JP7111598B2 - Optical Probes, Optical Displacement Gauges, and Surface Profilometers - Google Patents

Description

The present invention relates to optical probes, optical displacement meters, and surface profilometers.

For example, an optical displacement meter used in a measuring machine such as a surface profile measuring machine is known. The optical displacement meter scans a focused spot of measurement light along the surface to be measured. The optical displacement gauge measures the displacement of the surface to be measured based on the light intensity signal of the reflected light from the surface to be measured.
However, if the surface to be measured is light transmissive and the object to be measured is thin in the measurement direction, there is a possibility that reflected light from another reflecting surface that overlaps the surface to be measured will enter the optical displacement meter. In this case, the amount of light received by the optical displacement meter deviates from the amount of reflected light from the surface to be measured, resulting in a decrease in measurement accuracy.
Techniques for reducing the focal depth of the condensed spot are known in order to suppress such deterioration in measurement accuracy.
For example, Patent Literature 1 describes an optical displacement measuring instrument that uses the peripheral light component of the measurement beam by blocking the paraxial light component of the measurement beam. According to the technique described in Patent Document 1, the paraxial light component is blocked, so that the surface to be measured is irradiated with light having a large incident angle. As a result, even when the surface to be measured is light transmissive, it is easy to remove the influence of reflected light other than the surface to be measured.

Japanese Patent Application Laid-Open No. 2003-207323

However, the related art optical displacement meter and surface profilometer as described above have the following problems.
According to the technique described in Patent Document 1, the paraxial light component is blocked, so the light utilization efficiency of the light flux for measurement is lowered. In particular, when attempting to reduce the diameter of an optical probe used in an optical displacement meter, insufficient light intensity due to a decrease in light utilization efficiency tends to affect measurement accuracy.
Furthermore, in Patent Document 1, only the ambient light component is used, so when a single mode fiber is used as the light receiving section, the efficiency of coupling to the single mode fiber is significantly reduced.
As a result, according to the technique described in Patent Document 1, it is difficult to reduce the size and weight of the optical probe because a single fiber cannot be used as the light receiving portion of the optical probe used in the optical displacement meter.
For the purpose of shallowing the depth of focus of the measurement light flux, for example, shortening the focal length of the objective lens or increasing the numerical aperture (NA) of the objective lens may be considered. In this case, the diameter of the objective lens is increased, or the working distance of the objective lens is shortened. Depending on the shape of the object to be measured, the tip of the optical probe interferes with the surface to be measured when scanning the surface to be measured. As a result, the shape of the surface to be measured that can be measured is restricted.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems described above, and is capable of accurately measuring the displacement of a surface to be measured even for a thin, light-transmitting object to be measured, and at the same time improving the efficiency of light utilization. An object of the present invention is to provide an optical probe, an optical displacement meter, and a surface shape measuring instrument that are excellent in

In order to solve the above problems, the optical probe of the first aspect of the present invention includes a light emitting section for emitting light, and a first condensing optical element for condensing the light emitted from the light emitting section. a first beam converting element that converts the beam condensed by the first condensing optical element into a ring-shaped beam by bending the beam in a direction that intersects the optical axis; a second condensing optical element for irradiating a surface to be measured with light and condensing the reflected light from the surface to be measured; a second beam transforming element for transforming an ambient light component passing through the optical axis into a reduced diameter beam by moving it closer to the optical axis; a third focusing optical element for collecting the diameter reduced beam; a light receiving unit that receives the condensed diameter-reduced light flux.

In the above optical probe, the first beam conversion element may constitute the second beam conversion element, and the first condensing optical element may constitute the third condensing optical element.

In the optical probe, at least one of the first beam transforming element and the second beam transforming element may include a pair of conical lenses.

In the above optical probe, the first condensing optical element may form parallel light from the light.

In the above optical probe, the light receiving section may include an optical fiber into which the diameter-reduced light flux condensed by the third condensing optical element is incident.

The optical probe may further include a first light shielding section that shields an axial light beam in the light beam before being converted into the ring-shaped light beam.

The optical probe may further include a second light shielding section that shields light passing through the inner side of the ring-shaped light beam.

The optical probe may further include a third light shielding section that shields light passing outside the ring-shaped light beam.

The optical probe may further include a fourth light shielding section that shields light passing outside the light flux before being converted into the ring-shaped light flux.

An optical displacement meter according to a second aspect of the present invention includes the optical probe, a first moving section that relatively moves the optical probe with respect to the surface to be measured at least in the optical axis direction, and a light receiving section that receives light. a displacement measuring unit that measures the displacement of the surface to be measured in the optical axis direction based on the light intensity signal.

A surface profile measuring instrument according to a third aspect of the present invention comprises the above optical displacement gauge, and a second moving section that moves the optical displacement gauge relative to the holding section at least in a direction intersecting the optical axis. , provided.

INDUSTRIAL APPLICABILITY According to the optical probe, the optical displacement meter, and the surface shape measuring instrument of the present invention, it is possible to accurately measure the displacement of the surface to be measured even for a thin, light-transmitting object to be measured. Efficient.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the structural example of the optical probe of the 1st Embodiment of this invention, an optical displacement meter, and a surface profile measuring machine. FIG. 3 is a schematic diagram showing a configuration example of a measurement unit in the optical displacement meter of the first embodiment of the present invention; FIG. 4 is an explanatory diagram of the operation of the surface shape measuring instrument according to the first embodiment of the present invention; FIG. 5 is a schematic diagram showing a configuration example of an optical probe and an optical displacement gauge according to a second embodiment of the present invention; FIG. 5 is a schematic front view of a conical lens used in the optical probe according to the second embodiment of the present invention; FIG. 6 is a cross-sectional view taken along the line AA in FIG. 5; FIG. 10 is a schematic diagram illustrating the action of the first light shielding section used in the optical probe of the second embodiment of the present invention; FIG. 10 is a schematic diagram showing a configuration example of an optical probe and an optical displacement meter according to a third embodiment of the present invention; FIG. 10 is a schematic diagram showing a configuration example of an optical probe and an optical displacement meter according to a fourth embodiment of the present invention; FIG. 11 is a schematic diagram showing a configuration example of an optical probe and an optical displacement meter according to a fifth embodiment of the present invention;

Embodiments of the present invention are described below with reference to the accompanying drawings. In all the drawings, even when the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common explanations are omitted.

[First embodiment]
An optical probe, an optical displacement meter, and a surface shape measuring instrument according to a first embodiment of the present invention will be described.
FIG. 1 is a schematic diagram showing a configuration example of an optical probe, an optical displacement gauge, and a surface shape measuring instrument according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration example of a measurement unit in the optical displacement meter of the first embodiment of the invention.

As shown in FIG. 1, the surface shape measuring instrument 70 of this embodiment includes a stage 30, an optical displacement gauge 60A, and a control section 100. As shown in FIG.

The stage 30 includes a holding portion 31 and a moving portion 32 (second moving portion).
The holding part 31 holds the object to be measured. The configuration of the holding part 31 is not particularly limited as long as it can hold the object to be measured. For example, the holding section 31 may include a chuck mechanism, a suction mechanism, or the like for the purpose of holding the object to be measured.
The object to be measured by the surface shape measuring instrument 70 is not particularly limited as long as the surface to be measured can reflect the light emitted from the first optical system 60A. For example, examples of objects to be measured include optical elements, substrates for optical elements, molds, and the like.
Examples of optical elements include lenses, prisms, mirrors, and the like. The shape of the surface to be measured in the optical element is not particularly limited. For example, the surface to be measured in the optical element may be a concave surface, a convex surface, a flat surface, or the like.
Examples of substrates for optical elements include glass substrates and plastic substrates formed in the shape of optical elements.
Examples of molds include molds for optical elements and molds for molding parts other than optical elements.

An example in which the object to be measured is the lens 40 to be measured will be described below. The shape of the lens 40 to be measured is not particularly limited. In the example shown in FIG. 1, the lens 40 to be measured is a convex meniscus lens. The lens 40 to be measured has a first surface 40a and a second surface 40b. The first surface 40a is a concave surface. The second surface 40b is a convex surface arranged coaxially with the first surface 40a.
The lens thickness of the lens 40 to be measured is not particularly limited.
The surface to be measured of the lens 40 to be measured may be the first surface 40a or the second surface 40b. In the example shown in FIG. 1, the surface to be measured is the first surface 40a.
The lens 40 to be measured may be a glass lens or a plastic lens.

The moving part 32 movably supports the holding part 31 . The moving part 32 moves the holding part 31 at least in a direction intersecting an optical axis O of an optical displacement meter 60A, which will be described later. The moving part 32 may further move the holding part 31 in a direction along the optical axis O (hereinafter sometimes referred to as an optical axis direction). For example, the moving section 32 may include a goniometer stage, a rotating stage, an XY stage, and the like. The moving part 32 may further include a Z stage that moves in the optical axis direction.
The moving unit 32 is communicably connected to a control unit 100 to be described later, and the amount of movement is controlled by a control signal from the control unit 100 .
The moving part 32 relatively moves the surface to be measured held by the holding part 31 with respect to the optical axis O. As shown in FIG. More preferably, when the moving part 32 moves the surface to be measured, the surface to be measured is orthogonal to the optical axis O and maintains a state in which the point P on the optical axis O is passed through. Point P is the measurement reference position. For example, the point P is the imaging position of the measurement light flux at the movement neutral position of the optical probe 10A, which will be described later.

As a displacement measuring method in the optical displacement meter 60A, an appropriate displacement measuring method based on the reflected light intensity of the measurement light beam irradiated on the surface to be measured is used. For example, examples of displacement measurement methods suitable for the optical displacement meter 60A include a method using an interferometer (hereinafter referred to as an interferometer method) and a method using a coaxial confocal optical system (hereinafter referred to as a coaxial confocal method). .
The interferometric method uses an interferometer optical system having a reference surface. In the interferometer method, the reflected light flux of the measurement light flux on the reference surface and the reflected light flux of the measurement light flux on the surface to be measured are caused to interfere with each other. The interference light intensity changes according to the relative displacement in the optical axis direction between the surface to be measured and the interferometer optical system. A relative displacement is calculated from the amplitude and phase information of the interfering light intensity.
In the coaxial confocal method, the surface to be measured is irradiated with a measuring light beam through a coaxial confocal optical system. A light-receiving unit arranged at a confocal position receives the reflected light flux of the measurement light flux from the surface to be measured. The signal intensity of the reflected light flux at the light receiving section is maximized when the surface to be measured is arranged at the focal position. The relative displacement of the surface to be measured is calculated by relatively moving the coaxial confocal optical system and the surface to be measured in the optical axis direction and obtaining the amount of relative movement that maximizes the signal intensity.

The displacement measurement method of the optical displacement meter 60A may be an interferometer method or a coaxial confocal method, but an example of the interferometer method will be described below. In the optical displacement meter 60A, the configuration other than the interferometer optical system can also be used for the coaxial confocal method unless otherwise specified.
The optical displacement meter 60A includes an optical probe 10A, an optical probe moving section 7 (first moving section), and a measuring unit 20. As shown in FIG.

The optical probe 10A includes a housing 10a, a first optical fiber 1, a reference member 2, a first condensing lens 3 (first condensing optical element, third condensing optical element), a first conical lens 4 (first beam conversion element, second beam converting element), second conical lens 5 (first beam converting element, second beam converting element), and second condenser lens 6 (second condenser optical element).

The housing 10a is an elongated cylindrical member with a bottom. A tip portion 1b of a first optical fiber 1, which will be described later, is fixed to a first end portion E1 (end portion on the left side in the figure) in the longitudinal direction of the housing 10a. An opening 10b that opens in the longitudinal direction is formed at a second end E2 (the right end in the drawing) of the housing 10a in the longitudinal direction.
Inside the housing 10a, along the optical axis O, there are a tip portion 1b, a reference member 2, a first condenser lens 3, a first conical lens 4, a second conical lens 5, and a second condenser lens 6. arranged in this order. The optical axis O extends in the longitudinal direction of the housing 10a.
The tip portion 1b, the reference member 2, the first condenser lens 3, the first conical lens 4, the second conical lens 5, and the second condenser lens 6 are fixed to the housing 10a by a fixing member (not shown). .

The first optical fiber 1 is a single-mode fiber extending from a proximal end 1c (see FIG. 2) to a distal end 1b.
As shown in FIG. 2, the base end portion 1c is arranged inside a measurement unit 20, which will be described later.
As shown in FIG. 1, the tip portion 1b (light emitting portion, light receiving portion) is fixed coaxially with the optical axis O inside the first end portion E1 of the housing 10a. An optical fiber end surface 1a is formed at the tip portion 1b. The optical fiber end surface 1 a allows light to enter and exit the first optical fiber 1 .

The reference member 2 is made of a light-transmissive parallel plate with good surface precision. The reference member 2 is arranged close to the optical fiber end face 1 a of the first optical fiber 1 . However, a configuration is also possible in which the optical fiber end surface 1a also serves as a reference surface of the reference member 2, which will be described later. In this case, no reference member is arranged close to the optical fiber end face 1a.
In the reference member 2, a reference surface in an interferometer is formed on the surface near the optical fiber end surface 1a. For example, the reference plane is formed by the beam splitter plane.
The reference member 2 splits the incident light flux from the first optical fiber 1 into a transmitted light flux and a reflected light flux on the reference surface.

The first condenser lens 3 is composed of a single lens having positive refractive power or a group of lenses having positive refractive power as a whole. However, in the example shown in FIG. 1, the first condenser lens 3 is a single lens in which the first surface 3a and the second surface 3b face each other in the optical axis direction. The first surface 3 a is a lens surface facing the reference member 2 . The second surface 3b is a lens surface facing a first conical lens 4, which will be described later.
The first condenser lens 3 is arranged coaxially with the optical axis O. As shown in FIG. In this embodiment, the front focus of the first condenser lens 3 is aligned with the tip portion 1b. Thus, the first condenser lens 3 constitutes a collimator lens that converts the light emitted from the tip portion 1b into a parallel light beam.

The first conical lens 4 is a transmissive optical element in which a conical surface 4a and a flat surface 4b face each other in the optical axis direction. The first conical lens 4 is a rotationally symmetrical prism having a center line of rotation normal to a plane 4b passing through the vertex 4c of the conical surface 4a.
The plane 4 b of the first conical lens 4 faces the second surface 3 b of the first condenser lens 3 . The first conical lens 4 is arranged coaxially with the optical axis O.
The first conical lens 4 bends toward the optical axis O the optical path of the transmitted light incident on the flat surface 4b and transmitted through the conical surface 4a.

The second conical lens 5 is a transmissive optical element in which a conical surface 5a and a flat surface 5b face each other in the optical axis direction. The second conical lens 5 is composed of a rotationally symmetrical prism having a rotational center line normal to a plane 5b passing through the vertex 5c of the conical surface 5a.
The conical surface 5 a of the second conical lens 5 faces the conical surface 4 a of the first conical lens 4 . The second conical lens 5 is arranged coaxially with the optical axis O.
The second conical lens 5 bends toward the optical axis O the optical path of the transmitted light incident on the flat surface 5b and transmitted through the conical surface 5a.
In this embodiment, the apex angle of the conical surface 5 a is equal to the apex angle of the conical surface 4 a of the first conical lens 4 .

The second condenser lens 6 consists of a single lens with positive refractive power or a lens group with positive refractive power as a whole. However, in the example shown in FIG. 1, the second condenser lens 6 is a single lens in which the first surface 6a and the second surface 6b face each other in the optical axis direction. The first surface 6 a is a lens surface that faces the plane 5 b of the first conical lens 4 . The second surface 6b is a lens surface facing the opening 10b.
The second condenser lens 6 is arranged coaxially with the optical axis O. As shown in FIG.

The optical probe moving unit 7 supports the optical displacement meter 60A so as to be movable at least in the optical axis direction. By moving the optical displacement meter 60A in the optical axis direction, the optical probe moving unit 7 advances and retreats the condensing position of the measurement light flux emitted from the optical displacement meter 60A in the optical axis direction with high accuracy.
The configuration of the optical probe moving unit 7 is not particularly limited as long as the optical displacement meter 60A can be moved in the optical axis direction with accuracy corresponding to required measurement accuracy. For example, as the optical probe moving unit 7, a piezoelectric element driving mechanism or the like may be used.
The optical probe moving unit 7 is communicably connected to a control unit 100 to be described later, and the amount of movement is controlled by a control signal from the control unit 100 .

As shown in FIG. 2, the measurement unit 20 includes a light source 21, a coupling lens 22, a second optical fiber 23, an optical fiber coupler 24, a third optical fiber 25, a condenser lens 26, a light receiving element 27, and a displacement meter side portion 28. Prepare.

Light source 21 emits light used for displacement measurement. Since the optical displacement meter 60A uses an interferometer system, the light source 21 emits coherent light. A semiconductor laser, a gas laser, or the like may be used as the light source 21 . In this embodiment, a semiconductor laser is used as an example. In this case, the light emitted by the light source 21 is divergent light.

The coupling lens 22 optically couples light emitted from the light source 21 to a second optical fiber 23 which will be described later.
The coupling lens 22 is arranged at a position where the light emitting point of the light source 21 and the center of the core on the incident end surface 23a are optically conjugate with each other. The coupling lens 22 collects the light emitted by the light source 21 and forms an image on the incident end surface 23 a of the second optical fiber 23 .

The second optical fiber 23 transmits the light optically coupled by the coupling lens 22 to the first optical fiber 1 .
The second optical fiber 23 has a first end and a second end in the longitudinal direction. The first end of the second optical fiber 23 is formed with an incident end face 23a with an exposed core. A second end of the second optical fiber 23 is connected to a port of an optical fiber coupler 24, which will be described later. For example, the second optical fiber 23 consists of a single mode fiber.

The fiber optic coupler 24 has a first port 24a, a second port 24b and a third port 24c. The optical fiber coupler 24 outputs the light incident on the first port 24a to the second port 24b. The optical fiber coupler 24 outputs the light incident on the second port 24b to the third port 24c.
A second end of a second optical fiber 23 is optically connected to the first port 24a.
The base end portion 1c of the first optical fiber 1 is optically connected to the second port 24b.
A first end of a third optical fiber 25, which will be described later, is optically connected to the third port 24c.

The third optical fiber 25 transmits light emitted from the third port 24 c of the optical fiber coupler 24 .
The third optical fiber 25 has a first end and a second end in the longitudinal direction. A first end of the third optical fiber 25 is optically connected to a third port 24 c of the optical fiber coupler 24 . A second end of the third optical fiber 25 is formed with an emission end face 25a with an exposed core. For example, the third optical fiber 25 consists of a single mode fiber.

The condensing lens 26 condenses the light emitted from the emission end surface 25 a of the third optical fiber 25 .
The light-receiving element 27 is arranged at a light condensing position by the condensing lens 26 . The light receiving element 27 photoelectrically converts the light condensed by the condensing lens 26 . The light-receiving element 27 sends out a light intensity signal generated by photoelectric conversion to a displacement gauge side section 28, which will be described later.
As the light-receiving element 27, an appropriate photo-detecting element or photo-detector capable of photoelectric conversion of wavelength light generated by the light source 21 can be used.

The displacement meter side part 28 measures the displacement of the surface to be measured in the optical axis direction based on the light intensity signal sent from the light receiving element 27 . The displacement meter side unit 28 is communicably connected to a control unit 100, which will be described later, and drives the light source 21 and processes a light intensity signal from the light receiving element 27 based on a control signal from the control unit 100. .
The displacement measurement processing performed by the displacement meter side section 28 will be described together with the operation of the optical displacement meter 60A.

The control unit 100 shown in FIG. 1 controls the measurement operations of the surface shape measuring machine 70 and the optical displacement meter 60A. The control unit 100 includes an operation unit 100a through which a user performs an operation input. For example, the operation unit 100a has appropriate operation input means such as a keyboard, operation buttons, operation levers, operation panel, and operation switches.
The control unit 100 is communicably connected to the stage 30, the optical probe moving unit 7, and the displacement meter side unit 28 (see FIG. 2). The control unit 100 controls each device part of the surface shape measuring machine 70 based on the operation input through the operation unit 100a.
For example, the control unit 100 sends a control signal to at least one of the optical probe moving unit 7 and the stage 30 to adjust the relative position between the optical displacement meter 60A and the object to be measured held by the holding unit 31. control. In this embodiment, design shape data of the surface to be measured is stored in the control unit 100 before shape measurement. The control unit 100 can move a point on the surface to be measured to, for example, the measurement reference position P based on the stored designed shape data.
For example, the control section 100 controls the start and stop of shape measurement by the optical displacement gauge 60A by sending a control signal to the displacement gauge side section 28 .
Specific control performed by the control unit 100 will be described together with the operations of the surface shape measuring machine 70 and the optical displacement meter 60A.

As the device configuration of the displacement gauge side section 28 and the control section 100, for example, a computer including a CPU, a memory, an input/output interface, an external storage device, and the like may be used. In this case, the computer executes a suitable control program that generates control signals corresponding to the operations described below. The control program may be stored in the aforementioned memory or external storage device. The control program may be loaded into memory by reading from a storage medium. The control program may be loaded into memory through a communication line.
Appropriate hardware for executing respective operations may be used as the device configuration of the displacement meter side unit 28 and the control unit 100, or a combination of appropriate hardware and a computer may be used. .
The displacement meter side part 28 and the control part 100 may be configured separately from each other, or may be integrated.

Next, an example of the operation of the surface shape measuring machine 70 will be described, centering on an example of the operation of the optical probe 10A and the optical displacement meter 60A.
FIG. 3 is an explanatory diagram of the operation of the surface profile measuring instrument according to the first embodiment of the present invention.

As shown in FIG. 1, in the surface shape measuring instrument 70, the stage 30 is positioned to face the second end E2 of the optical displacement meter 60A.
For example, when measuring the surface shape of the first surface 40a of the lens 40 to be measured, as shown in FIG. Let
When an operation input for starting shape measurement is performed from the operation unit 100a, the control unit 100 calculates the scanning path of the measurement light beam for surface shape measurement based on the pre-stored shape data of the first surface 40a.
Thereafter, the control section 100 sends a control signal for initializing the relative positions of the optical probe 10A and the lens 40 to be measured to the optical probe moving section 7 and the stage 30 . Thereby, the optical probe moving section 7 moves the optical probe 10A to the movement neutral position. The moving part 32 of the stage 30 moves the starting point of the scanning path on the first surface 40a to the measurement reference position P based on the designed shape data of the first surface 40a. At this time, the moving part 32 rotates the holding part 31 for the purpose of aligning the normal line of the first surface 40a at the measurement reference position P with the optical axis O. As shown in FIG.
This completes the initialization of the arrangement of the optical probe 10A and the lens 40 to be measured.

After that, the control unit 100 sends a control signal to the displacement meter side unit 28 to start displacement measurement.
The displacement meter side part 28 lights the light source 21 . As shown in FIG. 2, the light source 21 emits a luminous flux L0. The light flux L0 is condensed on the incident end surface 23a by the coupling lens 22. As shown in FIG. The light flux L0 is optically coupled to the second optical fiber 23 . The light beam L0 travels through the core of the second optical fiber 23 toward the first port 24a, as indicated by the solid arrow in FIG. Upon reaching the end of the second optical fiber 23 , the light beam L 0 enters the first port 24 a of the optical fiber coupler 24 . The light flux L0 travels through the optical fiber coupler 24 towards the second port 24b. The light flux L0 is emitted from the second port 24b of the optical fiber coupler 24. FIG. As a result, the light flux L0 is incident on the base end portion 1c of the first optical fiber 1. As shown in FIG.

As shown in FIG. 1, the luminous flux L0 is emitted toward the reference member 2 when it reaches the optical fiber end face 1a of the first optical fiber 1. As shown in FIG.
The luminous flux L0 is split at the reference surface of the reference member 2 into a reflected luminous flux L0r and an emitted luminous flux L1.
The reflected light beam L0r enters the optical fiber end face 1a of the first optical fiber 1 and travels through the first optical fiber 1 toward the optical fiber coupler 24 .
The emitted light flux L1 is emitted from the reference member 2 toward the first condenser lens 3 . The emitted light flux L1 diverges from the optical fiber end surface 1a with the optical axis O as the center.

As shown in FIG. 2, the reflected light flux L0r enters the third optical fiber 25 through the third port 24c after entering the second port 24b. The reflected light beam L0r travels through the third optical fiber 25 toward the output end surface 25a. The reflected light flux L0r is condensed on the light receiving element 27 by the condensing lens 26 after being emitted from the emission end face 25a.

As shown in FIG. 1 , the emitted light flux L1 is condensed by the first condensing lens 3 when incident on the first condensing lens 3 . In this embodiment, the front focal point of the first condenser lens 3 coincides with the optical fiber end face 1a, so the emitted light flux L1 is converted by the first condenser lens 3 into a parallel light flux L2.
The parallel light beam L2 travels along the optical axis O. When the parallel light flux L2 is incident on the plane 4b of the first conical lens 4, it travels along the optical axis O and reaches the conical surface 4a.

The conical surface 4a functions as a rotationally symmetrical prism. The collimated light beam L2 is uniformly refracted toward the optical axis O at the conical surface 4a, except for axial rays passing through the vertex 4c.
An on-axis ray, in principle, travels straight along the optical axis O. However, depending on the finished shape of the vertex 4c, the light may be refracted, scattered, or condensed according to the finished shape. The same is true for rays in the vicinity of the on-axis ray. However, in the parallel light flux L2, the light quantity of the axial ray component is much smaller than that of the other components.

When the parallel beam L2 is uniformly refracted toward the optical axis O, a bent beam L3 crossing the optical axis O is formed. As the bent light beam L3 progresses toward the second end E2, the peripheral light component of the parallel light beam L2 and the central light component of the parallel light beam L2 are gradually replaced.
After the outermost marginal ray in the collimated beam L2 crosses the optical axis O, the refracted beam L3 moves away from the optical axis O as it progresses toward the second end E2. In this specification, such a state in which the cross section perpendicular to the optical axis O is annular is referred to as a ring-shaped light flux L4. Hereinafter, regarding the cross section of the luminous flux, the cross section orthogonal to the optical axis O is simply referred to as the "cross section" unless otherwise specified.
The inner peripheral light component of the ring-shaped light flux L4 consists of the central light component of the parallel light flux L2. The peripheral light component of the ring-shaped light beam L4 consists of the peripheral light component of the parallel light beam L2. The light intensity distribution from the inner circumference to the outer circumference in the cross section of the ring-shaped light beam L4 corresponds to the light intensity distribution from the periphery to the center in the cross section of the parallel light beam L2.

When the ring-shaped light flux L4 reaches the conical surface 5a of the second conical lens 5, it is uniformly refracted toward the optical axis O at the conical surface 5a. In this embodiment, the apex angles of the conical surfaces 4a and 5a are equal to each other, and the first conical lens 4 and the second conical lens 5 are arranged coaxially. As a result, the ring-shaped luminous flux L4 is converted into a cylindrical parallel luminous flux coaxial with the optical axis O. FIG.
When the ring-shaped luminous flux L4 transmitted through the plane 5b is incident on the second condenser lens 6, the ring-shaped luminous flux L4 is condensed and converted into a ring-shaped condensed luminous flux L5. In this embodiment, the ring-shaped condensed light beam L5 is imaged at the rear focal position of the second condensing lens 6 . In this embodiment, the back focal position of the second condenser lens 6 matches the measurement reference position P in the initialized state.

Since the ring-shaped condensed light flux L5 is condensed toward the rear focal position, the outer peripheral light and the inner peripheral light of the ring-shaped condensed light flux L5 gradually approach each other, forming a minute spot on the optical axis O. .
When the ring-shaped condensed light flux L5 reaches the first surface 40a, part of the ring-shaped condensed light flux L5 is reflected toward the object side according to the reflectance of the first surface 40a, and the other part of the ring-shaped condensed light flux L5 passes through the first surface 40a.
For example, part of the light flux L5a in the ring-shaped condensed light flux L5 is reflected as the light flux L6a. The normal line of the first surface 40a is aligned with the optical axis O due to the initialization operation described above. As a result, the luminous flux L6a is a symmetrical luminous flux with respect to the optical axis O with respect to the luminous flux L5a. Similarly, part of the other light flux components of the ring-shaped condensed light flux L5 is similarly reflected by the first surface 40a. As a result, the first surface 40a forms a reflected light flux L6 that has the same shape as the ring-shaped condensed light flux L5 and follows the same optical path as the ring-shaped condensed light flux L5 toward the second condensing lens 6. The reflected light flux L6 has a light intensity distribution similar to that of the ring-shaped condensed light flux L5, although the total amount of light is smaller than that of the ring-shaped converged light flux L5. The reflected light beam L6 as a whole travels backward along the optical path of the ring-shaped condensed light beam L5.

The reflected light beam L6 is incident on the peripheral portion of the second condenser lens 6 . The reflected light beam L6 is condensed by the second condensing lens 6 and travels along the optical axis O. As shown in FIG.
The reflected light flux L6 passes through the second conical lens 5 and the first conical lens 4 in this order, and is converted into a diameter-reduced light flux L7. The diameter-reduced light flux L7 is formed by traveling backward along the optical paths of the ring-shaped light flux L4 and the bent light flux L3. The diameter-reduced light flux L7 is a parallel light flux formed by shifting the reflected light flux L6 passing through the peripheral portion of the second condenser lens 6 to the vicinity of the optical axis O. FIG. As a result, the outer diameter of the diameter-reduced light flux L7 is smaller than the outer diameter of the reflected light flux L6 passing through the second condenser lens 6 .
Since the diameter-reduced light flux L7 travels backward along the same optical paths as the parallel light flux L2 and the emitted light flux L1, the optical coupling efficiency at the optical fiber end surface 1a is improved. Thereby, the light amount of the reflected light flux L6 can be measured with high accuracy.

On the other hand, the other component of the light beam L5a transmitted through the first surface 40a is refracted according to the refractive power of the first surface 40a and then reflected as the light beam L6b by the second surface 40b.
The luminous flux L6b is optically coupled to the first optical fiber 1 in the same manner as the reflected luminous flux L6 when the luminous flux L6b travels backward along the optical path of the ring-shaped condensed luminous flux L5. When the light flux L6b is optically coupled to the first optical fiber 1, it becomes noise light for displacement measurement, which will be described later.
The ring-shaped condensed light beam L5 obliquely enters the first surface 40a and forms an image on the first surface 40a. After that, a light beam L6b is formed by being partially reflected by the second surface 40b.
Except for a very special case in which the radius of curvature of the second surface 40b matches the lens thickness of the lens 40 to be measured, the entire light beam L6b does not return to the imaging position of the ring-shaped condensed light beam L5.
When the object to be measured is a thin lens, if the angle of incidence on the second surface 40b is shallow, part of the light flux L6b may return to the optical fiber end surface 1a.
However, in the present embodiment, the ring-shaped condensed light flux L5 does not include paraxial light with respect to the optical axis O, so even the light flux component with the shallowest incident angle is the ring-shaped converged light flux L4 and the ring-shaped converged light flux L5. is the inner peripheral component of Therefore, according to this embodiment, by appropriately setting the inner diameter of the ring-shaped light beam L4 and the numerical aperture of the second condenser lens 6, the light beam L6b travels backward along the optical path and forms an image on the optical fiber end surface 1a. can be prevented.
Furthermore, in this embodiment, even if the light beam L6b returns to the optical fiber end face 1a, the inner peripheral component of the ring-shaped light beam L4 is the peripheral light component of the emitted light beam L1. The peripheral light component of the emitted light flux L1 has a lower light intensity than the central light component. As a result, even if the light flux L6b should return to the optical fiber end face 1a, noise will be lower than in the case where the central light component returns.

The diameter-reduced light beam L7 optically coupled to the first optical fiber 1 at the optical fiber end face 1a travels along the same optical path as the reflected light beam L0r and is received by the light receiving element 27. FIG. However, the reflected light flux L0r and the diameter-reduced light flux L7 interfere with each other according to the mutual optical path length difference. Here, the optical path length of the diameter-reduced light flux L7 is defined as the length of the emitted light flux L1 emitted from the reference surface, the parallel light flux L2, the bent light flux L3, the ring-shaped light flux L4, the ring-shaped converged light flux L5, the reflected light flux L6, and the contracted light flux L6. It means the total optical path length after being sequentially converted into the diameter luminous flux L7 and returning to the reference surface. Specifically, it corresponds to twice the optical path length from the reference member 2 to the optical fiber end surface 1a.
The light receiving element 27 sends an interference signal corresponding to the light intensity of the interference light to the displacement meter side section 28 .

Next, the displacement measurement operation will be described.
In displacement measurement by the optical displacement meter 60A, an interference signal is obtained while driving the optical probe 10A in the optical axis direction at each measurement position on the scanning path on the first surface 40a.
When the optical probe 10A is moved in the optical axis direction by the optical probe moving part 7, the focus position of the ring-shaped condensed light flux L5 is moved in the optical axis direction. When the focus position deviates from the first surface 40a arranged at the measurement reference position P, the first surface 40a is irradiated with the defocused ring-shaped condensed light flux L5.
In such a defocused state, the component of the reflected light flux L6 that can travel backward along the optical path of the ring-shaped condensed light flux L5 decreases. Among the reflected light beams L6, the amount of light that travels backward along the optical path of the ring-shaped condensed light beam L5 and returns to the optical fiber end surface 1a is maximized because the focus position of the ring-shaped converged light beam L5 coincides with the first surface 40a. It is time.
After passing through the reference surface of the reference member 2, the diameter-reduced light beam L7, which is optically coupled to the first optical fiber 1 and reaches the light source 21, interferes with the reflected light beam L0r in accordance with the optical path length difference. The amount of light received by the light receiving element 27 is the sum of the light amount of the reflected light flux L6 incident on the first optical fiber 1 and the light amount change due to interference.

An interference signal generated by photoelectric conversion by the light receiving element 27 is sent to the displacement meter side part 28 . In the displacement meter side part 28, from the movement position of the optical probe 10A based on the driving amount of the optical probe moving part 7 and the interference signal, the movement position where the focus position of the ring-shaped condensed light beam L5 coincides with the first surface 40a is determined. calculate. As a specific processing, for example, arithmetic processing by the phase shift method can be mentioned.
According to the phase shift method, the information of the movement position at which the peak intensity excluding the signal change due to the interference is obtained is calculated by arithmetic processing of the interference signals at a plurality of positions in the optical axis direction.
However, if noise light such as the light flux L6b from the second surface 40b is mixed in the reflected light flux L6, an error occurs in the determination of the peak intensity. For example, the light beam L6b has a different optical path length than the reflected light beam L6, and thus causes noise in the interference signal. Disturbances in the interfering signal reduce the accuracy of the phase shift method.
For example, even if the light amount of the reflected light flux L6 optically coupled in the first optical fiber 1 decreases or varies, an error occurs in determining the peak intensity. For example, when the light amount of the reflected light beam L6 optically coupled to the first optical fiber 1 decreases, the S/N ratio of the interference signal decreases, resulting in a decrease in measurement accuracy. For example, when the light amount of the reflected light beam L6 optically coupled to the first optical fiber 1 varies, the position of the peak intensity changes.
In the present embodiment, as described above, noise light is suppressed from being mixed into the reflected light flux L6, and the optical coupling efficiency in the first optical fiber 1 is excellent, so it is possible to determine the peak intensity with high accuracy.
The displacement meter side part 28 stores the information of the movement position where the focus position of the ring-shaped condensed light beam L5 coincides with the first surface 40a as the displacement amount of the first surface 40a at the measurement position.

When the position of the first surface 40a at one measurement position is obtained in this way, the control unit 100 sends a control signal to the stage 30 to set the next measurement position on the scanning path to the measurement reference position P move to For example, when the first surface 40a is a spherical surface, the moving part 32 rotates the holding part 31 around the point P as shown in FIG.
This measurement position is a designed measurement position on the first surface 40 a stored in the control unit 100 . The actual first surface 40a may deviate from the measurement reference position P due to manufacturing errors or the like.
After the measurement position is moved, the control unit 100 performs control to perform the displacement measurement operation described above.
After the measurement at all measurement positions on the planned scanning path is completed, the displacement meter side section 28 converts each displacement amount into a displacement from an arbitrary reference position. For example, assuming that the displacement at the intersection of the first surface 40a and the lens optical axis of the lens 40 to be measured is 0, the displacement at each measurement position is converted. Each converted amount of displacement represents the amount of deviation from the design value of the first surface 40a. Thus, the shape measurement of the first surface 40a is completed.

According to the optical probe 10A of the present embodiment, the first surface 40a is irradiated with the ring-shaped condensed light beam L5 passing through the peripheral portion of the second condenser lens 6. Paraxial light with shallow angles is eliminated. Therefore, even if the lens 40 to be measured is thin, it is possible to prevent the reflected light (light beam L6b) from returning to the first optical fiber 1 from the second surface 40b. As a result, it is possible to suppress the light reflected by the first surface 40a, such as the light beam L6a, from being mixed into the reflected light beam L6 reflected by the surface to be measured as noise light, so that highly accurate displacement measurement can be performed.

Further, in the present embodiment, a parallel light flux L2 is formed from the total light flux of the emitted light flux L1, and a ring-shaped light flux L4 is formed from the parallel light flux L2 by the first conical lens 4 and the second conical lens 5. The ring-shaped luminous flux L4 is condensed by the second conical lens 5, so that the first surface 40a is irradiated with the entire luminous flux of the ring-shaped luminous flux L4 as a condensed ring-shaped luminous flux L5.
As described above, in the present embodiment, all of the central light component and the peripheral light component of the emitted light flux L1 are obliquely incident on the first surface 40a by passing through the peripheral portion of the second condenser lens 6. FIG. For this reason, for example, the light utilization efficiency is improved compared to the case where the central portion of the parallel light flux L2 is shielded to form the measurement light flux that passes through the peripheral portion of the second condenser lens 6. FIG.

Furthermore, in this embodiment, since the ring-shaped luminous flux L4 is condensed by the peripheral portion of the second condensing lens 6, as described above, compared to the case where the entire luminous flux is transmitted through the second condensing lens 6, the image is formed. Aberrations in position are reduced. As a result, if the numerical aperture is the same, the depth of focus of the optical system of this embodiment is shallower than that of the optical system through which the entire luminous flux is transmitted. Therefore, displacement measurement with higher accuracy becomes possible. In order to obtain the same depth of focus in an optical system through which the entire luminous flux is transmitted, the numerical aperture must be increased by, for example, increasing the lens diameter. .
If the outer diameter of the optical probe 10A can be reduced, it becomes easier to measure a mold surface having a complicated shape, a small lens having a concave surface with a small radius of curvature as shown in FIG.

As described above, according to the optical probe 10A, the optical displacement meter 60A, and the surface shape measuring instrument 70 of the present embodiment, even a thin, light-transmitting object to be measured can be accurately displaced on the surface to be measured. can be measured, and the light utilization efficiency is excellent.

[Second embodiment]
An optical probe and an optical displacement meter according to a second embodiment of the present invention will be described.
FIG. 4 is a schematic diagram showing a configuration example of an optical probe and an optical displacement gauge according to a second embodiment of the present invention. FIG. 5 is a schematic front view of a conical lens used in the optical probe according to the second embodiment of the invention. FIG. 6 is a cross-sectional view along line AA in FIG. 7A and 7B are schematic diagrams for explaining the action of the first light shielding part used in the optical probe of the second embodiment of the present invention. FIG.

As shown in FIG. 4, an optical displacement meter 60B of this embodiment includes an optical probe 10B instead of the optical probe 10A of the optical displacement meter 60A of the first embodiment. The optical displacement gauge 60B can be used in place of the optical displacement gauge 60A in the surface shape measuring instrument 70 of the first embodiment.
The following description will focus on the differences from the first embodiment.

The optical probe 10B is configured in the same manner as the optical probe 10A except that a light shielding portion 41 (first light shielding portion) and a light shielding portion 42 (second light shielding portion) are added.
The light shielding part 41 shields the axial light flux in the light flux before being converted into the ring-shaped light flux L4. The transmittance of the light shielding portion 41 can be appropriately set in consideration of the influence of transmitted light on displacement measurement.
As shown in FIGS. 5 and 6, the light blocking portion 41 is provided on the conical surface 4a of the first conical lens 4 at and near the vertex 4c. The planar view shape of the light shielding portion 41 is a circle centered on the vertex 4c.
The outer diameter D41 of the light shielding portion 41 may be any size as long as it can cover the conical range in which manufacturing errors are likely to occur in the vicinity of the vertex 4c. However, in FIG. 4, the size of the light shielding portion 41 is exaggerated for the sake of visibility, and illustration of the light shielding region is omitted.

The configuration of the light blocking portion 41 is not particularly limited as long as it can block the axial light flux. For example, the light-shielding portion 41 may be formed of a cured light-shielding paint containing a light-absorbing material. For example, the light shielding portion 41 may be formed by depositing a light absorbing material on the conical surface 4a.
The light shielding part 41 may attenuate the axial light flux by light scattering. Specifically, the light shielding portion 41 may be formed by roughening the vicinity of the vertex 4c. For example, the light shielding part 41 may be formed by a light scattering layer covering the vertex 4c.

The light blocking portion 42 blocks light passing through the inside of the ring-shaped light beam L4. The transmittance of the light shielding portion 42 can be appropriately set in consideration of the influence of displacement measurement of transmitted light. For example, the transmittance of the light shielding portion 42 may be the same as the transmittance of the light shielding portion 41 .
As shown in FIGS. 5 and 6, the light blocking portion 42 is provided on the conical surface 5a of the second conical lens 5 at and near the vertex 5c. The planar view shape of the light shielding portion 42 is a circle centered on the vertex 5c.
The outer diameter D42 of the light shielding portion 42 is not particularly limited as long as it is equal to or smaller than the inner diameter of the ring-shaped light flux L4.
As for the configuration of the light shielding portion 42, the configuration illustrated in the description of the light shielding portion 41 may be used.

The optical probe 10B is the same as the optical probe of the first embodiment, except that the light blocking portion 41 blocks the axial light component of the parallel light beam L2, and the light blocking portion 42 blocks the light passing through the inner side of the ring-shaped light beam L4. It has the same action as 10A.
The operation of the optical probe 10B will be described below, focusing on the differences from the first embodiment.

When the first conical lens 4 is made of glass or plastic, it is difficult to converge the conical surface 4a precisely to one point. The vertex 4c is formed by a finite end face that is larger than the wavelength of the parallel light flux L2. As a result, the axial luminous flux incident near the vertex 4c is emitted in a direction different from the refraction direction by the conical surface 4a.
For example, as shown in FIG. 7, when the axial light flux L2a incident on the first conical lens 4 travels straight at the vertex 4c like the light flux L3a, when it reaches the second surface 40b (see FIG. 4), the second surface Return light is specularly reflected at 40b and has an optical path length different from that of the reflected light flux L6.
For example, depending on the shape of the vicinity of the vertex 4c, the axial light beam L2a, like the light beam L3b, may be transmitted in a direction different from the optical axis O and the bent light beam L3. In this case, the light flux L3b is incident on the second surface 40b at a shallow angle of incidence, so it is likely to become return light that is optically coupled to the optical fiber end surface 1a.
However, in the present embodiment, since the on-axis light beam L2a is blocked by the light blocking portion 41, the light beams L3a and L3b are not generated or can be suppressed to a level that does not affect the displacement measurement even if they are generated.

The light blocking portion 42 can block light passing through the inner side of the ring-shaped light flux L4 on the conical surface 5a. As a result, the noise light that passes through the light shielding portion 42 and is optically coupled to the optical fiber end surface 1a is shielded.
For example, even if luminous fluxes such as the luminous fluxes L3a and L3b are generated to pass through the light shielding portion 41, the light components passing through the inner side of the ring-shaped luminous flux L4 are shielded by the light shielding portion .
For example, the light shielding portion 42 shields the light component of the reflected light from the second surface 40b that passes through the inner side of the ring-shaped light beam L4 and is optically coupled to the optical fiber end surface 1a.
Furthermore, even if flare light is generated by reflected light from an optical element in the optical probe 10B, the light shielding portion 42 blocks the light component of the flare light that passes through the position of the light shielding portion 42 and is optically coupled to the optical fiber end surface 1a. Can be shaded.

As described above, according to the present embodiment, the light shielding portions 41 and 42 can suppress the generation of noise light more than the first embodiment, so that more accurate displacement measurement is possible.

Furthermore, in this embodiment, the manufacturing cost of the first conical lens 4 and the second conical lens 5 can be reduced.
For example, in the first conical lens 4, if the conical surface 4a is formed with high accuracy up to the vicinity of the vertex 4c, the manufacturing cost of the first conical lens 4 increases. However, in the present embodiment, since the vicinity of the vertex 4c is shielded by the light shielding portion 41, the conical surface 4a may not be formed in the portion covered by the light shielding portion 41. FIG. For example, the shape of the portion covered with the light shielding portion 41 may be a plane that intersects the lens optical axis, a convex surface that is different from a cone, or the like. As a result, the manufacturing cost of the first conical lens 4 is reduced.
The second conical lens 5 is also similar to the first conical lens 4 .

As described above, according to the optical probe 10B and the optical displacement meter 60B of the present embodiment, as in the first embodiment, even if the object to be measured is light-transmissive and thin, the surface to be measured can be accurately measured. Displacement can be measured, and light utilization efficiency is excellent.

[Third embodiment]
An optical probe and an optical displacement meter according to a third embodiment of the present invention will be described.
FIG. 8 is a schematic diagram showing a configuration example of an optical probe and an optical displacement gauge according to a third embodiment of the present invention.

As shown in FIG. 8, an optical displacement meter 60C of this embodiment includes an optical probe 10C instead of the optical probe 10A of the optical displacement meter 60A of the first embodiment. The optical displacement gauge 60C can be used in place of the optical displacement gauge 60A in the surface shape measuring instrument 70 of the first embodiment.
The following description will focus on the differences from the first embodiment.

The optical probe 10C is configured in the same manner as the optical probe 10A except that a light shielding portion 43 (fourth light shielding portion) and a light shielding portion 44 (third light shielding portion) are added.
The light shielding part 43 shields the light passing through the outside of the light flux before being converted into the ring-shaped light flux L4. The transmittance of the light shielding portion 43 can be appropriately set in consideration of the influence of transmitted light on displacement measurement. For example, the transmittance of the light shielding portion 43 may be the same magnitude as the transmittance of the light shielding portion 41 in the second embodiment.
The configuration of the light blocking portion 43 is not particularly limited as long as it can block light passing through the outside of the light flux before being converted into the ring-shaped light flux L4. In the example shown in FIG. 8, the light shielding part 43 is formed of a light shielding plate through which an opening 43a having an inner diameter equal to or larger than the outer diameter of the bent light beam L3 penetrates in the thickness direction. For example, the light-shielding portion 43 may include a metal plate, a plastic plate, or the like coated with a light-shielding paint containing a light-absorbing material. For example, the light shielding portion 43 may include a black-plated metal plate or plastic plate that has been matted.
The light shielding part 43 is fixed inside the housing 10a by a fixing member (not shown). The light blocking portion 43 is fixed at a position where the bent light beam L3 passes through the inside of the opening portion 43a.

The light blocking portion 44 blocks light passing outside the ring-shaped light flux L4. The transmittance of the light shielding portion 44 can be appropriately set in consideration of the influence of displacement measurement of transmitted light. For example, the transmittance of the light shielding portion 44 may be the same as the transmittance of the light shielding portion 43 .
The configuration of the light blocking portion 44 is not particularly limited as long as it can block light passing through the outside of the ring-shaped light flux L4. In the example shown in FIG. 8, the light shielding portion 44 is formed of a light shielding plate through which an opening 44a having an inner diameter equal to or larger than the outer diameter of the ring-shaped light flux L4 penetrates in the thickness direction. The light shielding portion 44 may be formed in the same manner as the light shielding portion 43 except for the size of the opening 44a.
The light shielding part 44 is fixed inside the housing 10a by a fixing member (not shown). The light blocking portion 44 is fixed at a position between the first conical lens 4 and the second conical lens 5 so that the ring-shaped light flux L4 passes through the inner side of the opening 44a.

In the optical probe 10C, light passing outside the luminous flux before being converted into the ring-shaped luminous flux L4 is blocked by the light blocking part 43, and light passing outside the ring-shaped luminous flux L4 is blocked by the light blocking part 44. It has the same action as the optical probe 10A of the first embodiment.
The operation of the optical probe 10C will be described below, focusing on the differences from the first embodiment.

According to this embodiment, the light shielding portion 43 shields the light passing outside the bent light flux L3. As a result, the noise light that passes through the light shielding portion 43 and is optically coupled to the optical fiber end face 1a is shielded.
Further, according to the present embodiment, the light shielding portion 44 shields the light passing outside the ring-shaped light flux L4. As a result, the noise light that passes through the light shielding portion 44 and is optically coupled to the optical fiber end surface 1a is shielded.
Furthermore, according to the light shielding portions 43 and 44, even if flare light is generated by the reflected light of the optical element in the optical probe 10B, the flare light component passing through the positions of the light shielding portions 43 and 44 can be shielded, so that the noise light can be suppressed. can be reduced.

As described above, according to the present embodiment, the light shielding portions 43 and 44 can suppress the generation of noise light more than the first embodiment, so that more accurate displacement measurement is possible.

As described above, according to the optical probe 10C and the optical displacement meter 60C of the present embodiment, as in the first embodiment, even if the object to be measured is light-transmissive and thin, the surface to be measured can be accurately measured. Displacement can be measured, and light utilization efficiency is excellent.

[Fourth embodiment]
An optical probe and an optical displacement meter according to a fourth embodiment of the present invention will be described.
FIG. 9 is a schematic diagram showing a configuration example of an optical probe and an optical displacement gauge according to a fourth embodiment of the present invention.

As shown in FIG. 9, an optical displacement meter 60D of this embodiment includes an optical probe 10D instead of the optical probe 10A of the optical displacement meter 60A of the first embodiment. The optical displacement gauge 60D can be used in place of the optical displacement gauge 60A in the surface shape measuring instrument 70 of the first embodiment.
The following description will focus on the differences from the first embodiment.

The optical probe 10C is the same as the optical probe 10A except that the same light shielding parts 41 and 42 as in the second embodiment and the light shielding parts 43 and 44 as in the third embodiment are added. Configured.

According to the present embodiment, since the light blocking portions 41 to 44 are provided, the same effects as those of the second and third embodiments are provided in addition to the effects similar to those of the first embodiment.
As described above, according to the present embodiment, the light shielding portions 41 to 44 can suppress the generation of noise light more than the first embodiment, so that more accurate displacement measurement is possible.

[Fifth embodiment]
An optical probe and an optical displacement meter according to a fifth embodiment of the present invention will be described.
FIG. 10 is a schematic diagram showing a configuration example of an optical probe and an optical displacement gauge according to a fifth embodiment of the present invention.

As shown in FIG. 10, an optical displacement gauge 60E of this embodiment includes an optical probe 10E instead of the optical probe 10B of the optical displacement gauge 60B of the second embodiment. The optical displacement gauge 60E can be used in place of the optical displacement gauge 60A in the surface shape measuring instrument 70 of the first embodiment.
In the following, the points different from the second embodiment will be mainly described.

The optical probe 10E further includes light shielding portions 45, 46 and 47 (first light shielding portions) and light shielding portions 48, 49 and 50 (second light shielding portions) in addition to the light shielding portions 41 and 42 in the second embodiment. Prepare.

The light shielding portions 45, 46, and 47, similarly to the light shielding portion 41, shield the axial light flux before being converted into the ring-shaped light flux L4. However, the light blocking portion 45 is provided on the optical axis O on the first surface 3 a of the first condenser lens 3 . The light blocking portion 46 is provided on the optical axis O on the second surface 3 b of the first condenser lens 3 . The light blocking portion 47 is provided on the optical axis O on the plane 4 b of the first conical lens 4 .
The sizes of the light shielding portions 45 to 47 when viewed in the optical axis direction are equal to or smaller than the size corresponding to the light shielding area of the light shielding portion 41 on the respective optical paths. For example, in the case of this embodiment, the size of the light shielding portions 46 and 47 is equal to or smaller than the size of the light shielding portion 41 . The light shielding portion 45 is slightly smaller than the light shielding portion 41 .
In this embodiment, since the axial light flux can be blocked by the light shielding portions 41 and 45 to 47, the transmittance of the light shielding portions 41 and 45 to 47 affects the displacement measurement of the transmitted light as a whole. is sufficient as long as the transmittance can be suppressed. For example, when the transmittance required as a whole is T1 and the light shielding portions 45 to 47 have a light shielding region corresponding to the light shielding portion 41, the product of the respective transmittances of the light shielding portions 41 and 45 to 47 is equal to T1. It may be.

The light blocking portions 48, 49, and 50 block light passing through the inner side of the ring-shaped luminous flux L4, similarly to the light blocking portion . However, the light blocking portion 48 is provided on the optical axis O on the plane 5 b of the second conical lens 5 . The light blocking portion 49 is provided on the optical axis O on the first surface 6 a of the second condenser lens 6 . The light shielding part 50 is provided on the optical axis O on the second surface 6 b of the second condenser lens 6 .
The size of the light blocking portions 48 to 50 as seen from the optical axis direction is equal to or less than the inner diameter of the ring-shaped light beam L4 on each optical path.
In this embodiment, since the light passing through the inside of the ring-shaped luminous flux L4 can be blocked by the light blocking portions 42, 48 to 50, the transmittance of the light blocking portions 42, 48 to 50 is the same as that of the light blocking portions 42, 48 to 50 as a whole. Any transmittance may be used as long as it can suppress the influence of light on displacement measurement. For example, when the transmittance required as a whole is T2 and the light shielding portions 48 to 50 have a light shielding region corresponding to the light shielding portion 42, the product of the respective transmittances of the light shielding portions 42 and 48 to 50 is T2. It may be.

According to the present embodiment, since the light blocking portions 45 to 47 are provided in addition to the light blocking portion 41, transmission of the on-axis light beam can be suppressed more reliably than in the second embodiment. Furthermore, specularly reflected light from the first surface 3a and the second surface 3b of the first condenser lens 3 and specularly reflected light from the plane 4b of the first conical lens 4 can be suppressed. As a result, it is possible to prevent specularly reflected light of the axial light beam from the first condenser lens 3 and the first conical lens 4 from being optically coupled to the optical fiber end surface 1a and becoming noise light.

Furthermore, according to the present embodiment, since the light shielding portions 48 to 50 are provided in addition to the light shielding portion 42, light passing through the inner side of the ring-shaped light beam L4 is more reliably suppressed from being optically coupled to the optical fiber end surface 1a. can.
In particular, even if flare light is generated by reflected light from an optical element in the optical probe 10E, the flare light components passing through the positions of the light shielding portions 48 to 50 can be further blocked, so noise light can be further reduced.

As described above, according to the present embodiment, by further providing the light shielding portions 45 to 50, generation of noise light can be further suppressed than in the second embodiment, so that more accurate displacement measurement is possible.

In addition, in the description of each of the above embodiments, an example in which the light emitting portion of the optical probe is formed from the tip portion 1b of the first optical fiber 1 has been described. However, the light emitting portion may be composed of a light emitting element having a light emitting surface arranged at the same position as the optical fiber end surface 1a. For example, a light-emitting element that can be used as the light emitting portion includes a semiconductor laser.

In the description of each of the above embodiments, an example in which the light receiving portion of the optical probe is formed from the tip portion 1b of the first optical fiber 1 has been described. However, the light-receiving part may be composed of a light-receiving element having a light-receiving surface arranged in the vicinity of the optical fiber end surface 1a in the optical axis direction. For example, the light receiving element 27 may be used as the light receiving section.

In the description of each of the above embodiments, the example in which the first light flux conversion element and the second light flux conversion element consist of a combination of the first conical lens 4 and the second conical lens 5 has been described. However, the first beam transforming element and the second beam transforming element are not limited to the combination of conical lenses. For example, a diffraction grating, a hologram element, or the like may be used as the first beam conversion element and the second beam conversion element. For example, a combination of a conical lens, a diffraction grating, a hologram element, or the like may be used as the first beam conversion element and the second beam conversion element.

In the description of each of the above embodiments, the example in which the tip portion 1b of the first optical fiber 1 constitutes the light emitting portion and the light receiving portion of the optical probe has been described. However, the light emitting section and the light receiving section may be made of different members.
For example, in the first embodiment, a beam splitter may be provided on the optical path of the emitted light flux L1 to split the light flux returning along the optical path of the emitted light flux L1. In this case, a light receiving section is provided on the branched optical path. In the interferometric method, the beam splitter plane can be used as a reference plane. The fiber optic coupler 24 of the reference member 2 and the metrology unit 20 is eliminated.
For example, in the first embodiment, a beam splitter may be provided on the optical path of the parallel light flux L2 to split the light flux returning on the optical path of the parallel light flux L2. In this case, a condensing lens (third condensing optical element) similar to the first condensing lens 3 and a light receiving section are provided on the branched optical path. In the interferometric method, the beam splitter plane can be used as a reference plane. In this case, the reference member 2 and the optical fiber coupler 24 of the measuring unit 20 are omitted. This modification is an example in which the first condensing optical element and the third condensing optical element are different.

In the description of each of the above embodiments, the example in which the first beam conversion element constitutes the second beam conversion element has been described, but the second beam conversion element may be different from the first beam conversion element.
For example, in the first embodiment, a beam splitter is provided on the optical path of the ring-shaped luminous flux L4 between the second conical lens 5 and the second condenser lens 6, whereby the luminous flux returning along the optical path of the parallel luminous flux L2 may be branched. In this case, the second light flux converting element, the third condensing optical element, and the light receiving section are provided on the branched optical path. For example, a configuration similar to that of the first conical lens 4 and the second conical lens 5 may be used as the second beam converting element. For example, an optical element similar to the first condenser lens 3 may be used as the third condenser optical element. In the interferometric method, the beam splitter plane can be used as a reference plane. In this modification, the first optical path changing element and the second optical path changing element are different from each other, and the first condensing optical element and the third condensing optical element are different.
Similarly, by providing a beam splitter on the optical path between the first conical lens 4 and the second conical lens 5 in the first embodiment, the light beam returning along the optical path of the bent light beam L3 or the ring-shaped light beam L4 is split. may be In this case, an optical element similar to the first conical lens 4, a third condensing optical element, and a light receiving section are provided on the branched optical path. This modification is an example in which the first optical path changing element and the second optical path changing element share a part.

In the description of each of the above embodiments, an example in which the first condenser lens 3 converts the emitted light flux L1 into the parallel light flux L2 has been described. In this case, the lens interval between the first conical lens 3 and the first conical lens 4 and the lens interval between the second conical lens 5 and the second conical lens 6 can be freely changed as required. .
However, the first condenser lens 3 may condense the emitted light flux L1 into non-parallel light.

In the second and fourth embodiments, the light shielding part 43 is arranged on the optical path of the bent light flux L3, and the light shielding part 44 is the light of the ring-shaped light flux L4 between the first conical lens 4 and the second conical lens 5. An example of the case where it is arranged on the road has been explained. However, the arrangement positions of the light shielding portions 43 and 44 are not limited to this.
For example, the light blocking portion 43 may be arranged on the optical path of at least one of the emitted light flux L1 and the parallel light flux L2.
For example, the light shielding part 44 may be arranged on the optical path between the second conical lens 5 and the second condenser lens 6 .

In the description of the second to fifth embodiments, the example in which the second light shielding portion such as the light shielding portion 42 is equal to or smaller than the inner diameter of the ring-shaped light flux L4 has been described. However, the second light shielding portion may be larger than the inner diameter of the ring-shaped light flux L4. In this case, the second light shielding portion is a beam shaping member that regulates the beam diameter of the inner peripheral portion of the ring-shaped beam L4.
Similarly, the inner diameters of the third light shielding portions such as the light shielding portion 44 and the fourth light shielding portions such as the light shielding portion 42 may be smaller than the outer diameters of the light beams passing therethrough. In this case, the third light shielding part and the fourth light shielding part are light beam shaping members that regulate the light beam diameter of the outer peripheral portion of the light beams passing therethrough.

In the description of each of the above embodiments, an example in which displacement measurement is performed by an interferometer method has been described. However, the configuration example in the interferometer system is not limited to the above example.
For example, a configuration in which the optical fiber coupler 24, the condenser lens 26, and the reference member 2 are omitted from the first embodiment is also possible. In this case, by disposing a first beam splitter between the light source 21 and the coupling lens 22, the light passing through the coupling lens 22 to the object side is branched to form a first branched optical path. . A light receiving element 27 is arranged on the first branched optical path. Further, a second beam splitter is arranged in the optical path between the coupling lens 22 and the first optical fiber 1 to split the light flux L0 to form a second branched optical path. A reflective reference member is provided on the second branched optical path. The light reflected by the reference surface of the reference member travels backward along the optical path, is split by the first beam splitter, and enters the light receiving element 27 .
For example, a configuration in which the reference member 2 is deleted in the first embodiment is also possible. In this case, instead of the optical fiber coupler 24, an optical fiber coupler having four ports is used. The light flux L0 is split between the second port 24b and the fourth port. A light beam L0 emitted from the fourth port is condensed by a condensing lens, reflected by a reflective reference member, and optically coupled to the fourth port through the condensing lens. The light beam optically coupled to the fourth port enters the light receiving element 27 through the third port 24c. This modification is an example in which the optical system composed of the above-described first and second beam splitters is composed of an optical fiber coupler having four ports.

In the description of each of the above embodiments, the case where the displacement measurement is performed by the interferometer method has been described. However, displacement measurements may also be made in a coaxial confocal manner. For example, according to the configuration in which the reference member 2 is omitted in the first embodiment, coaxial confocal displacement measurement is possible.
In that case, the optical path splitting by the optical fiber coupler 24 may be replaced with an optical path splitting using a beam splitter.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Configuration additions, omissions, substitutions, and other changes are possible without departing from the scope of the present invention.
Moreover, the present invention is not limited by the foregoing description, but only by the appended claims.

1 first optical fiber 1a optical fiber end face 1b tip (light emitting part, light receiving part)
2 reference member 3 first condenser lens 4 first conical lens (first beam conversion element, second beam conversion element)
4a, 5a conical surfaces 4c, 5c vertex 5 second conical lens (first light flux conversion element, second light flux conversion element)
6 Second condenser lens 7 Optical probe moving part (first moving part)
10a Housings 10A, 10B, 10C, 10D, 10E Optical probe 21 Light source 27 Light receiving element 28 Displacement meter side part 30 Stage 31 Holding part 32 Moving part (second moving part)
40 lens to be measured (object to be measured)
40a first surface (surface to be measured)
40b second surface 41, 45, 46, 47 light shielding portion (first light shielding portion)
42, 48, 49, 50 light shielding portion (second light shielding portion)
43 light shielding part (fourth light shielding part)
44 light shielding part (third light shielding part)
60A, 60B, 60C, 60D, 60E Optical displacement meter 70 Surface shape measuring instrument 100 Control unit E1 First end E2 Second end L0, L3a, L3b, L5a, L6a, L6b Light beam L0r Reflected light beam L1 Emitted light beam L2 Parallel Light flux L2a On-axis light flux L3 Bending light flux L4 Ring-shaped light flux L5 Ring-shaped condensed light flux L6 Reflected light flux L7 Diameter-reduced light flux O Optical axis P Measurement reference position

Claims (11)

a light emitting portion that emits light;
a first condensing optical element condensing the light emitted from the light emitting section;
a first beam conversion element that converts the beam condensed by the first condensing optical element into a ring-shaped beam by bending the beam in a direction that intersects the optical axis;
a second condensing optical element condensing the ring-shaped luminous flux, irradiating the condensed light onto the surface to be measured, and condensing the reflected light from the surface to be measured;
A second luminous flux that converts the reflected light into a diameter-reduced luminous flux that is reduced in diameter by moving a peripheral light component of the reflected light that passes through a peripheral portion of the second condensing optical element to the vicinity of the optical axis. a conversion element;
a third condensing optical element for condensing the diameter-reduced light flux;
a light receiving unit that receives the condensed diameter-reduced light flux;
an optical probe. The first beam conversion element constitutes the second beam conversion element,
The first condensing optical element constitutes the third condensing optical element,
The optical probe according to claim 1. At least one of the first beam transforming element and the second beam transforming element includes a pair of conical lenses,
The optical probe according to claim 1. the first collection optical element forms parallel light from the light;
The optical probe according to claim 1. The light receiving unit includes an optical fiber into which the diameter-reduced light flux condensed by the third condensing optical element is incident,
The optical probe according to claim 1. further comprising a first light shielding unit that shields an axial light beam in the light beam before being converted into the ring-shaped light beam;
The optical probe according to claim 1. Further comprising a second light shielding part that shields light passing through the inside of the ring-shaped light beam,
The optical probe according to claim 1. Further comprising a third light shielding part that shields light passing outside the ring-shaped light beam,
The optical probe according to claim 1. Further comprising a fourth light shielding unit that shields light passing outside the light beam before being converted into the ring-shaped light beam,
The optical probe according to claim 1. an optical probe according to claim 1;
a first moving unit that relatively moves the optical probe with respect to the surface to be measured at least in the optical axis direction;
a displacement measuring unit that measures the displacement of the surface to be measured in the optical axis direction based on the light intensity signal received by the light receiving unit;
An optical displacement meter, comprising: a holding section that holds the object to be measured;
an optical displacement meter according to claim 10;
a second moving unit that relatively moves the optical displacement meter with respect to the holding unit at least in a direction that intersects the optical axis;
A profilometer, comprising:

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