JP3336640B2 - Interferometer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interferometer apparatus for inspecting the surface condition of a lens such as a lens using a laser interferometer.

[0002]

2. Description of the Related Art Conventionally, a laser interferometer is used to inspect the finishing accuracy of a lens. That is, a reference lens serving as a reference for a lens is provided in an optical path of a laser beam from a laser light source, and a test lens is provided at a position in front of the reference lens in the optical path, and light reflected from a reference surface of the reference lens is provided. The surface condition of the lens is inspected by measuring the number of interference fringes generated between the light and the reflected light from the surface to be inspected of the lens to be inspected. As described above, the use of the laser interferometer allows the inspection lens to be inspected in a non-contact manner, so that the inspection can be precisely performed without damaging the reference lens and the inspection lens, which is extremely convenient.

In general, if the lens to be inspected is a spherical lens, the reference lens is also a spherical lens. However, whether the lens to be inspected is a convex lens or a concave lens, the radius of curvature of the reference lens and the radius of curvature of the lens to be inspected are determined. By observing the interference fringes at a position separated by the distance of, the lens to be measured can be measured. Here, in practice, the reference lens has a certain limit in the range in which the optimum measurement can be performed.
Prepare about several types of reference lenses, and replace the reference lens according to the type of the lens to be measured, that is, whether it is a concave lens or a convex lens, the effective aperture or radius of curvature of the surface to be measured, etc. And use it.

In practice, a reference lens is incorporated as a main body of an interferometer together with a laser light source, an optical system, imaging means for interference fringes, and the like, and a test lens is configured to be detachably set on a lens mount. The main body or the lens mount is connected to the displacement means and is moved by the displacement means so that the distance between the reference lens and the test lens is adjusted to the measurement position.

[0005]

As described above, the reference lens mounted on the main body of the interferometer is selected from a plurality of types. Then, it is necessary to confirm whether or not measurement is possible with the reference lens currently mounted on the interferometer main body, and when a reference lens that is not suitable for the measurement is mounted, it is necessary to replace it. Here, the interferometer device according to the related art is not necessarily configured to easily replace the reference lens.

Usually, the optical path of the laser light from the laser light source to the reference lens is housed in the housing of the main body of the interferometer, but the optical path between the reference lens and the lens to be measured adjusts the optical path length. For that reason, they cannot be provided in the housing. However, if this part is exposed to the outside, there is a possibility that disturbance due to air flow may occur,
Observation of stable interference fringes cannot be performed. In view of the above, the present applicant has provided a substantially sealed main body casing, provided the interferometer main body under the top plate of the main casing so as to be able to ascend and descend, and provided an upper position of the top plate section. The lens mount on which the lens to be tested is set is mounted, and the top plate is formed with a through hole to secure the optical path of the laser beam between the reference lens and the lens to be tested. Things developed. With such a configuration, disturbance of the laser beam does not occur, and the interference fringe fringes are stabilized.

However, if the entire interferometer main body is housed in the main body casing in this way, there is a problem that the work of attaching and detaching the reference lens becomes troublesome. In particular, if the main body casing is formed small in order to make the apparatus compact and means for driving the interferometer main body up and down are provided in the main body casing, the work of replacing the reference lens becomes extremely difficult.

The present invention has been made in view of the above points, and an object of the present invention is to make it possible to easily replace a reference lens mounted on an interferometer body.

[0009]

In order to achieve the above-mentioned object, the present invention provides a main body casing having a top plate having a through-hole, a laser oscillator, an optical system for guiding laser light, The interferometer body, which has a reference lens that reflects a part of the laser light from the light guiding optical system and transmits a part of the laser light, Place the lens mount where the lens is set on the top of the top plate,
The reference lens and the test lens are arranged so as to face each other with the through hole interposed therebetween, and the lens mount is provided on the top plate so as to open the through hole forming portion, and the interferometer The main body is provided to be able to move up and down, and the through hole is
That allows the reference lens mounting part of the main body of the interferometer to be inserted
It is characterized by having a shape .

[0010]

Even if the main body of the interferometer is housed in the main body casing, the lens mount must be disposed outside the main body casing because the lenses to be inspected and measured must be set in order. For this purpose, the interferometer main body is arranged below the main body casing and a lens mount is provided above. Then, a through-hole is formed in the top plate to secure an optical path of the laser light between the reference lens and the lens to be measured. The reference lens mounted on the main body of the interferometer is attached and detached using the through holes.

In order to replace the reference lens, the opening position of the through hole in the top plate of the main body casing is first opened by removing the lens mount or the like. And
Attachment part of reference lens in interferometer body through through hole
Raise it to a position higher than the top surface of the
Desorption After that, a new reference lens is attached. Next, when the interferometer main body is located above the top panel, the interferometer main body is lowered, or when the interferometer main body is located below the top panel, the interferometer main body is left as it is. Then, reattach the lens mount. Since the reference lens is mounted upward at the upper end of the main body of the interferometer, it is reasonable to attach and detach the reference lens from the upper side, and when the reference lens is mounted, its positioning can be easily performed.

If the lens mount has a movable structure, accurate positioning may not be achieved. In such a case, the position adjustment between the reference lens and the test lens can be performed by providing the lens mount with the position adjusting means for the test lens.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. First, in FIG. 1, reference numeral 1 denotes an interferometer main body, and the interferometer main body 1 is mounted on a main body casing 2. The main body casing 2 is a closed space in order to prevent the occurrence of air disturbance inside the main body casing 2, and the interferometer main body 1 is provided inside the main body casing 2 with an elevating means mounted on a top plate 2a. 3 so as to be vertically displaceable. Further, a through hole 4 is formed in the top plate 2a, so that the laser beam from the interferometer main body 1 can be led out through the through hole 4. The test lens 5 whose surface condition is to be measured is set on the lens mount 6 disposed on the upper surface side of the through hole 4 so that the test surface 5a faces the interferometer main body 1 side. It is configured. In the drawing, reference numeral 7 denotes an anti-vibration support member for holding the top plate 2a from transmitting external vibrations.

FIG. 2 shows an example of the main body 1 of the interferometer. The figure shows a so-called Fizeau interferometer, but it goes without saying that the interferometer used in the present invention is not limited to this type. In FIG. 1, reference numeral 10 denotes a laser oscillator 10 composed of a He—Ne laser or the like. The laser light output from the laser oscillator 10 is once focused by a diverging lens 11 for beam divergence. Diverge. A pinhole 12 is provided at the condensing position of the diverging lens 11, so that light other than the condensed light is cut off from the optical path. The light passing through the pinhole 12 is reflected by the reflection surface 13a of the beam splitter 13. The light reflected by the beam splitter 13 is converted into a parallel light by a collimator lens 15 via a quarter-wave plate 14, and the parallel light is converted into a reference lens 16 as a reference member.
Is incident on. The entrance surface 16a of the reference lens 16 is coated with an anti-reflection coating.
The surface opposite to the reference surface 16b is a reference surface 16b. The reflected light from the reference surface 16b forms a reference wavefront as reference light with respect to the measurement wavefront which is the object light reflected from the surface 5a of the lens 5 to be measured. I do.

When the lens 5 to be measured is mounted on the lens mount 6, the reference lens 1 from the laser oscillator 10 passes through the diverging lens 11, the pinhole 12, the beam splitter 13, and the collimator lens 15 which constitute a laser light guiding optical system.
6, a part of the light is reflected by the reference surface 16b of the reference lens 16, and the other is incident on the lens 5 to be inspected and reflected by the surface 5a of the lens 5 to be inspected. Reference lens 16
The reflected light from the reference surface 16b and the test surface 5a of the test lens 5 is returned to the beam splitter 13 via the quarter wavelength plate 14 while being converged by the collimator lens 15. Here, this return light passes through the reflection surface 15a of the beam splitter 13. The optical path of the transmitted light of the beam splitter 13 includes an aperture 17 and an imaging lens 1.
An interference fringe is formed at the imaging position of the imaging lens 18 by the interference between the reference light from the reference surface 16b and the object light from the test surface 5a. An imaging means 19 composed of a CCD or the like is provided at the image forming position, and the imaging means 19 captures interference fringes. The imaging means 19 is connected to a monitor device 20, and the monitor device 20 displays an interference fringe image.

As described above, the surface condition of the lens 5 to be inspected is inspected by observing the interference fringes. In this interferometer device, not only a single type of lens to be inspected is measured, but also The measurement is performed by appropriately replacing a plurality of types of lenses to be measured.

As shown in FIG. 3, when the test lens 5 is a spherical lens, whether it is a concave lens or a convex lens, the reference surface 16b of the reference lens 16 is formed as a concave spherical surface. Is a concave lens 5P,
From the reference lens 16, if placed at a position separated by a distance D ₁ which corresponds to the sum of the curvature radius R ₂ of curvature R ₁ and a test lens 5P of the reference lens 16, the interference fringes is minimized at the position, By measuring the number of interference fringes at this time,
The surface condition of the lens to be measured can be measured. When the test lens is a convex lens 5V, the reference lens 16
Disposing of at a position separated by a distance D ₂ which corresponds to the difference between the radius of curvature R ₃ of the lens 5V radius of curvature R ₁ Toko.

However, when the test lens is a large lens as indicated by reference numeral 5L, the laser beam does not hit the periphery of the lens 5L, and is indicated by reference numeral 5S. With a small lens, the monitor screen 20a
The image of the interference fringes displayed in the image becomes small, and the observation thereof becomes difficult. Furthermore, when the test lens is a convex lens 5V radius of curvature R ₁ or more lenses of the reference lens 16 can not be measured. Further, the movable range of the interferometer main body 1 on which the reference lens 16 is mounted has a limit. From the above, there is a limit to the measurement range to the reference lens, the reference record that is mounted to the currently interferometer 1 by the test lens
Measurement 16 may not be possible. Therefore, the reference lens mounted on the interferometer main body 1 must be replaced according to the type of the lens to be inspected. For this purpose, the reference lens 16 is configured to be detachably mounted at the tip of the interferometer main body 1.

The reference lens 16 can be replaced through the through hole 4 formed in the top plate 2a.
For this purpose, the through-hole 4 is provided between the reference lens 16 and the test lens 5.
And the mounting portion of the reference lens 16 of the interferometer main body 11 projects through the through hole 4 to a position above the upper surface of the top plate 2a. It has a configuration that can be performed. In addition, the lens mount 6 is disposed at a position above the through hole 4 and is configured to be displaceable between an operating position where the lens 5 to be tested can be set and a retracted position where the through hole 4 is opened. I have. 4 and 5 show the configuration of the lens mount 6. FIG.

As is apparent from FIG. 1, the lens mount 6 includes a base 21, an XY table 22 and an angle adjuster 2.
And an angle adjusting unit 2 comprising:
The lens set 24 is mounted on the lens set 3. Base 21
Has an outer shape capable of completely covering the entire through hole 4, and has a light guide opening 21a formed in the center. A pair of X-axis guides 25 that guide the X-axis direction of the XY table 22 are attached to the upper surface of the base 21. The X-axis guide 25 is for guiding the X-axis table 26.
A pair of Y-axis guides 27 are mounted on the axis table 26. A Y-axis table 28 is provided on the Y-axis guide 27.
Are guided in the X-axis direction. And
In order to adjust the positions of the X-axis table 26 and the Y-axis table 28, these are provided with micrometer heads 29, 30.
Is connected. The X-axis table 26 and the Y-axis table 28 are provided with light guide openings 26a and 28a.

The angle adjusting section 23 has a support plate 31, which is screwed into three screw shafts 32 protruding from the Y-axis table 28. An adjusting head 32a is continuously provided at the tip of each of the three screw shafts 32.
By appropriately screwing the adjustment head 32a, the tilt of the support plate 31 can be adjusted. The lens setting section 24 includes the support plate 31
It is mounted interchangeably by screwing it in.

The lens mount 6 configured as described above
Are detachably attached to the top plate 2a of the main body casing 2. For this reason, the top plate 2a has
Two positioning pins 33 are provided around the portion where the through hole 4 is formed.
Is erected. On the other hand, the base 21 of the lens mount 5 is provided with a positioning hole 34 into which the positioning pins 33 are inserted. Also, the base 21
, A fixing screw 35 is inserted into the four corners thereof, and the fixing screw 35 is adapted to be screwed into a screw hole 36 provided in the top plate 2a.

The interferometer device is constructed as described above. In order to inspect and measure the lens 5 having a predetermined radius of curvature and an effective aperture, the lens 5 is mounted on a lens mount. The laser beam is emitted from the laser oscillator 10 by setting the laser beam on the reference surface 1 of the reference lens 16.
An interference fringe generated between the reference light reflected on the target surface 6a and the object light reflected on the test surface 5a of the test lens 5 is monitored by the monitor device 20.
And by observing this interference fringe image,
Measurement of the finishing accuracy of the test surface 5a of the test lens 5 is performed.

Here, as described above, it is necessary to replace the reference lens 16 according to the type of the lens 5 to be inspected. To replace the reference lens 16, first, the fixing screw 35 for fixing the base 21 of the lens mount 6 to the top plate 2a of the main body housing 2 is loosened, and the lens mount 6 is separated from the top plate 2a. I do. In this state, the lifting means 3
The interferometer body 1 at the tip of the reference lens 1
The mounting portion 6 is raised to a position protruding from the through hole 4 formed in the top plate portion 2a. Thus, the interferometer main body 1 is housed in the main body casing 2 which forms a substantially closed space, but the mounting portion of the reference lens 16 is attached to the top plate portion 2a.
, The reference lens 16 can be replaced outside the main body casing 2. Moreover, since the reference lens 16 is arranged upward, the reference lens 16 can be positioned by simple positioning means, and can be easily attached and detached.

When the replacement of the reference lens 16 is completed, the lens mount 6 is set at the original position on the top plate 2a. In this operation, first, the base 21 is placed on the top plate 2a with the positioning pins 33 provided on the top plate 2a fitted into the positioning holes 34 of the base 21. Thereafter, the fixing screw 35 is tightened. Thereby, the lens mount 6 can be fixed on the top plate 2 a of the main body casing 2.

Here, due to the nature of measuring interference fringes, the distance between the reference lens 16 newly mounted on the interferometer main body 1 and the test lens 5 set in the lens setting section 24 of the lens mount 6 is set. The position adjustment must be performed very strictly. If the lens mount 6 is detached from the top plate 2a when the reference lens 16 is replaced, there is a possibility that a positional shift between the two lenses 5 and 16 may occur. Since the reference lens 16 and the test lens 5 change, it is natural that the distance between them has to be changed. The adjustment of this distance is performed by operating the elevating means 3.
The position adjustment between the lenses 5 and 16 is not limited to this, and the position adjustment in the horizontal direction (XY direction) and the tilt direction (θ direction) must be performed between the lenses 5 and 16. The adjustment in the X and Y directions can be performed by operating the micrometer heads 29 and 30 in the XY table 22, and the adjustment in the θ direction can be performed by operating the adjustment head 32 a in the angle adjustment unit 23. In short, by adjusting the position of the lens setting section 24 in the lens mount 6, the reference lens 1
Position adjustment between the lens 6 and the test lens 5 can be performed.

Specifically, in order to perform this position adjustment, a so-called Newton prototype, which is an ideal shape of the test lens 5 to be measured, is set in the lens setting section 24, and the Newton prototype is set. The device is irradiated with laser light from the laser oscillator 10 to cause interference with the light reflected on the reference surface 16b of the reference lens 16, and this interference fringe is imaged by the imaging means 19 and transmitted to the monitor device 20. The image is displayed, and the interference fringe image displayed on the monitor device 20 is visually observed and adjusted so as to minimize the number of interference fringes.

When the above adjustments are completed, the Newton prototype is removed from the lens setting section 23, and the lens 5 to be inspected is mounted, so that the inspection and measurement of the lens 5 can be performed.

Since the reference lens 16 is arranged in the interferometer main body 1 so as to face the through hole 4 of the top plate 2a, the replacement is performed at a position above the top plate 2a. Therefore, the work can be performed very easily without any obstacles. Moreover, since the reference lens 16 mounted on the interferometer body 1 can be positioned by the action of its own weight, it is sufficient that the reference lens 16 is held so as not to move during operation. Be able to fix. As a result, the reference lens 1
6 can be exchanged more easily.

In the above-described embodiment, the lens mount is configured to be attachable to and detachable from the top plate using a fixing screw. In short, when exchanging the reference lens, the through hole in the top plate is opened. For example, it is possible to use a mechanism such as fixing the lens mount using a detachable clamp mechanism or connecting the lens mount and the top plate with a hinge to open and close the lens mount. It is. More lens mount Ru can also be adapted to have a position adjusting mechanism of the XY direction and the θ direction.

[0031]

As described above, according to the present invention, the reference lens mounted on the main body of the interferometer is exchanged by using the through hole formed in the top plate constituting the main body casing. Therefore, even if the main body casing is formed in a substantially sealed state to prevent disturbance by air, etc., the interferometer main body to which the main body casing is attached and the main body casing is formed small and compact, Various effects can be achieved such that the reference lens can be replaced very easily, accurately and quickly according to the type of lens.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an overall configuration of an interferometer apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an optical system in the interferometer apparatus.

FIG. 3 is an operation explanatory view showing a specific reference lens, a test lens that can be measured, and a test lens that is not suitable for measurement.

FIG. 4 is a sectional view of a lens mount.

FIG. 5 is a plan view of a lens mount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interferometer main body 2 Main body casing 2a Top plate part 3 Elevating means 4 Through-hole 5 Test lens 6 Lens mount 16 Reference lens 16b Reference surface 21 Base 22 XY table 23 Angle adjustment unit 24 Lens setting unit 33 Positioning pin 35 For fixing screw

Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 9/00-11/30 102 G01M 11/00-11/08

Claims (3)

(57) [Claims] 1. A laser oscillator, a laser light guiding optical system, and a part of the laser light from the light guiding optical system are reflected on a main body casing having a top plate having a through hole. , An interferometer body with a reference lens that transmits part of the light is located on the lower side of the top plate, and a lens mount on which the lens to be inspected and measured is set is located on the upper side of the top plate.
The reference lens and the test lens are arranged so as to face each other with the through hole interposed therebetween, and the lens mount is provided on the top plate so that the through hole forming portion can be opened, and the interferometer An interferometer apparatus characterized in that the main body is provided so as to be able to move up and down, and the through-hole has a shape that allows a reference lens mounting portion of the interferometer main body to be inserted. 2. The interferometer apparatus according to claim 1, wherein said lens mount is provided with a means for adjusting a position of a lens to be inspected. 3. The method of claim wherein the adjusting means is provided on a base which defines an opening for the light guide, and the base is characterized in that a configuration is found detachably mounted on the top plate 2. The interferometer device according to 2.