JP3554373B2 - Distance measuring optical system - Google Patents

Description

[0001]
The present invention relates to a distance measuring optical system.
[0002]
[Prior art and its problems]
The ranging optical system is used, for example, in a lightwave ranging device. FIG. 3 is a view showing the configuration of a conventional example, in which 1 is a light source such as an LED, 2 is a light receiving element, 3 is a half mirror, 4 is an objective lens system, and 5 is a prism for splitting light. A light splitting element, 6 is a prism for image inversion, and 7 is an eyepiece. The objective lens system 4 includes a front group 4a and a rear group 4b, and a light splitting element 5 is located between the two groups.
[0003]
An optical system including the objective lens system 4, the light splitting element 5, the image inverting prism 6, and the eyepiece 7 confirms a distance measuring object (generally, a corner cube) CC with eyes, that is, with visible light. To make up a telescope.
[0004]
The light source 1 emits infrared light as a first light flux. This infrared light has a wavelength of about 850 nm, and has a different wavelength from the visible light as the second light flux. The infrared light emitted from the light source 1 passes through the half mirror 3 and reaches the light splitting element 5 for splitting light. A dichroic coat made of a dielectric multilayer film for reflecting infrared light and transmitting visible light is formed on the division surface 5a of the light dividing element 5. Therefore, the infrared light from the light source 1 is reflected by the dichroic coat, passes through the front group 4a of the objective lens system 4, and then travels to the corner cube CC.
[0005]
The infrared light reflected by the object to be measured returns to the front group 4a of the objective lens system 4, is reflected again by the dichroic coat of the light splitting element 5, is further reflected by the half mirror 3, and enters the light receiving element 2. .
[0006]
As is well known in principle, the lightwave distance measuring device emits infrared light from the light source 1 in a pulsed manner at a predetermined frequency. The time until the light is reflected by the cube CC and enters the light receiving element 2 is detected based on the phase shift between the pulses of the distance measuring light and the reference light, and the distance to the object to be measured is calculated.
[0007]
By the way, the dichroic coat used in the above configuration has a property that its spectral characteristic changes depending on the incident angle of light incident on this coat. FIG. 4 is a diagram illustrating this spectral characteristic, in which the vertical axis represents transmittance (%) and the horizontal axis represents light wavelength. The solid line shows the relationship between the wavelength and the transmittance when the incident angle is 45 °, the broken line shows the relationship at 30 ° and the dashed line shows the relationship at 15 °. The angle of incidence is 0 ° for normal incidence. From this figure, it can be seen that when the incident angle is 15 °, almost 100% of the light is transmitted up to a wavelength of about 750 nm, which is the limit of visible light, and almost 100% of the longer wavelength is reflected. Next, when the incident angle is 30 °, the transmittance starts to decrease from around 700 nm, which is near the upper limit of visible light, but it can be transmitted by about 50% up to about 750 nm, and it can be said that it has almost the same characteristics as the target.
[0008]
However, when the incident angle becomes 45 °, the transmittance from around 600 nm in the visible light region drops to 50% or less, and the transmittance becomes almost 0% between 700 nm and 750 nm. The red component of the image will be significantly reduced. In addition, a slight shift of the observer's eye in a direction orthogonal to the optical axis of the eyepiece 7 changes the color tone of the object being observed.
[0009]
On the other hand, the light incident on the dichroic coat is divergent light from the light source 1 or convergent light that is light returned from the measurement target, and thus has a wide angle at which the light enters the dichroic coat. For example, assuming that the angle α between the reflection film 5a and the optical axis O of the objective lens 4 is 60 °, the incident angle β of the principal ray (the incident ray overlapping with the optical axis) is 30 °. However, the incident angles of the upper ray and the lower ray have a width of about ± 15 ° and extend from 15 ° to 45 °, depending on the F-number of the objective lens. As described above, the spectral characteristic is within the allowable limit up to an incident angle of about 30 °, but when the incident angle is 45 °, the spectral characteristic deteriorates, and there is a problem that the light use efficiency is greatly reduced.
[0010]
[Object of the invention]
The present invention has been made to solve the above problem, and the angle of the incident light beam with respect to the dichroic coat surface does not change, so that the light use efficiency is high, and even if the positional relationship between the eyepiece and the eye is displaced, the object is not affected. It is an object of the present invention to provide a distance measuring optical system in which a color tone does not change.
[0011]
SUMMARY OF THE INVENTION The present invention provides a light source that emits a light beam for distance measurement; a light splitting element having a dichroic coated surface that reflects the light beam from the light source and transmits visible light; a collimator lens group, a divergent lens, An objective lens system for projecting the light beam reflected by the dichroic surface onto the object to be measured, and condensing the light beam reflected by the object to be measured and reflected again by the dichroic coat surface A collimating optical system including an objective lens system , a divergent lens, a condenser optical system, and an eyepiece, wherein a visible light beam among light beams reflected by the object to be measured passes through a dichroic coat surface of the light splitting element; In the distance measuring optical system provided with, in the light projecting and receiving optical system and the collimating optical system, a parallel light beam system in which light beams are parallel to each other is provided, and in this parallel light beam system, a light splitting element is provided. Dichroic It is characterized in that the coated surface is located.
[0012]
As described above, if the dichroic coat surface of the light splitting element is arranged in the parallel light beam, the parallel light beam always enters the coat surface, so that the spectral characteristics are not adversely affected. The parallel light beam system can be configured by, for example, an afocal optical system including an objective lens system and a diverging lens, or an afocal optical system including an objective lens and a condenser lens. In the former case, there is an advantage that the entire length of the optical system can be shortened and the size can be reduced. In the latter case, since the image is formed once in the parallel light beam system, a prism for image reversal becomes unnecessary and the cost is reduced. .
[0013]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a collimator lens group for converting a first light beam emitted from the light source 1 into parallel light . The collimator lens group 11 , the diverging lens 12, and the objective lens system 4 constitute a light projecting and receiving optical system. The objective lens system 4 and the diverging lens 12 constitute an afocal optical system 20.
[0014]
On the other hand, the objective lens 4, the diverging lens 12, the condenser optical system 13, and the eyepiece 7 constitute a collimating optical system (telescope). Between the diverging lens 12 and the condensing optical system 13, there is a parallel light system in which the light beams are parallel, which is common to the light projecting / receiving optical system and the collimating optical system. The light splitting element 5 is arranged. The collimating optical system is used to search for a distance measurement target such as a corner cube CC using visible light.
[0015]
That is, the infrared light emitted from the light source 1 as the distance measuring light beam is an LED light having a wavelength of 850 nm, transmits through the half mirror 3, further passes through the collimator lens group 11, is converted into a parallel light beam, and is split by the light splitting element. 5 and reaches a dichroic-coated division surface 5a. Since the dichroic coat reflects infrared light, the light beam from the light source 1 is reflected here and passes through the afocal optical system 20 to irradiate the corner cube CC.
[0016]
The infrared light, which is the distance measuring light beam reflected from the corner cube CC, is superimposed on the visible light, passes through the afocal optical system 20, and proceeds to the light splitting element 5 in a parallel light state. When the light reaches the division surface 5a, the infrared light is reflected, goes backward through the collimator lens group 11, is reflected by the half mirror 3, and reaches the light receiving element 2. As described above, the distance from the light source 1 to the light reflected from the corner cube CC and incident on the light receiving element 2 is detected from the phase shift between the pulses of the distance measuring light and the reference light. Is calculated.
[0017]
On the other hand, the visible light passes through the splitting surface 5a, passes through the condensing optical system 13, passes through the prism 6 for image inversion, and reaches the eyepiece 7. By moving all or part of the condensing optical system 13 in the optical axis direction, the collimating optical system can be focused.
[0018]
In the above configuration, since the distance measuring light beam and the collimating light beam incident on the division surface 5a of the light splitting element 5 are both parallel light beams, the upper light beam and the lower light beam are parallel to the main light beam. It has the same angle of incidence as the light beam. Therefore, by appropriately setting the angle γ between the optical axis of the collimator lens group 11 and the optical axis of the afocal optical system 20, the incident angle can be set to an angle that does not affect the spectral characteristics. Also, when using the telescope, the color tone does not change even if the relative position between the eye and the eyepiece 7 changes.
[0019]
FIG. 2 shows a second embodiment of the present invention. In this embodiment, the afocal optical system 20 of the collimating optical system is composed of the objective lens system 4 and the condenser lens 15 having a positive power. Once formed an image. Further, an image is formed once more between the condensing optical system 16 and the eyepiece 7. Since the image is formed twice between the objective lens system 4 and the eyepiece 7 in this manner, the image in the collimating optical system is an erect image, and the image inversion prism 6 used in the first embodiment becomes unnecessary. Therefore, the configuration is simplified, and the manufacturing cost of the telescope can be reduced. Other configurations are common to the first embodiment, and common components are denoted by common reference numerals.
[0020]
【The invention's effect】
As described above, according to the present invention, a light splitting element having a dichroic coat surface that reflects a distance measuring light beam and transmits visible light is provided by a parallel light beam commonly provided in a light projecting / receiving optical system and a collimating optical system. Since it is located in the system, the angle of incidence of the distance measuring light beam and the visible light beam incident on the dichroic coat surface is always constant, and the incident angle of the upper ray and the lower ray coincides with the incident angle of the principal ray. It is no longer affected by spectral characteristics. Further, when the distance measuring optical system of the present invention is applied to a telescope of the distance measuring optical system, the color tone of the object does not change even if the positional relationship between the eyepiece and the eye is shifted.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first embodiment of a distance measuring optical system of the present invention.
FIG. 2 is a diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a conventional distance measuring optical system.
FIG. 4 is a diagram showing spectral characteristics of a dichroic coat.
[Explanation of symbols]
Reference Signs List 1 light source 4 objective lens system 5 light splitting element 5a splitting surface 7 eyepiece 11 collimator 20 afocal optical system

Claims (3)

A light source that emits a light beam for distance measurement;
A light splitting element having a dichroic coat surface that reflects a distance measuring light beam from this light source and transmits visible light,
A collimator lens group, a diverging lens, and an objective lens system are provided, and the light beam reflected on the dichroic surface is projected on the object to be measured, and the light beam reflected on the object for distance measurement and reflected again on the dichroic coat surface. Optical system for condensing light,
A collimating optical system including the objective lens system , the diverging lens, a condenser optical system, and an eyepiece, wherein a visible light beam among light beams reflected by the object to be measured passes through a dichroic coat surface of the light splitting element. When,
In a ranging optical system with
In the light emitting and receiving optical system and the collimating optical system, a parallel light beam system in which light beams are parallel to each other is provided, and a dichroic coat surface of the light splitting element is located in the parallel light beam system. A distance measuring optical system characterized by the above. 2. The distance measuring optical system according to claim 1, wherein the parallel light beam system is configured by an afocal optical system including the objective lens system and the diverging lens . A light source that emits a light beam for distance measurement;
A light splitting element having a dichroic coat surface that reflects a distance measuring light beam from this light source and transmits visible light,
A collimator lens group, a condenser lens, and an objective lens system are provided, and the light beam reflected on the dichroic surface is projected on the object to be measured, reflected on the object for distance measurement, and reflected again on the surface of the dichroic coat. A light emitting and receiving optical system for condensing a light beam;
Collimating optics comprising the objective lens system, the condenser lens, the condenser optical system, and an eyepiece, wherein a visible light beam among light beams reflected by the object to be measured passes through a dichroic coat surface of the light splitting element. System and
In a ranging optical system with
In the light emitting and receiving optical system and the collimating optical system, a parallel light beam system in which the light beams are parallel to each other is provided,
In this parallel light flux system, the dichroic coat surface of the light splitting element is located,
The parallel beam system is an afocal optical system including the objective lens system and the condenser lens, and a distance measuring optical system that forms an image once between the objective lens and the condenser lens.

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