JPH0135306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical structure of a light wave distance measuring device that measures distance using light waves. As is well known, a light wave ranging device uses a light transmitting optical system to direct light from a light emitting element such as a light emitting diode that is modulated at a certain specified frequency to a reflector such as a corner cube placed at a measurement point. emit the light, and image the light returned from the reflector on a light-receiving element using a light-receiving optical system;
This is a device that measures distance by converting the reflected modulated light into an electrical signal and detecting the phase delay of the reflected modulated light with respect to the reference modulated light. In the case of such a light wave ranging device,
Distance measurement error is an important performance problem, and there are various optical and electrical causes for this error.

The present invention relates to an optical structure that eliminates the influence of phase unevenness of a light emitting section among the optical causes and reduces measurement errors.

Normally, in a light wave distance measuring device, a correction light is provided separately from the measurement light in order to correct measurement errors based on the optical path length within the device and the phase shift of the electronic circuit section, but how to capture this correction light. Unlike measurement light that uses emitted light near the optical axis of the light emitting section, a method that uses light in a range of emitted angles that are far away from the optical axis is often used mechanically. However, in this case, if there is phase unevenness due to a difference in the radiation angle, the phase difference between the measurement light and the correction light will change over time due to the mechanical setting position of the optical path or the temperature characteristics of the light emitting element, which will cause the distance to change. There is a problem that the measurement error increases. This phase unevenness is small and within an acceptable range near the optical axis in a highly directional type light emitting element, which is very effective in that a large amount of light can be emitted from a light wave ranging device. At radiation angles that are far from the axis, phase unevenness with respect to angle tends to be very large.

Conventional methods for reducing the influence of phase unevenness on the radiation angle include a method in which a light emitting element and an optical fiber are combined and the optical fiber is bent and placed in the optical path; There is a method of using a material with less unevenness.

However, it is difficult to achieve the objective by bending the optical fiber unless the optical fiber is bent extremely, and the bending can lead to the optical fiber breaking, impairing the reliability of the optical distance measuring device over time. In order to use a light-emitting element with little phase unevenness with respect to the radiation angle, it is necessary to select a light-emitting element whose light radiation characteristics are close to non-directional. The optical output is small in the narrow radiation angle range that is actually used, and when used in optical coupling with optical fibers, the coupling efficiency with them is very poor, and more power is required to compensate for the coupling loss. The disadvantage is that the amount of emitted light must be increased by supplying light to the light emitting element.

An object of the present invention is to provide a light wave distance measuring device which solves the drawbacks of the conventional methods described above and eliminates the disadvantages caused by phase unevenness, and its features are as follows.

In the present invention, a shutter is provided on the optical path between the light transmitting part and the objective lens to switch the light incident on the light receiving part into measurement light and correction light, and furthermore, the shutter is reflected at the position of the shutter when switching to the correction light. By attaching the member and condensing the reflected light with a condensing optical system, and using the light with a radiation angle range that is almost the same as the measurement light including the optical axis of the light transmitting section as correction light, the light of the light transmitting section can be adjusted. Unlike the case where light at a large angle with respect to the axis is used as correction light, it is not affected by phase unevenness with respect to the radiation angle that leads to measurement errors. Then, it becomes possible to use the highly directional light emitting element described above. Therefore, as mentioned above, large amounts of power must be supplied by bending the optical fiber and using omnidirectional light emitting elements, which have little phase variation with respect to the radiation angle but are inefficient as light wave ranging devices. The inconvenience of not having to do so will no longer occur.

Embodiments of the present invention will be described in detail below with reference to the drawings. In addition to the phase unevenness with respect to the radiation angle, there is a problem that the phase unevenness depending on the location of the light emitting surface of the light emitting element increases the distance measurement error.
It's called an optical rod. ) etc., it is already known that the phase unevenness depending on the location of the light emitting surface can be mixed and uniformed, and this problem can be solved. Therefore, in consideration of this fact in the embodiments of the present invention, a combination of a light emitting element and an optical fiber or an optical rod is considered as a light transmitting section. Here, it is clear that an optical fiber or an optical rod is not necessary for a light emitting element that has no phase unevenness depending on the location of the light emitting surface, and the light emitting element may be placed as it is as a light transmitting section.

FIG. 1 is a diagram showing an embodiment of the present invention regarding the optical structure of a light wave distance measuring device, in which 1 indicates a light transmitting section;
2 is a shutter for switching between measurement light and correction light, 3
4 is a driving device for the shutter 2, 4 is a reflecting member provided on the shutter 2, 5 is a light transmission optical path through hole, 6 is a light beam splitter, and 6a and 6b are light beam splitters 6.
7 is an objective lens, 8 is a corner cube, 9 is a light receiving section, 10 and 11 are condensing lenses for correction light, and 12 and 13 are reflection members for correction light.
2 is a diagram showing an embodiment of the light transmitting section 1 in FIG. 1, in which 14 is a light emitting element, 15 is a condenser lens, 16 is an optical fiber,
6a is the incident end face of the optical fiber 16;
16d is the output end face of the optical fiber 16. This optical fiber can also be an optical rod.

In FIG. 2, modulated light from the light emitting element 14 passes through the condenser lens 15 and forms an image on the incident end surface 16a of the optical fiber 16. The modulated light incident on the input end face 16a is transmitted by the optical fiber 16 and is emitted from the output end face 16b. This becomes the emitted light from the light transmitting section 1. In FIG. 1, the shutter 2 is a switching shutter that switches the light incident on the light receiving section 9 into either measurement light or correction light, and has a light transmission optical path through hole 5 that spans both measurement light and correction light. death,
It is rotated by a driving device 3 according to the measurement light and the correction light, and a reflection member 4 is attached to the shutter position when the correction light is used, and when the measurement light is selected, the emitted light from the light transmitting section 1 is Since there is no reflecting member 4 in place, the light passes through the shutter 2 as it is and reaches the light beam splitter 6. At this time, since the reflecting member is not set in the light transmission optical path, no light enters the correction light optical path. Further, when the correction light is selected, the emitted light from the light transmitting section 1 is reflected by a reflecting member 4 such as a mirror provided on the shutter 2 and guided to the correction light optical path. At this time, the measuring light is not present because the reflecting member is set in the light transmission optical path and the measuring light optical path is blocked. In other words, considering the case where the measurement light is selected now, the emitted light from the light transmitting section 1 passes through the light transmitting optical path through hole 5 of the shutter 2, and then is reflected by the reflecting surface 6a of the light beam splitter 6. The light passes through the objective lens 7, becomes a parallel beam of light, and is emitted to the outside. This emitted light is reflected by a corner cube 8 installed at the distance measurement point, and the reflected light passes through the objective lens 7 again, is reflected by the reflective surface 6b of the light beam splitter 6, and enters the light receiving section 9. This becomes distance measurement information. Further, when the correction light is selected, the emitted light from the light transmitting section 1 passes through the light transmitting optical path through hole 5 of the shutter 2, and then passes through the reflecting member 4.
, the light in the radiation angle range that is almost the same as the measurement light including the optical axis of the light transmitting section is reflected, and the correction light condensing lens 1
0, it becomes a parallel light beam, and the reflecting members 12 and 13
After being reflected by, the light is focused by the condensing lens 11 and enters the light receiving section 9, and becomes correction information for measurement errors based on the optical path length within the device and the phase shift of the electronic circuit section.

In this embodiment, the reflecting member 4 is attached to the shutter 2, and this shutter is rotated by the drive device 3, but the structure is such that the reflecting member is directly moved in and out of the optical path according to the measurement light and the correction light without using the shutter. But I can't blame you. FIG. 3 shows one embodiment of this, in which the reflecting member 4 is rotated by the drive shaft 17 of the drive device 3 according to the measurement light and the correction light, and is moved in and out of the optical path. As described above, the reflecting member 4 can be driven by any method as long as the measuring light and the correction light can be switched. Furthermore, in this embodiment, the parallel light beam from the condensing lens 10 is transmitted by the reflecting members 12 and 13, but an optical fiber is used for this part, and the condensing lens 10 reflects the light to the incident end of the optical fiber. A structure may also be used in which the reflected light from the member 4 is collected and transmitted by an optical fiber, and then the emitted light from the optical fiber is collected by a condensing lens 11 and enters the light receiving section 9.

As explained above, according to the present invention, a reflecting member is moved in and out of the optical path between the light transmitting unit and the objective lens according to the measurement light and the correction light, and the reflected light is focused by the focusing optical system, By using light with a reflection angle range that is almost the same as the correction light, unlike the case where light is used at an angle far away from the optical axis of the light transmitting section,
Since the influence of phase unevenness on the reflection angle can be removed and a large amount of emitted light can be obtained, it becomes possible to use a highly directional light emitting element, which is very effective in application to a light wave range finder. Therefore, a light emitting element with small phase unevenness with respect to the reflection angle is selected,
By supplying a large amount of power to the light emitting element and compensating for its poor emission efficiency, the inconvenience of securing the necessary amount of emitted light is eliminated, and it can be achieved with a fraction of the power supplied compared to that type of light emitting element. It becomes possible to obtain the above amount of emitted light. Therefore, it is a very effective device for reducing power consumption and electrical errors in a light wave distance measuring device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the optical structure of a light wave distance measuring device, FIG. 2 is a diagram showing an example of the light transmitting section, and FIG. 3 is a diagram showing an example of the driving section of the reflecting member. It is a figure showing an example. DESCRIPTION OF SYMBOLS 1... Light transmission part, 2... Shutter, 3... Shutter drive device, 4... Reflection member, 5... Light transmission optical path hole, 6... Light beam splitter, 6a, 6b...
Reflection surface of the light beam splitter 6, 7...objective lens,
8... Corner cube, 9... Light receiving section, 10,
11...Condensing lens for correction light, 12, 13...Reflection member for correction light, 14...Light emitting element, 15...Condenser lens, 16...Optical fiber, 16a...Incidence end surface of optical fiber 16 , 16b...Optical fiber 1
output end face of 6, 17... drive shaft of drive device 3;

Claims (1)

[Claims] 1 Emits the modulated radiation light from the light emitting section toward a reflector using a light transmitting optical system, and focuses the modulated light reflected from the reflector on the light receiving section using a light receiving optical system, so that the modulated radiation light In a light wave distance measuring device that measures distance based on a phase difference between the light beam and the reflected modulated light, a reflecting member is provided on the optical path between the light transmitting section and the light transmitting optical system, and is moved in and out according to the measurement light and the correction light. , by arranging a condensing optical system that condenses the correction light on the correction light optical path, the radiation modulation light having substantially the same radiation angle range as the measurement light is used as the correction light; A light wave ranging device characterized in that the influence of phase unevenness on the radiation angle of light is removed.