JPS5855470B2 - Phase unevenness mixing homogenization device for light wave ranging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase unevenness mixing and homogenizing device in a light wave distance measuring device.

A modulation signal is given to a light emitting element such as a light emitting diode to generate emitted modulated light, this emitted modulated light is reflected by a reflector such as a corner cube, the reflected modulated light is received by a light receiving element, and the emitted modulated light and the reflected light are reflected. A light wave distance measuring device that measures distance based on a phase difference with modulated light is well known.

Incidentally, the modulated light emitted from the light emitting diode generally includes positional fluctuation and angular phase irregularity.

Here, the positional phase unevenness means that modulated light with different phases is emitted depending on the light emitting position of the light emitting diode.
On the other hand, angular phase unevenness occurs due to the thickness of the light emitting part of the light emitting diode, and
This means that modulated light having different phases is emitted depending on the emitting direction.

In addition, when a light-wave ranging device is configured with a light-emitting diode with phase unevenness and the distance is measured by the light-wave ranging device, the emitted light with the phase unevenness is emitted from the objective lens of the light-wave ranging device. As a result, even if the same distance is measured, a phase difference occurs in the reflected light, resulting in variations in measured distance values and measurement errors.

A conventionally proposed method to solve this problem of phase unevenness is to pass the modulated light from the light emitting element through a glass rod closely attached to the light emitting element, and to achieve phase mixing by repeatedly reflecting the modulated light within the glass rod. How to do it (% Kosho 52-
32260), a method of performing phase mixing by passing modulated light through irregularly intersecting optical guides, a method of inserting a condensing lens in front of the light emitting surface and performing phase mixing using the Kohler illumination method, and a method of performing phase mixing by passing modulated light through optical guides that intersect irregularly. There are methods such as passing the image through a multi-lens.

However, the method of closely adhering glass rods is difficult to manufacture and increases the manufacturing cost of the light emitting device, and the method of passing the modulated light through irregularly interlaced optical guides is difficult to obtain sufficiently effective phase unevenness mixing. For this purpose, an optical element with a diameter of several microns or less is required, and since it is almost impossible to manufacture such an optical element with current technology, it is considered impossible to mix and homogenize the phase unevenness using this type of optical guide. It was considered.

Furthermore, the method using Koehler illumination generally has the problem that the magnification of Koehler illumination, that is, the ratio of the element area to the diameter of the objective lens cannot be maintained sufficiently, and the method using multiple lenses has the problem that there is a large loss of light quantity. There are problems in that it is difficult to obtain uniformity of the multi-lens, and phase unevenness occurs in all directions, making it difficult to quantitatively control the phase unevenness.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide a more effective phase unevenness mixing homogenization device. It has a lens means for focusing the modulated light flux emitted from the light emitting element, and a bent optical fiber having an end face at the focal position, and the modulated light emitted from the optical fiber is focused at the other end of the optical fiber. The structure is such that the light is emitted from the reflector toward the reflector.

Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. In FIG. 1, modulated light from a light emitting element 1 is transmitted through a relay lens 2.
Incident plane A of optical fiber 3 bent through
The image is projected onto the image.

Anti-reflection plate 4 made of a transparent plate with a refractive index that is the same as or close to the refractive index of the optical fiber 3.
5 are bonded to both ends of the optical fiber 3 with an adhesive.

It is desirable that this adhesive also has a refractive index that is the same as or close to the refractive index of the optical fiber 3.

The exit side end of the optical fiber 3 is arranged to face the objective lens 6, and the light beam emitted from the optical fiber 3 is turned into a parallel light beam by the objective lens 6, and travels toward a reflector (not shown).

Next, the effect of mixing and homogenizing the phase unevenness of the light emitting element 1 in the above configuration will be explained.

First, when there is a space between the light emitting element 1 which has phase unevenness due to position and the input end A of the optical fiber 3, the angle that occurs at the input end A due to the phase unevenness due to the position of the light emitting element is This prevents phase unevenness from occurring.

That is, by forming the light emitting part image of the light emitting element 10 onto the input end A of the optical fiber 3 by the relay lens 2 and using this end surface as a secondary light source, phase unevenness due to the above-mentioned angle does not occur.

Here, FIG. 1 shows an example in which the light emitting part image of the light emitting element 10 is imaged onto the input end A of the optical fiber 3 by the relay lens 2. It may be placed near the image formation position at a position where the modulated light emitted from the light emitting element 1 is focused by the relay lens 2.

That is, if the input end A of the optical fiber 3 is placed at a position where the modulated light emitted from the light emitting element 1 is focused,
This is because a sufficient amount of light can be ensured, and since various output modulated lights enter the optical fiber 3, the input end can be regarded as a secondary light source, and phase unevenness due to angle does not occur.

Note that nothing is attached to the light emitting element 1 in close contact with the light emitting element 1, and the manufacturing price of the light emitting element 1 is, of course, the same as in the past.

Second, the occurrence of phase unevenness due to angle within the mixing homogenization member is prevented.

When the mixing homogenizing member is not bent as in the prior art described above, as shown in Fig. 2, the optical path length is different between the normal incident light velocity that travels straight through the member and the oblique incident light velocity that repeats reflections on the side surfaces. Differently, this optical path length difference is approximately 4.5 mm when the optical fiber length is 30 degrees and the incident angle is 30 degrees.
becomes.

As a result, this optical path length difference causes angular phase unevenness at the exit end even when a light beam from a light emitting element that has no phase unevenness due to angle or position is incident on the optical fiber.

However, in the configuration of the present invention, the optical fiber serving as the mixing and homogenizing member is bent and arranged to prevent phase unevenness due to angle at the injection end of the mixing and homogenizing member.

Thirdly, the phase unevenness caused by the angle and position of the light emitting element is also eliminated by repeating reflection within the bent optical fiber to homogenize the mixture.

Further, the antireflection plates 4 and 5 have the effect of shifting the reflection surfaces at the input end and the exit end of the doublet fiber 3 from the imaging position, and have the effect of preventing the generation of noise due to stray light.

In addition, by applying an anti-reflection coating to the incident end and exit end of the optical fiber 3 in addition to the above-mentioned reflector,
It is also possible to reduce the reflected light at the end facets and prevent the generation of noise due to stray light.

Optical fiber 3a according to another embodiment of the present invention,
3b is arranged with its entrance end and exit end eccentrically or deflected from each other, as shown in FIGS. 3 and 4.

By decentering or deflecting the input end and exit end of the optical fiber in this way, the light emitting element and objective lens can be placed in any position, making the device more compact, easier to assemble, and the light emitting element and light receiving element It has structural design benefits such as prevention of induction between

As described above, the present invention can effectively prevent and eliminate phase unevenness generated from the light emitting element and the mixing homogenizer, and greatly contributes to improving the measurement accuracy of the optical distance measuring device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing reflection of light within an optical fiber,
FIG. 3 and FIG. 4 are schematic diagrams showing other embodiments of the optical fiber. 1...Light emitting element, 2...Relay lens, 3...Optical fiber 4,5...
...Anti-reflection plate, 6...Objective lens.

Claims (1)

[Scope of Claims] 1 Optical wave measurement in which emitted modulated light from a light emitting element is reflected by a reflector, the reflected modulated light is received by a light receiving element, and distance is measured based on the phase difference between the emitted modulated light and the reflected modulated light. The distance device includes a lens means for condensing the modulated light emitted from the light emitting element, and a bent optical fiber having an end face at the condensing position, and the lens means condenses the modulated light emitted from the optical fiber. A mixing homogenizer in a light wave distance measuring device, characterized in that the optical fiber is configured to emit light from the other end of the optical fiber toward the reflector. 2. Claim 1, characterized in that the end face of the optical fiber is coated with an anti-reflection coating.
A phase unevenness mixing and homogenizing device for the optical distance measuring device described in 2.