JP2001124856A - Noise rate reducing method and laser range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise rate reducing method and a laser range finder. SOLUTION: This range finder is mainly constituted of a main body 31, a laser receiver 32 arranged inside the main body 31, a laser emitter 33, a telescope 34, an emission collimator lens 35, a receiving lens 36 and the like. The telescope 34 includes an objective lens 40, an eyepiece lens 50, and a prism lens 60 arranged between the objective lens 40 and the eyepiece lens 50. The emission collimator lens 35 uses the objective lens 40 and the prism lens 60 in common with the telescope 34. After a laser beam emitted from the laser emitter 33 is refracted by the prism lens 60, the beam is emitted to a target parallelly to the objective lens 40. The laser beam reflected and returned is focused on the laser receiver 32 via the receiving lens 36. The receiving lens 36 includes a non-spherical convex lens 361 and a concave lens 362.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reducing an optical noise rate, and more particularly to a method for reducing a noise rate of an instrument for measuring a distance and a laser range finder.

[0002]

2. Description of the Related Art Conventionally, a laser range finder (Las) based on a laser beam has been used among instruments for measuring a distance.
The er Range Finder has long been applied to measure the distance of distant objects or targets. Taking a laser range finder as an example, the basic method of measurement is a pulse of laser light (laserp).
ulse) toward the target, and at the same time, receives a laser light signal that is reflected back from the outside world by a light sensor (photosensor). Then, the time at which the laser light pulse was emitted is compared with the time at which the laser reflected light was received, and the time difference between the two is multiplied by the speed of light and divided by 2 to calculate the distance between the laser range finder and the target. Is done.

Usually, a laser range finder is formed from the following structure. Laser launcher (laser di
mode) emits laser light. Light detector (pho
The to-detector receives the reflected laser light. The emission collimator lens concentrates the laser light emitted from the laser emitter into one light beam and emits the light in parallel.

The above method reduces the phenomenon of dispersive emission by placing the laser emitter at the focal point of the launch collimator lens and providing a better exit path for the laser beam to exit in parallel. . In addition, a laser signal is received by focusing the laser light reflected by the receiving focusing lens. By the above method, a launching / receiving system can be configured.

[0005]

Conventional distance measuring instruments typically employ the same launch collimator lens and receive convergent lens to reduce manufacturing costs, thus reducing the image formed on the light sensor. Becomes equal to the dimensions of the laser launcher. However, because the area of a general light sensor is larger than that of a laser emitter, the image of the laser emitter projected on the light detector tends to occupy only a very small part of the light detector. For example, as shown in FIG. 1, the photosensitive area 11 of the light detector has a receiving area 12 and an image of a laser emitter (in a dark area), and the remaining area is a non-receiving area 13. For Laser Range Finder,
Since the portion for signal analysis determination is only a laser beam signal, all signals in the non-receiving area 13 are noise. Unfortunately, with conventional techniques, the area of the light detector is larger than the laser
The ratio between 2 and the non-receiving area 13 becomes relatively small.
That is, in the existing technology, the noise rate of the signal received by the light sensor is high, so that not only the difficulty of subsequent processing is increased, but also the performance of the distance measuring instrument is reduced.

Accordingly, it is a primary object of the present invention to provide a method and a laser range finder for reducing the noise rate of a distance measuring instrument. Another object of the present invention is to provide a telephoto lens.
es) to provide a method for reducing a noise rate and a laser range finder.

[0007]

In order to achieve the above-mentioned object, a main technique of the present invention is to enlarge an image projected by a laser emitter on a light sensor, and to increase a ratio of a reception area to a non-reception area. To reduce the noise rate.

When the image formed by the laser emitter on the light sensor is enlarged, for example, as shown in FIG. 2, the area occupied by the enlarged receiving area 22 in the light-sensitive area 11 of the light sensor is already present. It is larger than the technology reception area 12. On the other hand, the non-reception area 13 becomes the non-reception area 23 after being reduced, and changes as shown in FIG. Thereby, the ratio between the reception area and the non-reception area is improved. That is, the noise rate is reduced.

On the optics, there is a ratio relationship between the formed image and the focal length, so that the focal length of the emitting collimator lens is F1, the size of the laser emitter is D1, and the focal point of the receiving concentrated lens is F2. Assuming that the size of the received and formed image is D2, the relational expression between them is as follows. F1 / F2 = D1 / D2 → D2 = (F2 / F1) *
D1

Therefore, when the focal length of the reception focusing lens is increased, the image formed by the laser emitter is enlarged, and also serves the purpose of reducing the above-mentioned noise rate.

Normally, when the focal length is increased, the length of the laser range finder becomes longer to accommodate the lens. In order to reduce the volume of the laser range finder, the present invention further uses a combination of concave and convex lenses to reduce the volume.

Based on the above idea, the present invention provides a technique for reducing a noise rate by enlarging an image formed by a laser emitter. There is a receiving lens in the design of the art. Since the focal length is greater than the focal length of the launch collimator lens, the image formed by the laser emitter is magnified and the noise is reduced by causing the image to just fall within the light sensitive area of the light sensor.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 3, a laser range finder 30 according to an embodiment of the present invention mainly includes a main body 3.
1. A laser receiver 32, a laser emitter 33, a telescope 34, an emission collimator lens 35, a reception lens 36, and the like provided in a main body 31. Telescope 34
Are the objective lens 40, the eyepiece lens 50,
0 includes a prism lens 60 interposed therebetween. The launch collimator lens 35 includes the objective lens 40 and the prism lens 6.
0 is shared with the telescope 34. After the laser beam is emitted from the laser emitter 33 and refracted by the prism lens 60, the target (first
Inject to pass). The reflected laser light is focused on the laser receiver 32 via the receiving lens 36. The receiving lens 36 includes an aspheric convex lens 361 and a concave lens 362.

The laser emitter 33 emits a laser beam (or a non-visible light beam having an appropriate wavelength and usable in the present embodiment) to the measurement object, and the above-mentioned light beam is emitted from the surface of the measurement object. Comes back as soon as you reach.
The laser receiver 32 receives the folded laser beam, and after being connected to a predetermined electronic circuit (not shown), calculates a distance between the measurement object and the laser range finder 30. The telescope 34 is provided for receiving visible light (that is, light having a color that can be observed with the naked eye of the human eye) that the user can see from the measurement object with the eyes. You can check.

The optical path of the receiving lens 36 utilizes a telephoto lens design to save space in the assembly, as shown in FIG. In the optical design, light is concentrated inside by a convex lens 81 and is focused on a focal point 83 by dispersion and emission of a concave lens. FIG.
The effective focal length 84 can be longer than the actual assembly length 85. Thus, although the effective focal length 84 is equal to that of a convex lens, only a shorter space is required, which also serves the purpose of reducing the space of the assembly.

As can be seen from the calculation formula of the compound lens,
The smaller the focal length of the convex lens 81 is, the better the effect can be obtained. Therefore, in this embodiment shown in FIG. 3, the aspherical convex lens 361 is adopted to further reduce the space and further improve the resolution. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a reception screen of a conventional laser range finder.

FIG. 2 is a diagram illustrating a reception screen of a laser range finder according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating a laser range finder according to an embodiment of the present invention.

FIG. 4 is a side view showing a long distance lens of a laser range finder according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 Sensing range of photodetector 12 Receiving part 13 Non-reception area 22 Enlarged reception area 23 Reduced non-reception area 30 Laser range finder 31 Main body 32 Laser receiver 33 Laser emitter 34 Telescope 35 Emission collimator lens 36 Receiving lens Reference Signs List 40 Objective lens 50 Eyepiece 60 Prism 71 First pass 81 Convex lens 82 Concave lens 83 Focus 84 Effective focal length 85 Assembly length 361 Aspheric convex lens 362 Concave lens

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 13/18 G02B 13/18

Claims (6)

[Claims] 1. A method for reducing the noise rate of an instrument for measuring a distance, the method comprising: setting a focal length of a receiving lens larger than a focal length of an emitting collimator lens; A method for reducing noise rate, wherein the receiving area of the light sensing device is larger than the non-receiving area and smaller than or equal to the focal length of the emitting collimator lens. 2. The method according to claim 1, wherein the receiving lens includes a convex lens and a concave lens. 3. The method according to claim 2, wherein the convex lens is an aspheric convex lens. 4. A laser range finder capable of reducing a noise rate, comprising: a telescope, a laser emitter, a launch collimator lens, a reception lens, and a laser receiver, wherein a reception area of the laser receiver is reduced. The laser emitter, and the focal length of the receiving lens is greater than the focal point of the emitting collimator lens, the laser emitter, the image formation in the laser receiver is larger than the laser emitter, the laser receiver A laser range finder, wherein an upper receiving area is larger than a focal length of the receiving lens and smaller than or equal to a focal length of the emitting collimator lens. 5. The laser range finder according to claim 4, wherein said receiving lens includes a convex lens and a concave lens. 6. The laser range finder according to claim 5, wherein said convex lens is an aspheric convex lens.