JPH0448210A - Optical distance sensor - Google Patents

Abstract

PURPOSE:To improve the measurement accuracy by forming images on plural array type optical converting elements individually with reflected light from one light source and calculating distance by a triangulation system which uses the current ratio of currents outputted by said elements. CONSTITUTION:Although one light projection part 2 is provided, photodetection parts 41 and 42 of the same specification are arranged symmetrically about the light projection part 2 and the reflected light from an object body is received by photodetection lenses 141 and 142 which are arranged at a distance B from the luminous flux to form the images on liner type position detecting elements (PSD) 181 and 182 which are arranged at a distance of the focal length of the photodetection lenses 141 and 142. The photodetection parts 41 and 42 calculate the ratios IN/IF of currents IN outputted from electrodes of the PSDs 181 and 182 close to the luminous flux and currents IF outputted from far-side electrodes, and the distance Z between the object body and photodetection lenses 141 and 142 is calculated by an arithmetic part 24 from an equation. Here, (n) is the number of the photodetection parts and L is the length of the photodetection parts. Consequently, the distance and its variation can be measured accurately with high precision.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical distance sensor.

[Prior Art] Unmanned underwater vehicles (hereinafter referred to as AUVs) that navigate under the sea have been developed since they are useful for various exploration purposes and underwater robot work purposes. This AU
When controlling the navigation of a V, when approaching a target object from an AUV, or when controlling navigation close to an obstacle such as the ocean floor, it is necessary to accurately determine the distance from close-range image information of the target object. It is extremely important to measure this.

As described above, various means for measuring the distance to a target object at a relatively short distance by remote measurement from an observation position have been developed in the past.

Some of these measurement methods use ultrasonic waves, but when multiple distance sensors are used, there is a risk of malfunction due to mutual interference, and it is difficult to measure the distance to the sea floor where sludge has accumulated or seaweed has grown. In this case, distance measurement using sound waves will have a large error. On the other hand, optical means have the advantage of easily eliminating the interference problem and the influence of the surface condition of the target object, and therefore various optical distance measuring means have been developed.

A conventional measurement method using optical means and applying the principle of triangulation will be explained below with reference to FIG. In the figure, the distance sensor 1 has a light projecting section 2 and a light receiving section 4, and the light projecting section 2 consists of a light projecting device 6 and a light projecting lens 8.

The light projecting device 6 is generally composed of a light emitting diode, a semiconductor laser element, etc., and emits light from the projecting device 6 into a parallel light beam 10 toward the target object 12 by a projecting lens 8 . Further, the light receiving section 4 includes a light receiving lens 14 and a linear position detection element (hereinafter referred to as PSD) 16. The PSD 16 is placed at a position away from the light receiving lens 14 by a focal length F, so that the reflected light 18 of the target object 12 is
The image is formed on the D16.

The PSD 16 is an array type element in which electrodes E, E, are attached to both ends of a long and narrow semiconductor photoelectric conversion element 18.

When the spot light hits the photoelectric conversion element 18 having a length L, the electrodes EN and EF move to the electrodes EN at both ends from the spot light incident position.

Distance to Er (X)t, current IN inversely proportional to Xy.

Output I y (IN/IF=X y/X N).

Therefore, from the principle of triangulation, the distance Z between the lens 8.14 and the target object 12 is as follows. Therefore, the distance can be automatically determined by using an electronic device, and it has been conventionally used as an automatic focusing sensor in a camera or a positioning sensor in a production line.

However, the above-mentioned means has a drawback in that the larger the displacement of the target object, the worse the accuracy in measuring the amount of displacement becomes. Furthermore, there are other problems, such as the fact that the refractive index of the air changes due to local temperature changes, the optical system gets dirty with oil or dust, etc., and is easily affected by the environment, and it cannot be applied when the target object is a mirror surface.

[Problem to be solved by the invention]

Therefore, in order to accurately measure the amount of displacement, a beam of laser light is irradiated from two locations onto the same location on the target object at the same angle of incidence, and the change in reflected light that occurs when the surface of the target object is displaced. Unexamined Japanese Patent Application Publication No. 4
There is a prior art of Publication No. 7-19846. The reflected light change detector described in this publication uses a photoelectric converter placed inside a rotating drum provided with slits.

That is, a laser beam irradiated from two places to one point is observed as two reflected lights from the object toward the detector. Next, when the reflection position is displaced, the light emitted from the two places will illuminate different positions, so the reflection position will be separated into two places. Therefore, since the photoelectric converter outputs a current when the slit of the rotating drum captures reflected light from either of the two places, the larger the displacement, the wider the output time interval of the current. Therefore, displacement can be measured from the time difference.

As can be seen from the above explanation, the prior art of the above-mentioned publication does not allow the AU to change the distance significantly even when passing through a small displacement, such as when measuring the height of an object running on a heald.
It cannot be used as an optical distance measuring device installed in V.

The present invention has been made focusing on the above problems,
By using optical triangulation means, it is possible to accurately measure distances and their changes with high accuracy even when distance changes are large within the measurable range.
The purpose is to provide an optical distance sensor that can be mounted on a UV.

(Means for Solving the Problems) The configuration of the optical distance sensor of the present invention for achieving the above object includes a light projecting section that emits a luminous flux toward a target object;
A light receiver that receives reflected light from a target object by a light receiving lens placed at a distance B from the light beam, and forms an image on a linear position detection element placed at a focal length F of the light receiving lens. A plurality of light receiving parts are provided, and each light receiving part is determined by the ratio I, /I, of the current IN output from the electrode on the side closer to the light beam of the linear position detection element and the current ■ output from the electrode on the far side. The distance Z between the target object and the light-receiving lens is determined by the following formula, where n represents the number of light-receiving parts.

This is equipped with an arithmetic unit that calculates from.

The optical distance sensor can be used both in the air and underwater.

When the number n of light receiving sections is 3 or more, the optical distance sensor of the present invention can be formed, for example, by arranging the light receiving sections radially around the light source.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical distance sensor of the present invention will be described in detail below by way of an embodiment with reference to the accompanying drawings.

FIG. 1 is a schematic explanatory diagram of the optical distance sensor of this embodiment. In the figure, the optical distance sensor 1 has one light projecting section 2, but two light receiving sections 41.4□ having the same specifications are arranged symmetrically with respect to the light projecting section 2. The light projecting unit 2 consists of a light projecting device 6 that emits one beam of green laser light and a light projecting window 8' made of optical glass.The light projecting unit 2 includes a light receiving lens 14 and a light receiving lens 14, respectively, located at a distance B from the optical axis of the light projecting device 6. , 14□
Place. PSD16. ．． 16□ is the light receiving lens 14□, 14! The lens was placed at a position separated by the focal length F of the lens.

PSD18. The current I N output from the electrodes ENI and E□ of
I+ I FI+ I N! , I vz amplifier 2
0, amplified and converted into a digital signal by the A/D converter 22, and then provided to the arithmetic unit 24. The calculation unit 24 performs calculations according to the following equation, and provides a signal of distance Z to the display 26.

4. Therefore, according to the present invention, it is possible to measure more accurately and with higher precision than the conventional optical distance sensor, and by arranging the unit light receiving parts radially around the light source, it is compact. Moreover, it is possible to provide a surveying instrument that is accurate and has high precision. Therefore, it is possible to install it in an AUV with a large change in measurement distance.

(Effects of the Invention) As explained above, the optical distance sensor of the present invention focuses the reflected light from one light source on a plurality of array two-light conversion elements separately, and converts the current output from these elements into two images. Since the averaged distance is calculated by a triangulation method using a ratio, it is possible to obtain the effect of being able to accurately measure and improve measurement precision compared to the conventional method with a relatively simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an optical distance sensor according to an embodiment, and FIG. 2 is a schematic explanatory diagram of a conventional optical distance sensor. 1... Optical distance sensor, 2... Light projecting section, 4, 4.
. 4□... Light receiving unit, 6... Light emitter, lO... Luminous flux, 12... Target object, 14, 14. ．． 14□... Light receiving lens, 16... Linear type light conversion element (PSD)
, 18...Reflected light, 24... Arithmetic unit.

Claims (1)

[Scope of Claims] A light projector that emits a light beam toward a target object, and a light receiving lens that receives the reflected light from the target object at a distance B from the light beam, and the focal length of the light receiving lens is A plurality of light receivers are provided to form an image on a linear position detecting element arranged at a distance F, and each light receiving part is outputted from an electrode of the linear position detecting element on the side closer to the luminous flux.
The ratio I_ of _N and the current I_F output from the far side electrode
Determine N/I_F for each light receiving part, and calculate the distance Z between the target object and the light receiving lens using the following formula, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ where n is the number of light receiving parts, and L is the number of light receiving parts. Each represents the length. Optical distance sensor equipped with a calculation unit that calculates from