JP2002202369A - Light signal detector and range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light signal detector and a range finder which can obtain a full detection efficiency even when a distance from the range finder to a target becomes large or a use environment (periphery of the target) changes. SOLUTION: The laser range finder 100 is provided with a semiconductor laser 112 for generating a laser light, a photodiode 122 for detecting the laser light reflected by the target 1, and a control circuit 160 for calculating the distance L on the basis of a time from the generation of the laser light to the detection of the reflected light. A diaphragm 123 having an aperture approximately similar to an emission shape of the laser light is arranged to a position nearly conjugate to the semiconductor laser 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal detecting device and a distance measuring device, and more particularly to an optical signal detecting device for detecting a pulsed laser beam emitted from a semiconductor laser and a distance measuring device using the same.

[0002]

2. Description of the Related Art Conventionally, there has been known an optical signal detection device for detecting a reception timing of a pulse signal transmitted at a predetermined timing. Such an optical signal detection device is used, for example, in a distance measuring device that irradiates a target object with laser light, receives reflected light thereof, and measures a distance to the target object.

In the distance measuring device, a time difference between the emission (transmission) of the laser beam and the reception of the reflected light is obtained by the count value of the clock pulse generated at a constant interval. The distance to the target is determined based on the speed of the laser light.

[0004]

In such a distance measuring apparatus, it is necessary to extend the measurable distance by reducing the influence of laser beam attenuation due to light scattering in the air. Is used.

[0005] Laser light generated and emitted from such a semiconductor laser is irradiated onto a target object while being spread and scattered, and a reflected signal thereof is detected by a photodiode 20 (FIG. 9). At this time, if the SN ratio at the time of detecting the reflected light is large, highly accurate measurement can be performed even over a long distance. However, the signal detected by the photodiode 20 includes not only the reflected signal light but also its background light (reflected light due to non-signal light from the background around the irradiation spot D2 in FIG. 8, self-emission, radiation, etc.). It mixes as disturbance noise (for example, the background light mixes as white noise). Since the disturbance noise does not decrease even when the measurement distance is increased, the influence of the disturbance noise is high in long-distance measurement. In particular, when the surroundings of the object 1 are bright, the influence of the above-described disturbance noise or the like becomes large, the S / N ratio of the detection signal of the photodiode 20 is reduced, and high-precision measurement over a long distance becomes difficult. There is.

In order to solve this problem, an interference filter or the like that absorbs components other than the oscillation wavelength of the semiconductor laser 10 (unnecessary components in the visible and infrared regions) is prepared, and the interference filter and the like are used. A method for removing disturbance noise is considered. However, in the method using the interference filter, if individual variations occur in the oscillation wavelength of the semiconductor laser 10, only the laser beam having the desired oscillation wavelength cannot be efficiently detected.

Further, in the semiconductor laser 10, the oscillation output may shift or the wavelength may shift due to temperature fluctuation. In consideration of the dynamic characteristics when the laser light is emitted in a pulse shape, disturbance noise is reduced. It was not practical to use an interference filter that limits the number of transmission wavelength bands to the nm level for removal. The present invention has been made in view of such circumstances, and it is possible to obtain sufficient detection performance even when the distance from a distance measuring device to a target object increases or the use environment (around the target object) changes. An object is to provide an optical signal detection device and a distance measuring device.

[0008]

According to an aspect of the present invention, there is provided an optical signal detecting apparatus for generating an optical signal, an optical signal generating section for detecting the optical signal, and an optical signal detecting section for detecting the optical signal. A stop having an opening corresponding to a signal emission shape, wherein the stop is arranged near a light receiving surface of the light detection unit.

According to a second aspect of the present invention, there is provided an optical signal generating section for generating an optical signal, and a light detecting section for detecting the optical signal, and a light receiving surface of the optical detecting section is adapted to emit the optical signal. It is shaped according to the shape.

According to a third aspect of the present invention, there is provided an emission section for emitting a pulsed laser beam toward an object, a laser beam detection section for detecting a pulsed laser beam reflected from the object, An aperture stop disposed near the light receiving surface of the laser light detector and having an opening substantially similar to the spot shape of the laser light; and the reflected pulsed laser light from the time when the pulsed laser light is irradiated. A time counting unit that counts the time until it is detected through the aperture, and a distance calculation unit that calculates the distance to the target based on the counted time and the speed of the pulsed laser light. It is provided with.

According to a fourth aspect of the present invention, there is provided an emission section for emitting a pulsed laser beam toward an object, a laser beam detection section for detecting a pulsed laser beam reflected from the object, A timer that counts the time from when the pulsed laser light is irradiated to when the reflected pulsed laser light is detected, and the counted time and the speed of the pulsed laser light. And a distance calculation unit for calculating a distance to the target object based on the distance, and a light receiving surface of the light detection unit is substantially similar to a spot shape of the laser light.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor has examined a high-power semiconductor laser and a light receiving surface of a light receiving element (for example, a photodiode) 20. A general semiconductor laser (small output laser) has an emission shape (beam shape) having an aspect ratio (an aspect ratio of an ellipse) of about 1: 1 to 1: 2. The shape of the exit surface of No. 10 (shape of D1) is elongated and the aspect ratio is 1: 100 to
1: As large as around 200 (FIG. 7).

The laser light from the semiconductor laser 10 is
Light is emitted toward the object 1 through an infinite optical system such as a collimator lens. At this time, the laser beam spreads to reach the target 1, and the irradiation spot D2
Becomes an elongated ellipse (FIG. 8).

The shape of the light reflected from the object 1 also becomes this elongated ellipse (shape indicated by D2), and after being converged by an imaging optical system such as a condensing lens, the light receiving element 20 shown in FIG. The light is incident on the light receiving surface 22 (an elongated ellipse indicated by D2 'in the figure). In general, the shape of the light receiving surface is
It is formed irrespective of the shape of 2 ′, for example, circular. Accordingly, the portion D2 'on the light receiving surface 22 in FIG. 9 receives the reflected signal light and the background light from the area of the irradiation spot D2 in FIG.

The portion of the light receiving surface 22 excluding D2 'receives background light from an area excluding the area of the irradiation spot D2 from (background) in FIG. The reception of the background light in the portion excluding D2 'lowers the SN ratio of the detection signal. This has not been noticed conventionally because the semiconductor laser light is invisible light. Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 9.

FIG. 1 is a perspective view of a laser distance measuring apparatus 100 to which the present invention is applied, and FIG. 2 is a block diagram showing the internal configuration thereof. As shown in FIG. 1, the laser distance measuring device 100 is provided with a power and measurement start button 101 and a mode change button 102 on the upper surface thereof. The mode change button 102 is used to change a unit of distance or the like. A laser irradiation window 103 and a laser receiving window 104 are provided on the front surface, and a finder window (not shown) is provided on the rear surface.

Inside the laser distance measuring apparatus 100, a collimating lens (infinity optical system) 1
Reference numeral 11 denotes a condenser lens (imaging optical system) 121 disposed on the laser receiving window 104 side. Also, the laser distance measuring device 10
A semiconductor laser (optical signal generation unit) 112 and a pulse generation circuit 130 are arranged inside the collimator lens 111 on the side of the collimator lens 111, and the laser light from the semiconductor laser 112 passes through the collimator lens 111 to the target 1. Irradiation is performed (FIG. 3). The emission section is constituted by the semiconductor laser 112, the collimator lens 111, and the like.

Also, a stop 123,
Photodiode (photodetector) 122, receiving circuit 150
Are arranged (FIG. 2). The condensing lens 121 and the photodiode 122 constitute a laser light detecting unit. The control circuit 160 causes the semiconductor laser 112 to emit laser light at a predetermined timing (light emission timing) based on the light emission start signal S1 output from the pulse generation circuit 130 described above.

On the other hand, the control circuit 160 detects the light receiving timing of the laser light reflected by the object 1 based on the signal S2 from the receiving circuit 150. As shown in FIG. 3, the control circuit 160 detects a time difference t between the light emission timing and the light reception timing by counting the number of clock pulses (function as a clock unit).

The control circuit 160 calculates a distance L from the laser distance measuring device 100 to the target 1 based on the counted time difference t and the speed of the laser beam (function as a distance calculation unit). . The control circuit 160 displays this calculation result on the liquid crystal display section 170 in the finder. By the way, in the present embodiment, as shown in FIG.
Reference numeral 23 is arranged between the condenser lens 121 and the photodiode 122 at a position conjugate with the emission surface of the semiconductor laser 112.

The slit (opening) 1 of the diaphragm 123
The shape E1 of 23A is the emission surface D1 of the semiconductor laser 112.
Is determined based on the shape (emission shape) of the laser beam and the infinity optical system (collimating lens 111), and is substantially similar to the shape of the laser beam irradiation spot D2 on the object 1 (FIG. 3). . By arranging the aperture 123,
Even if the distance L from the laser distance measuring device 100 to the target 1 increases and the laser beam spreads and the irradiation spot D2 increases, the SN ratio of the detection signal from the photodiode 122 can be increased.

This is because when the laser light from the semiconductor laser 1 is reflected by the object 1, the reflected light
Even if the signal component of disturbance noise due to background light (reflected light from the background, self-emission, radiation, etc.) from a portion other than 2 increases, the diaphragm 123 removes the component due to the disturbance noise. It is. By increasing the SN ratio when the reflected light is detected by the photodiode 122 by the function of the aperture 123, the distance that can be measured by the laser distance measuring apparatus 100 can be increased.

Further, even if the surroundings of the object 1 are bright, the influence of the disturbance noise and the like can be reduced by the stop 123, so that measurement over a long distance becomes possible. As described above, the laser distance measuring device 1 of the first embodiment
In 00, since the stop 123 is disposed near the photodiode 122, the irradiation spot (D2) of the target 1
Disturbance noise due to background light from the surroundings can be reduced, and the S / N ratio can be increased. As a result, the laser ranging device 100
Accordingly, the distance to the target 1 that can be measured can be increased.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. In the laser distance measuring apparatus according to the second embodiment, instead of disposing the stop 123 according to the first embodiment, the shape of the light receiving surface 202 of the photodiode 222 is substantially the same as the shape of the irradiation spot D2 of the laser light. It is similar. The shape of the irradiation spot D2 depends on the emission shape of the photodiode 122 (the shape of D1) and the infinity optical system (the collimator lens 11).
1 etc.).

The laser range finder of the second embodiment does not have the stop 123 and the photodiode 122
Except that a photodiode 222 is used in place of the laser distance measuring apparatus 10 of the first embodiment.
The configuration is the same as 0, and a detailed description thereof will be omitted. As shown in FIG. 6, the photodiode 222 used in the laser distance measuring apparatus of the second embodiment
01 so as to cover the pn junction surface (light receiving portion)
A light-shielding film 223 having an opening (shape of D2 ′) substantially similar to the shape of the irradiation spot D2 is formed, and the light-receiving surface 202 is formed.
Are formed.

By making the light receiving surface 202 substantially similar to the shape of the irradiation spot D2, the distance L from the laser distance measuring device 100 to the object 1 is increased as in the case of the first embodiment. Therefore, even if the irradiation spot D2 becomes large, the SN ratio of the detection signal from the photodiode 122 can be increased. As described above, when the SN ratio at the time of detecting the reflected light by the photodiode 122 increases, the measurable distance increases. Further, even when the periphery of the object 1 is bright, long distance measurement by the laser distance measuring device becomes possible.

In the above-described first and second embodiments, an example in which the present invention is applied to the laser distance measuring apparatus 100 has been described. However, the present invention can be applied to measuring equipment using other measuring waves. Is applicable.

[0028]

As described above, according to the first aspect of the present invention, since the stop having the aperture corresponding to the emission shape of the optical signal is arranged near the light receiving surface of the light detecting section, Even if the distance between the signal generation unit and the light detection unit is long and the intensity of the received light signal is reduced, the reduction in the SN ratio can be suppressed.

According to the second aspect of the present invention, the light receiving surface is
Since the shape is in accordance with the emission shape of the optical signal, even if the distance between the optical signal generation unit and the light detection unit is long and the intensity of the received light signal is reduced, the reduction in the SN ratio can be suppressed.

According to the third aspect of the present invention, in the distance measuring apparatus, the diaphragm having an aperture substantially similar to the spot shape of the laser beam on the object is arranged near the light receiving surface of the laser beam detector. Therefore, when detecting the reflected light from the object, even if the spot shape of the reflected light widens, the disturbance noise can be reduced, the SN ratio can be increased, and the distance to the measurable object can be increased. Can be longer.

According to the fourth aspect of the present invention, in the distance measuring device, the shape of the light receiving surface of the laser beam detecting portion is substantially similar to the spot shape of the laser beam on the target, so that the distance from the target is small. When detecting the reflected light, even if the spot shape of the reflected light is widened, disturbance noise can be reduced, the S / N ratio can be increased, and the distance to the target that can be measured can be increased.

[Brief description of the drawings]

FIG. 1 is a perspective view of a laser distance measuring apparatus 100 to which the present invention is applied.

FIG. 2 is a block diagram showing an internal configuration of the laser distance measuring apparatus 100.

FIG. 3 is a timing chart showing how light reception timing is measured when obtaining a distance L to an object 1.

FIG. 4 is a diagram showing a relationship between a semiconductor laser 112 and an object 1;

FIG. 5 is a perspective view showing a diaphragm 123;

FIG. 6 is a perspective view showing a photodiode 222 in which a light-shielding film having an elliptical opening is formed on a light receiving surface.

FIG. 7 is a perspective view showing a high-power semiconductor laser 10;

FIG. 8 is a diagram showing an irradiation spot of a high-power semiconductor laser.

FIG. 9 is a perspective view showing a conventional photodiode 20.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Object 100 Laser distance measuring device 111 Collimating lens (infinity optical system) 112 Semiconductor laser (optical signal generation part) 121 Condensing lens (imaging optical system) 122 Photodiode (light detection part) 160 Control circuit (time measurement part) , Distance calculation section) 170 Liquid crystal display section

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 3/00 H01L 31/02 BF Term (Reference) 2F065 AA06 DD04 FF12 GG06 GG12 HH04 JJ01 JJ18 LL30 UU02 2F112 AD01 BA01 BA07 CA06 CA12 DA25 EA05 FA14 5F072 AB13 KK30 SS06 YY13 5F088 AA02 BB06 JA05 JA11 5J084 AD01 BA04 BA36 BB02 BB04 BB37 CA03 DA01 EA02 EA07

Claims (4)

[Claims] 1. An optical signal generating unit for generating an optical signal, a light detecting unit for detecting the optical signal, and a stop having an opening corresponding to an emission shape of the optical signal, wherein the stop includes the light An optical signal detection device disposed near a light receiving surface of a detection unit. 2. An optical signal generating section for generating an optical signal; and a light detecting section for detecting the optical signal, wherein a light receiving surface of the light detecting section has a shape corresponding to an emission shape of the optical signal. An optical signal detection device, comprising: 3. An emission unit for emitting a pulsed laser beam toward an object, a laser beam detection unit for detecting a pulsed laser beam reflected from the object, and light reception of the laser beam detection unit A stop disposed in the vicinity of the surface and having an opening substantially similar to the spot shape of the laser light, and the reflected pulsed laser light from the point in time when the pulsed laser light is irradiated is transmitted through the stop. A time counting unit that counts time until detection, and a distance calculation unit that calculates a distance to the target object based on the counted time and the speed of the pulsed laser light. Characteristic ranging device. 4. An emission unit for emitting a pulsed laser beam toward an object, a laser beam detection unit for detecting a pulsed laser beam reflected from the object, and the pulsed laser beam. A timer that counts the time from the point of irradiation until the reflected pulsed laser light is detected, and up to the target object based on the counted time and the speed of the pulsed laser light. A distance calculating unit for calculating a distance of the laser beam, wherein a light receiving surface of the light detecting unit is substantially similar to a spot shape of the laser light.