JPH01227916A - Three-dimensional optical distance sensor - Google Patents

Abstract

PURPOSE:To measure the surface of a body to be measured speedily in fine steps by varying the light emission wavelength of a semiconductor laser by utilizing the wavelength dispersibility of an optical device. CONSTITUTION:When a variable reference voltage generating means 19 varies the reference voltage of an APC (Automatic Power Control) circuit 18, the output of the APC circuit 18, i.e. the injecting current to a semiconductor laser 11 varies until the output voltage of a light emission power detector 17 becomes equal to the reference voltage, so that the light emission power of the semiconductor 11 varies. The light emission wavelength of the semiconductor laser 11 has light emission power dependency, so the light emission power also varies. The variation in the light emission wavelength causes variation in the projection angle of slit projection light from a shaping prism 13. Consequently, slit luminous flux is scanned at a high speed in fine steps without using a polarizing mirror nor a rotary encoder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a three-dimensional optical distance sensor that non-contactly measures steps on the surface of an object using light.

2. Description of the Related Art The structure of a conventional optical distance sensor will be described below with reference to the drawings. FIG. 5 is a configuration diagram of a conventional optical distance sensor. l
is a laser, 2 is a first deflection mirror that scans the beam in the X direction in the figure, 3 is a second deflection mirror that scans the beam in the X direction in the figure, 4 is the object to be measured, and 5 is the object to be measured A condensing lens condenses the reflected light from 4, and 6 a two-dimensional array photodetector placed behind the condensing lens.

Next, the principle of this conventional optical distance sensor will be explained with reference to FIG. In Fig. 6, S is the center of the condenser lens 5, L is the center of the beam emitted from the laser l, 0 is a point on the object to be measured 4, θ and φ are the reflected beams from each of the four points O, and the beam from the laser l is Let D be the angle that the outgoing beam of
If we set it as the length of , then the distance to point O is expressed by equation (1):
Formula (1).

Here, the angle e is the direction of the axis of the condenser lens 5, and is expressed by the formula (2
tane=f/d given by (2) f: Focal length of the condenser lens 5 d: Distance between the center of the condenser lens 5 and the beam detection point on the two-dimensional array photodetector. - and the first deflection mirror 2.3 (by which the laser beam is scanned in the X direction and the S, the center of the output beam, and the object to be measured 4
By extending equations (1) and (2) three-dimensionally between the point O above, three-dimensional distance measurement to the object to be measured 4 becomes possible.

Problems to be Solved by the Invention However, in the above configuration, the laser beam is
It is necessary to use deflection mirrors to scan in the X direction, and a rotary encoder is used as a detector to detect the angle for rotation 1i'1i3W of these deflection mirrors. is not only on the order of 0.01 degree, but also the response frequency of the r-direction mirror is on the order of only a few KH2. Therefore, it is difficult to measure the surface of the object to be measured at high speed and in minute steps. Met.

In view of these problems, the present invention makes use of the wavelength dispersion properties of optical elements and uses a means for changing the emission wavelength of a semiconductor laser, thereby making it possible to measure the surface of an object in three dimensions at high speed and in minute steps. The purpose is to provide an optical distance sensor.

Means for Solving the Problems The present invention provides a V-conductor laser, a condensing means for condensing light from the V-conductor laser into parallel light, and a slit-shaped light beam for directing the condensed laser light. A beam shaping means for converting the beam shape, an optical element having a wavelength dispersion property for reflecting or transmitting the light that has passed through one stage of beam shaping, and an optical element having a wavelength dispersion property arranged substantially in the same plane as the optical element having the wavelength dispersion property. This is a three-dimensional optical distance sensor characterized by being equipped with a two-dimensional photodetector and a means for changing the emission wavelength of a V-conductor laser.

Effect of the present invention With the above-described configuration, first, the elliptical emission beam of the semiconductor laser is made into a long and narrow slit shape by the beam shaping means, and then the emission wavelength of the semiconductor laser is varied to change the wavelength of the incident light to the optical element having wavelength dispersion. By changing the emission angle of the slit-shaped emitted light by wavelength dispersion, it is possible to scan the surface of the object to be measured as a plane, and it is possible to provide a three-dimensional optical distance sensor of fine step feeding and high-speed scanning type.

Example FIG. 1 is a plan view of a first embodiment of the invention.

11 is a semiconductor laser, 12 is a collimator lens that condenses the emitted light from the semiconductor laser into parallel light, and 13 is a shaper that reduces the short axis direction of the elliptical beam emitted from the collimator lens and shapes the beam into an elongated slit-shaped light. prism,
14 is an object to be measured onto which the light emitted from the shaping prism is projected, 15 is a condenser lens that collects the reflected light from the object to be measured 14, and 16 is arranged in substantially the same plane as the exit surface of the shaping prism. , the beam 11 focused by the focusing lens 15
17 is a light emission power detector that detects the light emission power of the semiconductor laser 11 from the back surface of the semiconductor laser 11; 18 is a light emission power detector that detects the light emission power of the semiconductor laser 110, and a variable reference voltage; The APC (Automatic Control) is constantly controlled by the generating means 19.
tic Power C0ntrO1) circuit.

The emission wavelength variable means 20 includes the emission power detector 17 described above.
, an APC circuit 18, and a variable reference voltage generating means 19.

The operation of the first embodiment of the present invention constructed as described above will be described below with reference to FIGS. 1 and 2. The variable reference voltage generating means 19 causes the APC circuit 1 to
When the reference voltage 8 is changed, the output of the APC circuit 18, that is, the current injected into the semiconductor laser 11, changes until the output voltage of the emission power detector 17 becomes equal to this reference voltage, and the emission power of the semiconductor laser 110 changes. do. Since the emission wavelength of the semiconductor laser 11 is dependent on the emission power, the emission power also changes.

Next, a change in the angle of emission of the light emitted from the shaping prism 13 due to a change in the emission wavelength will be explained using FIG. 2. The apex angle of the shaping prism 13 is α, the angle of incidence on the prism incidence surface is β, the refraction angle there is γ, and the exit angle from the prism is δ.
, the refractive index of the prism glass material is n. Snell's law holds true for each of the entrance and exit surfaces.Incidence surface: sinβ=1sin7''・Formula (3) Output surface: n5in(y+a)=sinδ...Formula (4) Here, the wavelength of the glass material Considering the variance, formulas (3) and (4
), then from equation (3), o=ci n S i n7+n COS
7d7-”” From equation (5) and equation (4), dnsin(r + a )+ncos(r + a
)dr = cosδdδ...Equation (6) From Equations (5) and (6), dδ=1/CoSδ(dnsin(r + a) −
ncos(r+a)dnsinδ/ncosδ) = 1/cosδ(sin(7+a)−cos(7
+a)tan7)dn)””
Equation (7) can be written as %Equation % Therefore, in the end, the change in the emission angle due to the change in the emission wavelength of the semiconductor laser U and the dispersion of the prism glass material is dδ=sin
adn/(cosδcosy) “”Formula (8) On the other hand,
The reduction rate M of the shaping prism is M=cosδcos 1 /(cosβcos(γ+α
) + 1Φφ formula (9)% formula % For example, here, 5FI is used as the glass material of the shaping prism 13.
If you choose I, then if the apex angle of the shaping prism 13 is α = 20 degrees and the incident angle β = 25 degrees, then γ = 14.77 degrees M 0.4 times δ = 72.02
degree dδ', o, os degree (input: 800na+->830
naw).

Generally, the ellipticity of the far-field pattern of a semiconductor laser is about 2 to 3, so the ellipticity of the light emitted from the shaping prism is 5 to 7.5, making it possible to form a slit-shaped light beam.

Furthermore, if the emission wavelength of the semiconductor laser 11 is changed by 30 nm by the emission wavelength variable means 20, the change in the emission angle due to the dispersion of the prism glass material will be dδ=0°08 degrees.
For example, if the distance between the exit surface of the shaping prism 13 and the surface of the object to be measured is 1 m, then approximately l.

A 4mm slit-shaped light beam can be scanned in the Y direction.

That is, it is possible to perform minute step feeding of about o-oot degrees per Inm of change in the emission wavelength of the semiconductor laser 11, and
A scanning range of several mm can be easily obtained.

Therefore, if the light emission wavelength variable means 20 and the shaping prism 13 configured as described above are used, a deflection mirror for deflecting the light beam in two directions, X and Y, and a rotary encoder for detecting the rotation angle thereof can be used. It becomes possible to scan the slit-shaped light beam in minute steps of about 0.001 degree at high speed without any problems.

Next, a second embodiment of the present invention will be described using FIG. 3.

Numbers 11 to 16 in the figure indicate the same parts as in FIG. Reference numeral 21 denotes a Peltier element that performs cooling or heating using an electric current, and is fixed to the semiconductor laser 11. A temperature detector 22 detects the temperature of the semiconductor laser 11. 23 is AT C (Auto+atic T
0 emission wavelength variable control circuit that controls the Peltier element drive current so that the output of the temperature detector 22, that is, the temperature of the semiconductor laser 11, becomes a constant wavelength by the voltage supplied from the variable reference voltage generation means 24. The means 20 includes a temperature detector 22 and a Peltier element 2.
1. ATC circuit 23 and variable reference voltage generation means 24
It is made up of.

Next, the operation of the second embodiment of the present invention will be explained using FIG. The emission wavelength of a semiconductor laser changes depending on the temperature. Therefore, the variable reference voltage generating means 24
By setting the base i (i voltage of 23) to control the driving current of the Bertier element 21, the temperature of the semiconductor laser 11 can be arbitrarily set, and the emission wavelength can be changed u7.

Therefore, similarly to the first embodiment of the present invention described above, the emission angle of the emitted light can be scanned in minute steps by utilizing the wavelength dispersion of the shaping prism 130. In addition, unlike the first embodiment of the present invention, since the light emitting power of the semiconductor laser 11 can be kept constant, there is also the advantage that there is no need for a means for correcting changes in the amount of light accompanying the light emitting power. There is.

Next, a second embodiment of the present invention will be described using FIG. 4. FIG. 4 is a configuration diagram of a guided waveguide laser called a distributed reflection laser (DBR laser) that has a diffraction grating inside a semiconductor laser.

The reflectance r and phase φl of the DBR region are 5inhγL and γcoshγL+(α+
j AB) sinh7L) =1γl exp (jΦ1) ...Formula (10)
% Formula %) A : Period of the diffraction grating : Coupling constant between light and diffraction grating α : I) BR region loss β : Propagation constant On the other hand, the phase φ2 of the light emitting region is φ2 = βaLa ``'' Equation (11) β31 Light emitting region Propagation constant [, a: length of light emitting region Such an optical waveguide laser needs to satisfy the phase matching condition for laser oscillation φ1−φ2+2mπ...Equation (12). That is, it emits light at a wavelength that satisfies this condition.

However, when current is injected into the DBR region, electrons and carriers are stored in the optical waveguide layer. When carriers are accumulated, the equivalent refractive index neq decreases due to the plasma effect. Therefore, according to the equation (10), Δβ=(2π/λ)neq−π/A changes, and φ1 also changes.

Therefore, the emission wavelength changes based on the phase matching condition of equation (12).

Therefore, if the emission wavelength variable means 20 is constituted by an optical waveguide type semiconductor laser having a diffraction grating therein and a means for controlling the injection current into the internal diffraction grating region, the above-mentioned first and second aspects of the present invention can be achieved. You can enjoy the same effects as in the example.

Furthermore, according to this embodiment, it is possible to integrate the emission power of the semiconductor laser, and not only eliminates the need for the Beltier element 21 and the temperature detector 22, but also significantly reduces the power required to drive the Peltier element 21. This has the advantage that power consumption can be reduced.

In the above embodiment, a triangular prism was used as a means for converting the beam into a slit-shaped beam, but the present invention is not limited to this, and for example, a slit-shaped aperture may be used, and an optical element having wavelength dispersion may be used to reflect the beam. A similar effect can be obtained by using a type or transmission type diffraction grating.

Effects of the Invention The three-dimensional sales distance sensor of the present invention includes a semiconductor laser, a beam shaping prism that reduces the beam width in the short axis direction of the elliptical far-field pattern of the semiconductor laser, and a beam shaping prism that is substantially coplanar with the exit surface of the shaping prism. By providing a two-dimensional photodetector placed inside the interior and a means for varying the emission wavelength of the semiconductor laser, a slit-shaped light beam can be transmitted in minute steps without using a deflection mirror or the like.
It is possible to provide a three-dimensional distance sensor that scans the surface of an object to be measured at high speed.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the first embodiment of the present invention, and FIG. 3 is a plan view of the second embodiment of the present invention. FIG. 4 is a block diagram of a guided waveguide type laser according to a third embodiment of the present invention, FIG. 5 is a block diagram of a conventional example, and FIG. 6 is an explanatory diagram of the operation of the conventional example. DESCRIPTION OF SYMBOLS 11... Semiconductor laser, 12... Collimating lens, 13... Shaping prism, 14... Measured object, 1
5... Condenser lens, 16... Two-dimensional array photodetector, 20... Semiconductor laser emission wavelength variable means. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1: 20 trillion Kuyu-cho location Figure 2: Figure 3: Head of light source Figure 5:

Claims (2)

[Claims] (1) A semiconductor laser, a condensing means for condensing the light from the semiconductor laser into parallel light, a beam shaping means for converting the beam shape of the condensed laser light into a slit-shaped beam, and this beam an optical element having wavelength dispersion that reflects or transmits the light that has passed through the shaping means; a two-dimensional photodetector disposed substantially in the same plane; and an emission wavelength of the semiconductor laser. A three-dimensional optical distance sensor comprising variable means. (2) Claim 1 characterized in that the beam shaping means and the optical element having wavelength dispersion are constituted by a beam shaping prism that reduces the beam width in the minor axis direction of the elliptical far-field image of the laser beam. The three-dimensional optical distance sensor described in .