JPH074909A - Laser sensor apparatus - Google Patents

Abstract

PURPOSE:To use a plurality of laser sensors continuously at the same time at a close position by making the wavelengths of the emitted lights from laser light source elements deffer from each other, and providing spectroscopic filters having the function for shielding the light having the wavelength emitted from the other laser light source element in the incident light source of a photodetector. CONSTITUTION:The diameter of a laser beam 11 emitted from a laser light source element 1 of a laser sensor 10 is narrowed by a projecting lens 3. Then, the light is projected on a surface to be inspected 30 as the spot light. The image of the light is focused on the detecting surface of a position-detecting type detector 6 through an interference filter FL1 and a condenser lens 5. Meanwhile, the diameter of a laser beam 21 emitted from a semiconductor laser 1' of a laser sensor 20 is narrowed by a projected lens 3'. The light is projected on a surface to be inspected 40 as the spot light. The image of the light is focused on the detecting surface of a detector 6' through a filter FL2 and a condenser lens 5'. A step difference D or fluctuation is detected based on the difference output of the signals of the surfaces 30 and 40 generated in the sensors 10 and 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates an object with two or more laser beams from an optical sensor device having a laser light source, and detects each reflected light by a position detection type detector (PSD). ) Or the like, the present invention relates to an optical sensor device of a type that obtains data representing a positional relationship between a surface of an object and a sensor in a non-contact manner by detecting it with a light detecting means.

The technical fields in which the optical sensor device according to the present invention is used are displacement measurement of objects such as various works,
There are surface shape sensing, thickness measurement of a plate-like object (particularly, a transparent object), and the like.

[0003]

2. Description of the Related Art In recent years, laser diodes (hereinafter referred to as LD
Say ) Projects light from a laser light source such as
An optical displacement measuring device that detects the reflected light with a light detection device and calculates the position, surface shape, thickness of the object or changes in them based on the detection result is used for automation of factory production lines, automatic machine It is used in a wide variety of fields such as operation control and condition monitoring of various objects.

FIG. 1 is a schematic diagram of a conventional laser sensor device. To explain this, the light from the LD 1 is generated by the collimator lens 2 provided as necessary.
Are collimated by the projection lens 3, the beam diameter is narrowed by the projection lens 3, and projected onto the object 4 to be inspected as spot light. This projection spot light image is made incident on the detection surface of a position detection type photodetector (hereinafter referred to as PSD) 6 as a detection spot image via a condenser lens 5. When the position of the test object 4 is displaced along the optical axis of the incident light (P → P ′), the detection spot image also moves on the PSD (Q → Q ′).

The PSD 6 having a position detecting function generates two current outputs I1 and I2 according to the incident position of the spot light, and I12 = (I1−I2) / (I1 + I2
) Represents the incident position on the PSD. Therefore, the respective current outputs I1 and I2 are converted into voltage V1 and
Converted to V2 and calculated by calculator 9 Δ12 = (V1-V
By performing 2) / (V1 + V2), the position of the detected spot light can be known, and the position of the object 4 to be inspected (the position of the projected spot light) can be obtained based on it. In the figure, the positional displacement of the object 4 to be inspected is shown by translational movement (solid line → broken line), but the positional displacement (spot light incident position) due to the posture change of the object to be inspected may be measured.

Further, a laser light source element such as an LD usually used in such an optical position displacement measuring apparatus has a monitor light detector 9 for monitoring output light intensity of the light source built-in or attached. , The light source drive circuit LD via the controller CTL based on the output of the monitor photodetector 9.
Control of D is performed to keep the output light intensity of the light source element (LD) 1 constant. In order to avoid the influence of the return light from the object 4 to the LD element 1, a beam splitter is arranged between the LD 1 and the object 4 and the light emitted from the LD 1 is monitored on the side of the beam splitter. In some cases.

Such a laser sensor uses each sensor individually or at a position sufficiently separated from each other,
There is a case where two or more sensors are used simultaneously at positions close to each other. An example of the latter usage is (1)
Detection of surface shape-related amount such as step and surface direction or its change amount (2) Detection of thickness of plate-shaped or web-shaped object, (3)
Simultaneous position detection of a plurality of close objects can be considered. Figure 2
FIGS. 3A and 3B and FIGS. 3A and 3B exemplify the relationship between the laser sensor, the laser beam, and the test object in these cases.

In FIG. 2A, laser sensors 10 and 2 are shown.
The laser beams 11 and 21 from 0 are incident on the surfaces 30 and 40 at the positions 12 and 22, and the step D between the surfaces 30 and 40 is measured from the Z direction position data of the respective incident positions 12 and 22. In FIG. 2B, the laser beam from each of the sensors 10 and 20 is incident on the vicinity of the tip of the triangular ridge portion 50, and the angle θ of the ridge portion 50 is measured. In addition, FIG.
, The sensors 10, 2, from both sides of the plate-like object 60.
An arrangement is shown in which laser beams 11 and 21 from 0 are incident on the front and back corresponding points 12 and 22 and the thickness of the plate-like object 60 is measured. Further, FIG. 3B shows an example in which the heights h1 and h2 of two columnar objects 70 and 80 located close to each other on the same plane G are measured by the same arrangement. In addition to this, there may be a case where two or more laser sensors are used in close proximity in various situations.

When two or more laser sensors are used in such a state, since the incident positions of the laser beams are close to each other, an irradiation spot formed by a laser beam emitted from another laser sensor is detected. Phenomenon or the light that is multiple-reflected in the peripheral part becomes ambient light and enters the photodetector (PSD) through the condenser lens provided in the photodetection section of the adjacent sensor. Was there. In the thickness measurement shown in FIG. 3A, this phenomenon occurs especially when the plate-shaped or web-shaped object 60 has a light-transmitting property.

When such an interference phenomenon occurs between the sensors, of course, noise accompanies the output of the position detection type detector of the sensor, and the measurement accuracy is remarkably lowered. In some cases, it is practically impossible to measure. FIG. 4 is a diagram showing an example of actual measurement of the detection output when the interference phenomenon occurs. In FIG. 4, the horizontal axis t is the time, and the vertical axis Z is the axis representing the spot light image forming position on the PSD. The vertical scale 1 scale corresponds to 10 μm, and the 830 nm laser light source element (GaAlAs) used for another laser sensor in proximity to the photodetection part of the laser sensor having the 780 nm laser light source element (GaAlAs semiconductor laser). The interference phenomenon that occurs when light from a semiconductor laser) enters as disturbance light is illustrated.

That is, when an ideal measurement without interference is performed in a state where the object is not displaced, the detection output gives a straight line graph of Z = Z0 (constant value). This should be the case (see Examples below). However, in the example shown in FIG. 4, the width (several hundred μ
It can be seen that a pulsatile detection output with m) is produced.

Conventionally, the method that has been adopted as a measure for avoiding such an interference phenomenon is to turn off the LD light source of the laser sensor in the vicinity of a certain sensor during the measurement period. The state is set to a weak light emission state. However, once the LD light source is put into the extinction state or the faint light emission state, it takes some time (for example, several ms) to return to the stable measurable state again.
It becomes difficult to obtain a measurement output from each laser sensor at a repetition frequency of 1 kHz or higher. Further, from the point of view that the control circuit means for accurately shifting the light emission phase of the plurality of laser light source elements, the circuit means for extracting the detection output during the light emission phase, etc. are required, this conventional It cannot be said that the method was satisfactory.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser sensor device capable of preventing mutual interference between a plurality of laser sensor means. That is, according to the present invention, in a laser sensor device using a plurality of laser sensor means, by interrupting the disturbance light originating from the laser light source of another laser sensor means, another laser sensor means can perform another measurement while performing measurement. This eliminates the need to set the laser light source of the laser sensor means to the extinction state or the slight light emission state.

[0014]

The present invention is directed to a laser light source element, an optical system for making the output light of the laser light source element incident on an object to be inspected, a position detection type photodetector, and the position detection type. In a laser sensor device comprising a plurality of laser sensor means having an optical system for making reflected light from the object to be detected incident on a photodetector, in the laser light source element belonging to each of the plurality of laser sensor means. The emission wavelength characteristics are made different from each other, and the spectral filter means having a function of blocking the light of the emission wavelength of the laser light source belonging to another laser sensor means is arranged in the optical path of incidence to the photodetector of each laser sensor means. By doing so, a laser sensor device without mutual interference is realized.

[0015]

In the laser sensor device of the present invention, the emission wavelength characteristics of the laser light source elements belonging to the respective laser sensor means are made different, and then the laser light source element in each laser sensor means is provided in the incident optical path of the photodetector (PSD). Since spectral filter means having a function of effectively blocking light of a wavelength emitted from a laser light source element belonging to another laser sensor is arranged, even if two or more laser sensors are used at the same time, It is possible to prevent the light emitted from the laser light source element belonging to the laser sensor of (1) from entering the photodetector (PSD) of itself via the target object or the peripheral object. Therefore, as in the conventional case, it is possible to continuously use two or more laser sensors at a close position simultaneously without fear of deterioration of measurement accuracy or unmeasurable state caused by incidence of ambient light.

Further, at that time, it is not necessary to stop the light emission of the laser light source element belonging to another laser sensor or reduce the light emission state to a weak light emission state during the use of each laser sensor (during laser emission). Therefore, there is no need for a control means for alternately synchronizing the laser light source elements of the plurality of laser sensors, the photodetectors, the photodetector output processing circuits, and the like.

[0017]

FIG. 5 shows a laser sensor device according to the present invention.
It is the figure which showed typically one example of the whole arrangement | positioning and the schematic structure of each laser sensor about the case used for the level | step difference measurement shown to (a). In the figure, some of the elements common to FIG. 1 and FIG. 2A are given the same numbers.

In FIG. 5, the laser sensor device is composed of two laser sensors 10 and 20 arranged in close proximity to each other. The laser sensors 10 and 20 are laser light source elements 1 and 1 '(built-in collimator lenses if necessary), projection lenses 3 and 3', condenser lenses 5 and 5 ', and position detection type detector (PSD) 6, It has 6 '. These constituent elements themselves are basically the same as those of the conventional laser sensor shown in FIG. 1, but the laser light source element 1 of each of the laser sensors 10 and 20 has a configuration according to the features of the present invention. As 1 ', those having emission wavelengths different from each other are used, and spectral filter means FL1 and FL2 are arranged in each light receiving side optical path.

The filter means FL1 of the laser sensor 10 is selected to have a spectral characteristic that cuts off the emission wavelength of the laser light source 1'of the laser sensor 20.
As the filter means FL2 of 0, one having a spectral characteristic of cutting off the emission wavelength of the laser light source 1 of the laser sensor 10 is selected.

For example, the laser light source 1 has an emission wavelength of 78.
When the GaAlAs semiconductor laser of 0 nm is used and the GaAlAs semiconductor laser of the emission wavelength 830 nm is also used as the laser light source 1 ′, the filter means FL1 and FL2 are used.
An interference filter (also called an ND filter) having a spectral transmission characteristic as shown in FIG. 6 is selectively used.

That is, as the filter means FL1, as shown by η 1 (λ) in the figure, most of the light in the wavelength band around 780 nm is transmitted, but the light on the long wavelength side from around 830 nm is almost blocked. While an interference filter showing a transition of the spectral transmittance η is used, as the filter means FL2, as shown by η2 (λ), most of the light in the wavelength band around 830 nm is transmitted, but the wavelength from around 780 nm is short. An interference filter that changes the spectral transmittance η so as to block most of the light on the wavelength side is used.

The operation of the laser sensor device when such a configuration is adopted in each section will be described below. The laser beam 11 having a wavelength of 780 nm emitted from the laser light source element (semiconductor laser) of the laser sensor 10 is collimated by a built-in collimator lens (not shown) as necessary, and the beam diameter is narrowed by the projection lens 3. Then, it is projected as spot light on the surface 30 to be inspected. This projected spot light image is formed as a detection spot image on the detection surface of the position detection type photodetector (PSD) 6 via the interference filter FL1 having a spectral transmission characteristic represented by η 1 (λ) and the condenser lens 5. To be imaged.

Detector (PSD) 6 having a position detecting function
1 is processed in the manner described in the related description part of FIG. 1 to generate a signal representing the vertical position of the surface 30 in the figure or its displacement.

On the other hand, the wavelength 830 emitted from the semiconductor laser 1'constituting the laser light source element of the laser sensor 20.
The laser beam 21 of nm is collimated by a built-in collimator lens (not shown) if necessary,
The beam diameter is narrowed down by the projection lens 3 ′ and projected onto the surface 40 to be inspected as spot light. This projection spot light image is detected on the detection surface of the position detection type photodetector (PSD) 6'through an interference filter FL2 having a spectral transmission characteristic represented by η2 (λ) and a condenser lens 5 '. Is imaged as. The detection signal of the position detection type detector (PSD) 6'is processed in the same manner as the detection signal of the position detection type detection device 6 to generate a signal indicating the vertical position in the figure of the surface 40 or its displacement. . And both laser sensors 1
The level difference D of the surfaces 30 and 40 or its variation is detected from the difference output of the signals representing the positions or displacements of the surfaces 30 and 40 generated by 0 and 20.

By the way, the two laser sensors 10 and 20
Are arranged close to each other, each laser sensor 10, 20
In the incident optical paths of the position detection type detectors 6 and 6 ', the other laser light is scattered along various paths. For example, in FIG.
As indicated by a wavy line AM <b> 1, a part of the light from the spot image by the light source 1 ′ of the laser sensor 20 directly enters from the position 22 toward the light detection unit of the laser sensor 10. Further, as indicated by a wavy line AM2, a part of the light from the spot image by the light source 1 of the laser sensor 10 is partially moved from the position 12 to the position P1 on the wall surface of the laser sensor 10 and the surface 4 to be measured.
After being reflected at the position P2 above 0, it is possible for the light to enter the light detecting portion of the laser sensor 20 in the form of stray light.

However, unlike the case of the prior art, the spectral transmission characteristics represented by η 1 (λ) and η 2 (λ) are respectively present in the incident optical paths of the position detection type photodetectors (PSD) 6 and 6 ′. The interference filters FL1 and FL2 having a wavelength of 78 are arranged.
Since a 0 nm GaAlAs semiconductor laser and a GaAlAs semiconductor laser with an emission wavelength of 830 nm are used as the laser light source 1 ′, a position detection type photodetector (PS
D) Light derived from the other laser beam does not reach either 6 or 6 '.

That is, even if ambient light enters the other laser sensor side through a path such as AM1 or AM2,
The filters FL1, FL2 substantially prevent the position sensitive photodetectors (PSDs) 6 and 6 ′ from reaching.

FIGS. 7 and 8 show a filter FL1 having a central wavelength of 780 nm and a half-value width of 70 nm for verifying the occurrence of interference between laser sensors when the laser sensor device having the above-described structure is used. 7), and 1
4 nm (Fig. 8) interference filter (Nippon Vacuum Optical, DI
F-BPF-4 type and DIF-BPF-1 type) are used, and the detection output measured under the same conditions as the case shown in FIG. 4 (without using the interference filter) is the same as that of FIG. It is shown by.

In FIG. 7, the half value width of the interference filter FL1 is 70 nm, which is rather wide, so that the total amount of light received by the position detection type photodetector (PSD) 6 is relatively large, but it slightly occurs. The noise, which is considered to be due to the interference phenomenon, is superimposed in the magnitude of δ1 (peak-to-peak; PEAK-TO-PEAK) shown in the figure.

On the other hand, in FIG. 8, the interference filter F
Since the half-value width of L1 is narrowed down to 14 nm, the amount of light received by the position detection type photodetector (PSD) 6 as a whole is small, but the noise level is δ2 (peak-to-peak; PEAK) shown in the figure. -TO-PEAK), and it can be read that the interference phenomenon was almost completely suppressed.

As described above, in both cases of FIGS. 7 and 8, there is no doubt that remarkable noise reduction is realized as compared with the case of not using the filter of FIG.

That is, it has been confirmed that the structure of the above-described embodiment according to the technical idea of the present invention exerts a remarkable interference preventing effect. With regard to the emission wavelength, emission intensity of the semiconductor laser and the spectral characteristics of the interference filter, a wide variety of them are available these days. Therefore, the sensitivity of the position detection type photodetector (PSD) is taken into consideration, and it is suitable for the usage conditions. It goes without saying that it is preferable to use the semiconductor laser and the interference filter in combination.

Further, two or more filters may be overlapped and used in order to obtain a desired spectral transmission characteristic, and the filters are fixed around the condenser lens, immediately before the position detection type photodetector (PSD) or the like. Instead of arranging them, it is also possible to arrange them so that one kind or two or more kinds of filters can be selectively inserted and removed. According to such an arrangement, when there is no fear of occurrence of an interference phenomenon such as when one laser sensor is used alone, a filter is not used to secure a sufficient amount of received light, or a different emission wavelength is used. When a semiconductor laser is used, it is possible to deal with it by replacing the filter inserted in the optical path.

Further, in the above embodiment, the number of laser sensors used simultaneously at the close position is two, but by devising the combination of the emission wavelength of the laser light source element to be used and the spectral transmission characteristics of the filter, it is possible to reduce the number of laser sensors to three. It will be apparent from the above description that a laser sensor device to which the technical idea of the present invention is applied can be configured even when two or more laser sensors are simultaneously used at close positions.

[0035]

In the laser sensor device of the present invention, the light emission wavelengths of the laser light source elements belonging to the respective laser sensor means are different from each other, and other laser light sources are included in the incident light path of the photodetector (PSD) of each laser sensor means. Since the spectral filter means having the function of effectively blocking the light of the wavelength emitted from the laser light source element belonging to the laser sensor of No. 2 is arranged, even if two or more laser sensors are used at the close positions at the same time, Light emitted from a laser light source element belonging to another laser sensor is prevented from being incident on its own photodetector (PSD) via an object or a peripheral object.

Therefore, as in the conventional case, it is possible to continuously use two or more laser sensors simultaneously at a close position without fear of deterioration of measurement accuracy or unmeasurable state caused by incidence of ambient light. . Also, at that time,
It is not necessary to stop the emission of the laser light source elements belonging to other laser sensors or reduce the light emission state to weak light emission while using each laser sensor (during laser emission). There is no need for a control means for alternately and synchronously operating the detector, the photodetector output processing circuit, and the like, and there is an advantage that the configuration of the entire system using the laser sensor device is simplified.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional laser sensor device.

2A and 2B are schematic diagrams showing an example in which two or more laser sensors are simultaneously used at positions close to each other, in which FIG. 2A is a step measurement, and FIG. 2B is a triangle ridge angle θ. It is an example of an arrangement used for measurement.

FIG. 3 is a schematic diagram showing another example in which two or more laser sensors are simultaneously used at positions close to each other, and (a) is
An example is shown of an arrangement for measuring the thickness of a plate-like object, and an arrangement for measuring the heights of two columnar objects located close to each other on the same plane.

FIG. 4 is a diagram showing an example of detection output when an interference phenomenon occurs in two laser sensors.

FIG. 5 is a diagram schematically showing an example of the overall arrangement and the schematic configuration of each laser sensor when the laser sensor device of the present invention is used for the step measurement shown in FIG. 2 (a).

6 is a graph illustrating the spectral transmission characteristics of an interference filter that can be used in the laser sensor device shown in FIG.

FIG. 7 shows a center wavelength of 780n as a filter FL1 of one laser sensor of the laser sensor device shown in FIG.
It is an example of the detection output observed when m and a half value width of 70 nm are used.

8 is a center wavelength of 780n as a filter FL1 of one laser sensor of the laser sensor device shown in FIG.
This is an example of the detection output observed when m and the half width of 14 nm are used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser light source element (semiconductor laser or LD) 2 Collimator lens 3 Projection lens 4 Object to be inspected 5 Condensing lens 6 Position detection type detector (PSD) 7 Current-voltage conversion circuit 8 Arithmetic circuit 9 Monitor photodetector 10, 20 Laser sensor 11, 21 Laser beam 12, 22 Laser beam incident point 30, 40 Step surface 50 Triangular ridge 60 Plate-like or web-like object 70, 80 Cylindrical object CTL controller LDD Light source element drive circuit η1 (λ), η 2 (λ) Spectral transmittance curves of filters FL1 and FL2

Claims (1)

[Claims] 1. A laser light source element, an optical system for making output light of the laser light source element incident on an object to be inspected, a position detection type photodetector, and the position detection type photodetector to be inspected. In a laser sensor device provided with a plurality of laser sensor means having an optical system for allowing reflected light from an object to enter, the laser light source elements belonging to each of the plurality of laser sensor means have emission wavelength characteristics different from each other. , A spectral filter means having a function of blocking light of an emission wavelength of a laser light source belonging to another laser sensor means is disposed in an incident optical path to the photodetector of each of the plurality of laser sensor means. The laser sensor device described above.