JPH0560554A - Optical position measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an optical position measuring device capable of always accurately measuring the position of an object to be measured even when the amount of ambient light is very large. [Structure] A light source drive circuit 11 that drives a light source 2 in a pulsed manner and outputs a sampling signal synchronized with this pulse, and a plurality of signals amplified by amplifiers 6a and 6b when the light source 2 is turned on or turned off, or both. Correspondingly, the input circuit 13 which takes in and a plurality of signals V1, which are amplified by the amplifiers 6a and 6b by judging the magnitude of the taken-in signals,
It is composed of a determination circuit 14 for determining whether or not V2 is normal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical position measuring device for measuring the position of an object to be measured without contact.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an optical position measuring device disclosed in, for example, Japanese Patent Publication No. 56-10561. In the figure, 1 is an object to be measured, 2 is a light source using a semiconductor laser (LD), a light emitting diode (LED), or the like, 3 is light collected from the light source 2, and the light is emitted onto the object to be measured 1. A light projecting lens 4 for forming an image of the spot is provided on an optical axis which is reflected by the irradiation beam at an angle θ, and a light spot on the DUT 1 is detected by an optical position detecting element (hereinafter referred to as PSD).
Light receiving lens for forming an image on 5, 6a, 6b
Is an amplifier for amplifying the electric signal converted by PSD5, 7
Is a subtracter for calculating the difference between the outputs of the amplifiers 6a and 6b, 8
Is an adder for calculating the sum of the outputs of the amplifiers 6a and 6b, and 9
Reference numerals a and 9b are high-pass filters for purifying and extracting only signals converted from the laser pulse light. Reference numerals 10a and 10b are sampling and holding outputs from the high-pass filters 9a and 9b, respectively, in synchronization with the drive pulse from the light source drive circuit 11. A sample-and-hold circuit 12 is provided for dividing the output of the sample-and-hold circuits 10a and 10b.

Next, the operation will be described. The light source 2 is pulse-driven by the light source drive circuit 11, and emits light in a state where lighting / extinction is repeated. The light emitted from the light source 2 is focused by the light projecting lens 3 and becomes a light beam which is projected perpendicularly to the surface of the DUT 1. Here, the beam light scatters on the surface of a general object other than an ideal mirror surface, and spots of light from various angles, that is, light spots are observed. This light spot is imaged on the light receiving surface of the PSD 5 through the light receiving lens 4. The PSD 5 outputs two systems of current signals corresponding to the position of the formed light spot image, which are respectively input to the amplifiers 6a and 6b, and are respectively proportional to the voltage signal V.
1, converted to V2 and amplified. These voltage signals V
1 and V2 are both supplied to the subtractor 7 and the adder 8, and the subtractor 7 and the adder 8 subtract the voltage signals V1 and V2 (V1-V2) and the added voltage signal (V1 +), respectively.
V2) is output. These subtracted and added voltage signals are respectively passed through the high-pass filters 9a and 9b, so that only the portion related to the pulsed light is extracted and the influence of ambient light is reduced. The voltage signals passed through the high-pass filters 9a and 9b are supplied to the sample hold circuits 10a and 10b, respectively, and the sample hold circuits 10a and 10b both sample the input signal in synchronization with the drive pulse of the light source drive circuit 11. As a result, the light receiving signal having the pulse waveform is converted into a DC signal and output. Then, these output signals are supplied to the divider 12, and the divider 12 calculates (V1-V2) / (V1 + V2). As a result, a signal d proportional to the light amount barycentric position of the spot light formed on the light receiving surface of the PSD 5 is obtained, and the distance to the DUT 1 is measured based on the value of the signal d.

[0004]

Since the conventional optical position measuring device is configured as described above, the reflected light from the DUT 1 is the reflected light of the light emitted from the light source 2 and the light source 2.
Other than the above, reflected light from a light source such as an electric lamp (disturbance light) is considered, but normally, even if the disturbance light can be removed by the high-pass filters 9a and 9b, if the quantity of the disturbance light is very large, the amplifiers 6a and 6b are used. And subtractor 7 and adder 8
Was saturated, and there was a problem that an incorrect value was output. Even if the influence of ambient light is small, the DUT 1
Is a rough finished surface of metal, the spatial distribution of the amount of light diffusely reflected from the surface is not uniform and has a sharp peak in a specific direction, and the spatial distribution shows that the planar position of the DUT 1 is It has a property that it greatly changes if it changes, and in the measuring method in which the DUT 1 is moved in the direction orthogonal to the beam in order to measure the shape of the DUT 1, even if the light projection amount of the light source 2 is constant, The amount of received light fluctuates greatly during measurement, and therefore, the amplifiers 6a and 6b, the subtractor 7 and the adder 8 are saturated and an incorrect value is measured, or conversely, the amount of light is too small or the S / N ratio, or There was a problem that the resolution deteriorates.

The present invention has been made to solve the above problems, and provides an optical position measuring device capable of always accurately measuring the position of an object to be measured even when the amount of ambient light is very large. The purpose is to provide.

Further, according to the present invention, the position of the object to be measured can always be accurately measured even when the amount of ambient light is very large, and the position can be measured with high accuracy even on the object to be measured whose surface reflection state changes greatly. It is intended to provide a possible optical position measuring device.

[0007]

An optical position measuring device according to the present invention irradiates a light beam from a light source onto an object to be measured, and outputs a plurality of output signals of an optical position detecting element which receives the reflected light. Separately, in the optical position measuring device for calculating the position of the object to be measured by the amplifying means, the light source driving means for pulse-driving the light source and outputting the sampling signal synchronized with the pulse, and the amplifying means. In accordance with at least one of when the light source is turned on or when the light source is turned off, a plurality of signals that are amplified by And a determination unit that determines whether or not the plurality of signals amplified by the amplification unit are normal.

Further, in the optical position measuring device according to the present invention, a plurality of output signals of the light position detecting element for irradiating the object to be measured with the light beam from the light source and receiving the reflected light are individually sent to the amplifying means. In the optical position measuring device for calculating the position of the object to be measured, the light source is driven by a pulse, and a sampling signal synchronized with the pulse is output to the light source drive means and the amplification means. Multiple signals that are synchronized with the sampling signal of the light source drive circuit,
Input means for capturing at least one of when the light source is turned on or off, and determining whether or not a plurality of signals amplified by the amplifying means are normal from the magnitude of the signal captured by the input means, And a control means for controlling the light quantity of the light beam from the light source and controlling the amplification gain of the amplification means based on the determination result.

[0009]

According to the present invention, the light source driving means for driving the light source in a pulsed manner and outputting the sampling signal in synchronization with the pulse causes the plurality of signals amplified by the amplifying means to be provided at least when the light source is turned on or off. By correspondingly capturing and determining the magnitude of the output signal, it is possible to detect whether or not the measured value is normal.

In the present invention, the light quantity of the light beam from the light source and the amplification gain of the amplifying means are controlled to appropriate values by the control means on the basis of the determination results of the magnitudes of the plurality of output signals from the amplifying means. Adjusted to.

[0011]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a first embodiment of the present invention.
In the figure, 1 to 12 are the same as the conventional device. Reference numeral 13 is an input circuit which synchronizes with the sampling signal from the light source drive circuit 11 and takes in the outputs of the amplifiers 6a and 6b in response to lighting of the light source 2, and 14 has a predetermined threshold value, and this threshold value and the input It is a determination circuit that compares the output of the circuit 13 and determines whether the output is correct or not.

Next, the operation will be described. The light source 2 is pulse-driven by the light source drive circuit 11, and emits light in a state where lighting / extinction is repeated. The light emitted from the light source 2 is focused by the light projecting lens 3, becomes a beam light, is projected perpendicularly to the surface of the DUT 1, and the light reflected at the angle θ is condensed by the light receiving lens 4, A light spot is formed on the light receiving surface of the PSD 5. The PSD 5 outputs two systems of current signals corresponding to the position of the formed light spot image, which are respectively input to the amplifiers 6a and 6b, and the corresponding voltage signals V1 and V1, respectively.
It is converted to V2 and amplified. The voltage signals V1 and V2 output by the amplifiers 6a and 6b are synchronized with the sampling pulse of the light source driving circuit 11, and the respective values while the light source 2 is lit are fetched by the input circuit 13 and held. It should be noted that, here, the voltage signal V taken into the input circuit 13
The values of 1 and V2 are not only when the light source 2 is on, but also when it is off.
Alternatively, it may be a value in both. The held signal is output to the determination circuit 14. A threshold value for determining whether or not the amplifiers 6a and 6b are saturated has been set in advance in the determination circuit 14, and the determination circuit 14 compares this threshold value with the input voltage signals V1 and V2. Then
If these voltage signals V1 and V2 are greater than or equal to the threshold value, an error is output to the outside as a measurement error. On the other hand, the amplifiers 6a and 6b apply the voltage signal V to the subtractor 7 and the adder 8, respectively.
1 and V2 are output, and the subtracter 7 and the adder 8 subtract the voltage signals V1 and V2, respectively (V1-V2).
2) and the added voltage signal (V1 + V2) is output. These subtracted and added voltage signals pass through high-pass filters 9a and 9b, respectively, and are input to sample hold circuits 10a and 10b, respectively, and each sample hold circuit 10a and 10b is synchronized with the drive pulse of the light source drive circuit 11. The input signal is sampled, and as a result, the light receiving signal having a pulse waveform is converted into a DC signal and output. Then, these output signals are supplied to the divider 12, and in the divider 12, (V1-V2) / (V1 + V
Calculation of 2) is performed. As a result, a signal d proportional to the light amount barycentric position of the spot light formed on the light receiving surface of the PSD 5 is obtained, and the distance to the DUT 1 is measured based on the value of the signal d. Whether or not the measured distance is normal can be determined by the output state of the determination circuit 14 described above.

Embodiment 2. 2 is a block diagram showing a second embodiment of the present invention. In the figure, 1-5, 7-10, 1
Reference numerals 2 and 13 are the same as those in FIG. Reference numeral 15 is a light source drive circuit, 16a and 16b are amplifiers capable of switching amplification gains,
Reference numeral 17 has a judgment function of the judgment circuit 14 and generates a switching signal for switching the gains of the amplifiers 16a and 16b based on the output of the input circuit 13 and a control signal for adjusting the light emission amount of the light source 2 to the light source driving circuit 15. It is an arithmetic circuit as a control means for performing.

Next, the operation will be described. The light source 2 is pulse-driven by the light source drive circuit 15, and emits light in a state of repeatedly turning on / off. The light emitted from the light source 2 is focused by the light projecting lens 3, becomes a beam light, is projected perpendicularly to the surface of the DUT 1, and the light reflected at the angle θ is condensed by the light receiving lens 4, A light spot is formed on the light receiving surface of the PSD 5. The PSD 5 outputs two systems of current signals corresponding to the positions of the formed light spot images, which are respectively input to the amplifiers 16a and 16b, and the corresponding voltage signals V respectively.
1, converted to V2 and amplified. Amplifiers 16a and 1
The voltage signals V1 and V2 of 6b are synchronized with the sampling pulse of the light source drive circuit 15, and the respective values while the light source 2 is on and off are taken in and held by the input circuit 13. It should be noted that, here, the voltage signal V taken into the input circuit 13
The values of 1 and V2 are not only when the light source 2 is on and off,
The value in either case may be used. The held signals are output to the arithmetic circuit 17, respectively. First, arithmetic circuit 1
Reference numeral 7 compares the values of the voltage signals V1 and V2 when the light source 2 is turned on to a threshold value or more at which it can be determined that the amplifiers 16a and 16b are in a saturated state. It is determined whether any of these exceeds this threshold. If it exceeds, it is judged as a saturation error. Next, the arithmetic circuit 17 compares the values of the voltage signals V1 and V2 when the light source 2 is turned off with a threshold value at which it can be determined that ambient light is being received, and either of the voltage signals V1 and V2 is It is determined whether the threshold value is exceeded. If it exceeds, it is determined to be an ambient light error. The above operation is shown in FIG.
It is similar to the operation of the determination circuit 14 shown in FIG. That is, it may be considered that the arithmetic circuit 17 includes this determination function. The arithmetic circuit 17 performs the following control, for example, depending on the states of the saturation error and the ambient light error. When both the saturation error and the disturbance light error occur, it is determined that the values of the voltage signals V1 and V2 from the input circuit 13 are not normal, and the light source 2 emits light according to the light amount value signal L output from the arithmetic circuit 17. No adjustment of the amount or switching of the amplification gain by the gain value signal G of the amplifiers 16a and 16b is performed. In other cases, in order to keep the amount of light received by the PSD 5 constant, with respect to the values of the voltage signals V1 and V2 from the input circuit 13,
The arithmetic circuit 17 supplies the light amount value signal L as a control signal to the light source value driving circuit 15 to control it to adjust the light emission amount of the light source 2 and also to supply the gain value signal G to the amplifiers 16a and 16b as a switching signal. Then, the amplification gain is switched. At this time, the amplification gain is switched by N times, for example. According to this method, the amplifiers 16a and 16b are
It is possible to distinguish whether the output signal from the light source 2 is not normal due to the large amount of light emitted from the light source 2 or is not normal due to ambient light, and as a result, the adjustment of the amount of light emitted by the light amount value signal L from the light source 2 and the amplifiers 16a and 16b. It is possible to normally switch the amplifier gain by the gain value signal G. If the above determination is not performed, the following problems will occur. For example, if the amount of light received by the PSD 5 due to the reflection from the DUT 1 with respect to the light emitted from the light source 2 is small, originally,
The light amount of the light source 2 and the gains of the amplifiers 16a and 16b are PSD5.
However, when the amplifier 16a or 16b is saturated by ambient light, the voltage signal V
1 and V2 become large values, and the light emission amount of the light source 2 and the gain of the amplifier are erroneously controlled so that the light reception amount of the PSD 5 becomes small. Thus, the amplifiers 16a and 16
By determining the output signal from b by the arithmetic circuit 17, the light source 2 is normally operated so that the light receiving amount of the PSD 5 becomes constant.
The amount of light emission can be adjusted by the light amount value signal L, and the amplification gain can be switched by the gain value signal G of the amplifiers 16a and 16b.

[0015]

As described above, according to the present invention, a plurality of output signals of the optical position detecting element for irradiating the object to be measured with the light beam from the light source and receiving the reflected light are individually applied to the amplifying means. In the optical position measuring device for calculating the position of the object to be measured, the light source is driven by a pulse, and a sampling signal synchronized with the pulse is output to the light source drive means and the amplification means. A plurality of signals that are synchronized with the sampling signal of the light source drive circuit, and input means for taking in at least one of when the light source is turned on or off, and to the amplification means based on the magnitude of the signal taken by the input means. Since it is equipped with a determination means for determining whether or not a plurality of signals amplified by the optical system are normal, it is possible to always accurately measure the position of the measured object even when the amount of ambient light is very large. An effect that location measuring device is obtained.

Further, the light beam from the light source is applied to the object to be measured, and a plurality of output signals of the optical position detecting elements for receiving the reflected light are individually processed by the amplifying means to calculate the position of the object to be measured. In the optical position measuring device for measuring the light source, the light source is driven by a pulse and a sampling signal synchronized with the pulse is output, and a plurality of signals amplified by the amplifying means are sampled by the light source driving circuit. An input unit that is synchronized with the signal and that takes in at least one of when the light source is turned on and when the light source is turned off, and whether or not the plurality of signals amplified by the amplifying unit based on the magnitude of the signal taken by the input unit is normal or not. And the control means for controlling the light quantity of the light beam from the light source based on the determination result and controlling the amplification gain of the amplification means. The effect that the position of the object to be measured can always be measured accurately even when the amount of light is very large, and an optical position measuring device that can measure the position of the object to be measured with high fluctuation of the surface reflection state with high accuracy can be obtained. Play.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical position measuring device according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the optical position measuring device according to the present invention.

FIG. 3 is a configuration diagram showing a conventional optical position measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DUT 2 Light source 5 Optical position detection element (PSD) 6a, 6b, 16a, 16b Amplifier 11,15 Light source drive circuit 13 Input circuit 14 Judgment circuit 17 Arithmetic circuit

Claims (2)

[Claims] 1. A position of the object to be measured is obtained by irradiating an object to be measured with a light beam from a light source, and individually calculating a plurality of output signals of an optical position detecting element for receiving the reflected light by an amplifying means. In the optical position measuring device for measuring the light source, the light source is driven by a pulse and a sampling signal synchronized with the pulse is output, and a plurality of signals amplified by the amplifying means are sampled by the light source driving circuit. An input means that is synchronized with the signal and that takes in at least one of when the light source is turned on and when it is turned off, and whether or not the plurality of signals amplified by the amplifier means are normal based on the magnitude of the signal taken by the input means. An optical position measuring device, comprising: a determining unit that determines whether or not the position is determined. 2. The position of the object to be measured is obtained by irradiating the object to be measured with a light beam from a light source and individually processing a plurality of output signals of an optical position detecting element for receiving the reflected light by an amplifying means. In the optical position measuring device for measuring the light source, the light source is driven by a pulse and a sampling signal synchronized with the pulse is output, and a plurality of signals amplified by the amplifying means are sampled by the light source driving circuit. An input means that is synchronized with the signal and that takes in at least one of when the light source is turned on and when it is turned off, and whether or not the plurality of signals amplified by the amplifier means are normal based on the magnitude of the signal taken by the input means. And a control means for controlling the light amount of the light beam from the light source based on the determination result and controlling the amplification gain of the amplification means. Optical position measuring device.