JP2010197112A - Optical type displacement meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical type displacement meter which obtains an accurate result of measurement. <P>SOLUTION: A light projecting element 21 generates a beam of light. The light is radiated on a workpiece W through a light projecting lens 22 and a scanning part 23. The scanning part 23 scans the light one-dimensionally on the surface of the workpiece W. Reflected light from the workpiece W enters a light receiving element 31 through a light receiving lens 32. A light reception signal showing light reception amount distribution is obtained by a light receiving element 2. A light projection control part 3 controls a light emission level of the light projecting element 21. A light reception control part 4 controls an exposure time of the light receiving element 31. A waveform generating part 6 converts the light reception signal into waveform data. An FB control part 7 performs a feedback control of the light projection control part 3, the light reception control part 4 and the waveform generating part 6, based on the waveform data obtained by the waveform generating part 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical displacement meter for measuring a cross-sectional shape of an object.

  In an optical displacement meter using the principle of triangulation, light is applied to a measurement point on the surface of an object (hereinafter referred to as a workpiece), and the reflected light has pixels arranged in one or two dimensions. Light is received by the light receiving element. The height of the measurement point can be measured based on the peak position of the received light amount distribution obtained by the light receiving element.

  As a method of measuring the cross-sectional shape of the workpiece, there is a light cutting method. In the optical displacement type optical displacement meter, strip-shaped light having a linear cross section (hereinafter referred to as strip-shaped light) is irradiated onto a workpiece, and the reflected light is received by a two-dimensional light receiving element. The received light amount distribution obtained by the light receiving element is amplified by an amplifier and then converted into digital waveform data. Based on the peak position of the waveform data, the height of each measurement point is detected.

  By the way, the amount of received light reflected from the work surface varies depending on the reflectance of the work surface. Due to the change in the amount of received light, the peak height of waveform data (hereinafter referred to as peak level) changes. For accurate measurement, it is necessary to adjust the peak level within a certain range.

  Therefore, the peak level is adjusted by controlling the light emission level of the light applied to the workpiece, the exposure time of the light receiving element, the gain of the amplifier, and the like. However, in the above-described light cutting method, the intensity of the band-like light is uniform in the width direction, and therefore the appropriate amount of received light may not be obtained if the reflectance of the workpiece surface varies greatly depending on the part.

  For example, if the total amount of received light is controlled so as to make the amount of light received from a measurement point with low reflectance appropriate, the amount of light received is saturated at a portion with high reflectance. On the other hand, if the intensity of the strip light is lowered to make the amount of light received from the measurement point with high reflectivity an appropriate level, the amount of light received from the part with low reflectivity becomes small, and a peak is detected on the waveform data. I can't do that.

  Accordingly, there is an optical scanning method as another method for measuring the cross-sectional shape of the workpiece. In the optical scanning type optical displacement meter, light is reciprocally scanned in one direction of the workpiece (hereinafter referred to as the X direction) by the light projecting unit. In this case, a plurality of received light amount distributions by reflected light from a plurality of measurement points along the X direction are obtained. Each received light amount distribution is amplified by an amplifier and then converted into digital waveform data. The heights of the plurality of measurement points along the X direction are detected based on the peak positions of the waveform data corresponding to the plurality of received light amount distributions. Thereby, the cross-sectional shape along the X direction of the workpiece can be measured. In the optical scanning optical displacement meter, the peak level can be adjusted for each measurement point, so that accurate measurement can be performed on the entire workpiece even when the reflectance of the workpiece surface varies greatly depending on the part.

  By performing feedback control on the light emission level, exposure time, and gain, the peak level can be adjusted during measurement at each measurement point. For example, at the time of measurement at each measurement point, the light emission level, the exposure time, and the gain are feedback controlled based on the result of the previous measurement.

  However, according to the optical scanning type optical displacement system, the irradiation position of light always moves. Therefore, if the reflectance differs greatly between adjacent measurement points, the peak level can be adjusted even if the light emission level, exposure time, and gain are controlled during measurement at the other measurement point based on the measurement result at one measurement point. It cannot be adjusted properly.

  Therefore, as shown in Patent Document 1, in a plurality of reciprocating scans of light, peak levels corresponding to a plurality of measurement points in the next scan are respectively determined based on peak levels corresponding to a plurality of measurement points in the current scan. A control method is known. According to this method, even if there is a difference in reflectance between adjacent measurement points, the peak level of reflected light from each measurement point can be adjusted appropriately.

Japanese Patent No. 3613708

  In the optical scanning optical displacement meter, the exposure time of the light receiving element can be easily controlled by the electronic shutter in the light receiving element. Therefore, normally, the peak level is adjusted by controlling the exposure time of the light receiving element.

  However, for high-speed measurement, it is necessary to increase the light scanning speed. In this case, even if the exposure time is changed slightly, the light irradiation range at each measurement point is greatly different. This makes it difficult to obtain accurate measurement results.

  An object of the present invention is to provide an optical displacement meter capable of obtaining an accurate measurement result.

  (1) An optical displacement meter according to the present invention is a light scanning unit that scans light on the surface of an object by controlling a light generation unit that generates light and a light projecting direction of the light generated by the light generation unit. Means, a condensing optical system for condensing the reflected light from the object, and a plurality of pixels disposed on the condensing surface of the condensing optical system, and a concentrator that changes according to the distance to the object A light receiving element that outputs a light receiving signal indicating a received light amount distribution corresponding to the position of the light spot, a waveform data generating unit that amplifies the light receiving signal output from the light receiving element to generate waveform data, and light projection by an optical scanning unit Waveform data generated by the waveform data generator that controls the light emission intensity of the light generator and the exposure time of the light receiving element based on the setting value of the light emission intensity by the light generator and the exposure time of the light receiving element for each direction. Light so that the peak level of the Control means for adjusting the setting value of the light emission intensity and the setting value of the exposure time for each light projection direction by the inspection means, and the control means preferentially adjusts the setting value of the light emission intensity over the setting value of the exposure time. Is.

  In the optical displacement meter, light is scanned on the surface of the object by controlling the light projecting direction of the light generated by the light generator by the light scanning means. The reflected light from the object is condensed by the condensing optical system and enters the light receiving element. The light receiving element outputs a light receiving signal indicating a received light amount distribution corresponding to the position of the focused spot. Waveform data is generated by the waveform data generation unit based on the output light reception signal. Based on the peak position of the generated waveform data, the height of the surface at the measurement point (light irradiation position) of the object in the light projection direction can be measured. Thereby, the cross-sectional shape of the object can be measured by measuring the heights of a plurality of measurement points on the surface of the object.

  The light emission intensity of the light generation unit and the exposure time of the light receiving element are controlled based on the set value of the light emission intensity by the light generation unit and the set value of the exposure time of the light receiving element for each light projection direction by the optical scanning unit. The set value of the emission intensity and the set value of the exposure time are adjusted so that the peak level of the waveform data generated by the waveform data generation unit falls within a predetermined range for each light projection direction by the optical scanning unit.

  In this case, the set value of the light emission intensity of the light generation unit is adjusted with priority over the set value of the exposure time of the light receiving element. Accordingly, it is possible to suppress the exposure time of the light receiving element from fluctuating greatly every measurement. As a result, accurate measurement results can be obtained stably.

  (2) The control means may adjust the setting value of the exposure time in addition to the setting value of the light emission intensity when the peak level cannot be adjusted to the predetermined range even if the setting value of the light emission intensity is adjusted. .

  In this case, the peak level can be adjusted to a predetermined range by adjusting the exposure time setting value to a minimum. Thereby, the fluctuation of the exposure time is suppressed to the minimum. As a result, accurate measurement results can be obtained stably.

  (3) The control unit further controls the amplification factor of the waveform data generation unit based on the set value of the amplification factor of the waveform data generation unit for each light projection direction by the optical scanning unit, and the waveform generated by the waveform data generation unit The set value of the amplification factor may be adjusted for each light projecting direction by the optical scanning unit so that the peak level of the data falls within a predetermined range.

  In this case, the peak level of the waveform data can be easily adjusted by adjusting the amplification factor of the waveform data generation unit.

  (4) The control means may preferentially adjust the gain setting value over the exposure time setting value.

  In this case, fluctuations in exposure time are suppressed. As a result, accurate measurement results can be obtained stably.

  (5) The control means may preferentially adjust the set value of the light emission intensity over the set value of the amplification factor.

  In this case, it is suppressed that the amplification factor of the waveform data generation unit varies greatly from measurement to measurement. Therefore, it becomes possible to maintain the amplification factor in a low state. Therefore, it is possible to suppress a decrease in the resolution of the waveform data. As a result, a decrease in measurement accuracy due to noise can be suppressed.

  (6) The position of the condensing spot changes along the first direction according to the distance to the object, and the plurality of pixels of the light receiving element are arranged so as to be aligned along the first direction. The length of each of the plurality of pixels in the second direction orthogonal to the one direction may be greater than the length of each of the plurality of pixels in the first direction.

  In this case, the received light amount distribution in the first direction can be reliably obtained, and the reflected light of the light reciprocally scanned on the surface of the object can be reliably received. In addition, it is possible to proceed with the measurement more quickly than when a plurality of pixels are arranged two-dimensionally.

  (7) The length of each of the plurality of pixels in the first direction may be not less than 10 times and not more than 1000 times the length of each of the plurality of pixels in the second direction.

  In this case, it is possible to promptly measure with higher accuracy while more reliably receiving the reflected light from the object.

  According to the present invention, it is possible to suppress the exposure time of the light receiving element from fluctuating greatly every measurement. As a result, accurate measurement results can be obtained stably.

It is a block diagram which shows the structure of the optical displacement meter which concerns on this Embodiment. It is a schematic diagram for demonstrating the measuring method of the cross-sectional shape of the workpiece | work by an optical displacement meter. It is a schematic diagram for demonstrating the measuring method of the cross-sectional shape of the workpiece | work by an optical displacement meter. It is a schematic diagram which shows an example of waveform data. It is a schematic diagram which shows the relationship between the scanning of light and measurement timing. It is a flowchart of the peak level adjustment process by FB control part. It is a typical top view which shows the specific example of a light receiving element. It is a figure for demonstrating the adjustment method of the exposure time T in a common light projection direction. It is a figure which shows the relationship between the exposure time and the production | generation time of waveform data in the conventional optical displacement meter. It is a figure which shows the relationship between the exposure time in this Embodiment, and the generation time of the waveform data by a waveform generation part.

  Hereinafter, an optical displacement meter according to an embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of Optical Displacement Meter FIG. 1 is a block diagram showing the configuration of the optical displacement meter according to the present embodiment. As shown in FIG. 1, the optical displacement meter 100 includes a light projecting unit 1, a light receiving unit 2, a light projecting control unit 3, a light receiving control unit 4, a waveform generating unit 6, a feedback control unit (hereinafter abbreviated as FB control unit). 7), a waveform processing unit 8, a profile generation unit 9, a measurement processing unit 10, and an interface unit 11.

  The light projecting unit 1 includes a light projecting element 21, a light projecting lens 22, and a scanning unit 23. The light projecting element 21 includes, for example, a laser diode, and generates beam-shaped light. The light is applied to an object (hereinafter referred to as a workpiece) W via the light projection lens 22 and the scanning unit 23. The scanning unit 23 includes, for example, a galvano scanner, and scans light one-dimensionally on the surface of the workpiece W as will be described later.

  The light receiving unit 2 includes a light receiving element 31 and a light receiving lens 32. Reflected light from the workpiece W enters the light receiving element 31 via the light receiving lens 32. The light receiving element 2 includes a CMOS (complementary metal oxide semiconductor) sensor, for example, and has a plurality of pixels arranged in one direction. As a result, an analog received light signal indicating the received light amount distribution in the arrangement direction of the plurality of pixels is obtained.

  The light projecting control unit 3 controls the intensity of light generated by the light projecting element 21 (hereinafter referred to as a light emission level) by adjusting the drive current of the light projecting element 21, for example. The light reception control unit 4 controls the exposure time of the light receiving element 31 by an exposure control signal described later.

  A shutter that blocks the optical path from the workpiece W to the light receiving element 31 may be provided. In that case, the exposure time of the light reception control unit 4 can be controlled by opening and closing the shutter. Further, the exposure time of the light receiving element 31 may be controlled by controlling the light emission time of the light projecting element 21.

  The waveform generator 6 includes an amplifier and an analog / digital converter. The light reception signal obtained by the light receiving element 31 is amplified by an amplifier and then analog / digital converted by an analog / digital converter. Thereby, digital waveform data is obtained.

  The FB control unit 7 feedback-controls the light projection control unit 3, the light reception control unit 4, and the waveform generation unit 6 based on the waveform data obtained by the waveform generation unit 6. Details of the control operation of the FB control unit 7 will be described later.

  The waveform processing unit 8 generates distance information indicating the distance from the light projecting unit 1 to each measurement point on the surface of the workpiece W based on the waveform data obtained by the waveform generation unit 6. The measurement points will be described later.

  The profile generation unit 9 generates profile data representing the cross-sectional shape of the workpiece W based on the distance information calculated by the waveform processing unit 7. The measurement processing unit 10 performs correction processing and measurement processing on the profile data created by the profile generation unit 9. Here, the measurement process is a process of calculating the size of an arbitrary part on the surface of the workpiece W based on the profile data.

  The waveform data obtained by the waveform generator 6 is taken out through the interface unit 11. The user performs various settings and inputs through the interface unit 11. Thereby, the FB control unit 7, the waveform processing unit 8, and the measurement processing unit 10 are controlled.

(2) Measuring Method FIGS. 2 and 3 are schematic diagrams for explaining a measuring method of the cross-sectional shape of the workpiece W by the optical / displacement meter 100. FIG. 4 is a schematic diagram illustrating an example of waveform data. 2 and 3, three directions orthogonal to each other are defined as an X direction, a Y direction, and a Z direction, as indicated by arrows X, Y, and Z. In the waveform data of FIG. 4, the horizontal axis corresponds to the position on the light receiving element 31 in the pixel arrangement direction, and the vertical axis corresponds to the received light amount.

  In this example, the position (height) in the Z direction of each measurement point on the workpiece W is measured. Here, the measurement point refers to a portion on the workpiece W that is irradiated with light during one exposure period of the light receiving element 31.

  At the time of measurement, the light receiving element 31 is exposed by the light receiving control unit 4 (FIG. 1). At this time, as shown in FIG. 2, the light emitted from the light projecting unit 1 to the measurement point P <b> 1 on the workpiece W enters the light receiving element 31 through the light receiving lens 32. In this case, as indicated by the dotted line, when the height of the measurement point P1 is different, the incident position of the reflected light on the light receiving element 31 is different in the Y1 direction. Thereby, the received light amount distribution of the light receiving element 31 is different.

  Each pixel of the light receiving element 31 is arranged along the Y1 direction on the light collection surface by the light receiving lens 32. Here, the light collection surface refers to a surface formed by a plurality of light collection points.

  The received light signal indicating the received light amount distribution of the light receiving element 31 is converted into waveform data by the waveform generator 6 (FIG. 1). As shown in FIG. 4, the waveform data indicates the received light amount distribution of the light receiving elements 31 in the pixel arrangement direction. The peak position corresponds to the height of the measurement point P1, and when the height of the measurement point P1 changes, the peak position changes. That is, the height of the measurement point P1 can be detected based on the peak position of the waveform data.

  As shown in FIG. 3, the light from the light projecting unit 1 is scanned along the X direction on the surface of the workpiece W by the scanning unit 23 (FIG. 1). The light receiving element 31 is exposed by the reflected light from the workpiece W at a predetermined timing.

  In this case, the position of each measurement point in the X direction is recognized based on the light projecting direction from the light projecting unit 1, and the position of each measurement point in the Z direction (each measurement based on the received light amount distribution of the light receiving element 31). Point height) is detected. Thereby, the cross-sectional shape of the workpiece W along the XZ plane can be detected two-dimensionally.

  Furthermore, the workpiece W is moved in the Y direction continuously or intermittently. The intermittent movement of the workpiece W in the Y direction is performed, for example, every time the light is reciprocated in the X direction. Thereby, the surface shape of the workpiece W can be detected three-dimensionally.

  FIG. 5 is a schematic diagram showing the relationship between light scanning and measurement timing. In FIG. 5, the horizontal axis indicates time, and the vertical axis indicates the light scanning position on the workpiece W in the X direction. In FIG. 5, the light scanning position in the X direction corresponds to the light projecting direction in the XZ plane from the light projecting unit 1.

  As shown in FIG. 5, the scanning position of light reciprocates a certain distance along the X direction. In the present embodiment, measurement is performed at a constant cycle so that the light projecting direction from the light projecting unit 1 coincides with a predetermined direction at each measurement. That is, in FIG. 5, measurement is performed at time points t11 to t16, t21 to t26, and t31 to t36 when the scanning position of the light in the X direction coincides with the positions P11, P12, and P13.

  If the surface of the workpiece W is uneven, the light scanning position in the X direction may be different even if the light projection direction is common. Therefore, in practice, in the X direction, the scanning position of the light at the time of measurement may be slightly different for each scanning.

  In the present embodiment, feedback control of the light projection control unit 3, the light reception control unit 4, and the waveform generation unit 6 is performed based on the previous measurement result in the common light projection direction. That is, in the example of FIG. 5, feedback control at time t12 is performed based on the measurement result at time t11, and feedback control at time t13 is performed based on the measurement result at time t12. Thereafter, at time points t14 to t16, feedback control is similarly performed based on the previous measurement result at the same position in the X direction.

  Similarly, feedback control is performed based on the previous measurement result at the same position in the X direction at time points t21 to t26. Similarly, based on the previous measurement result at the same position in the X direction at time points t31 to t36. Feedback control is performed.

(3) Control Method In the above waveform data, in order to accurately specify the peak position, it is desirable that the peak height (hereinafter referred to as peak level) is within a predetermined range. The peak level is proportional to the product of the amount of light received by the light receiving element 31 and the circuit gain of the waveform generator 6 (the amplification factor of the amplifier in the waveform generator 6). The amount of light received by the light receiving element 31 is proportional to the product of the light emission level of the light projecting element 21 and the exposure time of the light receiving element 31.

  In the present embodiment, the FB control unit 7 feedback-controls the light projection control unit 3, the light reception control unit 4, and the waveform generation unit 6 based on the waveform data obtained by the waveform generation unit 6.

  In this case, the FB control unit 7 can control the light projection control unit 3 to control the light emission level of the light projecting element 21, and the light reception control unit 4 can control the exposure time of the light receiving element 31. Can be controlled. Further, the circuit gain of the waveform generation unit 6 can be controlled by the FB control unit 7 controlling the waveform generation unit 6. In the following description, the light emission level of the light projecting element 21, the exposure time of the light receiving element 31, and the circuit gain of the waveform generator 6 are referred to as a light emission level P, an exposure time T, and a circuit gain G, respectively.

  Details of the control operation of the FB control unit 7 will be described. FIG. 6 is a flowchart of peak level adjustment processing by the FB control unit 7.

  Here, the FB control unit 7 sets the light emission level P, the exposure time T, and the circuit gain G based on the preset light emission level P, exposure time T, and circuit gain G values (hereinafter referred to as setting values). Control. This set value is set for each light projecting direction in which measurement is performed, and is stored in the storage device in the FB control unit 7. That is, in the example of FIG. 5, set values of the light emission level P, the exposure time T, and the circuit gain G are set so as to correspond to the positions P11, P12, and P13, respectively. In the initial state, the set values of the light emission level P, the exposure time T, and the circuit gain G in each light projecting direction may be common.

  As shown in FIG. 6, first, the FB control unit 7 determines whether or not new waveform data has been obtained by the waveform generation unit 6 (step S1). The waveform data is updated every time measurement is performed.

  When the waveform data is not obtained, the FB control unit 7 stands by until the waveform data is obtained. When the waveform data is obtained, the FB control unit 7 acquires the peak level of the waveform data (step S2). Next, the FB control unit 7 calculates the ratio of the peak level to the preset reference value (step S3).

  Next, the FB control unit 7 determines whether or not the calculated ratio is within a preset specified range (step S4). If the calculated ratio is within the specified range, the FB control unit 7 proceeds to the process of step S13 described later.

  If the calculated ratio is not within the specified range, the FB control unit 7 acquires set values of the light emission level P, the exposure time T, and the circuit gain G at the time of the current measurement (step S5).

  Next, the FB control unit 7 determines whether or not the peak level can be adjusted to the reference value by adjusting the set value of the light emission level P (step S6). Here, since the adjustable range of the set value of the light emission level P is limited, even if the set value of the light emission level P is adjusted to the maximum when the difference between the acquired peak level and the reference value is large. The peak level cannot be adjusted to the reference value.

  When the peak level can be adjusted to the reference value by adjusting the set value of the light emission level P, the FB control unit 7 corresponds to the light projecting direction so that the peak level matches the reference value. The set value of the light emission level P is adjusted (step S7), and the process proceeds to step S13 described later.

  On the other hand, when the peak level cannot be adjusted to the reference value only by adjusting the light emission level P, the FB control unit 7 sets the light emission level P corresponding to the light projecting direction so that the peak level approaches the reference value. The value is adjusted to the maximum (step S8).

  Subsequently, the FB control unit 7 determines whether or not the peak level can be matched with the reference value by adjusting the set value of the circuit gain G (step S9). Here, since the adjustable range of the circuit gain G is limited, if the difference between the peak level that can be adjusted by adjusting the light emission level P and the reference value is large, the set value of the circuit gain G is maximized. Even after adjustment, the peak level cannot be adjusted to the reference value.

  When the peak level can be matched with the reference value by adjusting the set value of the circuit gain G, the FB control unit 7 corresponds to the light projecting direction so that the peak level matches the reference value. The set value of the circuit gain G is adjusted (step S7), and the process proceeds to step S13 described later.

  On the other hand, if the peak level cannot be adjusted to the reference value by adjusting the circuit gain G, the FB control unit 7 sets the circuit gain G corresponding to the light projecting direction so that the peak level approaches the reference value. The setting is adjusted to the maximum (step S11). Subsequently, the FB control unit 7 adjusts the set value of the exposure time T corresponding to the light projection direction so that the peak level matches the reference value (step S12), and proceeds to the process of step S13.

  In step S <b> 13, the FB control unit 7 controls the light emission level P, the exposure time T, and the circuit gain G based on the set value corresponding to the light projecting direction to be measured next. The set value used in step S13 is adjusted in advance by the processes in steps S1 to S12 at the time of the previous measurement in the light projecting direction. For example, when measuring the position P11 at time t12 in FIG. 15, a set value adjusted based on the measurement result of the position P11 at time t11 is used. Thereafter, the FB control unit 7 returns to the process of step S1.

  Thus, in the present embodiment, the adjustment of the setting value of the light emission level P and the adjustment of the setting value of the circuit gain G are preferentially performed as compared with the adjustment of the setting value of the exposure time T. Thereby, it is suppressed that the exposure time T fluctuates greatly for each measurement. Therefore, the movement distance of the light irradiation position during each measurement is substantially constant. As a result, accurate measurement results can be obtained stably.

  Further, the adjustment of the setting value of the light emission level P is preferentially performed compared to the adjustment of the setting value of the circuit gain G. Thereby, the fluctuation of the circuit gain G is also suppressed. Therefore, the circuit gain G can be kept as low as possible. Therefore, it is possible to suppress a decrease in the resolution of the waveform data. As a result, even when a lot of noise is generated, the measurement accuracy can be kept high.

(4) Other control examples (4-1)
In the above example, the adjustment of the setting value of the circuit gain G is performed with priority over the adjustment of the setting value of the exposure time T. However, particularly when a lot of noise occurs, the resolution is sufficiently lowered due to the increase of the circuit gain G. Therefore, the adjustment of the setting value of the exposure time T may be performed with priority over the adjustment of the setting value of the circuit gain G.

(4-2)
The adjustment range of the setting value of the circuit gain G is provided in two steps of high and low, and the adjustment in the range where the setting value of the circuit gain G is lower than the adjustment of the setting value of the exposure time T is given priority, and the setting value of the circuit gain G is set. The adjustment of the set value of the exposure time T may be performed with priority over the adjustment in a high range.

  That is, if the peak level cannot be adjusted to the reference value even if the set value of the light emission level P is adjusted, the FB control unit 7 adjusts the light emission level P to the maximum and sets the set value of the circuit gain G. By adjusting in a low range, the peak level is made to coincide with the reference value.

  If the peak level cannot be adjusted to the reference value even if the set value of the light emission level P is adjusted to the maximum and the set value of the circuit gain G is adjusted to the maximum within a low range, the FB control unit 7 While adjusting the set value of the circuit gain G to the maximum within a low range, the peak level is made to coincide with the reference value by adjusting the set value of the exposure time T.

  If the peak level cannot be adjusted to the reference value even if the setting value of the exposure time T is adjusted to the maximum, the FB control unit 7 adjusts the setting value of the exposure time T to the maximum and the peak level is The set value of the circuit gain G is adjusted in a high range so as to coincide with the reference value.

  In this case, fluctuations in the exposure time T can be suppressed while suppressing an increase in the circuit gain G. Thereby, highly accurate measurement can be performed more reliably.

(4-3)
When the peak level is higher than the predetermined range, the adjustment of the setting value of the circuit gain G may be performed with priority over the adjustment of the setting value of the light emission level P.

  In this case, if the peak level is higher than a predetermined value, the set value of the circuit gain G is first lowered. This prevents the set value of the circuit gain G from being kept high. Therefore, it is possible to more reliably suppress a decrease in the resolution of the waveform data.

(5) Light Receiving Element Here, the light receiving element 31 will be described in detail. FIG. 7 is a schematic plan view showing a specific configuration of the light receiving element 31. In FIG. 7, an X direction and a Y1 direction orthogonal to each other are defined.

  As shown in FIG. 7, the light receiving element 31 includes a plurality of pixels PE and a shift register SR arranged in the Y1 direction. Each pixel PE extends in a long shape in the X direction. The width of each pixel PE is, for example, 20 μm, and the length of each pixel PE is, for example, 6.4 mm. The total number of pixels PE is 320, for example. In this case, the light receiving element 31 has a substantially square shape.

  As shown in FIG. 2, according to the height (position in the Z direction) of the measurement point P1 on the workpiece W, the incident position of the reflected light on the light receiving element 31 at the measurement point P1 changes along the Y1 direction. . Thereby, the received light amount distribution corresponding to the height of the measurement point P1 is obtained by the plurality of pixels PE.

  Further, as shown in FIG. 3, the light from the light projecting unit 1 is scanned on the workpiece W along the X direction. Thereby, the incident position of the reflected light to the light receiving element 31 changes along the X direction. Therefore, in order to reliably receive the reflected light, it is necessary to secure the length of the light receiving element 31 in the X direction by the change in the incident position due to the light scanning.

  In this case, it is conceivable to use an area sensor in which a plurality of pixels are arranged two-dimensionally. However, when an area sensor is used, it takes a long time to read out information corresponding to each pixel. Therefore, it becomes difficult to proceed with measurement quickly.

  Therefore, in the present embodiment, by using the light receiving elements 31 arranged one-dimensionally so that a plurality of elongated pixels PE extending in the X direction are arranged in the Y1 direction, the reflected light from the workpiece W is reliably obtained. While receiving light, it becomes possible to proceed with measurement quickly with high accuracy.

  Note that the length of each pixel PE, the number of pixels PE, and the like may be appropriately changed according to the ratio between the light scanning width and the measurement range of the height of the workpiece W.

The length of each pixel PE is preferably not less than 10 times and not more than 1000 times the width of each pixel PE. An exposure control signal ECL is given to the plurality of pixels PE. The exposure start timing and end timing are controlled by the exposure control signal ECL. The charge accumulated in each pixel PE during exposure is transferred to the shift register SR simultaneously with the end of exposure.

  The shift register SR temporarily stores the charges transferred from each pixel PE. An output start signal RPL is given to the shift register SR. In response to the output start signal RPL, the charges stored in the shift register SR are sequentially output as the light reception signal RCL.

  In this embodiment, a light receiving element in which a plurality of elongated pixels PE extending in the X direction are arranged one-dimensionally is used. However, using a light receiving element in which pixels are arranged two-dimensionally, the Y1 direction is used. Needless to say, light reception signals (charges) in a direction orthogonal to the direction may be added and output.

(6) Adjustment method of exposure time Next, the adjustment method of the exposure time T is demonstrated in detail. FIG. 8 is a diagram for explaining a method for adjusting the exposure time T in a common light projecting direction. Here, a case will be described in which the set value of the exposure time T is adjusted to a different value at time points t21, t22, and t23 in FIG.

  As shown in FIG. 8, at time points t21, t22, and t23, the light scanning position in the X direction coincides with the position P12. In this case, the exposure starts from a time t21a before the time t21, and the exposure ends at a time t21b after the time t21. Similarly, exposure starts from time t22a before time t22, and exposure ends at time t22b after time t22. In addition, exposure is started from time t23a before time t23, and exposure is ended at time t23b after time t23. Hereinafter, the length of the period from time t21a to t21b is referred to as exposure time T1, the length of the period from time t22a to t22b is referred to as exposure time T2, and the length of the period from time t23a to t23b is referred to as exposure time T3.

  The exposure time T2 is longer than the exposure time T1, and the exposure time T3 is shorter than the exposure time T1.

  In the present embodiment, the light projection direction (light scanning position in the X direction) coincides with a predetermined direction at an intermediate time point between the start time point and the end time point of exposure (hereinafter referred to as an exposure intermediate time point). The start time and end time of exposure are adjusted. That is, the length of the period from time t21a to t21 and the length of the period from time t21 to t21b are adjusted to be equal, the length of the period from time t22a to t22 is adjusted to be equal to the length of the period from time t22 to t22b, and time t23a The length of the period of t23 and the length of the period of time t23 to t23b are adjusted equally.

  In this way, the exposure time T is increased or decreased based on the exposure intermediate time point. Thereby, the height of the surface at a desired position on the workpiece W can be accurately measured. The reason is as follows.

  The light scanning position in the X direction moves from position P12a to position P12b from time t21a to time t21b, moves from position P12c to position P12d from time t22a to time t22b, and from time t23a to time t23b. To the position P12f from the position P12e.

  In this case, the average value of the height in the path from the position P12a to the position P12b is obtained as a measurement result in the period from the time point t21a to t21b. Similarly, the average value of the height in the path from the position P12c to the position P12d is obtained as a measurement result in the period from the time point t22a to t22b, and the measurement result in the period from the time point t23a to t23b is obtained from the position P12e to the position P12f. The average height in the path is obtained.

  Here, in the present embodiment, the intermediate position between position P12a and position P12b, the intermediate position between position P12c and position P12d, and the intermediate position between position P12e and position P12f substantially coincide with position P12.

  Therefore, for example, even if the surface of the workpiece W is inclined from the position P12a to the position P12b, the average height from the position P12a to the position P12b substantially matches the height of the position P12. That is, the height of the position P12 can be obtained as a measurement result in the period from the time point t21a to t21b. Similarly, the height of the position P12 can be obtained as the measurement result in the period from time t22a to t22b and the measurement result in the period from time t23a to t23b. Thereby, even if the exposure time T increases or decreases, the height of the surface at a desired position can be stably obtained as a measurement result.

  On the other hand, for example, when exposure is started when the light scanning position in the X direction matches a predetermined position and the exposure time T is increased or decreased by moving the exposure end time back and forth, the light scanning position at the exposure start time And the scanning position of the light at the end of exposure vary as the exposure time T increases or decreases. Thereby, the surface height at the desired position cannot be obtained stably.

  Therefore, the height of the surface at a desired position on the workpiece W can be accurately measured by increasing or decreasing the exposure time T with reference to the exposure intermediate point.

(7) Relationship Between Exposure Time and Output Time Next, the relationship between the exposure time T and the light reception signal output time will be described.

  In the conventional light receiving element, the exposure end timing or start timing is determined in advance, and the output time of the light receiving signal is controlled so as to be synchronized with the timing. Specifically, when the exposure end timing is determined in advance, the output of the received light signal is started simultaneously with the end of exposure. In addition, when the exposure start timing is determined in advance, the output time is controlled so that the output of the light reception signal is completed simultaneously with the start of exposure.

  In the present embodiment, as described above, the exposure start timing and end timing are controlled so that the light projection direction coincides with a predetermined direction at the exposure intermediate point. Therefore, both the exposure start timing and end timing change in accordance with the surface state of the workpiece. In this case, if the exposure time T and the light reception signal output time are synchronized as described above, the following problem occurs.

  FIG. 9 is a diagram for explaining problems in the case where the exposure time and the output time of the received light signal are controlled by the conventional method.

  In the example of FIG. 9, the light receiving element 31 is exposed during a period from time t51 to t52, a period from time t53 to t54, and a period from time t55 to t56. The charges accumulated in each pixel PE (FIG. 7) of the light receiving element 31 during the exposure are transferred to the shift register SR simultaneously with the end of the exposure. Immediately after the charge is transferred from each pixel PE to the shift register SR, the output of the light reception signal RCL is started.

  That is, in the example of FIG. 9, the output of the light reception signal RCL (reading of the light reception signal RCL by the waveform generation unit 6) is started simultaneously with the end of the exposure of the light receiving element 31. Specifically, the output of the light reception signal RCL corresponding to the charge accumulated in the period from the time t51 to t52 is started from the time t52, and the output of the light reception signal RCL corresponding to the charge accumulated in the period from the time t53 to t54. Is started from time t54, and the output of the light reception signal RCL corresponding to the electric charge accumulated in the period from time t55 to time t56 is started from time t56.

  In this case, depending on the length of each period to be exposed (exposure time T), the output time of the light reception signal RCL corresponding to the charge accumulated in the previous period and the light reception signal corresponding to the charge accumulated in the subsequent period. The RCL output time may overlap. In the example of FIG. 9, the period from time t53 to t54 is relatively long, and the period from time t55 to t56 is relatively short. As a result, the output time of the light reception signal RCL corresponding to the charge accumulated during the period of time t53 to t54 and the output time of the light reception signal RCL corresponding to the charge accumulated during the period of time t55 to t56 partially overlap. ing. If the output times overlap in this way, a normal light reception signal RCL cannot be output.

  Therefore, in the present embodiment, the output start timing of the light reception signal RCL is controlled separately from the exposure start and end timing by the output signal RPL. As a result, even when both the exposure start timing and end timing change, overlapping of the output time of the light reception signal RCL as shown in FIG. 9 is prevented.

  FIG. 10 is a diagram showing a method for controlling the exposure time and the light reception signal output time in the present embodiment. FIG. 10 shows the relationship between the exposure time T and the output time at time points t11 to t31 in FIG.

  In the example of FIG. 10, the light receiving element 31 is exposed in a period from time t11a to t11b, a period from time t21a to t21b, and a period from time t31a to t31b. An intermediate time between the time t11a and the time t11b is a time t11, an intermediate time between the time t21a and the time t21b is a time t21, and an intermediate time between the time t31a and the time t31b is a time t31.

  Further, the output start signal RPL controls the start timing of the light reception signal RCL separately from the exposure end timing, and the output of the light reception signal RCL is started at a constant cycle. Specifically, the light reception signal RCL is output at time t11d intermediate between time t11 and time t21, time t21d intermediate between time t21 and time t31, and time t31d intermediate between time t31 and time t32 (FIG. 5). Is started.

  In this case, the output of the light reception signal RCL corresponding to the electric charge accumulated in each pixel PE at the previous exposure is started before the start of the next exposure. That is, the output of the light reception signal RCL corresponding to the charge accumulated during the period of time t11a to t11b is started from time t11d, and the output of the light reception signal RCL corresponding to the charge accumulated during the period of time t21a to t21b is output at time t21d. The light reception signal RCL corresponding to the electric charge accumulated during the period from time t31a to time t31b is output from time t31d.

  As described above, the output start timing of the light reception signal RCL is controlled separately from the exposure start and end timings, thereby preventing the output times of the light reception signal RCL in the preceding and following periods from overlapping. Further, it is possible to read out the light reception signal RCL at the time of the previous exposure and the next exposure in parallel. By such parallel processing, high-speed processing is realized.

(8) Other Embodiments The light projecting element 21 is not limited to a laser diode, and other elements such as an LED (light emitting diode) can also be used. The light receiving element 31 is not limited to a CMOS sensor, and other elements such as a CCD (charge coupled device) sensor can also be used. The scanning unit 23 is not limited to a galvano scanner, but may be a MEMS (micro electro mechanical system), a polygon mirror, a tuning fork, or other optical elements.

(9) Correspondence between each component of claim and each part of embodiment The following describes an example of the correspondence between each component of the claim and each part of the embodiment. It is not limited.

  In the above embodiment, the light projecting element 21 is an example of a light generation unit, the scanning unit 23 is an example of an optical scanning unit, the waveform generation unit 6 is an example of a waveform data generation unit, the FB control unit 7, The light projection control unit 3 and the light reception control unit 4 are examples of control means, the X direction is an example of the first direction, and the Y1 direction is an example of the second direction.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

  The present invention can be effectively used for measuring the cross-sectional shape of an object.

DESCRIPTION OF SYMBOLS 1 Light projection part 2 Light reception part 3 Light projection control part 4 Light reception control part 6 Waveform generation part 7 FB control part 21 Light projection element 23 Scanning part 31 Light reception element 100 Optical displacement meter PE Pixel W Workpiece

Claims (7)

A light generating section for generating light;
Light scanning means for scanning light on the surface of an object by controlling a light projection direction of the light generated by the light generation unit;
A condensing optical system for condensing the reflected light from the object;
A light receiving device that has a plurality of pixels disposed on a light collecting surface of the light collecting optical system and outputs a light receiving signal indicating a light receiving amount distribution corresponding to a position of a light collecting spot that varies depending on a distance to an object. Elements,
A waveform data generator for amplifying a light reception signal output from the light receiving element to generate waveform data;
The light emission intensity of the light generator and the exposure time of the light receiving element are controlled on the basis of the setting value of the light emission intensity by the light generator and the exposure time of the light receiving element for each light projecting direction by the light scanning means. Control for adjusting the set value of the emission intensity and the set value of the exposure time for each light projection direction by the optical scanning means so that the peak level of the waveform data generated by the waveform data generation unit falls within a predetermined range. Means and
The optical displacement meter, wherein the control means preferentially adjusts the set value of the emission intensity over the set value of the exposure time. The control means adjusts the setting value of the exposure time in addition to the setting value of the emission intensity when the peak level cannot be adjusted to the predetermined range even if the setting value of the emission intensity is adjusted. The optical displacement meter according to claim 1. The control unit further controls the amplification factor of the waveform data generation unit based on a set value of the amplification factor of the waveform data generation unit for each light projection direction by the optical scanning unit, and is generated by the waveform data generation unit. 3. The optical displacement meter according to claim 1, wherein the set value of the amplification factor is adjusted for each light projection direction by the optical scanning unit so that a peak level of the waveform data is within a predetermined range. 4. The optical displacement meter according to claim 3, wherein the control means preferentially adjusts the set value of the amplification factor over the set value of the exposure time. 5. The optical displacement meter according to claim 3, wherein the control means preferentially adjusts the set value of the emission intensity over the set value of the amplification factor. The position of the focused spot changes along the first direction according to the distance to the object,
The plurality of pixels of the light receiving element are arranged to be aligned along the first direction,
The length of each of the plurality of pixels in a second direction orthogonal to the first direction is larger than the length of each of the plurality of pixels in the first direction. The optical displacement meter according to any one of 5. The length of each of the plurality of pixels in the second direction is 10 to 1000 times the length of each of the plurality of pixels in the first direction. Optical displacement meter.

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