JP2006292729A - Displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement sensor that can measure the surface of a transparent body at all times, without having to depend on the difference of reflectivity between the surface and backside of the transparent body. <P>SOLUTION: The displacement sensor includes a light projection means for projecting a line beam directed toward a predetermined measuring object area; a two-dimensional imaging device for imaging the measuring object area from the angle that is different from the projection angle of the line beam; a measuring means for measuring the displacement of an object in the measuring object area, on the basis of the output of the two-dimensional imaging device; a measuring object area setting means that can set the measuring object areas more than two in the visual field of the two-dimensional imaging device; a measuring point coordinate decision means for determining at least one measuring point coordinate, included in the set measuring object area, on the basis of the image taken by the two dimensional imaging device; and an automatic area tracking means for tracking the variation of the measuring displacement on the reference plane of a measuring object and for moving at least one measuring object area terminal in the displacement measuring direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a displacement sensor, and in particular, a displacement suitable for measuring a gap between a glass substrate used for a flat panel display (hereinafter referred to as FPD) and a photomask used for exposure processing on the glass substrate. It relates to sensors.

  The displacement sensors are roughly classified into a one-dimensional displacement sensor and a two-dimensional displacement sensor. The former uses a spot beam as a measurement medium, and the latter uses a line beam as a measurement medium. Nowadays, the latter is becoming the mainstream.

  More specifically, the two-dimensional displacement sensor uses light emitted from a light source such as a laser diode as a line beam using a slit, and irradiates the measurement target object with the line beam. As a result, an irradiation light image corresponding to the surface shape or properties is displayed on the measurement target object (regardless of whether the view is approved or not). That is, for example, when the surface of the measurement target object (including the back surface in the case of a transparent body) is a flat surface without unevenness, a linear irradiation light image equivalent to a line beam appears on the measurement target object surface. On the other hand, if there are irregularities in the irradiation area of the line beam, a non-linear irradiation light image appears. Therefore, the irradiation light image appearing on the surface of the measurement target object is picked up by the two-dimensional image sensor, and the light receiving area (coordinates) in the two-dimensional image sensor is detected, so that the distance from the light source to the measurement target object, the measurement target object Various values such as surface properties, displacement amounts, and thicknesses can be measured.

  One of the uses of such a two-dimensional displacement sensor is to measure a gap between a glass substrate used for FPD and a glass photomask used when exposure processing is performed on the glass substrate. When performing exposure processing, multiple displacement sensors are deployed and arranged on the same plane so that the glass substrate and the photomask are parallel, and multiple such that the gap between the photomask and the glass substrate falls within a predetermined numerical range. Gaps are measured at this point. The glass substrate subjected to the exposure process has various conditions for each substrate such as the thickness of the substrate and the type of the resist solution applied to the surface, and the intensity of reflected light also differs for each substrate. Therefore, in a two-dimensional displacement sensor used for gap measurement between a glass substrate used for FPD and a glass photomask used when performing exposure processing on the glass substrate, the light receiving sensitivity adjustment in the measurement region is acquired. In general, the measurement is automatically performed for each region so that the measured optical image can be measured with appropriate sensitivity. When automatic sensitivity adjustment is performed, if there is only one light image in the area, the sensitivity is adjusted appropriately to measure that light image, and if there are multiple light images in the area, The light receiving sensitivity is adjusted based on the light image having the largest received light amount or the light image satisfying an arbitrary condition.

As a displacement sensor used for this type of application, the applicant has previously proposed a displacement sensor described in International Publication No. 01/57471 (Patent Document 1). The displacement sensor described in Patent Document 1 is characterized in that the user can arbitrarily designate a light reception presence / absence detection target region (substantial measurement region) in the two-dimensional image sensor. In this displacement sensor, a rough light-receiving area is predicted in advance and a substantial measurement area in the two-dimensional image sensor is limited, so that a detection process for areas other than the substantial measurement area is not required. As compared with the displacement sensor, a remarkable effect is obtained that the response speed is dramatically improved.
International Publication No. 01/57471 Pamphlet

  However, even with the above displacement sensor, the light reception sensitivity adjustment of each measurement region is generally performed automatically for each region, and when a plurality of light images are detected in one region, the light reception amount is the largest. There is a possibility that the light receiving sensitivity is adjusted based on a large light image, and the target light image cannot be detected.

  For example, when both the optical image on the glass substrate surface (small amount of received light) and the optical image on the back surface of the glass substrate (large amount of received light) are included in the region where the optical image of the glass substrate is measured, the light received in this region In general, the sensitivity is adjusted based on the amount of light received on the back surface of the glass substrate. If there is a large difference between the received light amount of the glass substrate surface light image and the received light amount of the glass substrate back surface light image, the received light amount of the glass substrate surface light image is too small as a result of adjusting the sensitivity based on the glass substrate back surface light image. May become undetectable. In this case, the glass substrate surface light image necessary for the gap measurement is not measured, and instead, the light image on the back surface of the glass substrate in the region is erroneously recognized as the surface light image. Since the thickness of the glass substrate is much larger than the gap ΔG between the photomask and the glass substrate when performing the exposure process, the glass substrate approaches the photomask if the glass substrate surface light image and the back surface light image are mistaken.・ Accidents such as contact may occur.

  As a solution to this problem, in the area where the optical image of the glass substrate is measured, the optical image closest to the photomask among the optical images contained in the area is recognized as the measurement object, and the other optical images are detected. A method of setting not to be considered is conceivable. However, if the substrate is set in this way, a “most photomask-side” light image cannot be specified in the case of a substrate in which a photomask back light image is not detected, which causes a problem in measurement.

  Moreover, although the said patent document 1 describes the displacement sensor which tracks the image of the imaged reflective surface and moves measurement object area | region itself, when two or more measurement object area | regions are provided, it is an area | region which does not move And the area to be moved are mixed, the above-mentioned problem occurs when these areas overlap each other.

  The present invention has been made in view of the above problems, and its object is to provide a displacement sensor that can always measure the surface of a transparent body regardless of the difference in reflectance between the surface and the back surface of the transparent body. Is to provide.

  Still other objects and effects of the present invention will be easily understood by those skilled in the art from the following description in the specification.

  In order to achieve the above-described object, the displacement measuring method of the present invention is arranged so that one surface of the first transparent plate is fixed so as to be included in the measurement target region, and is opposed to the surface. The second transparent plate is approached from a position that is more than or equal to the distance, and the beam is irradiated toward the measurement target region, and the measurement target region is imaged by the imaging element from an angle different from the beam irradiation angle. A method of measuring a displacement based on an optical image of a reflection surface of the transparent plate that reflects the beam and a reflection surface of the second transparent plate that reflects the beam, wherein the first measurement is performed prior to the measurement of the displacement. The measurement target region is set within a field of view of the imaging element, and a range in which a light image of the reflection surface by one surface of the first transparent plate can be captured, and the second measurement target region is set by the second transparent plate. In a state where it exists at a position more than a predetermined distance facing one surface Is set to a range that does not include the optical image of the reflecting surface of the second transparent plate that is far from the first transparent plate, and that does not overlap the first measurement target region, thereby measuring displacement. , While the second transparent plate is approached from a position away from the reflecting surface of the first transparent plate by a predetermined distance or more, a beam is irradiated toward the measurement target region and repeated imaging is performed by the imaging device. , For each second imaging target area, the position of the end on the opposite side of the first measuring target area with respect to the direction of the arrangement of the optical images of the reflecting surfaces in the first and second measuring target areas is determined. And tracking the light image of the reflecting surface existing in the second measurement target area so as to be within a certain range with reference to the optical image of the reflecting surface, and the sensitivity of the first and second measurement target areas in each measurement target area The reflection surface image with the largest received light amount or a predetermined condition Based on the received light amount of the selected reflective surface image, the measurement point coordinates are determined and determined from the optical image of the reflective surface of the target object existing in each measurement target area obtained by adjusting the sensitivity. Based on the measured measurement point coordinates, the displacement of the reflection surface in the first measurement target region and the displacement of the reflection surface in the second measurement target region are measured.

  The “predetermined condition” is a reflective surface that exists in the measurement target area and is commonly used for displacement measurement performed during the work of bringing the second reflector to the first reflector once. Is a predetermined condition for selecting.

  Further, the gap for calculating the displacement of the reflection surface in the first measurement target region, the displacement of the reflection surface of the second measurement target region and the shell, and the distance between the first transparent plate and the second transparent plate. Can be measured.

  According to such a method, it is possible to measure the displacement of the reflecting surface of the transparent plate approaching the fixed transparent plate and the gap between the two regardless of the difference in reflectance between the front surface and the back surface of the transparent body. is there.

  Preferably, within a certain range based on the optical image of the reflection surface existing in the region that follows the end of the second measurement target region, the light on the reflection surface in the first and second measurement target regions With respect to the direction in which the images are arranged, it is larger than the width of the optical image on the reflecting surface and smaller than the interval in the field of view of the image sensor corresponding to the thickness of the second transparent plate.

  According to this method, the displacement can be stably measured for one surface of the moving second transparent body.

  Preferably, the second transparent plate is approached from outside the field of view of the image sensor.

  According to this method, since the two surfaces of the second transparent plate do not exist in the second subtotal region, the measurement target region is placed on the surface far from the first transparent plate. There is no risk of incorrect settings.

  Preferably, the beam is a line beam. The second transparent plate is a glass substrate used for FPD (flat panel display), and the first transparent plate is a mask glass used for exposure processing.

  The displacement sensor according to the present invention is based on a light projecting unit that irradiates a beam toward a predetermined measurement target region, an image sensor that images the measurement target region from an angle different from the beam irradiation angle, and an output of the image sensor. Measurement means for measuring the displacement of an object in the measurement target area, measurement target area setting means for setting two or more measurement target areas in the field of view of the image sensor, and an image captured by the image sensor Based on the measurement point coordinate determining means for determining one or two or more measurement point coordinates included in the set measurement target region based on the measurement displacement variation on the reflection surface of the measurement target object, the measurement is performed. A region automatic tracking means for moving at least one measurement target region end of the measurement target region including the reflecting surface of the measurement target object whose displacement varies in the direction of variation of the measurement displacement, Has at least a first measurement target region and a second measurement target region, and the first measurement target region is set for a reflecting surface fixed in the field of view of the image sensor, and the measurement displacement is For the reflecting surface of the measurement target object that fluctuates, a second measurement target region is set in a range other than the first measurement target region so as to include the reflection surface. The end of the second measurement target area on the opposite side of the first measurement target area is moved with respect to the direction of the arrangement of the optical images of the reflecting surfaces in the first and second measurement target areas.

  According to such a configuration, it is possible to provide a displacement sensor capable of measuring the reflective surface of the transparent plate that is brought close to the fixed transparent plate regardless of the difference in reflectance between the front surface and the back surface of the transparent body.

  Preferably, the coordinates of the end of the second measurement target region on the first measurement target region side in the direction of the measurement displacement within the field of view of the imaging device are measured for the image included in the first measurement target region. Set based on the point coordinates and image the coordinates of the end opposite to the first measurement target area in the direction of the measurement displacement in the field of view of the second measurement target area imaging element in the second measurement target area. Is not included, one end in the direction of measurement displacement in the field of view of the image sensor is set as the end, and when the second measurement target region includes an image, the second The end point is set based on the measurement point coordinates of the image included in the measurement target region.

  According to such a configuration, by configuring the first measurement target region for the image included in the initial state, the first measurement region is automatically generated without any special operation by the operator. It becomes possible and operation becomes easier. Further, when the transparent body is measured in the second measurement target region, it is possible to surely enter the measurement region one side at a time.

  Furthermore, according to such a configuration, it is possible to temporarily set the second measurement region based on the image in the first measurement region even when the second measurement region does not include a reflective surface. Become. In addition, when the second measurement area includes a reflecting surface, the end point coordinates are set based on the image in the second measurement area, so that it is possible to set coordinates more suited to the state. Become.

  Preferably, when the displacement of the reflection surface included in the second measurement target region is measured, the second measurement target is based on the measurement point coordinates of the reflection surface included in the second measurement target region. Reset the coordinates of the end point of the area

  According to such a configuration, since the second measurement area end point coordinate is appropriately changed according to the displacement of the image in the second measurement area, it is possible to set the area according to the situation even when the reflecting surface moves. It becomes.

  Preferably, when an image is included in the second measurement target region, it is set based on the measurement point coordinates of the image included in the second measurement target region, or in the second measurement target region The distance from the measurement point coordinate to the end of the second measurement target region in which the coordinates of the second measurement target region end point are reset based on the measurement point coordinates of the included image is smaller than the thickness of the glass substrate.

  By this method, it becomes possible to always measure only the surface of the glass substrate, and there is no problem caused by measuring the back surface of the glass substrate.

  Preferably, it can be suitably used for measurement of a gap between a glass substrate used for FPD (flat panel display) and a mask glass used for exposure processing for the glass substrate. Also, the beam can be a line beam.

  As is clear from the above configuration, according to the present invention, since the measurement target region end point is determined by the measurement point coordinates in the measurement target region, the transparent body is always independent of the difference in reflectance between the front and back surfaces of the transparent body. It is possible to provide a displacement sensor that can measure the surface of the sensor.

  Hereinafter, a preferred embodiment of a displacement sensor of the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is merely an example of the present invention, and the gist of the present invention is defined only by the description of the scope of claims.

  The displacement sensor of the present embodiment is a so-called so-called signal processing unit and sensor head unit separated in order to enable compact accommodation in a control panel or the like and to facilitate installation in a narrow measurement environment. This is an amp-separated displacement sensor.

  An external perspective view of a signal processing unit of the displacement sensor of the present embodiment is shown in FIG. The outer shell case 10 of the signal processing unit 1 has a slightly elongated rectangular parallelepiped shape. An external connection cord 11 is drawn out from the front surface of the outer shell case 10. The external connection cord 11 includes an external input line, an external output line, a power supply line, and the like. The external input line is for giving various commands from the outside to the signal processing unit 1 from, for example, a PLC (Programmable Logic Controller) as a host device, and the external output line is generated inside the signal processing unit 1. The switching output and the analog output are output to the PLC and the like, and the power supply line is for supplying power to the internal circuit of the signal processing unit. A USB connector 12 and an RS-232C connector 13 are provided on the front surface of the outer shell case 10.

  An operation unit lid 14 that can be opened and closed is provided on the upper surface of the outer shell case 10. Although not shown, an operation unit for performing various command operations in the signal processing unit 1 is provided below the operation unit lid 14. Further, on the upper surface of the outer shell case 10, a display unit 15 for performing operation display and the like is disposed.

  On the left and right sides of the outer shell case 10, signal processing unit connector covers 16 are provided. Inside the signal processing unit connector lid 16, a signal processing unit connector (relay connector 3) for connecting another signal processing unit 1 is provided.

  FIG. 2 is an external perspective view showing a state in which a plurality of signal processing units 1 are connected. As shown in the figure, a plurality of signal processing units 1 are connected in a row in an adjacently coupled state via a DIN rail 4 in this example. A sensor head connector 17 is provided on the rear surface of the outer case 10 of the signal processing unit 1. The signal processing unit 1 is connected to the sensor head unit 2 described later via the sensor head unit connection connector 17.

  An external perspective view of the sensor head portion is shown in FIG. The sensor head unit 2 includes a signal processing unit connection connector 27 corresponding to the sensor head unit connection connector 17, a cable 21, and a sensor head body unit 20. Then, pulsed laser light emitted from a light projecting element (in this example, a laser diode) built in the main body 20 is irradiated as slit light L1 on the surface of the measurement target object 5 through a light projecting lens (not shown). . Thereby, an irradiation light image LI of the slit light is formed on the surface of the measurement target object 5. The reflected light L2 of the slit light reflected by the measurement target object 5 is received by a two-dimensional image sensor (CCD type, CMOS type, etc.) through a light receiving lens (not shown) in the sensor head unit 2. That is, the image signal including the irradiation light image LI of the slit light is acquired by photographing the surface of the measurement target object 5 from different angles with the two-dimensional image sensor. Based on this video signal, a predetermined feature amount is extracted, and a target displacement amount (in this example, a distance between the sensor head unit 2 and the measurement target object 5) is obtained.

  FIG. 4 is a block diagram showing the entire electrical hardware configuration of the signal processing unit 1 of the displacement sensor. As shown in the figure, the signal processing unit 1 includes a control unit 101, a storage unit 102, a display unit 103, a communication unit 104 with a sensor head unit, a communication unit 105 with an external device, and key input. Unit 106, external input unit 107, output unit 108, and power supply unit 109.

  The control unit 101 is composed of a CPU (Central Processing Unit) and an FPGA (Field Programmable Gate Array), and takes charge of overall control of the signal processing unit 1. The control unit 101 realizes various functions to be described later, binarizes the received light signal with a predetermined threshold as a reference, and sends this as output data from the output unit 108 to the outside. The storage unit 102 includes a nonvolatile memory (EEPROM) 102 a and an image memory 102 b that stores image data displayed on the display unit 103. The display unit 103 includes a liquid crystal display unit 103a on which various numerical values relating to a threshold value, a distance to a measurement target object, and the like are displayed, and an indicator LED 103b indicating an output state (on / off state) according to the measurement value. And. The communication unit 104 is responsible for communication with the sensor head unit 2. The external communication unit 105 includes a USB communication unit 105a for connecting to an external personal computer (PC) 110, a serial communication unit 105b used for transmission / reception of various commands and program data, and a predetermined protocol and transmission / reception format. An inter-signal processing unit communication unit 105c that performs data communication with the other adjacent left and right signal processing units is provided. The key input unit 106 includes switches and operation buttons for various settings (not shown). The external input unit 107 is for receiving various commands to the signal processing unit 1 from a host device such as a PLC. The output unit 108 is used to output an on / off output to a host device such as a PLC. The power supply unit 109 supplies power to the control unit 101 and an external hardware circuit.

  A block diagram showing the electrical hardware configuration of the sensor head unit 2 is shown in FIG. As shown in the figure, the sensor head unit 2 is reflected by the control unit 201, the light projecting unit 202 for irradiating slit light toward the measurement target object 5, and the measurement target object 5. A light receiving unit 203 that receives reflected light, an indicator LED 204, a storage unit 205, and a communication unit 206 are provided.

  The control unit 201 is configured by a CPU (Central Processing Unit) and a PLD (Programmable Logic Device), and plays a role of controlling the components 202 to 206 of the sensor head unit.

  In this example, the light projecting unit 202 includes a laser diode as a light projecting element and a light projecting circuit, and irradiates slit light toward the detection target region. The light receiving unit 203 receives a light reception signal obtained from the two-dimensional image pickup device in synchronization with a two-dimensional image pickup device (CCD type, CMOS type, etc.) that receives the reflected light of the slit light and a timing control signal from the control unit 201. A received light signal processing unit that amplifies and outputs the amplified signal to the control unit 201. The indicator LED 204 is turned on and off in response to various operating states of the sensor head unit 2. The storage unit 205 is composed of, for example, a non-volatile memory (EEPROM). In this example, an ID (identification information) for identifying the sensor head unit 2 is recorded. The communication unit 206 is responsible for communication with the signal processing unit 1 in accordance with instructions from the control unit 201. The sensor head unit 2 of the present embodiment has a circuit configuration as described above, and performs an appropriate light projecting / receiving process according to a command from the signal processing unit 1.

  An example schematically showing the gap measurement between the photomask and the glass substrate by the displacement sensor to which the present invention is applied is shown in FIG. In the figure, 61 is a sensor head of the displacement sensor, 62 is a photomask, 63 is a glass substrate, 63a is a planned movement position of the glass substrate, L3 is reflected light from the back surface of the photomask 62, and L4 is reflected from the glass substrate surface. Light, ΔG is a gap between the photomask 62 and the glass substrate 63. The photomask 62 has an exposure pattern drawn on the back surface (surface facing the glass substrate 63), and exposure processing (not shown) is performed on the glass substrate 63 from the surface side of the photomask 62 with an exposure device (not shown). Is performed, an exposure pattern corresponding to each glass substrate is used. On the other hand, a resist solution is applied to the front surface (surface facing the photomask) of the glass substrate 63, and exposure processing is performed through the photomask 62, so that the glass substrate 63 corresponds to the pattern on the back surface of the photomask 62. Are exposed. In this example, a plurality of displacement sensors may be used in accordance with the size of the glass substrate 63 and the gap between the photomask 62 and the glass substrate 63 may be measured at a plurality of locations. In this case, the exposure process may be set to be performed when the gaps at a plurality of locations are within a predetermined range so that the glass substrate 63 and the photomask 62 are close to each other at a constant interval.

  In this example, in the initial state before the measurement is started, the photomask 62 is in the measurement area of the displacement sensor, but the glass substrate 63 is outside the measurement area of the displacement sensor. When the measurement starts, the glass substrate 63 moves from the outside of the measurement area of the displacement sensor in the direction approaching the photomask 62, approaches the predetermined gap ΔG, and the glass substrate 63 is exposed through the photomask 62.

  An example in which the gap between the photomask and the glass substrate is measured with a conventional displacement sensor is shown in FIG. In the figure, area 0 is a region for measuring a photomask, area 1 is a region for measuring a glass substrate, 81 is a light image on the back surface of the photomask, 82 is a light image on the surface of the glass substrate, and 83 is a light image on the back surface of the glass substrate. , P1 is the peak of the reflected light on the glass substrate surface, and P2 is the peak of the reflected light on the back surface of the glass substrate. The heights P1 and P2 indicate the intensity of the reflected light. In this example, two light images of a glass substrate front surface light image 82 and a glass substrate back surface light image 83 are included in the area 1, and the glass substrate back surface reflected light is higher in intensity than the glass substrate front surface reflected light. As described above, in this type of displacement sensor, when there are multiple light images in an area, the sensitivity is automatically adjusted based on the light image having the highest intensity in the area. Is. Therefore, in this example, since P1 <P2, the light receiving sensitivity of area 1 is automatically adjusted based on the glass substrate back surface light image 83. In this way, when multiple peaks are included in one area, if there is a large difference in the intensity of multiple peaks, other peaks will not be detected if the reception sensitivity is determined based on one peak. Or may be saturated. That is, in such a conventional displacement sensor, when the gap between the photomask and the glass substrate is measured, the peak on the glass substrate surface << the peak on the back surface of the glass substrate, the peak on the glass substrate surface is not detected. As a result, a trouble that the photomask and the glass substrate approach and contact each other may occur.

  FIG. 7 shows an explanatory diagram of detection region end automatic tracking when the gap between the photomask and the glass substrate is measured by the displacement sensor to which the present invention is applied. In the figure, area 0 is a region for measuring a photomask, area 1 is a region for measuring a glass substrate, 71 is a light image on the back surface of the photomask, 72 is a light image on the glass substrate surface, 73 is a light image on the back surface of the glass substrate, ΔG1 to G3 are distances between the back surface of the photomask and the glass substrate surface, ΔE is the distance from the glass substrate surface to the end of area 1, ΔD is the thickness of the glass substrate, and ΔZ is a predetermined distance from the glass substrate surface and smaller than ΔD. Value. In this example, in any of FIGS. 7A to 7C, the position of the photomask in area 0 does not move, and the optical image 71 on the back surface of the photomask does not move. On the other hand, the position of the glass substrate in area 1 moves in the order of (a), (b), and (c) in the direction approaching the photomask, and the distances ΔG1 to ΔG3 between the photomask and the glass substrate are ΔG1> ΔG2. > ΔG3.

  First, in FIG. 7A, the glass substrate surface light image 72 is immediately after entering the area 1 from the terminal side (in the figure, the right end side of the area 1). It is preferable that the area 1 is set wide to some extent in the initial state so as to easily capture the light image on the surface of the glass substrate. The area width of the area 1 may be appropriately set in consideration of the thickness of the glass substrate and the like, but it is necessary that the glass substrate surface light image 72 does not enter the area 1 in the initial state. The glass substrate surface is outside the area 1 at the start of measurement, and enters the area 1 from the end side. At this time, the distance ΔE between the glass substrate surface light image 72 and the end point of the area 1 is a value smaller than a predetermined value ΔZ, that is, ΔE <ΔZ. When the distance ΔE between the glass substrate surface light image 72 and the end point of the area 1 is smaller than the predetermined value ΔZ, the end point may not be adjusted, and the area 1 may be expanded so that ΔE = ΔZ. . In a state immediately after the glass substrate front surface light image 72 enters the area 1, the glass substrate back surface light image 73 is outside the area 1 area.

  Next, in FIG. 7B, the glass substrate is closer to the photomask than in FIG. 7A, and the distance ΔE = ΔZ between the glass substrate surface light image 72 and the end point of the area 1 is set. When ΔE ≧ ΔZ, the end point E of area 1 moves following the glass substrate surface light image 72 so that ΔE = ΔZ. Since ΔZ is a fixed value smaller than the thickness ΔD of the glass substrate, as long as the distance ΔE between the glass substrate surface light image 72 and the area week end point is smaller than ΔZ (that is, when ΔE ≦ ΔZ), ΔD> ΔZ Since ΔZ ≧ ΔE, the relationship of ΔD> ΔZ ≧ ΔE always holds, and the distance ΔE between the glass substrate surface light image 72 and the end point of the area 1 is always smaller than the thickness ΔD of the glass substrate, and the back surface of the glass substrate The optical image 73 is outside the area 1 area.

  In FIG. 7C, the glass substrate is closer to the photomask side than the time of FIG. 7B, but the end point E is the glass substrate so that it is away from the glass substrate surface light image 72 by a fixed value ΔZ. Since it follows the surface light image 72, ΔE = ΔZ is always maintained, and the glass substrate back surface light image 73 is always outside the area 1 and is not measured (recalculation so that ΔE = ΔZ. And the end point is reset). As described above, in the displacement sensor to which the present invention is applied, the termination point E follows the glass substrate surface light image 72 at a predetermined distance ΔZ (glass substrate thickness ΔD> ΔZ). 73 does not enter the area 1, and there is no problem that may occur when the glass substrate back surface light image 73 enters the area 1 and is measured.

In the displacement sensor to which the present invention is applied, a general flowchart showing a procedure for determining a measurement region is shown in FIG. 9, and an explanatory diagram corresponding to the flow of FIG. 9 is shown in FIG. In the figure, A, B, Z (x), P (z), ΔZ1, ΔZ2, ΔZ, ΔG, and ΔdAB are as follows.
A: CCD light receiving position on the back of the photomask, unit (pix)
B: CCD light receiving position on the glass substrate surface, unit (pix)
Z (x): Conversion formula from CCD light receiving position (pix) to distance value (mm) P (z): Conversion formula from distance value (mm) to CCD light receiving position (pix) ΔZ1: For measurement value of area 0 Offset value ΔZ2 to area 1 start point: Offset value to area 1 end point with respect to area 0 measurement value ΔZ: Fixed value to area 1 end point with respect to area 1 measurement value ΔG: Photomask for performing exposure processing Distance ΔdAB between light receiving position A on the back surface and light receiving position B on the glass substrate surface: Distance between light receiving position A on the back surface of the photomask and light receiving position B on the glass substrate surface

  Waiting until the measurement area setting process start signal is received (step 901, step 902 NO), and when the start signal indicating that the measurement area determination process is performed is received (step 902 YES), an image of area 0 is acquired and the light receiving position A Based on the position information, area temporary setting processing for area 1 is performed (YES in step 903, step 905). In this example, the position of the photomask measured in area 0 is fixed. If no image is detected in area 0 in step 903 (NO in step 903), an error is determined and error processing is performed (step 904). As error processing, for example, steps 901 to 903 may be repeated until an image is detected in area 0, or a guide sentence is given so that the user is notified that no image is detected in area 0 and some processing is performed. May be set to be displayed.

The area temporary setting process in step 905 will be described with reference to FIG. When an image is detected in area 0 (step 903 YES in FIG. 9), the light receiving position A of the acquired image is detected (step 9051), and the measurement area of area 1 is provisionally determined based on the information on the light receiving position A (step 9052). ). Here, the start position and end position of the area 1 which is the measurement area are obtained by the following equations from the position information of the light receiving position A and the predetermined offset values ΔZ1 and ΔZ2, respectively.
Start position: P (Z (A) + ΔZ1)
End position: P (Z (A) + ΔZ2)
ΔZ1 and ΔZ2 that determine the start position, end position, and area width of area 1 are appropriately determined in view of the thickness of the glass substrate and the like.

  When the start position and end position of area 1 are provisionally determined by the above formula (step 9052), the area temporary setting process is performed based on the information, and the start position and end position of area 1 are set (step 9053).

  Returning to FIG. 9, when the temporary setting process for area 1 is completed (step 905), the process waits until an image is detected in area 1 (step 906, step 907 NO). If an image is detected in area 1 (YES in step 907), the process proceeds to a resetting process for area 1 (step 908).

The area reset processing in step 908 will be described with reference to FIG. When an image is detected in area 1 (YES in step 907 in FIG. 9), the light receiving position B of the acquired image is detected (step 9081), and the measurement area of area 1 is determined again based on the information on the light receiving position B (step 9082). ). Here, the start position and the end position of the area 1 which is the measurement area are obtained by the following equations from the position information of the light receiving position A and the position information of the light receiving position B, predetermined offset values ΔZ1, ΔZ2, and a fixed value ΔZ, respectively.
Start position: P (Z (A) + ΔZ1)
End position: P (Z (B) + ΔZ)
ΔZ1, ΔZ2, and ΔZ that determine the start position, end position, and area width of area 1 are appropriately determined in view of the thickness of the glass substrate and the like.

  When the start position and end position of area 1 are determined again according to the above formula (step 9082), the area temporary setting process for area 1 is performed based on the information (step 9083).

  Returning to FIG. 9, when the area 1 resetting process is completed (step 908), it is determined whether or not the gap between the light receiving position A and the light receiving position B has reached the specified value ΔG (step 909). If the specified value ΔG has not been reached (NO in step 909), the position of the workpiece B is adjusted again (step 910), and steps 908 to 910 are performed until the gap between the light receiving position A and the light receiving position B reaches the specified value ΔG. repeat. When the gap between the light receiving position A and the light receiving position B reaches the specified value ΔG (step 909 YES), the glass substrate is subjected to an exposure process and the process is terminated (step 911).

  A timing chart showing the sensitivity adjustment processing for each region is shown in FIG. As shown in the figure, in the displacement sensor of this embodiment, when one or two or more measurement target areas are set within the field of view of the two-dimensional CCD, an optical image of a beam irradiation point in each measurement target area. Therefore, the density is always automatically adjusted to a density suitable for measurement.

  That is, in FIG. 13, as clearly shown by comparing the column of the VD signal shown in (a) with the column of region setting shown in (b), the regions 1 and 1 are alternately arranged in successive vertical periods. Switching to the region 0, the light receiving sensitivity is controlled in a time-sharing manner. As a result, when there are two video peaks in the field of view of the two-dimensional CCD, and one of them is extremely larger or smaller than the other, the automatic sensitivity adjustment function by this time division switching works, At any peak, measurement point coordinate determination processing can be performed with an appropriate concentration.

  That is, in the example of FIG. 13, the image included in the region 0 is insufficient in density, but as a result of sequential density automatic adjustment, when the density is increased to an appropriate density, the measurement point coordinates are calculated using feature calculation. Is extracted. On the other hand, since the image included in the region 1 has an appropriate density from the beginning, the measurement point coordinates are determined as it is based on this. In the displacement sensor of the present application, since the density automatic adjustment is performed for each region in this way, measurement point coordinates are determined at an appropriate density in any image, and based on this, a target measurement (for example, This makes it possible to measure the thickness of transparent bodies.

  FIG. 14 shows a timing chart showing a process for causing the set area to follow the vertical fluctuation of the measurement point. In the present invention, the measured value on the surface of the glass substrate is constantly monitored, and when the fluctuation occurs, the end point of the measurement area is controlled to follow the distance of ΔZ according to the fluctuation amount. Let That is, as shown in FIG. 13, in this embodiment, the range of the region 1 is recalculated based on the position information of the light image on the surface of the glass substrate in the region 1, and the region range is changed based on the result. Since the range of the region 1 is changed as the position of the glass substrate changes, the reflected light on the back surface of the glass substrate is always outside the region 1, and the measurement can be avoided by the optical image on the back surface of the glass substrate. .

  Next, FIG. 15 is a block diagram schematically showing the internal configuration of the controller of the displacement sensor to which the present invention is applied. In the figure, 1501 is a sensor head, 1502 is a controller, 1503 is an A / D converter, 1504 is an area determination unit, 1505 is an image memory, 1506 is a display composition unit, 1507 is a D / A converter, 1508 is displacement, A density extraction unit, 1509 is a console interface, 1510 is an external I / O interface, 1511 is a memory, 1512 is a CPU, 1513 is an area setting unit, 1514 is a calculation unit, and 1515 is a sensitivity determination unit. The calculation unit 1514 incorporates various calculation functions such as pixel / mm conversion calculation, measurement processing calculation, pass / fail determination calculation, and display processing calculation.

  The CPU 1512 is configured mainly with a microprocessor, and in this example, three functions of an area setting unit 1513, a calculation unit 1514, and a sensitivity determination unit 1515 are realized in software. The region setting unit 1513 has a function of setting a measurement target region in the field of view of the two-dimensional CCD constituting the sensor head unit 1501 in response to a predetermined operation of the console interface 1509. This measurement target area limits the image of the area to be measured among all images taken by the two-dimensional CCD. The measurement target region set by the region setting unit 1513 is notified to the region determination unit 1504 and used here as a reference for the region determination processing.

  On the other hand, the region determination unit 1504 selectively gates the digital video signal sent from the sensor head 1501 via the A / D converter 1503 corresponding to the region set by the region setting unit 1513. It becomes. That is, when one or more set measurement target areas exist in the list, only the pixel output sequence of the measurement target area is extracted by passing the digital video signal at the timing of those measurement target areas. Thus, an extracted image is generated. The extracted image thus obtained is sent from the area determination unit 1504 to the image memory 1505 and temporarily stored in the image memory 1505.

  The extracted image stored in the image memory 1505 is combined with the graphic image indicating the boundary line of the measurement target region sent from the region setting unit 1513 in the display combining unit 1506, and the combined image obtained in this way is the D / D. The raw image data sent to the image monitor via the A converter 1507 and photographed by the two-dimensional CCD and masked by the area determination unit 1504 on the screen (not shown) of the image monitor, and the density of each display line It is displayed together with a line bright waveform indicating the distribution (luminance distribution). This display mode will be described in detail later with reference to the screen explanatory diagram.

  As described above, in the displacement sensor in this embodiment, the light projecting means including the laser diode for forming the measurement light spot on the measurement target object and the measurement target object on which the light spot is formed are set at a predetermined angle. A light receiving means including a two-dimensional CCD for photographing from the above, and an arithmetic means for calculating a target displacement based on one information of a light spot image in an image obtained from the light receiving means.

  In addition, based on comparison between the extracted image feature and a predetermined reference value, the feature extraction unit extracts an image feature correlated with the magnitude of the video signal of the light spot image from the image obtained from the light receiving unit. And a control means for controlling the magnitude of the video signal of the light spot image used for the displacement calculation calculation to an appropriate state by operating the light projection gain adjustment element of the light projection means and / or the light reception gain adjustment element of the light reception means. It has.

  An example of screen display when setting the thickness of the glass substrate in the displacement sensor to which the present invention is applied is shown in FIGS. The setting procedure will be described in detail with reference to FIGS.

  First, FIG. 16A shows a menu screen at the start of setting. In this example, the application options are “surface displacement”, “spot displacement”, “maximum height”, “groove, dent”, “step”, “transparent thickness”, “step (2 sensors)”, “thickness” The item “(2 sensors)” is shown. In FIG. 16A, “transparent thickness” is selected from these items, and the corresponding display is made on the right side of the screen.

  When “Transparent thickness” is selected, the screen of FIG. 16B is displayed. In the upper half of the screen, a light image 1601 on the transparent body surface and a light image 1602 on the back surface of the transparent body are displayed, and a guide sentence is displayed, “Specifying measurement area on front surface”. First, in order to designate the measurement region of the surface light image of the transparent body, the cursor 1603 is set in accordance with the surface light image 1601 to perform designation processing. When the measurement area on the front surface is designated, the screen shown in FIG. 17A is displayed in order to designate the measurement area on the back surface, and a guide sentence “Please make only two surfaces within the measurement area” is displayed. As in the case of the front surface, the cursor 1603 is placed on the transparent rear surface light image 1602 and a designation process is performed.

  When the measurement area designation of the front and back surfaces of the transparent body is completed, the screen of FIG. 17B is displayed, and a processing procedure for correcting the refractive index is shown. In the figure, a guide sentence “Please input the measured value of point 1” is displayed. When the measured value of point 1 is input as specified, the screen of FIG. 18A is then displayed and a guide sentence “Please enter the distance between the two points” is displayed. As in the previous case, enter the distance between the two points, and proceed to the next step.

  Finally, the screen of FIG. 18B is displayed for confirmation, and an item name and an option of whether or not to register this setting are presented. When registering as it is, “Register” is selected, “Return” is selected when correction is desired, and “Cancel” is selected when canceling the setting itself.

  An example of the screen configuration of the displacement sensor to which the present invention is applied is shown in FIG. In the figure, reference numeral 1901 denotes an area 0 in which a light image on the back side of the photomask is displayed, 1902 denotes an area 1 in which a light image on the surface of the glass substrate is displayed, 1903 denotes a light image on the back side of the photomask, and 1904 denotes a light image on the surface of the glass substrate. 1905 is a line bright display on the back side of the photomask, 1906 is a line bright display on the surface of the glass substrate, 1907 is the light sensitivity of area 0 and the peak value of the light image in area 0, 1908 is the light sensitivity of area 1 and in area 1 The peak values of the optical images are respectively shown.

  As described above with respect to one embodiment of the present invention, the displacement sensor of the present invention can completely eliminate the influence of the light image on the back surface of the transparent body with a simple operation, and can be applied to various applications. is there. For example, in the embodiment, the line beam is irradiated, but when the spot beam is irradiated instead of the line beam, the other parts remain in the same configuration or are replaced with the two-dimensional image sensor. Displacement measurement is also possible by using.

It is an external appearance perspective view of a signal processing part. It is an external appearance perspective view of the continuous state of a signal processing part. It is an external appearance perspective view of a sensor head part. It is a block diagram which shows the electrical hardware constitutions of a signal processing part. It is a block diagram which shows the electrical hardware constitutions of a sensor head part. It is the figure which showed the gap measurement of a photomask and a glass substrate. It is an example of the gap measurement by the displacement sensor to which this invention was applied. It is an example of the gap measurement by the conventional displacement sensor. It is a general flowchart which shows the procedure which determines a measurement area | region in the displacement sensor to which this invention was applied. It is a flowchart which shows the step 905 area | region temporary setting process of FIG. 9 in detail. 10 is a flowchart showing in detail a step 908 area resetting process in FIG. 9. It is explanatory drawing of an area | region setting process procedure. It is a timing chart which shows the sensitivity adjustment process according to area | region. It is a timing chart which shows the process which makes a setting area follow the up-and-down fluctuation of a measurement point. It is a block diagram which shows roughly the internal structure of the controller of the displacement sensor to which this invention was applied. It is an example (the 1) of a screen display at the time of setting the thickness of a glass substrate. It is an example (the 2) of a screen display at the time of setting the thickness of a glass substrate. It is an example (the 3) of a screen display at the time of setting the thickness of a glass substrate. It is an example of the screen structure of the displacement sensor to which this invention was applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal processing part 2 Sensor head part 3 Relay connector 4 DIN rail 5 Object to be detected 10 Outer shell case 11 External connection cord 12 USB connector 13 RS-232C connector 14 Operation part cover 15 Display part 16 Signal processing part connector cover 17 Sensor Connector for head unit 20 Sensor head body unit 21 Cable 27 Connector for signal processing unit connection 101 Control unit 102 Storage unit 102a Non-volatile memory 102b Image memory 103 Display unit 103a Liquid crystal display unit 103b Indicator LED
104 Communication Unit with Sensor Head 105 Communication Unit with External Device 105a USB Communication Unit 105b Serial Communication Unit 105c Signal Processing Unit Communication Unit 106 Key Input Unit 107 External Input Unit 108 Output Unit 109 Power Supply Unit 110 External Personal Computer 201 Control Unit 202 Light Emitting Unit 203 Light Receiving Unit 204 Indicator LED
205 Storage Unit 206 Communication Unit 61 Sensor Head Unit 62 Photomask 63 Glass Substrate 63a Planned Movement Position of Glass Substrate 71 Optical Image on the Back Side of Photomask 72 Optical Image on the Front Side of Glass Substrate 73 Optical Image on the Back Side of Glass Substrate 81 Light on the Back Side of Photomask Image 82 Optical image of glass substrate surface 83 Optical image of glass substrate back surface 1501 Sensor head 1502 Controller 1503 A / D converter 1504 Area determination unit 1505 Image memory 1506 Display composition unit 1507 D / A converter 1508 Displacement and density extraction unit 1509 Console interface 1510 External I / O interface 1511 Memory 1512 CPU
1513 Area setting unit 1514 Calculation unit 1515 Sensitivity determination unit 1601 Light image on transparent body surface 1602 Light image on transparent body back surface 1603 Cursor 1901 Area 0
1902 Area 1
1903 Light image on the back side of the photomask 1904 Light image on the surface of the glass substrate 1905 Line bright display on the back side of the photomask 1906 Line bright display on the surface of the glass substrate 1907 Light reception sensitivity of area 0 and peak value of the light image in area 1 1908 Photosensitivity and peak value of light image in area 1 L1 Irradiation light image L2 Reflected light L3 Reflected light from photomask back surface L4 Reflected light from glass substrate surface P1 Peak of glass substrate surface reflected light P2 Glass substrate back surface reflected light peak

Claims (12)

While fixing and arranging one surface of the first transparent plate so as to be included in the measurement target region, while making the second transparent plate approach from a position separated from the predetermined distance by facing the surface, A beam is irradiated toward the measurement target region, the measurement target region is imaged by an imaging device from an angle different from the beam irradiation angle, and the reflection surface of the first transparent plate that reflects the beam and the second A method of measuring displacement based on an optical image of a reflecting surface that reflects the beam of a transparent plate,
Prior to measuring displacement,
Setting the first measurement target region within the field of view of the imaging device to a range in which a light image of the reflecting surface by one surface of the first transparent plate can be captured;
In a state where the second measurement target region is present at a position where the second transparent plate is separated from the first surface by a predetermined distance or more, the second measurement target region is located with respect to the first transparent plate of the second transparent plate. A range that does not include the optical image of the reflection surface by the surface on the far side, and a range that does not overlap with the first measurement target region,
In measuring displacement,
While approaching the second transparent plate from a position away from a predetermined distance facing the reflecting surface of the first transparent plate, the image sensor repeatedly irradiates a beam toward the measurement target region,
For each imaging, the position of the end of the second measurement target region on the side opposite to the first measurement target region with respect to the alignment direction of the optical images of the reflection surfaces in the first and second measurement target regions is determined. , To follow the light image of the reflecting surface existing in the second measurement target region to be within a certain range with reference to,
The sensitivity of the first and second measurement target regions is automatically adjusted based on the light reception amount of the reflection surface image having the largest light reception amount existing in each measurement target region or a reflection surface image selected according to a predetermined condition, Measurement point coordinates are determined from the light images of the reflecting surfaces of the objects present in the respective measurement target areas obtained by adjusting the sensitivity, and the first measurement target area is determined based on the determined measurement point coordinates. Displacement measuring method for measuring the displacement of the reflecting surface and the displacement of the reflecting surface of the second measurement target region.   From the displacement of the reflecting surface in the first measurement target region and the displacement of the reflecting surface in the second measurement target region obtained by the method according to claim 1, the first transparent plate and the second transparent plate A gap measurement method that calculates the distance to the plate.   Within a certain range based on the optical image of the reflecting surface existing in the region that follows the end of the second measuring target region, the optical image of the reflecting surface in the first and second measuring target regions The displacement measuring method according to claim 1, wherein the arrangement direction is larger than the width of the optical image of the reflecting surface and smaller than the interval in the field of view of the imaging device corresponding to the thickness of the second transparent plate.   The displacement measuring method according to claim 1, wherein the second transparent plate is approached from outside the field of view of the image sensor.   The displacement measuring method according to claim 1, wherein the beam is a line beam.   The gap measurement according to claim 2, wherein the second transparent plate is a glass substrate used for an FPD (flat panel display), and the first transparent plate is a mask glass used for exposure processing. Method. A light projecting means for irradiating a beam toward a predetermined measurement target area;
An image sensor that images the measurement target region from an angle different from the beam irradiation angle;
Measuring means for measuring the displacement of the object in the measurement target region based on the output of the image sensor;
Measurement target area setting means capable of setting two or more measurement target areas in the field of view of the image sensor;
Measurement point coordinate determining means for determining one or more measurement point coordinates included in the set measurement target region based on an image captured by the image sensor;
Following the variation of the measurement displacement on the reflective surface of the measurement target object, one measurement target region end of the measurement target region including the reflection surface of the measurement target object where the measurement displacement fluctuates in the variation direction of the measurement displacement A region automatic tracking means to be moved, and
The measurement target area has at least a first measurement target area and a second measurement target area, and the first measurement target area is set for a reflective surface that is fixed in the field of view of the image sensor, For the reflection surface of the measurement target object whose measurement displacement fluctuates, the second measurement target region is set in a range other than the first measurement target region so as to include the reflection surface,
The area automatic tracking means moves the end of the second measurement target area on the opposite side of the first measurement target area with respect to the arrangement direction of the optical images of the reflecting surfaces in the first and second measurement target areas. A displacement sensor. Based on the measurement point coordinates of the image included in the first measurement target region, the coordinates of the end of the second measurement target region on the first measurement target region side in the direction of the measurement displacement within the field of view of the imaging device. Set,
The coordinates of the end of the second measurement target region opposite to the first measurement target region in the direction of the measurement displacement in the field of view of the image sensor,
If no image is included in the second measurement target region, one end in the direction of measurement displacement in the field of view of the image sensor is set as the end,
The end point is set based on the measurement point coordinates of the image included in the second measurement target region when the second measurement target region includes an image. Displacement sensor.   When the displacement of the image included in the second measurement target region is measured, the coordinates of the second measurement target region end point are determined based on the measurement point coordinates of the image included in the second measurement target region. The displacement sensor according to claim 8, wherein the displacement sensor is reset.   8. A target displacement measurement target is a gap between a glass substrate used for an FPD (flat panel display) and a mask glass used for exposure processing on the glass substrate. The displacement sensor according to any one of 9.   When an image is included in the second measurement target area, it is set based on the measurement point coordinates of the image included in the second measurement target area, or is included in the second measurement target area. The coordinates of the second measurement target region end point are reset based on the measurement point coordinates of the obtained image, and the distance from the measurement point coordinate to the end point of the second measurement target region is smaller than the thickness of the glass substrate. The displacement sensor according to claim 8 or 9, characterized in that:   The displacement sensor according to claim 7, wherein the beam is a line beam.

Images