Shape measuring device and method for calibrating shape measuring device

Abstract

A shape measuring device of the present invention comprises an image processing unit in which, in the case of measurement, a plate-shaped measurement target is disposed between an illumination unit and an imaging unit and the contour shape of the measurement target is determined on the basis of a shadow image of the measurement target generated by imaging the shadow of the measurement target formed by the illumination light emitted from the illumination unit by the imaging unit. In the case of calibration, a dimming filter unit is disposed between the illumination unit and the imaging unit, and the quantity of illumination light emitted from the illumination unit is calibrated on the basis of the received light quantity received by the imaging unit through a dimming filter unit 2.

Description

Shape measuring device and method for calibrating shape measuring device

[0001] The present invention relates to a shape measuring device that measures the contour shape of a plate-shaped measurement target using illumination light, and a method for calibrating the shape measuring device.

[0002] Conventionally, as disclosed in Patent Document 1, for example, a shape measuring device is known that irradiates a parallel light beam through a measurement object toward an image sensor and measures the shape of the measurement object using an image of the measurement object projected onto the image sensor.

[0003] However, when the object to be measured is a long component in the direction of travel of the collimated light, diffraction fringes may occur. When diffraction fringes occur, the image of the object to be measured and the diffraction fringes appear in the image, resulting in an error in the shape of the measurement results. For this reason, it is conceivable to make the background of the image white by saturating the amount of light received by the image sensor. However, this method exceeds the dynamic range of the image sensor, and therefore the amount of collimated light cannot be adjusted to a set value based on the output of the image sensor, making calibration impossible.

[0004] Japanese Patent Application Laid-Open No. 2006-145487

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a shape measuring device capable of calibrating the amount of light and a method for calibrating a shape measuring device.

[0006] The shape measurement device and its calibration method according to the present invention are an apparatus and a calibration method thereof, which include an image processing unit that, during measurement, places a plate-shaped measurement object between an illumination unit and an imaging unit, and determines the contour shape of the measurement object based on a shadow image of the measurement object generated by imaging the shadow of the measurement object formed by illumination light irradiated from the illumination unit using the imaging unit, and wherein, during calibration, a neutral density filter unit is placed between the illumination unit and the imaging unit, and the amount of illumination light irradiated from the illumination unit is calibrated based on the amount of light received by the imaging unit via the neutral density filter unit 2.

[0007] These and other objects, features and advantages of the present invention will become apparent from the following detailed description and accompanying drawings.

[0008] FIG. 1 is a block diagram showing the configuration of a shape measuring device in an embodiment. FIG. 2 is a diagram for explaining a retracted position of a neutral density filter in the shape measuring device. FIG. 3 is a diagram for explaining a calibration position of a neutral density filter in the shape measuring device. FIG. 4 is a diagram for explaining, as an example, a contour shape measured by the shape measuring device. FIG. 5 is a flowchart showing the operation of the shape measuring device regarding calibration. FIG. 6 is a diagram for explaining a shape measuring device of a third modified embodiment. FIG. 7 is a diagram for explaining a measurement object measured by the shape measuring device of the third modified embodiment. FIG. 8 is a diagram for explaining, as an example, a contour shape measured by the shape measuring device of the third modified embodiment.

[0009] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In addition, components with the same reference numerals in each drawing indicate the same components, and their description will be omitted as appropriate. In this specification, when referring to a general term, a reference numeral without a subscript is used, and when referring to an individual component, a reference numeral with a subscript is used.

[0010] The shape measurement device in this embodiment includes an illumination unit, an imaging unit, and an image processing unit that, during measurement, a plate-shaped measurement target is placed between the illumination unit and the imaging unit, and that determines the contour shape of the measurement target based on a shadow image of the measurement target generated by the imaging unit capturing a shadow of the measurement target formed by illumination light irradiated from the illumination unit. During calibration, the shape measurement device also includes a neutral density filter unit placed between the illumination unit and the imaging unit, and a calibration unit that calibrates the amount of illumination light irradiated from the illumination unit based on the amount of light received by the imaging unit via the neutral density filter unit. The following describes in more detail such a shape measurement device and a calibration method for a shape measurement device implemented therein.

[0011] Fig. 1 is a block diagram showing the configuration of a shape measuring device according to an embodiment. Fig. 2 is a diagram for explaining a retracted position of a neutral density filter in the shape measuring device. Fig. 3 is a diagram for explaining a calibration position of the neutral density filter in the shape measuring device. Fig. 4 is a diagram for explaining, as an example, a contour shape measured by the shape measuring device.

[0012] The shape measuring device 1000 includes, for example, a first contour shape measuring unit 1, a first neutral density filter unit 2, a control processing unit 3, an input unit 4, an output unit 5, an interface unit (IF unit) 6, and a memory unit 7, as shown in Figures 1 to 3.

[0013] The first contour shape measuring unit 1 is an apparatus including an illumination unit, an imaging unit, and an image processing unit. In the case of measurement, a plate-shaped measurement object WA is placed between the illumination unit and the imaging unit. The image processing unit captures a shadow image of the measurement object WA formed by illumination light emitted from the illumination unit. The image processing unit calculates the contour shape of the measurement object WA based on the shadow image of the measurement object WA. More specifically, in this embodiment, the first contour shape measuring unit 1 measures the contour shape of the measurement object WA based on a shadow image captured by irradiating the peripheral portion of the measurement object WA with light from a tangential direction of the outer periphery. The measurement object WA is, for example, a disk-shaped member. The contour shape is the thickness direction contour shape of the disk-shaped member (the outer contour shape as viewed from a horizontal direction (side) perpendicular to the normal direction of the disk) measured based on the thickness direction shadow image SWA, as shown in FIG. 4 . The measurement object WA is placed on a rotary stage (turntable) not shown, and the first contour shape measuring unit 1 uses the rotary stage to sequentially rotate the measurement object WA at predetermined angular intervals (sampling intervals) and measures each contour shape viewed from the side at each measurement location (sampling point) in the circumferential direction. The first contour shape measuring unit 1 includes, for example, a first measurement unit 11 and a first shape calculation unit 12 (32).

[0014] The first measurement unit 11 is connected to the control processing unit 3 and, under the control of the control processing unit 3, generates a shadow of the peripheral portion of the measurement object WA by irradiating the peripheral portion with light from a tangential direction of the outer periphery, and captures an image of the generated shadow of the peripheral portion. As shown in FIGS. 2 and 3 , the first measurement unit 11 includes an illumination unit (first illumination unit) 111, an illumination optical system 112, a light-receiving optical system 113, and an image capture unit 114. The first illumination unit 111 is connected to the control processing unit 3 and emits illumination light under the control of the control processing unit 3, and is configured with a light source such as a white light-emitting diode. The illumination optical system 112 collimates the illumination light irradiated (radiated) from the first illumination unit 111 into parallel light, and is configured with, for example, one or more lenses. The light-receiving optical system 113 forms an optical image of a shadow of the peripheral portion of the measurement object WA, which is generated by irradiating the peripheral portion with the parallel illumination light, on the imaging surface (light-receiving surface) of the imaging unit 114, and is configured, for example, with one or more lenses. The imaging unit 114 is connected to the control processing unit 3 and converts the optical image of the shadow of the peripheral portion formed on the imaging surface into an electrical signal under the control of the control processing unit 3, and is configured, for example, with a CCD area image sensor or a CMOS area image sensor. The imaging unit 114 outputs data obtained by this imaging (shadow data) to the control processing unit 3. The first illumination unit 111, illumination optical system 112, light-receiving optical system 113, and imaging unit 114 are arranged in this order so that their optical axes coincide with each other.

[0015] In this embodiment, the first shape calculation unit 12 (32) is functionally configured in the control processing unit 3 as described later, and performs image processing (first image processing) on ​​the output (the shadow data) of the imaging unit 114 to generate shadow image data that is data representing an image of the shadow of the peripheral portion (shadow image), and performs image processing (second image processing) on ​​the generated shadow image data to determine the contour shape of the measurement object WA. The second image processing includes a second image processing step that extracts edges using an edge filter such as a Sobel filter, a second image processing step that removes noise from the edges extracted in the second image processing using a preset brightness threshold, and a third image processing step that obtains, in subpixel units, a curve that fits to the edges after noise removal in the second image processing as the shadow contour shape.

[0016] In this embodiment, in order to remove the influence of diffraction fringes by making the background of the image white by saturating the amount of light received by the image sensor, the first illumination unit 111 irradiates illumination light with an amount of light of a preset value SV that exceeds the dynamic range DR of the area image sensor in the imaging unit 114. If the dynamic range DR of the area image sensor in the imaging unit 114 is 0≦DR≦DRu, then DRu<SV.

[0017] The first neutral density filter unit 2 is a device that is disposed between the illumination unit 111 and the imaging unit 114 during calibration, and that reduces (dims) the amount of incident light before emitting it. More specifically, in this embodiment, the first neutral density filter unit 2 includes a neutral density filter 21 and a movement driver 22, as shown in FIGS. 2 and 3 .

[0018] The neutral density filter (ND filter) 21 is an optical element that reduces (dims) the amount of incident light before it is emitted. Any optical filter can be used as the neutral density filter 21 as long as it can reduce the amount of incident light. For example, the neutral density filter 21 can be an optical filter in which a metal thin film is laminated on a glass substrate, an optical filter in which a light-absorbing material is mixed into a glass substrate or a resin substrate, a so-called frosted glass optical filter, or an optical filter in which a dielectric multilayer film is laminated on a glass substrate. The neutral density filter 21 may or may not have a wavelength-dependent light blocking range, and it is sufficient if it can attenuate the wavelength of the illumination light emitted from the first illumination unit 111. The transmittance RV (0≦RV≦1), which is the ratio of transmitted light to incident light in the neutral density filter 21, is appropriately set so that in the case of measurement, the amount of light of a set value SV that exceeds the dynamic range DR of the area image sensor in the imaging unit 114 is reduced to the amount of light within the dynamic range DR of the area image sensor in the case of calibration (0≦SV×RV≦DR).

[0019] The movement driver 22 is connected to the control processor 3 and is a device that moves the neutral density filter 21 between a calibration position and a retracted position under the control of the control processor 3. The calibration position is a position where the neutral density filter 21 is disposed between the first illumination unit 111 and the image capture unit 114, as shown in FIG. 3 , and is the position where the neutral density filter 21 is located during calibration. The retracted position is a position where the neutral density filter is not disposed between the first illumination unit 111 and the image capture unit, as shown in FIG. 2 , and is the position where the neutral density filter 21 is located during measurement. That is, the calibration position is a position where the illumination light emitted from the first illumination unit 111 is received by the image capture unit 114 via the neutral density filter 21, and the retracted position is a position where the illumination light emitted from the first illumination unit 111 is received by the image capture unit 114 without passing through the neutral density filter 21. In the case of calibration, the measurement object WA may or may not be placed, but this measurement object WA that is not placed is shown by a dashed line in Fig. 3. By superimposing the measurement object WA shown in Fig. 2 on the measurement object WA shown by the dashed line in Fig. 3, the calibration position and the retracted position can be compared, and the difference between these positions can be recognized.

[0020] The movement drive unit 22 may be any device capable of moving the neutral density filter 21 between the calibration position and the retracted position. For example, a hydraulic cylinder, an electric cylinder, or the like may be used for the movement drive unit 22. In this embodiment, an electric cylinder 22 is used for the movement drive unit 22, and the neutral density filter 21 is attached to its piston rod 22a. Alternatively, a so-called rack-and-pinion may be used for the movement drive unit 22. The neutral density filter 21 is attached to the rack, and the pinion is driven by a motor. In the above description, the neutral density filter 21 is moved between the calibration position and the retracted position on a linear trajectory. However, the neutral density filter 21 may also be moved between the calibration position and the retracted position on a curved trajectory. In this case, for example, the retracted position is set to a position rotated 90 degrees clockwise or counterclockwise from the calibration position, and the movement drive unit 22 is configured to include, for example, a reducer and a motor for rotating the neutral density filter 21.

[0021] The input unit 4 is connected to the control processing unit 3 and is a device that inputs various commands, such as a command to start measurement, and various data required to operate the form measuring device 1000, such as the name of the object to be measured, to the form measuring device 1000, and is, for example, a keyboard, a mouse, and a plurality of input switches to which predetermined functions are assigned. The output unit 5 is connected to the control processing unit 3 and is a device that outputs the commands, data, contour shapes, etc. input from the input unit 4 under the control of the control processing unit 3, and is, for example, a display device such as a CRT display, LCD (liquid crystal display), or organic EL display, or a printing device such as a printer.

[0022] The input unit 4 and the output unit 5 may be configured as a touch panel. In this touch panel configuration, the input unit 4 is a position input device, such as a resistive or capacitive type, that detects and inputs an operation position, and the output unit 5 is a display device. In this touch panel, a position input device is provided on the display surface of the display device, and one or more input content candidates that can be input are displayed on the display device. When a user touches the display position showing the input content they want to input, the position is detected by the position input device, and the display content displayed at the detected position is input to the shape measurement device 1000 as the user's operation input content. Such a touch panel makes it easy for the user to intuitively understand input operations, providing a shape measurement device 1000 that is easy for the user to use.

[0023] The IF unit 6 is connected to the control processing unit 3 and is a circuit that inputs and outputs data to and from, for example, an external device under the control of the control processing unit 3, and is, for example, an interface circuit for RS-232C, which is a serial communication method, an interface circuit using the Bluetooth (registered trademark) standard, an interface circuit using the USB standard, etc. The IF unit 6 may also be, for example, a communication interface circuit that transmits and receives communication signals to and from an external device, such as a data communication card or a communication interface circuit conforming to the IEEE802.11 standard, etc.

[0024] The memory unit 7 is connected to the control processing unit 3 and is a circuit that stores various predetermined programs and various predetermined data under the control of the control processing unit 3. The various predetermined programs include, for example, a control processing program, which includes, for example, a control program, a first shape calculation program, a calibration program, and a movement control program. The control program is a program that controls each of the units 1, 2, 4 to 7 of the shape measurement device 1000 according to the function of each unit. The first shape calculation program is a program that generates the shadow image data by performing the first image processing on the shadow data output from the imaging unit 114 and then obtains the contour shape of the measurement object WA by performing the second image processing on the generated shadow image data. The calibration program is a program that calibrates the amount of illumination light emitted from the first illumination unit 111 based on the amount of light received by the imaging unit 114 via the neutral density filter unit 2. The movement control program is a program that controls the movement drive unit 22 of the neutral density filter unit 2 so that the neutral density filter 21 is positioned at the calibration position during calibration and at the retracted position during measurement.

[0025] The various types of predetermined data include, for example, the name of the object to be measured, the set value SV which is the target light intensity of the illumination light emitted from the first illumination unit 111, the light attenuation amount RV of the neutral density filter 21, the adjustment amount Δi for adjusting the current value during calibration, each data item and contour shape during information processing, and other data required for executing each of these programs. The set value SV and the adjustment amount Δi are set in advance as appropriate from, for example, a plurality of samples.

[0026] The storage unit 7 includes, for example, a ROM (Read Only Memory), which is a nonvolatile storage element, or an EEPROM (Electrically Erasable Programmable Read Only Memory), which is a rewritable nonvolatile storage element. The storage unit 7 also includes a RAM (Random Access Memory), which serves as a working memory for the control processing unit 3 and stores data generated during execution of the predetermined program. The storage unit 7 may also be configured with a hard disk drive having a relatively large storage capacity.

[0027] The control processing unit 3 is a circuit that controls each of the units 1, 2, 4 to 7 of the shape measuring device 1000 according to the function of each unit, and determines the contour shape of the measurement object WA. The control processing unit 3 is configured to include, for example, a CPU (Central Processing Unit) and its peripheral circuits. By executing the control processing program, the control processing unit 3 is functionally configured to include a control unit 31, a first shape calculation unit 32 (12), a calibration unit 33, and a movement control unit 34.

[0028] The control unit 31 controls each of the units 1, 2, 4 to 7 of the shape measuring device 1000 in accordance with the function of each unit, and is in charge of overall control of the shape measuring device 1000.

[0029] As described above, the first shape calculation unit 32 (12) generates the shadow image data by performing the first image processing on the shadow data output from the imaging unit 114, and then obtains the thickness-wise contour shape of the measurement object WA by performing the second image processing on the generated shadow image data.

[0030] The calibration unit 33 calibrates the amount of illumination light irradiated from the first illumination unit 111 based on the amount of light received by the imaging unit 114 via the neutral density filter 21 of the neutral density filter unit 2.

[0031] The movement control unit 34 controls the movement drive unit 22 of the neutral density filter unit 2 so that the neutral density filter 21 is positioned at the calibration position during calibration, and is positioned at the retracted position during measurement.

[0032] To explain the calibration in more detail, first, the movement control unit 34 controls the movement drive unit 22 to position the neutral density filter 21 at the calibration position. Next, the control unit 31 causes the first illumination unit 111 to emit illumination light by passing a current of a current value ic adjusted in the previous calibration (a default (initial) current value in the first calibration), and the emitted illumination light is received by the area image sensor of the imaging unit 114 via the neutral density filter 21. Within the range (light receiving range) of the area image sensor of the imaging unit 114 that receives the illumination light that has passed through the neutral density filter 21, a plurality of light receiving elements are set in advance for calculating the amount of received light MV. Next, the calibration unit 33 calculates the average value of the outputs from the multiple light receiving elements as the amount of received light MV, and adds the amount of light attenuation RV of the neutral density filter 21 to this calculated amount of received light MV to calculate the true amount of light TV (=MV+RV) of the illumination light emitted from the first illumination unit 111. Next, the calibration unit 33 compares this calculated true amount of light TV of the illumination light with the set value SV, and determines, for example, whether the true amount of light TV of the illumination light matches the set value SV within a predetermined range (margin). If they match, the calibration unit 33 ends the calibration process. On the other hand, if they do not match and the true light intensity TV of the illumination light is smaller than the set value SV, the current value ic is updated by adding the adjustment amount Δi to the current value ic (ic←ic+Δi), and if they do not match and the true light intensity TV of the illumination light is greater than the set value SV, the current value ic is updated by subtracting the adjustment amount Δi from the current value ic (ic←ic−Δi). With this updated current value ic, as described above, the following processes are performed: irradiation of the illumination light by the first illumination unit 111, reception of the illumination light by the area image sensor of the imaging unit 114, calculation of the true light intensity TV of the illumination light, comparison of the true light intensity TV of the illumination light with the set value SV, and updating of the current value ic according to the comparison result. This process is repeated until the comparison results match.Then, when the calibration process is completed, the calibration unit 33 stores the current value ic at that time in the memory unit 7 as the current value adjusted in the current calibration (if not updated, the current value ic adjusted in the previous calibration is stored in the memory unit 7 as the current value adjusted in the current calibration, and if updated, the updated current value ic is stored in the memory unit 7 as the current value adjusted in the current calibration). The movement control unit 34 controls the movement drive unit 22 to position the neutral density filter 21 at the retracted position.

[0033] The control processing unit 3, input unit 4, output unit 5, IF unit 6 and storage unit 7 can be configured by, for example, a desktop or notebook computer.

[0034] Next, the operation of this embodiment will be described with reference to the flowchart of FIG.

[0035] When the power is turned on, the shape measuring device 1000 having such a configuration initializes the necessary parts and starts its operation. The control processing unit 3 executes a control processing program to functionally configure a control unit 31, a first shape calculation unit 32 (12), a calibration unit 33, and a movement control unit 345.

[0036] For example, when the input unit 4 receives a command to start calibration, in FIG. 5, the shape measuring device 1000 controls the movement drive unit 22 by the movement control unit 34 of the control processing unit 3 to move the dimming filter 21 to the calibration position (S1).

[0037] Next, the shape measuring device 1000 causes the control unit 31 of the control processing unit 3 to emit illumination light from the first illumination unit 111 with a current of the current value ic stored in the memory unit 7, and receives this emitted illumination light via the neutral density filter 21 with the area image sensor of the imaging unit 114 (S2).

[0038] Next, the shape measuring device 1000 determines the amount of received light MV by the calibration unit 33 of the control processing unit 3 to determine the true amount of light TV (=MV+RV) of the illumination light (S3).

[0039] Next, the shape measuring device 1000 compares the true light quantity TV of the illumination light thus obtained with the set value SV by the calibration unit 33 (S4).

[0040] Next, the form measuring device 1000 determines whether the true light intensity TV of the illumination light matches the set value SV within the predetermined range as a result of the comparison using the calibration unit 33 (S5). If the result of the determination is that they do not match, the form measuring device 1000 next executes step S6, while if they match, the form measuring device 1000 next executes step S7.

[0041] In this process S6, the shape measuring device 1000, using the calibration unit 33, updates the current value ic by adding the adjustment amount Δi to the current value ic (ic←ic+Δi) if the true light intensity TV of the illumination light is smaller than the set value SV, and updates the current value ic by subtracting the adjustment amount Δi from the current value ic (ic←ic-Δi) if the true light intensity TV of the illumination light is greater than the set value SV, and then returns the process to process S2.

[0042] In step S7, the calibration unit 33 of the shape measuring device 1000 stores the current value ic at that time in the storage unit 7 as the current value adjusted by this calibration.

[0043] Then, the shape measuring device 1000 controls the movement driver 22 by the movement controller 34 of the control processor 3 to move the neutral density filter 21 to the retracted position (S8), and ends this process.

[0044] As described above, the shape measuring device 1000 in the embodiment and the calibration method for the shape measuring device implemented therein are equipped with a neutral density filter unit 2 that reduces the amount of incident light before emitting it. Therefore, even when calibration is performed by adjusting the amount of illumination light irradiated from the first illumination unit 111 to a set value SV that exceeds the dynamic range DR of the imaging unit 114, the amount of light can be calibrated by attenuating the light using the neutral density filter unit 2 so that it is within the dynamic range DR of the imaging unit 114.

[0045] According to this embodiment, a shape measuring device 1000 can be provided that calibrates the amount of illumination light irradiated from the first illumination unit 111 so that the amount of light received MV by the imaging unit 114 becomes a predetermined amount of light, for example, an amount of light that exceeds the dynamic range DR of the area image sensor in the imaging unit 114 and saturates the light receiving element.

[0046] The shape measuring device 1000 is equipped with a movement drive unit 22 that moves the attenuation filter 21 between the calibration position and the retracted position, so that the attenuation filter 21 can be automatically moved between the calibration position and the retracted position in the case of calibration and in the case of measurement.

[0047] In the above-described embodiment, the dimming filter 21 is moved between the calibration position and the retracted position by the moving drive unit 22, but a jig (mounting jig) for attaching and detaching the dimming filter 21 may be provided at the calibration position, and in the case of calibration, the dimming filter 21 may be attached to the mounting jig by the user (operator), and in the case of measurement, the dimming filter 21 may be removed from the mounting jig by the user (first variant).

[0048] Furthermore, in the above-described embodiment (including the first modified embodiment), the shape measurement device 1000 may further include an alarm unit 37 that issues an alarm to the outside when the current value i of the current flowing through the first illuminator 111 after calibration exceeds a predetermined threshold (alarm notification threshold) i.sub.th based on the maximum rated current value i.sub.max of the first illuminator 111 (second modified embodiment). For example, the control processing program may include a program stored in the storage unit 7 that issues an alarm to the outside when the current value i of the current flowing through the first illuminator 111 after calibration exceeds an alarm notification threshold i.sub.th based on the maximum rated current value i.sub.max of the first illuminator 111. By executing the control processing program, the alarm unit 37 is functionally configured in the control processing unit 3, as shown by the dashed line in FIG. 1. The alarm notification threshold i.sub.th is set appropriately to, for example, 85%, 90%, or 95% of the maximum rated current value i.sub.max. When the above-described process S7 is executed, the notification unit 37 determines whether the current value ic adjusted in the current calibration exceeds the alarm notification threshold i th, and if the result of this determination indicates that the current value ic exceeds the alarm threshold i th, the notification unit 37 outputs, as the alarm, a message urging replacement of the light source of the first illumination unit 111, such as "We recommend replacing the light source of illumination light," to the output unit 5. Alternatively, the alarm may be issued by, for example, turning on a warning light or emitting an alarm sound.

[0049] The amount of illumination light emitted from the first illumination unit 111 generally decreases over time. Because the amount of light increases as the amount of power supply increases, the current value ic of the current flowing through the first illumination unit 111 is increased at a constant voltage to compensate for the decreased amount of light. Consequently, the current value ic of the current flowing through the first illumination unit 111 eventually exceeds the maximum rated current value imax of the first illumination unit 111, causing the first illumination unit 111 to fail. In the shape measurement device 1000 of the second modified embodiment, an alarm is issued to the outside when the current value ic exceeds the alarm threshold ith. Therefore, it is possible to take action, such as replacing the light-emitting element of the light source, before the first illumination unit 111 fails.

[0050] Furthermore, in the above-described embodiments (including the first and second modified embodiments), the shape measuring device 1000 may be further configured such that the measurement object is a disc-shaped member and the shape measuring device 1000 measures the circumferential contour of the disc-shaped member, or the measurement object is a disc-shaped member having a notch formed at a predetermined position in the circumferential direction and the shape measuring device 1000 measures the contour of the notch (third modified embodiment). While either one of these may be further provided in the shape measuring device 1000, a more specific description will be given here of a case in which the shape measuring device 1000 is further provided with both of these.

[0051] Fig. 6 is a diagram for explaining a shape measuring apparatus of a third modified embodiment. Note that the first to third neutral density filter units 2, 42, and 52 are omitted from Fig. 6 and are not shown. Fig. 7 is a diagram for explaining a measurement target to be measured by the shape measuring apparatus of the third modified embodiment. Fig. 8 is a diagram for explaining, as an example, a contour shape to be measured by the shape measuring apparatus of the third modified embodiment.

[0052] The shape measuring device 1000 in this third modified form further includes a second contour shape measuring unit 41, a second neutral density filter unit 42, a third contour shape measuring unit 51, and a third neutral density filter unit 52, as shown by dashed lines in Figure 1.

[0053] The measurement object WAa here is, for example, a disk-shaped member with a substantially "V"-shaped notch NC formed at a predetermined position in the circumferential direction, as shown in Fig. 7. When the measurement object WAa is a semiconductor wafer, the notch NC indicates its crystal orientation.

[0054] The second contour shape measuring unit 41 is a device that measures the circumferential contour shape of the measurement object WAa (the outer contour shape as viewed from the normal direction of the disk), and is equipped with, for example, a second measuring unit 411 and a second shape calculation unit 412 (35).

[0055] The second measurement unit 411 is connected to the control processing unit 3 and is a device that measures the position of the peripheral edge of the measurement object WAa by irradiating the measurement object WAa with predetermined illumination light from the thickness direction of the measurement object WAa under the control of the control processing unit 3. The second measurement unit 411 measures each position of the peripheral edge at a plurality of different measurement points along the circumferential direction θ of the measurement object WAa.

[0056] 6, the second measurement unit 411 includes an illumination unit (second illumination unit) 4111 that irradiates the measurement object WAa with illumination light in a linear manner from the thickness direction along the radial direction, a light receiving unit 4112 that receives the illumination light irradiated from the second illumination unit 4111 through the measurement object WAa, and a holder 4113 that holds the second illumination unit 4111 and the light receiving unit 4112 so that they face each other with a predetermined gap between them. The second illumination unit 4111, holder 4113, and light receiving unit 4112 have a substantially U-shape (an E-shape with the central "-" removed) in side view. Therefore, the light receiving unit 412 is disposed opposite the second illumination unit 4111. The second illumination unit 4111 may include, for example, a device that converts light emitted from a light source into parallel light using a collimator lens, converts the parallel light into slit light that travels along the radial direction r through a slit hole in a plate-like member having a rectangular slit hole elongated in one direction, and irradiates the measurement object WAa with the slit light as the illumination light. The light-receiving unit 4112 may include, for example, a line sensor or area image sensor that is wider than the slit hole. In the second measurement unit 411 equipped with the second illumination unit 4111 and light-receiving unit 4112, the measurement object WAa is positioned relative to the second measurement unit 411 so that the radial direction r is aligned with the one direction. Alternatively, for example, the second illumination unit 4111 may be a device that irradiates the measurement object WAa with laser light emitted from a light source as the illumination light while scanning it in the radial direction r. The light-receiving unit 4112 may include, for example, a line sensor or area image sensor that is wider than the laser light. In the second measurement unit 411 equipped with such a second illumination unit 4111 and light receiving unit 4112, the measurement object WAa is disposed relative to the measurement unit 1 so that the radial direction r is along the scanning direction. The holding unit 4113 is, for example, a columnar member extending in one direction, and holds the second illumination unit 4111 and the light receiving unit 4112 at both ends of the columnar member so that they extend in a direction perpendicular to the one direction.

[0057] In this third modified embodiment, the second shape calculation unit 412 (35) is functionally configured in the control processing unit 3, and for each of the plurality of measurement locations, determines the position of the peripheral edge of the measurement object WAa at that measurement location based on the output of the light receiving unit 4112, and calculates the circumferential contour shape of the measurement object WAa based on the positions of the peripheral edge of the measurement object WAa determined at each of the plurality of measurement locations. Since the linear illumination light emitted from the second illumination unit 4111 is blocked by the measurement object WAa, for example, by determining pixels whose brightness is less than a predetermined threshold (a peripheral edge position determination threshold) and pixels whose brightness is equal to or greater than the peripheral edge position determination threshold, the position of the pixel where this brightness changes is determined as the position of the peripheral edge of the measurement object WAa, and the distance L1 from one end of the linear illumination light (the end closest to the center of the measurement object WAa) to the peripheral edge of the measurement object WAa is calculated. In principle, the distance L2 from the center of the rotation stage (the center of the measurement object WAa) to one end of the linear illumination light is known in advance, so by adding the distance L2 to the distance L1, the distance L3 (= L1 + L2) from the center of the measurement object WAa to the peripheral edge of the measurement object WAa can be calculated. By calculating this distance L3 for each of the multiple measurement points, the contour shape of the measurement object WAa in the circumferential direction can be calculated.

[0058] The second attenuation filter unit 42 is similar to the first attenuation filter unit 2, except that it is positioned relative to the second contour shape measurement unit 41 so that a calibration position is set between the second illumination unit 4111 and the light receiving unit 4112, and therefore its description will be omitted.

[0059] The calibration unit 33 further calibrates the amount of illumination light emitted from the second illumination unit 4111 based on the amount of received light received by the light receiving unit 4112 via the second neutral density filter unit 42. The calibration program further includes a program for calibrating the amount of illumination light emitted from the illumination unit 4111 based on the amount of received light received by the light receiving unit 4112 via the second neutral density filter unit 42.

[0060] The storage unit 7 stores, as a program included in the control processing program, a second shape calculation program for determining, for each of the plurality of measurement locations, the position of the peripheral edge of the measurement object WAa at that measurement location based on the output of the light receiving unit 4112, and for determining the circumferential profile shape of the measurement object WAa based on the positions of the peripheral edges of the measurement object WAa determined at each of the plurality of measurement locations. Execution of the control processing program functionally configures a second shape calculation unit 35 (412) in the control processing unit 3.

[0061] The third contour shape measuring unit 51 is a device that measures the contour shape of the notch NC in the measurement object WAa (the contour shape of the notch NC as viewed from the normal direction of the disk), and includes, for example, a third measurement unit 511 and a third shape calculation unit 512 (36). The third measurement unit 511 is similar to the first measurement unit 11 except that it irradiates light onto the peripheral portion of the measurement object WA from the thickness direction. That is, the third measurement unit 511 includes an illumination unit 5111 having an illumination unit and illumination optical system similar to the first illumination unit 111 and illumination optical system 112, and a light receiving unit 5112 having a light receiving optical system and image capturing unit similar to the light receiving optical system 113 and image capturing unit 114. The third shape calculation unit 512 (36) is similar to the first shape calculation unit 32 (12) except that it uses the output of the image capturing unit of the light receiving unit 5112, and therefore its description will be omitted.

[0062] The third attenuation filter section 52 is similar to the first attenuation filter section 2, except that it is positioned relative to the third contour shape measurement section 51 so that a calibration position is set between the illumination unit 5111 and the light receiving unit 5112, and therefore its description will be omitted.

[0063] The calibration unit 33 further calibrates the amount of illumination light emitted from the illumination unit 5111 based on the amount of received light of the illumination light emitted from the illumination unit and received by the light-receiving unit 5112 via the third neutral density filter unit 52. The calibration program further includes a program for calibrating the amount of illumination light emitted from the illumination unit 5111 based on the amount of received light of the illumination light emitted from the illumination unit and received by the light-receiving unit 5112 via the third neutral density filter unit 52.

[0064] The storage unit 7 stores a third shape calculation program similar to the first shape calculation program as a program included in the control processing program. Execution of the control processing program functionally configures a third shape calculation unit 36 ​​(512) in the control processing unit 3.

[0065] This specification discloses various aspects of the technology as described above, but the main technologies among them are summarized below.

[0066] One embodiment of the shape measuring device comprises an illumination unit, an imaging unit, and an image processing unit that, during measurement, a plate-shaped measurement object is placed between the illumination unit and the imaging unit, and that determines the contour shape of the measurement object based on a shadow image of the measurement object generated by the imaging unit capturing the shadow of the measurement object formed by the illumination light irradiated from the illumination unit. During calibration, the device comprises a neutral density filter unit that is placed between the illumination unit and the imaging unit, and a calibration unit that calibrates the amount of illumination light irradiated from the illumination unit based on the amount of light received by the imaging unit via the neutral density filter unit.

[0067] Such a shape measuring device is equipped with a neutral density filter unit that reduces the amount of incident light before emitting it. Therefore, even when calibration is performed by adjusting the amount of illumination light emitted from the illumination unit to a set value that exceeds the dynamic range of the imaging unit, the amount of light can be calibrated by reducing the light using the neutral density filter unit so that it is within the dynamic range of the imaging unit.

[0068] In another aspect, in the above-mentioned shape measurement device, the calibration unit calibrates the amount of illumination light irradiated from the illumination unit by adjusting the illumination unit so that the amount of light received by the imaging unit becomes a predetermined light amount.

[0069] This makes it possible to provide a shape measuring device that calibrates the amount of illumination light emitted from the illumination unit so that the amount of light received by the imaging unit is a predetermined light amount that has been set in advance.

[0070] In another aspect, the above-mentioned shape measurement devices further include an alarm unit that issues an alarm to the outside when the current value of the current flowing through the illumination unit after the calibration exceeds a threshold value that is preset based on the maximum rated current value of the illumination unit.

[0071] The amount of illumination light emitted from the illumination unit generally decreases over time. Therefore, to compensate for the decreased amount of light, the current value flowing through the illumination unit is increased. Consequently, the current value flowing through the illumination unit eventually exceeds the maximum rated current value of the illumination unit, causing the illumination unit to fail. When the current value exceeds a threshold, the shape measurement device issues an alarm to the outside, allowing the illumination unit to take action, such as replacing the light-emitting element, before it fails.

[0072] In another aspect, in these above-mentioned shape measurement devices, the neutral density filter unit includes a neutral density filter and a movement drive unit that moves the neutral density filter between a calibration position and a retracted position, the calibration position being a position where the neutral density filter is placed between the illumination unit and the imaging unit, and the retracted position being a position where the neutral density filter is not placed between the illumination unit and the imaging unit.

[0073] Such a shape measurement device is equipped with a movement drive unit that moves the light-attenuating filter between the calibration position and the retracted position, so that the light-attenuating filter can be automatically moved between the calibration position and the retracted position for calibration and measurement.

[0074] Another aspect of the calibration method for a shape measurement device is a method for calibrating a shape measurement device that includes an illumination unit, an imaging unit, and an image processing unit that, during measurement, places a plate-shaped measurement object between the illumination unit and the imaging unit, and determines the contour shape of the measurement object based on a shadow image of the measurement object generated by imaging the shadow of the measurement object formed by illumination light irradiated from the illumination unit with the imaging unit, and that includes, during calibration, a placement step of placing a neutral density filter between the illumination unit and the imaging unit, and a calibration step of calibrating the amount of illumination light irradiated from the illumination unit based on the amount of light received by the imaging unit through the neutral density filter.

[0075] In the calibration method for such a shape measuring device, a neutral density filter that reduces the amount of incident light and then emits it is placed between the illumination unit and the imaging unit during calibration.Therefore, even when calibration is performed by adjusting the amount of illumination light emitted from the illumination unit to a set value that exceeds the dynamic range of the imaging unit, the amount of light can be calibrated by reducing the light using the neutral density filter so that it is within the dynamic range of the imaging unit.

[0076] In another aspect, in the method for calibrating a shape measuring instrument described above, the measurement object is a disk-shaped member, and the contour shape is a contour shape of the disk-shaped member in a thickness direction.

[0077] This provides a method for calibrating a shape measuring instrument that measures the contour shape of a disk-shaped member in the thickness direction.

[0078] In another aspect, in the method for calibrating a shape measuring instrument described above, the measurement object is a disk-shaped member, and the contour shape is a contour shape of the disk-shaped member in a circumferential direction.

[0079] This provides a method for calibrating a shape measuring instrument that measures the contour shape of a disk-shaped member in the circumferential direction.

[0080] In another aspect, in the above-mentioned method for calibrating a shape measuring device, the measurement object is a circular plate-shaped member having a notch formed at a predetermined position in the circumferential direction, and the contour shape is the contour shape of the notch.

[0081] This provides a method for calibrating a shape measuring device that measures the contour shape of a notch.

[0082] This application is based on Japanese Patent Application No. 2023-108156 filed on June 30, 2023, the contents of which are incorporated herein by reference.

[0083] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims.

[0084] According to the present invention, it is possible to provide a shape measuring device that measures the contour shape of a plate-shaped measurement target using illumination light, and a method for calibrating a shape measuring device.

Claims

1. A shape measuring device comprising an illumination unit, an imaging unit, and an image processing unit which, in the case of measurement, places a plate-shaped measurement object between the illumination unit and the imaging unit, and determines the contour shape of the measurement object based on a shadow image of the measurement object generated by imaging the shadow of the measurement object formed by illumination light irradiated from the illumination unit with the imaging unit; and, in the case of calibration, comprises a neutral density filter unit which is placed between the illumination unit and the imaging unit, and a calibration unit which calibrates the amount of illumination light irradiated from the illumination unit based on the amount of light received by the imaging unit via the neutral density filter unit.

2. The shape measuring device according to claim 1, wherein the calibration unit calibrates the amount of illumination light irradiated from the illumination unit by adjusting the illumination unit so that the amount of light received by the imaging unit becomes a predetermined light amount that has been set in advance.

3. The shape measuring device according to claim 1, further comprising an alarm unit that issues an alarm to the outside when the current value of the current flowing through the illumination unit after the calibration exceeds a threshold value that is preset based on the maximum rated current value of the illumination unit.

4. The shape measuring device of claim 1, wherein the neutral density filter section comprises a neutral density filter and a movement drive section which moves the neutral density filter between a calibration position and a retracted position, the calibration position being a position where the neutral density filter is disposed between the illumination section and the imaging section, and the retracted position being a position where the neutral density filter is not disposed between the illumination section and the imaging section.

5. A method for calibrating a shape measuring device comprising an illumination unit, an imaging unit, and an image processing unit which, in the case of measurement, places a plate-shaped measurement object between the illumination unit and the imaging unit, and determines a contour shape of the measurement object based on a shadow image of the measurement object generated by imaging the shadow of the measurement object formed by illumination light irradiated from the illumination unit with the imaging unit, the method comprising: in the case of calibration, a placement step of placing a neutral density filter between the illumination unit and the imaging unit; and a calibration step of calibrating the amount of illumination light irradiated from the illumination unit based on the amount of light received by the imaging unit through the neutral density filter.

6. The method for calibrating a shape measuring device according to claim 5, wherein the measurement object is a disk-shaped member, and the contour shape is the contour shape in a thickness direction of the disk-shaped member.

7. The method for calibrating a shape measuring instrument according to claim 5, wherein the measurement object is a disk-shaped member, and the contour shape is a contour shape in a circumferential direction of the disk-shaped member.

8. A method for calibrating a shape measuring device according to claim 5, wherein the measurement object is a disk-shaped member having a notch formed at a predetermined position in the circumferential direction, and the contour shape is the contour shape of the notch.

Images