Image measuring device

Abstract

Image measuring device (1) which includes: a table (12) for arranging a workpiece; a camera (110, 120) which photographs the workpiece on the table (12) and produces a workpiece image; a transmission lighting unit (150) arranged in a housing (100) for irradiating the workpiece on the table (12) with illumination light from below the table (12); a ring illumination unit (140) with a diffuse illumination device (50) and a side-emitting illumination device (40) is integrated, wherein the diffuse illumination device (50) is ring-shaped, surrounds the photo axis of the camera (110, 120) and has a ring-shaped optical diffuser (53), and the side-emitting illumination device (40) illuminates the workpiece on the table (12) with illumination light from the side of the workpiece through a slot (46) which is provided in the direction of the photo axis below the diffuse illumination device (50); a relative position setting unit (101, 103) which moves the ring illumination unit (140) along the direction of the photo axis to set a relative position between the ring illumination unit (140) and the table (12); an execution switch (16) which is arranged on the housing (100); an imaging control unit (21) that is suitable for moving the relative position setting unit (101, 103) to a relative position corresponding to a measurement target location, based on measurement setting data, in response to an actuation of the execution switch (16), and for obtaining the workpiece image; and a dimensional measuring unit (26) suitable for extracting an edge of the measurement target location based on the obtained workpiece image and for obtaining a dimension of the measurement target location based on the extracted edge.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates to an image measuring device and in particular to an improvement in an image measuring device which extracts an edge in a workpiece image obtained by photographing a workpiece in order to measure a dimension of the workpiece. 2. Description of the state of the art

[0002] An image measuring device is a device that photographs a workpiece to obtain an image of the workpiece and extracts or detects an edge in the workpiece image to measure a dimension and shape of the workpiece (for example, JP 2012-32224 A, JP 2012-32341 A, JP 2012-32344 A, JP 2012-159409 A, and JP 2012-159410 A). The workpiece is typically positioned on a movable table that can be moved along the X, Y, and Z axes. Moving the table along the Z axis brings the workpiece image into focus, and moving the table along the X or Y axis adjusts the workpiece's position within a field of view. Other image measuring devices with various illumination devices are known from US 4 606 635 A, DE 36 86 847 T2, DE 101 28 476 A1, WO 2004 / 040 279 A1, DE 11 2006 002 867 T5 and DE 10 2007 043 609 A1.

[0003] Since the workpiece image is a very accurate replica of the workpiece, regardless of the position of the moving table along the Z-axis, determining distances and angles within the image allows for the detection of the workpiece's actual dimensions. Edge extraction is performed by analyzing changes in the illumination of the workpiece image, detecting edge points, and fitting a geometric figure, such as a straight line, circle, or arc, to the detected edge points. This yields an edge, which marks a boundary between the workpiece and a background, and a roughness on the workpiece. The workpiece's dimensions are obtained as the distance or angle between the edges thus obtained, or as the central position or diameter of a circular edge.Furthermore, a difference (an error) between the value of the measured dimension and a design value is compared as a tolerance in order to perform a quality determination.

[0004] When measuring the external shape of a workpiece using such an image measuring device, transmission illumination is often used to illuminate the workpiece on the table from the side opposite the camera. Conversely, when measuring a non-through opening, a step, or the roughness of the workpiece, epi-illumination is often used to illuminate the workpiece on the table from the same side as the camera.

[0005] With conventional image-based measuring equipment, a texture on the workpiece surface—that is, a machining mark, a pattern, or a fine roughness—can sometimes be erroneously extracted as an edge when determining dimensions using epi-illumination. This makes it difficult to stabilize the dimensional measurement compared to using transmission illumination, which was problematic. This is especially true when photographing the workpiece on the table using a camera with low photographic magnification, as an edge cannot be reliably extracted. Typically, in dimensional measurement, a vertical plane parallel to the camera's optical axis is extracted as an edge.However, since the camera has a high depth of field even at low magnification, even if the upper end of the vertical plane was initially in focus, the lower end of the vertical plane would also be in focus. Consequently, accurate edge extraction was difficult, as it was affected not only by a texture at the upper end of the vertical plane but also by a texture at the lower end. SUMMARY OF THE INVENTION

[0006] The present invention was developed in light of the above circumstances, and one object thereof is to provide an image measurement device with which stable edge extraction can be performed. In particular, one object thereof is to provide an image measurement device with which the erroneous extraction of a texture on a workpiece surface as an edge can be reduced during dimensional measurement using epi-illumination. Furthermore, one object thereof is to provide an image measurement device with which a step can be correctly extracted as an edge when measuring a workpiece which has the step in one direction of the camera's photo axis.

[0007] An image measuring device according to an embodiment of the invention has the features of claim 1 and in particular: a table for arranging a workpiece; a camera which photographs the workpiece on the table and generates a workpiece image; a laterally emitting illumination device which has a light quantity distribution which changes sharply or rapidly in one direction of the camera's photo axis and illuminates the workpiece on the table laterally or from one side with illumination light; a measurement target location specification unit which specifies a measurement target location on the workpiece image; a relative position adjustment unit which moves the table or the laterally emitting illumination device in the direction of the photo axis in order to set a relative position between the laterally emitting illumination device and the table;a relative position determination unit which detects a change in illumination at the target measurement location with respect to two or more workpiece images photographed while the relative position is changing in order to determine a relative position; an imaging control unit which controls the relative position setting unit based on the determined relative position and actuates the laterally emitting illumination device to obtain the workpiece image; and a dimensional measurement unit which extracts an edge of the target measurement location based on the obtained workpiece image in order to obtain a dimension of the target measurement location based on the extracted edge.

[0008] This image measurement device allows the illumination position to be located along the photographic axis in relation to the workpiece's illumination light. This is because the laterally emitting illumination device has a light distribution that changes sharply and rapidly along the camera's photographic axis. For example, when measuring a workpiece with a step along the photographic axis, the workpiece can be illuminated by shining the light on either the upper or lower end of the step. Localizing the illumination position in this way avoids the influence of textures located away from the target measurement point along the photographic axis. Therefore, when using epi-illumination for dimensional measurement, it is possible to reduce the erroneous extraction of textures on the workpiece surface as edges.

[0009] Furthermore, since the influence of a texture at a position remote from the measurement target along the photo axis is avoided, it is possible to correctly extract a desired edge, even when photographing the workpiece using a camera with low magnification. For example, when measuring a workpiece with a step along the photo axis, the step can be correctly extracted as an edge if the workpiece is photographed with the illumination only on the upper or lower end of the step.

[0010] Furthermore, a change in the illumination of the measurement target location is obtained with respect to two or more workpiece images, which are photographed while changing the relative position, and the relative position is subsequently determined, making it possible to automatically determine a suitable irradiation position with the illumination light to extract an edge of the measurement target location and to photograph the workpiece.

[0011] In addition to the above setup, an image measuring device according to a further embodiment of the invention can be constructed such that the laterally emitting illumination device provides illumination with illumination light as parallel light or with illumination light that has a spreading angle that is close to parallel light, wherein the illumination light has a change range to a peripheral part or circumferential area of ​​the light quantity distribution that is less than a depth of field of the camera.

[0012] With such a setup, by adjusting the relative position of the laterally emitting illumination device so that a boundary of the illumination light is located within the depth of field of the camera, it is possible to correctly extract an edge within the depth of field without being affected by a texture that is located far from the measurement target location.

[0013] In addition to the above setup, an image measuring device according to a further embodiment of the invention can be configured such that the laterally emitting illumination device illuminates an area narrower than the depth of field. With such a setup, it is possible to illuminate a pinpoint within the camera's depth of field relative to the direction of the photographic axis, thus enabling the accurate extraction of an edge within the depth of field.

[0014] In addition to the above setup, an image measuring device according to yet another embodiment of the invention can be constructed such that the laterally emitting illumination device has a mirror that reflects illumination light emitted by a light source in the direction of the photo axis in a direction that intersects the direction of the photo axis, and a slot that limits a diverging angle of the illumination light reflected by the mirror.

[0015] Since the illumination light emitted by the light source is deflected by the mirror, such a setup makes it possible to reduce the dimensions of the laterally emitting illumination device in a direction that intersects the direction of the photographic axis. Furthermore, by limiting the diffraction angle of the illumination light with the slit, it is possible to achieve illumination with light that more closely approximates parallel light.

[0016] In addition to the above setup, an image measuring device according to yet another embodiment of the invention can be configured such that the slot of the laterally emitting illumination device is a slit that is narrower than the depth of field of the camera. With such a setup, it is possible to obtain illumination light that is narrower than the depth of field of the camera.

[0017] In addition to the above setup, an image measuring device according to yet another embodiment of the invention has a diffuse illumination device which has an annular light source surrounding the photo axis of the camera and illuminates the workpiece on the table with diffuse light from above, wherein the laterally emitting illumination device has a light source which is arranged concentrically with respect to the light source of the diffuse illumination device, and wherein this is provided with the slot in a stepped part which is formed by a lens tube part projecting more strongly in the direction of the photo axis than the lower end of the diffuse illumination device.

[0018] Since the light source of the side-emitting illumination device is arranged concentrically with respect to the light source of the diffuse illumination device, this setup makes it possible to illuminate the periphery or surroundings of the workpiece from the side. Furthermore, because the slot in the stepped section is formed by the lens tube section protruding more in the direction of the photo axis than the lower end of the diffuse illumination device, it is possible to arrange the diffuse illumination device and the side-emitting illumination device without increasing the size of the side-emitting illumination device in the direction that intersects the photo axis.

[0019] In addition to the above setup, an image measurement device according to a further embodiment of the invention can be configured such that the measurement target location specification unit specifies an area on the workpiece image, which is photographed under diffuse light illumination by the diffuse illumination device, as the measurement target location. Using the workpiece image photographed under diffuse light illumination, it is possible with such a setup to specify the measurement target location while the entire image of the workpiece is being inspected.

[0020] In addition to the above setup, an image measurement device according to a further embodiment of the present invention can include a measurement target information storage unit which stores or holds two or more measurement target locations in relation to relative positions. The imaging control unit repeatedly moves the table or the side-emitting illumination device to the corresponding relative position for each measurement target location stored in the measurement target information storage unit and illuminates the workpiece on the table from one side with the illumination light of the side-emitting illumination device to obtain the workpiece image. If several measurement target locations are specified on the same workpiece image, it is possible with such a setup to sequentially extract edges of these measurement target locations while the relative position between the side-emitting illumination device and the table is adjusted.

[0021] In addition to the above setup, an image measurement device according to a further embodiment of the invention can be configured such that the relative position determination unit obtains a contrast in the vicinity of an edge of the measurement target location with respect to each of a plurality of workpiece images illuminated by the illumination light from the laterally emitting illumination device, in order to determine a relative position associated with the measurement target location based on the obtained contrasts. According to such a setup, it is possible to improve the stability of the edge extraction by determining a relative position associated with the measurement target location based on a relative position at which a workpiece image with high contrast was photographed from among the multiple workpiece images that were photographed while changing the relative position.

[0022] In addition to the above setup, an image measurement device according to a further embodiment of the invention can be configured such that the imaging control unit controls the relative position adjustment unit so that the position of the illumination with the light corresponds to a focus position of the camera in order to obtain the workpiece image. With such a setup, it is possible to correctly extract an edge in a focused image area.

[0023] According to the present invention, it is possible to provide an image measurement device with which stable edge extraction can be performed. Since the influence of a texture located in a direction away from a measurement target location along the photo axis is avoided, it is particularly possible to provide an image measurement device with which, during dimensional measurement using epi-illumination, the erroneous extraction of a texture on the workpiece surface as an edge can be reduced. Furthermore, it is possible to provide an image measurement device with which a step can be correctly extracted as an edge when measuring a workpiece that has a step in a direction along the photo axis of a camera. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view showing an exemplary setup of an image measuring device 1 according to an embodiment of the present invention; Fig. Figure 2 is an explanatory view showing an exemplary structure of a measuring unit 10. Fig. Figure 1 schematically shows and shows a cutting plane in the case of the section of the measuring unit 10 by means of a vertical plane parallel to a photo axis; Fig. Figure 3 is a sectional view showing an exemplary structure of a ring lighting unit 140. Fig. 2 shows; Fig. Figure 4 is a diagram showing an example of the light quantity distribution of a side-emitting lighting device 40 of the Fig. 3 shows; Fig. Figure 5 is a view that provides an example of the operation of measuring unit 10. Fig. Figure 2 shows a case in which an upper end part of the workpiece W is illuminated on a movable table 12 with illumination light 2 of the laterally emitting lighting; Fig. Figure 6 is a view that provides an example of the operation of measuring unit 10. Fig. Figure 2 shows a workpiece image that is in the state of Fig. 5 is photographed; Fig. Figure 7 is a view that provides an example of the operation of measuring unit 10. Fig. 2 shows and shows a case in which an intermediate part of the workpiece W on the movable table 12 is illuminated with the illumination light 2 of the laterally emitting lighting; Fig. Figure 8 is a view which is an example of the operation of measuring unit 10 of the Fig. Figure 2 shows a workpiece image that is in the state of Fig. 7 is photographed; Fig. Figure 9 is a block diagram that shows an example of the functional structure of a control unit 20. Fig. 1 shows; Fig. Figure 10 is a flowchart that provides an example of how image measuring device 1 works. Fig. 1 at the time of measurement setup; Fig. Figure 11 is a flowchart that provides an example of how image measuring device 1 works. Fig. 1 at the time of measurement setup; Fig. Figure 12 is a flowchart that provides an example of how image measuring device 1 works. Fig. 1 at the time of a dimension measurement; Fig. Figure 13 is a sectional view showing another exemplary assembly of the laterally emitting lighting device 40; and Fig. 14A and Fig. Figure 14B shows sectional views, each showing a further exemplary assembly of the laterally emitting lighting device 40. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS<Bildmesseinrichtung 1>

[0024] Fig. Figure 1 is a perspective view showing an exemplary setup of an image measuring device 1 according to an embodiment of the present invention. This image measuring device 1 is a dimensional measuring device that extracts an edge from a workpiece image obtained by photographing the workpiece in order to measure a dimension of the workpiece. The image measuring device 1 consists of a measuring unit 10, a control unit 20, a keyboard 31, and a mouse 32. The workpiece is a measurement target whose shape and dimension are to be measured.

[0025] The measuring unit 10 comprises a display unit 11, a movable table 12, an XY adjustment knob 14a, a Z adjustment knob 14b, a power switch 15, and an execution switch 16. The measuring unit 10 illuminates the workpiece on the movable table 12 with measuring light, which is visible light, and receives the transmitted or reflected light to generate an image of the workpiece. The workpiece is positioned within a detection area 13 of the movable table 12. Furthermore, the measuring unit 10 displays the workpiece image on a display 11a of the display unit 11.

[0026] The display unit 11 is a display unit that shows a workpiece image or a measurement result on the display 11a. The movable table 12 is an arrangement table for positioning the workpiece and is equipped with the detection area 13, to which detection light is transmitted. The detection area 13 is a circular area made of transparent glass. This movable table 12 can be moved in the direction of the Z-axis, which is parallel to a camera's photo axis, and in directions of the X-axis and Y-axis, which are perpendicular to the photo axis.

[0027] The XY adjustment knob 14a is a control element for moving the movable table 12 in the direction of the X-axis or the direction of the Y-axis in order to set its position in the X-axis and Y-axis directions. The Z adjustment knob 14b is a control element for moving the movable table 12 in the direction of the Z-axis in order to set its position in the Z-axis direction. The power switch 15 is a control element for switching a main power supply or main power of both the measuring unit 10 and the control unit 20 between an on state and an off state. The execution switch 16 is a control element for starting the dimensional measurement.

[0028] The control unit 20 is a control element that manages the photography and display by the measuring unit 10 and analyzes a workpiece image to measure a dimension of the workpiece. The control unit 20 is connected to the keyboard 31 and the mouse 32. After the power supply is switched on, the dimension of the workpiece is measured automatically when the workpiece is positioned within the detection area 13 and the execution switch 16 is activated. <Messeinheit 10>

[0029] Fig. Figure 2 is an explanatory view showing an exemplary setup of the measuring unit 10. Fig. Figure 1 schematically shows a section plane in the case of cutting the measuring unit 10 by means of a vertical plane parallel to the photo axis. This measuring unit 10 is composed of the display device 11, the movable table 12, a housing 100, a table adjustment part 101, a lens tube part 102, an illumination position adjustment part 103, cameras 110, 120, a coaxial epi illumination unit 130, a ring illumination unit 140 and a transmission illumination unit 150.

[0030] The table adjustment unit 101, the lens tube unit 102, the cameras 110, 120, the coaxial epi illumination unit 130 and the transmission illumination unit 150 are arranged in the housing 100. The table adjustment unit 101 moves the movable table 12 in the directions of the X, Y or Z axis, based on an actuation signal from the control unit 20, and sets the position of the workpiece in the directions of the X, Y and Z axes.

[0031] The camera 110 is an imaging device with low photographic magnification and consists of an imaging element 111, an image-forming lens 112, an aperture 113, and a light-receiving lens 114. The imaging element 111 receives detection light and generates an image of the workpiece. This imaging element 111 is arranged so that its light-receiving surface faces downwards. The image-forming lens 112 is an optical element that forms an image onto the imaging element 111 using the detection light. The aperture 113 is an optical diaphragm that limits the amount of transmitted detection light and is located between the image-forming lens 112 and the light-receiving lens 114. The light receiving lens 114 is an optical element that collects the detection light from the workpiece and is arranged opposite the movable table 12.The image formation lens 112, the aperture 113 and the light receiving lens 114 are arranged with a vertically extending central axis as their center.

[0032] The camera 120 is a high-magnification imaging device comprising an imaging element 121, an image-forming lens 122, an aperture 123, a beam splitter 124, and a light-receiving lens 114. The imaging element 121 receives detection light and generates an image of the workpiece. This imaging element 121 is arranged such that its light-receiving surface faces a horizontal direction. The image-forming lens 122 is an optical element that forms an image using the detection light and the imaging element 121. The aperture 123 is an optical diaphragm that limits the amount of transmitted detection light and is located between the image-forming lens 122 and the beam splitter 124. The light-receiving lens 114 is shared with the camera 110.The detection light transmitted through the light receiving lens 114 is deflected in the horizontal direction by the beam splitter 124, and an image is formed on the imaging element 121 by means of the aperture 123 and the image formation lens 122.

[0033] The imaging elements 111 and 121 consist of an image sensor, such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). A telecentric lens is used as the light-receiving lens, which has the property that the size of an image does not change even if its position in the vertical direction, i.e., the direction of the photo axis, changes.

[0034] The coaxial epi-illumination unit 130 is an epi-illumination device that illuminates the workpiece on the movable table 12 from above with illumination light and aligns an optical axis of the illumination light with the photo axis. This coaxial epi-illumination unit 130 consists of a light source 131, which is arranged so that it faces the horizontal direction, and a beam splitter 132, which deflects the illumination light emitted by the light source 131 downwards.

[0035] The image formation lenses 112, 122, the apertures 113, 123, the beam splitters 124, 132 and the light receiving lens 114 are arranged in the lens tube part 102.

[0036] The transmission lighting unit 150 is a transmission lighting device that illuminates the workpiece on the movable table 12 from below with illuminating light. It consists of a light source 151, a mirror 152, and a condenser 153. The light source 151 is arranged so that it faces the horizontal direction. Illuminating light emitted by the light source 151 is reflected by the mirror 152 and emitted via the condenser 153. This illuminating light is transmitted through the movable table 12, and part of the transmitted light is blocked by the workpiece, while another part falls onto the light-receiving lens 114.

[0037] The ring illumination unit 140 is an epi-illumination device that illuminates the workpiece on the movable table 12 from above or from the side. It is ring-shaped, surrounding the photo axis of the cameras 110 and 120. The light sources for the illumination units 130 to 150 can be, for example, an LED (light-emitting diode) or a halogen lamp. The illumination position adjustment unit 103 is a relative position adjustment unit that moves the ring illumination unit 140 in the direction of the photo axis to establish a relative position between a laterally emitting illumination device 40 and the movable table 12. Transmission illumination, ring illumination, and / or coaxial epi-illumination can be selected as the workpiece illumination method. <Ringbeleuchtungseinheit 140>

[0038] Fig. Figure 3 is a sectional view showing an exemplary assembly of the ring lighting unit 140. Fig. Figure 2 shows. This ring illumination unit 140 is a lighting device formed by coaxially arranging a laterally emitting lighting device 40, which provides side illumination with illumination light 2 having a spreading angle close to parallel light, and a diffuse lighting device 50, which provides irradiation with diffuse light.

[0039] The laterally emitting illumination device 40 is an epi-illumination device consisting of a wiring substrate 41, a light source 42, a lens tube section 43, a mirror 44, a diffusion plate 45, and a slot 46, and exhibits a light quantity distribution that changes sharply in the direction of the photo axis. The lens tube section 43 has a cylindrical interior extending in the direction of the photo axis, which accommodates the wiring substrate 41, the light source 42, the mirror 44, and the diffusion plate 45.

[0040] The wiring substrate 41 and the light source 42 are arranged on a cover portion of the lens tube part 43, and the mirror 44, the diffusion plate 45, and the slot 46 are arranged on the bottom of the lens tube part 43. The light source 42 is arranged on the wiring substrate 41 in a downward-facing position. For example, an LED (light-emitting diode) is used as the light source 42. The light source 42 is an annular light source with two or more LEDs arranged around its circumference.

[0041] The mirror 44 is an optical element that reflects the illumination 2, emitted by the light source 42 in the direction of the photoaxis, in a direction that intersects the direction of the photoaxis. This mirror 44 is formed from an annular reflective plate and is arranged at an angle of approximately 45 degrees. Since the illumination 2 emitted by the light source 42 is deflected by the mirror 44, it is possible to reduce the size or dimension of the laterally emitting illumination device 40 in the direction that intersects the direction of the photoaxis, while ensuring an optical path from the light source 42 to the slot 46.

[0042] The slot 46 is a spreading-angle limiting element that limits the spreading angle of the illumination light 2 reflected by the mirror 44. The slot 46 is a slit in the direction of the photographic axis and is shaped in a circumferential direction. The slot 46 is positioned at a certain distance from the light source 42. By limiting the spreading angle of the illumination light 2 with the slot 46, it is possible to illuminate the subject with light 2 that is closer to parallel. For example, the slot 46 is shaped as a slit narrower than the depth of field of the camera 110 for low-magnification photography.

[0043] The diffusion plate 45 is a diffusion plate with a large aspect ratio, which diffuses the illumination 2 in the circumferential direction and is arranged between the mirror 44 and the slot 46. This diffusion plate 45 is cylindrical and extends along the photographic axis. By arranging such a diffusion plate 45, it is possible to avoid uneven light distribution in the circumferential direction, even if the light source 42 comprises a large number of individually arranged LEDs.

[0044] The optical axis of the illumination light 2, which is emitted from a light projection window of the laterally emitting illumination device 40, is inclined with respect to the horizontal direction within the range of 0° or more and 45° or less. For example, the optical axis of the illumination light 2 is inclined with respect to the horizontal direction within the range of 30°.

[0045] The diffuse illumination device 50 is an epi-illumination device consisting of a wiring substrate 51, a light source 52, and a diffusion plate 53. The light source 52 is an annular light source surrounding the photoaxes of the cameras 110 and 120. The light source 52 is positioned on the wiring substrate 51 in a downward-facing position. The diffusion plate 53 is an optical element that diffuses the illumination light emitted by the light source 52 in a circumferential or radial direction. This diffusion plate 53 is annular in shape, and its cross-sectional shape with respect to a vertical plane parallel to the photoaxis is an arcuate curve. The workpiece on the movable table 12 is illuminated with the diffuse light from above or from the side.

[0046] The lens tube section 43 of the laterally emitting illumination device 40 extends radially outside the diffuse illumination device 50, and the light source 42 is arranged concentrically with respect to the light source 52 of the diffuse illumination device 50. Furthermore, the slot 46 is formed in a stepped section 3, which is created by the lens tube section 43 projecting more prominently in the direction of the photographic axis than the lower end of the diffuse illumination device 50. Since the light source 42 of the laterally emitting illumination device 40 is arranged concentrically with respect to the light source 52 of the diffuse illumination device 50, the periphery or surroundings of the workpiece can be illuminated from the side.Furthermore, since the slot 46 is formed in the step part 3, the diffuse lighting device 50 and the side-emitting lighting device 40 can be arranged without increasing the dimension of the side-emitting lighting device 40 in the direction which intersects the direction of the photo axis.

[0047] Fig. Figure 4 is a diagram showing an example of the light quantity distribution of the side-emitting lighting device 40. Fig. 3 shows. In Fig. Figure 4 shows the light quantity distribution of the illumination light 2 in the vicinity of the detection area 13 of the movable table 12, where a horizontal axis denotes a quantity of light and a vertical axis denotes a position in the direction of the Z-axis. Fig. Figure 4 shows a case in which the illumination light 2 has an approximately linear symmetrical light quantity distribution, with a position Z0 in the direction of the Z-axis being taken as the center.

[0048] The light intensity distribution of the illumination light 2 corresponds to an illumination intensity distribution on the workpiece when the workpiece is illuminated by the illumination light 2 on the movable table 12. The light intensity has a maximum value of Km at position Z0 in the direction of the Z-axis and decreases rapidly and sharply with increasing distance from position Z0. For extracting a fine roughness as an edge by creating a clear boundary between an illuminated and an unilluminated area with the illumination light 2, it is preferable for the change ranges ΔZa and ΔZb to be narrower along a circumference of the light intensity distribution.

[0049] For example, each of the change ranges ΔZa and ΔZb is a range in which the amount of light changes from approximately 90% to approximately 10% of the maximum value Km, and this is narrower than the depth of field of camera 110 for low-magnification photography. With such a setup, it is possible to correctly extract an edge within the depth of field without being affected by a texture located away from the measurement target location by adjusting the relative position of the ring illumination unit 140 such that a boundary of the illumination light 2 is localized within the depth of field of camera 110.

[0050] Furthermore, the width ΔZc of the illumination light 2 in the direction of the Z-axis is sufficiently narrower than the depth of field of the camera 110, and an area narrower than the depth of field of the camera 110 is illuminated by the illumination light 2. With such a setup, it is possible to perform illumination within the depth of field of the camera 110 at a precise point (pinpoint) with respect to the direction of the photographic axis in order to extract an edge within the depth of field.

[0051] Fig. Figure 5 is a view which provides an example of how the measuring unit 10 functions. Fig. Figure 2 shows a case in which an upper end part of the workpiece W on the movable table 12 is illuminated by the illumination light 2 of the laterally emitting light. Furthermore, Fig. 6 a view which is an example of the functioning of the measuring unit 10 of the Fig. Figure 2 shows, and this shows a workpiece image that is in the state of Fig. 5 is photographed.

[0052] Since the laterally emitting illumination device 40 has a light distribution that changes sharply in the direction of the photo axis, the irradiation position of the workpiece W on the movable table 12 with the illumination light 2 in the direction of the photo axis can be located. For this reason, in the case of measuring a workpiece W that has a step in the direction of the photo axis, the workpiece W can be photographed with the illumination light 2 illuminating only the upper end part of the step.

[0053] In this case, only the upper end of the workpiece W is illuminated by the light source 2, and the illumination in the workpiece image changes significantly in the vicinity of the edge of the upper end. Localizing the position of the illumination with the light source 2 in this way avoids the influence of a texture at a position located away from the target measurement point along the photo axis.

[0054] Fig. Figure 7 is a view that provides an example of how the measuring unit 10 functions. Fig. Figure 2 shows a case in which an intermediate part of the workpiece W on the movable table 12 is illuminated by the illumination light 2 of the laterally emitting light. Furthermore, Fig. 8 a view that provides an example of how the measuring unit 10 works Fig. Figure 2 shows, and this shows a workpiece image that is in the state of Fig. 7 is photographed.

[0055] In this example, only the intermediate part of the workpiece W is illuminated by the light source 2, and the illumination in the workpiece image changes significantly in the vicinity of the edge of the intermediate part. Localizing the position of the illumination by the light source 2 in this way can avoid the influence of a texture at a position located away from the target measurement point along the photo axis. <Steuereinheit 20>

[0056] Fig. Figure 9 is a block diagram that shows an example of a functional structure in control unit 20 of the Fig. Figure 1 shows. This control unit 20 is composed of an imaging control part 21, a workpiece image storage part 22, a measurement target location specification part 23, a measurement location information storage part 24, a relative position determination part 25 and a dimension measuring part 26.

[0057] The imaging control unit 21 controls the cameras 110, 120, the lighting position adjustment unit 103 and the lighting units 130 to 150 based on the control by the user to obtain a workpiece image from the cameras 110, 120, and stores the workpiece image in the workpiece image storage unit 22.

[0058] The measurement target location specification part 23 specifies a measurement target location on the workpiece image. For example, based on the user setting, the measurement target location specification part 23 specifies as the measurement target location an area on the workpiece image that is photographed under irradiation with the diffuse light of the diffuse illumination device 50. By using the workpiece image photographed under irradiation with the diffuse light, it is possible to specify the measurement target location while the entire image of the workpiece is being inspected. Position information that identifies the measurement target location and a measurement type is stored as measurement location information in the measurement location information memory part 24.

[0059] The relative position determination unit 25 receives a change in the illumination at the measurement target location relative to two or more workpiece images that are photographed, while the relative position between the side-emitting illumination device 40 and the movable table 12 is changed in order to determine the relative position. The two or more workpiece images mentioned above are workpiece images obtained by photographing the same workpiece using illumination from the side-emitting illumination device 40.For example, the relative position determination part 25 receives a contrast of an image at the measurement target location with respect to each of a plurality of workpiece images that are photographed under illumination with the lighting light 2 by the laterally emitting lighting device 40, and compares the obtained contrasts in order to determine a relative position at which the workpiece image with the greatest contrast was photographed as a relative position that is to be associated with the measurement target location.

[0060] Generally speaking, if the image contrast is greater, the edge extraction is more stable. Such contrast of the measurement target location is obtained as an evaluation value that characterizes the stability of the edge extraction. A workpiece image with the highest evaluation value, i.e., a workpiece image with the greatest contrast, is extracted from several workpiece images that are photographed while the relative position of the laterally emitting illumination device 40 is changed, and the relative position is subsequently determined, thereby enabling an improvement in the stability of the edge extraction.

[0061] Furthermore, there is a method for determining the relative position associated with the measurement target location that differs from the method described above. In this method, a workpiece image with the highest contrast at the measurement target location is determined from several workpiece images, and the relative position at which the workpiece image was obtained is determined as the relative position described above. For example, the setup can be designed such that, based on three or more workpiece images with different relative positions between the laterally emitting illumination device 40 and the movable table 12, a distribution containing the contrast at each relative position is obtained, and a curve, such as a quadratic curve, is applied to this distribution to determine a relative position at which the contrast is greatest.

[0062] The measurement location information storage unit 24 holds or stores two or more measurement target locations together with their relative positions. The measurement target location and the relative position are stored as measurement location information. The imaging control unit 21 controls the illumination position adjustment unit 103 based on the relative position determined by the relative position determination unit 25 and actuates the laterally emitting illumination device 40 to obtain a workpiece image. Based on the workpiece image obtained by the imaging control unit 21, the dimension measuring unit 26 extracts an edge of the measurement target location, obtains a dimension of the measurement target location based on the extracted edge, and outputs the measurement result.

[0063] Since the relative position is determined based on two or more workpiece images that are photographed while the relative position between the laterally emitting illumination device 40 and the movable table 12 is changed, it is possible to photograph the workpiece by automatically determining a suitable position of irradiation with the illumination light 2 for extracting an edge of the measurement target location.

[0064] With respect to each measurement target location stored in the measurement location information memory unit 24, the imaging control unit 21 moves the side-emitting illumination device 40 to the corresponding relative position and illuminates the workpiece on the movable table 12 with illumination light 2 from the side-emitting illumination device 40 from the side, in a repeating manner, to obtain the workpiece image. With such a setup, edges of these measurement target locations can be extracted sequentially while the relative position between the side-emitting illumination device 40 and the movable table 12 is adjusted when several measurement target locations with respect to the same workpiece image are specified.

[0065] Furthermore, the imaging control unit 21 controls the illumination position adjustment unit 103, so that the position of the illumination with the light source 2 coincides with a focus position of the camera 110 in order to obtain the workpiece image. With such a setup, an edge in a focused image area can be correctly extracted.

[0066] A measurement result, such as a dimensional value, is displayed on the display unit 11. Furthermore, the control unit 20 generates measurement setting data for the sequential or repeated measurement of the workpiece. This measurement setting data contains positioning information, measurement location information, information identifying a design value, and a tolerance for each measurement target location. The position information is used to analyze a workpiece image to detect the position and orientation of the workpiece.

[0067] The Fig. 10 and Fig. 11 with steps S101 to S115 are flowcharts which provide an example of the functional sequence at the time of the measurement setting of the image measuring device 1 of the Fig. 1. First, the control unit 20 activates the diffuse lighting device 50 of the ring lighting unit 140, photographs the workpiece on the movable table 12 using the camera 110 (steps S101, S102) and displays a workpiece image obtained from the camera 110 on the display device 11.

[0068] Next, the control unit 20 accepts the user inputs, and if a measurement target location is specified on the workpiece image (step S103), the control unit 20 activates the side-emitting illumination device 40 instead of the diffuse illumination device 50 and photographs the workpiece on the movable table 12 using the camera 110 (steps S104, S105). Based on the workpiece image, which is photographed from the side under illumination with the light source 2, the control unit 20 receives a change in the illumination at the measurement target location and calculates a contrast in the vicinity of the edge as an evaluation value that characterizes the stability of the edge extraction (step S106).

[0069] The control unit 20 controls the lighting position adjustment unit 103 to repeat the processing procedure of steps S105 and S106, while the ring lighting unit 140 is moved sequentially to two or more preset positions in the direction of the Z-axis (step S107). Subsequently, the control unit 20 compares the relative positions between the laterally emitting lighting device 40 and the movable table 12, that is, evaluation values ​​of a plurality of workpiece images with different lighting positions, and calculates a relative position according to the measurement target location (step S108).

[0070] Next, to adjust the lighting position, the control unit 20 controls the lighting position adjustment part 103 to move the ring lighting unit 140 to the relative position obtained from the evaluation step (step S109). Subsequently, the control unit 20 photographs the workpiece on the movable table 12 to obtain a workpiece image (step S110).

[0071] The control unit 20 extracts an edge of the measurement target location based on the obtained workpiece image (step S111) and calculates a dimension value or value of the dimension of the measurement target location based on the extracted edge (step S112) in order to display the edge and the dimension value as measurement results on the display device 11 (step S113).

[0072] The control unit 20 accepts the user's input, and if a different measurement target location is specified, the control unit 20 repeats the processing procedure of step S103 and the subsequent steps (step S114). When the dimensional measurement is complete with respect to all measurement target locations, the control unit 20 generates measurement setting data and completes this processing (step S115).

[0073] The Fig. 12 with steps S201 to S211 is a flowchart that shows an example of the functional sequence at the time of dimensional measurement in the image measuring device 1 of the Fig. Figure 1 shows. First, the control unit 20 accepts the user's input and selects measurement setting data as a subsequent measurement target according to the workpiece (step S201).

[0074] Next, when the execution switch 16 of the measuring unit 10 is actuated (step S202), the control unit 20 reads the measurement target location, which is stored as measurement setting data (step S203), and controls the illumination position adjustment unit 103 to adjust the illumination position in order to move the ring illumination unit 140 to the relative position associated with the measurement target position (step S204). Subsequently, the control unit 20 activates the side-emitting illumination device 40 and photographs the workpiece on the movable table 12 to obtain a workpiece image (step S205).

[0075] The control unit 20 extracts an edge of the measurement target location based on the obtained workpiece image (step S206) and calculates a dimensional value of the measurement target location based on the extracted edge (step S207). If another measurement target location is present, the control unit 20 repeats the processing procedure from step S203 to step S207 (step S208). When the dimensional measurement for all measurement target locations is complete, the control unit 20 displays the edge and the dimensional value as measurement results on the display device 11 (step S209) and saves the measurement results (step S210).

[0076] If another workpiece is available as a subsequent measurement target, the control unit 20 repeats the processing procedure of step S202 and subsequent steps, and if no further workpiece is available as a subsequent measurement target, the control unit 20 completes this processing (step S211).

[0077] Since the laterally emitting illumination device 40 has a light distribution that changes sharply in the directions of the photo axes of the cameras 110 and 120, the irradiation position of the workpiece on the movable table 12 can be localized in the direction of the photo axis according to the present embodiment. Because such localization of the irradiation position avoids the influence of a texture at a position located away from the measurement target in the direction of the photo axis, it is possible to avoid the erroneous extraction of a texture on the workpiece surface as an edge during dimensional measurement using epi-illumination.

[0078] Furthermore, since the influence of the texture at a position far from the measurement target location in the direction of the photo axis is avoided, it is possible to correctly extract a desired edge, even when photographing a workpiece using camera 110 with low magnification. Additionally, with respect to two or more workpiece images to be photographed, a change in the illumination of the measurement target location is obtained while the relative position is changed, and the relative position is then determined. This makes it possible to photograph the workpiece by automatically determining a suitable position for irradiation with the illumination light 2 to extract an edge of the measurement target location.

[0079] In the present embodiment, a description has been given of an example of the laterally emitting illumination device 40, which reflects illumination light emitted by the light source 42 in the direction of the photoaxis through the mirror 44 in the direction intersecting the photoaxis. However, the present invention is not limited to this exemplary configuration of the laterally emitting illumination device 40. For example, the laterally emitting illumination device 40 can be provided without the mirror 44, and illumination light emitted in the horizontal direction by the light source 42 can be narrowed by the slot 46 to allow illumination with the illumination light 2, which has a diffraction angle close to parallel light.

[0080] Fig. Figure 13 is a sectional view showing another exemplary assembly of the side-emitting lighting device 40. This side-emitting lighting device 40 is composed of the wiring substrate 41, the light source 42, the lens tube section 43, and the slot 46. The lens tube section 43 has an interior space extending horizontally. The wiring substrate 41 and the light source 42 are arranged at a right end of the lens tube section 43, and the slot 46 is formed at the left end of the lens tube section 43.

[0081] The light source 42 is arranged on the wiring substrate 41 in a position where it is directed horizontally to the left. The slot 46 controls the spreading angle of the illumination light 2 emitted by the light source 42. The slot 46 is positioned at a certain distance from the light source 42. Even such a laterally emitting illumination device 40 enables the realization of an epi-illumination device that has a light quantity distribution that changes sharply in the directions of the photo axes of the cameras 110 and 120.

[0082] The Fig. 14A and Fig. Figure 14B shows sectional views, each showing a further exemplary assembly of the laterally emitting lighting device 40. Fig. Figure 14A shows the case in which illumination light 2, which has a spreading angle that is close to parallel light, is obtained using a condenser 47. Fig. Figure 14B shows a case in which illumination light 2 is obtained as parallel light using the light source 42, which generates laser light.

[0083] The laterally emitting lighting device 40, which is in Fig. The assembly shown in Figure 14A consists of the wiring substrate 41, the light source 42, the lens tube section 43, and the condenser 47. The lens tube section 43 has an interior that extends horizontally. The wiring substrate 41 and the light source 42 are located at the right end of the lens tube section 43, and the condenser 47 is located at the left end of the lens tube section 43.

[0084] The light source 42 is positioned on the wiring substrate 41 in such a way that it is directed horizontally to the left. The condenser 47 is an optical element that receives illumination 2, which has a beam angle close to parallel light, by collecting the illumination 2 emitted by the light source 42.

[0085] The laterally emitting lighting device 40, which is in Fig.The light source 42, shown in Figure 14B, is provided with a laser oscillator that generates laser light. The light source 42 is positioned horizontally facing the left side and illuminates the area with laser light emitted by the laser oscillator, which is parallel light. Even such a laterally emitting illumination device 40 enables the realization of an epi-illumination device that exhibits a light distribution which changes sharply in the directions of the photoaxis of cameras 110 and 120.

[0086] Furthermore, according to the present embodiment, a description was given regarding an example in which, based on several workpiece images to be photographed, while the relative position between the laterally emitting lighting device 40 and the movable table 12 is changed, the relative position which is to be associated with the measurement target location is determined.

[0087] However, in contrast, there is another method for determining the relative position associated with the measurement target location. For example, a height measuring unit that measures the height of the workpiece in the Z-axis direction can be provided, and the relative position associated with the measurement target location can be determined based on the height measurement result. Furthermore, the relative position associated with the measurement target location can be determined based on design information that specifies the shape and dimensions of the workpiece.

[0088] Furthermore, according to the present embodiment, a description of an example of determining the stability of edge extraction based on the contrast in the vicinity of the edge of the target measurement location was given. However, the present embodiment is not limited to this method for determining the stability of edge extraction. For example, an average illumination value can be obtained with respect to the target measurement location, and the stability of edge extraction can be assessed based on this average illumination value. As the average illumination value increases, the stability of edge extraction also increases. Alternatively, illumination unevenness can be obtained with respect to an area that differs from an area where the change in illumination at the target measurement location is large, and the stability of edge extraction can be assessed based on this illumination unevenness.When the lighting irregularity decreases, the stability of the edge extraction increases.

[0089] Furthermore, according to the present embodiment, a description of an example was given in which, when the measurement target location is specified based on user input, the workpiece images are obtained by photographing the workpiece on the movable table 12 while the relative position between the laterally emitting illumination device 40 and the movable table 12 is changed, and the relative position associated with the measurement target location is determined based on the obtained plurality of workpiece images. However, in contrast, another method for determining the relative position associated with the measurement target location is possible.For example, the setup can be designed such that the workpiece images are obtained by photographing the workpiece on the movable table 12 while the relative position between the laterally emitting illumination device 40 and the movable table 12 is changed, and edge extraction is performed on each of the obtained workpiece images to display a group of edges extracted from the multiple workpiece images on a common workpiece image. From such a group of edges, one edge is specified as the measurement target.

[0090] Furthermore, according to the present embodiment, a description of an example was given in which the lighting position adjustment element 103 adjusts the position of the ring lighting unit 140 in the direction of the Z-axis, thereby adjusting the relative position between the side-emitting lighting device 40 and the movable table 12. However, the present invention is not limited to this configuration of the relative position adjustment element. For example, the relative position adjustment element can be configured such that the movable table 12 is moved in the direction of the Z-axis, or the movable table 12 and the side-emitting lighting device 40 are moved separately in the direction of the Z-axis in order to adjust the relative position between the side-emitting lighting device 40 and the movable table 12.

[0091] The following numbered paragraphs describe further embodiments. 1. Image measuring device comprising: a table for arranging a workpiece; a camera that photographs the workpiece on the table and creates a workpiece image; a laterally emitting lighting device which has a light quantity distribution that changes sharply in the direction of a photo axis of the camera, and illuminates the workpiece on the table laterally with lighting light; a measurement target location specification unit, which specifies a measurement target location on the workpiece image; a relative position adjustment unit which moves the table or the side-emitting lighting device along the direction of the photo axis in order to set a relative position between the side-emitting lighting device and the table; a relative position determination unit which receives a change in the illumination at the measurement target location with respect to two or more workpiece images photographed at different relative positions in order to determine a relative position; an imaging control unit which sets the relative position adjustment unit based on the determined relative position and actuates the side-emitting illumination device to obtain the workpiece image; and a dimensional measuring unit that extracts an edge of the measurement target location based on the obtained workpiece image in order to obtain a dimension of the measurement target location based on the extracted edge.

[0092] 2. Image measuring device according to 1, in which the laterally emitting illumination device performs irradiation with illumination light as parallel light or illumination light having a spreading angle that is close to parallel light, wherein the illumination light has a range of change at a peripheral part of the light quantity distribution which is narrower than a depth of field of the camera.

[0093] 3. Image measuring device according to 2, in which the laterally emitting illumination device performs irradiation with the illumination light in an area that is narrower than the depth of field.

[0094] 4. Image measuring device according to one of the preceding ones, in which the side-emitting illumination device has: a mirror that reflects illumination light emitted in the direction of the photo axis from a light source in a direction that intersects the direction of the photo axis, and a slit that limits the angle of spread of the illumination light reflected by the mirror.

[0095] 5. Image measuring device according to 4, in which the slot of the laterally emitting illumination device is a slit that is narrower than the depth of field of the camera.

[0096] 6. Image measuring device according to 4, which has a diffuse illumination device having a ring-shaped light source which surrounds the photo axis of the camera and illuminates the workpiece on the table with diffuse light from above, wherein The laterally emitting illumination device has a light source which is arranged concentrically with respect to the light source of the diffuse illumination device and whose slot is provided in a stepped part which is formed by a lens tube part projecting more strongly in the direction of the photo axis than the lower end of the diffuse illumination device.

[0097] 7. Image measuring device according to 6, in which the measurement target location specification unit specifies as measurement target location an area on the workpiece image which is photographed under irradiation with the diffuse light of the diffuse illumination device.

[0098] 8. Image measuring device according to one of the preceding ones, comprising a measurement location information storage unit which stores two or more of the measurement target locations in conjunction with relative positions, wherein With respect to each measurement target location stored in the measurement location information storage unit, the imaging control unit repeatedly moves the table or the side-emitting illumination device to the corresponding relative position and illuminates the workpiece on the table laterally with the illumination light of the side-emitting illumination device in order to obtain the workpiece image.

[0099] 9. Image measuring device according to one of the preceding ones, in which the relative position determination unit obtains a contrast in a vicinity of an edge of the measurement target location with respect to each of a plurality of workpiece images photographed under irradiation with the illumination light of the laterally emitting illumination device, in order to determine a relative position to be associated with the measurement target location based on the obtained contrasts.

[0100] 10. Image measuring device according to one of the preceding ones, wherein the imaging control unit controls the relative position setting unit so that a position of the irradiation with the illumination light corresponds to a focus position of the camera in order to obtain the workpiece image.

Claims

[1] Image measuring device (1) comprising: a table (12) for arranging a workpiece; a camera (110, 120) which photographs the workpiece on the table (12) and creates a workpiece image; a transmission illumination unit (150) arranged in a housing (100) for irradiating the workpiece on the table (12) with illumination light from below the table (12); a ring illumination unit (140) integrated with a diffuse illumination device (50) and a side-emitting illumination device (40), wherein the diffuse illumination device (50) is ring-shaped, surrounds the photo axis of the camera (110, 120) and has a ring-shaped optical diffuser (53), and the side-emitting illumination device (40) irradiates the workpiece on the table (12) with illumination light from the side of the workpiece through a slit (46) provided below the diffuse illumination device (50) in the direction of the photo axis; a relative position adjusting unit (101, 103) which moves the ring illumination unit (140) along the direction of the photo axis to adjust a relative position between the ring illumination unit (140) and the table (12); an execution switch (16) arranged on the housing (100); an imaging control unit (21) adapted to move, in response to an operation of the execution switch (16), the relative position setting unit (101, 103) based on measurement setting data to move the ring illumination unit (140) to a relative position corresponding to a measurement target location and to obtain the workpiece image; and a dimension measuring unit (26) adapted to extract an edge of the measurement target location based on the obtained workpiece image and to obtain a dimension of the measurement target location based on the extracted edge. [2] Image measuring device (1) according to claim 1, wherein the diffuse illumination device (50) comprises an annular light source (52) which surrounds the photo axis of the camera (110, 120) and irradiates a workpiece on the table (12) via the annular optical diffuser (53), and the side-emitting illumination device (40) comprises a light source (42) which is arranged concentrically with the annular light source (52) of the diffuse illumination device (50) and irradiates a workpiece on the table (12) through the slit (46). [3] The image measuring device (1) according to claim 2, wherein the side-emitting illumination device (40) further comprises a diffusion plate (45) formed in a cylindrical shape extending in the direction of the photographing axis and diffusing light from the light source (42) in the circumferential direction. [4] Image measuring device (1) according to one of claims 1 to 3, wherein the annular optical diffuser (53) is formed from an arcuate curved plane which has an arc shape in a section in a vertical plane parallel to the photographic axis. [5] The image measuring device (1) according to any one of claims 1 to 4, wherein the side-emitting illumination device (40) performs irradiation with illumination light as parallel light or illumination light having an expansion angle close to parallel light, the illumination light having a change range at a peripheral part of the light quantity distribution which is narrower than a depth of field of the camera (110, 120). [6] Image measuring device (1) according to claim 5, wherein the side-emitting illumination device (40) performs irradiation with the illumination light in a region which is narrower than the depth of field. [7] Image measuring device (1) according to one of the preceding claims, in which the side-emitting illumination device (40) comprises: a mirror (44) which reflects illuminating light emitted in the direction of the photo axis from a light source in a direction which intersects the direction of the photo axis, and the slot (46) limits an expansion angle of the illumination light reflected by the mirror (44). [8] Image measuring device (1) according to one of the preceding claims, comprising a measurement location information storage unit (24) which stores two or more of the measurement target locations in association with relative positions, wherein with respect to each measurement target location stored in the measurement location information storage unit (24), the imaging control unit (21) repeatedly moves the table (12) or the ring illumination unit (140) to the corresponding relative position and laterally illuminates the workpiece on the table (12) with the illumination light of the side-emitting illumination device (40) to obtain the workpiece image. [9] The image measuring device (1) according to any one of the preceding claims, wherein the relative position detecting unit (25) obtains a contrast in a vicinity of an edge of the measurement target location with respect to each of a plurality of workpiece images photographed under irradiation with the illumination light of the side-emitting illumination device (40) to detect a relative position to be associated with the measurement target location based on the obtained contrasts. [10] Image measuring device (1) according to one of the preceding claims, wherein the imaging control unit (21) controls the relative position setting unit (101, 103) so that a position of irradiation with the illumination light coincides with a focus position of the camera (110, 120) to obtain the workpiece image.

Images