Image measuring device

Abstract

Image measuring device which features: 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 setting unit which moves the table or the side-emitting lighting device along the direction of the photo axes 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, and in which the laterally emitting illumination device performs an irradiation with illumination light as parallel light or illumination light having a spreading angle close to parallel light, wherein the illumination light has a change range at a peripheral part of the light quantity distribution which is narrower than a depth of field of the camera.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to an image measuring device, and more particularly to an improvement in an image measuring device which extracts an edge in a workpiece image obtained by photographing a workpiece 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 a workpiece image and extracts or detects an edge in the workpiece image to measure a dimension and a shape of the workpiece (for example, JP 2012-32224 A, JP 2012-32341 A, JP 2012-32344 A, JP 2012-159409 A, JP 2012-159410 A, and DE 198 09 505 A1). Typically, the workpiece is placed on a movable table that is movable in the X-, Y-, and Z-axis directions. By moving the movable table in the Z-axis direction, the workpiece image is brought into focus, and by moving the movable table in the X- or Y-axis directions, a position of the workpiece within a field of view is adjusted.

[0003] Since the workpiece image is a highly accurate replica of the workpiece, regardless of the position of the movable table in the Z-axis direction, determining a distance and an angle in the workpiece image enables the detection of an actual dimension of the workpiece. Edge extraction is performed by analyzing a change in illumination of the workpiece image, detecting edge points, and fitting a geometric figure such as a straight line, a circle, or an arc to the detected multiple edge points, thereby obtaining an edge that marks a boundary between the workpiece and a background and a roughness on the workpiece. The dimension of the workpiece is obtained as a distance or an angle between the edges thus obtained, or a central position or a 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 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 stage with illumination light from the opposite side of a camera. On the other hand, when measuring a non-through hole, a step, and roughness of the workpiece, epi-illumination is often used to illuminate the workpiece on the stage with illumination light from the same side as the camera.

[0005] With conventional image measurement equipment, a texture on the workpiece surface, such as a machining mark, pattern, or fine roughness, may be mistakenly extracted as an edge when determining the dimension using epi-illumination, making it difficult to stabilize the dimensional measurement compared to the case of using transmission illumination, which has been problematic. Especially when photographing the workpiece on the stage using a camera with low photographing magnification, an edge cannot be stably extracted, which has been problematic. Typically, a vertical plane parallel to the camera's photographing axis is extracted as an edge during dimensional measurement.However, because the camera has a high depth of field at low photo magnification, even if the top of the vertical plane was originally brought into focus, the bottom of the vertical plane would also be brought into focus. Consequently, accurate edge extraction was difficult, as it was influenced not only by a texture at the top of the vertical plane, but also by a texture at the bottom of the vertical plane. SUMMARY OF THE INVENTION

[0006] The present invention was made in view of the above circumstances, and an object thereof is to provide an image measuring device capable of performing stable edge extraction. Specifically, an object thereof is to provide an image measuring device capable of reducing erroneous extraction of a texture on a workpiece surface as an edge in dimensional measurement using epi-illumination. Furthermore, an object thereof is to provide an image measuring device capable of correctly extracting a step as an edge in the case of measuring a workpiece having the step in a direction of the photographing axis of a camera.

[0007] An image measuring device according to an embodiment of the invention comprises: a table for placing a workpiece; a camera that photographs the workpiece on the table and generates a workpiece image; a side-emitting illuminator that has a light quantity distribution that changes sharply in a direction of the camera's photographic axis and irradiates the workpiece on the table from the side; a measurement target location specifying unit that specifies a measurement target location on the workpiece image; a relative position adjusting unit that moves the table or the side-emitting illuminator in the direction of the photographic axis to adjust a relative position between the side-emitting illuminator and the table;A relative position detection unit that obtains a change in illumination at the measurement target location with respect to two or more workpiece images photographed with a change in relative position to detect a relative position; an imaging control unit that controls the relative position setting unit based on the detected relative position and operates the side-emitting illuminator to obtain the workpiece image; and a dimension measurement unit that extracts an edge of the measurement target location based on the obtained workpiece image to obtain a dimension of the measurement target location based on the extracted edge.

[0008] With this image measuring device, the illumination position of the workpiece on the table can be localized in the direction of the camera's photo axis using the illumination light, since the side-emitting illumination device has a light quantity distribution that changes sharply or rapidly in the direction of the camera's photo axis. For example, when measuring a workpiece with a step in the direction of the photo axis, the workpiece can be illuminated by irradiating either an upper end or a lower end of the step with the illumination light. Localizing the irradiation position with the illumination light in this way can prevent the influence of a texture at a position distant from the measurement target in the direction of the photo axis. Therefore, in dimensional measurement using epi-illumination, it is possible to reduce the erroneous extraction of the texture on the workpiece surface as an edge.

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

[0010] Furthermore, a change in illumination of the measurement target location is obtained with respect to two or more workpiece images photographed while changing the relative position, and the relative position is then detected, whereby it is possible to automatically detect a suitable irradiation position with the illumination light for extracting an edge of the measurement target location and to photograph the workpiece.

[0011] In addition to the above structure, the image measuring device according to the invention is constructed such that the side-emitting illumination means performs illumination with illumination light as parallel light or with illumination light having an expansion angle close to parallel light, the illumination light having a change range to a peripheral part of the light quantity distribution which is narrower than a depth of field of the camera.

[0012] With such a setup, by adjusting the relative position of the side-emitting illuminator so that a boundary of the illuminating 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 located away from the measurement target location.

[0013] In addition to the above configuration, an image measuring device according to another embodiment of the invention may be configured such that the side-emitting illumination device performs illumination light irradiation in a range narrower than the depth of field. With such a configuration, it is possible to perform illumination within the depth of field of the camera at a fine point (pinpoint) with respect to the direction of the photographic axis, so that an edge within the depth of field can be accurately extracted.

[0014] In addition to the above structure, an image measuring device according to still another embodiment of the invention may be constructed such that the side-emitting illumination device includes a mirror that reflects illumination light emitted from a light source in the direction of the photographic axis in a direction intersecting the direction of the photographic axis, and a slit that limits an expanding 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 structure makes it possible to reduce the size of the side-emitting illumination device in a direction intersecting the direction of the photoaxis. Furthermore, by limiting the expansion angle of the illumination light by the slit, it is possible to perform irradiation with illumination light that is closer to parallel light.

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

[0017] In addition to the above structure, an image measuring device according to still another embodiment of the invention comprises a diffuse illumination device having an annular light source surrounding the photographing axis of the camera and irradiating the workpiece on the table with diffused light from above, wherein the side-emitting illumination device has a light source arranged concentrically with respect to the light source of the diffuse illumination device, and is provided with the slit in a step part formed by protruding a lens barrel part in the direction of the photographing axis more than the lower end of the diffuse illumination device.

[0018] Since the light source of the side-emitting illuminator is arranged concentrically with the light source of the diffuse illuminator, such a structure makes it possible to illuminate the periphery or surroundings of the workpiece from the side. Furthermore, since the slit is formed in the stepped portion formed by protruding the lens barrel portion more in the direction of the photographic axis than the bottom end of the diffuse illuminator, it is possible to arrange the diffuse illuminator and the side-emitting illuminator without increasing the size of the side-emitting illuminator in the direction intersecting the photographic axis.

[0019] In addition to the above configuration, an image measuring device according to yet another embodiment of the invention may be configured such that the measurement target location specifying unit specifies a region on the workpiece image photographed under irradiation with diffused light from the diffuse illumination device as the measurement target location. With such a configuration, using the workpiece image photographed under irradiation with the diffused light, it is possible to specify the measurement target location while inspecting the entire image of the workpiece.

[0020] In addition to the above structure, an image measuring device according to yet another embodiment of the present invention may include a measurement target information storage unit that stores two or more measurement target locations in association with relative positions. The imaging control unit repeatedly moves the stage or the side-emitting illuminator to the corresponding relative position for each measurement target location stored in the measurement target information storage unit, and irradiates the workpiece on the stage with the illumination light of the side-emitting illuminator from one side to obtain the workpiece image. With such a structure, when multiple measurement target locations are specified on the same workpiece image, it is possible to sequentially extract edges of these measurement target locations while adjusting the relative position between the side-emitting illuminator and the stage.

[0021] In addition to the above configuration, an image measuring device according to yet another embodiment of the invention may be configured such that the relative position detection 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 irradiated by irradiation with the illumination light from the side-emitting illumination device, to detect a relative position to be associated with the measurement target location based on the obtained contrasts. According to such a configuration, it is possible to improve the stability of edge extraction by detecting a relative position to be associated with the measurement target location based on a relative position at which a workpiece image with a high contrast was photographed from among the plurality of workpiece images photographed while changing the relative position.

[0022] In addition to the above configuration, an image measuring device according to yet another embodiment of the invention may be configured such that the imaging control unit controls the relative position adjustment unit so that a position of irradiation with the illumination light coincides with a focus position of the camera to obtain the workpiece image. With such a configuration, it is possible to correctly extract an edge in an in-focus image area.

[0023] According to the present invention, it is possible to provide an image measuring device capable of performing stable edge extraction. In particular, since an influence of a texture located away from a measurement target in a direction of the photographic axis is avoided, it is possible to provide an image measuring device capable of reducing erroneous extraction of a texture on the workpiece surface as an edge in dimensional measurement using epi-illumination. Furthermore, it is possible to provide an image measuring device capable of correctly extracting a step as an edge in the case of measuring a workpiece having a step in a direction of the photographic axis of a camera. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an exemplary structure of an image measuring device 1 according to an embodiment of the present invention; Fig. Fig. 2 is an explanatory view showing an exemplary structure of a measuring unit 10 of the Fig. 1 schematically shows a cutting plane in the case of cutting the measuring unit 10 by means of a vertical plane parallel to a photo axis; Fig. 3 is a sectional view showing an exemplary structure of a ring lighting unit 140 of the Fig. 2 shows; Fig. Fig. 4 is a diagram showing an example of a light quantity distribution of a side-emitting illumination device 40 of the Fig. 3 shows; Fig. Fig. 5 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2 and shows a case where an upper end part of the workpiece W on a movable table 12 is irradiated with illumination light 2 of the side-emitting illumination; Fig. Fig. 6 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2 and shows a workpiece image that is in the state of Fig. 5 is photographed; Fig. Fig. 7 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2 and shows a case where an intermediate part of the workpiece W on the movable table 12 is irradiated with the illumination light 2 of the side-emitting illumination; Fig. Fig. 8 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2 and shows a workpiece image that is in the state of Fig. 7 is photographed; Fig. 9 is a block diagram showing an example of a functional structure of a control unit 20 of the Fig. 1 shows; Fig. 10 is a flowchart showing an example of the operation of the image measuring device 1 of the Fig. 1 at the time of measurement setting; Fig. 11 is a flowchart showing an example of the operation of the image measuring device 1 of the Fig. 1 at the time of measurement setting; Fig. 12 is a flowchart showing an example of the operation of the image measuring device 1 of the Fig. 1 at the time of a dimensional measurement; Fig. 13 is a sectional view showing another exemplary structure of the side-emitting illumination device 40; and Fig. 14A and Fig. 14B are sectional views each showing another exemplary structure of the side-emitting illumination device 40. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS<Bildmesseinrichtung 1>

[0024] Fig. 1 is a perspective view showing an exemplary configuration of an image measuring device 1 according to an embodiment of the present invention. This image measuring device 1 is a dimension measuring device that extracts an edge in a workpiece image obtained by photographing a workpiece to measure a dimension of the workpiece. The image measuring device 1 is configured by 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 includes a display device 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 irradiates the workpiece on the movable table 12 with measurement light, which is visible light, and receives the transmitted light or reflected light to generate a workpiece image. The workpiece is placed in 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 device 11.

[0026] The display device 11 is a display device that displays a workpiece image or a measurement result on the display 11a. The movable table 12 is a placement table for arranging the workpiece and is provided 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 Z-axis direction, which is parallel to a camera's photographic axis, and in an X-axis direction and a Y-axis direction, which are vertical to the photographic axis.

[0027] The XY adjustment knob 14a is an operation part for moving the movable table 12 in the X-axis direction or the Y-axis direction to adjust the position in the X-axis direction and the Y-axis direction. The Z adjustment knob 14b is an operation part for moving the movable table 12 in the Z-axis direction to adjust the position in the Z-axis direction. The power switch 15 is an operation part 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 an operation part for starting the dimensional measurement.

[0028] The control unit 20 is a control part that controls 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 is turned on, if the workpiece is placed in the detection area 13 and the execution switch 16 is pressed, the dimension of the workpiece is automatically measured. <Messeinheit 10>

[0029] Fig. Fig. 2 is an explanatory view showing an exemplary structure of the measuring unit 10 of the Fig. 1 schematically shows a section plane in the case of cutting the measuring unit 10 by a vertical plane parallel to the photo axis. This measuring unit 10 is constructed by the display device 11, the movable stage 12, a housing 100, a stage adjustment part 101, a lens barrel 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 stage adjustment part 101, the lens barrel part 102, the cameras 110, 120, the coaxial epi-illumination unit 130, and the transmission illumination unit 150 are arranged in the housing 100. The stage adjustment part 101 moves the movable stage 12 in the X-, Y-, or Z-axis directions based on an operation signal from the control unit 20, and adjusts the position of the workpiece in the X-, Y-, and Z-axis directions.

[0031] The camera 110 is an imaging device with low photographic magnification and is composed of an imaging element 111, an image forming lens 112, a diaphragm 113, and a light receiving lens 114. The imaging element 111 receives detection light and forms a workpiece image. This imaging element 111 is arranged with its light receiving surface facing downward. The image forming lens 112 is an optical element that forms an image with the detection light on the imaging element 111. The diaphragm 113 is an optical diaphragm that limits the transmitted light amount and is arranged 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 to the movable table 12.The image forming lens 112, the aperture 113 and the light receiving lens 114 are arranged with a vertically extending central axis as the center.

[0032] The camera 120 is a high-magnification imaging device composed of an imaging element 121, an image forming lens 122, a diaphragm 123, a beam splitter 124, and a light-receiving lens 114. The imaging element 121 receives detection light and forms a workpiece image. This imaging element 121 is arranged with its light-receiving surface facing a horizontal direction. The image forming lens 122 is an optical element that forms an image with the detection light and the imaging element 121. The diaphragm 123 is an optical diaphragm that limits the transmitted light amount of the detection light and is arranged 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 forming lens 122.

[0033] An image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is used as the imaging elements 111 and 121. 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 changes in the vertical direction, i.e., the direction of the photo axis.

[0034] The coaxial epi-illumination unit 130 is an epi-illumination device that irradiates the workpiece on the movable table 12 with illumination light from above and aligns the optical axis of the illumination light with the photo-axis. This coaxial epi-illumination unit 130 is composed of a light source 131 arranged to face the horizontal direction and a beam splitter 132 that deflects the illumination light emitted from the light source 131 downward.

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

[0036] The transmission illumination unit 150 is a transmission illumination device that irradiates the workpiece on the movable table 12 with illumination light from below. It is composed of a light source 151, a mirror 152, and a condenser 153. The light source 151 is arranged facing the horizontal direction. Illumination light emitted from the light source 151 is reflected by the mirror 152 and emitted via the condenser 153. This illumination light is transmitted through the movable table 12, and part of the transmitted light is shielded by the workpiece, while another part is incident on the light-receiving lens 114.

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

[0038] Fig. 3 is a sectional view showing an exemplary structure of the ring lighting unit 140 of the Fig. 2. This ring illumination unit 140 is an illumination device formed by coaxially arranging a side-emitting illumination device 40 that performs illumination from the side with illumination light 2 having an expansion angle close to parallel light, and a diffuse illumination device 50 that performs irradiation with diffuse light.

[0039] The side-emitting illuminator 40 is an epi-illuminator composed of a wiring substrate 41, a light source 42, a lens barrel portion 43, a mirror 44, a diffusion plate 45, and a slit 46. The illuminant distribution varies sharply in the direction of the photoaxis. The lens barrel portion 43 is formed with a cylindrical interior space extending in the direction of the photoaxis and accommodating 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 lid portion of the lens barrel portion 43, and the mirror 44, the diffusion plate 45, and the slit 46 are arranged at the bottom of the lens barrel portion 43. The light source 42 is arranged on the wiring substrate 41 in a downward-facing state. For example, an LED (light-emitting diode) is used as the light source 42. The light source 42 is a ring-shaped light source with two or more LEDs arranged on its circumference.

[0041] The mirror 44 is an optical element that reflects the illumination light 2 emitted in the direction of the photographic axis from the light source 42 in a direction intersecting the photographic axis. This mirror 44 is formed from an annular reflecting plate and is arranged at an inclination of approximately 45 degrees. Since the illumination light 2 emitted from the light source 42 is deflected by the mirror 44, it is possible to reduce the size of the side-emitting illuminator 40 in the direction intersecting the photographic axis while ensuring an optical path from the light source 42 to the slit 46.

[0042] The slit 46 is an expansion angle limiting part that limits the expansion angle of the illumination light 2 reflected by the mirror 44. The slit 46 is a gap in the direction of the photographing axis and is formed in a shape extending in a circumferential direction. The slit 46 is arranged at a position a certain distance away from the light source 42. By limiting the expansion angle of the illumination light 2 by the slit 46, it is possible to perform irradiation with illumination light 2 that is closer to parallel light. For example, the slit 46 is formed as a gap narrower than a depth of field of the camera 110 for low-magnification photography.

[0043] The diffusion plate 45 is a diffusion plate with a high aspect ratio that diffuses the illumination light 2 in the circumferential direction and is arranged between the mirror 44 and the slit 46. This diffusion plate 45 is formed in a cylindrical shape extending in the direction of the photoaxis. By disposing such a diffusion plate 45, it is possible to prevent the occurrence of an uneven amount of light in the circumferential direction, even when the light source 42 has a large number of individually arranged LEDs.

[0044] The optical axis of the illumination light 2 emitted from a light projection window of the side-emitting illumination device 40 is inclined with respect to the horizontal direction within a 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 a range of 30°.

[0045] The diffuse illumination device 50 is an epi-illumination device constructed by a wiring substrate 51, a light source 52, and a diffusion plate 53. The light source 52 is an annular light source surrounding the photo axes of the cameras 110 and 120. The light source 52 is arranged on the wiring substrate 51 in a state where it faces downward. The diffusion plate 53 is an optical element that diffuses illumination light emitted from the light source 52 in a circumferential direction or a radial direction. This diffusion plate 53 has a ring shape, and its cross-sectional shape with respect to a vertical plane parallel to the photo axis is formed of an arcuate curved plane. The workpiece on the movable table 12 is irradiated with the diffused light from above or from the side.

[0046] The lens barrel portion 43 of the side-emitting illuminator 40 is formed radially outward from the diffuse illuminator 50, and the light source 42 is arranged concentrically with respect to the light source 52 of the diffuse illuminator 50. Furthermore, the slit 46 is formed in a stepped portion 3, which is formed by protruding the lens barrel portion 43 in the direction of the photographic axis more than the lower end of the diffuse illuminator 50. Since the light source 42 of the side-emitting illuminator 40 is arranged concentrically with respect to the light source 52 of the diffuse illuminator 50, the periphery of the workpiece can be illuminated from the side.Furthermore, since the slit 46 is formed in the step part 3, the diffuse illuminator 50 and the side-emitting illuminator 40 can be arranged without increasing the dimension of the side-emitting illuminator 40 in the direction intersecting the direction of the photographing axis.

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

[0048] The light quantity distribution of the illumination light 2 corresponds to an illumination intensity distribution on the workpiece in the case where the workpiece on the movable table 12 is irradiated with the illumination light 2. The light quantity has the maximum value Km at the position Z0 in the Z-axis direction and decreases rapidly or sharply with increasing distance from the position Z0. From the viewpoint of extracting a fine roughness as an edge by establishing a clear boundary between an irradiation area and a non-irradiation area with the illumination light 2, it is more preferable that the change ranges ΔZa and ΔZb are narrower at a peripheral region of the light quantity distribution.

[0049] For example, each of the change ranges ΔZa and ΔZb is a range where 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 the camera 110 for low-magnification photography. With such a configuration, 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 by adjusting the relative position of the ring illumination unit 140 so that a boundary of the illumination light 2 is located within the depth of field of the camera 110.

[0050] Furthermore, a width ΔZc of the illumination light 2 in the Z-axis direction 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 irradiated with the illumination light 2. With such a configuration, it is possible to perform illumination within the depth of field of the camera 110 at a fine point (pinpoint) with respect to the direction of the photographing axis to extract an edge within the depth of field.

[0051] Fig. Fig. 5 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2, and this shows a case where an upper end part of the workpiece W on the movable table 12 is irradiated with the illumination light 2 of the side-emitting illumination. Furthermore, Fig. 6 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2, and this shows a workpiece image that is in the state of Fig. 5 is photographed.

[0052] Since the side-emitting illuminator 40 has a light quantity distribution that changes sharply in the direction of the photographic axis, an irradiation position of the workpiece W on the movable stage 12 with the illumination light 2 can be localized in the direction of the photographic axis. Therefore, in the case of measuring a workpiece W having a step in the direction of the photographic axis, the workpiece W can be photographed by irradiating only the upper end portion of the step with the illumination light 2.

[0053] In this case, only the upper end part of the workpiece W is irradiated with the illumination light 2, and in the workpiece image, the illumination changes significantly in the vicinity of the upper end edge. Localizing the position of the irradiation with the illumination light 2 in this way can prevent the influence of a texture at a position located away from the measurement target in the direction of the photo axis.

[0054] Fig. Fig. 7 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2, and this shows a case where an intermediate part of the workpiece W on the movable table 12 is irradiated with the illumination light 2 of the side-emitting illumination. Furthermore, Fig. 8 is a view showing an example of the operation of the measuring unit 10 of the Fig. 2, 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 irradiated with the illumination light 2, and in the workpiece image, the illumination in the vicinity of the edge of the intermediate part changes significantly. Localizing the position of the irradiation with the illumination light 2 in this way can prevent the influence of a texture at a position located away from the measurement target in the direction of the photo axis. <Steuereinheit 20>

[0056] Fig. 9 is a block diagram showing an example of a functional structure in the control unit 20 of the Fig. 1. This control unit 20 is constructed 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 detection part 25, and a dimension measurement part 26.

[0057] The imaging control part 21 controls the cameras 110, 120, the illumination position setting part 103, and the illumination units 130 to 150 based on the user's control to obtain a workpiece image from the cameras 110, 120, and stores the workpiece image in the workpiece image storage part 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 photographed under irradiation with the diffused light of the diffuse illumination device 50. By using the workpiece image photographed under irradiation with the diffused light, it is possible to specify the measurement target location while inspecting the entire image of the workpiece. Position information indicating the measurement target location and a measurement type is stored as measurement location information in the measurement location information storage part 24.

[0059] The relative position detection part 25 obtains a change in illumination at the measurement target location relative to two or more workpiece images photographed while changing the relative position between the side-emitting illuminator 40 and the movable table 12 to detect the relative position. The above two or more workpiece images are workpiece images obtained by photographing the same workpiece using illumination by the side-emitting illuminator 40.For example, the relative position detecting part 25 obtains a contrast of an image at the measurement target location with respect to each of a plurality of workpiece images photographed under irradiation with the illumination light 2 by the side-emitting illumination device 40, and compares the obtained contrasts to detect a relative position at which the workpiece image with the largest contrast was photographed as a relative position to be associated with the measurement target location.

[0060] Generally speaking, the higher the image contrast, the more stable the edge extraction is. Such a contrast of the measurement target location is obtained as an evaluation value indicating the stability of the edge extraction. A workpiece image with the highest evaluation value, that is, a workpiece image with the highest contrast, is extracted from a plurality of workpiece images photographed while changing the relative position of the side-emitting illuminator 40, and the relative position is then detected, thereby enabling an improvement in the stability of the edge extraction.

[0061] Furthermore, as a method for determining the relative position to be associated with the measurement target location, there is a method different from the above-mentioned method in which a workpiece image having the highest contrast at the measurement target location is determined from a plurality of workpiece images, and a relative position at which the workpiece image was obtained is determined as the above relative position. For example, however, the configuration may be such that, based on three or more workpiece images having different relative positions between the side-emitting illuminator 40 and the movable stage 12, a distribution including 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 a contrast is greatest.

[0062] In the measurement location information storage part 24, two or more measurement target locations are stored along with relative positions. The measurement target location and the relative position are stored as measurement location information. The imaging control part 21 controls the illumination position setting part 103 based on the relative position determined by the relative position determination part 25 and actuates the side-emitting illuminator 40 to obtain a workpiece image. Based on the workpiece image obtained by the imaging control part 21, the dimension measurement part 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 photographed while changing the relative position between the side-emitting illumination device 40 and the movable table 12, it is possible to photograph the workpiece by automatically determining an appropriate 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 storage section 24, the imaging control section 21 moves the side-emitting illuminator 40 to the corresponding relative position and repeatedly illuminates the workpiece on the movable table 12 with illumination light 2 from the side-emitting illuminator 40 to obtain the workpiece image. With such a configuration, when multiple measurement target locations are specified with respect to the same workpiece image, edges of these measurement target locations can be extracted sequentially while adjusting the relative position between the side-emitting illuminator 40 and the movable table 12.

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

[0066] A measurement result, such as a dimension value, is displayed on the display device 11. Furthermore, the control unit 20 generates measurement setting data for sequentially or repeatedly measuring the workpiece. This measurement setting data includes positioning information, measurement location information, information indicating a design value, and a tolerance for each measurement target location. The position information is information for analyzing a workpiece image to detect a position and orientation of the workpiece.

[0067] The Fig. 10 and Fig. 11 with steps S101 to S115 are flowcharts showing an example of the operation sequence at the time of measurement setting of the image measuring device 1 of the Fig. 1. First, the control unit 20 activates the diffuse illumination device 50 of the ring illumination 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 input, and if a measurement target location is specified on the workpiece image (step S103), the control unit 20 operates the side-emitting illuminator 40 instead of the diffuse illuminator 50 and photographs the workpiece on the movable table 12 using the camera 110 (steps S104, S105). Based on the workpiece image photographed from the side under irradiation with the illumination light 2, the control unit 20 obtains a change in illumination at the measurement target location and calculates a contrast in the vicinity of the edge as an evaluation value indicating the stability of the edge extraction (step S106).

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

[0070] Next, to adjust the illumination position, the control unit 20 controls the illumination position adjustment part 103 to move the ring illumination unit 140 to the relative position obtained from the judgment 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 of the measurement target location based on the extracted edge (step S112) 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 subsequent steps (step S114). When the dimensional measurement is completed for 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 showing an example of the operation sequence at the time of dimension measurement in the image measuring device 1 of the Fig. 1. First, the control unit 20 accepts the user's input and selects measurement setting data according to the workpiece as a subsequent measurement target (step S201).

[0074] Next, when the execution switch 16 of the measuring unit 10 is operated (step S202), the control unit 20 reads the measurement target location stored as measurement setting data (step S203) and controls the illumination position setting part 103 to adjust the illumination position, moving 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 based on the obtained workpiece image (step S206) and calculates a dimensional value of the measurement target based on the extracted edge (step S207). If another measurement target exists, the control unit 20 repeats the processing procedure from step S203 to step S207 (step S208). When the dimensional measurement with respect to all measurement targets is completed, 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] When there is another workpiece as the subsequent measurement target, the control unit 20 repeats the processing procedure of step S202 and subsequent steps, and when there is no another workpiece as the subsequent measurement target, the control unit 20 completes this processing (step S211).

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

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

[0079] In the present embodiment, a description was given regarding an example of the side-emitting illuminator 40, which reflects illumination light emitted in the direction of the photographic axis from the light source 42 by the mirror 44 in the direction intersecting the photographic axis. However, the present invention is not limited to this exemplary configuration of the side-emitting illuminator 40. For example, the side-emitting illuminator 40 may be provided without the mirror 44, and illumination light emitted in the horizontal direction from the light source 42 may be narrowed by the slit 46 to perform irradiation with the illumination light 2 having an expansion angle close to parallel light.

[0080] Fig. 13 is a sectional view showing another exemplary structure of the side-emitting illuminator 40. This side-emitting illuminator 40 is configured by the wiring substrate 41, the light source 42, the lens barrel portion 43, and the slit 46. The lens barrel portion 43 has an internal space extending in the horizontal direction. The wiring substrate 41 and the light source 42 are arranged at a right end portion of the lens barrel portion 43, and the slit 46 is formed at the left end of the lens barrel portion 43.

[0081] The light source 42 is arranged on the wiring substrate 41 in a state where it is directed to the left side in the horizontal direction. The slit 46 controls the expansion angle of the illumination light 2 emitted from the light source 42. The slit 46 is arranged at a position a certain distance from the light source 42. Even such a side-emitting illumination device 40 enables the realization of an epi-illuminator having a light quantity distribution that changes sharply in the directions of the photo axis of the cameras 110 and 120.

[0082] The Fig. 14A and Fig. 14B are sectional views each showing another exemplary structure of the side-emitting illumination device 40. Fig. 14A shows the case where illumination light 2 having an expansion angle close to parallel light is obtained using a condenser 47. Fig. 14B shows a case where illumination light 2 is obtained as parallel light using the light source 42 which generates laser light.

[0083] The side-emitting illumination device 40, which is Fig. 14A is constructed by the wiring substrate 41, the light source 42, the lens barrel portion 43, and the condenser 47. The lens barrel portion 43 has an internal space extending in the horizontal direction. The wiring substrate 41 and the light source 42 are arranged at the right end portion of the lens barrel portion 43, and the condenser 47 is arranged at the left end of the lens barrel portion 43.

[0084] The light source 42 is arranged on the wiring substrate 41 in a state where it is directed to the left side in the horizontal direction. The condenser 47 is an optical element that receives illumination light 2, which has an expansion angle close to parallel light, by concentrating the illumination light 2 emitted from the light source 42.

[0085] The side-emitting illumination device 40, which is Fig.14B is constructed by the light source 42 provided with a laser oscillator that generates laser light. The light source 42 is arranged to face the left side in the horizontal direction and irradiates laser light emitted from the laser oscillator as the illumination light 2, which is parallel light. Even such a side-emitting illumination device 40 enables the realization of an epi-illuminator having a light quantity distribution that changes sharply in the directions of the photo-axis of the cameras 110 and 120.

[0086] Further, according to the present embodiment, a description has been given regarding an example in which the relative position to be associated with the measurement target location is determined based on a plurality of workpiece images to be photographed while changing the relative position between the side-emitting illumination device 40 and the movable table 12.

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

[0088] Furthermore, according to the present embodiment, a description has been given regarding an example of determining the stability of edge extraction based on the contrast in the vicinity of the edge of the measurement target. However, the present embodiment is not limited to this method of determining the stability of edge extraction. For example, an average value of illumination may be obtained with respect to the measurement target, and based on the average value of illumination, the stability of edge extraction may be judged. As the average value of illumination becomes larger, the stability of edge extraction increases. Alternatively, illumination unevenness may be obtained with respect to a region other than a region where a change amount of illumination at the measurement target is large, and based on the illumination unevenness, the stability of edge extraction may be judged.As the illumination non-uniformity decreases, the stability of edge extraction increases.

[0089] Furthermore, according to the present embodiment, a description has been given regarding an example 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 stage 12 while changing the relative position between the side-emitting illuminator 40 and the movable stage 12, and the relative position to be 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 to be associated with the measurement target location is possible.For example, the configuration may be such that workpiece images are obtained by photographing the workpiece on the movable table 12 while changing the relative position between the side-emitting illuminator 40 and the movable table 12. 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 a measurement target.

[0090] Furthermore, according to the present embodiment, a description has been given of an example in which the illumination position adjusting part 103 adjusts the position of the ring illumination unit 140 in the Z-axis direction, thereby adjusting the relative position between the side-emitting illuminator 40 and the movable stage 12. However, the present invention is not limited to this configuration of the relative position adjusting unit. For example, the relative position adjusting unit may be configured to move the movable stage 12 in the Z-axis direction, or to move the movable stage 12 and the side-emitting illuminator 40 separately in the Z-axis direction, thereby adjusting the relative position between the side-emitting illuminator 40 and the movable stage 12.

Claims

[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 side-emitting illuminator having a light quantity distribution that changes sharply in the direction of a photo axis of the camera and irradiates the workpiece on the table laterally with illuminating light; a measurement target location specification unit that specifies a measurement target location on the workpiece image; a relative position adjusting unit that moves the stage or the side-emitting illuminator along the direction of the photo axes to adjust a relative position between the side-emitting illuminator and the stage; a relative position detecting unit that receives a change in illumination at the measurement target location with respect to two or more workpiece images photographed at different relative positions to detect a relative position; an imaging control unit that adjusts 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 dimension measuring unit that extracts an edge of the measurement target location based on the obtained workpiece image to obtain a dimension of the measurement target location based on the extracted edge, and wherein the side-emitting illumination device 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 that is narrower than a depth of field of the camera. [2] An image measuring device according to claim 1, wherein the side-emitting illumination means irradiates the illumination light in a region narrower than the depth of field. [3] Image measuring device according to one of the preceding claims, in which the side-emitting illumination device comprises: a mirror that reflects illuminating 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 an expansion angle of the illumination light reflected by the mirror. [4] An image measuring device according to claim 3, wherein the slit of the side-emitting illumination device is a slit which is narrower than the depth of field of the camera. [5] An image measuring device according to claim 3, comprising a diffuse illumination device having an annular light source surrounding the photographic axis of the camera and irradiating the workpiece on the table with diffused light from above, wherein the side-emitting illumination device comprises a light source arranged concentrically with respect to the light source of the diffuse illumination device and whose slit is provided in a step part formed by projecting a lens barrel part in the direction of the photographic axis more than the lower end of the diffuse illumination device. [6] The image measuring device according to claim 5, wherein the measurement target location specifying unit specifies, as the measurement target location, an area on the workpiece image photographed under irradiation with the diffuse light of the diffuse illumination device. [7] An image measuring device according to any preceding claim, comprising a measurement location information storage unit storing 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, the imaging control unit repeatedly moves the stage or the side-emitting illuminator to the corresponding relative position and laterally illuminates the workpiece on the stage with the illuminating light of the side-emitting illuminator to obtain the workpiece image. [8] An image measuring device according to any preceding claim, wherein the relative position detecting 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 side-emitting illumination device to detect a relative position to be associated with the measurement target location based on the obtained contrasts. [9] An image measuring device according to any preceding claim, wherein the imaging control unit controls the relative position adjusting unit so that a position of irradiation with the illumination light coincides with a focus position of the camera to obtain the workpiece image.

Images