JP7616953B2 - Photographing device and photographing method - Google Patents

Description

The present invention relates to a technique for photographing transparent objects such as glass.

When measuring the position of a transparent object such as glass using a captured image of the transparent object, a lighting device that irradiates highly parallel light is generally placed on the other side of the transparent object as seen from the camera. This is because if light with low parallelism is irradiated onto the transparent object, some of the light will pass through the inside of the transparent object and reach the camera, as shown in Figure 1A, making it impossible to obtain a high-contrast image.

On the other hand, by shining highly parallel light onto a transparent object, a high-contrast image can be obtained.

JP 2014-157106 A

However, in order to irradiate a transparent object with highly parallel light, it is necessary to use a collimator lens as shown in Figure 1B, or to lengthen the optical path length from the lighting device to the transparent object as shown in Figure 1C, which requires a large space on the other side of the transparent object as seen from the camera. This reduces the freedom of design of the equipment, including the imaging device.

The shape measuring device disclosed in Patent Document 1 measures the edge of the wafer and the surface shape of the measurement area, and does not measure transparent objects such as glass. In other words, Patent Document 1 does not disclose any imaging technology that can obtain a high-contrast image when a transparent object such as glass is the subject of imaging.

In view of the above problems, the present invention aims to provide a photography technique that requires less space on the other side of a transparent body as viewed from the imaging unit and can obtain high-contrast images.

The imaging device according to the first aspect of the present invention includes an illumination device, a half mirror that reflects light irradiated from the illumination device, a plane mirror, a telecentric lens that collects light that is reflected by the half mirror, further reflected by the plane mirror or a transparent body, and then passes through the half mirror, and an imaging unit that receives the light collected by the telecentric lens, in which the narrow angle between the reflection surface of the half mirror and a virtual reference plane is approximately 45 degrees, the optical axis of the telecentric lens and the virtual reference plane are approximately perpendicular, and the reflection surface of the plane mirror is inclined with respect to the virtual reference plane so that the shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in the direction perpendicular to the virtual reference plane (first configuration).

In the imaging device of the first configuration described above, the narrow angle between the reflecting surface of the plane mirror and the virtual reference plane may be 0.5 degrees or more and 1.5 degrees or less (second configuration).

The imaging device according to the second aspect of the present invention includes an illumination device that irradiates light parallel to a virtual reference plane, a half mirror that reflects the light irradiated from the illumination device, a plane mirror, a telecentric lens that collects the light that is reflected by the half mirror and further reflected by the plane mirror or a transparent body and then passes through the half mirror, and an imaging unit that receives the light collected by the telecentric lens, in which the reflective surface of the plane mirror is parallel to the virtual reference plane, the reflective surface of the half mirror is inclined with respect to a narrow angle of 45 degrees with the virtual reference plane so that the shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in the direction perpendicular to the virtual reference plane (third configuration).

In the imaging device of the third configuration, the narrow angle between the reflecting surface of the half mirror and the virtual reference plane may be 43.5 degrees or more and 44.5 degrees or less, and the optical axis of the telecentric lens may be inclined by 0.5 degrees or more and 1.5 degrees or less with respect to the perpendicular direction of the virtual reference plane (fourth configuration).

In the imaging device of any of the first to fourth configurations described above, the distance between the plane mirror and the transparent body may be shorter than the distance between the telecentric lens and the transparent body (fifth configuration).

The imaging method according to the third aspect of the present invention includes a light collecting step of reflecting light irradiated from an illumination device by a half mirror, further reflecting the light by a plane mirror or a transparent body, and collecting the light that has passed through the half mirror by a telecentric lens, and a light receiving step of receiving the light collected by the telecentric lens by an imaging unit, in which the narrow angle between the reflecting surface of the half mirror and a virtual reference plane is approximately 45 degrees, the optical axis of the telecentric lens and the virtual reference plane are approximately perpendicular, and the reflecting surface of the plane mirror is inclined with respect to the virtual reference plane so that the shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in the direction perpendicular to the virtual reference plane (sixth configuration).

The imaging method according to the fourth aspect of the present invention includes a light collecting step of reflecting light parallel to a virtual reference plane irradiated from an illumination device by a half mirror, further reflecting the light by a plane mirror or a transparent body, and collecting the light that has passed through the half mirror by a telecentric lens, and a light receiving step of receiving the light collected by the telecentric lens by an imaging unit, in which the reflecting surface of the plane mirror is parallel to the virtual reference plane, the reflecting surface of the half mirror is inclined with respect to a direction in which the narrow angle it forms with the virtual reference plane is 45 degrees, and the optical axis of the telecentric lens is inclined with respect to the perpendicular direction to the virtual reference plane so that the shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in the perpendicular direction to the virtual reference plane (seventh configuration).

According to the present invention, the required space on the other side of the transparent body as seen from the imaging unit is small, and a high-contrast image can be obtained.

FIG. 1 is a diagram showing an example of a schematic configuration of a general imaging device for imaging a transparent object; FIG. 1 is a diagram showing another example of the schematic configuration of a general imaging device for imaging a transparent object; FIG. 13 is a diagram showing yet another example of the schematic configuration of a general imaging device for imaging a transparent object; FIG. 1 is a diagram showing an example of a schematic configuration of an imaging device according to a first embodiment; FIG. 1 is a diagram showing an example of a schematic configuration of an image capturing device according to a comparative example; FIG. 1 is a diagram showing an example of a photographed image taken by using an image taking device according to a comparative example; FIG. 1 is a diagram showing an example of a captured image captured by the imaging device according to the first embodiment; 1 is a flowchart showing a procedure for photographing using the photographing device according to the first embodiment; FIG. 13 is a diagram showing an example of a schematic configuration of an imaging device according to a second embodiment; FIG. 1 is a diagram showing an example of a schematic configuration of a position measuring device;

An exemplary embodiment of the present invention will be described in detail below with reference to the drawings.

First Embodiment
2 is a diagram showing a schematic configuration example of the imaging device according to the first embodiment. The imaging device 11 according to the first embodiment includes an illumination device 1, a half mirror 2, a plane mirror 3, a telecentric lens 4, and an imaging unit 5.

The imaging device 11 according to the first embodiment captures an image of a transparent body 6 such as glass.

The virtual reference plane 7 is a plane extending along the X-axis direction and the Y-axis direction. The perpendicular line of the virtual reference plane 7 is parallel to the Z-axis direction. The negative direction of the Z-axis direction may be, for example, the vertical direction, but the X-axis direction, the Y-axis direction, and the Z-axis direction are not limited to this example.

The imaging unit 5, telecentric lens 4, half mirror 2, and plane mirror 3 are arranged in this order in the Z-axis direction. The transparent body 6 is transported to a position between the half mirror 2 and the plane mirror 3 by a transport device (not shown). The illumination device 1 and the half mirror 2 are aligned in the X-axis direction.

The lighting device 1 includes a plurality of light sources 1A and a diffusion plate 1B. The light sources 1A may be, for example, LEDs (Light Emitting Diodes).

The light emitted from the lighting device 1 is generally parallel to the virtual reference plane 7, but is not strictly parallel because it is diffused by the diffusion plate 1B. Note that if the light emitted from the lighting device 1 were strictly parallel, it would not reach the imaging unit 5, so the light emitted from the lighting device 1 needs to be low-parallel light.

The half mirror 2 reflects the light emitted from the lighting device 1.

The telecentric lens 4 focuses the light that is reflected by the half mirror 2, further reflected by the plane mirror 3 or the transparent body 6, and then passes through the half mirror 2. The telecentric lens 4 guides only the light that is parallel to the optical axis of the telecentric lens 4 to the imaging unit 5.

The imaging unit 5 receives the light focused by the telecentric lens 4. As the imaging unit 5, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, etc. can be used.

The narrow angle β between the reflecting surface of the half mirror 2 and the virtual reference plane 7 is approximately 45 degrees. Approximately 45 degrees means that the design value is 45 degrees, but a range of 45±1 degrees is acceptable.

The optical axis of the telecentric lens 4 and the virtual reference plane 7 are approximately perpendicular. "Approximately perpendicular" means that the design value is 90 degrees, but a deviation of approximately 90±1 degrees is acceptable.

Here, the photographing device 11' according to the comparative example shown in FIG. 3 will be described. The photographing device 11' according to the comparative example shown in FIG. 3 uses a half mirror 2 in the same way as the photographing device 11 according to the first embodiment to reduce the required space behind the transparent body 6 as seen from the imaging unit 5. The photographing device 11' according to the comparative example shown in FIG. 3 differs from the photographing device 11 according to the first embodiment in that the light irradiated from the lighting device 1' is parallel light and the optical axis of the telecentric lens 4 is designed to be perpendicular to the plane mirror 3. However, in the photographing device 11' according to the comparative example shown in FIG. 3, if the optical axis of the telecentric lens 4 is not perpendicular to the plane mirror 3 due to an error in the arrangement of each component, or if the parallelism of the parallel light irradiated from the lighting device 1' is low, when the light reflected by the half mirror 2 toward the plane mirror 3 moves away from the transparent body 6 toward the plane mirror 3, the shadow of the transparent body 6 is photographed. As a result, the photographed image of the transparent body 6 is as shown in FIG. 4. The first portion P1' of the photographed image shown in FIG. 4 corresponds to the light LT1 reflected by the plane mirror 3. The second portion P2' of the captured image shown in FIG. 4 corresponds to the light LT2 reflected at the edge of the transparent body 6. The third portion P3' of the captured image shown in FIG. 4 corresponds to the light LT3 reflected at a surface parallel to the virtual reference plane 7 of the transparent body 6. The fourth portion P4' of the captured image shown in FIG. 4 corresponds to the shadow SD1 of the transparent body 6 reflected on the plane mirror 3. The boundary between the fourth portion P4' and the second portion P2' is the outer shape of the transparent body 6. However, since the fourth portion P4' corresponds to the shadow of the transparent body 6, the contrast between the fourth portion P4' and the second portion P2' is low. If the contrast between the fourth portion P4' and the second portion P2' is low, the boundary between the fourth portion P4' and the second portion P2' becomes unclear, and the outer shape of the transparent body 6 becomes unclear. In other words, in order to obtain a high-contrast image in which the outer shape of the transparent body 6 is clear, it is necessary to prevent the shadow of the transparent body 6 from being reflected in the captured image. In order to prevent the shadow of the transparent body 6 from appearing in the captured image, in the imaging device 11 according to the first embodiment, the reflection surface of the plane mirror 3 is inclined with respect to the virtual reference plane 7 so that the shadow of the transparent body 6 is hidden by the transparent body 6 when the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the direction perpendicular to the virtual reference plane 7, that is, so that the light reflected by the half mirror 2 and approaching the plane mirror 3 from the transparent body 6 is reflected by the plane mirror 3 and becomes parallel to the optical axis of the telecentric lens 4. Since the shadow of the transparent body 6 is hidden by the transparent body 6 when the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the direction perpendicular to the virtual reference plane 7, the contrast is high at the boundary between the part corresponding to the light reflected by the plane mirror 3 and the part corresponding to the light reflected by the edge part of the transparent body 6, and the boundary between the part corresponding to the light reflected by the plane mirror 3 and the part corresponding to the light reflected by the edge part of the transparent body 6 is clear, and an image in which the outer shape of the transparent body 6 is clear can be obtained. As described above, an error in the narrow angle β between the reflecting surface of the half mirror 2 and the virtual reference plane 7, and an error in the narrow angle between the optical axis of the telecentric lens 4 and the virtual reference plane 7 are allowed. This makes it possible to eliminate or simplify the position adjustment mechanism for the half mirror 2, etc., thereby reducing costs. Furthermore, by allowing the error, it is possible to reduce the effort required to assemble the imaging device 11 according to the first embodiment and the effort required to maintain the imaging device 11 according to the first embodiment.

When the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the direction perpendicular to the virtual reference plane 7, the shadow SD1 of the transparent body 6 is hidden by the transparent body 6, so the captured image of the transparent body 6 becomes as shown in Figure 5.

The first portion P1 of the captured image shown in FIG. 5 corresponds to the light LT1 reflected by the plane mirror 3. The second portion P2 of the captured image shown in FIG. 5 corresponds to the light LT2 reflected by the edge of the transparent body 6. The third portion P3 of the captured image shown in FIG. 5 corresponds to the light LT3 reflected by a surface parallel to the virtual reference plane 7 of the transparent body 6. The boundary between the first portion P1 and the second portion P2 of the captured image is the outline of the transparent body 6.

Unlike the imaging devices shown in Figures 1A to 1C, the imaging device 11 according to the first embodiment does not need to irradiate the transparent body 6 with highly parallel light, and therefore does not need a large space on the other side of the transparent body 6 as seen from the imaging unit 5. This allows for greater freedom in designing the equipment including the imaging device.

It is desirable that the narrow angle α between the reflecting surface of the plane mirror 3 and the virtual reference plane 7 is 0.5 degrees or more and 1.5 degrees or less. By setting the narrow angle α between the reflecting surface of the plane mirror 3 and the virtual reference plane 7 to 0.5 degrees or more and 1.5 degrees or less, the space occupation on the other side of the transparent body 6 as seen from the imaging unit 5 can be suppressed, and the size of the imaging device 11 according to the first embodiment can be suppressed. In addition, the plane mirror 3 is tilted so that it is further away from the transparent body 6 in the Z axis direction as it is further away from the transparent body 6 in the X axis direction. By tilting the plane mirror 3 so that it is further away from the transparent body 6 in the Z axis direction as it is further away from the transparent body 6 in the X axis direction, the shadow of the transparent body 6 can be hidden by the transparent body 6 when the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the perpendicular direction of the virtual reference plane 7. Therefore, the captured image shown in FIG. 5 can be obtained. Conversely, if the plane mirror 3 is tilted so that the farther it is from the transparent body 6 in the X-axis direction, the closer it is to the transparent body 6 in the Z-axis direction. When the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the direction perpendicular to the virtual reference plane 7, the shadow of the transparent body 6 will extend beyond the transparent body 6, and the captured image shown in FIG. 5 cannot be obtained, and only the captured image similar to the captured image shown in FIG. 4 can be obtained.

Furthermore, it is desirable that the distance L1 between the plane mirror 3 and the transparent body 6 is shorter than the distance L2 between the telecentric lens 4 and the transparent body 6. This allows for even greater freedom in designing the equipment, including the imaging device.

Figure 6 is a flowchart showing the procedure for photographing using the photographing device 11 according to the first embodiment.

First, a conveying device (not shown) conveys the transparent body 6 to a position between the half mirror 2 and the plane mirror 3 (step S10).

Next, the lighting device 1 emits light (step S20). Note that the process of step S20 may be started before step S10.

In step S30 following step S20, the telecentric lens 4 collects the light. Then, the imaging unit 5 receives the light collected by the telecentric lens 4 (step S40). When the processing of step S40 is completed, the image capture ends.

Second Embodiment
7 is a diagram showing a schematic configuration example of an imaging device according to the second embodiment. Descriptions of the same parts of the imaging device 12 according to the second embodiment as those of the imaging device 11 according to the first embodiment will be omitted as appropriate, and the following will describe the parts of the imaging device 12 according to the second embodiment that are different from the imaging device 11 according to the first embodiment.

The lighting device 1 includes multiple light sources 1A and a collimator lens 1C. The light emitted from the lighting device 1 is parallel to the virtual reference plane 7.

The reflecting surface of the plane mirror 3 is parallel to the virtual reference plane 7.

The reflective surface of the half mirror 2 is tilted in a direction such that the narrow angle it forms with the virtual reference plane 7 is 45 degrees, and the optical axis of the telecentric lens 4 is tilted in a direction perpendicular to the virtual reference plane 7, so that the shadow of the transparent body 6 is hidden by the transparent body 6 when the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the direction perpendicular to the virtual reference plane 7. Since the shadow of the transparent body 6 is hidden by the transparent body 6 when the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the direction perpendicular to the virtual reference plane 7, a high-contrast image can be obtained.

Unlike the imaging device shown in Figures 1A to 1C, the imaging device 12 according to the second embodiment does not need to irradiate the transparent body 6 with highly parallel light, and therefore does not need a large space on the other side of the transparent body 6 as seen from the imaging unit 5. This allows for greater freedom in designing the equipment including the imaging device.

The narrow angle β between the reflecting surface of the half mirror 2 and the virtual reference plane 7 is 43.5 degrees or more and 44.5 degrees or less, and the optical axis AX of the telecentric lens 4 is inclined by 0.5 degrees or more and 1.5 degrees or less with respect to the perpendicular direction of the virtual reference plane 7, that is, it is desirable that the narrow angle γ between the optical axis AX of the telecentric lens 4 and the perpendicular direction of the virtual reference plane 7 is 0.5 degrees or more and 1.5 degrees or less. This makes it possible to suppress the size of the imaging device 12 according to the second embodiment by suppressing the occupation of space on the other side of the transparent body 6 as viewed from the imaging unit 5, while making it possible to hide the shadow of the transparent body 6 when the plane mirror 3 and the transparent body 6 are viewed from the imaging unit 5 in the perpendicular direction of the virtual reference plane 7.

<Application Examples>
The imaging device 11 according to the first embodiment and the imaging device 12 according to the second embodiment can be applied to, for example, a position measuring device that measures the position of a transparent body 6. Fig. 8 is a diagram showing an example of the schematic configuration of the position measuring device.

The position measuring device 13 includes the imaging device 11 according to the first embodiment and an image processing unit 14. The image processing unit 14 processes the captured image data output from the imaging device 11 according to the first embodiment to detect coordinates indicating the outline of the transparent body 6 in the captured image, and measures the position of the transparent body 6 based on the detection result.

Note that, although the imaging device 11 according to the first embodiment is used in the position measurement device 13, the imaging device 12 according to the second embodiment may be used instead of the imaging device 11 according to the first embodiment.

<Points to note>
The above-described embodiments should be considered in all respects as illustrative and not restrictive, and the technical scope of the present invention is indicated by the claims, not by the description of the above-described embodiments, and should be understood to include all modifications that fall within the meaning and scope of the claims.

REFERENCE SIGNS LIST 1 Illumination device 1A Light source 1B Diffuser 1C Collimator lens 2 Half mirror 3 Plane mirror 4 Telecentric lens 5 Imaging section 6 Transparent body 7 Virtual reference plane 11 Imaging device according to first embodiment 12 Imaging device according to second embodiment 13 Position measuring device 14 Image processing section

Claims (7)

A lighting device;
a half mirror that reflects light emitted from the lighting device;
A plane mirror;
a telecentric lens that collects light that is reflected by the half mirror, further reflected by the plane mirror or the transparent body, and then passes through the half mirror;
an imaging unit that receives light collected by the telecentric lens;
Equipped with
a narrow angle between a reflecting surface of the half mirror and a virtual reference plane is approximately 45 degrees, and an optical axis of the telecentric lens is approximately perpendicular to the virtual reference plane;
An imaging device in which the reflective surface of the plane mirror is inclined with respect to the virtual reference plane so that the shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in a direction perpendicular to the virtual reference plane. The imaging device according to claim 1, wherein the narrow angle between the reflecting surface of the plane mirror and the virtual reference plane is 0.5 degrees or more and 1.5 degrees or less. An illumination device that irradiates light parallel to a virtual reference plane;
a half mirror that reflects light emitted from the lighting device;
A plane mirror;
a telecentric lens that collects light that is reflected by the half mirror, further reflected by the plane mirror or the transparent body, and then passes through the half mirror;
an imaging unit that receives light collected by the telecentric lens;
Equipped with
a reflecting surface of the plane mirror is parallel to the virtual reference plane;
an imaging device in which the reflective surface of the half mirror is inclined with respect to a narrow angle of 45 degrees with respect to the virtual reference plane, and the optical axis of the telecentric lens is inclined with respect to the perpendicular direction to the virtual reference plane, so that the shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in the perpendicular direction to the virtual reference plane. The imaging device according to claim 3, wherein the narrow angle between the reflecting surface of the half mirror and the virtual reference plane is 43.5 degrees or more and 44.5 degrees or less, and the optical axis of the telecentric lens is inclined by 0.5 degrees or more and 1.5 degrees or less with respect to the perpendicular direction of the virtual reference plane. The imaging device according to any one of claims 1 to 4, wherein the distance between the plane mirror and the transparent body is shorter than the distance between the telecentric lens and the transparent body. a focusing step of reflecting light emitted from an illumination device by a half mirror, further reflecting the light by a plane mirror or a transparent body, and then focusing the light that has passed through the half mirror by a telecentric lens;
a light receiving step of receiving the light collected by the telecentric lens with an imaging unit;
Equipped with
a narrow angle between a reflecting surface of the half mirror and a virtual reference plane is approximately 45 degrees, and an optical axis of the telecentric lens is approximately perpendicular to the virtual reference plane;
A photographing method in which a reflective surface of the plane mirror is tilted with respect to the virtual reference plane so that a shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in a direction perpendicular to the virtual reference plane. a focusing step of reflecting light parallel to a virtual reference plane emitted from an illumination device by a half mirror, further reflecting the light by a plane mirror or a transparent body, and then focusing the light that has passed through the half mirror by a telecentric lens;
a light receiving step of receiving the light collected by the telecentric lens with an imaging unit;
Equipped with
a reflecting surface of the plane mirror is parallel to the virtual reference plane;
a reflective surface of the half mirror is tilted in a direction such that a narrow angle between the half mirror and a virtual reference plane is 45 degrees, and an optical axis of the telecentric lens is tilted in a direction perpendicular to the virtual reference plane, so that a shadow of the transparent body is hidden by the transparent body when the plane mirror and the transparent body are viewed from the imaging unit in a direction perpendicular to the virtual reference plane.