JP7807619B2 - Coaxial epi-illumination device for image processing inspection - Google Patents

Description

The present invention relates to a coaxial epi-illumination device for image processing inspection, which is used to illuminate an object during image processing inspection.

Image processing inspections using images captured by CCD cameras and other devices have traditionally been performed on production lines to inspect the quality of industrial products such as semiconductors and the printing on product packaging. One type of lighting device used in such image processing inspections is the coaxial epi-illumination device. Coaxial epi-illumination devices are configured so that light emitted from a light source is diffused by a diffuser plate, reflected by a half mirror, and irradiated onto an object on the illumination surface. The light reflected from the object then travels via the half mirror to a CCD camera or other device. The light source is composed of multiple LEDs arranged in a planar pattern (see, for example, Patent Document 1).

JP 2013-140032 A

Figure 3 shows an example of a conventional coaxial epi-illumination device. Referring to Figure 3(a), light reflected by the half mirror 106 is emitted through an irradiation opening (irradiation hole) 121a provided in the housing 102. However, in conventional coaxial epi-illumination devices, as shown in Figure 3(b), not only does the illuminance of the light vary in the irradiation area on the irradiation surface T, but there is also a discrepancy between the center of the irradiation opening 121a and the peak illuminance position of the light in the irradiation area. This is because some of the light diffused by the diffuser 8 reaches the irradiation surface T directly without being reflected by the half mirror 106, and the peak illuminance position is farther from the light source 103 than the center of the irradiation opening 121a.

Furthermore, with conventional coaxial epi-illumination devices, it was not possible to adjust the illumination area on the illumination surface according to the work distance or work size (object dimensions).

The objective of the present invention is to provide a coaxial epi-illumination device for image processing inspection that can emit light with more uniform illuminance.

Another object of the present invention is to provide a coaxial epi-illumination device for image processing inspection that allows the illumination area to be set according to the work distance and work size.

The coaxial epi-illumination device for image processing inspection according to the present invention is used in image processing inspections in which an object is imaged and inspected. It comprises a single light source having an optical axis in a first direction, a half mirror tilted with respect to the first direction, a first lens that reduces the light distribution angle of the light emitted from the single light source, and a second lens that causes the light from the first lens to enter the half mirror. The half mirror reflects the light from the second lens in a second direction perpendicular to the first direction to illuminate the object and transmits the light reflected from the object. The single light source, first lens, second lens, and half mirror are arranged in this order along the first direction.

It is also preferable that the second lens converts the light from the first lens into parallel or convergent light and directs it into the half mirror.

In the coaxial epi-illumination device for image processing inspection according to the present invention, a single light source, a first lens, a second lens, and a half mirror are arranged in this order along a first direction. The light emitted from the single light source has its light distribution angle reduced by the first lens, and is incident on the half mirror via the second lens. The light reflected by the half mirror then illuminates the object. Therefore, light from the single light source does not illuminate the object on the illumination surface without passing through the half mirror, allowing the object to be illuminated with a more uniform amount of light. Furthermore, because it has a single light source, the number of parts can be reduced compared to coaxial epi-illumination devices with multiple light sources arranged in a plane.

In addition, the second lens converts the light from the first lens into parallel light and makes it incident on the half mirror, so the light reflected by the half mirror and irradiated onto the object also becomes parallel light. Therefore, even if the working distance varies, the object can be irradiated with a uniform amount of light.

Alternatively, the second lens converts the light from the first lens into focused light and directs it into the half mirror, so that the light reflected by the half mirror and illuminating the object also becomes focused light. This allows for efficient illumination of a narrower illumination area, making it ideal for pinpoint illumination of an object. Furthermore, the degree of convergence of the focused light can be set appropriately according to the work distance and work size, and can be easily set by adjusting the distance from the first lens to the second lens.

1 is a schematic diagram showing the overall configuration of an image processing inspection system equipped with a coaxial epi-illumination device for image processing inspection according to a first embodiment of the present invention; FIG. 10 is a schematic diagram showing the overall configuration of an image processing inspection system including a coaxial epi-illumination device for image processing inspection according to a second embodiment of the present invention. 1A is a schematic diagram showing the overall configuration of an image processing inspection system equipped with a conventional illumination device, and FIG. 1B is a graph showing the illuminance distribution on an illumination surface in a conventional coaxial epi-illumination device.

[First embodiment]
An image processing inspection system including a coaxial epi-illumination device for image processing inspection according to a first embodiment of the present invention will be described below with reference to the accompanying drawings. The image processing inspection system S shown in Fig. 1 includes a coaxial epi-illumination device for image processing inspection (hereinafter referred to as the "illumination device") 1 for irradiating light onto an object B on an irradiation surface T, and an imaging device C for imaging the object B. The illumination device 1 includes a housing 2, and a light source 3, a first lens 4, a second lens 5, and a half mirror 6 housed and held in the housing 2. The light source 3 has an optical axis in a front-to-rear direction (first direction) D1, and the light source 3, the first lens 4, the second lens 5, and the half mirror 6 are arranged in this order along the front-to-rear direction D1 at intervals from one another.

The housing 2 is rectangular and has a bottom wall 21, a top wall 22, a front wall 23, a rear wall 24, and a pair of side walls (not shown). The bottom wall 21 has an irradiation hole 21a, and the top wall 22 has a transmission window 22a into which a transmission member 22b is fitted. The light source 3 is a single light source having only one LED element 31, and is arranged on the inner surface of the rear wall 24 of the housing 2 so that the optical axis of the LED element 31 extends forward.

The first lens 4 functions as a light distribution control lens that reduces the light distribution angle of the light emitted from the light source 3. The second lens 5 converts the light that passes through the first lens 4 into parallel light parallel to the optical axis of the light source 3 and emits it toward the half mirror 6; here, a Fresnel lens is used as the second lens 5. The optical axes of the first lens 4 and second lens 5 coincide and extend in the front-to-rear direction D1.

The half mirror 6 is a mirror that reflects half of the light that enters it and transmits the other half. It is tilted at a 45-degree angle relative to the front-to-back direction D1 (diagonally tilted upward and rearward in the example of Figure 1), and reflects light from the second lens 5 downward (in the second direction) D2 toward the object B (irradiation surface T), while transmitting the light reflected from the object B upward toward the imaging device C. The imaging device C has an optical axis in the vertical direction, is positioned opposite the object B via the half mirror 6, and captures the light reflected from the object B.

In this configuration, the light emitted from the light source 3 has its light distribution angle reduced by the first lens 4, and the light distribution angle is further controlled by the second lens 5 to form parallel light. The parallel light from the second lens 5 is incident on the half mirror 6, which reflects it downward D2 along the optical axis of the imaging device C. The light reflected downward D2 is emitted through the irradiation hole 21a and illuminates the object B. The light reflected by the object B then enters the housing 2 through the irradiation hole 21a, passes through the half mirror 6 and the transmission window 22a, reaches the imaging device C, and is imaged by the imaging device C.

In this way, the light emitted from the light source 3 is converted by the second lens 5 into parallel light parallel to the optical axis of the light source 3, so the light from the second lens 5 does not directly illuminate the object B. This allows the illumination area on the illumination surface T to be uniformly illuminated. Furthermore, because the luminous intensity distribution angle of the light emitted from the light source 3 is reduced by the first lens 4, the light from the light source 3 can be efficiently incident on the second lens 5, minimizing light loss.

Furthermore, because the parallel light from the second lens 5 is reflected by the half mirror 6, the light reflected by the half mirror 6 and irradiating the object B becomes parallel light. Therefore, even if the working distance WD (i.e., the distance from the irradiation hole 21a to the object B) varies, the object B can be irradiated with a uniform amount of light.

In this embodiment, a single light source is used, which reduces the number of parts compared to a surface light source in which multiple light sources are arranged in a plane.

In this embodiment, the object B is preferably a wide object such as a label or packaging part. Regarding the distance OD from the light source 3 to the first lens 4 and the distance MD from the first lens 4 to the second lens 5, the distance OD is set first, and then the distance MD is set.

Second Embodiment
Next, an illumination device (coaxial epi-illumination device for image processing inspection) according to a second embodiment of the present invention will be described with reference to Fig. 2. The illumination device 1A according to this embodiment is substantially the same as the illumination device 1 shown in Fig. 1, except that the distance MD from the first lens 4 to the second lens 5 is set wider than that shown in Fig. 1, so that light incident on the second lens 5 is converted into focused light. The focused light emitted from the second lens 5 is then reflected downward by the half mirror 6 and illuminates the object B.

In this embodiment, too, the light emitted from the light source 3 is converted into focused light by the second lens 5 and enters the half mirror 6, so the light from the second lens 5 does not directly illuminate the object B. Therefore, the illumination area on the illumination surface T can be uniformly illuminated.

In addition, because the focused light from the second lens 5 is reflected by the half mirror 6, the light reflected by the half mirror 6 and irradiating the object B becomes focused light. Therefore, compared to the first embodiment described above, a narrower irradiation area can be efficiently irradiated, making it suitable for pinpoint illumination of the object B. In this embodiment, the object B is preferably a small item such as an electronic component.

The degree to which light is focused by the second lens 5 can be set appropriately according to the work distance and the size of the irradiation area (in other words, the dimensions of the object B (work size)), and the degree to which light is focused by the second lens 5 can be easily set by adjusting the distance MD from the first lens 4 to the second lens 5 (i.e., the focal length of the combined lens consisting of the first and second lenses 4 and 5).

The above describes a coaxial epi-illumination device for image processing inspection according to an embodiment of the present invention with reference to the accompanying drawings. However, the present invention is not limited to such an embodiment, and various modifications and variations are possible without departing from the scope of the present invention.

For example, in the first and second embodiments described above, only the distance MD from the first lens 4 to the second lens 5 is different, but in addition, the distance OD from the single light source 3 to the first lens 4 may also be different.

1, 1A Coaxial epi-illumination device for image processing inspection 3 Single light source 4 First lens 5 Second lens 6 Half mirror B Object C Imaging device S Image processing inspection system

Claims (2)

A coaxial epi-illumination device for image processing inspection used in image processing inspection for imaging and inspecting an object,
a single light source having only one LED element having an optical axis in a first direction;
a half mirror tilted with respect to the first direction;
a first lens that reduces the light distribution angle of the light emitted from the single light source;
a second lens for causing the light from the first lens to be incident on the half mirror;
a housing that houses and holds the single light source, the half mirror, the first lens, and the second lens,
the half mirror reflects the light from the second lens in a second direction perpendicular to the first direction to irradiate the light onto an object, and transmits the light reflected from the object;
the housing has a first wall and a second wall facing each other in the second direction, the first wall is provided with an irradiation hole through which reflected light reflected by the half mirror passes, and the second wall is provided with a transmission window through which the reflected light passes;
the single light source, the first lens, the second lens, and the half mirror are arranged in this order along the first direction,
the second lens is a Fresnel lens attached to the first and second walls, converting the light from the first lens into parallel light and causing the parallel light to be incident on the half mirror;
the illumination light irradiated onto the object is parallel light,
does not have any lenses other than the first lens and the second lens,
A coaxial epi-illumination device for image processing inspection characterized by not having a diffusion plate. A coaxial epi-illumination device for image processing inspection used in image processing inspection for imaging and inspecting an object,
a single light source having only one LED element having an optical axis in a first direction;
a half mirror tilted with respect to the first direction;
a first lens that reduces the light distribution angle of the light emitted from the single light source;
a second lens for causing the light from the first lens to be incident on the half mirror;
a housing that houses and holds the single light source, the half mirror, the first lens, and the second lens,
the half mirror reflects the light from the second lens in a second direction perpendicular to the first direction to irradiate the light onto an object, and transmits the light reflected from the object;
the housing has a first wall and a second wall facing each other in the second direction , the first wall is provided with an irradiation hole through which reflected light reflected by the half mirror passes, and the second wall is provided with a transmission window through which the reflected light passes;
the single light source, the first lens, the second lens, and the half mirror are arranged in this order along the first direction,
the second lens is a Fresnel lens attached to the first and second walls, converting the light from the first lens into focused light and causing it to be incident on the half mirror;
The focused light incident on the half mirror is reflected by the half mirror and irradiated onto the object,
does not have any lenses other than the first lens and the second lens,
A coaxial epi-illumination device for image processing inspection characterized by not having a diffusion plate.