Coaxial epi-illumination device for image processing inspection

Abstract

To provide a coaxial incident illumination device for image processing inspection that can apply light with more uniform illuminance.SOLUTION: A coaxial incident illumination device 1 for image processing inspection comprises a single light source 3 having an optical axis in a front-rear direction D1, a half mirror 6 inclined with respect to the front-rear direction D1, a first lens 4 for reducing the light distribution angle of light emitted from the single light source 3, and a second lens 5 for making light from the first lens 4 incident on the half mirror 6. The half mirror 6 reflects light from the second lens 5 in a downward direction D2 to apply it to an object B, and transmits reflected light from the object B. The single light source 3, the first lens 4, the second lens 5, and the half mirror 6 are arranged in this order along the front-rear direction D1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coaxial epi-illumination device for image processing inspection, which is used to illuminate an object in image processing inspection. [Background technology]

[0002] Image processing inspection using images captured by a CCD camera or the like has been conventionally performed on production lines to inspect the quality of industrial products such as semiconductors and the printing on product packages. A coaxial epi-illuminator has been proposed as one of the illumination devices used in such image processing inspections. A coaxial epi-illuminator is configured such that light emitted from a light source is diffused by a diffuser plate, reflected by a half mirror, and irradiated onto an object on an illumination surface, and the reflected light from the object reaches a CCD camera or the like via the half mirror. The light source is composed of multiple LEDs arranged in a plane (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-140032 Summary of the Invention [Problem to be solved by the invention]

[0004] An example of a conventional coaxial epi-illumination device is shown in Fig. 3. Referring to Fig. 3(a), light reflected by half mirror 106 is emitted through irradiation opening (irradiation hole) 121a provided in housing 102. In the conventional coaxial epi-illumination device, as shown in Fig. 3(b), not only does the illuminance of the light vary in the irradiation area on irradiation surface T, but there is also a discrepancy between the center of irradiation opening 121a and the peak illuminance position of the light in the irradiation area. This is because a portion of the light diffused by diffuser plate 8 reaches irradiation surface T directly without being reflected by half mirror 106, and the peak illuminance position is farther from light source 103 than the center of irradiation opening 121a.

[0005] Furthermore, in conventional coaxial epi-illumination devices, it is not possible to adjust the illumination area on the illumination surface in accordance with the work distance or work size (the dimensions of the target object).

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a coaxial epi-illumination device for image processing inspection that can irradiate light with a more uniform illuminance.

[0007] Another object of the present invention is to provide a coaxial epi-illumination device for image processing inspection that can set the illumination area according to the work distance and work size. [Means for solving the problem]

[0008] The coaxial epi-illumination device for image processing inspection according to the present invention is used in image processing inspection in which an object is imaged and inspected, and comprises a single light source having an optical axis in a first direction, a half mirror inclined with respect to the first direction, a first lens that reduces the distribution angle of light emitted from the single light source, and a second lens that causes the light from the first lens to be incident on the half mirror, wherein the half mirror reflects the light from the second lens in a second direction perpendicular to the first direction to irradiate the object and transmits the reflected light from the object, and the single light source, the first lens, the second lens, and the half mirror are arranged in this order along the first direction.

[0009] Preferably, the second lens converts the light from the first lens into parallel light or convergent light and makes it incident on the half mirror. [Effects of the Invention]

[0010] According to the coaxial epi-illumination device for image processing inspection of 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, and the light emitted from the single light source has its light distribution angle reduced by the first lens and enters the half mirror via the second lens, and the light reflected by the half mirror illuminates the object. Therefore, the light from the single light source does not illuminate the object on the illumination surface without passing through the half mirror, and the object can be illuminated with a more uniform amount of light. Furthermore, since the device includes a single light source, the number of parts can be reduced compared to a coaxial epi-illumination device including multiple light sources arranged in a planar manner.

[0011] Furthermore, the second lens converts the light from the first lens into parallel light and makes it incident on the half mirror, so that 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.

[0012] Alternatively, the second lens can convert the light from the first lens into focused light and make it incident on the half mirror, so that the light reflected by the half mirror and irradiated onto the target also becomes focused light. This allows for efficient illumination of a narrower illumination area, making it suitable for pinpoint illumination of the target. Furthermore, the degree of convergence of the focused light can be appropriately set 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. [Brief explanation of the drawings]

[0013] [Figure 1] 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. [Figure 2]FIG. 10 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 second embodiment of the present invention. [Figure 3] FIG. 1(a) is a schematic diagram showing the overall configuration of an image processing inspection system equipped with a conventional illumination device, and FIG. 1(b) is a graph showing the illuminance distribution on the illumination surface in a conventional coaxial epi-illumination device. DETAILED DESCRIPTION OF THE INVENTION

[0014] [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.

[0015] The housing 2 has a rectangular parallelepiped shape and includes a bottom wall 21, a top wall 22, a front wall 23, a rear wall 24, and a pair of side walls (not shown). An irradiation hole 21a is opened in the bottom wall 21, and a transmission window 22a is provided in the top wall 22, and a transmission member 22b is fitted into the transmission window 22a. 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.

[0016] 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 has passed through the first lens 4 into parallel light that is parallel to the optical axis of the light source 3 and emits the parallel light 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 the second lens 5 coincide and extend in the front-to-rear direction D1.

[0017] The half mirror 6 is a mirror that reflects half of the incident light and transmits the other half, and is arranged at an angle of 45 degrees with respect to the front-to-back direction D1 (diagonally facing upward and rearward in the example of FIG. 1), and reflects the light from the second lens 5 downward (second direction) D2 toward the object B (irradiation surface T), and transmits the reflected light from the object B upward toward the imaging device C. The imaging device C has an optical axis in the vertical direction, is arranged opposite the object B via the half mirror 6, and captures the reflected light from the object B.

[0018] 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 and is reflected by the half mirror 6 downward toward D2 along the optical axis of the imaging device C. The light reflected downward toward D2 in this manner 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.

[0019] 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. Therefore, it is possible to uniformly illuminate the illumination area on the illumination surface T. 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, and light loss can be suppressed.

[0020] Furthermore, since 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.

[0021] In this embodiment, a single light source is used, so the number of parts can be reduced compared to a surface light source in which a plurality of light sources are arranged in a plane.

[0022] In this embodiment, a wide object such as a label or packaging part is suitable as the object B. 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.

[0023] [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, but the distance MD from the first lens 4 to the second lens 5 is set wider than that 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.

[0024] In this embodiment as well, the light emitted from the light source 3 is converted into convergent 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.

[0025] Furthermore, since the convergent light from the second lens 5 is reflected by the half mirror 6, the illumination light reflected by the half mirror 6 and illuminating the object B becomes convergent light. Therefore, compared to the first embodiment described above, a narrower illumination area can be illuminated efficiently, which is suitable for pinpoint illumination of the object B, and small items such as electronic components are suitable as the object B in this embodiment.

[0026] Here, the degree of convergence of light 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 of convergence of light 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).

[0027] The coaxial epi-illumination device for image processing inspection according to the embodiment of the present invention has been described above with reference to the accompanying drawings. However, the present invention is not limited to such an embodiment, and various modifications and alterations are possible without departing from the scope of the present invention.

[0028] For example, in the first and second embodiments, only the distance MD from the first lens 4 to the second lens 5 is different, but in addition to this, the distance OD from the single light source 3 to the first lens 4 may also be different. [Explanation of symbols]

[0029] 1, 1A Coaxial epi-illuminator 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

1. 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.

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 a converged light and making it 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.