Imaging device and inspection device

Abstract

This invention provides a novel imaging device capable of appropriately acquiring fluorescence and reflected light images of an object. [Solution] The imaging device 2 comprises a stage 21 for holding an object, a first emission unit 3 for emitting first emission light which is ultraviolet light, a second emission unit 4 for emitting second emission light which is light in a different wavelength range than ultraviolet light, a cross dichroic prism 5 which is a rectangular prism having first to fourth sides 51 to 54, and which emits first emission light incident on the first side 51 from the third side 53 to guide it to the imaging area 90 on the object, and emits second emission light incident on the second side 52 from the third side 53 to guide it to the imaging area 90, and an imaging unit 7 which receives fluorescence generated in the imaging area 90 when the first emission light is irradiated onto the imaging area 90, and receives reflected light of the second emission light in the imaging area 90 when the second emission light is irradiated onto the imaging area 90.

Description

Technical Field

[0001] The present invention relates to an imaging device and an inspection device.

Background Art

[0002] Conventionally, an inspection device that acquires images of various objects and inspects the objects has been used. For example, in the inspection system of Patent Document 1, inspection light is irradiated onto an inspection object from the periphery of the inspection object by coaxial illumination and dome illumination, and the inspection light reflected in the normal direction of the inspection object is received by an area camera to capture a color image. Then, a defect inspection of the inspection object is performed based on the color image. In addition, in Patent Document 2, a position measuring device such as an alignment mark is disclosed. In this device, using one cross-dichroic prism, R, G, and B lights are synthesized on one optical axis and irradiated onto a test object. Also, using another cross-dichroic prism, the light from the test object is separated into R, G, and B lights and imaged on a plurality of CCDs respectively.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the increasing resolution of patterns drawn on printed circuit boards, defects known as dark shorts can occur. A dark short defect is a short circuit where a thin layer of conductive material remains in an area that is supposed to be free of conductive material (background area), causing electrical conductivity between conductive parts. When acquiring a reflected light image by illuminating a printed circuit board with illumination light and receiving the reflected light from the conductive parts with an imaging unit, it is difficult to distinguish between normal background areas and dark short defects using the reflected light image because the reflected light is not directed to the imaging unit in either case. Therefore, it is conceivable to irradiate the printed circuit board with ultraviolet (UV) light and acquire a fluorescence image by receiving the excitation emission (fluorescence) in the background area with an imaging unit, and use this to detect dark short defects. Accordingly, there is a need for an imaging device that can appropriately acquire both fluorescence images and reflected light images.

[0005] This invention has been made in view of the above problems, and aims to provide a novel imaging device capable of appropriately acquiring fluorescence images and reflected light images of an object. [Means for solving the problem]

[0006] One aspect of the present invention is an imaging device for imaging an object, comprising: a stage for holding the object; a first emission unit for emitting first emission light which is ultraviolet light; a second emission unit for emitting second emission light which is light in a wavelength range different from ultraviolet light; a cross dichroic prism which is a rectangular prism having first to fourth sides, and which emits the first emission light incident on the first side from the third side to guide it to an imaging area on the object, and emits the second emission light incident on the second side from the third side to guide it to the imaging area; and an imaging unit which receives fluorescence generated in the imaging area when the first emission light is irradiated onto the imaging area, and receives reflected light of the second emission light in the imaging area when the second emission light is irradiated onto the imaging area.

[0007] Aspect 2 of the present invention is an imaging apparatus according to aspect 1, wherein the cross dichroic prism has a first mirror film and a second mirror film that intersect each other, the first mirror film reflects the first emitted light and transmits the second emitted light, the second mirror film transmits the first emitted light and reflects and transmits the second emitted light and the fluorescence, light from the imaging area is incident on the third side surface of the cross dichroic prism, a portion of the light is emitted from the fourth side surface of the cross dichroic prism and guided to the imaging unit.

[0008] A third aspect of the present invention is an imaging apparatus according to the second aspect, wherein the first side and the second side of the cross dichroic prism face each other, and the third side and the fourth side face each other.

[0009] Aspect 4 of the present invention is an imaging apparatus according to Aspect 1 (which may be any one of Aspects 1 to 3), wherein the imaging unit has a line sensor as an image sensor, and the cross dichroic prism is elongated in the direction along the first to fourth side surfaces.

[0010] Aspect 5 of the present invention is an imaging apparatus according to aspect 1 (which may be any one of aspects 1 to 4), wherein the light source of the first emission unit is a laser diode.

[0011] Aspect 6 of the present invention is an imaging apparatus according to Aspect 1 (which may be any one of Aspects 1 to 5), further comprising a dome-shaped illumination unit which is arranged on the optical axis between the third side surface of the cross dichroic prism and the imaging area, illuminates the imaging area with illumination light from a dome-shaped surface covering the imaging area, and has a light-transmitting portion provided at a position on the surface intersecting the optical axis.

[0012] Embodiment 7 of the present invention is an imaging device according to Embodiment 1 (which may be any one of Embodiments 1 to 6), wherein the object is a printed circuit board.

[0013] Aspect 8 of the present invention is an inspection apparatus comprising an imaging device according to any one of aspects 1 to 7, and an inspection unit for inspecting an image acquired by the imaging device. [Effects of the Invention]

[0014] According to the present invention, a novel imaging device capable of appropriately acquiring fluorescence and reflected light images of an object can be provided. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram showing the configuration of the inspection device. [Figure 2] This is a magnified view of an X-prism. [Figure 3] This is a cross-sectional view of a printed circuit board. [Figure 4] This figure shows the amount of ultraviolet light irradiated and the amount of fluorescence when using an LED. [Figure 5] This figure shows the amount of ultraviolet light irradiated and the amount of fluorescence when using a laser diode. [Modes for carrying out the invention]

[0016] Figure 1 shows the configuration of an inspection device 1 according to one embodiment of the present invention. The inspection device 1 in Figure 1 is an optical visual inspection device for inspecting the appearance of a printed circuit board 9. The inspection device 1 may be a device for inspecting substrates other than the printed circuit board 9, or a device for inspecting objects other than substrates. In the following description, the vertical direction in Figure 1 will be simply referred to as the "vertical direction," but the vertical direction is not limited to the direction of gravity.

[0017] The inspection device 1 includes an imaging device 2 and a computer 10. The computer 10 has a CPU or the like, and realizes an inspection unit 11 and a control unit (not shown) by executing a predetermined program. The inspection unit 11 inspects the image acquired by the imaging device 2. That is, using the said image, defects on the printed circuit board 9 are detected. The control unit is responsible for the overall control of the inspection device 1. All or part of the inspection unit 11 and the control unit may be realized by a dedicated electric circuit.

[0018] The imaging device 2 includes a control unit, a stage 21, a stage moving mechanism 22, a first emission unit 3, a second emission unit 4, a cross dichroic prism 5 (hereinafter simply referred to as "X prism 5"), a dome-shaped illumination unit 6, and an imaging unit 7. In the example of FIG. 1, the control unit of the inspection device 1 also serves as the control unit of the imaging device 2. The stage 21 holds the printed circuit board 9 which is the object to be imaged by the imaging device 2. In the example of FIG. 1, the printed circuit board 9 is supported and held from below by the stage 21. The printed circuit board 9 may be held on the stage 21 by suction adsorption or the like. The stage moving mechanism 22 has a motor, a ball screw, etc., and moves the stage 21. The moving directions of the stage 21 by the stage moving mechanism 22 are, for example, two directions (two directions perpendicular to the vertical direction in FIG. 1) along the main surface of the printed circuit board 9 and perpendicular to each other. The stage moving mechanism 22 may be a mechanism having a linear motor or the like.

[0019] Above the stage 21, the X prism 5 is arranged. The X prism 5 is typically formed by bonding four right triangular prisms together and has the outer shape of a quadrangular prism (in the example of FIG. 1, a regular quadrangular prism). The interfaces of the four prisms intersect in an X shape. In other words, in the X prism 5, two surfaces intersecting in an X shape are provided. Dielectric multilayer films, mirror films 56, 57, are formed on the two surfaces. The mirror film 56 on one surface (hereinafter referred to as "first mirror film 56") is a dichroic mirror that reflects ultraviolet light and transmits visible light. In an example of the first mirror film 56, the reflectivity of light with a wavelength of 360 - 409 nm at an incident angle of 45° is greater than 98%.

[0020] The mirror film 57 on the other side (hereinafter referred to as the "second mirror film 57") is a half mirror that transmits ultraviolet light and reflects and transmits visible light (it can also be regarded as a dichroic mirror). In an example of the second mirror film 57, the reflectance of light with a wavelength of 360 to 409 nm at an incident angle of 45° is less than 0.2%, and the reflectance of light with a wavelength of 410 to 860 nm is 50%. In the present embodiment, it is assumed that the light with a wavelength of 360 to 409 nm is included in ultraviolet light, and the light with a wavelength of 410 to 860 nm is included in visible light.

[0021] The outer shape of the X prism 5 has four side surfaces and two end surfaces. The four side surfaces include a first side surface 51, a second side surface 52, a third side surface 53, and a fourth side surface 54. In FIG. 1, the first side surface 51 faces the left side, and the second side surface 52 faces the right side. The third side surface 53 faces the lower side, and the fourth side surface 54 faces the upper side. Thus, the first side surface 51 and the second side surface 52 face each other, and the third side surface 53 and the fourth side surface 54 face each other. A general antireflection film (AR coat) is formed on the first to fourth side surfaces 51 to 54. In an example of the antireflection film, the reflectance of light with a wavelength of 360 to 860 nm at an incident angle of 0° is less than 0.2%. The outer shape of the X prism 5 is long in the direction along the first to fourth side surfaces 51 to 54 (the direction between the two end surfaces, hereinafter referred to as the "prism longitudinal direction"). The prism longitudinal direction in FIG. 1 is a direction perpendicular to the paper surface. When viewed along the prism longitudinal direction, the first mirror film 56 and the second mirror film 57 are respectively arranged on two diagonals of the quadrilateral forming the outer shape of the X prism 5 and intersect at an angle of 90°. The angle formed by the first mirror film 56 and each of the first to fourth side surfaces 51 to 54 is 45°. Similarly, the angle formed by the second mirror film 57 and each of the first to fourth side surfaces 5'1 to 54 is 45°.

[0022] The first emission unit 3 is positioned opposite the first side surface 51 of the X prism 5 and comprises a light source unit 31 and an optical system 32. The light source unit 31 emits first emission light, which is ultraviolet light. A preferred light source unit 31 includes one or more laser diodes (also called LDs or semiconductor lasers). As will be described later, laser diodes have a narrower wavelength range compared to LEDs, etc. The wavelength of the first emission light is, for example, 365 nm or 405 nm. The optical system 32 shapes the first emission light and guides it to the X prism 5. Specifically, the first emission light emitted from the light source unit 31 is shaped by the optical system 32 so that its cross-sectional area extends in the longitudinal direction of the prism, and then incident on the first side surface 51 of the X prism 5. The optical axis of the optical system 32 is approximately perpendicular to the first side surface 51.

[0023] The second emission unit 4 is positioned opposite the second side surface 52 of the X prism 5 and comprises a light source unit 41 and an optical system 42. The light source unit 41 emits, for example, second emission light which is visible light. The second emission light may be light other than ultraviolet light and visible light. In this embodiment, the light source unit 41 includes a plurality of LEDs (light-emitting diodes). The plurality of LEDs are arranged in the longitudinal direction of the prism. The wavelength of the second emission light is, for example, in the range of 410 to 860 nm. The optical system 42 guides the second emission light to the X prism 5. In the example of Figure 1, the optical system 42 has a diffuser plate and a linear Fresnel lens, and the second emission light emitted from the light source unit 41 is homogenized and shaped so that its light beam cross-section extends in the longitudinal direction of the prism before being incident on the second side surface 52 of the X prism 5. The optical axis of the optical system 42 is substantially perpendicular to the second side surface 52.

[0024] As described later, the first emitted light incident on the X-prism 5 from the first emitted section 3, and the second emitted light incident on the X-prism 5 from the second emitted section 4, are emitted from the third side surface 53 of the X-prism 5 and illuminate a region 90 (hereinafter referred to as the "imaging region 90") extending in the longitudinal direction of the prism on the upper surface of the printed circuit board 9. The imaging region 90 is the region where imaging is performed by the imaging unit 7. In the first emitted section 3, the first emitted light is guided to the imaging region 90 along the optical axis that goes from the light source 31 to the printed circuit board 9 via the optical system 32 and the X-prism 5. In the second emitted section 4, the second emitted light is guided to the imaging region 90 along the optical axis that goes from the light source 41 to the printed circuit board 9 via the optical system 42 and the X-prism 5. Between the third side surface 53 of the X-prism 5 and the printed circuit board 9, the optical axis of the first emitted section 3 and the optical axis of the second emitted section 4 coincide. In Figure 1, the optical axis between the third side surface 53 of the X prism 5 and the printed circuit board 9 is denoted by the symbol J1. The optical axis J1 is approximately perpendicular to the third side surface 53.

[0025] The dome-shaped illumination unit 6 is positioned on the optical axis J1 between the third side surface 53 of the X-prism 5 and the imaging area 90. The dome-shaped illumination unit 6 comprises a dome body 61 and a light source unit 62. The dome body 61 is a dome-shaped (may be considered hemispherical or bowl-shaped) rotating body with the optical axis J1 as its approximate center, and opens downwards. The dome body 61 has a dome-shaped inner surface 611 (hereinafter referred to as "dome inner surface 611"). The dome inner surface 611 of the dome body 61 is a reflective surface. The dome inner surface 611 covers the imaging area 90 of the printed circuit board 9. An opening 610 is formed at a position on the dome inner surface 611 that intersects the optical axis J1 (in the example in Figure 1, the upper part of the dome body 61). The X-prism 5 is positioned near the top of the opening 610. When viewed along the optical axis J1, the opening 610 is the size that overlaps with most of the X-prism 5 and is elongated in the longitudinal direction of the prism, similar to the X-prism 5. The first and second emitted light beams from the third side surface 53 of the X-prism 5 enter the dome body 61 through the aperture 610 and illuminate the imaging area 90. Thus, the aperture 610 is a light-transmitting section through which light passes.

[0026] An annular flange 612 is provided at the lower end of the dome body 61, projecting toward the optical axis J1 along its entire circumference. Multiple light sources (e.g., LEDs) 621 of the light source unit 62 are arranged on the upper surface of the annular flange 612 in the circumferential direction (circumferential direction centered on the optical axis J1). The light emitted from the light sources 621 is visible light, similar to the second emitted light. The light from the multiple light sources 621 is reflected (diffuse reflection or specular reflection) by the inner surface 611 of the dome and illuminates the imaging area 90 covered by the inner surface 611 of the dome. That is, illumination light from the inner surface 611 of the dome illuminates the imaging area 90 along various directions different from the optical axis J1. In the imaging device 2, the illumination unit is composed of a first emission unit 3, a second emission unit 4, an X prism 5, and a dome-shaped illumination unit 6.

[0027] The imaging unit 7 is positioned opposite the fourth side surface 54 of the X prism 5 and comprises an image sensor 71 and an imaging optical system 72. In this embodiment, the image sensor 71 is a line sensor. The line sensor extends in the longitudinal direction of the prism. The imaging optical system 72 includes a plurality of lenses, and light emitted from the fourth side surface 54 of the X prism 5 is incident on the imaging optical system 72. The optical axis of the imaging optical system 72 is approximately perpendicular to the fourth side surface 54. As will be described later, the imaging optical system 72 forms an image of the imaging area 90 on the imaging surface of the image sensor 71. As a result, a line image indicating the imaging area 90 is acquired. Note that in the imaging unit 7, an area sensor may be used as the image sensor 71.

[0028] In image acquisition by the imaging device 2, the stage moving mechanism 22 continuously moves the printed circuit board 9 in a direction perpendicular to the imaging area 90 (more precisely, perpendicular to the longitudinal direction of the prism and along the main surface of the printed circuit board 9). The image sensor 71 repeatedly acquires line images in parallel with the movement of the printed circuit board 9, thereby acquiring a two-dimensional multi-gradation image of the printed circuit board 9 (hereinafter referred to as the "imaging image"). In the inspection device 1 in this embodiment, the first imaging image is acquired with the emission of the first emitted light from the first emission unit 3 turned ON, and the emission of light from the second emission unit 4 and the dome-shaped illumination unit 6 turned OFF. The second imaging image is acquired with the emission of the first emitted light from the first emission unit 3 turned OFF, and the emission of light from the second emission unit 4 and the dome-shaped illumination unit 6 turned ON.

[0029] Figure 2 is a magnified view of the X-prism 5, with the first emission section 3 and the second emission section 4 also shown as blocks. As previously described, the X-prism 5 has a first mirror film 56 and a second mirror film 57 that intersect each other. The first mirror film 56 reflects ultraviolet light and transmits visible light. The second mirror film 57 transmits ultraviolet light and reflects and transmits visible light. When acquiring the first image, the first emitted light (ultraviolet light) incident from the first emission section 3 to the first side surface 51 is reflected by the first mirror film 56 and irradiated onto the imaging area 90 of the printed circuit board 9 via the third side surface 53. In Figure 2, the first emitted light is shown by a thick dashed line.

[0030] Figure 3 is a cross-sectional view of a printed circuit board 9. The upper surface of the printed circuit board 9 includes a region where conductive parts 91 are formed by a conductive material such as copper, and a region 92 in which conductive material does not exist according to the design (hereinafter referred to as the "background region 92"). The background region 92 is a region where the substrate or insulating layer of the printed circuit board 9 is exposed. In the background region 92, a material containing resin (such as epoxy resin) is exposed. The example in Figure 3 also includes a dark short defect 93 in which a thin layer of conductive material is present (residual) despite it being the background region 92, causing electrical conductivity between the conductive parts 91.

[0031] The first emitted light irradiated onto the imaging area 90 generates fluorescence (fluorescent light) in the background area 92, excluding the dark short defect 93. The majority of the fluorescence is visible light. On the other hand, the first emitted light is reflected (mainly specularly) in the conductive area 91 and the dark short defect 93, i.e., the area covered by the conductive material. A portion of the fluorescence and a portion of the reflected light of the first emitted light are incident on the third side surface 53 of the X prism 5 along the optical axis J1.

[0032] In the X-prism 5, some of the fluorescence incident on the third side surface 53 is reflected by the second mirror film 57 and heads toward the second emission section 4, while the remaining portion passes through the second mirror film 57. The first mirror film 56 transmits fluorescence. The fluorescence that has passed through the second mirror film 57 and the first mirror film 56 is emitted from the fourth side surface 54 of the X-prism 5 and incident on the imaging optical system 72 of the imaging unit 7. On the other hand, the reflected light of the first emission light incident on the third side surface 53 is reflected by the first mirror film 56 and heads toward the first emission section 3. Therefore, the reflected light of the first emission light does not incident on the imaging optical system 72 of the imaging unit 7. As a result, the imaging unit 7 acquires a fluorescence image showing only the fluorescence in the background region 92 as the first image.

[0033] When acquiring the second image, a portion of the second emitted light (visible light) incident on the second side surface 52 from the second emitter 4 passes through the second mirror film 57 and heads towards the first emitter 3, while the remaining portion is reflected by the second mirror film 57. The reflected second emitted light is irradiated onto the imaging area 90 of the printed circuit board 9 via the third side surface 53. In Figure 2, the second emitted light is shown by a thick solid line. Illumination light from the inner surface 611 of the dome-shaped illumination unit 6 is also irradiated onto the imaging area 90.

[0034] The second emitted light illuminating the imaging area 90 is hardly reflected (specularly reflected) in the background area 92, excluding the dark short defect 93. On the other hand, the second emitted light is reflected by the conductive part 91 and the dark short defect 93. A portion of the reflected light from the second emitted light is incident on the third side surface 53 of the X prism 5 along the optical axis J1. At this time, the reflected light from the upper surface of the conductive part 91 is directed towards the third side surface 53 along the optical axis J1, but the reflected light from the side surface of the conductive part 91 and the dark short defect 93 is directed in a different direction from the optical axis J1 and therefore hardly incident on the third side surface 53. In addition, the illumination light illuminating the imaging area 90 from the inner surface 611 of the dome is for dark-field illumination, and mainly the light reflected from the edge of the upper surface of the conductive part 91 etc. is incident on the third side surface 53 of the X prism 5 along the optical axis J1. Furthermore, the upper surface of the conductive part 91 may be rounded, in which case the illumination light from the dome-shaped illumination part 6 can cause reflected light over a wide area of ​​the upper surface to be incident on the X prism 5.

[0035] In the X-prism 5, a portion of the reflected light incident on the third side surface 53 (reflected light from the second emitted light and reflected light from the illumination light from the dome inner surface 611) is reflected by the second mirror film 57 and heads toward the second emitted section 4, while the remaining portion is transmitted through the second mirror film 57. The first mirror film 56 transmits this reflected light. The reflected light that has been transmitted through the second mirror film 57 and the first mirror film 56 is emitted from the fourth side surface 54 of the X-prism 5 and incident on the imaging optical system 72 of the imaging unit 7. As a result, the imaging unit 7 acquires a reflected light image showing the upper surface of the conductive section 91 as the second image.

[0036] In the inspection unit 11, dark short defects 93 are detected by comparing the fluorescence image and the reflected light image. As previously described, fluorescence does not occur in dark short defects 93 because conductive material is present. Also, the reflected light from the dark short defect 93 is directed in a direction different from the optical axis J1 and is therefore not guided to the imaging unit 7. Thus, in one example of the inspection process, areas darker than a predetermined threshold in both the fluorescence image and the reflected light image are detected as dark short defects 93. Detection of dark short defects 93 using fluorescence images and reflected light images may be performed by other methods. In addition, the inspection unit 11 may detect defects other than dark short defects 93 using fluorescence images.

[0037] As described above, the imaging device 2 in Figure 1 comprises a first emission unit 3, a second emission unit 4, an X prism 5, and an imaging unit 7. The first emission unit 3 emits first emission light, which is ultraviolet light. The second emission unit 4 emits second emission light, which is light in a different wavelength range than ultraviolet light. The X prism 5 is a rectangular prism having first to fourth sides 51 to 54. It emits first emission light incident on the first side 51 from the third side 53 and guides it to the imaging area 90 on the printed circuit board 9, and emits second emission light incident on the second side 52 from the third side 53 and guides it to the imaging area 90. The imaging unit 7 receives fluorescence generated in the imaging area 90 when the first emission light irradiates the imaging area 90, and receives reflected light of the second emission light in the imaging area 90 when the second emission light irradiates the imaging area 90. This makes it possible to realize an imaging device 2 that can appropriately acquire fluorescence and reflected light images of the printed circuit board 9.

[0038] Preferably, the X-prism 5 has a first mirror film 56 and a second mirror film 57 that intersect each other. The first mirror film 56 reflects the first emitted light and transmits the second emitted light. The second mirror film 57 transmits the first emitted light and reflects and transmits the second emitted light and fluorescence. Light from the imaging area 90 is incident on the third side surface 53 of the X-prism 5, and a portion of this light is emitted from the fourth side surface 54 of the X-prism 5 and guided to the imaging unit 7. In this configuration, ultraviolet light directed toward the imaging unit 7 can be blocked by the X-prism 5, and fluorescence images can be appropriately acquired. The characteristics of the first mirror film 56 and the second mirror film 57 may be changed as needed.

[0039] Preferably, the imaging device 2 further includes a dome-shaped illumination unit 6. The dome-shaped illumination unit 6 is positioned on the optical axis J1 between the third side surface 53 of the X prism 5 and the imaging area 90. Illumination light is shone onto the imaging area 90 from a dome-shaped surface (inner surface 611) that covers the imaging area 90, and an opening 610 is formed at a position on this surface that intersects the optical axis J1. By utilizing the dome illumination provided by the dome-shaped illumination unit 6, the imaging device 2 can obtain a desirable reflected light image in which the vicinity of the edge of the conductive part 91 is visible.

[0040] Here, we consider an imaging device of a comparative example, such as the device described in Japanese Patent Publication No. 2016-194434 (Patent Document 1 above), which is equipped with a visible light emitter for coaxial incident illumination and a dome-shaped illumination unit for dome illumination. The imaging device of the comparative example is the imaging device 2 in Figure 1, but with the first emitter 3 omitted and the X prism 5 replaced with a half mirror. In order to enable fluorescence observation in the imaging device of the comparative example, it is necessary to add an ultraviolet light emitter. In this case, for example, it is conceivable to arrange a half mirror for the visible light emitter and a dichroic mirror for the ultraviolet light emitter in order between the imaging device and the dome-shaped illumination unit, but the illumination unit between the imaging device and the printed circuit board becomes complex and large. In addition, the imaging device requires high resolution and telecentricity, and the working distance (WD) between the imaging device and the printed circuit board tends to be shorter. Therefore, the space available for the illumination unit is limited, making it difficult to install the illumination unit.

[0041] In contrast, in the imaging device 2 shown in Figure 1, an X-prism 5 is provided between the imaging unit 7 and the dome-shaped illumination unit 6. On the left and right sides of the X-prism 5 are a first emission unit 3 and a second emission unit 4 that emit light in different wavelength ranges, with a first side surface 51 into which the first emitted light is incident and a second side surface 52 into which the second emitted light is incident facing each other. This prevents the illumination unit, which is positioned between the imaging unit 7 and the printed circuit board 9, from becoming excessively complex and large in the imaging device 2, which is capable of acquiring fluorescent and reflected light images by coaxial incident illumination, thus enabling space saving of the illumination unit. Furthermore, when using a half-mirror or dichroic mirror, as in the imaging device of the comparative example above, ghosting is likely to occur in the images acquired by the imaging unit. On the other hand, in the imaging device 2 using the X-prism 5, the occurrence of ghosting in fluorescent and reflected light images can be suppressed.

[0042] Incidentally, in the background region 92 of the printed circuit board 9, the amount of fluorescence generated by irradiation with ultraviolet light is usually smaller than the amount of reflected light from the conductive parts 91, etc. Therefore, in order to make the imaging speed, i.e., the relative movement speed of the image sensor 71 (line sensor) with respect to the printed circuit board 9 (scanning speed), the same as when acquiring a reflected light image, it is necessary to increase the amount of fluorescence generated (excitation light).

[0043] Figures 4 and 5 show the amount of ultraviolet light irradiated onto the printed circuit board 9 and the amount of fluorescence light generated. The solid line L1 represents the amount of ultraviolet light irradiated, and the dashed line L2 represents the amount of fluorescence light. Figure 4 shows the amount of light when an LED emitting ultraviolet light is used as the light source 31 of the first emission unit 3, and Figure 5 shows the amount of light when a laser diode emitting ultraviolet light is used as the light source 31. In the right side of Figure 4 and in Figure 5, the boundary of the wavelength range of light transmitted by the first mirror film 56 of the X prism 5 is denoted by the symbol B1.

[0044] As shown on the left side of Figure 4, the ultraviolet light emitted from the LED has a wide wavelength range (spectral width), and the fluorescence it generates also has a wide wavelength range. In the imaging device 2, as shown on the right side of Figure 4, only light with a wavelength higher than wavelength B1 is transmitted through the first mirror film 56 and guided to the imaging unit 7. Therefore, in the example of Figure 4, only a portion of the generated fluorescence is used to acquire the fluorescence image. In other words, in the ultraviolet light emitted from the LED, the wavelength range indicated by arrow A1 on the right side of Figure 4 is effective for acquiring the fluorescence image, while the wavelength range indicated by arrow A2 is ineffective for acquiring the fluorescence image. Thus, the ultraviolet light emitted from the LED contains many wavelengths (light) that are not effective for acquiring the fluorescence image, and in order to obtain a high excitation light amount so that the imaging speed is equivalent to that when acquiring reflected light images, it is necessary to irradiate the printed circuit board 9 with a large amount of light energy. In this case, there is a possibility that the printed circuit board 9 may be damaged due to heat generation.

[0045] On the other hand, the ultraviolet light emitted from a laser diode has a narrow wavelength range, as shown in Figure 5. Therefore, by using a laser diode, it is possible to irradiate the printed circuit board 9 with ultraviolet light that contains many wavelengths effective for acquiring fluorescence images and few wavelengths ineffective for acquiring fluorescence images. In the example in Figure 5, the wavelength range of the light emitted from the laser diode hardly overlaps with the wavelength range of fluorescence. In the imaging device 2, since the light source of the first emission unit 3 is a laser diode, it is possible to generate sufficient fluorescence while reducing the amount of light energy irradiated onto the printed circuit board 9. As a result, fluorescence images can be appropriately acquired while reducing damage to the printed circuit board 9. Depending on the type of object being imaged by the imaging device 2, a light source other than a laser diode (LED, solid-state laser, lamp, etc.) may be used in the first emission unit 3. Light sources other than LEDs may also be used in the second emission unit 4 and the dome-shaped illumination unit 6.

[0046] The imaging device 2 and inspection device 1 described above can be modified in various ways.

[0047] In the imaging device 2, for example, the optical axis J1 extending from the X prism 5 to the imaging area 90 of the printed circuit board 9 may be inclined with respect to the vertical direction. In this case, the fluorescence generated in the imaging area 90 and the reflected light of the second emitted light in the imaging area 90 may be guided to the imaging unit 7 without passing through the X prism 5. Thus, the imaging device 2 is not limited to coaxial incident illumination. Also, in the imaging device 2 of Figure 1, for example, the arrangement of the imaging unit 7 and the second emitted unit 4 may be swapped. In this case, in the X prism 5, the surface facing upward in Figure 1 becomes the second side surface 52, and the surface facing to the right becomes the fourth side surface 54. Thus, the arrangement of the first emitted unit 3, the second emitted unit 4 and the imaging unit 7 with respect to the X prism 5 may be changed as appropriate.

[0048] In the imaging device 2, the first emitted light and the second emitted light may be emitted simultaneously from the first emitted unit 3 and the second emitted unit 4. In this case, for example, the imaging unit 7 is provided with an optical element (such as a dichroic mirror) that separates the second emitted light from the fluorescence, and the reflected light image and the fluorescence image are acquired simultaneously by the two image sensors.

[0049] In the dome body 61 of the dome-shaped illumination unit 6, a transparent member that transmits light in the wavelength range of the first emitted light, the second emitted light, and fluorescence may be provided in the opening 610. In the imaging device 2 including the dome-shaped illumination unit 6, it is sufficient that the dome body 61 is provided with a light-transmitting portion that transmits the first emitted light, the second emitted light, and fluorescence.

[0050] Depending on the design of the dome-shaped illumination unit 6, multiple light sources may be provided on the inner surface 611 of the dome. Depending on the object being imaged by the imaging device 2, the dome-shaped illumination unit 6 may be omitted.

[0051] The stage 21 may be fixed, and a moving mechanism may be provided that moves the first emission unit 3, the second emission unit 4, the X prism 5, the dome-shaped illumination unit 6, and the imaging unit 7 as a single unit.

[0052] The object in the imaging device 2 does not have to be the printed circuit board 9, as long as it generates fluorescence when irradiated with ultraviolet light.

[0053] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other. [Explanation of Symbols]

[0054] 1. Inspection device 2. Imaging device 3. First ejection section 4. Second ejection section 5 Cross Dichroic Prism 6. Dome-shaped lighting section 7 Imaging Unit 9 Printed circuit boards 11. Inspection Department 21 stages 51-54 (Side view of a cross dichroic prism) 56 First mirror film 57 Second mirror film 71 Image sensor 90 imaging area 610 Opening 611 Dome interior J1 optical axis

Claims

1. An imaging device for imaging an object, A stage for holding the object, A first emission unit that emits first emission light which is ultraviolet light, A second emission unit that emits second emission light, which is light in a different wavelength range than ultraviolet light, A cross dichroic prism is a rectangular prism having first to fourth sides, which emits first light incident on the first side from the third side and guides it to the imaging area on the object, and emits second light incident on the second side from the third side and guides it to the imaging area, An imaging unit that receives fluorescence generated in the imaging area when the first emitted light is irradiated onto the imaging area, and receives reflected light of the second emitted light in the imaging area when the second emitted light is irradiated onto the imaging area, An imaging device equipped with the following features.

2. The imaging apparatus according to claim 1, The cross dichroic prism has a first mirror film and a second mirror film that intersect each other. The first mirror film reflects the first emitted light and transmits the second emitted light, The second mirror film transmits the first emitted light and reflects and transmits the second emitted light and the fluorescence. Light from the imaging region is incident on the third side surface of the cross dichroic prism, An imaging device in which a portion of the aforementioned light is emitted from the fourth side surface of the cross dichroic prism and guided to the imaging unit.

3. The imaging apparatus according to claim 2, An imaging device in which the first side and the second side of the cross dichroic prism face each other, and the third side and the fourth side face each other.

4. The imaging apparatus according to claim 1, The imaging unit has a line sensor as the image sensor, An imaging device in which the cross dichroic prism is elongated in the direction along the first to fourth side surfaces.

5. The imaging apparatus according to claim 1, An imaging device in which the light source of the first emission unit is a laser diode.

6. The imaging apparatus according to claim 1, An imaging device further comprising a dome-shaped illumination unit, which is positioned on the optical axis between the third side surface of the cross dichroic prism and the imaging region, and which illuminates the imaging region with illumination light from a dome-shaped surface covering the imaging region, and which has a light-transmitting portion provided at a position on the surface intersecting the optical axis.

7. The imaging apparatus according to claim 1, An imaging device in which the object is a printed circuit board.

8. An inspection device, An imaging device according to any one of claims 1 to 7, An inspection unit that inspects the images acquired by the aforementioned imaging device, An inspection device equipped with the following features.

Images