JPH0434346A - Image reading system - Google Patents

Abstract

PURPOSE:To increase the quantity of sensed light in an image sensor and thereby to increase the precision in detection of an image by a construction wherein a light source for vertical illumination of a surface to be inspected is disposed in a part of an angular aperture of an imaging optical system. CONSTITUTION:A light source 110 for vertical illumination is constructed of a combination of a light source 111 for regular reflection with light sources 112 and 113 for diffused reflection, and the light source 111 for regular reflection is disposed in a part of an angular aperture of an imaging optical system 140. Accordingly, a light from the light source 110 for vertical illumination is applied onto a surface to be inspected of a printed circuit board 20 without passing through a half mirror or the like. Although part of a light reflected on the surface to be inspected is by the light source 110, the remainder reaches CCD linear image sensors 161 and 162 through the imaging optical system 140. According to this constitution, a respectable part of the light from the light source 110 enters the image sensors 161 and 162 and thus the precision in detection of an image in the image sensors 161 and 162 is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image reading system used in an optical visual inspection device for printed circuit boards, etc., and particularly relates to an image reading system for increasing the amount of light incident on an image sensor. Regarding improvements.

[Background of the invention]

As is well known, in a printed circuit board, a metal wiring pattern is formed on one or both sides thereof, and through holes for mounting electronic components are formed in a direction penetrating the board. Various types of optical appearance inspection devices are used to inspect whether these wiring patterns and through holes are formed with accuracy within tolerance.

[Conventional technology]

FIG. 13 is a conceptual diagram showing a conventional example of an image reading system used in a wiring pattern inspection device. Light 2 generated by a light source 1 is reflected by a half mirror 3 and irradiated onto the surface of a printed circuit board 5. This printed circuit board 5
A wiring pattern 6 and a through hole 7 are formed on the surface, and the reflected light 8 obtained by reflecting the light 2 on the surface is focused on the linear image sensor 9 via the half mirror 3 and the imaging lens 4. Image.

The first example of the light reception level in the linear image sensor 9 is
This is shown in Figure 4, and this light reception level is shown in Figure 13.
corresponds to a linear image along a line. Since the wiring pattern 6 is made of metal, its light reflectance is high, and the level of light received corresponding to this wiring pattern 6 is also high. On the other hand, the level of light received from the insulating base 5a of the substrate 5 is relatively small, and since the light 2 is transmitted downward through the through hole 7, the level of light received therefrom is substantially zero. Therefore, by determining the light reception level using the threshold TH, it is possible to understand the image of the wiring pattern 6.

A method has also been proposed in which another light source is placed on the back side of the printed circuit board, and the light transmitted from the other light source through the through-hole is detected together with the reflected light by a single image sensor. An example of this is the technique described in Japanese Patent Publication No. 62-29737.

[Problem to be solved by the invention]

In the device shown in FIG. 13, only half of the light 2 from the light source 1 is reflected by the half mirror 3 and directed toward the printed circuit board 5. Further, of the light 8 reflected by the printed circuit board 5, only half of the amount of light passes through the half mirror 3 and reaches the image sensor 9. Therefore, even if the light reflectance in the wiring pattern 6 is 100%, the amount of light reaching the image sensor 9 is 1/4 of the amount of light emitted from the light source 1.

Therefore, the amount of light received by the image sensor 9 is relatively small, and there is a problem that image detection accuracy is not necessarily high. This is a common problem not only in devices used for visual inspection of printed circuit boards, but also in visual inspection devices for various objects to be inspected.

[Purpose of the invention]

The present invention is intended to overcome the above-mentioned problems in the prior art, and it is an object of the present invention to provide an image reading system that increases the amount of light received by an image sensor and improves image detection accuracy.

[Means to solve the problem]

In order to achieve the above object, a first configuration of the present invention includes an image detection section having an image sensor and an imaging optical system, and detects an optical image of the surface to be inspected by the image detection section. In an image reading system used for performing a visual inspection of a surface to be inspected, a light source for epi-illuminating the surface to be inspected is arranged at a part of the aperture angle of the imaging optical system.

Preferably, a light source for epi-illumination is arranged at a position tangent to the optical axis of the imaging optical system.

[Effect]

Light from a light source for epi-illumination is irradiated onto the surface to be inspected without passing through a half mirror or the like. A portion of the light reflected by the surface to be inspected is vignetted by the light source, but the remaining portion reaches the image sensor via the imaging optical system. Therefore, a considerable portion of the light from the light source will be incident on the image sensor, improving the image detection accuracy of the image sensor. When the light source is arranged so as to be in contact with the optical axis of the imaging optical system, the reflected light that reaches the image sensor without being eclipsed by the light source is approximately 1/2 of the reflected light that travels toward the entrance pupil of the image detection unit. Become.

〔Example〕

<A. Overall Configuration> FIG. 1A is a cutaway plan view of a printed circuit board inspection apparatus 10 incorporating an image reading system according to an embodiment of the present invention, and FIG. 1B is a side view thereof. This device 1
0 includes a lower housing 11 and an upper housing 12, and a horizontally movable table 13 is provided near the opening of the upper surface of the lower housing 11. The movable table 13 has a structure in which a glass plate 15 is attached within a rectangular frame 14, and the lower surface 15a of this glass plate 15 is a slotted surface. Then, the upper surface 15 of the glass plate 15
A printed circuit board 2o is placed on b, and this glass plate 1
Supported by 5.

As shown in FIG. 2, the printed circuit board 2o has an insulating base plate 21 made of glass epoxy and a printed wiring pattern 22' made of copper formed on one or both sides of the insulating base plate 21. The printed wiring pattern 22 has a wiring portion 23 and a land 24, and a through hole 25 passing through the printed circuit board 20 is formed in the land 24.

Returning to FIGS. 1A and 1B, the frame 14 can slide on a pair of guide rails 16, and a ball screw 17 extends in a direction parallel to the guide rails 16. A ball nut 19 fixed to the frame 14 is screwed into this ball screw 17, and when the ball screw 17 is rotated by the motor 18, the movable table 13 is moved horizontally (
±Y) direction.

Meanwhile, an image reading system 50 is provided inside the upper housing 12. At the upper center of the image reading system 50, an optical radar array 100 extending in the horizontal (±X) direction is arranged. This optical radar array 100 includes eight optical heads HO to H7, and these optical heads HO to H7 are supported by a support member 101 at equal intervals. This support member 101 can slide in the (±X) direction on a guide member 102, and the guide member 102 is a pair of side frame members 51a.

51b. This side frame material 51a,
51b is the housing 11. ．． 12 in a fixed position. Further, the support member 101 is coupled to a motor 103 via a ball nut (not shown) and a ball screw 104. Therefore, when the motor 103 is rotated, the optical heads HO to H7 are moved together with the support member 101 (±X
) direction.

A light source 120 for transmitted illumination is provided below the optical heads HO to H7.
is located. This light source 120 includes a large number of infrared L
The EDs are arranged in the (±X) direction and essentially function as a linear light source.

This light source 120 is supported from the side frame 51 by support rods 121 and 122. In addition, the optical head HO
A light source 110 for epi-illumination is attached to the lower part of each of H7. As will be detailed later, this light source 110
has three one-dimensional arrays of red LEDs extending in the (±X) direction.

A presser roller mechanism 20 is provided before and after the optical radar array 100.
OA and 200B are provided. Front roller mechanism 20
0A includes eight roller units 210A, which are attached to side frames 51a and 51b via shafts 201A.

The rear roller mechanism 200B also has eight roller units 210.
B, and is attached to the side frames 51g, 51b via a shaft 201B. These roller units 21OA and 210B have rubber rollers supported by swingable arms, and the rubber rollers and arms are biased by springs. These roller mechanisms 20OA and 200B are connected to the printed circuit board 20.
It is provided to hold down the substrate 20 and prevent it from shifting and bending when the substrate 20 is sent downward.

A pair of operation switch panels 26 are attached to the upper surface of both sides of the lower housing 11. These switch boards 2
6 are provided with the same group of switches, so that the switches can be easily operated from either side of the housing 11. Further, in the upper housing 12, a data processing device 300 for performing various data processing and operation control is arranged.

<B. General operation> Before explaining the detailed configuration of this test bag [10]
The general operation of No. 10 will be described below. First, the printed circuit board 20 is placed on the glass plate 15 in the state shown in FIGS. 1A and 1B.
is placed on top of the When the switch board 26 is operated, the motor 18 rotates forward, and the printed circuit board 20 moves in the (+Y) direction together with the moving table 13. Further, the light sources 110 and 120 are turned on.

When the printed circuit board 20 reaches the position of the image reading system 50 as the table 13 moves, the rollers of the presser roller mechanisms 200A and 200B press the printed circuit board 20 toward the glass plate 15 while moving the board 20. Rotate. The epi-illumination from the light source 110 causes the images of the wiring patterns 22 (FIG. 2) to be read line-by-line by the optical heads HO to B7, and the transmitted-light illumination from the light source 120 causes the images of the through-holes 25 to be read line-by-line by the optical heads. It is read from HO to B7.

The internal structure of the optical heads HO to H7 for this reading will be described later.

By the way, although the optical heads HO to H7 are arranged in a straight line, there is a gap between each field of view.
Even if the printed circuit board 20 is moved in the (+Y) direction, the entire image on its surface cannot be read. Therefore, after the printed circuit board 20 is moved in the (+Y) direction, the motor 103 is driven, and the optical heads HO to H7 are thereby driven.
Move the entire area in the (+X) direction. The amount of movement is half the mutual arrangement pitch of the optical heads HO to H7.

After this movement, the motor 18 is reversely rotated to move the printed circuit board 20 in the (-Y) direction, and the wiring patterns 22 and through holes 2 formed by the optical heads HO to H7 are
Read the image with 5.

As a result, the scan shown by the solid line arrow A1 and the scan shown by the broken line arrow A2 in FIG. The read image is processed by the data processing device W.
300 and according to predetermined standards wiring pattern 2
2 and the through hole 25 are judged to be good or bad.

Details of C8 Optical Head> FIG. 3A is a schematic side view showing the internal configuration of the optical head HO. Although FIG. 3A shows one optical head HO, the other optical heads H1 to H7 also have the same structure.

The optical head HO has a casing 130, and supports 11.6, 1 are attached to the lower part of the casing 130.
A light source 110 for epi-illumination is suspended by 17. The light source 110 includes a regular reflection light source 111 and a diffuse reflection light source 11
2,113, each light source 111,112
．． ．． Each of 113 has a wavelength λ, (-800 to 7
It is essentially a linear light source consisting of a -dimensional array of red LEDs 115 (FIG. 3B) that generate red light (00 ns).

Among these, the light sources 112 and 113 for diffuse reflection are arranged at a position quite far from the optical axis LA of the imaging lens system 140 provided in the optical head HO, but the light sources 112 and 113 for regular reflection
11 is provided at a position where its end is in contact with the optical axis LA. As will be described later, the imaging lens system 140 is for forming images of the wiring pattern 22 and the through hole 25 of the printed circuit board 20 on the CCD linear image sensors 161 and 162, respectively. The light sources 112 and 113 for diffuse reflection are arranged outside the aperture angle for image formation, and the light source 111 for regular reflection is arranged in a part of the aperture angle.

Light from these light sources 111, 112, and 113 is irradiated toward the inspection area AR, which is located directly under the optical head HO at that time on the upper surface of the printed circuit board 20.

Regular reflection light source 111 and diffuse reflection light source 1 for epi-illumination
12 and 113 are provided because the surface of the wiring pattern 22 is not necessarily a mirror surface, so in order to accurately capture the image of the wiring pattern 22, it is necessary to utilize both specular reflection and diffused reflection from the wiring pattern 22. This is because it is preferable. Note that the light sources 111, 11.2, and 113 described above are shielded from light on the imaging lens system 140 side (upper side in the figure).

On the other hand, the transmission light source 120 has a wavelength λ2 (-700~
Infrared LED 125 (1000n■) that generates infrared light
It consists of a one-dimensional array (Figure 3B). This light source 12
0 is provided on a line perpendicular to the optical axis LA of the imaging lens system 140. The light source 120 irradiates infrared light in the (+2) direction toward an area of the back surface of the printed circuit board 20 that corresponds to the back side of the area to be inspected AR.

The red light emitted from the epi-illumination light sources 111, 112, and 113 toward the inspection area AR is reflected in the inspection area A.
It is reflected by R. In addition, a portion of the infrared light emitted from the transmitted illumination light source 120 toward the through hole 25 passes through the through hole 25 . Then, these reflected light and transmitted light head toward the optical head HO as spatially overlapping composite light.

As shown in FIG. 4A, a light beam is directed from the inspection area AR of the printed circuit board 20 into the range of the entrance pupil of the imaging lens system 140. Of these, only the portion corresponding to half reaches the imaging lens system 140, and the remaining portion Lb corresponding to the remaining half is obscured by the light source 111 and its support member 116. Therefore, the portions L and Lb are each referred to as an "effective luminous flux".

If we call it an "ineffective light beam," then the projection solid angle ω of the effective light beam La (complex light intake angle of the imaging lens system 140) and the projection solid angle ω5 of the invalid light beam are each a light beam. The projection solid angle (aperture angle) ω. It is half of that. That is, the following equations (1) to (4) hold true.

ω + ωb-ω0 ... (1) ω
■a11ωD...(2)ω
b = (1a) ・ω0 ... (3) α-
1/2...(4
) The effective luminous flux is the imaging lens system 1 as shown in FIG. 3A.
40 and enters the cold mirror 150. The cold mirror 150 is a mirror that transmits only infrared rays. Therefore, the effective luminous flux.

Among the light included in the red light (i.e., the printed circuit board 2
The reflected light LR) from the surface of the mirror 150 is reflected by the mirror 150, travels in the (+Y) direction, and forms an image on the light receiving surface of the first CCD, linear image sensor 161. In addition, the infrared light included in the effective luminous flux La (the transmitted light L of the through hole 25
T) passes through the mirror 150 and forms an image on the light receiving surface of the second CCD linear image sensor 162.

These CCD linear image sensors 161 and 162 have CCD light receiving cells arranged one-dimensionally in the (±X) direction. Therefore, the first linear image sensor 161 detects a one-dimensional image of the surface of the printed circuit board 20 due to epi-illumination, and the second linear image sensor 162 detects a one-dimensional image of the through-hole 25 due to transmitted illumination. and,! 2. In Figure ll1IA and Figure 1B. By relatively moving the printed circuit board 20 and the optical RAD array 100 using the illustrated moving mechanism,
Each area of the printed circuit board 20 is scanned, and the wiring pattern 22 and through hole 25 for each area are scanned.
A dimensional image is grasped.

The image signals 11 to 162 from the linear image sensors 161 and 162 are digitized by a circuit to be described later, and then the threshold values TH1,
It is binarized using TH2. However, FIG. 5(a) shows an example of the image signal PSo obtained by the first linear image sensor 161, and FIG. 5(b) shows an example of the image signal H8o obtained by the second linear image sensor 162. It shows.

FIG. 3B is a schematic front view of the optical head HO shown in FIG. 3A, and in FIG. 3B, for convenience of illustration,
The first linear image sensor 161 is omitted.

Furthermore, the optical path within the optical head IO is also shown for only the light transmitted through the through holes. In this embodiment, a telecentric lens system is used as the imaging lens system 140, which is telecentric both on the printed circuit board 20 side and on the linear image sensor 161, 162 side. Therefore, the imaging optical axis of the transmitted light from each through hole 25 within the field of view of this lens system 140 is parallel to the optical axis LA of the lens system 140 itself, both in front and behind the lens system 140. .

The image reading system 50 having the above configuration has the following advantages.

(1) Lens system 140 from the surface of the printed circuit board 20
Half of the light directed toward the entrance pupil of is imaged on linear image sensors 161 and 162. On the other hand, in the conventional example shown in FIG. 13, as described above, the image sensor 9
The light 8 reaching the is 1/4 of the light 2 from the light source 1.

FIGS. 6A and 6B are schematic diagrams showing the range into which light from the printed circuit board actually enters in the entrance pupil of the imaging lens system and the density of light flux passing through the range in the conventional example and the example. Figure 16A corresponds to the conventional example in Figure 113, in which light enters the entire area of the entrance pupil, but the density of the light flux passing through it is equal to that of the light source 1.
This is 1/4 or less of the generated luminous flux density. On the other hand, in FIG. 6B (embodiment), only half of the entrance pupil is used, but the density of the amount of light passing therethrough is four times that of the conventional example. However, in this comparison, in the example, the specular reflection light source 111
I'm only thinking about.

For this reason, the linear image sensor 161 in the embodiment
The amount of light incident on the image sensor 9 is twice the amount of light incident on the image sensor 9 in the conventional example, and an image with strong contrast and less susceptible to noise can be obtained.

By the way, as shown in FIG. 7, the imaging lens system 140a
It is also possible to consider a technique in which the optical axis LA is inclined by an angle (+φ) from the normal direction NA of the printed circuit board 20, and the specular reflection light source 111a is inclined by an angle (−φ) from the normal direction NA. If the value of the angle φ at this time is increased to a certain extent, the reflected light from the printed circuit board 20 will be incident on the imaging lens system 140a without being vignetted by the light source 111a.
The amount of light incident on the linear image sensor is twice that of the example.

However, in this case, image detection is performed in a direction tilted from the normal direction NA, and image detection is not performed directly above the area to be inspected.

This situation is schematically shown in FIG. 6C, and the deviation of the light receiving range from the cross point in the figure represents such an inclination. If such an inclination exists, it is not possible to focus on the entire area to be inspected, which causes blurring and distortion in the detected image of the wiring pattern 22, reducing the detection accuracy.

On the other hand, such a problem does not occur with the arrangement of the embodiment.

In addition, in the embodiment, the mirror 150 disposed above the imaging lens system 140 is not a half mirror, and substantially all of the light beam incident on this mirror 150 among the specularly reflected light is reflected. The amount of light will never be halved.

(2) Since the image of the wiring pattern 22 and the image of the through hole 25 can be obtained at the same time, the appearance inspection can be performed at high speed. Further, since the imaging lens system 140 is used for both the image detection of the wiring pattern 22 and the image detection of the through hole 25, there is no need to provide a plurality of imaging lens systems in parallel within one optical head.

(3) As shown in FIGS. 5(a) and 5(b), since the image of the wiring pattern 22 and the image of the through hole 25 are detected separately by the linear image sensors 161 and 162, the threshold levels THI and TH2 are detected separately. can be individually set to the optimum value without considering their mutual relationship. As a result, even if the light reception level of each image varies spatially, each image can be accurately grasped.

(4) Since the imaging lens system 140 is a telecentric lens system, it is possible to accurately capture the image of a small diameter through hole such as a mini via hole. The reason is as follows. That is, first, in the mini-via hole, as shown in FIG. 8, the ratio (aspect ratio) between the length (depth) H and the diameter is, for example, H/D-1,6■■/ 0.3+m■-5,3...
(5). Therefore, when a non-telecentric lens system 141 is used as shown in FIG. 9A, the holes 25a and 25b located far from the optical axis of the lens system become shadows of transmitted illumination, and correspondingly, in the image signal obtained in [7],
As shown in FIG. 10A, portions of hole images 25A and 25B corresponding to holes 25a and 25b are missing.

On the other hand, if the telecentric lens system 140 is used as in this embodiment, the hole 2 located far from the optical axis
Images 5a and 25b can also be captured accurately (see Figures 9B and 10B).

(5) Since the lower surface 15a (FIG. 2) of the glass plate 15 is a scratched surface, the light from the transmission light source 120 is uniformly irradiated onto the back surface of the substrate 20. Therefore, the light reception level on the image of the through hole 25 becomes uniform.

<D. Electrical Configuration> FIG. 11 is a block diagram showing the electrical configuration in this embodiment. The wiring pattern image signal pso-pS and the through-hole image signal BSo-H57 obtained from each optical helad HO to H7 are the A/D converter 30
After being converted into a digital signal by 1, the binarization circuit 3
Given to 02,303.

FIG. 12 shows details of a combination 304 of binarization circuits 302 and 303 corresponding to the optical head HO. The binarization circuits 302 and 303 are comparators 305 and 30.
6, and threshold values TH1 and TH2 held in registers 307 and 308 are applied to these comparators 3.
05,306. Comparators 305, 306
are these thresholds THI, TI (see Figure 5 for comparing the image signals ps, pso after being digitized with 2), and the signals pso, HSo are lower than the thresholds THI, TH2.
When the level is high, it becomes “H”, and when it is low, it becomes “L”.
', respectively, are output. The binarization circuits 302 and 303 corresponding to the other optical heads H1 to H7 have a similar configuration, and the threshold values TH1 and TH2 from the registers 307 and 308 are set for each pair of the binarization circuits 302 and 303. Commonly used.

Returning to FIG. 11, the binarized image signal obtained in this manner is provided to a pattern inspection circuit 400.

The pattern inspection circuit 400 constructs a two-dimensional image of the wiring pattern 22 and the through hole 25 based on these image signals, and determines whether the image is good or bad according to a predetermined standard.

The data processing device 300 is also provided with a control circuit 310. The control circuit 310 is a lighting circuit 311.312
In addition to giving on/off commands to the light sources 110 and 120 via the controllers, it also outputs drive control signals to the motors 18 and 103.

Further, the motor 18 is provided with a rotary encoder 18E, and a motor rotation angle signal detected by the rotary encoder 18E is taken into the control circuit 310. This rotation angle signal defines data processing timing.

With the above configuration, the optical inspection apparatus 10 shown in FIGS. 1A and 1B accurately performs the visual inspection of the printed circuit board 20.

<E, Other Examples> (1) The specular reflection light source 111 is the optical head HO to H7.
It is only necessary to arrange it at a part of each aperture angle, and it is not necessarily necessary to be in contact with the optical axis LA of the imaging lens system 140. That is, the value of the parameter α in the equations (1) to (3) described above can be variously selected within the range of 0 × α<1 (6). When the value of the parameter α is set to a relatively large value, the effective aperture angle of the optical heads HO to H7 becomes wider (FIG. 4B). However, in this case, the light source 111
Since the light is incident on the surface of the printed circuit board 20 at a shallow angle, the reflection angle of its specular reflection also becomes shallow, and the amount of reflected light (effective luminous flux) incident on the imaging lens system 140 is reduced. When the value of the parameter a is set to a relatively small value, the reflection angle becomes large, but the effective aperture angle becomes narrow, and as a result, the amount of effective luminous flux also decreases.

The amount of effective luminous flux is the solid angle ω in equations (1) to (8)
8. It can be considered that it is proportional to the product of ωb.

The solid angle ω expresses the width of the effective aperture angle of the imaging lens system 140, and the solid angle ω5 affects the reflection angle at which the light emitted from the light source 111 is reflected on the surface of the printed circuit board 20.

Therefore, the light quantity Q of the effective luminous flux can be written as Q-Cω8ωb (7) using the proportionality constant C, but using the theorem that the arithmetic mean is greater than the geometric mean, the following equation ( 8) is obtained.

Q-Cω8 ω b ≦ C (ω + ωb) /4 (8) And,
Using the condition of equation (1), Q ≦ Cω /4
...(9)O, ω, -ωb ...(lO)
When , Q becomes the maximum value Cω /4. In the embodiment shown in FIG. 4OA, formula (10), that is, α-1
This is the reason why /2 is made to hold.

(2) The present invention is applicable not only to the visual inspection of printed circuit boards, but also to image reading systems in various inspection apparatuses, such as visual inspection of magnetic disks and semiconductor wafers.

〔Effect of the invention〕

As described above, according to the first aspect of the invention, it is possible to illuminate the surface to be inspected and read the image thereof without using a half mirror, so that the amount of light incident on the image sensor increases. As a result, the image of the surface to be inspected can be detected with high precision.

Further, in the invention as set forth in claim 2, since the amount of reflected light incident on the imaging optical system can be maximized, the above-mentioned effect becomes particularly remarkable.

[Brief explanation of the drawing]

1A is a partially cutaway plan view of an optical inspection device for printed circuit boards incorporating an image reading system according to an embodiment of the present invention; FIG. 1B is a partially cutaway side view of the device shown in FIG. 1A; FIG. 2 is a diagram showing an example of a printed circuit board, FIG. 3A is a schematic side view of the optical head used in the example, and FIG. 3B is a schematic front view of the optical head shown in FIG. 3A. FIG. 4A is a diagram showing the relationship between the arrangement position of the specular reflection light source and the incident light flux to the imaging lens system, and FIG. 4B is a diagram showing the relationship between the arrangement position of the light source for specular reflection and the incident light flux to the imaging lens system in another embodiment of the present invention. FIG. 5 is a waveform diagram showing an image signal obtained by the system of the embodiment and its binarization process, and FIG. 6A to FIG.
Figure C is a schematic diagram showing the range of incidence and amount of incident light on the imaging lens system for a conventional example, an example, and a comparative example, Figure 7 is an explanatory diagram of the arrangement in the comparative example, and Figure 8 is: The explanatory diagram of the mini-buy 7 holes, Figures 9A and 9B, are as follows:
An explanatory diagram of a non-telecentric lens system and a telecentric lens system, FIGS. 10A and 10B are diagrams showing a hole image obtained through a non-telecentric lens system and a hole image obtained through a telecentric lens system, 11 and 12 are diagrams showing the electrical configuration of the apparatus shown in FIGS. 1A and 1B, FIG. 13 is a principle diagram of a conventional image reading system, and FIG. 14 is a diagram showing the electrical configuration of the device shown in FIGS. FIG. 3 is a waveform diagram showing an example of an image signal obtained by the system. 10... Printed circuit board inspection device, 13... Moving table, 20... Printed circuit board,
50... Image reading system, 110... Light source for epi-illumination, 111... Light source for specular reflection, 112.113... Light source for diffused reflection, 120... Light source for transmitted illumination, 140-... Conclusion Image lens system, 150...Cold mirror 161.162...CCD linear image sensor, H
O-H7... Optical head 2nd rEJ 3A 110: Epi-illumination light source 111: Specular reflection light source 112.113: Diffuse reflection light source 161: 162: CCD linear image sensor 25
B Figure 0A Figure 0B Figure bA 2mm Figure A Figure B Figure holder Figure Figure

Claims (2)

[Claims] (1) An image that is provided with an image detection section having an image sensor and an imaging optical system, and that is used to perform an external appearance inspection of the surface to be inspected by detecting an optical image of the surface to be inspected by the image detection section. An image reading system, characterized in that a light source for epi-illuminating the surface to be inspected is disposed at a part of the aperture angle of the imaging optical system. (2) The image reading system according to claim 1, wherein the light source for epi-illumination is arranged at a position tangent to the optical axis of the imaging optical system.