JP7709901B2 - Reading device, inspection device, reading system, and method for manufacturing reading device - Google Patents

Description

The present invention relates to a reading device, an inspection device, a reading system, and a method for manufacturing a reading device.

Patent Document 1 shows a lens array that forms an erect life-size image by arranging a large number of optical fibers with a refractive index distribution in a direction perpendicular to the optical axis in a straight line. When using a lens array that forms an erect life-size image in this way, the images of two adjacent lenses are superimposed on the sensor, but since the same image is formed at the same position on the sensor, the superposition does not cause any problems.

Japanese Patent Application Publication No. 6-342131

When a lens array such as that shown in Patent Document 1 is applied to a reading device, the overlap of images synthesized by multiple adjacent lenses can cause the depth of field to become shallow, leading to a deterioration in the quality of the resulting image. In particular, when a lens array such as that shown in Patent Document 1 is applied to a reduction optical system to deepen the depth of field, the positions of the images formed on the sensor by two adjacent lenses will be shifted from each other (images at the same position on the subject will be formed at different positions on the sensor). As a result, different images will be superimposed on the sensor, and a clear image of the subject will no longer be formed on the sensor.

The present invention aims to provide technology that is advantageous for improving the image quality of reading devices.

In view of the above problems, a reading device according to an embodiment of the present invention is a reading device including a sensor including a plurality of pixels arranged along a main scanning direction, and a plurality of lens blocks, each of the plurality of lens blocks including a plurality of rod lenses arranged along a direction intersecting an optical axis, the plurality of rod lenses included in each of the plurality of lens blocks including a lens in use that forms an image on the sensor and a lens not in use that does not form an image on the sensor, the lens in use of each of the plurality of lens blocks is arranged along the main scanning direction, and the plurality of lens blocks are arranged at a distance from each other along the main scanning direction.

The above means provide technology that is advantageous for improving the image quality of the reading device.

FIG. 1 is a perspective view showing an example of the configuration of a reading device according to an embodiment of the present invention. 2A and 2B are a plan view and a cross-sectional view of the reading device of FIG. 1; FIG. 2 is a perspective view showing a modified example of the reading device of FIG. 1 . 4A and 4B are a plan view and a cross-sectional view of the reading device of FIG. 3; FIG. 1 is a diagram showing an example of the configuration of an inspection device and a reading system in which a reading device according to the present embodiment is incorporated.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. In addition, the same reference numbers are used for the same or similar configurations, and duplicate descriptions are omitted.

A reading device according to an embodiment of the present disclosure will be described with reference to Figures 1(a) and 1(b) to 5(a) and 5(b). Figure 1(a) is a perspective view showing an example of the configuration of a reading device 100 according to this embodiment, Figure 1(b) is a plan view of a lens block 101 used in the reading device 100, and Figure 2 is a plan view and a cross-sectional view of the reading device 100.

The reading device 100 includes a sensor 102 including a plurality of pixels arranged along a main scanning direction 151, and a plurality of lens blocks 101. Each of the plurality of lens blocks 101 includes a plurality of rod lenses 110 arranged along a direction intersecting the optical axis. The plurality of rod lenses 110 included in each of the plurality of lens blocks 101 include a used lens 111 that forms an image on the sensor 102, and an unused lens 112 that does not form an image on the sensor 102. The used lens 111 can be said to be a lens that guides light to the sensor 102. The unused lens 112 can be said to be a lens that does not guide light to the sensor 102. The used lenses 111 of each of the plurality of lens blocks 101 are arranged along the main scanning direction 151 (specifically, they are arranged on a virtual line indicated by the symbol 152). In other words, they are arranged in a straight line (on a virtual line) parallel to the main scanning direction. Furthermore, the lens blocks 101 are spaced apart from one another along the main scanning direction 151. Note that the state in which the lens blocks 101 are spaced apart from one another along the main scanning direction 151 means that the lens blocks 101 are spaced apart on a straight line parallel to the main scanning direction 151. In other words, even if the lens blocks 101 adjacent to one another in the main scanning direction 151 overlap when viewed from the sub-scanning direction perpendicular to the main scanning direction 151, they only need to be spaced apart in the main scanning direction 151.

When a rod lens array having multiple rod lenses is arranged so that the rod lenses are aligned in the main scanning direction, some of the light emitted from adjacent rod lenses overlaps on the sensor 102. The overlap of images synthesized by multiple rod lenses can cause a decrease in image quality.

In this embodiment, as shown in Figures 1(a) to 2, the lenses 111 used that form an image on the sensor 102 are arranged at a distance from each other along the main scanning direction 151. This prevents the overlap of images synthesized by multiple adjacent rod lenses. Figures 1(a) and 2 show an image circle 121 on which the lens 111 used forms an image. The area of the image circle 121 is defined by the focal length f of the lens 111 used, the distance from the light exit surface of the lens 111 used to the sensor 102, and the aperture angle of the lens 111 used. The aperture angle is the maximum angle between the optical axis and a ray that can be incident on one end of the optical axis of the lens 111 used, which is a gradient index lens.

For example, when a rod lens array is applied to a reduction optical system to deepen the depth of field, the positions of the images formed on the sensor by two adjacent lenses are shifted from each other (images at the same position on the subject are formed at different positions on the sensor). As a result, different images are superimposed on the sensor, and a clear image of the subject is not formed on the sensor. On the other hand, in the reading device 100 of this embodiment, the image circles 121 on which the respective lenses 111 form images are arranged apart from each other. In other words, even when the reading device 100 is applied to a reduction optical system in which the lenses 111 form a reduced image of the subject on the sensor 102, it is possible to realize a reading device 100 with a deep depth of field and suppressed deterioration in image quality. The magnification M by the reduction optical system referred to here is:
0.05≦M≦0.80 ... (1)
It is desirable to satisfy the relationship. If it is below the lower limit of formula (1), the image obtained will be coarse, which is not preferable. The lower limit of this formula (1) may be 0.10 or more, and may further be 0.18 or more. On the other hand, if it is above the upper limit of formula (10), the depth of field will be shallow. Therefore, taking into consideration the depth of field, the upper limit of formula (1) may more preferably be 0.70 or less, or 0.40 or less.

In the configuration shown in Figures 1(a) to 2, the multiple rod lenses 110 included in each of the multiple lens blocks 101 are arranged in a direction intersecting the main scanning direction 151 (for example, the sub-scanning direction). Furthermore, one of the multiple rod lenses 110 included in each of the multiple lens blocks 101 functions as a used lens 111. Meanwhile, the rod lenses 110 other than the used lens 111 among the multiple rod lenses 110 included in each of the multiple lens blocks 101 function as unused lenses 112.

The unused lens 112 may be made not to form an image on the sensor 102 or to have difficulty in forming an image by performing appropriate processing on the rod lens 110. For example, the unused lens 112 can be made by shading at least a part of the light exit surface or light entrance surface of the rod lens 110. Also, for example, a light-shielding material may be applied to the light exit surface or light entrance surface of the rod lens 110 that becomes the unused lens 112, or a light-shielding tape may be attached. Also, the unused lens 112 may have a defect in a part compared to the used lens 111. For example, the light entrance surface of the rod lens 110 that becomes the unused lens 112 may be roughened in an uneven shape by polishing or the like. The light incident on the rod lens 110 is scattered at the light entrance surface and directed toward the side wall of the rod lens 110, making it difficult to form an image on the sensor 102. Also, the light exit surface or light entrance surface of the rod lens 110 may be tilted from the normal direction of the optical axis. If the light exit surface is tilted, the light exit surface of the rod lens 110 can be tilted so that the exiting light is not directed toward the sensor 102. Also, if the light incident surface of the rod lens 110 is tilted, the incident light is absorbed by the side walls of the rod lens 110, making it difficult to form an image on the sensor 102. Also, the light incident surface and light exit surface of the rod lens 110 that becomes the unused lens 112 do not have to be continuous.

1B, each lens block 101 may be formed by dividing a rod lens array including a plurality of rod lenses 110 arranged along a direction intersecting the optical axis. For example, the above-mentioned processing that makes it difficult to form an image is performed on some of the rod lenses 110 arranged in the rod lens array. Next, the rod lens array is cut at an appropriate position according to the position of the unprocessed used lens 111, and the formed plurality of lens blocks 101 are arranged at the corresponding positions of the sensor 102, thereby manufacturing the reading device 100. For example, even if the processing accuracy that makes it difficult to form an image of the rod lens 110 is low, the lens block 101 can be obtained by picking up a rod lens that functions as the used lens 111 from the processed rod lens array and cutting it to an appropriate length. The lens block 101 divided from the rod lens array has a configuration in which the rod lens 110 is arranged in a joint member 115 of an integral structure as shown in FIG. 1B. The joint member 115 joins the plurality of rod lenses 110 in each of the lens blocks 101. The coupling member 115 can be formed integrally with the rod lens 110, for example, from a resin material different from that of the rod lens 110. The coupling member 115 can also be colored an appropriate color, such as black.

Here, when the lens block 101 is assembled into the reading device 100 as shown in FIG. 1(a), the surface where light enters the rod lens 110 arranged in the lens block 101 is called the light entrance surface. In addition, the surface of the lens block 101 arranged on the sensor 102 side where light is emitted from the lens 111 used to the sensor 102 is called the light exit surface. In this case, the surface between the light entrance surface and the light exit surface of the lens block 101 is called the side wall. It is desirable that the side wall of the lens block 101 is parallel to the surface formed by the optical axis of the rod lens 110 and the two axes in the direction in which the rod lens 110 is arranged. It is also desirable that the side wall of the lens block 101 and the light entrance surface are perpendicular. Similarly, it is desirable that the side wall of the lens block 101 and the light exit surface are perpendicular.

In the reading device 100, it is possible to arrange multiple rod lenses at a predetermined interval without using the lens block 101. However, high precision is required to arrange rod lenses with a diameter of about φ1.0 mm at a predetermined interval with their optical axes aligned, which may lead to increased costs. On the other hand, in this embodiment, the lens block 101 can be formed by dividing the rod lens array. Furthermore, the reading device 100 includes a frame 201 having a housing section 202 that houses multiple lens blocks 101. Each lens block 101 is fixed to the frame 201, which fixes the position of the multiple lens blocks 101 relative to the sensor 102. Through these steps, the lenses 111 to be used, which are arranged in the lens block 101 with high precision, can be easily and highly accurately arranged in the predetermined position.

The used lenses 111 and unused lenses 112 arranged in the lens block 101 are rod lenses 110 made of the same material. Therefore, compared to a case where multiple rod lenses are arranged at a specified distance, even if there is an environmental change such as temperature, the rod lenses are less likely to be affected by tilting in an unintended direction due to differences in the coefficient of thermal expansion.

For example, as shown in FIG. 2, a plurality of storage sections 202 may be provided in the frame 201, and a plurality of lens blocks 101 may be arranged in each of the plurality of storage sections 202. In other words, the storage section 202 may be arranged independently for each lens block of the plurality of lens blocks 101. By inserting the lens block 101 into the storage section 202, the axis alignment of the lens 111 in use can be easily performed. In addition, the storage section 202 may be provided with abutment sections 203 for determining the position of each of the plurality of lens blocks 101 in the optical axis direction. By butting the lens block 101 against the buttment section 203, the distance between the lens 111 in use and the sensor 102 can be easily adjusted. In other words, at least a part of the coupling member 115 may be arranged in an area overlapping the buttment section 203 in the orthogonal projection in the optical axis direction of the rod lens 110. In the configuration shown in FIG. 2, an example is shown in which the abutment portion 203 is disposed between the lens block 101 and the sensor 102, but this is not limited thereto. Depending on the configuration of the reading device 100, for example, the abutment portion 203 may be disposed on the side of the lens block 101 opposite the sensor 102 (the side of the subject). The abutment portion 203 may also extend beyond the connecting member 115 to the position where the unused lens 112 is disposed. In other words, in the orthogonal projection in the optical axis direction of the rod lens 110, at least a portion of the unused lens 112 may be disposed in an area that overlaps with the abutment portion 203.

In the configuration shown in Figs. 1(a) and 2, the unused lens 112 may not be processed to make it difficult to form an image as described above. For example, if the image circle of the unused lens 112 adjacent to the used lens 111 is not placed on the sensor 102, the unused lens 112 may not be processed for light blocking. Also, for example, the image may become dark at the end of the image circle, and the effects of aberration may occur. Therefore, even if the image circle of the unused lens 112 overlaps with the image circle 121 of the used lens 111, it is possible to generate an image without using the signal output from the overlapping area. Furthermore, for example, as shown in Fig. 1(a), it is possible that the image circle 121 of the used lens 111 is larger than the sub-scanning direction of the sensor 102. In this case, it is possible that even if the image circle of the unused lens 112 overlaps with the image circle 121 of the used lens 111, the overlapping area is not on the sensor 102. Even in such a case, the rod lens array is cut to an appropriate size and stored as a lens block 101 in the storage section 202 of the frame 201 without performing any processing on the rod lens 110 that would make it difficult to form an image as described above. Through these steps, the optical system of the reading device 100 can be manufactured with high precision.

Figures 3 and 4 are diagrams showing modified examples of the reading device 100 described above. The multiple rod lenses 110 included in each of the multiple lens blocks 101 of the reading device 100 may be arranged along the main scanning direction 151. When this configuration is used, the unused lenses 112 may be lenses that have been treated to make it difficult for the rod lenses 110 to form an image as described above.

In the configuration shown in Figures 3 and 4, the number of lenses 111 used arranged in one lens block 101 is not limited to one. Depending on the size of the image circle 121 of the lens 111 used and the size of the lens block 101 in the main scanning direction 151, two or more rod lenses 110 may function as the lens 111 used. In this case, the image circles 121 of two adjacent lenses 111 used do not have to overlap. Also, if the ends of the image circles 121 of two adjacent lenses 111 used overlap, an image may be generated without using a signal output from the area where the image circles 121 of the sensor 102 overlap.

4, in the orthogonal projection in the optical axis direction of the rod lens 110, at least a part of the connecting member 115 is arranged in an area overlapping the abutment portion 203, so that the position in the optical axis direction of the lens block 101 can be determined. Also, as shown in FIG. 4, the abutment portion 203 may extend beyond the connecting member 115 to a position where the unused lens 112 is arranged. In other words, in the orthogonal projection in the optical axis direction of the rod lens 110, at least a part of the unused lens 112 may be arranged in an area overlapping the abutment portion 203. The unused lens 112 does not need to be imaged on the sensor 102. Therefore, the light entrance surface or light exit surface of the unused lens 112 may overlap the abutment portion 203. When this configuration is used, it is possible to make the abutment portion 203 larger. In other words, the stability of the lens block 101 when it is accommodated in the accommodation portion 202 of the frame 201 is improved, and it is possible to more easily improve the position and arrangement precision of the lens 111 in the optical axis direction. Even in the configuration shown in FIG. 2, an abutment portion 203 may be provided at the end of the accommodation portion 202 in the direction intersecting with the main scanning direction 151 (reference numeral 152) so as to overlap the lens 112 not in use in the orthogonal projection of the rod lens 110 in the optical axis direction.

In the configurations shown in Figures 1(a) to 4, the number of rod lenses 110 arranged in the lens block 101 is five, but is not limited to this. The number of rod lenses 110 may be four or less, or six or more. However, from the viewpoint of the number of steps for cutting the rod lens array and a size that is easy to handle, the number of rod lenses 110 arranged in the lens block 101 may be three or more, or even five or more. Also, in the configurations shown in Figures 1(a) and 2, if the number of rod lenses 110 arranged in the lens block 101 increases, the size of the lens block 101 in the sub-scanning direction intersecting with the main scanning direction 151 increases, and the number of unused lenses 112 increases relatively. Even in the configurations shown in Figures 3 and 4, if the number of rod lenses 110 arranged in the lens block 101 increases, the number of unused lenses 112 may increase relatively. In other words, since it is possible to obtain an appropriate number of lens blocks 101 from a rod lens array, and this is advantageous in terms of cost, the number of rod lenses 110 arranged in the lens block 101 may be 20 or less, or even 10 or less.

As described above, in this embodiment, a reading device 100 is obtained that suppresses degradation of image quality caused by overlapping images synthesized by multiple adjacent lenses when a rod lens array is used. Furthermore, the lens 111 used can be positioned with greater precision compared to when multiple rod lenses are positioned at a predetermined interval. Furthermore, a reading device 100 that is resistant to environmental changes can be realized.

Next, as application examples of the reading device 100 of this embodiment, an inspection device and a reading system incorporating the reading device 100 will be described. FIG. 5(a) is a diagram illustrating an inspection device 500 incorporating the reading device 100. FIG. 5(b) is a diagram illustrating a reading system 510 incorporating the reading device 100.

As shown in Figs. 5(a) and 5(b), the reading device 100 may acquire image information of a subject 550 (illuminated object) illuminated by an illumination device 131. In other words, the reading device 100 may further include an illumination device 131 for illuminating the subject 550.

When the subjects 550 have different sizes (heights) as shown in Figures 5(a) and 5(b), a deep depth of field is required for imaging. Therefore, the lenses 111 used to form an image on the sensor 102 are arranged at a distance from each other along the main scanning direction 151, and the reading device 100 has an optical system that can be used in a reduction optical system with a deep depth of field, making it possible to focus on subjects 550 of different heights.

The reading device 100 that can focus on subjects 550 of different sizes can be applied to an inspection device 500, for example, as shown in FIG. 5(a). The inspection device 500 may include the reading device 100 and an inspection unit 501 that inspects the state of the subject 550 using image information acquired by the reading device 100. Here, the state may be the pass/fail state of the subject 550 with respect to a judgment criterion previously set for a specific item (e.g., size, color, etc.), the state of the image quality of the printed matter, or the color development state of the printed matter. For example, the inspection unit 501 may inspect whether the subject 550 is in a predetermined state, or may perform an inspection to classify the subject 550 according to the size, color, etc. of the subject 550. The inspection device 500 may also be equipped with a transport device 502 for transporting the subject 550, as shown in FIG. 5(a). The inspection device 500 may be, for example, an inspection device that includes multiple lens blocks 101 and a line-shaped sensor 102 (for example, a line sensor extending in a direction intersecting the paper surface of FIG. 5(a)) and inspects an object 550 moving on a conveying device 502. The reading device 100 can focus on objects 550 of different sizes, which can improve the accuracy of the inspection by the inspection device 500.

The reading device 100 that can focus on subjects 550 of different sizes can be applied to a reading system 510, for example, as shown in FIG. 5(b). The reading system 510 includes the reading device 100 and a storage device 511 that stores data in a storage medium based on image information acquired by the reading device 100. The reading system 510 includes a copier, a printer, a data storage device that stores data in a hard disk or memory, and the like. The reading system 510 may image the subject 550 while moving it as in the above-mentioned inspection device 500, or may image the subject 550 by moving the reading device 100. Even if the subject 550 is uneven, as shown in FIG. 5(b), the lenses 111 used to form an image on the sensor 102 are arranged at a distance from each other along the main scanning direction 151, and the reading system 510 includes a reading device 100 equipped with an optical system that can be used in a reduced optical system with a deep depth of field, and can store an image focused on the surface of the subject 550.

The storage device 511 may store the image information read by the reading device 100 as electronic data in a storage medium such as a hard disk or memory. In this case, the storage device 511 may include a storage medium such as a hard disk or memory. The storage device 511 may also include a communication device that transfers the image information read by the reading device 100 to a storage medium such as a cloud storage device located outside the storage device 511.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the invention.

100: Reading device, 101: Lens block, 102: Sensor, 110: Rod lens, 111: Used lens, 112: Unused lens, 151: Scanning direction

Claims (17)

A sensor including a plurality of pixels arranged along a main scanning direction;
A reading device comprising:
Each of the lens blocks includes a plurality of rod lenses arranged along a direction intersecting an optical axis,
the plurality of rod lenses included in each of the plurality of lens blocks include a used lens that forms an image on the sensor and an unused lens that does not form an image on the sensor,
the lenses in each of the lens blocks are arranged along the main scanning direction,
The reading device according to claim 1, wherein the lens blocks are arranged at intervals from each other along the main scanning direction. A sensor including a plurality of pixels arranged along a main scanning direction;
A reading device comprising:
Each of the lens blocks includes a plurality of rod lenses arranged along a direction intersecting an optical axis,
the plurality of rod lenses included in each of the plurality of lens blocks include a used lens that guides light to the sensor and an unused lens that does not guide light to the sensor,
the lenses in each of the lens blocks are arranged along the main scanning direction,
The reading device according to claim 1, wherein the lens blocks are arranged at intervals from each other along the main scanning direction. The reading device according to claim 1 or 2, characterized in that one of the rod lenses included in each of the lens blocks functions as the lens in use. The reading device according to any one of claims 1 to 3, characterized in that the rod lenses included in each of the lens blocks are arranged in a direction intersecting the main scanning direction. The reading device according to any one of claims 1 to 3, characterized in that the rod lenses included in each of the lens blocks are arranged in the main scanning direction. The reading device according to any one of claims 1 to 5, characterized in that the number of the rod lenses included in each of the lens blocks is 3 or more and 20 or less. A reading device according to any one of claims 1 to 6, characterized in that the light entrance surface or light exit surface of the unused lens is light-shielded. The reading device according to any one of claims 1 to 7, characterized in that the unused lens has a defect in a portion compared to the used lens. The reading device according to any one of claims 1 to 8, characterized in that the rod lenses are gradient index lenses. a frame having a housing portion for housing the plurality of lens blocks;
10. The reading device according to claim 1, wherein the frame fixes the positions of the lens blocks relative to the sensor. A plurality of the storage sections are provided in the frame,
11. The reading device according to claim 10, wherein the lens blocks are arranged one by one in each of the plurality of storage sections. abutting portions for determining positions of the lens blocks in the optical axis direction are disposed in the housing portion;
12. The reading device according to claim 10, wherein at least a part of the unused lens is disposed in a region overlapping the abutment portion in an orthogonal projection in the optical axis direction. abutting portions for determining positions of the lens blocks in the optical axis direction are disposed in the housing portion;
each of the lens blocks includes a coupling member that couples the rod lenses together;
13. The reading device according to claim 10, wherein at least a part of the coupling member is disposed in a region overlapping the abutment portion in an orthogonal projection in the optical axis direction. The reading device according to any one of claims 1 to 13, characterized in that the lens used reduces and forms an image of the subject on the sensor. A reading device according to any one of claims 1 to 14,
an inspection unit that inspects a state of a subject using image information acquired by the reading device;
An inspection device comprising: A reading device according to any one of claims 1 to 14,
a storage device that stores the image information acquired by the reading device in a storage medium;
A reading system comprising: A sensor including a plurality of pixels arranged along a main scanning direction;
A method for manufacturing a reading device including a plurality of lens blocks, the method comprising the steps of:
A first step of dividing a rod lens array including a plurality of rod lenses arranged along a direction intersecting an optical axis into a plurality of lens blocks;
a second step of placing the lens blocks at corresponding positions on the sensor;
the rod lenses included in each of the plurality of lens blocks include a used lens that forms an image on the sensor and an unused lens that does not form an image on the sensor;
In the second step,
The lenses in use of the plurality of lens blocks are arranged along the main scanning direction,
The manufacturing method according to claim 1, wherein the lens blocks are arranged spaced apart from each other along the main scanning direction.