JP2023034993A - Rod lens array, sensor unit, reading device, inspection device, and recording system - Google Patents

Abstract

To provide a technique advantageous to apply a rod lens array to a reduction optical system.SOLUTION: A plurality of lens elements are aligned linearly in a normal direction of the optical axes of the lens elements in the rod lens array. The lens elements include first lens elements and second lens elements each obtained by chipping the shape of a first lens element.SELECTED DRAWING: Figure 1

Description

The present invention relates to rod lens arrays, sensor units, reading devices, inspection devices and recording systems.

Japanese Patent Application Laid-Open No. 2002-200000 discloses a lens array that forms an erect equal-magnification image, in which a large number of optical fibers having a refractive index distribution in a direction perpendicular to the optical axis are arranged in a straight line.

JP-A-6-342131

When a lens array such as that shown in Patent Document 1 is applied to a reduction optical system to increase the depth of field, the overlapping of images synthesized by a plurality of adjacent lenses becomes more likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide an advantageous technique for applying a rod lens array to a reduction optical system.

In view of the above problems, a rod lens array according to an embodiment of the present invention is a rod lens array in which a plurality of lens elements are arranged linearly in a direction normal to an optical axis of the plurality of lens elements, wherein the plurality of is characterized by including a first lens element and a second lens element in which a part of the shape of the first lens element is missing.

The above means provide an advantageous technique for applying a rod lens array to a reduction optical system.

1 is a perspective view showing a configuration example of a rod lens array according to this embodiment; FIG. FIG. 2 is a perspective view showing a configuration example of a sensor unit using the rod lens array of FIG. 1; FIG. 2 is a cross-sectional view showing a structural example of the rod lens array in FIG. 1; FIG. 2 is a cross-sectional view showing a structural example of the rod lens array in FIG. 1; FIG. 2 is a cross-sectional view showing a configuration example of the rod lens array in FIG. 1; FIG. 2 is a cross-sectional view showing a configuration example of the rod lens array in FIG. 1; FIG. 3 is a diagram showing a modification of the sensor unit of FIG. 2; FIG. 2 is a diagram showing a configuration example of a reading device, an inspection device, and a recording system in which the rod lens array of FIG. 1 is incorporated;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined arbitrarily. Also, the same or similar configurations are denoted by the same reference numerals, and redundant explanations are omitted.

A rod lens array according to an embodiment of the present disclosure will be described with reference to FIGS. 1(a) to 8(b). FIGS. 1A and 1B are perspective views showing configuration examples of the rod lens array 100 of this embodiment. A plurality of lens elements (rod lenses) 101 are arranged linearly (in a line) along a normal direction N (arrangement direction perpendicular to the optical axis) of the optical axis L of the plurality of lens elements (rod lenses) 101 to form a rod lens. An array 100 is constructed. The lens element 101 includes a lens element 101a and a lens element 101b having different shapes, as will be described later. Unless otherwise distinguished, the lens element 101 will be referred to as the lens element 101. a”, lens element 101 “b”, and so on. Further, the lens element 101 (rod lens) constituting the rod lens array 100 of the present embodiment is a lens element having a refractive index distribution in which both the surface on the incident side and the surface on the exit side are flat. be. Furthermore, this lens element 101 is a lens element that forms an erect image of an object on the image plane (forms an intermediate image).

A plurality of lens elements 101 are bonded by a bonding material 102 . In the configuration shown in FIGS. 1A and 1B, an example in which a plurality of lens elements 101 are arranged in a line is shown, but the configuration is not limited to this. Two or more rows of lens elements 101 may be arranged linearly along the normal direction N. Regardless of the number of rows of lens elements 101, the rod lens array 100 can have a shape in which the direction along the normal direction N shown in FIGS. 1(a) and 1(b) is the longitudinal direction.

As shown in FIGS. 1A and 1B, the plurality of lens elements 101 includes a lens element 101a and a lens element 101b having a partial defect in the shape of the lens element 101a. include. The lens element 101a exhibits a lens action by having a refractive index distribution concentrically in the normal direction of the optical axis L, for example. That is, in the lens element 101a, light enters from one end side surface and forms an image on the other end side (after being emitted from the other end side surface). Lens element 101b is basically the same lens element as lens element 101a. However, a part of the shape of the lens element 101a is damaged by the processing described later. As a result, in the lens element 101b, at least part of the light incident from the surface on the one end side is blocked, making it more difficult to form an image on the other end side than the lens element 101a. Here, almost all of the light incident from the surface on the one end side (incidence side) of the lens element 101b is attenuated by the wall surface (adhesive between the lens elements) of the lens element 101b, or incident on the adjacent lens element. It is not necessary to contribute to image formation by doing so.

FIG. 2 is a diagram showing a sensor unit 300 using the rod lens array 100. As shown in FIG. Sensor unit 300 includes rod lens array 100 shown in FIGS. and a frame 301 that houses the . The sensors 201 constitute the sensor assembly 200 by being arranged on the substrate 202, and the position of each sensor 201 can be fixed. Also, the frame 301 determines the positional relationship between the rod lens array 100 and the sensors 201 forming the sensor assembly 200 . Light is incident in the direction of the arrow shown in FIG. 2, passes through the rod lens array 100 and forms an image on the sensor 201 .

In the sensor unit 300, it may be necessary to increase the depth of field of the rod lens array 100, for example, when imaging an uneven subject. When a rod lens array 100 with a plurality of lens elements 101 arranged side by side is applied to a reduction optical system in order to deepen the depth of field, the influence of overlapping images synthesized by a plurality of adjacent lens elements 101 becomes large. . Therefore, in the present embodiment, some lens elements 101b out of the plurality of lens elements 101 do not form images, or the plurality of lens elements 101 do not form images by suppressing the lens elements 101b from forming images. suppresses the effect of overlapping images. For example, adjacent lens elements 101a may partially overlap each other in the range in which an image of a subject can be captured. On the other hand, the lens elements 101a and 101b are arranged so that the other lens element 101a does not form an image in the range where one lens element 101a forms an image on the sensor 201. FIG. With such a configuration of the rod lens array 100, it is possible to image the entire subject while suppressing the influence of image overlap. Here, the image formation magnification of the reduction optical system of the present embodiment is about 0.3 times, but is not limited thereto, and the image formation magnification is 0.05 times or more and 0.9 times or less (more preferably 0.15 times). times or more and 0.35 times or less).

For example, as shown in FIG. 2, two or more lens elements 101b may be arranged between two lens elements 101a. The number of lens elements 101b arranged between the two lens elements 101a may be appropriately designed according to the take-in angle of the lens elements 101, the arrangement pitch of the photoelectric conversion elements arranged in the sensor 201, and the like. The number of lens elements 101b arranged between two lens elements 101a may be the same between any two lens elements 101a, or may be partially different depending on the arrangement of the sensor 201 and the like. good too. For example, when there is a seam of the sensor 201 at a position corresponding to between the two lens elements 101a, the distance between the two lens elements 101a is higher than when there is no seam of the sensor 201 at a position corresponding between the two lens elements 101a. The number of lens elements 101b in between can be large.

Returning to FIGS. 1(a) and 1(b), the lens element 101b, which has a partial defect relative to the shape of the lens element 101a, will be further described. As shown in FIG. 1A, a slit (hole) 111 may be provided in the lens element 101b so that the lens element 101b is discontinuous between one end and the other end. For example, by providing a slit as shown in FIG. 1A, it becomes difficult for the lens element 101b to form an image of the subject (form an image of the subject). On the other hand, the slit 111 is not provided at the position corresponding to the lens element 101a, and the lens element 101a is continuous between one end and the other end, so that it is possible to form an image of the subject (form an image of the subject). be.

Further, as shown in FIG. 1B, the surface of the lens element 101b on the one end side may be rougher than the surface on the one end side and the surface on the other end side of the lens element 101a. For example, the lens element 101b can be obtained by roughening the surface of one end side of the lens element 101a using a file or the like. The roughened surface on the one end side can be arranged on the light incident side of the sensor unit 300, as shown in FIG. By roughening the surface of one end of the lens element 101b, incident light is refracted in various directions, making it difficult to form an image. For example, when incident light is refracted at one end surface of the lens element 101 b and enters the bonding material 102 from the lens element 101 b , the light can be absorbed in the bonding material 102 . Thus, the binding material 102 may function as a light shielding material. The bonding material 102 may be an adhesive or the like for bonding the plurality of lens elements 101 together. By adding black paint or the like to this adhesive, the light is absorbed by the bonding material 102, making it difficult for the light to pass through the lens element 101b. Further, for example, even if the coupling material 102 is transparent, the light incident on the coupling material 102 from the lens element 101b travels to a position far away from the original coupling position, and thus it becomes difficult to contribute to image formation. Also, for example, both ends of the lens element 101b may be roughened. Moreover, the slit 111 shown in FIG. 1(a) and the roughening of the end portion shown in FIG. 1(b) may be combined.

Further, for example, as shown in FIGS. 3(a) and 3(b), the shape of the surface on the one end side of the lens element 101b may be conical. For example, a cutting tool 151 such as a drill may be provided at a position corresponding to each of the lens elements 101b, and the lens elements 101b may be formed by cutting. The light incident from the object to be illuminated 411 illuminated by the illumination device 401 passes through the lens element 101a (the lens action is not depicted in FIG. 3(b); the same applies to the following figures). On the other hand, since the surface of one end of the lens element 101b is conical, the light incident on the lens element 101b is projected in the direction of the interface between the lens element 101b and the binder 102 as shown in FIG. 3(b). and becomes difficult to pass through the lens element 101b. That is, it becomes difficult for the lens element 101b to form an image.

Next, the angle of the surface on the one end side of the lens element 101b will be described. The inclination θ with respect to the normal direction (for example, the normal direction N) of the surface on the one end side of the lens element 101b shown in FIG. 3B may be greater than or equal to the take-in angle of the lens element 101a. Here, the take-in angle is the maximum angle formed by the light beam that can form an image on the lens element 101 and the optical axis, among the light beams incident on the position where the light incident surface of the lens element 101a and the optical axis intersect. It's about the angle. Also, the acceptance angle is sometimes referred to as the aperture angle. This take-in angle (aperture angle) is 9 degrees in this embodiment, but may be 12 degrees, preferably 3 degrees or more and 21 degrees or less (4.8 degrees or more and 12.3 degrees or less). By setting this inclination θ to be 1.5 times or more the take-in angle, almost all of the light incident on the lens element 101b is shielded from the sensor 201 (prevented from entering the sensor 201). can be done. Further, the inclination θ of the surface on the one end side of the lens element 101b with respect to the normal direction may be twice or more (more preferably three times or more) the take-in angle of the lens element 101a. Also, it is desirable that this inclination θ is six times or less (more preferably five times or less) the take-in angle. The lens elements 101 used in the rod lens array 100 may have an acceptance angle of approximately 9° as described above. Therefore, the inclination θ of the surface on the one end side of the lens element 101b with respect to the normal direction may be 13.5° or more. Furthermore, considering a margin, the inclination θ of one end of the lens element 101b with respect to the normal direction N may be 18° or more (preferably 27° or more). FIGS. 3(a) and 3(b) show the case where machining is performed with a cutting tool 151 having a tip inclined at about 90°, such as a drill, and the inclination θ is about 45°.

In the configuration shown in FIGS. 3A and 3B, conical concave portions are formed so as to correspond to the respective lens elements 101b, but the configuration is not limited to this. For example, as shown in FIGS. 4(a) and 4(b), one lens element 101b may have a plurality of conical depressions, or two or more lens elements 101b may have one conical depression. A concave portion may be formed.

Further, for example, as shown in FIGS. 5A to 5C, the one end surface of the lens element 101b may be inclined with respect to the one end surface of the lens element 101a. Here, FIGS. 3(a) to 4(b) show cross sections in which a plurality of lens elements 101 are arranged in the horizontal direction of the drawing, but FIGS. A cross-section is shown with a plurality of lens elements 101 aligned in a direction.

As shown in FIG. 5A, light incident on the lens element 101a is transmitted through the lens element 101a. On the other hand, the lens element 101b is obliquely cut using a cutting tool 151 such as an end mill. Therefore, the light incident on the lens element 101b is refracted in the direction of the interface between the lens element 101b and the binder 102 as shown in FIG. 5B, making it difficult for the light to pass through the lens element 101b. That is, it becomes difficult for the lens element 101b to form an image. As noted above, the binder 102 may function as a light shield. Moreover, the lens element 101b is not only inclined in one direction as shown in FIG. may be tilted diagonally in both directions intersecting with . In the same manner as described above, the inclination θ of one end of the lens element 101b shown in FIGS. . Further, the inclination θ of one end of the lens element 101b with respect to the normal direction of the optical axis may be three times or more the take-in angle of the lens element 101a. Further, the inclination θ of one end of the lens element 101b with respect to the normal direction N may be 9° or more, or may be 27° or more.

In this way, some lens elements (lens element 101b) out of the plurality of lens elements 101 are processed so as to make it difficult to form an image. This makes it possible to apply the rod lens array 100 to a reduction optical system and increase the depth of field while suppressing deterioration in image quality due to overlapping of images synthesized by a plurality of adjacent lenses. .

In the sensor unit 300, instead of using the rod lens array 100 having the lens elements 101a and 101b, it is conceivable to arrange a plurality of lens elements at predetermined intervals. However, in order to align the optical axes of the lens elements with a diameter of about 1.0 mm at predetermined intervals in accordance with the positions of the photoelectric conversion elements arranged in the sensor 201, high accuracy is required, which causes an increase in cost. can also be On the other hand, in the present embodiment, a rod lens array that is generally used for the sensor unit 300 and the like is processed. can be equivalent to In addition, the rod lens array 100 is a general-purpose rod lens array, which is relatively different from a general-purpose rod lens array by forming the above-described slits 111, roughening the surface on one end side of the lens element 101a, forming a conical concave portion, and tilting the surface. Since it can be manufactured by adding easy processing, the impact on cost can be suppressed.

Further, in order to shield some of the lens elements 101 from light, it is conceivable to dispose a light shielding member on some of the plurality of lens elements 101 arranged in a general-purpose rod lens array. For example, it is conceivable to dispose a partially opened metal plate or resin plate as the light shielding member so as to cover the rod lens array. However, there is a high possibility that the light shielding member has a coefficient of linear expansion different from that of the rod lens array due to differences in structure and the like. Therefore, it is difficult to align the light shielding member with respect to each lens element 101 of the rod lens array 100 due to changes in the environment such as temperature and the lengthening of the sensor unit 300 . On the other hand, in the present embodiment, since the lens elements 101 themselves arranged in the rod lens array 100 are processed, it is possible to easily cope with environmental changes and lengthening of the sensor unit 300 .

Next, a modified example of rod lens array 100 will be described with reference to FIG. A light shielding member 112 may cover the surface of one end of the lens element 101b, which has a defect in the shape of the lens element 101a, so that the lens element 101b is difficult to form an image. For example, as shown in FIG. 6, colored resin such as black may be embedded in the portion where the surface of the lens element 101b on the one end side is damaged. Further, for example, a metal film may be formed as the light shielding member 112 on the portion where the surface of the lens element 101b on the one end side is damaged. The light shielding member 112 does not need to cover the entire end surface of the lens element 101b, and may cover only a portion of the end surface. By disposing the light shielding member 112, it becomes more difficult for light to pass through the lens element 101b.

7(a) and 7(b) are diagrams showing modifications of the sensor unit 300 shown in FIG. Similar to the sensor unit 300 shown in FIG. 2, the sensor unit 300 shown in FIG. 7A includes a rod lens array 100, a sensor 201 for receiving light emitted from the rod lens array 100, and a frame 301 that houses the lens array 100 and the sensor 201 . In the configuration shown in FIGS. 7(a) and 7(b), the surface on one end side of the lens element 101b arranged in the rod lens array 100 is, as shown in FIGS. 3(a) to 5(c), For example, it is cut using a cutting tool 151 to form a recess. Further, similarly to the configuration shown in FIG. are arranged to face the

At this time, as shown in FIGS. 7( a ) and 7 ( b ), one end side of the lens element 101 b having the concave portion may be used for alignment between the rod lens array 100 and the frame 301 . 7(a) is an exploded perspective view of the sensor unit 300, and FIG. 7(b) is a sectional view of the portion 160 of FIG. 7(a). As described above, the surface on the one end side of the lens element 101b is provided with a concave portion. A reference pin 302 is arranged on the frame 301 so as to fit into the concave portion of the lens element 101b. When the rod lens array 100 is incorporated into the frame 301, the alignment of the rod lens array 100 with respect to the frame 301 can be facilitated by fitting the concave portion of the lens element 101b with the reference pin 302. FIG.

As shown in FIG. 7B, the concave portion into which the reference pin 302 is inserted and the concave portion into which the reference pin 302 is not inserted among the plurality of lens elements 101b may have different shapes. Further, the concave portion into which the reference pin 302 is inserted and the concave portion into which the reference pin 302 is not inserted among the plurality of lens elements 101b may have the same shape. Alignment between the rod lens array 100 and the frame 301 can be made easier if the recess into which the reference pin 302 is inserted and the recess into which the reference pin 302 is not inserted have different shapes. Even when the slit 111 is formed in the rod lens array 100, a concave portion having an appropriate shape may be formed on the surface of one end of the lens element 101b so that the reference pin 302 is fitted.

Next, as an application example of the rod lens array 100 of this embodiment, a reading device, an inspection device, and a recording system including the sensor unit 300 incorporating the rod lens array 100 will be described. FIG. 8A is a diagram illustrating a reading device 400 including a sensor unit 300 incorporating a rod lens array 100 and an inspection device 500 including the reading device 400. FIG. FIG. 8B is a diagram illustrating a reading device 400 including the sensor unit 300 incorporating the rod lens array 100 and a recording system 510 including the reading device 400. FIG.

As shown in FIGS. 8A and 8B, the reading device 400 includes an illumination device 401 and an image sensor for acquiring image information of an object to be illuminated 411 (subject) illuminated by the illumination device 401. 402 and. The image sensor 402 is provided with a sensor unit 300 incorporating the rod lens array 100 described above. As shown in FIGS. 1(b) and 3(a) to 5(c), when the surface on one end side of the lens element 101b is processed, the lens element 101a has a defect in its shape. A surface on one end side of the element 101b can be arranged to face the object 411 to be illuminated.

When the object 411 to be illuminated has a difference in size (height) as shown in FIGS. 8A and 8B, a deep depth of field is required for imaging. Therefore, by providing the rod lens array 100 with the above-described configuration, the reading device 400 including the sensor unit 300 incorporating the rod lens array 100 can focus on illuminated objects 411 having different sizes. become.

A reading device 400 that can focus on illuminated objects 411 of different sizes can be applied to, for example, an inspection device 500 as shown in FIG. 8(a). The inspection apparatus 500 can include a reader 400 and a determiner 501 that determines the quality of an object to be illuminated 411 using image information acquired by the reader 400 . Moreover, the inspection apparatus 500 may include a transport device 502 for transporting the object to be illuminated 411 as shown in FIG. 8(a). The inspection apparatus 500 includes, for example, a sensor unit 300 (line sensor unit) having a linear rod lens array 100 and a sensor 201, and inspects an illuminated object 411 moving on a conveying apparatus 502. good. The reading device 400 that can focus on illuminated objects 411 of different sizes makes it possible to improve the accuracy of inspection by the inspection device 500 .

Further, the reading device 400 that can focus on illuminated objects 411 of different sizes can be applied to, for example, a recording system 510 as shown in FIG. 8B. The recording system 510 includes a reading device 400 and a recording device 511 that prints on a recording medium based on image information acquired by the reading device 400 . The recording system 510 includes a copying machine, a printer, a data recording device that records data in a hard disk or memory, and the like. FIG. 8B shows an example of printing on a paper medium such as a copier or printer in the printing system 510 . The recording system 510 may capture an image while moving the object to be illuminated 411 as in the inspection device 500 described above, or may capture an image of the object to be illuminated 411 by moving the reading device 400 . Even if the object to be illuminated 411 is uneven as shown in FIG. A focused image can be recorded on the surface of the object 411 to be illuminated.

The recording device 511 can record an image including characters on a recording medium 513 (for example, paper) by any method such as an inkjet method or an electrophotographic method. In this case, recording system 510 may include transport device 512 . As the conveying device 512, a conveying roller that conveys the recording medium from upstream to downstream can be used. In one embodiment, the recording system 510 can perform copy processing, and in this case, the recording device 511 records image information read by the reading device 400 as an image on a recording medium. Also, in one embodiment, the recording system 510 can provide feedback control. For example, the reading device 400 can read image information from a recording medium 513 after recording has been performed by the recording device 511 and transmit the read data to the recording device 511 . Based on this read data, the recording device 511 can confirm the recording state on the recording medium, and can control the recording parameters for the next recording.

Also, the recording system 510 is not limited to a device that records on the recording medium 513 such as paper, as described above. The recording device 511 may record the image information read by the reading device 400 as electronic data in a recording medium such as a hard disk or memory. In this case, the recording device 511 may include a recording medium such as a hard disk or memory. In this case, the transport device 512 may not be arranged in the recording system 510 .

The invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the invention.

100: rod lens array, 101a, 101b: lens elements

Claims (15)

A rod lens array in which a plurality of lens elements are arranged linearly in the normal direction of the optical axis of the plurality of lens elements,
A rod lens array, wherein the plurality of lens elements includes a first lens element and a second lens element having a partially defective shape with respect to the shape of the first lens element. the plurality of lens elements includes a plurality of the first lens elements and a plurality of the second lens elements;
2. The rod lens array according to claim 1, wherein two or more of the second lens elements are arranged between two of the first lens elements. 3. The rod lens array according to claim 1, wherein the surface of the second lens element on the one end side is rougher than the surface of the first lens element on the one end side. 4. The rod lens array according to claim 1, wherein the surface of the second lens element on the one end side is inclined with respect to the surface of the first lens element on the one end side. 5. The rod lens array according to any one of claims 1 to 4, wherein the shape of the surface on the one end side of the second lens element is conical. 6. The rod lens array according to claim 4, wherein the inclination of the one end side surface of the second lens element with respect to the normal direction is greater than or equal to the take-in angle of the first lens element. 6. The rod lens array according to claim 4, wherein the inclination of the one end side surface of the second lens element with respect to the normal direction is 9 degrees or more. 8. The lens according to any one of claims 3 to 7, wherein a surface on one end side of the second lens element, which has a defect in the shape of the first lens element, is covered with a light shielding member. Rod lens array as described. 9. A rod lens array as claimed in any preceding claim, wherein the second lens element is discontinuous between one end and the other end. a rod lens array according to any one of claims 1 to 9;
a sensor for receiving light emitted from the rod lens array;
a frame housing the rod lens array and the sensor;
A sensor unit comprising: The surface of the second lens element opposite to the surface of the second lens element having a defect in the shape of the first lens element faces the sensor. Item 11. The sensor unit according to item 10. a lighting device;
and an image sensor for acquiring image information of an object to be illuminated illuminated by the illumination device,
12. A reading device, wherein the image sensor includes the sensor unit according to claim 10 or 11. 13. The method according to claim 12, wherein a surface on one end side of the second lens element, which has a defect in the shape of the first lens element, is arranged so as to face the object to be illuminated. reader. a reader according to claim 12 or 13;
a determiner that determines whether the object to be illuminated is good or bad using the image information acquired by the reading device;
An inspection device comprising: a reader according to claim 12 or 13;
a recording device for recording image information acquired by the reading device on a recording medium;
A recording system comprising:

Images