Patent Application
20250189456
The present invention relates to an optical unit for guiding light to a light receiving element provided along a main scanning direction, and an optical line sensor including the optical unit.
For example, there is known an optical line sensor that irradiates an object such as a printed matter or a functional film with light and receives transmitted light or reflected light from the object by a light receiving element. Examples of this type of optical line sensor include a line scan camera and a contact image sensor (CIS).
The optical line sensor includes an image forming lens for forming an image of transmitted light or reflected light from an object on a light receiving element. A rod lens array, which is an example of an image forming lens, is configured in an elongated shape along a main scanning direction with a plurality of rod lenses as image forming elements arranged in the main scanning direction (see, for example, Patent Document 1 below).
Patent Document 1: JP 5596803 B2
In the optical line sensor disclosed in Patent Document 1, a frame body that accommodates each component of the optical line sensor is divided into two frames. Further, a rod lens array is fixed to one of the frames by using an adhesive, and the other one of the frames is arranged so as not to contact the rod lens array. This is a configuration for preventing influence on the rod lens array in a case where the two frames are shifted and coupled, but on the other hand, this causes another problem.
First, in a configuration in which the rod lens array is fixed only to one frame, firm fixing is not guaranteed, and thus, reliability of fixation of the rod lens array is low. Further, in a case where the rod lens array is fixed using an adhesive, work takes time and effort. Furthermore, since a shape of a frame body is complicated because, for example, a filling groove to be filled with an adhesive needs to be formed in one frame, manufacturing cost is high.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical unit having high reliability for fixation of an image forming lens, and an optical line sensor including the optical unit.
Further, an object of the present invention is to provide an optical unit that facilitates work of fixing an image forming lens and an optical line sensor including the optical unit.
Furthermore, an object of the present invention is to provide an optical unit for which manufacturing cost can be reduced and an optical line sensor including the optical unit.
According to such a configuration, since the image forming lens having an elongated shape along the main scanning direction is sandwiched in a state of being pressed by a pair of the holding members arranged along the main scanning direction, firm fixation is guaranteed, and reliability of fixation of the image forming lens is improved.
Further, since firm fixation of the image forming lens is guaranteed without use of an adhesive, work of fixing the image forming lens is easier than a case of using an adhesive.
Furthermore, since it is not necessary to employ a complicated configuration for fixing the image forming lens, manufacturing cost can be reduced.
According to such a configuration, since the light receiving substrate is fixed so as to extend to a pair of the holding members to which the image forming lens is firmly fixed, positional accuracy between the light receiving element mounted on the light receiving substrate and the image forming lens can be accurately maintained.
According to such a configuration, since a pair of the holding members can be formed by use of an inexpensive material having an L-shaped cross section, manufacturing cost can be reduced.
According to such a configuration, in a state where the image forming lens is sandwiched between a pair of the holding members, a pair of the holding members are arranged to have a T-shaped cross section, and an empty space can be formed on the side of each of the first plate portions of a pair of the holding members facing each other. Since other members such as a light source unit can be arranged in this empty space, space saving can be improved.
According to such a configuration, a pair of the holding members are caused to abut on and accurately connected to each other at a portion other than the elastically deformable portion, and the elastically deformable portion is elastically deformed to abut on the image forming lens, so that the image forming lens can be pressed and firmly fixed.
According to such a configuration, the elastically deformable portion can be formed with a simple configuration in which only the groove extending in the main scanning direction is formed, and thus, manufacturing cost can be reduced.
According to such a configuration, the image forming lens can be uniformly pressed and firmly fixed.
According to such a configuration, the image forming lens can be uniformly pressed and firmly fixed.
According to the present invention, it is possible to improve reliability for fixation of an image forming lens. Further, according to the present invention, it is easy to perform work of fixing an image forming lens. Furthermore, according to the present invention, manufacturing cost can be reduced.
The optical line sensor 1 includes an illumination unit 2 and a light receiving unit 3. In the present embodiment, the optical line sensor 1 includes two illumination units 2 and one light receiving unit 3. However, the number of the illumination units 2 and the light receiving units 3 is not limited to the number in the present embodiment.
The illumination unit 2 has an elongated shape along the X direction, and irradiates the object S with light along an irradiation optical axis A1 orthogonal to the X direction. Light emitted from the illumination unit 2 is reflected by the object S, and the reflected light is directed to the light receiving unit 3 along a light receiving optical axis A2. The illumination unit 2 constitutes a light source unit that irradiates the object S conveyed in the Y direction with light.
The light receiving unit 3 has an elongated shape along the X direction, and receives reflected light from the object S along the light receiving optical axis A2 orthogonal to the X direction. The light receiving unit 3 includes a plurality of light receiving elements 32 (described later), and photoelectrically converts reflected light received by each of the light receiving elements 32 to obtain an electric signal corresponding to an amount of received light. The light receiving unit 3 constitutes an optical unit for guiding light to the light receiving element 32 provided along the X direction.
The illumination unit 2 and the light receiving unit 3 are connected by a pair of connection members 4 at both end portions in the X direction. By the above, a positional relationship between the illumination unit 2 and the light receiving unit 3 is fixed, and the integrated optical line sensor 1 is constituted. The optical line sensor 1 is fixed at a predetermined angle with respect to a conveyance direction (Y direction) of the object S. In a state in which the optical line sensor 1 is fixed, the light receiving optical axis A2 is, for example, perpendicular to the object S and parallel to the Z direction. On the other hand, the irradiation optical axis A1 is inclined with respect to, for example, a direction (Z direction) perpendicular to the object S.
The illumination unit 2 includes a plurality of LEDs 21, an LED substrate 22, a condenser lens 23, and an illumination housing 24. A plurality of the LEDs 21 are an example of a light source, and emit light along the irradiation optical axis A1 parallel to each other. The LED substrate 22 has an elongated shape along the X direction, and a plurality of the LEDs 21 are mounted in an array in the X direction and energized. That is, the LED substrate 22 constitutes an irradiation substrate on which a light source is mounted and energized. The condenser lens 23 condenses and emits light incident from each of the LEDs 21. The illumination housing 24 has an elongated shape along the X direction, and integrally holds the LED substrate 22 and the condenser lens 23 at a predetermined position. The irradiation optical axis A1 is an optical axis of the LED 21 or the condenser lens 23.
The light receiving unit 3 includes an image forming lens 31, a plurality of the light receiving elements 32, a light receiving substrate 33, and a light receiving housing 34. The image forming lens 31 transmits light from the object S along the light receiving optical axis A2 to form an image on a plurality of the light receiving elements 32. A plurality of the light receiving elements 32 receive light by which an image is formed by the image forming lens 31, photoelectrically converts the light, and outputs an electric signal. The light receiving substrate 33 has an elongated shape along the X direction, and a plurality of the light receiving elements 32 are mounted side by side in the X direction and energized. The light receiving housing 34 has an elongated shape along the X direction, and integrally holds the image forming lens 31 and the light receiving substrate 33 at a predetermined position. The light receiving optical axis A2 is an optical axis of a plurality of image forming elements constituting the image forming lens 31, and a line obtained by focusing each image forming clement on the light receiving optical axis A2 is the reading line L.
The image forming lens 31 is, for example, a rod lens array. In this case, the image forming lens 31 is constituted in an array shape having an elongated shape along the X direction with a plurality of rod lenses as image forming elements arranged in the X direction. The rod lens is an example of an image forming clement of an upright equal magnification image forming type. A typical commercially available rod lens array is SELFOC lens array (registered trademark: NIPPON SHEET GLASS CO., LTD.), and in this case, an operation distance (distance from a lens end surface to a focal point) is limited to 20 mm or less. In a case where the operation distance is 20 mm or less, there is a high probability that the object S comes into contact with a rod lens array and is damaged when being conveyed. Therefore, it is more preferable to use a rod lens array having the operation distance of 30 mm or more. For this purpose, the operation distance is preferably adjusted to 30 mm or more by independently creating a rod lens array having the operation distance of 30 mm or more or appropriately changing a pitch in an optical axis direction of a commercially available rod lens array (operation distance of 20 mm or less). Further, without limitation to a rod lens, a spherical lens, an aspherical lens, a lens group obtained by combining a plurality of these lenses, and the like may be arranged in an array in the X direction to constitute the image forming lens 31.
In the present embodiment, reflected light from the object S of light emitted from the illumination unit 2 is transmitted through the image forming lens 31 so that an image is formed on the light receiving element 32. However, the present invention is not limited to such a configuration, and in a case of a configuration where the illumination unit 2 is arranged on the opposite side of the light receiving unit 3 side with respect to the object S, transmitted light in the object S of light emitted from the illumination unit 2 may be transmitted through the image forming lens 31 so that an image is formed on the light receiving element 32.
The light receiving housing 34 of the light receiving unit 3 includes a pair of holding members (a first holding member 35 and a second holding member 36) that hold the image forming lens 31. The first holding member 35 and the second holding member 36 are arranged along the X direction. That is, the first holding member 35 and the second holding member 36 extend in parallel to the image forming lens 31.
The first holding member 35 has a configuration in which a first plate portion 351 and a second plate portion 352 are connected. The first plate portion 351 of the first holding member 35 is a plate-like member extending in the X direction along a plane (vertical plane) parallel to the X direction and the Z direction. The first plate portion 351 has a facing surface 353 facing the second holding member 36. The facing surface 353 is parallel to the X direction and the Z direction and orthogonal to the Y direction.
The second plate portion 352 of the first holding member 35 is a plate-like member extending in the X direction along a plane (horizontal plane) parallel to the X direction and the Y direction. The second plate portion 352 has a fixing surface 354 to which the light receiving substrate 33 is fixed. The fixing surface 354 is parallel to the X direction and the Y direction and orthogonal to the Z direction.
The first holding member 35 is formed to have an L-shaped cross section as the first plate portion 351 and the second plate portion 352 are connected. Specifically, as an end portion in the Z direction of the first plate portion 351 and an end portion in the Y direction of the second plate portion 352 are connected, the first plate portion 351 and the second plate portion 352 are connected so as to be orthogonal to each other. The first plate portion 351 and the second plate portion 352 may have a configuration in which a separate member is coupled or may have a configuration in which they are integrally formed.
The second holding member 36 has a configuration in which a first plate portion 361 and a second plate portion 362 are connected. The first plate portion 361 of the second holding member 36 is a plate-like member extending in the X direction along a plane (vertical plane) parallel to the X direction and the Z direction. The first plate portion 361 has a facing surface 363 facing the first holding member 35. The facing surface 363 is parallel to the X direction and the Z direction and orthogonal to the Y direction.
The second plate portion 362 of the second holding member 36 is a plate-like member extending in the X direction along a plane (horizontal plane) parallel to the X direction and the Y direction. The second plate portion 362 has a fixing surface 364 to which the light receiving substrate 33 is fixed. The fixing surface 364 is parallel to the X direction and the Y direction and orthogonal to the Z direction.
The second holding member 36 is formed to have an L-shaped cross section as the first plate portion 361 and the second plate portion 362 are connected. Specifically, as an end portion in the Z direction of the first plate portion 361 and an end portion in the Y direction of the second plate portion 362 are connected, the first plate portion 361 and the second plate portion 362 are connected so as to be orthogonal to each other. The first plate portion 361 and the second plate portion 362 may have a configuration in which a separate member is coupled or may have a configuration in which they are integrally formed.
On the facing surface 353 of the first holding member 35, a step surface 355 extending along the X direction is formed at an end portion (lower end portion) on the opposite side to the second plate portion 352 side in the Z direction. The step surface 355 faces the image forming lens 31. However, a surface on the light receiving element 32 side of the image forming lens 31 does not abut on the step surface 355.
On the facing surface 363 of the second holding member 36, a step surface 365 extending along the X direction is formed at an end portion (lower end portion) on the opposite side to the second plate portion 362 side in the Z direction. The step surface 365 faces the image forming lens 31 and has a shape corresponding to a shape of a corner portion facing the step surface 365 of the image forming lens 31. A surface on the light receiving element 32 side of the image forming lens 31 abuts on the step surface 365.
As described above, the step surface 365 of the second holding member 36 abuts on a surface on the light receiving element 32 side of the image forming lens 31, and functions as a reference surface for positioning the image forming lens 31 in the Z direction. For this reason, a distance between an upper surface (surface abutting on a surface on the light receiving element 32 side of the image forming lens 31) of the step surface 365 and the fixing surface 364 requires high dimensional accuracy. This dimensional accuracy is preferably an error of ±0.05 mm or less.
Further, a surface (surface orthogonal to the Y direction) facing a side surface of the image forming lens 31 of the step surface 365 of the second holding member 36 also functions as a reference surface for positioning the image forming lens 31 in the Y direction. Therefore, a surface orthogonal to the Y direction in the step surface 365 needs to be flat with high dimensional accuracy, and degree of flatness (tolerance) of the surface is preferably 0.1 mm or less.
On the other hand, the step surface 355 of the first holding member 35, which does not abut on a surface on the light receiving element 32 side of the image forming lens 31 as described above, docs not require dimensional accuracy such as that of the step surface 365 of the second holding member 36 from the viewpoint of positioning the image forming lens 31 in the Z direction. Similarly, a surface (surface orthogonal to the Y direction) facing a side surface of the image forming lens 31 of the step surface 355 of the first holding member 35 does not need to be flat with high dimensional accuracy. Therefore, manufacturing cost of the first holding member 35 can be reduced.
Note that the step surface 355 of the first holding member 35 and the step surface 365 of the second holding member 36 both function as a light shielding surface that does not transmit and blocks unnecessary light.
The first holding member 35 and the second holding member 36 are connected to each other using a connecting tool 37 such as a screw. In the present embodiment, both end portions in the X direction of the first holding member 35 and both end portions in the X direction of the second holding member 36 are connected to each other using the connecting tool 37. Specifically, the first holding member 35 and the second holding member 36 are connected as the connecting tool 37 inserted through a through hole formed at both end portions of the first plate portion 361 of the first holding member 35 is fastened to the second holding member 36.
At this time, the image forming lens 31 is arranged between the step surface 355 of the first holding member 35 and the step surface 365 of the second holding member 36, and both end surfaces in the Y direction of the image forming lens 31 are pressed by the step surface 355 and the step surface 365 as the first holding member 35 and the second holding member 36 are connected using the connecting tool 37. By the above, the image forming lens 31 is sandwiched between the first holding member 35 and the second holding member 36 in a state where both end surfaces in the Y direction are pressed by the step surface 355 and the step surface 365. That is, the image forming lens 31 is held only by pressing force of the first holding member 35 and the second holding member 36 without using an adhesive.
As described above, in a state where the first holding member 35 and the second holding member 36 sandwich the image forming lens 31, the first plate portion 351 of the first holding member 35 and the first plate portion 361 of the second holding member 36 face each other to sandwich the image forming lens 31. Further, the second plate portion 352 of the first holding member 35 and the second plate portion 362 of the second holding member 36 are located on the same plane in a plane (horizontal plane) parallel to the X direction and the Y direction.
By the above, as illustrated in
As illustrated in
The light receiving substrate 33 is fixed to the first holding member 35 and the second holding member 36 using a fixing tool 38 such as a screw. Specifically, one end portion in the Y direction of the light receiving substrate 33 faces the fixing surface 354 of the first holding member 35, and another end portion in the Y direction of the light receiving substrate 33 faces the fixing surface 364 of the second holding member 36. In the present embodiment, the light receiving substrate 33 is fixed to the first holding member 35 and the second holding member 36 as the fixing tool 38 inserted into a through hole formed at at least four corners of the light receiving substrate 33 is fastened to each of the first holding member 35 and the second holding member 36. By the above, the light receiving substrate 33 is fixed in a state of extending to the first holding member 35 and the second holding member 36.
On the fixing surface 354 of the first holding member 35, a step surface 356 is formed in a part of a region facing the light receiving substrate 33. On the fixing surface 364 of the second holding member 36, a step surface 366 is formed in a part of a region facing the light receiving substrate 33. In a state where the first holding member 35 and the second holding member 36 are connected, a space C communicating with the space B is formed by the step surface 356 and the step surface 366. The space C functions as a region for accommodating a component mounted on the light receiving substrate 33.
Specifically, a thickness further on the both end portion side than the boundary line D of the first plate portion 361 of the second holding member 36 is formed to be relatively larger than a thickness further on the central portion side than the boundary line D. A difference between these thicknesses, that is, an amount of protrusion of the protruding portion 367 is smaller than a thickness of the image forming lens 31. In a state where the first holding member 35 and the second holding member 36 are connected by fastening the connecting tool 37, a small gap is formed between the first holding member 35 and the second holding member 36 as illustrated in
In the present embodiment, the protruding portion 367 is formed at both end portions in the X direction of the second holding member 36, but the present invention is not limited to such a configuration, and the second holding member 36 may be constituted by a separate member divided at the boundary line D. In this case, the divided separate members may be connected and used. However, the same configuration may be employed for the first holding member 35 instead of the second holding member 36.
The groove 357 is formed in a straight line so as to extend from one end portion to the other end portion in the X direction on a surface on the side opposite to the second holding member 36 side of the first plate portion 351 of the first holding member 35. By the above, a portion further on the tip side (side opposite to the second plate portion 352 side) than the groove 357 of the first plate portion 351 is constituted as the elastically deformable portion 358. That is, the elastically deformable portion 358 is elastically deformable about the groove 357 in a direction of approaching the second holding member 36.
The elastically deformable portion 358 is connected to the second holding member 36 using the connecting tool 37. Specifically, the elastically deformable portion 358 approaches the second holding member 36 side as the connecting tool 37 inserted into a through hole formed at both end portions in the X direction of the elastically deformable portion 358 is fastened to the first plate portion 361 (step surface 368) of the second holding member 36. By the above, in a state where the image forming lens 31 is sandwiched between the first holding member 35 and the second holding member 36, the elastically deformable portion 358 elastically deforms and abuts on the image forming lens 31 as illustrated in
However, the elastically deformable portion 358 may be provided in the second holding member 36 instead of the first holding member 35, or the elastically deformable portion 358 may be provided in both the first holding member 35 and the second holding member 36. Further, the configuration is not limited to the configuration in which the groove 357 is formed, and the elastically deformable portion 358 may be formed by another configuration.
In the above variation, the elastically deformable portion 358 is elastically deformed in a direction of approaching the second holding member 36 by force acting on both end portions in the X direction, and abuts on the image forming lens 31. For this reason, in a case where a cross-sectional coefficient of the elastically deformable portion 358 is uniform in the X direction, at a portion closer to a central portion in the X direction of the elastically deformable portion 358, an amount of deformation (distance of approaching the second holding member 36) is smaller and the elastically deformable portion 358 is less likely to abut on the image forming lens 31. As a result, the image forming lens 31 is not uniformly pressed against a reference surface (step surface 365) provided on the second holding member 36, and there is a possibility that straightness of the reading line L is not secured.
In view of the above, the configuration may be such that the elastically deformable portion 358 has a cross-sectional coefficient that is non-uniform in the X direction. Specifically, a cross-sectional coefficient of the elastically deformable portion 358 may be configured to decrease toward a central portion in the X direction of the elastically deformable portion 358. In this case, for example, it is conceivable to form the groove 357 having a depth that becomes larger toward a central portion in the X direction. Note that the central portion is a concept including not only the center in the X direction of the groove 357 but also the vicinity of the center. However, the configuration is not limited to the configuration in which the groove 357 is formed so as to be deeper toward a central portion in the X direction as long as the groove 357 is formed so as to have a different depth depending on a position in the X direction.
Further, as another method, it is conceivable to provide a pressing tool for pressing the image forming lens 31 toward the second holding member 36 side separately from the connecting tool 37. As the pressing tool, for example, as indicated by a two-dot chain line in
Note that, in a case where the set screw 359 as described above is provided, if a fastening torque of the set screw 359 is too large, the elastically deformable portion 358 of the first holding member 35 or the entire first holding member 35 may be unnecessarily deformed. For this reason, it is preferable to manage a fastening torque of the set screw 359 to such a magnitude that the above-described unnecessary deformation does not occur.
Further, since firm fixation of the image forming lens 31 is guaranteed without use of an adhesive, work of fixing the image forming lens 31 is easier than a case of using an adhesive.
Furthermore, since it is not necessary to employ a complicated configuration for fixing the image forming lens 31, manufacturing cost can be reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-181088 | Nov 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/027520 | 7/13/2022 | WO |
