Optical unit and optical line sensor equipped with the same

Abstract

To provide an optical unit reliable with respect to fixation of an image forming lens, and an optical line sensor with the optical unit.SOLUTION: An optical unit (a light receiving unit 3), which is an optical unit for guiding light to a light receiving element 32 provided along a main scanning direction (a direction X), comprises an image forming lens 31 and a pair of holding members 35 and 36. The image forming lens 31 transmits light to form an image on the light receiving element 32. The pair of holding members 35 and 36 holds the image forming lens 31. The image forming lens 31 has a long shape along the main scanning direction and is inserted and held between the pair of holding members 35 and 36 arranged along the main scanning direction with pressing force by the holding members 35 and 36.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an optical unit for guiding light to a light receiving element arranged along a main scanning direction, and an optical line sensor including the same. [Background technology]

[0002] For example, optical line sensors are known that irradiate an object such as a printed matter or a functional film with light and receive the transmitted or reflected light from the object with a light-receiving element. Examples of this type of optical line sensor include a line scan camera and a contact image sensor (CIS).

[0003] An optical line sensor is provided with an imaging lens for forming an image of transmitted or reflected light from an object onto a light receiving element. A rod lens array, which is an example of an imaging lens, is configured in an elongated shape along the main scanning direction by arranging a plurality of rod lenses as imaging elements in the main scanning direction (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5596803 Summary of the Invention [Problem to be solved by the invention]

[0005] In the optical line sensor disclosed in Patent Document 1, the frame body that houses each component of the optical line sensor is divided into two frames. The rod lens array is fixed to one of the frames with an adhesive, and the other frame is positioned so as not to come into contact with the rod lens array. This configuration is intended to prevent the rod lens array from being affected if the two frames are joined with misalignment, but it also creates other problems.

[0006] First, a configuration in which the rod lens array is fixed to only one frame does not guarantee a strong fixation, resulting in low reliability in fixing the rod lens array. Furthermore, fixing the rod lens array using adhesive requires laborious work. Furthermore, it is necessary to form a filling groove in one of the frames for filling with adhesive, which makes the shape of the frame body complex, resulting in high manufacturing costs.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide an optical unit that is highly reliable in terms of fixing an imaging lens, and an optical line sensor including the same.

[0008] Another object of the present invention is to provide an optical unit that allows easy work in fixing an imaging lens, and an optical line sensor equipped with the same.

[0009] Another object of the present invention is to provide an optical unit that can reduce manufacturing costs and an optical line sensor equipped with the same. [Means for solving the problem]

[0010] (1) The optical unit according to the present invention is an optical unit for guiding light to a light receiving element arranged along a main scanning direction, and includes an imaging lens and a pair of holding members. The imaging lens transmits light and forms an image on the light receiving element. The pair of holding members hold the imaging lens. The imaging lens has an elongated shape along the main scanning direction, and is clamped in a pressed state between the pair of holding members arranged along the main scanning direction.

[0011] With this configuration, the imaging lens, which has an elongated shape along the main scanning direction, is clamped and pressed by a pair of holding members arranged along the main scanning direction, thereby ensuring strong fixation and improving the reliability of the fixation of the imaging lens.

[0012] Furthermore, since the imaging lens is guaranteed to be firmly fixed without using adhesive, the work of fixing the imaging lens is easier than when adhesive is used.

[0013] Furthermore, since there is no need to employ a complex structure for fixing the imaging lens, manufacturing costs can be reduced.

[0014] (2) The optical unit may further include a light-receiving substrate, on which the light-receiving element is mounted and which is fixed to the pair of holding members.

[0015] With this configuration, the light-receiving substrate is fixed so that the imaging lens straddles a pair of firmly fixed holding members, thereby accurately maintaining the positional accuracy of the light-receiving element mounted on the light-receiving substrate and the imaging lens.

[0016] (3) The pair of holding members may each be formed with an L-shaped cross section, with a first plate portion and a second plate portion connected together, each extending along the main scanning direction.

[0017] According to this configuration, the pair of holding members can be formed using an inexpensive material with an L-shaped cross section, thereby reducing manufacturing costs.

[0018] (4) When the pair of holding members clamp the imaging lens, the first plate portion of one holding member and the first plate portion of the other holding member may face each other to clamp the imaging lens, and the second plate portion of one holding member and the second plate portion of the other holding member may be positioned on the same plane, so that the pair of holding members are arranged in a T-shape in cross section.

[0019] With this configuration, when the imaging lens is sandwiched between the pair of holding members, the pair of holding members are arranged in a T-shape in cross section, and an empty space can be formed on the side of each of the first plate portions of the pair of holding members that face each other. Other members, such as a light source unit, can be placed in this empty space, thereby achieving improved space saving.

[0020] (5) At least one of the pair of holding members may be provided with an elastically deforming portion extending along the main scanning direction, in which case, when the imaging lens is sandwiched between the pair of holding members, the elastically deforming portion may be elastically deformed and come into contact with the imaging lens.

[0021] With this configuration, the pair of holding members are brought into contact with each other at parts other than the elastic deformation parts, thereby joining them to each other with high precision, and the elastic deformation parts are elastically deformed to bring them into contact with the imaging lens, thereby pressing the imaging lens and firmly fixing it.

[0022] (6) The elastically deforming portion may be elastically deformable around a groove that is formed in at least one of the pair of holding members and extends in the main scanning direction.

[0023] According to this configuration, the elastically deforming portion can be formed with a simple configuration of just forming a groove extending in the main scanning direction, thereby reducing manufacturing costs.

[0024] (7) The depth of the groove may be formed to vary depending on the position in the main scanning direction.

[0025] With this configuration, the imaging lens can be pressed uniformly and firmly fixed.

[0026] (8) The optical unit may further include a pressing tool provided at the center of the elastically deforming portion in the main scanning direction for pressing the imaging lens.

[0027] With this configuration, the imaging lens can be pressed uniformly and firmly fixed.

[0028] (9) An optical line sensor according to the present invention includes the optical unit and a light source unit that irradiates light onto an object transported in a sub-scanning direction. The light irradiated from the light source unit is transmitted through or reflected by the object, and is then imaged on the light-receiving element by passing through the imaging lens. [Effects of the Invention]

[0029] According to the present invention, the reliability of fixing the imaging lens can be improved. Also, according to the present invention, the work of fixing the imaging lens can be simplified. Furthermore, according to the present invention, the manufacturing cost can be reduced. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic cross-sectional view showing an example of the configuration of an optical line sensor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a light receiving unit. [Figure 3] FIG. 2 is an exploded perspective view of the light receiving unit. [Figure 4] FIG. 2 is a cross-sectional view of the light receiving unit. [Figure 5] FIG. 2 is an enlarged perspective view of a part of the light receiving unit 3. [Figure 6] FIG. 10 is a perspective view showing a modified example of the light receiving unit 3. DETAILED DESCRIPTION OF THE INVENTION

[0031] 1. Schematic configuration of optical line sensor 1 is a schematic cross-sectional view showing an example of the configuration of an optical line sensor 1 according to one embodiment of the present invention. This optical line sensor 1 obtains image information by reading an object S being transported in a sub-scanning direction with a reading line L extending in the main scanning direction. In the following description, the main scanning direction is defined as the X direction, the sub-scanning direction (the direction in which the object S is transported) as the Y direction, and the direction perpendicular to the X and Y directions as the Z direction.

[0032] The optical line sensor 1 includes an illumination unit 2 and a light receiving unit 3. In this embodiment, the optical line sensor 1 includes two illumination units 2 and one light receiving unit 3. However, the numbers of illumination units 2 and light receiving units 3 are not limited to those in this embodiment.

[0033] The lighting unit 2 has an elongated shape extending along the X direction, and irradiates the object S with light along an irradiation optical axis A1 perpendicular to the X direction. The light irradiated from the lighting unit 2 is reflected by the object S, and the reflected light travels along a light-receiving optical axis A2 toward the light-receiving unit 3. The lighting unit 2 constitutes a light source section that irradiates light onto the object S being transported in the Y direction.

[0034] The light receiving unit 3 has an elongated shape extending along the X direction, and receives reflected light from the target S along a light receiving optical axis A2 perpendicular to the X direction. The light receiving unit 3 includes a plurality of light receiving elements 32 (described later), and performs photoelectric conversion on the reflected light received by each light receiving element 32 to obtain an electrical signal corresponding to the amount of received light. The light receiving unit 3 constitutes an optical unit for guiding light to the light receiving elements 32 arranged along the X direction.

[0035] The illumination unit 2 and the light receiving unit 3 are connected at both ends in the X direction by a pair of connecting members 4. This fixes the positional relationship between the illumination unit 2 and the light receiving unit 3, forming an integrated optical line sensor 1. The optical line sensor 1 is fixed at a predetermined angle with respect to the conveyance direction (Y direction) of the object S. When 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 illumination optical axis A1 is inclined with respect to, for example, the direction perpendicular to the object S (Z direction).

[0036] The lighting unit 2 includes a plurality of LEDs 21, an LED substrate 22, a condenser lens 23, and a lighting housing 24. The plurality of LEDs 21 are an example of light sources, and each emits light along an illumination optical axis A1 that is parallel to one another. The LED substrate 22 has an elongated shape along the X direction, and the plurality of LEDs 21 are mounted in an array in the X direction and are energized. In other words, the LED substrate 22 constitutes an illumination substrate on which the light sources are mounted and energized. The condenser lens 23 condenses and emits light incident from each LED 21. The lighting 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 illumination optical axis A1 is the optical axis of the LEDs 21 or the condenser lens 23.

[0037] The light-receiving unit 3 includes an imaging lens 31, multiple light-receiving elements 32, a light-receiving substrate 33, and a light-receiving housing 34. The imaging lens 31 transmits light from the target S along a light-receiving optical axis A2, forming an image on the multiple light-receiving elements 32. The multiple light-receiving elements 32 receive the light imaged by the imaging lens 31, perform photoelectric conversion, and output an electrical signal. The light-receiving substrate 33 has an elongated shape along the X direction, and the multiple light-receiving elements 32 are mounted and arranged in the X direction and are electrically connected. The light-receiving housing 34 has an elongated shape along the X direction, and integrally holds the imaging lens 31 and the light-receiving substrate 33 in a predetermined position. The light-receiving optical axis A2 is the optical axis of the multiple imaging elements that make up the imaging lens 31, and the line formed by the focal points of each imaging element on the light-receiving optical axis A2 is the reading line L.

[0038] The imaging lens 31 is, for example, a rod lens array. In this case, the imaging lens 31 is configured in a long array shape along the X direction by arranging multiple rod lenses as imaging elements in the X direction. A rod lens is an example of an erect, equal-magnification imaging element. A typical commercially available rod lens array is the SELFOC Lens Array (registered trademark: Nippon Sheet Glass Co., Ltd.), but in this case, the working distance (the distance from the lens end face to the focal point) is limited to 20 mm or less. If the working distance is 20 mm or less, there is a high probability that the object S will come into contact with the rod lens array and be damaged during transportation, so it is more preferable to use a rod lens array with a working distance of 30 mm or more. To achieve this, it is recommended to create a rod lens array with a working distance of 30 mm or more, or to adjust the working distance to 30 mm or more by appropriately changing the pitch in the optical axis direction of a commercially available rod lens array (working distance of 20 mm or less). In addition to rod lenses, the imaging lens 31 may also be configured by arranging spherical lenses, aspherical lenses, or a lens group combining multiple such lenses in an array in the X direction.

[0039] In this embodiment, the light irradiated from the lighting unit 2 is reflected by the object S and passes through the imaging lens 31 to form an image on the light receiving element 32. However, the present invention is not limited to this configuration, and in a configuration in which the lighting unit 2 is disposed on the opposite side of the object S from the light receiving unit 3 side, the light irradiated from the lighting unit 2 and transmitted through the object S may be imaged on the light receiving element 32 by passing through the imaging lens 31.

[0040] 2. Specific configuration of the light receiving unit Fig. 2 is a perspective view of the light receiving unit 3. Fig. 3 is an exploded perspective view of the light receiving unit 3. Fig. 4 is a cross-sectional view of the light receiving unit 3. Fig. 4 shows a cross section of the light receiving unit 3 cut in a direction perpendicular to the X direction.

[0041] 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 imaging lens 31. The first holding member 35 and the second holding member 36 are arranged along the X direction. In other words, the first holding member 35 and the second holding member 36 extend parallel to the imaging lens 31.

[0042] The first holding member 35 has a configuration in which a first plate portion 351 and a second plate portion 352 are connected to each other. The first plate portion 351 of the first holding member 35 is a plate-shaped 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 an opposing surface 353 that faces the second holding member 36. The opposing surface 353 is parallel to the X direction and the Z direction and perpendicular to the Y direction.

[0043] The second plate portion 352 of the first holding member 35 is a plate-shaped member extending in the X direction along a plane (horizontal plane) parallel to the X and Y directions. 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 and Y directions and perpendicular to the Z direction.

[0044] The first holding member 35 is formed with an L-shaped cross section by connecting a first plate portion 351 and a second plate portion 352. Specifically, the Z-direction end of the first plate portion 351 and the Y-direction end of the second plate portion 352 are connected to connect the first plate portion 351 and the second plate portion 352 so that they are perpendicular to each other. The first plate portion 351 and the second plate portion 352 may be configured by connecting separate members together, or may be configured to be integrally formed.

[0045] The second holding member 36 has a configuration in which a first plate portion 361 and a second plate portion 362 are connected to each other. The first plate portion 361 of the second holding member 36 is a plate-shaped member extending in the X direction along a plane (vertical plane) parallel to the X and Z directions. The first plate portion 361 has an opposing surface 363 that faces the first holding member 35. The opposing surface 363 is parallel to the X and Z directions and perpendicular to the Y direction.

[0046] The second plate portion 362 of the second holding member 36 is a plate-shaped member extending in the X direction along a plane (horizontal plane) parallel to the X and Y directions. 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 and Y directions and perpendicular to the Z direction.

[0047] The second holding member 36 is formed with an L-shaped cross section by connecting a first plate portion 361 and a second plate portion 362. Specifically, the Z-direction end of the first plate portion 361 and the Y-direction end of the second plate portion 362 are connected to connect the first plate portion 361 and the second plate portion 362 so that they are perpendicular to each other. The first plate portion 361 and the second plate portion 362 may be configured by connecting separate members together, or may be configured to be integrally formed.

[0048] A stepped surface 355 extending along the X direction is formed on the opposing surface 353 of the first holding member 35 at the end (lower end) on the opposite side in the Z direction from the second plate portion 352. This stepped surface 355 faces the imaging lens 31. However, the surface of the imaging lens 31 facing the light receiving element 32 does not abut against the stepped surface 355.

[0049] A stepped surface 365 extending along the X direction is formed on the opposing surface 363 of the second holding member 36 at the end (lower end) on the opposite side in the Z direction from the second plate portion 362 side. This stepped surface 365 faces the imaging lens 31, and has a shape corresponding to the shape of a corner of the imaging lens 31 that faces the stepped surface 365. The surface of the imaging lens 31 facing the light receiving element 32 abuts against the stepped surface 365.

[0050] In this way, the stepped surface 365 of the second holding member 36 abuts against the surface of the imaging lens 31 facing the light receiving element 32, and functions as a reference surface for positioning the imaging lens 31 in the Z direction. Therefore, high dimensional accuracy is required for the distance between the upper surface of the stepped surface 365 (the surface that abuts against the surface of the imaging lens 31 facing the light receiving element 32) and the fixing surface 364. This dimensional accuracy preferably has an error of ±0.05 mm or less.

[0051] Furthermore, the surface of the stepped surface 365 of the second holding member 36 facing the side surface of the imaging lens 31 (the surface perpendicular to the Y direction) also functions as a reference surface for positioning the imaging lens 31 in the Y direction. Therefore, the surface of the stepped surface 365 perpendicular to the Y direction needs to be flat with high dimensional accuracy, and the flatness (tolerance) is preferably 0.1 mm or less.

[0052] In contrast, as described above, the step surface 355 of the first holding member 35 does not abut the surface of the imaging lens 31 on the light receiving element 32 side, and therefore does not require the same dimensional accuracy as the step surface 365 of the second holding member 36 from the perspective of positioning the imaging lens 31 in the Z direction. Similarly, the surface of the step surface 355 of the first holding member 35 that faces the side surface of the imaging lens 31 (the surface orthogonal to the Y direction) does not need to be flat with high dimensional accuracy. Therefore, the manufacturing cost of the first holding member 35 can be reduced.

[0053] The step surface 355 of the first holding member 35 and the step surface 365 of the second holding member 36 both function as light-shielding surfaces that do not transmit unnecessary light and block it.

[0054] The first holding member 35 and the second holding member 36 are connected to each other using connectors 37 such as screws. In this embodiment, both ends of the first holding member 35 in the X direction and both ends of the second holding member 36 in the X direction are connected to each other using the connectors 37. Specifically, the connectors 37 are inserted into through holes formed at both ends of the first plate portion 361 of the first holding member 35 and are tightened to the second holding member 36, thereby connecting the first holding member 35 and the second holding member 36.

[0055] At this time, the imaging lens 31 is disposed between the stepped surface 355 of the first holding member 35 and the stepped surface 365 of the second holding member 36, and as the first holding member 35 and the second holding member 36 are connected using the connector 37, both end surfaces in the Y direction of the imaging lens 31 are pressed by the stepped surfaces 355 and 365. As a result, the imaging 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 stepped surfaces 355 and 365. In other words, the imaging lens 31 is held only by the pressing force of the first holding member 35 and the second holding member 36, without using any adhesive.

[0056] In this way, when the first holding member 35 and the second holding member 36 sandwich the imaging 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 imaging lens 31. Furthermore, the second plate portion 352 of the first holding member 35 and the second plate portion 362 of the second holding member 36 are positioned on the same plane (horizontal plane) parallel to the X direction and the Y direction.

[0057] 4, the first holding member 35 and the second holding member 36, which are connected to each other, are arranged so as to have a T-shaped cross section. In this state, the fixing surface 354 of the first holding member 35 and the fixing surface 364 of the second holding member 36 are located on the same plane. However, the method of connecting the first holding member 35 and the second holding member 36 is not limited to the method described above, and any other method can be used as long as it allows the imaging lens 31 to be sandwiched between the first holding member 35 and the second holding member 36 in a pressed state.

[0058] 4, when the first holding member 35 and the second holding member 36 are connected, a portion of the facing surface 353 of the first holding member 35 above the step surface 355 and a portion of the facing surface 363 of the second holding member 36 above the step surface 365 face each other across a space B. This space B forms an optical path for guiding light that has passed through the imaging lens 31 in the Z direction to the light receiving element 32.

[0059] The light-receiving substrate 33 is fixed to the first holding member 35 and the second holding member 36 using fasteners 38 such as screws. Specifically, one end of the light-receiving substrate 33 in the Y direction faces a fixing surface 354 of the first holding member 35, and the other end of the light-receiving substrate 33 in the Y direction faces a fixing surface 364 of the second holding member 36. In this embodiment, fasteners 38 are inserted into through-holes formed in at least four corners of the light-receiving substrate 33 and tightened to the first holding member 35 and the second holding member 36, thereby fixing the light-receiving substrate 33 to the first holding member 35 and the second holding member 36. As a result, the light-receiving substrate 33 is fixed in a state spanning the first holding member 35 and the second holding member 36.

[0060] A step surface 356 is formed on a part of the fixing surface 354 of the first holding member 35, which faces the light-receiving board 33. A step surface 366 is formed on a part of the fixing surface 364 of the second holding member 36, which faces the light-receiving board 33. When the first holding member 35 and the second holding member 36 are connected, the step surfaces 356 and 366 form a space C that communicates with the space B. This space C functions as a region for accommodating components mounted on the light-receiving board 33.

[0061] 5 is an enlarged perspective view of a portion of the light receiving unit 3. In this embodiment, protrusions 367 that protrude toward the first holding member 35 are formed on both ends of the second holding member 36 in the X direction. That is, the second holding member 36 is formed to have different thicknesses on either side of boundary line D indicated by the two-dot chain line in FIGS. 3 and 5.

[0062] Specifically, the thickness of the first plate portion 361 of the second holding member 36 on both end sides of the boundary line D is formed relatively larger than the thickness of the first plate portion 361 on the central side of the boundary line D. The difference between these thicknesses, i.e., the amount of protrusion of the protrusion 367, is smaller than the thickness of the imaging lens 31. When the first holding member 35 and the second holding member 36 are connected by fastening the connector 37, a small gap is formed between the first holding member 35 and the second holding member 36, as shown in FIG. 5. If stray light or dust entering through this gap becomes a problem in an actual usage environment, it is advisable to seal it with a curable paste or the like.

[0063] In this embodiment, the protrusions 367 are formed on both ends of the second holding member 36 in the X direction, but the configuration is not limited to this, and the second holding member 36 may be formed of separate members divided at the boundary line D. In this case, the divided separate members may be connected to each other. However, a similar configuration may be adopted for the first holding member 35 instead of the second holding member 36.

[0064] 3. Variations 6 is a perspective view showing a modified example of the light receiving unit 3. In this modified example, a groove 357 is formed in the first plate portion 351 of the first holding member 35, thereby forming an elastic deformation portion 358 extending along the X direction. In addition, a stepped surface 368 is formed in the first plate portion 361 of the second holding member 36 at a position facing the elastic deformation portion 358. Since the other components are the same as those in the above embodiment, the same components are denoted by the same reference numerals in the drawings and detailed description thereof will be omitted.

[0065] The groove 357 is formed in a straight line extending from one end to the other end in the X direction on the surface of the first plate portion 351 of the first holding member 35 opposite the second holding member 36 side. As a result, the portion of the first plate portion 351 on the tip side of the groove 357 (opposite the second plate portion 352 side) is configured as an elastic deformation portion 358. In other words, the elastic deformation portion 358 is elastically deformable around the groove 357 in a direction approaching the second holding member 36.

[0066] The elastic deformation portion 358 is connected to the second holding member 36 by using a connector 37. Specifically, the connector 37 is inserted into through holes formed at both ends of the elastic deformation portion 358 in the X direction and fastened to the first plate portion 361 (step surface 368) of the second holding member 36, thereby moving the elastic deformation portion 358 closer to the second holding member 36. As a result, when the imaging lens 31 is sandwiched between the first holding member 35 and the second holding member 36, the elastic deformation portion 358 elastically deforms and comes into contact with the imaging lens 31, as shown in FIG.

[0067] However, the elastic deformation portion 358 may be provided on the second holding member 36 instead of the first holding member 35, or the elastic deformation portion 358 may be provided on both the first holding member 35 and the second holding member 36. Furthermore, the elastic deformation portion 358 may be formed by other configurations, not limited to the configuration in which the groove 357 is formed.

[0068] In the above modification, the elastic deformation portion 358 is elastically deformed in a direction approaching the second holding member 36 by forces acting on both ends in the X direction, and comes into contact with the imaging lens 31. Therefore, if the section modulus of the elastic deformation portion 358 is uniform in the X direction, the amount of deformation (the distance approaching the second holding member 36) becomes smaller toward the center of the elastic deformation portion 358 in the X direction, making it more difficult for the elastic deformation portion 358 to come into contact with the imaging lens 31. As a result, the imaging lens 31 will not be pressed uniformly against the reference surface (step surface 365) provided on the second holding member 36, and the straightness of the reading line L may not be ensured.

[0069] Therefore, the section modulus of the elastic deformation portion 358 may be non-uniform in the X direction. Specifically, the section modulus of the elastic deformation portion 358 may be configured to decrease toward the center in the X direction of the elastic deformation portion 358. In this case, for example, it is conceivable to form the groove 357 so that its depth increases toward the center in the X direction. Note that the above-mentioned center is a concept that includes not only the center of the groove 357 in the X direction but also its vicinity. However, as long as the depth of the groove 357 is configured to vary depending on the position in the X direction, it is not limited to a configuration in which it is formed to increase in depth toward the center in the X direction.

[0070] As another method, a pressing tool for pressing the imaging lens 31 toward the second holding member 36 can be provided separately from the connector 37. As the pressing tool, for example, as shown by the two-dot chain line in FIG. 6, at least one pressing screw 359 may be provided in the center of the elastic deformation portion 358 in the X direction. Note that the concept of the center includes not only the center of the elastic deformation portion 358 in the X direction but also its vicinity. The pressing screw 359 is provided so as to penetrate the elastic deformation portion 358 in the Y direction, and by tightening the pressing screw 359, the tip of the pressing screw 359 can press the imaging lens 31 toward the second holding member 36. In this case, the section modulus of the elastic deformation portion 358 may be uniform in the X direction.

[0071] When the set screw 359 as described above is provided, if the tightening torque of the set screw 359 is too large, there is a risk of unnecessary deformation occurring in the elastic deformation portion 358 of the first holding member 35 or in the entire first holding member 35. Therefore, it is preferable to control the tightening torque of the set screw 359 to a value that does not cause the above-mentioned unnecessary deformation.

[0072] 4. Effects (1) In this embodiment, the imaging lens 31, which has an elongated shape along the scanning direction (X direction), is clamped in a pressed state by the first holding member 35 and the second holding member 36 arranged along the main scanning direction, thereby ensuring strong fixation and improving the reliability of the fixation of the imaging lens 31.

[0073] Furthermore, since the imaging lens 31 is guaranteed to be firmly fixed without using adhesive, the work of fixing the imaging lens 31 is easier than when adhesive is used.

[0074] Furthermore, since there is no need to employ a complex structure for fixing the imaging lens 31, the manufacturing cost can be reduced.

[0075] (2) Furthermore, in this embodiment, the light-receiving substrate 33 is fixed so as to straddle the first holding member 35 and the second holding member 36 to which the imaging lens 31 is firmly fixed, so that the positional accuracy of the light-receiving element 32 mounted on the light-receiving substrate 33 and the imaging lens 31 can be accurately maintained.

[0076] (3) Furthermore, in this embodiment, the first holding member 35 and the second holding member 36 can be formed using an inexpensive material with an L-shaped cross section, thereby reducing manufacturing costs.

[0077] (4) In addition, in this embodiment, when the imaging lens 31 is sandwiched between the first holding member 35 and the second holding member 36, the first holding member 35 and the second holding member 36 are arranged to have a T-shaped cross section, and an empty space E (see FIG. 4) can be formed on the side of each of the first plate portions 351, 361 of the first holding member 35 and the second holding member 36 that face each other. Other members such as the lighting unit E can be placed in this empty space E, thereby improving space saving.

[0078] (5) In the modified example shown in FIG. 6, the first plate portion 351 of the first holding member 35 and the first plate portion 361 of the second holding member 36 are abutted at portions other than the elastic deformation portion 358 to be joined to each other with precision, and the elastic deformation portion 358 is elastically deformed to abut against the imaging lens 31, thereby pressing the imaging lens 31 and firmly fixing it.

[0079] (6) Furthermore, in the modified example shown in FIG. 6, the elastic deformation portion 358 can be formed with a simple configuration by simply forming a groove 357 extending in the main scanning direction (X direction), thereby reducing manufacturing costs.

[0080] (7) If the depth of the groove 357 is formed to vary depending on the position in the main scanning direction (X direction), the imaging lens 31 can be pressed uniformly and firmly fixed.

[0081] (8) Furthermore, even if a pressing tool (press screw 359) is provided at the center of the elastic deformation portion 358 in the main scanning direction (X direction) to press the imaging lens 31, the imaging lens 31 can be pressed uniformly and firmly fixed. [Explanation of symbols]

[0082] 1 Optical line sensor 3 Light receiving unit 31 Imaging lens 32 Photodetector 33 Photoreceptor board 35 first holding member 36 Second holding member 351 1st plate part 352 2nd plate part 357 Groove 358 Elastic deformation part 359 Push screw 361 1st plate part 362 2nd plate part

Claims

1. An optical unit for guiding light to a light receiving element provided along a main scanning direction, an imaging lens for transmitting light and forming an image on the light receiving element; a pair of holding members for holding the imaging lens; The imaging lens has an elongated shape along the main scanning direction, and is sandwiched in a pressed state between the pair of holding members arranged along the main scanning direction.

2. The optical unit according to claim 1 , further comprising a light-receiving substrate on which the light-receiving element is mounted and which is fixed to the pair of holding members.

3. 3. The optical unit according to claim 1, wherein each of the pair of holding members has an L-shaped cross section formed by connecting a first plate portion and a second plate portion that extend along the main scanning direction.

4. The optical unit described in claim 3, wherein when the pair of holding members clamp the imaging lens, the first plate portion of one holding member and the first plate portion of the other holding member face each other to clamp the imaging lens, and the second plate portion of one holding member and the second plate portion of the other holding member are positioned on the same plane, thereby forming a T-shaped cross section.

5. An optical unit according to any one of claims 1 to 4, wherein at least one of the pair of holding members is provided with an elastic deformation portion extending along the main scanning direction, and when the imaging lens is clamped between the pair of holding members, the elastic deformation portion elastically deforms and abuts against the imaging lens.

6. 6. The optical unit according to claim 5, wherein the elastically deforming portion is elastically deformable around a groove that is formed in at least one of the pair of holding members and extends in the main scanning direction.

7. 7. The optical unit according to claim 6, wherein the depth of the groove is formed to vary depending on the position in the main scanning direction.

8. 7. The optical unit according to claim 5, further comprising a pressing tool provided at the center of the elastic deformation portion in the main scanning direction, for pressing the imaging lens.

9. An optical unit as described in claim 1, wherein the imaging lens is held in place solely by the pressing force of the pair of holding members, without the use of adhesive.

10. An optical unit according to any one of claims 1 to 9; a light source unit that irradiates light onto an object being transported in the sub-scanning direction, An optical line sensor in which light irradiated from the light source unit is transmitted through or reflected by the object, and is imaged on the light receiving element by passing through the imaging lens.

Images