Optical sensor

Abstract

To suppress the reduction of the amount of light when light received by a light-receiving element of an optical sensor passes through a through hole.SOLUTION: An optical sensor 100 is disposed facing a belt on which a patch composed of a toner is formed on a surface, and includes: a substrate 110; a light-emitting element 120; light-receiving elements (a first light-receiving element 130 and a second light-receiving element 140). The substrate 110 has a front face 110A, a rear face 110B, and through holes (a first hole 111 and a second hole 112). The light-emitting element 120 is fixed to the substrate 110 and emits light. The light-receiving elements are fixed to the rear face 110B of the substrate 110. The light-receiving elements receive the light that has been emitted by the light-emitting element 120 and reflected by the patch P and that has passed through at least a part of the through holes (the first hole 111 and the second hole 112). The through holes (the first hole 111 and the second hole 112) extend from positions to which the light-receiving elements are fixed toward positions to which the light-emitting elements 120 are fixed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an optical sensor disposed opposite a belt.

Background Art

[0002] Conventionally, an optical sensor disposed opposite a belt on which a patch made of toner is formed on the surface is known for measuring the position and density of the formed toner (see Patent Document 1). This optical sensor has a light-emitting element and two light-receiving elements. The light-emitting element and the two light-receiving elements are soldered to a substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to reduce the dimension in the thickness direction of the optical sensor, it is conceivable to dispose the light-receiving element on the back surface of the substrate. In this case, it is necessary to provide a through hole in the substrate for the light to be received to pass through. However, there is a problem that when the light received by the light-receiving element passes through the through hole, the light is blocked at the edge of the through hole and the amount of light is reduced.

[0005] Therefore, an object of the present invention is to suppress a reduction in the amount of light when the light received by the light-receiving element of the optical sensor passes through the through hole.

Means for Solving the Problems

[0006] To solve the above problems, an optical sensor according to the present invention is disposed opposite a belt on which a patch made of toner is formed on the surface, and includes a plate-shaped substrate, a light-emitting element, and a light-receiving element. The substrate has a front surface facing the belt, a back surface opposite the front surface, and through holes that penetrate both the front and back surfaces. The light-emitting element is fixed to the substrate and emits light. The light-receiving element is fixed to the back surface of the substrate. The light-receiving element receives light that is emitted by the light-emitting element, reflected by the patch, and passes through at least a portion of the through holes. The through holes extend along the surface of the substrate from the position where the light-receiving element is fixed toward the position where the light-emitting element is fixed.

[0007] In this configuration, the through-holes in the substrate extend from the position where the photodetector is fixed towards the position where the light-emitting element is fixed, making it less likely for the light received by the photodetector to be blocked by the edges of the through-holes. Therefore, it is possible to suppress the reduction in light intensity as the light received by the photodetector passes through the through-holes.

[0008] Furthermore, in the optical sensor described above, the light-receiving element may include a first light-receiving element that receives the specular reflection component of light reflected by the patch, and a second light-receiving element that receives the diffuse reflection component of light reflected by the patch, and the through-hole may include a first hole corresponding to the first light-receiving element and a second hole corresponding to the second light-receiving element, wherein the first hole extends from the position where the first light-receiving element is fixed toward the position where the light-emitting element is fixed, and the second hole extends from the position where the second light-receiving element is fixed toward the position where the light-emitting element is fixed.

[0009] Furthermore, the optical sensor described above may further include a holder for holding the substrate, and the holder may have a light-emitting hole through which light emitted from the light-emitting element passes, a first light-receiving hole for guiding the specular reflection component of the light from the light-emitting element reflected by the patch to a first light-receiving element, and a second light-receiving hole for guiding the diffuse reflection component of the light from the light-emitting element diffused by the patch to a second light-receiving element.

[0010] Furthermore, in the optical sensor described above, the holder may have a first light-shielding wall located between the light-emitting element and the first light-receiving element, and a second light-shielding wall located between the light-emitting element and the second light-receiving element, wherein the first light-shielding wall may have a groove formed on the opposing surface facing the light-emitting element.

[0011] With this configuration, the first light-shielding wall prevents light emitted from the light-emitting element from directly reaching the first light-receiving element, and the second light-shielding wall prevents light emitted from the light-emitting element from directly reaching the second light-receiving element. Furthermore, the groove formed on the opposite surface of the first light-shielding wall prevents light reflected by the first shielding wall from reaching the second light-receiving element. As a result, the reading accuracy of the second light-receiving element is improved.

[0012] Furthermore, in the optical sensor described above, the groove formed on the opposing surface may be configured to extend in a direction along the optical axis of the light-emitting element.

[0013] Furthermore, in the optical sensor described above, the first hole may have a first portion through which the specular reflection component of the light reflected by the patch passes and a second portion extending in a direction intersecting the first portion, the second hole may have a third portion through which the diffuse reflection component of the light reflected by the patch passes and a fourth portion extending in a direction intersecting the third portion, the first light-shielding wall may have a first leg portion that enters the second portion, and the second light-shielding wall may have a second leg portion that enters the fourth portion.

[0014] Furthermore, in the optical sensor described above, the light-emitting element may be located on the back surface of the substrate, and the substrate may have a third hole that penetrates both the front and back surfaces, through which the light emitted by the light-emitting element passes.

[0015] With this configuration, both the light-emitting element and the light-receiving element are located on the back side of the substrate, making it easier to assemble the optical sensor. [Effects of the Invention]

[0016] According to the present invention, it is possible to suppress the reduction in light intensity when the light received by the light-receiving element of an optical sensor passes through a through-hole. [Brief explanation of the drawing]

[0017] [Figure 1] This is a cross-sectional view of a color printer according to an embodiment. [Figure 2] This is a perspective view showing the belt unit and optical sensor. [Figure 3] It is a cross-sectional view of an optical sensor. [Figure 4] It is an exploded perspective view of the optical sensor seen from the frame side. [Figure 5] It is an exploded perspective view of the optical sensor seen from the side opposite to FIG. 4. [Figure 6] It is an enlarged view of FIG. 3 and is a diagram for explaining the contact portion between the lens member and the holder. [Figure 7] It is an enlarged view of the holder in FIG. 5 and is a diagram for explaining the groove formed on the opposing surface. [Figure 8] FIG. (a) shows the optical path of the light received by the light receiving element in this embodiment, and FIG. (b) shows the optical path of the light received by the conventional light receiving element. [Figure 9] It is a diagram for explaining the action that the light emitted from the light emitting element is reflected by the groove on the opposing surface. [Figure 10] It is a comparative example diagram showing an example of the optical path when there is no groove formed on the opposing surface.

Embodiments for Carrying Out the Invention

[0018] Next, embodiments of the present invention will be described in detail with appropriate reference to the drawings. As shown in FIG. 1, a laser printer 1 as an example of an image forming apparatus includes a main body housing 10, a supply unit 20, an image forming unit 30, and a discharge unit 90.

[0019] The supply unit 20 includes a supply tray 21 and a sheet supply device 22. The supply tray 21 is a tray for accommodating the sheet S. The sheet supply device 22 conveys the sheet S in the supply tray 21 toward the image forming unit 30.

[0020] The image forming unit 30 includes four LED units 40, four process cartridges 50, a belt unit 70, and a fixing device 80.

[0021] The LED unit 40 has multiple LEDs. The LED unit 40 exposes the photosensitive drum 51, which will be described later.

[0022] The process cartridge 50 includes a photosensitive drum 51, a charger 52, a developing roller (indicated by abbreviated notation), a toner storage chamber, and the like. The process cartridge 50 contains toners of black, cyan, magenta, and yellow, indicated by the notations 50K, 50C, 50M, and 50Y, and in the direction of transporting the sheet S, they are arranged in the order of 50K, 50C, 50M, and 50Y from downstream to upstream.

[0023] The belt unit 70 includes a drive roller 71, a driven roller 72, a conveyor belt 73 as an example of a belt, and four transfer rollers 74.

[0024] The drive roller 71 and the driven roller 72 are rollers that rotate the conveyor belt 73. The drive roller 71 and the driven roller 72 are in contact with the inner circumferential surface of the conveyor belt 73.

[0025] The conveyor belt 73 is a belt that conveys the sheet S between each photosensitive drum 51. The outer surface of the conveyor belt 73 is in contact with each photosensitive drum 51. The transfer roller 74 sandwiches the conveyor belt 73 between itself and the photosensitive drum 51.

[0026] The fixing device 80 includes a heating roller 81 and a pressure roller 82. The heating roller 81 has a halogen heater 81A inside. The pressure roller 82 sandwiches the sheet S between itself and the heating roller 81.

[0027] In the image forming unit 30, first, the surface of the photosensitive drum 51 is charged by the charger 52 and then exposed by the LED unit 40. This forms an electrostatic latent image on the photosensitive drum 51. Subsequently, toner is supplied to the electrostatic latent image from the developing roller, forming a toner image on the photosensitive drum 51.

[0028] Next, the sheet S supplied onto the conveyor belt 73 passes between the photosensitive drum 51 and the transfer roller 74, transferring the toner image formed on the photosensitive drum 51 onto the sheet S. Then, the sheet S passes between the heating roller 81 and the pressure roller 82, thermally fixing the toner image transferred onto the sheet S.

[0029] The discharge unit 90 is configured to transport the sheet S discharged from the fixing device 80 toward the outside of the main housing 10. The discharge unit 90 includes a transport roller 91 and a discharge roller 92. The sheet S discharged from the fixing device 80 is transported by the transport roller 91 to the discharge roller 92, and then discharged by the discharge roller 92 to the discharge tray 11.

[0030] As shown in Figures 1 and 2, the image forming unit 30 further comprises an optical sensor 100 and a register sensor RS. The optical sensor 100 and the register sensor RS are positioned opposite each other at the end of the conveyor belt 73 on the drive roller 71 side.

[0031] The register sensor RS is positioned opposite the surface of the conveyor belt 73. The register sensor RS is a sensor that detects the position of patches P formed on the surface of the conveyor belt 73. Here, patches P are test toner images used to correct toner color misalignment and density. Patches P are formed on the conveyor belt 73 as patches PK, PC, PM, and PY corresponding to black, cyan, magenta, and yellow, respectively. Patches P are transferred from each photosensitive drum 51 to the conveyor belt 73 when correcting toner color misalignment and density. The register sensor RS has one light-emitting element and one light-receiving element (not shown).

[0032] As shown in Figure 3, the optical sensor 100 can be attached to a frame F, which is part of the main housing 10 of the laser printer 1. The optical sensor 100 is positioned facing the surface of the conveyor belt 73. The optical sensor 100 is a sensor that detects the position and density of patches P formed on the surface of the conveyor belt 73. Specifically, when the control unit (not shown) of the laser printer 1 detects the position and density of patches P, it forms patches P on the surface of the conveyor belt 73 (see Figure 2). The optical sensor 100 detects the brightness of the specular and diffuse reflection components in the reflected light of the "part with patches P" on the surface of the conveyor belt 73, and the brightness of the specular and diffuse reflection components in the reflected light of the "part without patches P". Based on the detection results of the optical sensor 100, the control unit determines the position and density of patches P.

[0033] The optical sensor 100 comprises a substrate 110, a light-emitting element 120, a first light-receiving element 130, a second light-receiving element 140, a lens member 150, a holder 160, and a substrate holder 170. The first light-receiving element 130 and the second light-receiving element 140 are examples of light-receiving elements. In the following description, the longitudinal direction of the substrate 110 is referred to as the "first direction," and the short direction of the substrate 110 is referred to as the "second direction." The second direction is the direction that intersects the first direction, and in this embodiment, the second direction is perpendicular to the first direction. Furthermore, the direction perpendicular to both the first and second directions is referred to as the "third direction." The third direction is the thickness direction of the substrate 110.

[0034] As shown in Figures 4 and 5, the substrate 110 is a rectangular plate that is elongated in the first direction. The substrate 110 has a front surface 110A and a back surface 110B. The front surface 110A is the surface facing the patch P (see Figure 3). The back surface 110B is the surface opposite to the front surface 110A.

[0035] In the third direction, the substrate 110 is positioned between the holder 160 and the substrate retainer 170. The front surface 110A of the substrate 110 is in contact with the holder 160, and the back surface 110B of the substrate 110 is in contact with the substrate retainer 170.

[0036] The light-emitting element 120 has the function of emitting light. The light-emitting element 120 is, for example, an LED. The light-emitting element 120 is fixed to the back surface 110B. More specifically, the light-emitting element 120 is joined to the back surface 110B by soldering, and a part of it is inserted into the third hole 113, which will be described later.

[0037] The first light-receiving element 130 and the second light-receiving element 140 are fixed to the back surface 110B. Specifically, the first light-receiving element 130 is joined to the back surface 110B by soldering, with a portion of it fitting into the first hole 111, which will be described later. Similarly, the second light-receiving element 140 is joined to the back surface 110B by soldering, with a portion of it fitting into the second hole 112, which will be described later. As shown in Figure 3, each light-receiving element (first light-receiving element 130 and second light-receiving element 140) receives light that is emitted from the light-emitting element 120, reflected by the patch P, and passes through at least a portion of the through-holes (first hole 111 and second hole 112, described later) formed in the substrate 110. The first light-receiving element 130 and the second light-receiving element 140 are, for example, photodiodes that are sensitive to the wavelength of light emitted from the light-emitting element 120.

[0038] The first light-receiving element 130 is positioned where the specular reflection component of the light reflected by patch P is incident, that is, where the incident light and the reflected light are equal among the light emitted from the light-emitting element 120 to patch P are incident. With this positioning, the first light-receiving element 130 receives the specular reflection component of the light from the light-emitting element 120 that is reflected by patch P.

[0039] The second light-receiving element 140 is positioned where the diffuse reflection component of the light reflected by patch P is incident, that is, where the light component that is not the specular reflection component of the light irradiated from the light-emitting element 120 to patch P is incident. As a result, the second light-receiving element 140 receives the diffuse reflection component of the light from the light-emitting element 120 that has been reflected by patch P.

[0040] The light-emitting element 120, the first photodetector 130, and the second photodetector 140 are arranged with a gap between them in the first direction. In the first direction, the gap between the light-emitting element 120 and the first photodetector 130 is smaller than the gap between the light-emitting element 120 and the second photodetector 140. That is, the first photodetector 130 is located closer to the light-emitting element 120 than the second photodetector 140.

[0041] Furthermore, the substrate 110 has a first hole 111, a second hole 112, a third hole 113, a fourth hole 114, and a fifth hole 115. The first hole 111, the second hole 112, the third hole 113, the fourth hole 114, and the fifth hole 115 are spaced apart in the first direction. The first hole 111 and the second hole 112 are examples of through holes that penetrate the surface 110A and the back surface 110B.

[0042] The first hole 111 is located between the third hole 113 and the fourth hole 114 in the first direction. The first hole 111 corresponds to the first photodetector 130. The first hole 111 has a T-shape and has a first portion 111A extending in the first direction and a second portion 111B extending in the second direction. The first portion 111A extends along the surface of the substrate 110 from the position where the first photodetector 130 is fixed toward the position where the light-emitting element 120 is fixed. The first portion 111A is the portion through which the specular reflection component of the light reflected by the patch P passes. The central part of the second portion 111B is connected to the end of the first portion 111A. The second portion 111B is the portion into which the first leg portion W11, which will be described later, enters.

[0043] The second hole 112 is located between the third hole 113 and the fifth hole 115 in the first direction. The second hole 112 corresponds to the second photodetector 140. The second hole 112 has a T-shape and has a third portion 112A extending in the first direction and a fourth portion 112B extending in the second direction. The third portion 112A extends along the surface of the substrate 110 from the position where the second photodetector 140 is fixed toward the position where the light-emitting element 120 is fixed. The third portion 112A is the portion through which the diffuse reflection component of the light reflected by the patch passes. The central part of the fourth portion 112B is connected to the end of the third portion 112A. The fourth portion 112B is the portion into which the second leg portion W21, which will be described later, enters.

[0044] The third hole 113 is located in the center of the substrate 110 in the first direction. The third hole 113 is located between the first hole 111 and the second hole 112 in the first direction. The third hole 113 is a hole through which light emitted by the light-emitting element 120 passes.

[0045] The fourth hole 114 and the fifth hole 115 are circular in shape and position the substrate 110. Specifically, the first positioning boss 166 and the second positioning boss 167, described later, fit into these holes, positioning the substrate 110 relative to the holder 160 in the first and second directions. The fourth hole 114 is a round hole. The fifth hole 115 is an elongated hole that is longer in the first direction.

[0046] The lens member 150 is made of transparent resin. The lens member 150 is located between the frame F and the substrate 110. The lens member 150 has a first surface 150A facing the frame F and a second surface 150B facing the substrate 110. The lens member 150 also has a first optical surface 151, a second optical surface 152, a third optical surface 153, a frame-side optical surface 154, a projection 155, a third hook 156, a sixth hole 157, and a seventh hole 158 (see also Figure 4). The first optical surface 151, the second optical surface 152, the third optical surface 153, and the frame-side optical surface 154 are examples of optical surfaces of the lens member 150.

[0047] The frame-side optical surface 154 is a planar optical surface formed on the first surface 150A. Light emitted from the light-emitting element 120, the specular reflection component of the light reflected by patch P, and the diffuse reflection component of the light reflected by patch P all pass through the frame-side optical surface 154.

[0048] The projections 155 protrude from the frame-side optical surface 154 of the first surface 150A toward the frame F. In this embodiment, four projections 155 are provided. These four projections 155 are arranged to surround the frame-side optical surface 154. When the optical sensor 100 is mounted on the frame F, the projections 155 are in contact with the frame F, while the frame-side optical surface 154 is not in contact with the frame F.

[0049] The second surface 150B is the surface opposite to the first surface 150A. The second surface 150B is a surface having an optical surface that is at least partially convex. The second surface 150B has a first optical surface 151, a second optical surface 152, and a third optical surface 153 as optical surfaces. The first optical surface 151, the second optical surface 152, and the third optical surface 153 are curved optical surfaces having a convex shape. The radius of curvature of the optical surface of the second surface 150B is smaller than the radius of curvature of the first surface 150A, and the second surface 150B constitutes a lens with positive power.

[0050] The first optical surface 151 is an optical surface through which light emitted from the light-emitting element 120 passes. The first optical surface 151 refracts the light emitted from the light-emitting element 120. The second optical surface 152 is an optical surface through which the specular reflection component of the light reflected by patch P passes. The second optical surface 152 refracts the specular reflection component of the light reflected by patch P. The third optical surface 153 is an optical surface through which the diffuse reflection component of the light reflected by patch P passes. The third optical surface 153 refracts the diffuse reflection component of the light reflected by patch P.

[0051] The third hooks 156 are positioned at both ends in the first direction and are the parts that engage with the holder 160. The tips of the third hooks 156 extend toward the holder 160 and have hook holes 156A that penetrate in the first direction. The hook holes 156A are holes into which the holder claws 168, which will be described later, engage. When the holder claws 168 enter the hook holes 156A, the lens member 150 engages with the holder 160, preventing the lens member 150 from coming off the holder 160.

[0052] The sixth hole 157 is a round hole. The seventh hole 158 is an elongated hole that is longer in the first direction. The sixth hole 157 and the seventh hole 158 position the lens member 150. Specifically, the first positioning boss 166, which will be described later, fits into the sixth hole 157. The second positioning boss 167, which will be described later, fits into the seventh hole 158. This positions the lens member 150 relative to the holder 160 in the first and second directions.

[0053] The holder 160 is a resin component that holds the substrate 110. The holder 160 is located between the frame F and the substrate 110 when the optical sensor 100 is mounted on the frame F (see Figure 3). The holder 160 is mounted on the surface 110A of the substrate 110 so as to cover the light-emitting element 120, the first light-receiving element 130, and the second light-receiving element 140. The holder 160 is fixed together with the frame F, sandwiching the lens member 150 between them.

[0054] The holder 160 includes a holder body 161, a positioning projection 161T, a light-emitting hole 162, a first light-receiving hole 163, a second light-receiving hole 164, a first hook 165, a first positioning boss 166, a second positioning boss 167, a holder claw 168, a second hook engagement portion 169, a first light-shielding wall W1, and a second light-shielding wall W2.

[0055] The positioning projection 161T protrudes from the holder body 161 toward the lens member 150. When the lens member 150 is attached to the holder 160, the positioning projection 161T contacts the second surface 150B of the lens member 150 (see Figure 6). The contact of the positioning projection 161T with the second surface 150B positions the lens member 150 in a third direction relative to the holder 160.

[0056] The light-emitting hole 162 is located in the center of the holder body 161 in the first direction. The light-emitting hole 162 is a through-hole that penetrates in the third direction and is formed in a circular shape. Light emitted from the light-emitting element 120 passes through the light-emitting hole 162.

[0057] The first light-receiving hole 163 and the second light-receiving hole 164 are through-holes that penetrate in the third direction and are spaced apart from the light-emitting hole 162 in the first direction. The first light-receiving hole 163 is a hole for guiding the specular reflection component of the light-emitting element 120 reflected by patch P to the first light-receiving element 130. The second light-receiving hole 164 is a hole for guiding the diffuse reflection component of the light-emitting element 120 reflected by patch P to the second light-receiving element 140.

[0058] The first hook 165 is the portion that protrudes from the holder body 161 and engages with the frame F. The first hook 165 is formed in an L-shape, protruding from the holder body 161 toward the frame F, and its tip extends in a first direction. In this embodiment, two first hooks 165 are arranged, spaced apart in the first direction. The tips of both first hooks 165 both extend in the same direction in the first direction.

[0059] As shown in Figures 4 and 5, the first positioning boss 166 and the second positioning boss 167 have a cylindrical shape and extend in a third direction. The first positioning boss 166 and the second positioning boss 167 protrude from the holder body 161 on both sides in the third direction. The amount of protrusion of the second positioning boss 167 towards the substrate 110 is greater than the amount of protrusion of the first positioning boss 166. The first positioning boss 166 and the second positioning boss 167 are spaced apart in the first direction.

[0060] The first positioning boss 166 fits into the sixth hole 157 of the lens member 150, the fourth hole 114 of the substrate 110, and the first positioning groove 173 (described later), thereby positioning the lens member 150, the substrate 110, the holder 160, and the substrate retainer 170 in the first and second directions. The second positioning boss 167 fits into the seventh hole 158 of the lens member 150, the fifth hole 115 of the substrate 110, and the second positioning groove 174 of the substrate retainer 170 (described later), thereby positioning the lens member 150, substrate 110, holder 160, and substrate retainer 170 in the first and second directions.

[0061] The holder claws 168 are claws formed on the holder body portion 161. Two holder claws 168 are formed and are located outside the first positioning boss 166 and the second positioning boss 167 in the first direction. The holder claws 168 protrude in the first direction and fit into the hook hole 156A of the lens member 150. When the holder claws 168 are fitted into the hook hole 156A, there is a gap in the third direction between the holder claws 168 and the hook hole 156A (see Figure 6). Because of this gap, the holder claws 168 and the hook 156 do not contribute to the positioning of the lens member 150 and the holder 160 in the third direction.

[0062] The second hook engagement portion 169 is located at both ends of the holder 160 in the first direction. The second hook engagement portion 169 is the portion to which the second hook 172 of the substrate holder 170, which will be described later, engages.

[0063] The first light-shielding wall W1 is located between the light-emitting element 120 and the first light-receiving element 130. The first light-shielding wall W1 is a wall that blocks light emitted from the light-emitting element 120 from reaching the first light-receiving element 130 in directions other than through the light-emitting hole 162 of the holder 160. In a first direction, the first light-shielding wall W1 is located between the light-emitting element 120 and the first light-receiving element 130. The first light-shielding wall W1 has first legs W11 that enter into the first hole 111 of the substrate 110.

[0064] The first leg portion W11 is the part of the first light-shielding wall W1 that fits into the first hole 111. In this embodiment, the first leg portion W11 is fitted into the second portion 111B of the first hole 111.

[0065] The first light-shielding wall W1 has a groove MZ formed on its opposing surface W12 facing the light-emitting element 120 (see also Figure 7). The groove MZ is a V-shaped notch when viewed from the third direction. The groove MZ extends in the direction along the optical axis of the light-emitting element 120, i.e., the third direction.

[0066] The second light-shielding wall W2 is located between the light-emitting element 120 and the second light-receiving element 140. The second light-shielding wall W2 is a wall that blocks light emitted from the light-emitting element 120 from reaching the second light-receiving element 140 in directions other than through the light-emitting hole 162 of the holder 160. In the first direction, the second light-shielding wall W2 is located between the light-emitting element 120 and the second light-receiving element 140. The second light-shielding wall W2 has a second leg portion W21 that enters the second hole 112 of the substrate 110.

[0067] The second leg portion W21 is the part of the second light-shielding wall W2 that fits into the second hole 112. In this embodiment, the second leg portion W21 is fitted into the fourth portion 112B of the second hole 112.

[0068] The substrate holder 170 is a component that, together with the holder 160, secures the substrate 110 in a clamping position. The substrate holder 170 has a substrate holder body 171, a second hook 172, a first positioning groove 173, a second positioning groove 174, a first elastic part 175, and a second elastic part 176.

[0069] The second hook 172 is a hook that protrudes from the substrate holder body 171 and engages with the holder 160. The second hook 172 is positioned at both ends of the substrate holder 170 in the first direction and protrudes from the substrate holder body 171 in a third direction. The second hook 172 engages with the second hook engaging portion 169 of the holder 160. The substrate holder 170 is fixed to the holder 160 by the engagement of the second hooks 172 at both ends with the second hook engaging portion 169.

[0070] The first positioning groove 173 and the second positioning groove 174 are grooves provided in the substrate holder body 171. The first positioning groove 173 is into which the first positioning boss 166 of the holder 160 fits. The second positioning groove 174 is into which the second positioning boss 167 of the holder 160 fits. As a result, the substrate holder 170 is positioned in the first and second directions relative to the holder 160.

[0071] The first elastic portion 175 and the second elastic portion 176 are thinner and less rigid than other parts of the substrate holder 170.

[0072] Next, referring to Figures 3 to 5, the assembly method of the optical sensor 100 and the method of attaching the optical sensor 100 to the frame F will be explained.

[0073] As shown in Figure 4, when assembling the optical sensor 100, first the lens member 150 is fitted into the holder 160. At this time, the first positioning boss 166 of the holder 160 is inserted into the sixth hole 157 of the lens member, and the second positioning boss 167 of the holder 160 is inserted into the seventh hole 158 of the lens member. Then, as shown in Figure 3, when the holder claws 168 of the holder 160 are engaged with the hook holes 156A of the lens member 150, the lens member 150 will not easily come off the holder 160. In this case, the holder claws 168 engage with the hook holes 156A, but because there is a gap, no pressing force is generated between the lens member 150 and the holder 160.

[0074] Next, with the substrate 110 sandwiched between the holder 160 and the substrate retainer 170, the substrate retainer 170 is assembled to the holder 160. At this time, the first positioning boss 166 of the holder 160 is placed into the first positioning groove 173 of the substrate retainer 170, and the second positioning boss 167 of the holder 160 is placed into the second positioning groove 174 of the substrate retainer 170. Then, the second hook 172 of the substrate retainer 170 is engaged with the second hook engaging portion 169 of the holder 160. When the second hook 172 engages with the second hook engaging portion 169, the first elastic portion 175 and the second elastic portion 176 bend and flex. As a result, the elastic restoring force of the first elastic portion 175 and the second elastic portion 176 causes the substrate retainer body 171 to press the substrate 110 toward the holder. In other words, the substrate holder body 171 presses the substrate 110 toward the holder 160 when the second hook 172 engages with the holder 160.

[0075] Next, when attaching the optical sensor 100 to the frame F, the first hook 165 is inserted into the frame hole FH of the frame F, and then the entire optical sensor 100 is slid in the direction in which the tip of the first hook 165 extends. This causes both first hooks 165 to engage with the frame F, preventing the optical sensor 100 from easily detaching from the frame F.

[0076] When the first hook 165 is engaged with the frame F, the first hook 165 bends so as to spread in the third direction. As the first hook 165 bends, the elastic restoring force of the first hook 165 pulls the holder body 161 toward the frame F. As a result, the holder body 161 presses the lens member 150 toward the frame F when the first hook 165 engages with the frame F.

[0077] According to the first embodiment, the following effects can be obtained. As shown in Figure 8(b), if the light-receiving elements 130 and 140 are placed on the back surface of the substrate 110J (the lower surface in Figure 8(b)) in order to reduce the thickness dimension of the optical sensor 100J that detects the patch, then through holes 111J and 112J must be provided in the substrate 110J for the light to pass through. However, when the light received by the light-receiving elements 130 and 140 passes through the through holes 111J and 112J, the light is blocked at the edges of the through holes 111J and 112J, reducing the amount of light. However, according to the optical sensor 100 of the first embodiment, as shown in Figure 8(a), the through holes in the substrate 110, namely the first hole 111 and the second hole 112, extend from the position where the first light-receiving element 130 and the second light-receiving element 140 are fixed toward the position where the light-emitting element 120 is fixed. Therefore, the light received by the first light-receiving element 130 and the second light-receiving element 140 is less likely to be blocked by the edges of the first hole 111 and the second hole 112. As a result, it is possible to suppress the reduction in light intensity when the light received by the first light-receiving element 130 and the second light-receiving element 140 passes through the first hole 111 and the second hole 112.

[0078] Furthermore, as shown in Figure 9, the holder 160 of the optical sensor 100 has a first light-shielding wall W1 located between the light-emitting element 120 and the first light-receiving element 130, and a second light-shielding wall W2 located between the light-emitting element 120 and the second light-receiving element 140. If a groove MZ is not formed on the opposing surface W12, as in the comparative example shown in Figure 10, light emitted from the light-emitting element 120 may be reflected at the opposing surface W12 of the first light-shielding wall W1 and reach the second light-receiving element 140. However, as shown in Figure 9, the holder 160 of the optical sensor 100 has a groove MZ formed on the opposing surface W12, so that the light emitted from the light-emitting element 120 is reflected in the groove MZ in a direction different from that of patch P. Therefore, the light emitted from the light-emitting element 120 is reflected at the opposing surface W12 and is prevented from directly reaching the second photodetector 140. As a result, the reading accuracy of the second photodetector 140 is improved.

[0079] Furthermore, in the optical sensor 100, the light-emitting element 120 is located on the back surface 110B of the substrate 110, so both the light-emitting element 120 and the light-receiving elements (first light-receiving element 130 and second light-receiving element 140) are located on the back side of the substrate 110. This makes the assembly of the optical sensor 100 easier.

[0080] Furthermore, the holder body 161 of the optical sensor 100 presses the lens member 150 toward the frame F when the first hook 165 engages with the frame F. Specifically, when the holder 160 is attached to the frame F, the first hook 165 bends so as to spread in a third direction, and the restoring force of this bending pulls the holder body 161 toward the frame F, thereby pressing the lens member 150 toward the frame F. In this way, the lens member 150 can be pressed and fixed toward the frame F, so that the error in the distance between the light-emitting element 120, the first light-receiving element 130, the second light-receiving element 140, and the lens member 150 and the patch P can be reduced. As a result, the optical sensor 100 can reduce the error in the distance between the light-emitting element 120, the first light-receiving element 130, the second light-receiving element 140, and the lens member 150 and the patch P, thereby improving the accuracy for measuring the position and density of the patch P.

[0081] Furthermore, when the second hook 172 of the substrate holder 170 engages with the second hook engagement portion 169 of the holder 160, the first elastic portion 175 and the second elastic portion 176 of the substrate holder 170 bend and flex, and the restoring force of this flexing causes the substrate holder body 171 to press the substrate 110 toward the holder 160. In this way, the substrate 110 can be pressed and fixed toward the holder 160, so that the error in the distance between the light-emitting element 120, the first light-receiving element 130, the second light-receiving element 140, and the lens member 150 and the patch P can be reduced. As a result, the optical sensor 100 can reduce the error in the distance between the light-emitting element 120, the first light-receiving element 130, the second light-receiving element 140, and the lens member 150 and the patch P, thus improving the accuracy for measuring the position and density of the patch P.

[0082] Furthermore, the positioning projection 161T of the holder 160 is in contact with the lens member 150 when the lens member 150 is attached to the holder 160. By positioning the lens member 150 relative to the holder 160 through this positioning projection 161T, the position of the lens member 150 is precisely determined.

[0083] Furthermore, when the optical sensor 100 is attached to the frame F, the projection 155 of the lens member 150 contacts the frame F, while the frame-side optical surface 154 of the lens member 150 does not contact the frame F. Therefore, contact between the projection 155 and the frame F prevents misalignment of the positional relationship between the frame F and the frame-side optical surface 154, and since the frame-side optical surface 154 does not contact the frame F, damage to the frame-side optical surface 154 is prevented.

[0084] Furthermore, the lens member 150 has a third hook 156 that engages with the holder 160. Therefore, the lens member 150 is less likely to come off the holder 160.

[0085] Furthermore, when the lens member 150 is attached to the holder 160, there is a gap between the hook hole 156A and the holder claw 168 in a third direction, which is the thickness direction of the substrate 110. As a result, the holder claw 168 fits into the hook hole 156A, preventing the lens member 150 from coming off the holder 160, but the gap between the hook hole 156A and the holder claw 168 in the third direction does not interfere with the positioning of the lens member 150 and the holder 160. In addition, the engagement between the hook hole 156A and the holder claw 168 prevents the lens member 150 from bending.

[0086] Furthermore, the lens member 150 has a first surface 150A facing the frame F and a second surface 150B facing the substrate 110, with a flat frame-side optical surface 154 positioned on the first surface 150A. By creating a lens shape with minimal protrusion on the frame F side in this way, the frame-side optical surface 154 is less likely to be scratched when the optical sensor 100 is attached to the frame F.

[0087] Furthermore, the lens element 150 is a positive power lens in which the first surface 150A facing the frame F has a larger radius of curvature than the second surface 150B facing the substrate 110. Therefore, when the optical sensor 100 is attached to the frame F, the optical surface of the lens element 150 is less likely to be scratched.

[0088] The present invention is not limited to the embodiments described above, and can be used in various forms as illustrated below.

[0089] In the above embodiment, four protrusions 155 were provided on the first surface 150A of the lens member 150, but the number of protrusions is not particularly limited. For example, the number of protrusions may be 1 to 3, or 5 or more.

[0090] In the first embodiment described above, a portion of the light-emitting element 120, the first light-receiving element 130, and the second light-receiving element 140 was inserted into the through-hole 113 of the substrate 110. However, the entirety of the first light-receiving element 130 and the second light-receiving element 140 may be inserted into the through-hole 113, or the entirety of the first light-receiving element 130 and the second light-receiving element 140 may not be inserted into the through-hole 113.

[0091] In the above embodiment, the lens member 150 was made of a transparent resin, but the lens member may be made of a material other than resin, such as glass.

[0092] In the above embodiment, a transport belt 73 that transports the sheet S between each photosensitive drum 51 was given as an example of a belt, but the configuration is not limited to this. For example, the belt may be an intermediate transfer belt that transports the toner image that has been primary transferred by each photosensitive drum to the point where it is transferred to the sheet in a secondary transfer.

[0093] In the above embodiment, the present invention was applied to a laser printer 1, but the present invention is not limited thereto and may be applied to other image forming devices, such as photocopiers and multifunction printers.

[0094] The elements described in the above embodiments and modifications may be implemented in any combination. [Explanation of symbols]

[0095] 100 Optical Sensors 110 circuit boards 110A surface 110B back side 111 Hole 1 111A Part 1 111B 2nd part 112 2nd hole 112A 3rd part 112B 4th part 120 light-emitting elements 130 First photodetector 140 Second photodetector 150 Lens components 150A 1st side 150B 2nd side 151 1st optical surface 152 Second optical surface 153 Third optical surface 154 Frame-side optical surface 155 Protrusion 156 Third Hook 160 holder 161 Holder body 162 light-emitting holes 163 1st light receiving hole 164 2nd light receiving hole 165 First Hook 169 Second hook engagement portion 172 Second Hook F Frame MZ Groove P Patch W1 First light-blocking wall W2 Second light-blocking wall W11 1st leg W21 2nd leg

Claims

1. An optical sensor positioned opposite a belt on which a patch made of toner is formed on its surface, A plate-shaped substrate having a surface facing the belt, a back surface opposite to the surface, and through holes penetrating the surface and the back surface, A holder for holding the substrate, A light-emitting element fixed to the substrate and emitting light, The substrate comprises a light-receiving element fixed to the back surface, which receives light emitted by the light-emitting element, reflected by the patch, and passing through at least a portion of the through-hole, The through-hole extends along the surface of the substrate from the position where the light-receiving element is fixed toward the position where the light-emitting element is fixed. The light-receiving element includes a first light-receiving element that receives the specular reflection component of the light reflected by the patch, and a second light-receiving element that receives the diffuse reflection component of the light reflected by the patch. The aforementioned holder is, A light-emitting hole through which light emitted from the light-emitting element passes, A first light-receiving hole for guiding the light from the light-emitting element reflected by the patch to the first light-receiving element, A second light-receiving hole for guiding the light from the light-emitting element diffused by the patch to the second light-receiving element, A first light-shielding wall located between the light-emitting element and the first light-receiving element, It has a second light-shielding wall located between the light-emitting element and the second light-receiving element, The optical sensor is characterized in that the first light-shielding wall has a groove formed on the opposing surface facing the light-emitting element.

2. The through hole includes a first hole corresponding to the first light-receiving element and a second hole corresponding to the second light-receiving element, The first hole extends from the position where the first light-receiving element is fixed toward the position where the light-emitting element is fixed. The optical sensor according to claim 1, characterized in that the second hole extends from the position where the second light-receiving element is fixed toward the position where the light-emitting element is fixed.

3. The optical sensor according to claim 1, characterized in that the groove extends in a direction along the optical axis of the light-emitting element.

4. The first hole has a first portion through which the specular reflection component of the light reflected by the patch passes, and a second portion extending in a direction intersecting the first portion. The second hole has a third portion through which the diffuse reflection component of the light reflected by the patch passes, and a fourth portion extending in a direction intersecting the third portion. The first light-shielding wall has a first leg portion that enters the second portion, The optical sensor according to claim 2, characterized in that the second light-shielding wall has a second leg portion that enters the fourth portion.

5. The light-emitting element is located on the back surface of the substrate, The optical sensor according to claim 1, characterized in that the substrate has a third hole that penetrates the front surface and the back surface, through which light emitted by the light-emitting element passes.

Images