Light emitting and receiving sensor and image forming apparatus including light emitting and receiving sensor

Abstract

To prevent a reduction in measurement accuracy caused by detection of irregularly reflected light and regularly reflected light in a mixed state, while achieving an irregularly reflected light detection system for detecting irregularly reflected light and a regularly reflected light detection system for detecting regularly reflected light, with one light emitting and receiving sensor.SOLUTION: A light emitting and receiving sensor 10 comprises a first light emitting element 14, a second light emitting element 16, a first light receiving element 15, and a second light receiving element 17, which are arranged on one face of a substrate 11 along a predetermined direction. The first light receiving element 15 receives regularly reflected light of light emitted from the first light emitting element 14. The second light receiving element 17 receives irregularly reflected light of light emitted from the second light emitting element 16. When seen from a substrate vertical direction, a first reference line L12 passing through the area center of gravity C1 of a first light emitting area 14a and the area center of gravity C2 of a first light receiving area 15a, and a second reference line L34 passing through the area center of gravity C3 of a second light emitting area 16a and the area center of gravity C4 of a second light receiving area 17a, intersect each other.SELECTED DRAWING: Figure 7A

Description

[Technical Field]

[0001] The present disclosure relates to an optical receiving and emitting sensor and an image forming apparatus including the optical receiving and emitting sensor. [Background technology]

[0002] Conventionally, a light emitting / receiving sensor has been known that includes a light emitting unit that irradiates light toward a measurement object, a light receiving unit that detects reflected light from the measurement object, and a substrate on which the light emitting unit and the light receiving unit are mounted. This type of light emitting / receiving sensor is used to measure a characteristic value of the measurement object (such as a surface concentration or a position, hereinafter referred to as a measurement object value).

[0003] An example of this type of light receiving and emitting sensor is disclosed in Patent Document 1. In this example, the light receiving and emitting sensor is used to measure the density and positional deviation of patch images formed on an intermediate transfer belt in an electrophotographic image forming apparatus or the like.

[0004] This light receiving and emitting sensor includes a first light emitting element and a second light emitting element as a light emitting section, and includes a first light receiving element and a second light receiving element as a light receiving section.

[0005] The first light receiving element is disposed at a position where it can receive specularly reflected light emitted from the first light emitting element. The first light receiving element is disposed at a position where it can receive diffusely reflected light emitted from the second light emitting element. The second light receiving element is disposed at a position where it can receive diffusely reflected light emitted from the second light emitting element. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7195808 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the light receiving and emitting sensor shown in Patent Document 1, due to various factors (for example, misalignment of the member supporting the object to be measured, etc.), specularly reflected light of light emitted from the first light emitting element may be incident on the second light receiving element provided for detecting diffusely reflected light, or specularly reflected light of light emitted from the second light emitting element may be incident on the second light receiving element provided for detecting diffusely reflected light, which may result in a decrease in the measurement accuracy of the value to be measured.

[0008] The purpose of the present disclosure is to realize a diffuse reflection light detection method that detects diffuse reflection light and a specular reflection light detection method that detects specular reflection light using a single light receiving and emitting sensor, while preventing a decrease in the measurement accuracy of the value to be measured due to the detection of a mixture of diffuse reflection light and specular reflection light. [Means for solving the problem]

[0009] A light receiving and emitting sensor according to one aspect of the present disclosure is a light receiving and emitting sensor that irradiates light toward a measurement object and detects reflected light from the measurement object, and includes a main substrate, and a first light emitting element, a second light emitting element, a first light receiving element, and a second light receiving element that are arranged along a predetermined direction on one surface of the main substrate, wherein the first light emitting element includes a first light emitting region, the second light emitting element includes a second light emitting region, the first light receiving element includes a first light receiving region, and the second light receiving element includes a second light receiving region, and the first light receiving element detects the forward and reverse directions of light emitted from the first light emitting element. The first light-receiving element is positioned at a position where it can receive diffusely reflected light emitted from the second light-emitting element, and the second light-receiving element is positioned at a position where it can receive diffusely reflected light emitted from the second light-emitting element, and when, as viewed from a substrate normal direction perpendicular to the main substrate, a straight line passing through the area center of gravity of the first light-emitting area and the area center of gravity of the first light-receiving area is defined as a first reference line, and a straight line passing through the area center of gravity of the second light-emitting area and the area center of gravity of the second light-receiving area is defined as a second reference line, each of the light-receiving elements and each of the light-emitting elements is positioned so that the first reference line and the second reference line intersect.

[0010] A light receiving and emitting sensor according to another aspect of the present disclosure is a light receiving and emitting sensor that irradiates light toward a measurement object and detects reflected light from the measurement object, and includes a main substrate, and a first light emitting element, a second light emitting element, a first light receiving element, and a second light receiving element that are arranged along a predetermined direction on one surface of the main substrate, wherein the first light emitting element includes a first light emitting region, the second light emitting element includes a second light emitting region, the first light receiving element includes a first light receiving region, and the second light receiving element includes a second light receiving region, and the first light receiving element detects a positive and negative reflection of light emitted from the first light emitting element. The first light-receiving region is positioned at a position where it can receive diffusely reflected light emitted from the second light-emitting region, and the second light-receiving region is positioned at a position where it can receive diffusely reflected light emitted from the second light-emitting region.When viewed from a substrate normal direction perpendicular to the main substrate, a straight line passing through the area center of gravity of the second light-emitting region and the area center of gravity of the second light-receiving region is defined as a second reference line, and a straight line passing through the area center of gravity of the first light-receiving region and the area center of gravity of the second light-receiving region is defined as a third reference line, the light-receiving elements and the light-emitting elements are positioned so that the second reference line and the third reference line intersect.

[0011] An image forming apparatus according to another aspect of the present disclosure includes the light receiving and emitting sensor. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to realize a diffuse reflection light detection method for detecting diffuse reflection light and a specular reflection light detection method for detecting specular reflection light using a single light receiving and emitting sensor, while preventing a decrease in the measurement accuracy of the value to be measured due to the detection of a mixture of diffuse reflection light and specular reflection light. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing an image forming apparatus equipped with a light receiving and emitting sensor according to the first embodiment. [Figure 2] FIG. 2 is an explanatory diagram for explaining the arrangement of the light receiving and emitting sensors, and is a diagram of the intermediate transfer unit as viewed from below. [Figure 3] FIG. 3 is a block diagram showing the configuration of a control system including a controller. [Figure 4]FIG. 4 is an explanatory diagram for explaining the principle of detecting black toner, where (a) shows the case where black toner is not present on the intermediate transfer belt, and (b) shows the case where black toner is present on the intermediate transfer belt. [Figure 5] Figure 5 is an explanatory diagram for explaining the principle of color toner detection, where (a) shows a case where color toner is not present on the intermediate transfer belt, and (b) shows a case where color toner is present on the intermediate transfer belt. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7A] 7A is a schematic diagram for explaining the arrangement of each light emitting and receiving element on a wiring board in the first embodiment, and corresponds to a view seen in the direction of arrow VII in FIG. [Figure 7B] FIG. 7B is a view corresponding to FIG. 7A, showing a first modification of the first embodiment. [Figure 7C] FIG. 7C is a view corresponding to FIG. 7A, showing a second modification of the first embodiment. [Figure 8] FIG. 8 is a view corresponding to FIG. 6 and showing the second embodiment. [Figure 9A] FIG. 9A is a view showing the second embodiment, corresponding to FIG. 7A. [Figure 9B] FIG. 9B is a diagram corresponding to FIG. 9A (corresponding to FIG. 7A) showing a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] The light emitting and receiving sensor of the present disclosure will be described in detail below with reference to the drawings. The light emitting and receiving sensor of the present disclosure measures a characteristic value of an object to be measured by irradiating the object with measurement light and receiving the reflected light. There are no particular limitations on the object to be measured, and the object can be a solid, semi-solid, liquid, powder, or the like. There are also no particular limitations on the characteristic value to be measured, as long as it can be analyzed from the reflected light. In the embodiment described below, an example of a light emitting and receiving sensor that is assembled into an image forming apparatus for detecting the concentration of toner used in image formation will be described.

[0015] (Embodiment 1) 1 is a schematic diagram showing an image forming apparatus 100 equipped with a light receiving and emitting sensor 10 according to this embodiment. The image forming apparatus 100 is configured as a tandem color printer.

[0016] [Overall configuration of image forming device] The image forming apparatus 100 includes a paper feed section 1, a vertical conveyance path 2, a pair of registration rollers 3, an intermediate transfer section 4, an image forming section 50, a secondary transfer section 6, a fixing device 7, a discharge conveyance path 8, a discharge tray 9, a light receiving and emitting sensor 10, and a controller 30 (FIG. 3). The image forming section 50 is equipped with four image forming mechanisms 5B, 5M, 5C, and 5Y.

[0017] The image forming apparatus 100 performs the following image forming process: Paper P is transported from a paper feed cassette 1a in a paper feed unit 1 to a vertical transport path 2 by a pickup roller 1b and a separation roller pair 1c (the roller pair on the left of the pickup roller 1b in FIG. 1), and is then transported to a secondary transfer unit 6 via a registration roller pair 3.

[0018] In the image forming unit 50, toner images of each color, yellow, cyan, magenta, and black, formed on each photosensitive drum 51 (the photosensitive drum 51 rotates counterclockwise in FIG. 1) serving as an image carrier are sequentially transferred in multiple layers onto an intermediate transfer belt 43 of the intermediate transfer unit 4 described below, forming a color image.

[0019] The color image formed here is secondarily transferred by the secondary transfer unit 6 from the intermediate transfer belt 43 onto the paper P conveyed from the paper feed cassette 1a. The color image is formed on the paper P.

[0020] Thereafter, the paper P onto which the unfixed color image has been transferred is separated from the intermediate transfer belt 43 and transported to the fixing device 7. Then, the amount of heat required for fixing is supplied to the paper P at the nip formed by the pressure contact between the fixing roller 7a and the pressure roller 7b, and the color image is fixed by further pressure being applied between the fixing roller 7a and the pressure roller 7b. After the fixing process has been completed in the fixing device 7, the paper P is discharged onto the discharge tray 9 via the discharge conveyance path 8. The fixing roller 7a has a built-in heater (not shown) that is controlled so that the surface of the fixing roller 7a reaches a predetermined temperature required for fixing.

[0021] 1, the intermediate transfer unit 4 is made up of a drive roller 41, a driven roller 42, a tension roller 44, and an endless intermediate transfer belt 43 stretched around these three rollers. The intermediate transfer belt 43 is given an appropriate tension by the tension roller 44. In this state, a driving force is transmitted to the drive roller 41 from a drive motor (not shown), so that the intermediate transfer belt 43 is driven at a feed speed equal to the surface speed of the outer periphery of the photosensitive drum 51 of each image forming mechanism 5B, 5M, 5C, and 5Y.

[0022] Next, we will explain in detail the configuration of the image forming unit 50, which is a main component of the image forming apparatus 100. The image forming unit 50 is made up of image forming mechanisms 5B, 5M, 5C, and 5Y, and four exposure devices 53 that emit laser light corresponding to each color based on image data input from a computer or the like.

[0023] The image forming mechanisms 5B, 5M, 5C, and 5Y are arranged in a line below the intermediate transfer unit 4. The image forming mechanisms 5B, 5M, 5C, and 5Y are arranged, from the upstream side in the movement direction of the intermediate transfer belt 43, for yellow (Y), cyan (C), magenta (M), and black (B), and all consist of image forming units with substantially the same configuration. Therefore, the same reference numerals are used for parts with the same configuration in the image forming mechanisms 5B, 5M, 5C, and 5Y. In the following description of the image forming mechanisms 5B, 5M, 5C, and 5Y, the identification symbols "Y," "C," "M," and "B" are omitted unless otherwise specified, and the mechanisms are simply referred to as the image forming mechanisms 5.

[0024] The image forming mechanism 5 includes a photosensitive drum 51, a charging device 52, a primary transfer member (primary transfer roller) 54, a cleaning device 55, and a developing device 56. These components are assembled into a housing made of resin or the like to form a single unit, which is attached to the main body of the image forming apparatus 100. During image formation, in each image forming mechanism 5, the peripheral surface of each photosensitive drum 51 is uniformly charged by the charging device 52, and the charged peripheral surface of the photosensitive drum 51 is irradiated with laser light corresponding to each color based on the image data. As a result, an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 51. Developer is supplied from the developing device 56 to the electrostatic latent image, forming yellow, magenta, cyan, and black toner images on the peripheral surface of each photosensitive drum 51. These toner images are transferred onto the intermediate transfer belt 43 in a superimposed state by a transfer bias applied to the primary transfer roller 54. Residual toner on the photosensitive drum 51 that was not transferred during the primary transfer is removed by the cleaning device 55.

[0025] [Layout of light receiving and emitting sensors] The light receiving and emitting sensor 10 is a registration sensor that detects registration marks r1 to r4 (see FIG. 2) formed by the image forming mechanisms 5B, 5M, 5C, and 5Y in an end region on one side in the width direction of the intermediate transfer belt 43. The registration marks r2 to r4 are marks for correcting color misregistration and are formed on the lower surface of the intermediate transfer belt 43 by the image forming mechanisms 5B, 5M, 5C, and 5Y under the control of a calibration control unit 32, which will be described later.

[0026] FIG. 2 is an explanatory diagram for explaining the arrangement of the light receiving and emitting sensors 10, and is a diagram of the intermediate transfer unit 4 as seen from below.

[0027] As shown in this figure, the light emitting and receiving sensor 10 is disposed opposite one end of the outer peripheral surface (the lower surface in this example) of the intermediate transfer belt 43 in the width direction. The light emitting and receiving sensor 10 is a reflective optical sensor that irradiates light toward the intermediate transfer belt 43, receives the reflected light (specularly reflected light and diffusely reflected light in this example), and outputs a signal (electrical signal) corresponding to the amount of reflected light received. The signal output from the light emitting and receiving sensor 10 is input to a controller 30 (described later), and the controller 30 executes calibration control (toner concentration correction processing) (described later) based on the signal received from the light emitting and receiving sensor 10. Note that the number of light emitting and receiving sensors 10 is not limited to one; for example, two light emitting and receiving sensors 10 may be disposed on both sides of the outer peripheral surface of the intermediate transfer belt 43 in the width direction.

[0028] [Control system configuration] 3 is a block diagram showing the configuration of a control system including the controller 30. The controller 30 is connected to the process device 50A, the setting operation unit 40, the light receiving and emitting sensor 10, etc. so as to be able to send and receive signals.

[0029] The process device 50A is a device necessary for the image forming process, and includes, for example, the photosensitive drum 51, the charging device 52, the exposure device 53, the developing device 56, the fixing device 7, and the like.

[0030] The setting operation unit 40 is configured so that a user can input print job execution commands and various conditions to the image forming apparatus 100 by operating it with his or her finger.

[0031] The controller 30 has, as functional units, a print control unit 31 and a calibration control unit 32. The controller 30 is made up of a microcomputer having a CPU, ROM, RAM, etc. The functions of the print control unit 31 and the calibration control unit 32 described below are realized by the CPU executing a computer program stored in the ROM, etc.

[0032] The print control unit 31 executes a print process on the paper P by controlling the process device 50A based on image data transmitted from an external terminal, for example.

[0033] The calibration control unit 32 executes calibration control at a predetermined timing, such as, but not limited to, a time period between print jobs executed by the print control unit 31.

[0034] In the calibration control, the operation of the exposure device 53 and each image forming mechanism 5 is controlled via the print control unit 31 to form four registration marks r1 to r4 (see Figure 2) for density correction in the non-print area (edge ​​area in the width direction) outside the print area on the surface of the intermediate transfer belt 43, and then the density of each of these registration marks r1 to r4 is acquired (calculated) based on the signal from the light receiving and emitting sensor 10, and the development bias, etc. is adjusted to correct the density of the toner image of each color transferred to the intermediate transfer belt 43 based on the acquired density of each of the registration marks r1 to r4.

[0035] In this example, the registration marks r1 to r4 are each made up of a rectangular patch image corresponding to each of the colors black, magenta, cyan, and yellow, and are formed in this order from the downstream side to the upstream side in the movement direction of the intermediate transfer belt 43. The letters B, M, C, and Y in Fig. 2 represent the colors of the registration marks r1 to r4, but these letters are not actually formed as images.

[0036] [Detection principle of light-emitting and receiving sensors] Next, the principle of detection of black toner and color toner by the light receiving and emitting sensor 10 will be briefly described with reference to FIGS.

[0037] 4 is an explanatory diagram for explaining the principle of detecting black toner, where (a) shows a case where black toner is not present on the intermediate transfer belt, and (b) shows a case where black toner is present on the intermediate transfer belt. In order to explain the principle, Fig. 4 shows a schematic diagram of a light-emitting element 201 that emits light, a light-receiving element 202 that receives light, and an intermediate transfer belt 203 onto which toner is transferred, separate from the actual device.

[0038] As shown in FIG. 4(a), when there is no black toner on the intermediate transfer belt 203, the light emitted from the light-emitting element 201 is specularly reflected from the surface of the intermediate transfer belt 203 and enters the light-receiving element 202. On the other hand, when there is black toner on the intermediate transfer belt 203 as shown in FIG. 4(b), a portion of the light incident on the belt 203 from the light-emitting element 201 is absorbed by the black toner, reducing the amount of specularly reflected light reflected on the intermediate transfer belt 203 and the amount of light incident on the light-receiving element 202. As a result, the magnitude of the output signal (electrical signal) output from the light-receiving element 202 also decreases. Therefore, by arranging the light-receiving element 202 in a position where it can receive the specularly reflected light of the light emitted from the light-emitting element 201, it is possible to detect the density of the black toner based on the output signal from the light-receiving element 202.

[0039] 5A and 5B are explanatory diagrams for explaining the principle of color toner detection, where (a) shows a case where color toner is not present on the intermediate transfer belt, and (b) shows a case where color toner is present on the intermediate transfer belt. In Fig. 5, a light-emitting element 301, a light-receiving element 302, and an intermediate transfer belt 303 are shown schematically, separate from the actual device.

[0040] In the example of Fig. 5, the position of the light receiving element 302 is different from that in the case of detecting black toner (in the case of Fig. 4). That is, the light receiving element 302 is disposed at a position where it can receive diffusely reflected light from color toner (in the example of this figure, it is disposed closer to the light emitting element 301 than the position where it can receive specularly reflected light).

[0041] 5(a), when there is no color toner on the intermediate transfer belt 303, the light emitted from the light-emitting element 301 is specularly reflected from the surface of the intermediate transfer belt 303, but the output signal of the light-receiving element 302 does not change because the light-receiving element 302 is not located beyond the point of this specularly reflected light. On the other hand, when there is color toner on the intermediate transfer belt 303 as shown in FIG. 5(b), part of the light incident on the intermediate transfer belt 303 from the light-emitting element 301 is diffusely reflected by the color toner and enters the light-receiving element 302. Therefore, by placing the light-receiving element 302 at a position away from the specular reflection position and at a position where it can receive the diffusely reflected light, it is possible to detect the density of the color toner based on the output signal of the light-receiving element 302.

[0042] [Details of the light receiving and emitting sensor] The light receiving and emitting sensor 10 mounted on the image forming apparatus 100 is configured to be able to detect the density of black toner and the density of color toner based on the above-mentioned detection principle.

[0043] A specific configuration of the light receiving and emitting sensor 10 will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 2. The left side of Fig. 6 corresponds to the front side of the image forming apparatus 100 (hereinafter referred to as the front side of the apparatus), and the right side of Fig. 6 corresponds to the rear side of the image forming apparatus 100 (hereinafter referred to as the rear side of the apparatus).

[0044] The light receiving and emitting sensor 10 includes a wiring board 11, a first element substrate 12A and a second element substrate 12B fixed to a main surface (one surface) of the wiring board 11, a first light emitting element 14 and a first light receiving element 15 formed on the first element substrate 12A, a second light emitting element 16 and a second light receiving element 17 formed on the second element substrate 12B, a housing 18 attached to the main surface of the wiring board 11 to form an element accommodating space S, and a lens unit 19 supported by the housing 18. In this example, the first light emitting element 14 and the second light emitting element 16 are configured as light emitting diodes (LEDs), and the first light receiving element 15 and the second light receiving element 17 are configured as photodiodes (PDs).

[0045] In the following, first, each component constituting the light receiving and emitting sensor 10 will be described, and then the arrangement and configuration of the four elements 14 to 17 will be described in detail.

[0046] The wiring board 11 is electrically connected to the controller 30 and applies a bias voltage to the light-emitting elements 14, 16 and the light-receiving elements 15, 17. In this example, the wiring board 11 is formed in a rectangular shape that is long in a predetermined direction (the left-right direction in FIG. 6, which is the main scanning direction in this example). The wiring board 11 is made of, for example, a resin substrate or a ceramic substrate. Note that the wiring board 11 is not limited to a rectangular shape and may have any shape, such as a circular shape or a diamond shape.

[0047] The first element substrate 12A and the second element substrate 12B are formed of, for example, semiconductor substrates and are mounted (laminated) on the main surface of the wiring substrate 11. The first element substrate 12A and the second element substrate 12B are disposed adjacent to each other along the surface direction (parallel to the main surface) of the main surface of the wiring substrate 11. In this example, the semiconductor substrate is formed of a Si (silicon) substrate. The first element substrate 12A and the second element substrate 12B are both rectangular in shape and elongated in the predetermined direction (see FIG. 7A). A slight gap is provided between the first element substrate 12A and the second element substrate 12B. That is, the first element substrate 12A and the second element substrate 12B are disposed separated by a slit-shaped recess with a U-shaped cross section that opens toward the intermediate transfer belt 43. The first element substrate 12A and the second element substrate 12B are not limited to being rectangular, and may be any shape, such as a circle or a diamond.

[0048] The first light-emitting element 14 and the first light-receiving element 15 are formed on the surface of the first element substrate 12A opposite to the side facing the wiring substrate 11. The first light-emitting element 14 and the first light-receiving element 15 are an element pair provided to detect black toner, and their positions are set based on the above-mentioned black toner detection principle (see FIG. 4).

[0049] That is, the first light-emitting element 14 is disposed so as to emit light toward a predetermined measurement irradiation position M on the intermediate transfer belt 43, and the first light-receiving element 15 is disposed at a position where it can receive specularly reflected light of the light emitted from the first light-emitting element 14. When viewed from the direction perpendicular to the substrate, the measurement irradiation position M is located at the center of a line segment connecting the area centroid position C2 of the first light-receiving region 15a of the first light-receiving element 15 (see FIG. 7A described later) and the area centroid position C1 of the first light-emitting region 14a of the first light-emitting element 14.

[0050] The second light-emitting element 16 and the second light-receiving element 17 are formed on the surface of the second element substrate 12B opposite to the wiring substrate 11. The second light-emitting element 16 and the second light-receiving element 17 are an element pair provided to detect color toner, and their positions are set based on the above-mentioned color toner detection principle (see FIG. 5).

[0051] That is, the second light-emitting element 16 is positioned to emit light toward the measurement irradiation position M, and the second light-receiving element 17 is positioned so as to receive the diffusely reflected light of the light emitted from the second light-emitting element 16.

[0052] Furthermore, the second light receiving element 17 is disposed at a position where it does not detect specularly reflected light of light emitted from the second light emitting element 16. Specifically, in this example, the second light receiving element 17 is disposed on the second light emitting element 16 side (the right side in FIG. 6) of a line that passes through the measurement illuminated position M and extends in the vertical direction. In other words, the second light receiving element 17 is disposed on the opposite side (the right side in FIG. 6) of the measurement illuminated position M from the specular reflection side of light emitted from the second light emitting element 16.

[0053] Moreover, the second light receiving element 17 is disposed at a position where it does not detect specularly reflected light of light emitted from the first light emitting element 14. Specifically, in this example, the second light receiving element 17 is disposed on the side of the first light emitting element 14 opposite to the side where the first light receiving element 15 that receives the specularly reflected light is located (the specular reflection side of light).

[0054] Referring to Figure 6, the distance between the second light-emitting element 16 and the measurement illuminated position M (more specifically, the distance along the light emission direction of the second light-emitting element 16) is longer than the distance between the first light-emitting element 14 and the measurement illuminated position M (more specifically, the distance along the light emission direction of the first light-emitting element 14).

[0055] The first light-emitting element 14 and the second light-emitting element 16 are each composed of, for example, a plurality of semiconductor layers. The plurality of semiconductor layers are formed by epitaxial growth on a semiconductor substrate (the first element substrate 12A or the second element substrate 12B) using, for example, an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus. The first light-receiving element 15 and the second light-receiving element 17 are each composed of an n-type semiconductor substrate (the first element substrate 12A or the second element substrate 12B) with a p-type semiconductor region provided thereon, thereby forming a p-n junction at the interface therebetween.

[0056] The lens unit 19 has a first light-emitting side lens 191, a first light-receiving side lens 192, a second light-emitting side lens 193, and a second light-receiving side lens 194, and a lens support member 190 that supports these four lenses 191 to 194 and is fixed to the housing 18. The lens support member 190 may be fixed to the wiring board 11 via a support pillar or the like that extends toward the wiring board 11.

[0057] The first light-emitting side lens 191 condenses the light emitted from the first light-emitting element 14 and guides it to the irradiation position M for measurement.

[0058] The first light receiving side lens 192 collects light emitted from the first light emitting element 14 and specularly reflected at the measurement irradiation position M, and guides the light to the first light receiving element 15 (more specifically, the first light receiving region 15a of the first light receiving element 15).

[0059] The second light-emitting side lens 193 condenses the light emitted from the second light-emitting element 16 and guides it to the irradiation position M for measurement.

[0060] The second light receiving side lens 194 collects the light emitted from the second light emitting element 16 and diffusely reflected at the measurement irradiation position M, and guides it to the second light receiving element 17 (more specifically, the second light receiving region 17a of the second light receiving element 17).

[0061] These lenses 191 to 194 are configured by, for example, convex lenses, spherical lenses, aspherical lenses, etc. It should be noted that the lenses 191 to 194 are not necessarily required.

[0062] The housing 18 prevents unintended light (stray light) from being received by the light receiving elements 15, 17. Specifically, the housing 18 has a peripheral wall portion 18a, a lid portion 18b, a first light-shielding wall 18c, and a second light-shielding wall 18d. In this example, the housing 18 is integrally molded from, for example, a resin material. The housing 18 may also be formed by combining multiple members.

[0063] Peripheral wall 18a is a frame-shaped member that surrounds an element accommodating space S that accommodates elements 14 to 17. An opening on one end of peripheral wall 18a is closed by wiring board 11, and an opening on the other end is closed by lid 18b. Thus, lid 18b, wiring board 11, and peripheral wall 18a form element accommodating space S.

[0064] The first light-shielding wall 18c and the second light-shielding wall 18d are provided to protrude from the surface of the lid portion 18b facing the wiring board 11.

[0065] The first light-shielding wall 18c is disposed so as to block the space between the first light-emitting element 14 and the first light-receiving element 15 when viewed from a direction (a direction perpendicular to the plane of the paper in FIG. 6) orthogonal to the arrangement direction (predetermined direction) of the four elements 14 to 17. In this way, the first light-shielding wall 18c prevents a portion of the light emitted from the first light-emitting element 14 from being directly detected by the first light-receiving element 15. The first light-shielding wall 18c also functions as a guide wall that guides the emitted light from the first light-emitting element 14 and the specularly reflected light of the emitted light. Further guide walls may be added along the light guide paths of the emitted light and the specularly reflected light.

[0066] The second light-shielding wall 18d is disposed so as to block the space between the second light-emitting element 16 and the second light-receiving element 17 when viewed from a direction (a direction perpendicular to the plane of the paper in FIG. 6) orthogonal to the arrangement direction (predetermined direction) of the four elements 14 to 17. In this way, the second light-shielding wall 18d prevents a portion of the light emitted from the second light-emitting element 16 from being directly detected by the second light-receiving element 17. The second light-shielding wall 18d also functions as a guide wall that guides the emitted light from the second light-emitting element 16 and the diffusely reflected light of the emitted light. Further guide walls may be added to the light guide paths of the emitted light and the diffusely reflected light.

[0067] [Emission control of each light-emitting element] Next, a detailed description will be given of the light emission control of the light emitting elements 14, 16 provided in the light receiving and emitting sensor 10. The light emission control of the light emitting elements 14, 16 is realized by the function of the calibration control section 32 of the controller 30.

[0068] When performing the calibration control, the calibration control unit 32 selectively causes the first light-emitting element 14 for detecting black toner or the second light-emitting element 16 for detecting color toner to emit light depending on the timing at which each of the registration marks r1 to r4 passes through the measurement irradiation position M directly above the light-emitting and receiving sensor 10.

[0069] Specifically, the calibration control unit 32 causes only the first light-emitting element 14 to emit light at the time when the black registration mark r1 passes through the measurement irradiation position M and before and after that time, and acquires (calculates) the density of the black registration mark r1 based on the magnitude of the output signal output from the first light-receiving element 15 after the emission.

[0070] On the other hand, the calibration control unit 32 causes only the second light-emitting element 16 to emit light at the timing when the registration marks r2 to r4 of a color other than black (in this example, yellow, magenta, or cyan) pass through the measurement irradiation position M and before and after that, and acquires (calculates) the density of the registration marks r2 to r4 corresponding to each of the colors yellow, magenta, and cyan based on the magnitude of the output signal output from the second light-receiving element 17 after the emission.

[0071] [Details of the arrangement of light-emitting and light-receiving elements] FIG. 7A is a schematic diagram for explaining the arrangement of elements 14 to 17 on wiring board 11, and corresponds to the view seen in the direction of arrow VII in FIG.

[0072] 7A shows the outer edges of the first and second light-receiving regions 15a and 17a, which are the light-receiving regions of the first and second light-receiving elements 15 and 17, respectively, and the outer edges of the first and second light-emitting regions 14a and 16a, which are the light-emitting regions of the first and second light-emitting elements 14 and 16, respectively. Here, the "light-emitting region" refers to the portion of the light-emitting element that emits light, and the "light-receiving region" refers to the portion of the light-receiving element that receives light. In this example, the outer edges of the first and second light-receiving elements 15 and 17 and the outer edges of the first and second light-receiving regions 15a and 17a are aligned, but this is not necessarily required. Furthermore, the outer edges of the first and second light-emitting elements 14 and 16 and the outer edges of the first and second light-emitting regions 14a and 16a are aligned, but this is not necessarily required. 7A, the shape of each of the light-receiving regions 15a, 17a and each of the light-emitting regions 14a, 16a is depicted as a simplified square, but is not limited to a square and the aspect ratio can be changed in various ways. Furthermore, the shape of each of the light-receiving regions 15a, 17a and each of the light-emitting regions 14a, 16a is not limited to a rectangular shape and may be, for example, a circular shape or a diamond shape.

[0073] The first light receiving element 15, the first light emitting element 14, the second light receiving element 17, and the second light emitting element 16 are arranged in this order from one side to the other side in the longitudinal direction of the wiring board 11 (a predetermined direction, which in this example is the main scanning direction).

[0074] The first light-emitting element 14 and the first light-receiving element 15 are arranged near both ends in the longitudinal direction of the first element substrate 12A. A pair of bonding pads 21 for connecting bonding wires is formed on both sides of the first light-emitting element 14 in the substrate width direction of the first element substrate 12A. The pair of bonding pads 21 are electrically connected to the first light-emitting element 14.

[0075] The second light-emitting element 16 and the second light-receiving element 17 are arranged near both ends in the longitudinal direction of the second element substrate 12B. A pair of bonding pads 22 for connecting bonding wires is formed on both sides in the substrate width direction of the second light-emitting element 16 on the second element substrate 12B. The pair of bonding pads 22 is electrically connected to the second light-emitting element 16.

[0076] Incidentally, when forming each of the elements 14 to 17 on a semiconductor substrate (element substrates 12A and 12B) as in this embodiment, the following steps are repeated: a film formation process for forming a thin film on the semiconductor substrate; a photolithography process for applying photoresist to the thin film and then exposing it to light using a photomask to form a resist pattern; a development process for the exposed photoresist; and an etching process for removing areas other than the areas protected by the photoresist remaining after the development process.

[0077] In this embodiment, the photolithography process comprises a process of forming a set of resist patterns for the first light-emitting element 14 and the first light-receiving element 15 on the first element substrate 12A using the same photomask, and a process of forming a set of resist patterns for the second light-emitting element 16 and the second light-receiving element 17 on the second element substrate 12B using the same photomask.

[0078] Therefore, in this embodiment, a straight line passing through the areal centroid positions C1 and C2 of the first light-emitting element 14 and the first light-receiving element 15 formed using the same photomask is defined as a first reference line L12 (see FIG. 7A). Furthermore, in this embodiment, a straight line passing through the areal centroid positions C3 and C4 of the second light-emitting element 16 and the second light-receiving element 17 formed using the same photomask is defined as a second reference line L34, which serves as a reference line for defining the design positional relationship relative to the first reference line L12. Here, the areal centroid positions C1, C2, C3, and C4 refer to the centroid positions of the areas defined by the outer edges of the first light-emitting region 14a, the first light-receiving region 15a, the second light-emitting region 16a, and the second light-receiving region 17a when viewed from the vertical direction of the wiring substrate 11 (hereinafter referred to as the substrate vertical direction), and are geometric centroid positions of the areas that can be determined without considering the mass distribution within the areas.

[0079] In the light receiving and emitting sensor 10 of this embodiment, as shown in FIG. 7A, the elements 14 to 17 are arranged so that the first reference line L12 and the second reference line L34 intersect when viewed from the direction perpendicular to the substrate.

[0080] In this embodiment, when viewed from the substrate perpendicular direction, the center line in the width direction of the first element substrate 12A coincides with the center line in the width direction of the wiring substrate 11. On the other hand, the center line in the width direction of the second element substrate 12B intersects with the center line in the width direction of the wiring substrate 11. Here, the center line in the width direction is a straight line that passes through the center position in the width direction.

[0081] In other words, when viewed from the substrate perpendicular direction, the first element substrate 12A is arranged so that its extension direction is parallel to the extension direction of the wiring substrate 11 (main substrate), whereas the second element substrate 12B is arranged so that its extension direction is slightly inclined relative to the extension direction of the wiring substrate 11.

[0082] That is, the second element substrate 12B is disposed so that its extending direction intersects with the extending direction of the first element substrate 12A when viewed in the direction perpendicular to the substrate.

[0083] Here, the extending direction of each of the substrates 11, 12A, and 12B is the direction in which the center line in the width direction of each substrate extends, and in this example, it coincides with the extending direction of the long side of the substrate. The center line in the width direction of the first element substrate 12A and the first reference line L12 coincide when viewed from the direction perpendicular to the substrate, and the center line in the width direction of the second element substrate 12B and the second reference line L34 coincide when viewed from the direction perpendicular to the substrate. Therefore, as described above, by arranging the second element substrate 12B at an inclination, the first reference line L12 and the second reference line L34 intersect when viewed from the direction perpendicular to the substrate.

[0084] As a result, in the direction orthogonal to the first reference line L12 (the vertical direction in FIG. 7A), the area centroid position C4 of the second light-receiving region 17a of the second light-receiving element 17 and the area centroid position C3 of the second light-emitting region 16a of the second light-emitting element 16 can be arranged to be separated from each other.

[0085] Furthermore, in the present embodiment, when the distance (hereinafter referred to as the first separation distance) between the area centroid position C1 of the first light-emitting region 14a of the first light-emitting element 14 and the area centroid position C2 of the first light-receiving region 15a of the first light-receiving element 15 is defined as K1, and the distance (hereinafter referred to as the second separation distance) between the area centroid position C3 of the second light-emitting region 16a of the second light-emitting element 16 and the area centroid position C4 of the second light-receiving region 17a of the second light-receiving element 17 is defined as K2, for example, the relationship of K1 = K2 is satisfied.

[0086] Also, when the distance (hereinafter referred to as the third separation distance) between the area centroid position C1 of the first light-emitting region 14a of the first light-emitting element 14 and the area centroid position C4 of the second light-receiving region 17a of the second light-receiving element 17 is defined as K3 when viewed from the direction perpendicular to the wiring substrate 11, the relationship of K3 < K1 (= K2) is satisfied. Note that the magnitude relationship among K1, K2, and K3 is not limited to this, and for example, K2 > K1 may be set.

[0087] [Operational Effects] In the light receiving and emitting sensor 10 of this embodiment configured as described above, the first light receiving element 15, the first light emitting element 14, the second light receiving element 17, and the second light emitting element 16 are arranged in this order along a predetermined direction on one surface of the wiring board 11. The first light receiving element 15 is arranged in a position where it can receive specularly reflected light of light emitted from the first light emitting element 14, and the second light receiving element 17 is arranged in a position where it can receive diffusely reflected light of light emitted from the second light emitting element 16.

[0088] As a result, the first light receiving element 15 receives the specularly reflected light emitted from the first light emitting element 14, and the second light receiving element 17 receives the diffusely reflected light emitted from the second light emitting element 16, making it possible to detect reflected light according to the light reflection characteristics of the toner, which is the measurement object B. This allows the light receiving and emitting sensor 10 to accurately measure the density of color toner, which has the property of easily reflecting light diffusely, and the density of black toner, which has the property of absorbing light and has a strong correlation with the amount of specularly reflected light on the surface of the intermediate transfer belt 43.

[0089] Furthermore, according to the arrangement order of the elements 14-17 in this embodiment, the second light-emitting element 16, which is the source of the diffusely reflected light detected by the second light-receiving element 17, is arranged at the outermost position (the rear side of the device in this example) in the arrangement direction (predetermined direction) of the elements 14-17. This allows the incident angle θ1 (see FIG. 6 ) of light incident from the second light-emitting element 16 onto the measurement irradiation position M to be maximized. Generally, the greater the incident angle of light, the weaker the specularly reflected light. Therefore, even if specularly reflected light from the second light-emitting element 16 is incident on the second light-receiving element 17 due to, for example, deformation of the intermediate transfer belt 43, the intensity of the light can be minimized. Therefore, even if specularly reflected light from the second light-receiving element 17 is mixed in with the light components detected by the second light-receiving element 17, the influence of this light can be minimized. This improves the accuracy of density measurement of the color registration marks r2-4 based on the output signal of the second light-receiving element 17. Furthermore, by increasing the incident angle θ1 of the light incident from the second light-emitting element 16 onto the measurement irradiation position M, the specular reflection component is reduced and the diffuse reflection component contained in the reflected light can be relatively increased. Consequently, the difference in the diffuse reflection characteristics according to the density of the color toner (an example of the measurement object B) can be fully reflected in the amount of light received by the second light-receiving element 17, thereby improving the accuracy of density measurement of the color registration marks r2 to r4 based on the output signal of the second light-receiving element 17.

[0090] Furthermore, according to the arrangement order of the elements 14 to 17 of this embodiment, the second light receiving element 17 is arranged on the side opposite to the first light receiving element 15 (the side where light emitted from the first light emitting element 14 is specularly reflected) relative to the first light emitting element 14, so that specularly reflected light of light emitted from the first light emitting element 14 can be prevented from entering the second light receiving element 17. This makes it possible to minimize the mixing of specularly reflected light of light emitted from the first light emitting element 14 with the light components received by the second light receiving element 17 for detecting diffusely reflected light. This in turn makes it possible to maximize the accuracy of density measurement of the color registration marks r2 to r4 based on the output signal of the second light receiving element 17.

[0091] Furthermore, in this embodiment, the elements 14 to 17 are arranged so that the first reference line L12 and the second reference line L34 intersect, and therefore, in a direction perpendicular to the first reference line L12 (the up and down direction in Figure 7A), the area center of gravity position C4 of the second light receiving region 17a of the second light receiving element 17 and the area center of gravity position C3 of the second light emitting region 16a of the second light emitting element 16 can be positioned apart from each other.

[0092] Therefore, when viewed from the substrate perpendicular direction, if the direction along the first reference line L12 is the specular reflection direction of the light emitted from each of the light-emitting elements 14 and 16, the second light-receiving element 17 is disposed at a position offset from the second light-emitting element 16 in a direction perpendicular to the specular reflection direction when viewed from the substrate perpendicular direction (see FIG. 7A). This makes it difficult for the second light-receiving element 17 to receive specularly reflected light emitted from the second light-emitting element 16. This makes it possible to prevent specularly reflected light from the second light-emitting element 16 from being mixed into the light component received by the second light-receiving element 17. This in turn improves the accuracy of measuring the density of color toner based on the output signal of the second light-emitting element 16.

[0093] In addition, in this embodiment, the light receiving and emitting sensor 10 has a first element substrate 12A and a second element substrate 12B that are stacked on the wiring board 11 and are arranged adjacent to each other in the specified direction, and the first light receiving element 15 and the first light emitting element 14 are provided on the first element substrate 12A, and the second light receiving element 17 and the second light emitting element 16 are provided on the second element substrate 12B.

[0094] According to this configuration, the first light receiving element 15 and the first light emitting element 14 are integrally formed on the first element substrate 12A, and the second light receiving element 17 and the second light emitting element 16 are integrally formed on the second element substrate 12B, and then the fixing positions of the first element substrate 12A and the second element substrate 12B relative to the wiring substrate 11 are adjusted separately, thereby making it possible to easily adjust the degree of intersection between the first reference line L12 and the second reference line L34.

[0095] Furthermore, in this embodiment, when viewed from the substrate perpendicular direction, the first element substrate 12A is arranged so that its extension direction is parallel to the first reference line L12 and coincides with the extension direction of the wiring substrate 11 (the specified direction), and the second element substrate 12B is arranged so that its extension direction is parallel to the second reference line L34 and is inclined with respect to the extension direction of the wiring substrate 11 (see Figure 7A), so that the elements 14 to 17 are arranged so that the first reference line L12 and the second reference line L34 intersect.

[0096] This facilitates manufacturing because the first reference line L12 and the second reference line L34 can be made to intersect by tilting the extension direction of the second element substrate 12B, on which the second light receiving element 17 and the second light emitting element 16 are formed, with respect to the extension direction of the wiring substrate 11 (the predetermined direction in this example). Moreover, by simply reusing an existing photomask and changing its installation angle, the elements 14 to 17 can be formed so that the first reference line L12 and the second reference line L34 intersect, thereby reducing manufacturing costs compared to when a new photomask is prepared.

[0097] In addition, in this embodiment, when viewed from the direction perpendicular to the substrate, a straight line passing through the area center of gravity C1 of the first light-emitting region 14a of the first light-emitting element 14 and the area center of gravity C2 of the first light-receiving region 15a of the first light-receiving element 15 is defined as a first reference line L12, and a straight line passing through the area center of gravity C3 of the second light-emitting region 16a of the second light-emitting element 16 and the area center of gravity C4 of the second light-receiving region 17a of the second light-receiving element 17 is defined as a second reference line L34, thereby specifying the positional relationship of each element 14 to 17, and manufacturing is made even easier based on such positional relationships.

[0098] That is, in this embodiment, when the first light-emitting element 14 and the first light-receiving element 15 are formed on the first element substrate 12A, the resist patterns for the elements 14 and 15 are formed using the same photomask, and when the second light-emitting element 16 and the second light-receiving element 17 are formed on the second element substrate 12B, the resist patterns for the elements 16 and 17 are formed using the same photomask. Therefore, by defining the lines passing through the areal centers of gravity of a pair of elements formed using the same photomask as the first reference line L12 and the second reference line L34, respectively, the positional relationship of the elements 14 to 17 can be defined in accordance with the characteristics of the manufacturing method, thereby facilitating manufacturing.

[0099] (Modification 1 of Embodiment 1) 7B is a view corresponding to FIG. 7A illustrating Modification 1 of Embodiment 1. Modification 1 differs from Embodiment 1 in that the position of the second light-emitting element 16 on the second element substrate 12B is shifted from the center position in the width direction so that the first reference line L12 and the second reference line L34 intersect.

[0100] That is, in this modification 1, the second light-emitting element 16 is disposed at a position offset in the width direction (vertical direction in FIG. 7B) from the center line (in this example, collinear with the first reference line L12) of the second element substrate 12B in the width direction (vertical direction in FIG. 7B). As a result, the first reference line L12 and the second reference line L34 intersect when viewed from the substrate perpendicular direction.

[0101] As a result of the first reference line L12 and the second reference line L34 intersecting in this manner, the area center of gravity position C4 of the second light receiving element 17 and the area center of gravity position C3 of the second light emitting element 16 are spaced apart in the direction perpendicular to the first reference line L12 (the up-down direction in FIG. 7B ). Therefore, the same effect as in the first embodiment (the effect that the second light receiving element 17 is less likely to receive specularly reflected light from the second light emitting element 16) can be obtained.

[0102] In summary, in this modification, when viewed from the substrate perpendicular direction, the first element substrate 12A is disposed so that its extension direction is parallel to the first reference line L12 and coincides with the extension direction of the wiring substrate 11 (the predetermined direction in this example). The second element substrate 12B is disposed so that its extension direction coincides with the extension direction of the wiring substrate 11 (the predetermined direction in this example). In addition, in a direction perpendicular to the extension direction of the second element substrate 12B, the area centroid C4 of the second light-receiving region 17a of the second light-receiving element 17 is at a different position from the area centroid C3 of the second light-emitting region 16a of the second light-emitting element 16. As a result, the first reference line L12 and the second reference line L34 intersect. The intersection of the first reference line L12 and the second reference line L34 provides the same advantageous effects as those of the first embodiment. Moreover, in this modified example, there is no need to position the second element substrate 12B at an angle with respect to the extension direction of the wiring substrate 11 as in the first embodiment, so the configuration of the manufacturing jig and manufacturing machine can be simplified, and ultimately the manufacturing cost can be reduced as much as possible.

[0103] (Modification 2 of Embodiment 1) 7A and illustrates a modified example 2 of embodiment 1. Modification example 2 differs from embodiment 1 and modification example 1 in that the second element substrate 12B is tilted and the position of the second light-emitting element 16 on the second element substrate 12B is shifted from the center position in the width direction so that the first reference line L12 and the second reference line L34 intersect.

[0104] 7C , in the present modification 2, the light receiving and emitting sensor 10 employs a configuration that combines the above-described Embodiment 1 and Modification 1. As can be seen from Fig. 7C , in the present modification 2, by combining the configuration of the above-described Embodiment 1 (configuration in which the extension direction of the second element substrate 12B is tilted with respect to the extension direction of the wiring substrate 11) with the configuration of Modification 1 (configuration in which the positions of the area centers of gravity C3, C4 of the second light emitting element 16 and the second light receiving element 17 in the direction perpendicular to the extension direction of the second element substrate 12B are made different), the intersection angle between the first reference line L12 and the second reference line L34 can be increased compared to the above-described Embodiment 1 and Modification 1.

[0105] As a result, it is possible to increase the distance between the area center of gravity C4 of the second light receiving element 17 and the area center of gravity C3 of the second light emitting element 16 in the direction perpendicular to the first reference line L12 (the up-down direction in FIG. 7C ). Therefore, the same effect as in the first embodiment and the first modification (the effect that the second light receiving element 17 is less likely to receive specularly reflected light from the second light emitting element 16) can be more reliably obtained.

[0106] To summarize, in this modification, not only is the extension direction of the second element substrate 12B tilted with respect to the extension direction of the wiring substrate 11, but the positions of the area centroid C4 of the second light receiving region 17a of the second light receiving element 17 and the area centroid C3 of the second light emitting region 16a of the second light emitting element 16 in the direction perpendicular to the extension direction of the second element substrate 12B are different from each other. This makes it possible to increase the intersection angle between the first reference line L12 and the second reference line L34 compared to the first embodiment and modification 1. This makes it possible to more reliably obtain the same effects as the first embodiment and modification 1.

[0107] (Embodiment 2) 8 and 9A are views corresponding to FIGS. 6 and 7A, respectively, illustrating a second embodiment. This embodiment differs from the first embodiment in that the elements 14 to 17 are mounted on the wiring board 11 via a single element substrate 13, and in the arrangement of the elements 14 to 17. The other configurations are the same as those of the first embodiment. In FIGS. 8 and 9A, the same components as those in FIGS. 6 and 7A are designated by the same reference numerals, and their description will be omitted as appropriate.

[0108] That is, in the first embodiment, the first light-emitting element 14 and the first light-receiving element 15 are formed on the first element substrate 12A, and the second light-emitting element 16 and the second light-receiving element 17 are formed on the second element substrate 12B, whereas in the present embodiment, the first light-receiving element 15, the first light-emitting element 14, the second light-receiving element 17, and the second light-emitting element 16 are all formed on the same single element substrate 13.

[0109] Here, when forming the elements 14 to 17 on the semiconductor substrate, the film forming step, photolithography step, development step, and etching step are repeated as described above.

[0110] In this case, when each element 14 to 17 is formed on one element substrate 13 (semiconductor substrate) as in this embodiment, the photolithography process consists of a process of forming a set of resist patterns for the first light receiving element 15 and the second light receiving element 17 using the same photomask, and a process of forming a set of resist patterns for the first light emitting element 14 and the second light emitting element 16 using the same photomask.

[0111] In this embodiment, a third reference line L24 is defined as a line passing through the areal centroids C2 and C4 of the first light-receiving region 15a of the first light-receiving element 15 and the second light-receiving region 17a of the second light-receiving element 17, which are formed using the same photomask. In this embodiment, a second reference line L34 and a first reference line L12 are defined as reference lines that define the design positional relationship relative to the third reference line L24. The second reference line L34 is a line passing through the areal centroid C3 of the second light-emitting region 16a of the second light-emitting element 16 and the areal centroid C4 of the second light-receiving region 17a of the second light-receiving element 17, and the first reference line L12 is a line passing through the areal centroid C1 of the first light-emitting region 14a of the first light-emitting element 14 and the areal centroid C2 of the first light-receiving region 15a of the first light-receiving element 15.

[0112] In this embodiment, when viewed from the substrate perpendicular direction, the second light-emitting element 16 is disposed at a position offset from the third reference line L24 to one side in the substrate width direction (the lower side in FIG. 9A ) as viewed from the substrate perpendicular direction. As a result, when viewed from the substrate perpendicular direction, the second reference line L34 intersects with the third reference line L24. Note that in this embodiment, when viewed from the substrate perpendicular direction, the first reference line L12 is positioned on the same straight line as the third reference line L24.

[0113] [Action and effect] As described above, in this embodiment, the element substrate 13 is formed as a single piece, so that positioning errors during fixing can be reduced compared to when two element substrates 12A and 12B are fixed to the wiring substrate 11 as in the first embodiment. Therefore, deviations in the positional relationship between the elements 14 to 17 can be suppressed.

[0114] Furthermore, in this embodiment, the third reference line L24 and the second reference line L34 intersect when viewed from the substrate vertical direction, so that in a direction perpendicular to the third reference line L24 (the up and down direction in Figure 9A), the area center of gravity position C4 of the second light receiving area 17a of the second light receiving element 17 and the area center of gravity position C3 of the second light emitting area 16a of the second light emitting element 16 can be positioned apart from each other.

[0115] Therefore, when viewed from the substrate perpendicular direction, if the direction along the third reference line L24 is the specular reflection direction of the light emitted from each of the light-emitting elements 14 and 16, the second light-receiving element 17 is disposed at a position offset from the second light-emitting element 16 in a direction perpendicular to the specular reflection direction (see FIG. 9A ). This makes it difficult for the second light-receiving element 17 to receive specularly reflected light emitted from the second light-emitting element 16. This makes it possible to prevent specularly reflected light emitted from the second light-emitting element 16 from being mixed into the light component received by the second light-receiving element 17. This in turn improves the accuracy of measuring the density of color toner based on the output signal of the second light-emitting element 16.

[0116] Furthermore, in this embodiment, the first light receiving element 15, the first light emitting element 14, the second light receiving element 17, and the second light emitting element 16 are formed on one element substrate 13, and the element substrate 13 is fixed to the wiring substrate 11, so that positioning errors during fixing can be reduced compared to when two element substrates 12A and 12B are fixed to the wiring substrate 11 as in the first embodiment. Therefore, deviations in the positional relationship between the elements 14 to 17 can be suppressed.

[0117] Furthermore, in this embodiment, when viewed from the direction perpendicular to the substrate, a straight line passing through the area center of gravity C1 of the first light-emitting region 14a of the first light-emitting element 14 and the area center of gravity C2 of the first light-receiving region 15a of the first light-receiving element 15 is defined as a first reference line L12, and each element 14 to 17 is arranged so that the first reference line L12 is parallel to (coincides with) the third reference line L24.

[0118] According to this configuration, when viewed from the substrate perpendicular direction, if the direction along the third reference line L24 is the direction of specular reflection of light emitted from each of the light-emitting elements 14 and 16, the first light-receiving element 15 is disposed in the direction of specular reflection of light emitted from the first light-emitting element 14. This makes it easier for the first light-receiving element 15 to receive specularly reflected light emitted from the first light-emitting element 14. Therefore, it is possible to ensure sufficient accuracy in measuring the concentration of black toner based on the output signal of the first light-receiving element 15.

[0119] Furthermore, in this embodiment, as viewed from the direction perpendicular to the substrate, a straight line passing through the area center position C2 of the first light receiving area 15a of the first light receiving element 15 and the area center position C4 of the second light receiving area 17a of the second light receiving element 17 is defined as the third reference line L24, as described above, to specify the positional relationship of each element 14 to 17, and manufacturing is facilitated based on such a positional relationship.

[0120] That is, in this embodiment, when the first light receiving element 15 and the second light receiving element 17 are formed on the element substrate 13, the same photomask is used to form resist patterns for the elements 15, 17. Therefore, by defining a straight line passing through the areal centroid positions C2, C4 of the light receiving regions 15a, 17a of the pair of elements 15, 17 formed using the same photomask as described above as the third reference line L24 and defining the positional relationship between the first reference line L12 and the second reference line L34 based on the third reference line L24, it is possible to define the positional relationship between the elements 14 to 17 in accordance with the characteristics of the manufacturing method, thereby facilitating manufacturing.

[0121] (Modification of the second embodiment) 9B is a diagram equivalent to FIG. 9A, showing Modification 1 of Embodiment 2. This modification differs from Embodiment 2 in that the first reference line L12 intersects with the third reference line L24. Except for this difference, the other configurations are the same as those of Embodiment 2. In FIG. 9B, the same elements as those in FIG. 9A are denoted by the same reference numerals, and their description will be omitted as appropriate.

[0122] That is, in this modification, the first light-emitting element 14 is disposed at a position offset to one side in the substrate width direction from the third reference line L24, similar to the second light-emitting element 16. As a result, when viewed from the substrate perpendicular direction, the first reference line L12 passing through the area centroid position C1 of the first light-emitting element 14 and the area centroid position C2 of the first light-receiving element 15 intersects with the third reference line L24.

[0123] In this embodiment, the first light-emitting element 14 and the second light-emitting element 16 have the same offset direction (both downward in FIG. 9B ) and offset amount relative to the third reference line L24. In other words, the first reference line L12 and the second reference line L34 are parallel to each other.

[0124] [Action and effect] As described above, according to this modification, the second reference line L34 intersects with the third reference line L24 when viewed from the direction perpendicular to the substrate, and therefore, the same effects as those of the second embodiment can be obtained.

[0125] Furthermore, in this modification, the first reference line L12 intersects with the third reference line L24. This configuration in which the first reference line L12 intersects with the third reference line L24 is useful from the viewpoint of manufacturing. That is, in the photolithography process, the resist patterns for the first light-emitting element 14 and the second light-emitting element 16 are formed using the same photomask. At this time, by offsetting the photomask in the substrate width direction with respect to the third reference line L24, the resist patterns for the first light-emitting element 14 and the second light-emitting element 16 can be simultaneously offset with respect to the third reference line L24, facilitating manufacturing.

[0126] (Other embodiments) Although the light receiving and emitting sensor 10 according to the embodiment of the present disclosure has been described above, the present disclosure is not limited thereto, and the following embodiment may be adopted, for example.

[0127] (1) In each of the above-described embodiments and modifications, the controller 30 (calibration control unit 32) is configured to selectively cause either the first light-emitting element 14 or the second light-emitting element 16 to emit light when performing the calibration control. However, this is not limited to this. That is, for example, when detecting the density of registration marks r2 to r4 of a color other than black (yellow, magenta, or cyan), the controller 30 may cause the first light-emitting element 14 to emit light in addition to the second light-emitting element 16 to supplement the amount of light emitted from the second light-emitting element 16. When performing such control, the arrangement of the elements 14 to 17 described in each of the above-described embodiments (arrangement of the first light-receiving element 15, the first light-emitting element 14, the second light-receiving element 17, and the second light-emitting element 16 in this order) is particularly useful. That is, according to this arrangement, the second light-receiving element 17 is arranged on the opposite side (right side in FIG. 6 ) of the first light-emitting element 14 from the direction of light emitted from the first light-emitting element 14 (leftward in FIG. 6 ). Therefore, when control is executed to cause both the first light-emitting element 14 and the second light-emitting element 16 to emit light as described above, the specularly reflected light of the light emitted from the first light-emitting element 14 is unlikely to be received by the second light-receiving element 17. Therefore, it is possible to prevent the specularly reflected light of the first light-emitting element 14 from being incident on the second light-receiving element 17, thereby preventing a decrease in the accuracy of density measurement of the color registration marks r2 to r4 based on the output signal of the second light-receiving element 17.

[0128] (2) In the above embodiments and modifications, the light-emitting and receiving sensor 10 is used as a density detection sensor. However, this is not limiting and the sensor can also be used for color misregistration correction. In this case, the registration marks r1 to r4 may be, for example, right-angled triangular registration marks whose bases extend along the main scanning direction. The light-emitting and receiving sensor 10 outputs a detection signal while detecting the registration marks r1 to r4, resulting in a pulse-like output signal. If the registration marks r1 to r4 are misaligned in the main scanning direction, the width of this pulse signal changes. Therefore, the calibration control unit 32 can calculate the amount of misalignment of the registration marks r1 to r4 of each color in the main scanning direction by detecting the width of this pulse signal. The calibration control unit 32 may, for example, correct the start position of the exposure device 53 writing an electrostatic latent image corresponding to each color to correct the calculated amount of color misregistration.

[0129] (3) In each of the above-described embodiments and modifications, the elements 14 to 17 are mounted on the main surface of the wiring board 11 via the element substrates 12A, 12B (or element substrate 13), but this is not limited to this. The wiring board and the element substrate may be integrated into a single substrate.

[0130] (4) In each of the above-described embodiments and modifications, both the first light-emitting element 14 and the second light-emitting element 16 are configured to emit light toward a single, common, predetermined measurement irradiation position M, but this is not limited to this. That is, the measurement irradiation position M may be set separately for each of the first light-emitting element 14 and the second light-emitting element 16. In this case, the measurement irradiation position M is set at two locations spaced apart from each other in the predetermined direction (in this example, the direction corresponding to the main scanning direction).

[0131] (5) In each of the above-described embodiments and variations, the light receiving and emitting sensor 10 is arranged so that the predetermined direction, which is the arrangement direction of the elements 14 to 17, is along the main scanning direction. However, this is not limited to this, and the predetermined direction may be arranged so that it is along the sub-scanning direction (the direction of movement of the intermediate transfer belt 43).

[0132] (6) In the above-described embodiments and modifications, the light receiving and emitting sensor 10 is mounted on the image forming apparatus 100, but the present invention is not limited to this and may be applied to any other apparatus.

[0133] (7) In each of the above-described embodiments and modifications, the elements 14 to 17 may be configured as bullet-shaped elements. In this case, the end surface of each light-emitting element may be defined as the light-emitting region, and the end surface of each light-receiving element may be defined as the light-receiving region, and the configurations of the above-described embodiments and modifications may be applied.

[0134] (8) In each of the above embodiments and modifications, the first light-emitting element 14 and the second light-emitting element 16 do not necessarily have to be light-emitting diodes and may be, for example, laser diodes. That is, the light-emitting elements 14 and 16 may have any configuration as long as they are elements capable of emitting light. Furthermore, the first light-receiving element 15 and the second light-receiving element 17 do not necessarily have to be photodiodes and may be, for example, optical sensors using elements whose resistance changes depending on the amount of light. That is, the light-receiving elements 15 and 17 may have any configuration as long as they are elements capable of detecting the amount of light.

[0135] (9) The light receiving and emitting sensor of the present disclosure includes any combination of the above-described embodiments and modifications. [Explanation of symbols]

[0136] 10: Light receiving and emitting sensor 11: Wiring board (main board) 12A: First element substrate 12B: Second element substrate 13: Element substrate 14: First light-emitting element 14a: First light-emitting region 15: First light receiving element 15a: 1st light receiving area 16: Second light-emitting element 16a: Second light-emitting region 17: Second light receiving element 17a: 2nd light receiving area B: Measurement object M: Irradiated position for measurement C1: Center of gravity of the first light-emitting area C2: Center of gravity of the first light receiving area C3: Center of gravity of the second light-emitting area C4: Center of gravity of the second light receiving area L12: 1st reference line L34: Second reference line L24: 3rd reference line

Claims

1. A light receiving and emitting sensor that irradiates a light onto a measurement object and detects reflected light from the measurement object, A main board; a first light-emitting element, a second light-emitting element, a first light-receiving element, and a second light-receiving element arranged along a predetermined direction on one surface of the main substrate; the first light-emitting element includes a first light-emitting region, and the second light-emitting element includes a second light-emitting region; the first light receiving element includes a first light receiving region, and the second light receiving element includes a second light receiving region; the first light receiving element is disposed at a position where it can receive specularly reflected light of light emitted from the first light emitting element, the second light receiving element is disposed at a position where it can receive diffusely reflected light of light emitted from the second light emitting element, When viewed from a substrate normal direction perpendicular to the main substrate, a straight line passing through the area center of gravity of the first light-emitting region and the area center of gravity of the first light-receiving region is defined as a first reference line, and a straight line passing through the area center of gravity of the second light-emitting region and the area center of gravity of the second light-receiving region is defined as a second reference line, and each of the light-receiving elements and each of the light-emitting elements is arranged so that the first reference line and the second reference line intersect.

2. 2. The light receiving and emitting sensor according to claim 1, a first element substrate and a second element substrate stacked on the main substrate and arranged adjacent to each other in the predetermined direction; the first light receiving element and the first light emitting element are disposed on the first element substrate, The second light receiving element and the second light emitting element are disposed on the second element substrate, forming a light receiving and emitting sensor.

3. 3. The light receiving and emitting sensor according to claim 2, A light receiving and emitting sensor, wherein, when viewed from the substrate perpendicular direction, the first element substrate is arranged so that its extension direction is parallel to the first reference line and coincides with the extension direction of the main substrate, and the second element substrate is arranged so that its extension direction is parallel to the second reference line and inclined with respect to the extension direction of the main substrate.

4. 3. The light receiving and emitting sensor according to claim 2, When viewed from the substrate perpendicular direction, the first element substrate is disposed so that its extension direction is parallel to the first reference line and coincides with the extension direction of the main substrate; the second element substrate is disposed so that its extension direction coincides with the extension direction of the main substrate, The light receiving and emitting sensor, wherein the center of gravity of the second light receiving region and the center of gravity of the second light emitting region are different from each other in a direction perpendicular to the extending direction of the second element substrate when viewed from the substrate perpendicular direction.

5. 4. The light receiving and emitting sensor according to claim 3, The light receiving and emitting sensor, wherein the center of gravity of the second light receiving region and the center of gravity of the second light emitting region are different from each other in a direction perpendicular to the extending direction of the second element substrate when viewed from the substrate perpendicular direction.

6. A light receiving and emitting sensor that irradiates a light onto a measurement object and detects reflected light from the measurement object, A main board; a first light-emitting element, a second light-emitting element, a first light-receiving element, and a second light-receiving element arranged along a predetermined direction on one surface of the main substrate; the first light-emitting element includes a first light-emitting region, and the second light-emitting element includes a second light-emitting region; the first light receiving element includes a first light receiving region, and the second light receiving element includes a second light receiving region; the first light receiving element is disposed at a position where it can receive specularly reflected light of light emitted from the first light emitting element, the second light receiving element is disposed at a position where it can receive diffusely reflected light of light emitted from the second light emitting element, When viewed from a substrate normal direction perpendicular to the main substrate, a line passing through the area center of gravity of the second light-emitting region and the area center of gravity of the second light-receiving region is defined as a second reference line, and a line passing through the area center of gravity of the first light-receiving region and the area center of gravity of the second light-receiving region is defined as a third reference line, and each of the light-receiving elements and each of the light-emitting elements is arranged so that the second reference line and the third reference line intersect.

7. 7. The light receiving and emitting sensor according to claim 6, further comprising an element substrate laminated on the one surface of the main substrate, The light receiving and emitting sensor, wherein the first light receiving element, the first light emitting element, the second light receiving element, and the second light emitting element are disposed on the element substrate.

8. The light receiving and emitting sensor according to claim 7, When viewed from the direction perpendicular to the substrate, a straight line passing through the center of gravity of the first light-emitting region and the center of gravity of the first light-receiving region is defined as a first reference line, and each of the light-receiving elements and each of the light-emitting elements is arranged so that the third reference line intersects with the first reference line.

9. The light receiving and emitting sensor according to claim 7, When viewed from the direction perpendicular to the substrate, a straight line passing through the center of gravity of the first light-emitting region and the center of gravity of the first light-receiving region is defined as a first reference line, and each of the light-receiving elements and each of the light-emitting elements is arranged so that the third reference line is parallel to the first reference line.

10. An image forming apparatus comprising the light receiving and emitting sensor according to claim 1 .

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