Light-receiving / emitting sensor and image-forming apparatus equipped with same

Abstract

A light-receiving / emitting sensor (10) is provided with a substrate (11), and a first light-emitting element (14), first light-receiving element (15), second light-emitting element (16), and second light-receiving element (17) provided on one surface of the substrate (11). 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 side by side in the stated order along a predetermined direction on the one surface, the first light-receiving element (15) being disposed at a position where regular reflection light of the light emitted from the first light-emitting element (14) can be received, and the second light-receiving element (17) being disposed at a position where diffused reflection light of the light emitted from the second light-emitting element (16) can be received.

Description

Light receiving and emitting sensor and image forming apparatus equipped with the light receiving and emitting sensor

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

[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 Japanese Patent Application Laid-Open No. 2005-207499. 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 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, and the first light receiving element is disposed at a position where it can receive diffusely reflected light emitted from the second light emitting element, and the second light receiving element is disposed at a position where it can receive diffusely reflected light emitted from the second light emitting element.

[0006] Patent Document 1 discloses the following three arrangement orders of the elements on the substrate. That is, in FIG. 2 of Patent Document 1, the first light-emitting element, the first light-receiving element, the second light-receiving element, and the second light-emitting element are arranged in this order on the substrate along a predetermined direction. In FIG. 6 of Patent Document 1, the first light-emitting element, the first light-receiving element, the second light-emitting element, and the second light-receiving element are arranged in this order on the substrate along a predetermined direction. In FIG. 20 of Patent Document 1, the first light-receiving element, the first light-emitting element, the second light-emitting element, and the second light-receiving element are arranged in this order on the substrate along a predetermined direction.

[0007] An optical receiving and emitting sensor according to one aspect of the present disclosure is an optical receiving and emitting sensor that irradiates light toward an object to be measured and detects reflected light from the object to be measured, and includes a substrate and a first light-emitting element, a second light-emitting element, a first light-receiving element, and a second light-receiving element provided on one surface of the substrate, wherein the first light-receiving element, the first light-emitting element, the second light-receiving element, and the second light-emitting element are arranged in this order along a predetermined direction on the one surface, 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, wherein the first light-receiving element is positioned at a position where it can receive specularly reflected light of light emitted from the first light-emitting element, and the second light-receiving element is positioned at a position where it can receive diffusely reflected light of light emitted from the second light-emitting element.

[0008] An image forming apparatus according to another aspect of the present disclosure includes the light receiving and emitting sensor.

[0009] FIG. 1 is a schematic diagram showing an image forming apparatus equipped with an optical receiving and emitting sensor according to an embodiment. FIG. 2 is an explanatory diagram illustrating the arrangement of the optical receiving and emitting sensors, showing a view of the intermediate transfer unit from below. FIG. 3 is a block diagram illustrating the configuration of a control system including a controller. FIG. 4A is an explanatory diagram illustrating the principle of black toner detection, showing a case where black toner is not present on the intermediate transfer belt. FIG. 4B is an explanatory diagram illustrating the principle of black toner detection, showing a case where black toner is present on the intermediate transfer belt. FIG. 5A is an explanatory diagram illustrating the principle of color toner detection, showing a case where color toner is not present on the intermediate transfer belt. FIG. 5B is an explanatory diagram illustrating the principle of color toner detection, showing a case where color toner is present on the intermediate transfer belt. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 2. FIG. 7 is a schematic diagram illustrating the arrangement of each optical receiving and emitting element on a wiring board, and corresponds to the view seen in the direction of arrow VII in FIG. 6. FIG. 8 is a diagram equivalent to FIG. 6, illustrating a second embodiment. FIG. 9 is a diagram equivalent to FIG. 7, illustrating a second embodiment. FIG. 10 is a diagram equivalent to FIG. 9, illustrating a third embodiment. Fig. 11 is an explanatory diagram showing a state of change in the position of reflected light when the position of the measurement object is shifted. Fig. 12 is a diagram corresponding to Fig. 9 and showing embodiment 4. Fig. 13A is a diagram corresponding to Fig. 7 and showing embodiment 5. Fig. 13B is a diagram corresponding to Fig. 7 and showing modified example 1 of embodiment 5. Fig. 13C is a diagram corresponding to Fig. 7 and showing modified example 2 of embodiment 5. Fig. 14 is a diagram corresponding to Fig. 6 and showing embodiment 6. Fig. 15 is a diagram corresponding to Fig. 7 and showing embodiment 6. Fig. 16A is a diagram corresponding to Fig. 15 and showing embodiment 7. Fig. 16B is a diagram corresponding to Fig. 16A and showing modified example 1 of embodiment 7.

[0010] 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.

[0011] 1 is a schematic diagram showing an image forming apparatus 100 including a light receiving and emitting sensor 10 according to this embodiment. The image forming apparatus 100 is configured as a tandem color printer.

[0012] [Overall Configuration of Image Forming Apparatus] The image forming apparatus 100 includes a paper feed unit 1, a vertical transport path 2, a pair of registration rollers 3, an intermediate transfer unit 4, an image forming unit 50, a secondary transfer unit 6, a fixing device 7, a discharge transport path 8, a discharge tray 9, a light receiving and emitting sensor 10, and a controller 30 (FIG. 3). The image forming unit 50 is equipped with four image forming mechanisms 5B, 5M, 5C, and 5Y.

[0013] The image forming apparatus 100 performs the following image forming process: A sheet P is transported from a sheet feed cassette 1a in a sheet 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.

[0014] 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, thereby forming a color image.

[0015] 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. A color image is formed on the paper P.

[0016] 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. 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.

[0017] 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.

[0018] Next, a detailed description will be given of 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.

[0019] 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, in order 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 comprise image forming units having substantially the same configuration. Therefore, the same reference numerals are used for parts having 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" will be omitted unless otherwise specified, and the mechanisms will simply be referred to as the image forming mechanisms 5.

[0020] 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. A 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.

[0021] [Arrangement 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.

[0022] 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 viewed from below.

[0023] As shown in this figure, the light receiving and emitting 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 receiving and emitting 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 receiving and emitting sensor 10 is input to a controller 30 described below, and the controller 30 performs calibration control (toner concentration correction processing) described below based on the signal received from the light receiving and emitting sensor 10. Note that the number of light receiving and emitting sensors 10 is not limited to one; for example, two light receiving and emitting sensors 10 may be disposed on both sides of the outer peripheral surface of the intermediate transfer belt 43 in the width direction.

[0024] 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.

[0025] The process equipment 50A is equipment 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.

[0026] 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.

[0027] 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.

[0028] The print control unit 31 executes a printing process on paper P by controlling the process device 50A based on image data transmitted from an external terminal, for example.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] [Detection Principle of Light Receiving and Emitting Sensor] Next, the detection principle of black toner and color toner by the light receiving and emitting sensor 10 will be briefly described with reference to FIGS.

[0033] 4A is an explanatory diagram for explaining the principle of detecting black toner, showing a case where black toner is not present on the intermediate transfer belt, and FIG. 4B shows a case where black toner is present on the intermediate transfer belt. In FIG. 4A and FIG. 4B, for the purpose of explaining the principle, 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 are shown as schematic diagrams separate from the actual device.

[0034] As shown in FIG. 4A , 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, as shown in FIG. 4B , when there is black toner on the intermediate transfer belt 203, 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, the density of the black toner can be detected based on the output signal from the light-receiving element 202.

[0035] 5A is an explanatory diagram for explaining the principle of color toner detection, showing a case where no color toner is present on the intermediate transfer belt, and FIG. 5B shows a case where color toner is present on the intermediate transfer belt. In FIG. 5A and FIG. 5B, a light-emitting element 301, a light-receiving element 302, and an intermediate transfer belt 303 are shown as schematic diagrams separate from the actual device.

[0036] 5, the position of the light receiving element 302 is different from that when 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).

[0037] 5A, when there is no color toner on intermediate transfer belt 303, light emitted from light-emitting element 301 is specularly reflected from the surface of intermediate transfer belt 303, but since light-receiving element 302 is not located beyond this specularly reflected light, the output signal of light-receiving element 302 does not change. On the other hand, when there is color toner on intermediate transfer belt 303, as shown in FIG. 5B, part of the light incident on intermediate transfer belt 303 from light-emitting element 301 is diffusely reflected by the color toner and enters light-receiving element 302. Therefore, by locating light-receiving element 302 at a position away from the specular reflection position and at a position where it can receive diffusely reflected light, it is possible to detect the density of color toner based on the output signal of light-receiving element 302.

[0038] [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 detection principle described above.

[0039] The 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).

[0040] The light receiving and emitting sensor 10 includes a wiring board 11, a first element board 12A and a second element board 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 board 12A, a second light emitting element 16 and a second light receiving element 17 formed on the second element board 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).

[0041] In the following, first, each component of the light receiving and emitting sensor 10 will be described, and then the arrangement of the four elements 14 to 17 will be described in detail.

[0042] 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.

[0043] The first element substrate 12A and the second element substrate 12B are each formed of a semiconductor substrate, for example, and are mounted (stacked) 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 silicon (Si) substrate. The first element substrate 12A and the second element substrate 12B are both rectangular in shape, elongated in the predetermined direction (see FIG. 7). 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 shape.

[0044] 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).

[0045] 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 board, 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. 7 described later) and the area centroid position C1 of the first light-emitting region 14a of the first light-emitting element 14.

[0046] 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 side facing 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).

[0047] 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 at a position where it can receive the diffusely reflected light of the light emitted from the second light-emitting element 16.

[0048] 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 closer to the second light emitting element 16 (to the right in FIG. 6 ) than a line that passes through the measurement irradiation position M and extends in the vertical direction. In other words, the second light receiving element 17 is disposed on the opposite side (to the right in FIG. 6 ) from the specular reflection side of the light emitted from the second light emitting element 16 with respect to the measurement irradiation position M.

[0049] 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).

[0050] 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).

[0051] 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, a metal organic chemical vapor deposition (MOCVD) 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) having a p-type semiconductor region formed thereon, thereby forming a p-n junction at the interface therebetween.

[0052] 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.

[0053] 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.

[0054] The first light receiving side lens 192 collects light emitted from the first light emitting element 14 and reflected specularly at the measurement irradiation position M, and guides it to the first light receiving element 15 (more specifically, the first light receiving area 15a of the first light receiving element 15).

[0055] The second light-emitting side lens 193 condenses the light emitted from the second light-emitting element 16 and guides it to the measurement irradiation position M. Note that the lenses 191 to 194 are not necessarily required.

[0056] 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 area 17a of the second light receiving element 17).

[0057] These lenses 191 to 194 are configured by, for example, convex lenses, spherical lenses, aspherical lenses, or the like.

[0058] 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 cover 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. Note that the housing 18 may be configured by combining multiple members.

[0059] The peripheral wall 18a is a frame-shaped member that surrounds the entire periphery of the element accommodating space S that accommodates the elements 14 to 17. An opening on one end of the peripheral wall 18a is closed by the wiring board 11, and an opening on the other end is closed by the lid 18b. Thus, the element accommodating space S is formed by the lid 18b, the wiring board 11, and the peripheral wall 18a.

[0060] The first light-shielding wall 18c and the second light-shielding wall 18d are provided to protrude from the surface of the cover portion 18b facing the wiring board 11.

[0061] 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. As a result, 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.

[0062] 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.

[0063] [Regarding Light Emission Control of Each Light Emitting Element] Next, a detailed description will be given of light emission control of each of the light emitting elements 14, 16 provided in the light receiving and emitting sensor 10. The light emission control of each of the light emitting elements 14, 16 is realized by the function of the calibration control unit 32 of the controller 30.

[0064] 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 / receiving sensor 10.

[0065] Specifically, the calibration control unit 32 causes only the first light-emitting element 14 to emit light at the time when the black resist mark r1 passes through the measurement irradiation position M and before and after that, and acquires (calculates) the density of the black resist mark r1 based on the magnitude of the output signal output from the first light-receiving element 15 after the emission.

[0066] 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.

[0067] [Details of Arrangement of Light-Emitting and Light-Receiving Elements] FIG. 7 is a schematic diagram for explaining the arrangement of the elements 14 to 17 on the wiring board 11, and corresponds to the view seen in the direction of the arrow VII in FIG.

[0068] 7 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, respectively, coincide with each other, but this does not necessarily have to be the case. 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, respectively, coincide with each other, but this does not necessarily have to be the case. 7, 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, as described below. 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, and may be, for example, a circular or diamond shape.

[0069] 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 in the longitudinal direction of the wiring board 11 (a predetermined direction, which in this example is the main scanning direction).

[0070] 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 12 A. A pair of bonding pads 21 for connecting bonding wires are formed on both sides of the first light-emitting element 14 in the substrate width direction on the first element substrate 12 A.

[0071] 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 are formed on both sides of the second light-emitting element 16 in the substrate width direction on the second element substrate 12B.

[0072] 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.

[0073] 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.

[0074] Therefore, in this embodiment, a straight line passing through the areal centroid positions C1 and C2 of the first light-emitting region 14a and the first light-receiving region 15a is defined as a first reference line L12. Furthermore, in this embodiment, a straight line passing through the areal centroid positions C3 and C4 of the second light-emitting region 16a of the second light-emitting element 16 and the second light-receiving region 17a of the second light-receiving element 17, which are formed using the same photomask, is defined as a second reference line L34 as a reference line for defining the design positional relationship with respect to the first reference line L12. Here, the areal centroid positions C1, C2, C3, and C4 refer to the centroid positions of the regions 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 perpendicular direction of the wiring substrate 11 (hereinafter referred to as the substrate perpendicular direction), and are geometric centroid positions of the regions that can be determined without considering the mass distribution within the regions.

[0075] In the light receiving and emitting sensor 10 of this embodiment, the elements 14 to 17 are arranged so that the first reference line L12 and the second reference line L34 are positioned on the same straight line when viewed from the direction perpendicular to the board.

[0076] In this embodiment, when viewed from the substrate perpendicular direction, the widthwise center line of each of the element substrates 12A, 12B coincides with the widthwise center line of the wiring substrate 11. Here, the widthwise center line is a straight line that passes through the center position in the width direction and extends in the predetermined direction in this example. The widthwise center line of the first element substrate 12A coincides with the first reference line L12. The widthwise center line of the second element substrate 12B coincides with the second reference line L34. These straight lines are all located on the same straight line.

[0077] Furthermore, when viewed from the direction perpendicular to the substrate, the distance (hereinafter referred to as the first separation distance) between 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 K1, and the distance (hereinafter referred to as the second separation distance) between 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 K2. In this example, the relationship K1 = K2 is satisfied.

[0078] Furthermore, when viewed from a direction perpendicular to the wiring board 11, when the distance (hereinafter referred to as the third separation distance) between 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 C4 of the second light-receiving region 17a of the second light-receiving element 17 is K3, the relationship K3 < K1 (= K2) is satisfied.

[0079] [Effects] As described above, 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 arranged in this order along a predetermined direction on one surface of the wiring substrate 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.

[0080] According to this configuration, 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, thereby 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.

[0081] 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 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, a larger incident angle weakens 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-emitting element 16 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 illuminated 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.

[0082] 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, thereby reducing the possibility that specularly reflected light emitted from the first light emitting element 14 will be incident on the second light receiving element 17. This makes it possible to minimize the possibility that specularly reflected light emitted from the first light emitting element 14 will be mixed in 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.

[0083] 8 and 9 are views corresponding to FIGS. 6 and 7, respectively, illustrating a second embodiment. In this embodiment, the relationship between the distance between the first light-emitting element 14 and the first light-receiving element 15 and the distance between the second light-emitting element 16 and the second light-receiving element 17 is different from that in the first embodiment. In FIGS. 8 and 9, the same components as those in FIGS. 6 and 7 are designated by the same reference numerals, and their description will be omitted where appropriate.

[0084] That is, in this embodiment, the distance in the alignment direction (predetermined direction) between the second light-emitting element 16 and the second light-receiving element 17 is set to be greater than the distance in the alignment direction (predetermined direction) between the first light-emitting element 14 and the first light-receiving element 15 (see Figures 8 and 9).

[0085] Here, in this embodiment, the distance in the alignment direction between the first light-emitting element 14 and the first light-receiving element 15 is defined as the separation distance K1 (hereinafter referred to as the first separation distance K1; see Figure 9) between the area center of gravity position C1 of the first light-emitting region 14a of the first light-emitting element 14 and the area center of gravity position C2 of the first light-receiving region 15a of the first light-receiving element 15, when viewed from the direction perpendicular to the substrate.

[0086] In addition, the distance in the alignment direction between the second light-emitting element 16 and the second light-receiving element 17 is defined as the separation distance K2 (hereinafter referred to as the second separation distance K2, see Figure 9) between the area center of gravity position C3 of the second light-emitting region 16a of the second light-emitting element 16 and the area center of gravity position C4 of the second light-receiving region 17a of the second light-receiving element 17 when viewed from the direction perpendicular to the substrate.

[0087] In this example, the second separation distance K2 is set to be larger than the first separation distance K1, as shown in Fig. 9. That is, in Fig. 9, the relationship K2>K1 is satisfied.

[0088] Here, a first distance ratio R1 (= K2 / K1) can be defined as the ratio of the second separation distance K2 to the first separation distance K1, and this first distance ratio is preferably greater than 1.0 and less than or equal to 1.6, and even more preferably 1.3.

[0089] In this example, the first separation distance K1 and the second separation distance K2 are both set to be greater than the third separation distance K3, which is the separation distance between the first light-emitting element 14 and the second light-receiving element 17. That is, in FIG. 9, the relationships K1>K3 and K2>K3 are satisfied.

[0090] Here, a second distance ratio R2 (= K1 / K3) can be defined as the ratio between the first separation distance K1 and the third separation distance K3, and this second distance ratio R2 is preferably 1.1 to 1.7, and more preferably 1.4. Also, a third distance ratio R3 (= K2 / K3) can be defined as the ratio between the second separation distance K2 and the third separation distance K3, and this third distance ratio R3 is preferably 1.5 to 2.1, and more preferably 1.8.

[0091] [Effects] As described above, in this embodiment, the elements 14 to 17 are arranged in the same order as in the first embodiment, so that the incident angle θ1 of the light incident from the second light-emitting element 16 to the measurement irradiation position M can be made large, and the same effects as in the first embodiment can be obtained.

[0092] In this embodiment, when viewed from the substrate perpendicular direction, a second separation distance K2, which is the 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 set to be larger than a first separation distance K1, which is the 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. That is, the relationship K2>K1 is satisfied (see FIG. 9 ).

[0093] According to this configuration, the incident angle θ1 of the light incident on the measurement irradiation position M from the second light-emitting element 16 can be made larger than that of the first embodiment. Therefore, the same effects as those of the first embodiment can be obtained more reliably.

[0094] On the other hand, because the first separation distance K1 is relatively narrow, the angle of incidence θ2 of light incident from the first light-emitting element 14 onto the measurement irradiation position M can be made as small as possible. Generally, the smaller the angle of incidence of light, the more likely specular reflection light is generated (because the proportion of specular reflection components contained in the reflected light relatively increases). Therefore, by making the angle of incidence θ2 of light irradiated from the first light-emitting element 14 onto the measurement irradiation position M small as described above, it is possible to ensure a sufficient amount of specular reflection light detected by the first light-receiving element 15. This allows differences in the specular reflection characteristics of black toner (differences in density in this example) to be reflected in changes in the amount of specular reflection light, and can be reliably detected by the first light-receiving element 15.

[0095] However, if the first distance ratio R1 (= K2 / K1), which is the ratio between the first separation distance K1 and the second separation distance K2, is too large or too small, there is a risk that the accuracy of measuring the density of black toner using the first light-emitting element 14 and the first light-receiving element 15 and the accuracy of measuring the density of color toner using the second light-emitting element 16 and the second light-receiving element 17 will be compromised.

[0096] After extensive research, the inventors have found that this problem can be avoided by setting the first distance ratio R1 (=K2 / K1) to be greater than 1.0 and equal to or less than 1.6, thereby improving the accuracy of toner concentration measurement by the light receiving and emitting sensor 10 as much as possible.

[0097] 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 arranged in this order along a predetermined direction on one surface of the wiring substrate 11. In this embodiment, when viewed from the substrate perpendicular direction, the second separation distance K2 is set to be larger than the third separation distance K3, which is the 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. In other words, the relationship K2>K3 is satisfied (see FIG. 9 ).

[0098] This configuration allows the second separation distance K2 to be relatively wide, minimizing the transfer of heat from the second light-emitting element 16 to the second light-receiving element 17. This prevents the temperature of the second light-receiving element 17 from excessively increasing and reducing its photoelectric conversion accuracy. Meanwhile, the third separation distance K3 is set relatively narrow, allowing the second light-receiving element 17 to be positioned as close as possible to the measurement irradiation position M (in this example, the center position of the line segment connecting the area centroid positions C1 and C2 as viewed from the substrate perpendicular direction). This makes it easier for the second light-receiving element 17 to receive diffused light from the measurement object B (measurement irradiation position M). This maximizes the accuracy of color toner concentration measurement based on the output signal of the second light-receiving element 17.

[0099] Here, if the third distance ratio R3 (= K2 / K3), which is the ratio between the second separation distance K2 and the third separation distance K3, is too large or too small, there is a risk that it will be impossible to protect the second light-receiving element 17 from heat generated by the first light-emitting element 14 and improve the accuracy of measuring the concentration of color toner using the second light-emitting element 16 and the second light-receiving element 17.

[0100] After extensive research, the inventors have found that this problem can be avoided by setting the third distance ratio R3 (=K2 / K3) to 1.5 or greater and 2.1 or less, thereby improving the accuracy of toner concentration measurement by the light receiving and emitting sensor 10 as much as possible while thermally protecting the second light receiving element 17.

[0101] In this embodiment, the first distance K1 is set to be larger than the third distance K3, that is, the relationship K1>K3 is satisfied (see FIG. 9).

[0102] This configuration allows the first separation distance K1 to be relatively wide, minimizing the transfer of heat from the first light-emitting element 14 to the first light-receiving element 15. This prevents the temperature of the first light-receiving element 15 from excessively increasing and reducing its photoelectric conversion accuracy. Meanwhile, the third separation distance K3 can be relatively narrow, allowing the second light-receiving element 17 to be positioned as close as possible to the measurement irradiation position M (in this example, the center position of the line segment connecting the area center positions C1 and C2 as viewed from the substrate perpendicular direction). This makes it easier for the second light-receiving element 17 to receive diffused light from the measurement target B. This improves the accuracy of color toner concentration measurement based on the output signal of the second light-receiving element 17.

[0103] However, if the second distance ratio R2 (= K1 / K3), which is the ratio between K1 and K3, is too large or too small, there is a risk that it will be impossible to protect each of the light-receiving elements 15 and 17 from heat generated by the first light-emitting element 14 and improve the accuracy of measuring the toner concentration based on the output signals of each of the light-receiving elements 15 and 17.

[0104] After extensive research, the inventors have found that this problem can be avoided by setting the second distance ratio R2 (=K1 / K3) to 1.1 or more and 1.7 or less, thereby improving the accuracy of toner concentration measurement by the light receiving and emitting sensor 10 as much as possible while protecting the light receiving elements 15 and 17 from heat.

[0105] In addition, in this embodiment, a first element substrate 12A and a second element substrate 12B are stacked adjacent to each other on one surface of the wiring substrate 11, and a first light-emitting element 14 and a first light-receiving element 15 are formed on the first element substrate 12A, and a second light-emitting element 16 and a second light-receiving element 17 are formed on the second element substrate 12B.

[0106] According to this, since the first light-emitting element 14 and the second light-receiving element 17 are formed on different element substrates 12A, 12B, respectively, heat generated from the first light-emitting element 14 is prevented from being transmitted to the second light-receiving element 17, and ultimately, the photoelectric conversion accuracy of the second light-receiving element 17 is prevented from being reduced due to heat generated from the first light-emitting element 14.

[0107] Moreover, in this embodiment, the first element substrate 12A and the second element substrate 12B are disposed adjacent to each other with a gap therebetween.

[0108] Therefore, compared to when the first element substrate 12A and the second element substrate 12B are disposed adjacent to each other with no gap between them, the transfer of heat between the first element substrate 12A and the second element substrate 12B can be suppressed as much as possible, and therefore, the transfer of heat from the first light-emitting elements 14 formed on the first element substrate 12A to the second light-receiving elements 17 formed on the second element substrate 12B can be more reliably suppressed.

[0109] (Embodiment 3) Figure 10 is a view corresponding to Figure 9 and shows embodiment 3. In this embodiment, the size relationship between the area of ​​the first light-emitting region 14a of the first light-emitting element 14 and the area of ​​the second light-emitting region 16a of the second light-emitting element 16 when viewed from the direction perpendicular to the substrate is different from that of embodiment 2. Except for this point, the other configuration is the same as embodiment 2. In Figure 10, the same components as those in Figure 9 are assigned the same reference numerals, and their description will be omitted as appropriate.

[0110] That is, in this embodiment, the area A1 of the first light-emitting region 14a of the first light-emitting element 14 (which in this example corresponds to the area defined by the outer edge of the first light-emitting element 14) when viewed from the direction perpendicular to the substrate is larger than the area A2 of the second light-emitting region 16a of the second light-emitting element 16 (which in this example corresponds to the area defined by the outer edge of the second light-emitting element 16). That is, the relationship A1>A2 is satisfied.

[0111] Here, the area ratio Sa (= A1 / A2) can be defined as an index showing how large the area A1 of the first light-emitting region 14a of the first light-emitting element 14 is set relative to the area A2 of the second light-emitting region 16a of the second light-emitting element 16, and this area ratio Sa is preferably 1.2 or more and 1.8 or less, and even more preferably 1.5.

[0112] In this example, in order to achieve the above-mentioned area relationship A1>A2, the first light-emitting region 14a of the first light-emitting element 14 is formed longer in the substrate length direction (the predetermined direction) than the second light-emitting region 16a of the second light-emitting element 16. Note that in this example, in the substrate width direction (the up-and-down direction in FIG. 10 ), the dimension V1 of the first light-emitting region 14a of the first light-emitting element 14 and the dimension V2 of the second light-emitting region 16a of the second light-emitting element 16 are set to the same size. In other words, the first light-emitting region 14a of the first light-emitting element 14 is formed so as to be longer than the second light-emitting region 16a of the second light-emitting element 16 only in the substrate length direction.

[0113] The aspect ratio of the first light-emitting region 14a of the first light-emitting element 14 when viewed from the direction perpendicular to the substrate (i.e., the value obtained by dividing the dimension H1 of the first light-emitting element 14 in the substrate length direction by the dimension V1 in the substrate width direction) is set to a value larger than the aspect ratio of the second light-emitting region 16a of the second light-emitting element 16 (i.e., the value obtained by dividing the dimension H2 of the second light-emitting element 16 in the substrate length direction by the dimension V2 in the substrate width direction).

[0114] For example, the aspect ratio (H1 / V1) of the first light-emitting element 14 is preferably 1.5 to 2.1, and more preferably 1.8. The aspect ratio (H2 / V2) of the second light-emitting element 16 is preferably 1.0 to 1.4, and more preferably 1.2.

[0115] [Effects] As described above, in this embodiment, when viewed from the direction perpendicular to the substrate, the area A1 of the first light-emitting region 14a of the first light-emitting element 14 is set to be larger than the area A2 of the second light-emitting region 16a of the second light-emitting element 16.

[0116] With this configuration, if the distance between the object to be measured B (in this example, the toner that constitutes the registration marks r1 to r4) and the light receiving and emitting sensor 10 deviates from the preset distance for some reason, the possibility that the first light receiving element 15 and the second light receiving element 17 will have difficulty detecting the reflected light can be reduced.

[0117] That is, if the distance between the light receiving and emitting sensor 10 and the measurement object B deviates from the set distance, the reflection position of the specularly reflected light emitted from the first light emitting element 14 will be displaced in the element alignment direction (the predetermined direction). In FIG. 11 , as an example, a state in which the distance has decreased due to a misalignment of the intermediate transfer belt 43 is shown by a two-dot chain line. As shown in this figure, it can be seen that the reduction in the distance causes the reflection position of the specularly reflected light emitted from the first light emitting element 14 to be displaced in the element alignment direction (the predetermined direction). As a result, there is a risk that the specularly reflected light will not be received by the first light receiving element 15.

[0118] In contrast, in this embodiment, the area of ​​the first light-emitting region 14a of the first light-emitting element 14 is set larger than the area of ​​the second light-emitting region 16a of the second light-emitting element 16. This increases the spot diameter of light incident on the measurement object B from the first light-emitting element 14, and therefore the spot diameter of the specularly reflected light. Therefore, even if the reflection position of the specularly reflected light of the light emitted from the first light-emitting element 14 changes due to a deviation of the distance between the light-receiving and -emitting sensor 10 and the measurement object B from the set distance, the specularly reflected light can be easily detected by the first light-receiving element 15. Therefore, the concentration of black toner can be accurately measured based on the output signal of the first light-receiving element 15. On the other hand, because the diffusely reflected light from the measurement object B has lower optical directionality than the specularly reflected light, a deviation in the distance between the light-receiving and -emitting sensor 10 and the measurement object B is less likely to affect the detection of the diffusely reflected light by the second light-receiving element 17. Therefore, in this configuration, the area of ​​the second light-emitting region 16a of the second light-emitting element 16, which is the irradiation source of the diffusely reflected light that enters the second light-receiving element 17, is set smaller than the area of ​​the first light-emitting region 14a of the first light-emitting element 14. This reduces the possibility that, for example, when the first light-emitting element 14 and the second light-emitting element 16 are simultaneously emitting light to detect the toner concentration, the range of diffusely reflected light of the light emitted from the second light-emitting element 16 will unnecessarily expand and reach the first light-receiving element 15. This reduces the possibility that the first light-receiving element 15 will receive unnecessary light, thereby reducing the accuracy of measuring the black toner concentration.

[0119] Furthermore, in this embodiment, when viewed from a direction perpendicular to the substrate, when the area of ​​the first light-emitting region 14a of the first light-emitting element 14 is A1 and the area of ​​the second light-emitting region 16a of the second light-emitting element 16 is A2, it is preferable that A1 / A2 be 1.2 or more and 1.8 or less.

[0120] That is, if A1 / A2 is too small, the spot diameter of the light emitted from the first light-emitting element 14 becomes small, and therefore, if the distance between the measurement object B and the light-receiving sensor 10 deviates from the set distance, it is not possible to ensure that the specularly reflected light from the first light-emitting element 14 overlaps with the first light-receiving area 15a of the first light-receiving element 15. On the other hand, if A1 / A2 is too large, the spot diameter of the light emitted from the first light-emitting element 14 becomes large, and therefore, if the distance between the measurement object B and the light-receiving sensor 10 deviates from the set distance, there is a risk that diffusely reflected light or specularly reflected light from the first light-emitting element 14 may unintentionally enter the second light-receiving element 17. Therefore, after extensive research, the inventors have found that this problem can be avoided by setting A1 / A2 to 1.2 or more and 1.8 or less. This numerical range is particularly useful when the light-receiving sensor 10 is used to measure the toner concentration on the intermediate transfer belt 43 in the image forming apparatus 100.

[0121] In this embodiment, the first light-emitting region 14a of the first light-emitting element 14 is set to be longer in the predetermined direction than the second light-emitting region 16a of the second light-emitting element 16. In other words, the dimension H1 of the first light-emitting region 14a of the first light-emitting element 14 in the alignment direction of the first light-emitting element 14 and the first light-receiving element 15 is set to be larger than the dimension H2 of the second light-emitting region 16a of the second light-emitting element 16 in the alignment direction of the second light-emitting element 16 and the second light-receiving element 17 (see 10).

[0122] According to this configuration, by setting the first light-emitting region 14a of the first light-emitting element 14 long in a predetermined direction, which is the displacement direction of the specularly reflected light (see the two-dot chain line in FIG. 11 ), even if the reflection position of the specularly reflected light of the light emitted from the first light-emitting element 14 is displaced in the predetermined direction due to the distance between the measurement object B and the light-receiving sensor 10 deviating from the preset distance as described above, the specularly reflected light and the first light-receiving region 15a of the first light-receiving element 15 are ensured to overlap, making it easier for the first light-receiving element 15 to receive the specularly reflected light. Therefore, the accuracy of black toner concentration measurement based on the output signal of the first light-receiving element 15 can be improved as much as possible.

[0123] This configuration can also be defined by the following aspect ratio relationship. That is, when viewed from the direction perpendicular to the substrate, the dimension of the first light-emitting region 14 a of the first light-emitting element 14 in the alignment direction of the first light-emitting element 14 and the first light-receiving element 15 is defined as H1, the dimension of the light-emitting region 14 a in the direction perpendicular to the alignment direction is defined as V1, and the dimension of the second light-emitting region 16 a of the second light-emitting element 16 in the alignment direction of the second light-receiving element 17 and the second light-emitting element 16 is defined as H2, and the dimension of the light-emitting region 16 a in the direction perpendicular to the alignment direction is defined as V2. The aspect ratio H1 / V1 of the first light-emitting region 14 a of the first light-emitting element 14 may be set to be larger than the aspect ratio H2 / V2 of the second light-emitting region 16 a of the second light-emitting element 16 (see FIG. 10 ). This can achieve the same advantageous effects.

[0124] In this embodiment, the distance between the first light-emitting element 14 (more specifically, the area center of gravity of the surface of the first light-emitting element 14 facing the intermediate transfer belt 43 (the lower side in Figure 6)) and its measurement illuminated position M is set shorter than the distance between the second light-emitting element 16 (more specifically, the area center of gravity of the surface of the second light-emitting element 16 facing the intermediate transfer belt 43 (the lower side in Figure 6)) and its measurement illuminated position M.

[0125] In such an optical receiving and emitting sensor 10, the distance between the first light-emitting element 14 and the measurement irradiation position M is short, making it difficult to adjust the light spot diameter using the first light-emitting side lens 191 disposed therebetween. In other words, there is a limit to how much the spot diameter of the light emitted from the first light-emitting element 14 can be increased using the first light-emitting side lens 191 in terms of lens magnification. Therefore, the configuration of this embodiment, in which the area of ​​the first light-emitting region 14a of the first light-emitting element 14 itself is increased, is particularly useful.

[0126] In this embodiment, the light receiving and emitting sensor 10 further includes a pair of bonding pads 21 provided on one surface of the wiring substrate 11 and electrically connected to the first light emitting element 14. The pair of bonding pads 21 are arranged on both sides of the first light emitting element 14 in a direction (in this embodiment, the width direction of the substrate) perpendicular to the arrangement direction of the first light emitting element 14 and the first light receiving element 15.

[0127] According to this configuration, the first light-emitting element 14 can be formed long in the substrate length direction (the direction in which the first light-emitting element 14 and the first light-receiving element 15 are aligned) without interfering with the pair of bonding pads 21. Therefore, the dimension H1 of the first light-emitting element 14 can be made as large as possible, and the dimension H1 of the first light-emitting region 14a of the first light-emitting element 14 in the substrate length direction can be made large without increasing the size of the wiring substrate 11 compared to, for example, a case in which the pair of bonding pads 21 are arranged on both sides of the first light-emitting element 14 in the substrate length direction. Therefore, the same effects as those of the above configurations can be obtained without increasing the size of the wiring substrate 11.

[0128] In addition, in this embodiment, when viewed from the direction perpendicular to the substrate, 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 the specified direction (see Figure 10).

[0129] With this configuration, the first light-emitting element 14 is disposed between the first light-receiving element 15 and the second light-receiving element 17, so the area of ​​the first light-emitting region 14a of the first light-emitting element 14 can be increased without increasing the size of the wiring board 11. That is, for example, if the first light-emitting element 14 were disposed outside the region between the first light-receiving element 15 and the second light-receiving element 17, the length of the wiring board 11 in the predetermined direction would need to be increased in order to increase the size of the first light-emitting element 14. However, with the above configuration, the size of the first light-emitting element 14 is increased within the range between the first light-receiving element 15 and the second light-receiving element 17, so the wiring board 11 does not increase in size. Therefore, the same effects as those of the above configurations can be obtained without increasing the size of the wiring board 11.

[0130] Furthermore, according to the above-described arrangement order, the second light-emitting element 16 is arranged on the outermost side of the four elements 14 to 17, and therefore the angle of incidence θ1 of light from the second light-emitting element 16 with respect to the object to be measured B can be increased as much as possible. Therefore, even if specularly reflected light emitted from the second light-emitting element 16 is unintentionally incident on the second light-receiving element 17 due to a deviation in the distance between the object to be measured B and the light-emitting and receiving sensor 10, the intensity of the light can be kept as low as possible. Consequently, the measurement accuracy of the object to be measured based on the output signal of the second light-emitting element 16 can be improved as much as possible.

[0131] In addition, in this embodiment, when viewed from the direction perpendicular to the substrate, the distance K2 between 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 larger than the distance K1 between 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.

[0132] According to this configuration, the distance between the area centroid positions C3, C4 of the second light-emitting element 16 and the second light-receiving element 17 is relatively wide, thereby making it possible to maximize the incident angle θ1 of the light emitted from the second light-emitting element 16 with respect to the measurement object B, and the distance between the area centroid positions C1, C2 of the first light-emitting element 14 and the first light-receiving element 15 is relatively narrow, thereby making it possible to minimize the incident angle θ2 of the light emitted from the first light-emitting element 14 with respect to the measurement object B. As in the former case, by making the incident angle θ1 of the light emitted from the second light-emitting element 16 as large as possible, the intensity of the specularly reflected light can be minimized, thereby reducing the effect of the specularly reflected light being incident on the second light-receiving element 17 due to a distance difference between the measurement object B and the light-emitting and receiving sensor 10. Therefore, the measurement accuracy of the measurement object value based on the output signal of the second light-receiving element 17 can be maximized. On the other hand, as in the latter case, by minimizing the incident angle θ2 of the light emitted from the first light-emitting element 14, the amount of misalignment of the specularly reflected light of the light emitted from the first light-emitting element 14 when the distance between the measurement object B and the light-receiving sensor 10 deviates from the set distance can be minimized. This minimizes the reduction in the accuracy of the measurement of the measurement object value based on the output signal of the first light-receiving element 15, which is caused by the distance between the measurement object B and the light-receiving sensor 10 deviating from the set distance. Furthermore, by increasing the incident angle of the light, the specular reflection component is reduced, and the diffuse reflection component contained in the reflected light is relatively increased. Furthermore, the difference in the diffuse reflection characteristics depending on 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 the density measurement of the color registration marks r2 to r4 based on the output signal of the second light-receiving element 17.

[0133] Furthermore, with the above configuration, by setting the distance between the second light-emitting element 16 and the second light-receiving element 17 relatively large, it is possible to minimize the transmission of heat generated by the second light-emitting element 16 to the second light-receiving element 17. This makes it possible to maximize the measurement accuracy of the measurement target value using the second light-receiving element 17.

[0134] (Embodiment 4) Figure 12 is a view corresponding to Figure 9 and shows embodiment 4. In this embodiment, the size relationship between the area of ​​the first light-receiving region 15a of the first light-receiving element 15 and the area of ​​the second light-receiving region 17a of the second light-receiving element 17 when viewed from the direction perpendicular to the substrate is different from that of embodiment 2. Except for this point, the other configuration is the same as embodiment 2. In Figure 12, the same components as those in Figure 9 are assigned the same reference numerals, and their description will be omitted as appropriate.

[0135] That is, in this embodiment, the area B1 of the first light receiving region 15a of the first light receiving element 15 (in this example, the area defined by the outer edge of the first light receiving element 15) when viewed from the direction perpendicular to the substrate is set to be larger than the area B2 of the second light receiving region 17a of the second light receiving element 17 (in this example, the area defined by the outer edge of the second light receiving element 17). In other words, the relationship B1>B2 is satisfied.

[0136] Here, the light receiving / emitting area ratio Sb (= B1 / B2) can be defined as an index showing how large the area B1 of the first light receiving area 15a of the first light receiving element 15 is set relative to the area B2 of the second light receiving area 17a of the second light receiving element 17, and it is preferable that this light receiving / emitting area ratio Sb be greater than 1.0 and not more than 1.8, and it is even more preferable that it be 1.5.

[0137] In this example, in order to achieve the above-mentioned area relationship B1>B2, the first light-receiving region 15a of the first light-receiving element 15 is formed longer in the substrate length direction (the predetermined direction) than the second light-receiving region 17a of the second light-receiving element 17. Note that in this example, the dimension of the first light-receiving region 15a of the first light-receiving element 15 and the dimension of the second light-receiving region 17a of the second light-receiving element 17 in the substrate width direction (the up-and-down direction in FIG. 12) are set to be the same. In other words, the first light-receiving region 15a of the first light-receiving element 15 is formed to be longer than the second light-receiving region 17a of the second light-receiving element 17 only in the substrate length direction.

[0138] The aspect ratio of the first light receiving region 15a of the first light receiving element when viewed from the direction perpendicular to the substrate (i.e., the value obtained by dividing the dimension H3 of the first light receiving region 15a in the substrate length direction by the dimension V3 in the substrate width direction) is set to a value larger than the aspect ratio of the second light receiving region 17a of the second light receiving element 17 (i.e., the value obtained by dividing the dimension H4 of the second light receiving region 17a in the substrate length direction by the dimension V4 in the substrate width direction).

[0139] As an example, the aspect ratio (= H3 / V3) of the first light receiving area 15a of the first light receiving element 15 is set to, for example, 1.13, and the aspect ratio (= H4 / V4) of the second light receiving area 17a of the second light receiving element 17 is set to, for example, 0.75.

[0140] [Effects] In this embodiment, when viewed from a direction perpendicular to the wiring substrate 11, the area B1 of the first light receiving region 15a of the first light receiving element 15 is set to be larger than the area B2 of the second light receiving region 17a of the second light receiving element 17.

[0141] This configuration reduces the possibility that the first light-receiving element 15 and the second light-receiving element 17 will have difficulty detecting reflected light if the distance between the measurement object B (in this example, the toner constituting the registration marks r1 to r4) and the light-emitting sensor 10 deviates from a preset distance for some reason. That is, in this embodiment, instead of increasing the area of ​​the first light-emitting region 14a of the first light-emitting element 14 as in the third embodiment, the area of ​​the first light-receiving region 15a of the first light-receiving element 15 is set larger than the area of ​​the second light-receiving region 17a of the second light-receiving element 17. This makes it easier for the first light-receiving element 15 to detect the specularly reflected light, even if the distance between the measurement object B and the light-emitting sensor 10 deviates from the preset distance, causing a misalignment of the specularly reflected light, as described above. Meanwhile, because diffusely reflected light from the measurement object B has lower optical directionality than specularly reflected light, a slight deviation in the distance between the light-emitting sensor 10 and the measurement object B is less likely to affect the detection of diffusely reflected light by the second light-receiving element 17. Therefore, in this embodiment, the area of ​​the second light receiving region 17a of the second light receiving element 17 is set smaller than the area of ​​the first light receiving region 15a of the first light receiving element 15. This reduces the possibility that the second light receiving element 17 will receive unnecessary light, thereby reducing the possibility that the accuracy of measuring the color toner density based on the output signal of the second light receiving element 17 will decrease.

[0142] Furthermore, in this embodiment, there is no need to increase the size of the first light-emitting element 14 (the area of ​​the first light-emitting region 14a), so it is possible to prevent the current flowing inside the first light-emitting element 14 from becoming uneven as its size increases, resulting in variations in light emission.

[0143] In this embodiment, the first light receiving region 15a of the first light receiving element 15 is set to be longer than the light receiving region of the second light receiving element 17 in the predetermined direction.

[0144] According to this configuration, by forming the first light receiving region 15a of the first light receiving element 15 long in a predetermined direction, which is the displacement direction of the specularly reflected light (see the two-dot chain line in FIG. 11 ), even if the reflection position of the specularly reflected light is displaced, the specularly reflected light and the first light receiving region 15a of the first light receiving element 15 overlap each other, making it easier for the first light receiving element 15 to receive the specularly reflected light. Therefore, the accuracy of measuring the black toner density based on the output signal of the first light receiving element 15 can be improved as much as possible.

[0145] In addition, in this embodiment, the distance between the first light-emitting element 14 (more specifically, the area center of gravity position of the surface of the first light-emitting element 14 facing the intermediate transfer belt 43 (the lower side in Figure 6)) and its measurement illuminated position M is set shorter than the distance between the second light-emitting element 16 (more specifically, the area center of gravity position of the surface of the second light-emitting element 16 facing the intermediate transfer belt 43 (the lower side in Figure 6)) and its measurement illuminated position M.

[0146] In this type of light receiving and emitting sensor 10, the distance between the first light emitting element 14 and the measurement irradiated position M is short, making it difficult to adjust the light spot diameter using the first light emitting side lens 191 disposed therebetween. In other words, there is a limit to how much the spot diameter of the light emitted from the first light emitting element 14 can be increased using the first light emitting side lens 191 in terms of lens magnification. Therefore, the configuration of this embodiment, in which the area of ​​the first light receiving region 15a of the first light receiving element 15 is increased rather than the light spot diameter being adjusted, is particularly useful.

[0147] (Embodiment 5) Figure 13A is a view equivalent to Figure 7 showing embodiment 5. This embodiment differs from embodiment 1 in that the elements 14 to 17 are arranged so that the first reference line L12 and the second reference line L34 intersect. The other configurations are the same as embodiment 1. In Figure 13A, the same components as those in Figure 7 are designated by the same reference numerals, and their description will be omitted as appropriate.

[0148] As shown in Figure 13A, 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 extension direction of the wiring substrate 11, while the second element substrate 12B is arranged so that its extension direction is slightly inclined with respect to the extension direction of the wiring substrate 11.

[0149] In other words, 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.

[0150] Here, the extension direction of each of the substrates 11, 12A, and 12B is the direction in which the center line of the width direction of each substrate extends, which in this example coincides with the extension direction of the long sides of the substrate. The center line of the width direction of the first element substrate 12A and the first reference line L12 coincide with each other when viewed from the substrate perpendicular direction, and the center line of the width direction of the second element substrate 12B and the second reference line L34 coincide with each other when viewed from the substrate perpendicular direction. Therefore, by tilting the second element substrate 12B as described above, the first reference line L12 and the second reference line L34 intersect when viewed from the substrate perpendicular direction.

[0151] As a result, in the direction orthogonal to the first reference line L12 (the up-down direction in FIG. 13A ), 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 spaced apart from each other. In this regard, referring to FIG. 7 of the first embodiment for comparison, in the example of FIG. 7 , 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 are arranged at the same position without being spaced apart from each other in the orthogonal direction (the up-down direction in FIG. 7 ).

[0152] [Effects] As described above, in this embodiment 5, the elements 14 to 17 are arranged so that the first reference line L12 and the second reference line L34 intersect, and therefore, in the direction perpendicular to the first reference line L12 (the up and down direction in Figure 13A), 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.

[0153] 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 light-emitting element 14, 16, the second light-receiving element 17 is positioned at a position offset from the second light-emitting element 16 in a direction perpendicular to the specular reflection direction (see FIG. 13A ). 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 prevents 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 ultimately improves the accuracy of color toner density measurement based on the output signal of the second light-emitting element 16.

[0154] 13B is a view corresponding to FIG. 7 illustrating a first modification of the fifth embodiment. The first modification is different from the fifth embodiment in that the second light-emitting element 16 on the second element substrate 12B is shifted from the center in the width direction so that the first reference line L12 and the second reference line L34 intersect.

[0155] 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. 13B ) 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. 13B ). As a result, the first reference line L12 and the second reference line L34 intersect when viewed from the direction perpendicular to the substrate.

[0156] As a result of the first reference line L12 and the second reference line L34 intersecting in this manner, the area center of gravity C4 of the second light-receiving region 17a of the second light-receiving element 17 and the area center of gravity C3 of the second light-emitting region 16a 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. 13B ). Therefore, the same effect as in the fifth 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.

[0157] 13C is a view corresponding to FIG. 7 illustrating a second modification of the fifth embodiment. The second modification differs from the fifth embodiment and the first modification in that the second element substrate 12B is tilted and the second light-emitting element 16 on the second element substrate 12B is shifted from the center in the width direction so that the first reference line L12 and the second reference line L34 intersect.

[0158] 13C , in this modification 2, the light receiving and emitting sensor 10 employs a configuration that combines the configuration of the fifth embodiment and the configuration of the first modification 1. As can be seen from Fig. 13C , in this modification 2, the intersection angle between the first reference line L12 and the second reference line L34 can be increased compared to the configuration of the fifth embodiment and the first modification 1 by combining the configuration of the fifth embodiment (the 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 the first modification 1 (the 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 are made different in the direction perpendicular to the extension direction of the second element substrate 12B).

[0159] As a result, it is possible to increase the distance between 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 first reference line L12 (the up-down direction in FIG. 13C ). Therefore, the same effect as in the fifth 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.

[0160] 14 and 15 are views corresponding to FIGS. 6 and 7, respectively, illustrating a sixth 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. The other configurations are the same as those of the sixth embodiment. In FIGS. 14 and 15, the same components as those in FIGS. 6 and 7 are designated by the same reference numerals, and their description will be omitted where appropriate.

[0161] That is, 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 all formed on the same single element substrate 13 .

[0162] 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.

[0163] Here, when forming each element 14 to 17 on one element substrate 13 (semiconductor substrate), 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.

[0164] In this embodiment, a straight line passing through the areal centroid positions 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, is defined as a third reference line L24. Furthermore, in this embodiment, a first reference line L12 and a second reference line L34 are defined as reference lines that should define the design positional relationship with respect to the third reference line L24. The second reference line L34 is a straight line passing through the areal centroid position C3 of the second light-emitting region 16a of the second light-emitting element 16 and the areal centroid position C4 of the second light-receiving region 17a of the second light-receiving element 17, and the first reference line L12 is a straight line passing through the areal centroid position C1 of the first light-emitting region 14a of the first light-emitting element 14 and the areal centroid position C2 of the first light-receiving region 15a of the first light-receiving element 15.

[0165] In this embodiment, the elements 14 to 17 are arranged such that the first reference line L12, the second reference line L34, and the third reference line L24 are aligned on the same straight line when viewed from the direction perpendicular to the substrate. Thus, in this embodiment, the positional relationship between the four elements 14 to 17 is the same as in the first embodiment.

[0166] 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 relationships of the elements 14 to 17 can be suppressed.

[0167] Furthermore, the light receiving and emitting sensor 10 of the sixth embodiment has the same configuration as that of the first embodiment except that there is only one element substrate 13, and therefore can achieve the same effects as those of the first embodiment.

[0168] (Embodiment 7) Figure 16A is a view corresponding to Figure 15 and shows embodiment 7. This embodiment differs from embodiment 6 in that, when viewed from the direction perpendicular to the substrate, the third reference line L24 and the second reference line L34 defined in embodiment 6 (Figure 15) intersect. Except for this point, the other configurations are the same as embodiment 6. In Figure 16A, the same components as those in Figure 15 are designated by the same reference numerals, and their description will be omitted as appropriate.

[0169] That is, in this embodiment, when viewed from the substrate perpendicular direction, the second light-emitting element 16 is disposed at a position offset to one side in the substrate width direction (the lower side in FIG. 16A ) from the third reference line L24. 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.

[0170] [Effects] As described above, in addition to the same effects as those of the first and sixth embodiments, the seventh embodiment further provides the following effects.

[0171] That is, in this embodiment, the third reference line L24 and the second reference line L34 intersect when viewed from the direction perpendicular to the substrate, so that in the direction perpendicular to the third reference line L24 (the up and down direction in Figure 16A), 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.

[0172] 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 light-emitting element 14, 16, the second light-receiving element 17 is positioned at a position offset from the second light-emitting element 16 in a direction perpendicular to the specular reflection direction (see FIG. 16A ). 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 prevents 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 ultimately improves the accuracy of color toner density measurement based on the output signal of the second light-emitting element 16.

[0173] (Variation of Embodiment 7) Figure 16B is a view corresponding to Figure 16A and shows Variation 1 of Embodiment 7. This variation differs from Embodiment 7 in that the first reference line L12 intersects with the third reference line L24. Note that, except for this point, the other configurations are the same as those of Embodiment 7. In Figure 16B, the same elements as those in Figure 16A are assigned the same reference numerals, and their description will be omitted as appropriate.

[0174] That is, in this modification, the first light-emitting element 14 is disposed at a position offset to one side in the board width direction from the third reference line L24, similar to the second light-emitting element 16. As a result, when viewed from the board perpendicular direction, the first reference line L12 passing through the areal center of gravity C1 of the first light-emitting region 14a of the first light-emitting element 14 and the areal center of gravity C2 of the first light-receiving region 15a of the first light-receiving element 15 intersects with the third reference line L24.

[0175] 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. 16B ) and offset amount relative to the third reference line L24. In other words, the second reference line L34 and the first reference line L12 are parallel to each other.

[0176] [Operational Effects] As described above, according to this modified example, the third reference line L24 and the second reference line L34 intersect when viewed from the direction perpendicular to the board, and therefore, operational effects similar to those of the seventh embodiment can be obtained.

[0177] 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.

[0178] 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 embodiments, for example, can be adopted.

[0179] (1) In each of the above 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 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, with 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 by 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. This reduces the possibility that the specularly reflected light of the first light-emitting element 14 will be incident on the second light-receiving element 17, thereby reducing the possibility that 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 will be reduced.

[0180] (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. In this case, 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 for 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 the electrostatic latent image corresponding to each color to correct the calculated amount of color misregistration.

[0181] (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 boards 12A and 12B (or the element board 13), but this is not limited to this. The wiring board and the element board may be integrated into a single substrate.

[0182] (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 limitative. 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).

[0183] (5) In each of the above-described embodiments and modified examples, 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).

[0184] (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.

[0185] (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 tip surface of each light-emitting element may be defined as the light-emitting region, and the tip 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.

[0186] (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 that can emit 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 that use 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 that can detect the amount of light.

[0187] (9) The light receiving and emitting sensor of the present disclosure includes any combination of the above-described embodiments and modifications.

[0188] In the above embodiments, (1) the light receiving and emitting sensor 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 substrate and a first light emitting element, a second light emitting element, a first light receiving element, and a second light receiving element provided on one surface of the substrate, wherein the first light receiving element, the first light emitting element, the second light receiving element, and the second light emitting element are arranged in this order along a predetermined direction on the one surface, 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, wherein the first light receiving element is arranged at a position where it can receive specularly reflected light of light emitted from the first light emitting element, and the second light receiving element is arranged at a position where it can receive diffusely reflected light of light emitted from the second light emitting element.

[0189] (2) In the light receiving and emitting sensor of (1) above, the area of ​​the first light receiving region may be larger than the area of ​​the second light receiving region when viewed in a direction perpendicular to the substrate.

[0190] (3) In the light receiving and emitting sensor of (1) or (2), the first light receiving region may be longer than the second light receiving region in the predetermined direction.

[0191] (4) In the light receiving and emitting sensor according to any one of (1) to (3), the area of ​​the first light emitting region may be larger than the area of ​​the second light emitting region when viewed in a direction perpendicular to the substrate.

[0192] (5) In the light receiving and emitting sensor according to any one of (1) to (4), the first light emitting region may be longer than the second light emitting region in the predetermined direction.

[0193] (6) In any one of the light receiving and emitting sensors (1) to (5), the first light emitting element and the second light emitting element are configured to emit light toward a predetermined measurement irradiated position, and the distance between the first light emitting element and the measurement irradiated position may be shorter than the distance between the second light emitting element and the measurement irradiated position.

[0194] (7) In any one of the light receiving and emitting sensors (1) to (6), when viewed from a direction perpendicular to the substrate, the distance between 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 K1, and the distance between 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 K2, the relationship K2 > K1 may be satisfied.

[0195] (8) In any one of the light receiving and emitting sensors (1) to (7), when viewed from a direction perpendicular to the 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, the first reference line and the second reference line may intersect.

[0196] (9) In any one of the light receiving and emitting sensors (1) to (8), when viewed from a direction perpendicular to the 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, the third reference line and the second reference line may intersect.

[0197] (10) In the light receiving and emitting sensor of (4), when viewed from a direction perpendicular to the substrate, the area of ​​the first light emitting region may be A1 and the area of ​​the second light emitting region may be A2, and A1 / A2 may be 1.2 or more and 1.8 or less.

[0198] (11) In the light receiving and emitting sensor of (4) or (10), when viewed from a direction perpendicular to the substrate, the dimension of the first light emitting region in the alignment direction of the first light emitting element and the first light receiving element is H1, the dimension of the first light emitting region in the direction perpendicular to the alignment direction is V1, the dimension of the second light emitting region in the alignment direction of the second light receiving element and the second light emitting element is H2, and the dimension of the second light emitting region in the direction perpendicular to the alignment direction is V2, the aspect ratio H1 / V1 of the first light emitting region may be larger than the aspect ratio H2 / V2 of the second light emitting region.

[0199] (12) In the light receiving and emitting sensor of (7), when viewed from a direction perpendicular to the substrate, the distance between the area center of gravity of the first light emitting region and the area center of gravity of the second light receiving region may be K3, and the relationship K2 > K3 may be satisfied.

[0200] (13) In the light receiving and emitting sensor of (7) or (12), when viewed from a direction perpendicular to the substrate, the distance between the center of gravity of the first light emitting region and the center of gravity of the second light receiving region may be K3, and the relationship K1 > K3 may be satisfied.

[0201] (14) An image forming apparatus including the light receiving and emitting sensor according to any one of (1) to (13).

[0202] (15) The present disclosure provides a light receiving and emitting sensor that irradiates light toward a measurement object and detects reflected light from the measurement object, the light receiving and emitting sensor comprising: a substrate; and a first light-emitting element, a second light-emitting element, a first light-receiving element, and a second light-receiving element provided on one surface of the 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 is positioned at a position where it can receive specularly reflected light of light emitted from the first light-emitting element, and the second light-receiving element is positioned at a position where it can receive diffusely reflected light of light emitted from the second light-emitting element, and the area of ​​the first light-emitting region is larger than the area of ​​the second light-emitting region when viewed from a direction perpendicular to the substrate.

[0203] (16) The present disclosure provides an optical receiving and emitting sensor that irradiates light toward an object to be measured and detects reflected light from the object to be measured, the optical receiving and emitting sensor comprising: a substrate; and a first light-emitting element, a second light-emitting element, a first light-receiving element, and a second light-receiving element provided on one surface of the 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, the first light-receiving element is disposed in a position where it can receive specularly reflected light of light emitted from the first light-emitting element, and the second light-receiving element is disposed in a position where it can receive diffusely reflected light of light emitted from the second light-emitting element, and when viewed from a direction perpendicular to the substrate, the distance between 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 K1, and the distance between 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 K2, and the optical receiving and emitting sensor satisfies the relationship K2>K1.

Claims

1. A light receiving and emitting sensor that irradiates light toward an object to be measured and detects light reflected from the object to be measured, comprising: a substrate; and a first light-emitting element, a second light-emitting element, a first light-receiving element, and a second light-receiving element provided on one surface of the substrate, wherein the first light-receiving element, the first light-emitting element, the second light-receiving element, and the second light-emitting element are arranged in this order along a predetermined direction on the one surface, wherein 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 arranged in a position where it can receive specularly reflected light of light emitted from the first light-emitting element, and the second light-receiving element is arranged in a position where it can receive diffusely reflected light of light emitted from the second light-emitting element.

2. The light receiving and emitting sensor according to claim 1, wherein the area of ​​the first light receiving region is larger than the area of ​​the second light receiving region when viewed in a direction perpendicular to the substrate.

3. A light emitting and receiving sensor according to claim 1 or 2, wherein the first light receiving region is longer than the second light receiving region in the predetermined direction.

4. The light emitting and receiving sensor according to any one of claims 1 to 3, wherein the area of ​​the first light emitting region is larger than the area of ​​the second light emitting region when viewed in a direction perpendicular to the substrate.

5. The light emitting and receiving sensor according to any one of claims 1 to 4, wherein the first light emitting region is longer than the second light emitting region in the predetermined direction.

6. A light emitting and receiving sensor according to any one of claims 1 to 4, wherein the first light emitting element and the second light emitting element are configured to emit light toward a predetermined illuminated position for measurement, and the distance between the first light emitting element and the illuminated position for measurement is shorter than the distance between the second light emitting element and the illuminated position for measurement.

7. A light receiving and emitting sensor according to any one of claims 1 to 6, wherein, when viewed from a direction perpendicular to the substrate, the distance between the area centroid position of the first light-emitting region and the area centroid position of the first light-receiving region is defined as K1, and the distance between the area centroid position of the second light-emitting region and the area centroid position of the second light-receiving region is defined as K2, and the relationship K2 > K1 is satisfied.

8. A light receiving and emitting sensor according to any one of claims 1 to 7, wherein, when viewed from a direction perpendicular to the substrate, a 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 a line passing through the center of gravity of the second light-emitting region and the center of gravity of the second light-receiving region is defined as a second reference line, the first reference line and the second reference line intersect.

9. A light receiving and emitting sensor according to any one of claims 1 to 8, wherein, when viewed from a direction perpendicular to the substrate, a line passing through the center of gravity of the second light emitting region and the center of gravity of the second light receiving region is defined as a second reference line, and a line passing through the center of gravity of the first light receiving region and the center of gravity of the second light receiving region is defined as a third reference line, and the third reference line intersects with the second reference line.

10. A light receiving and emitting sensor according to claim 4, wherein, when viewed in a direction perpendicular to the substrate, the area of ​​the first light emitting region is A1 and the area of ​​the second light emitting region is A2, A1 / A2 is 1.2 or more and 1.8 or less.

11. An optical receiving and emitting sensor according to claim 4 or 10, wherein, when viewed in a direction perpendicular to the substrate, the dimension of the first light-emitting region in the alignment direction of the first light-emitting element and the first light-receiving element is H1, the dimension of the first light-emitting region in the direction perpendicular to the alignment direction is V1, the dimension of the second light-emitting region in the alignment direction of the second light-receiving element and the second light-emitting element is H2, and the dimension of the second light-emitting region in the direction perpendicular to the alignment direction is V2, the aspect ratio H1 / V1 of the first light-emitting region is larger than the aspect ratio H2 / V2 of the second light-emitting region.

12. A light receiving and emitting sensor as defined in claim 7, wherein when viewed from a direction perpendicular to the substrate, the distance between the center of gravity of the area of ​​the first light emitting region and the center of gravity of the area of ​​the second light receiving region is K3, and the relationship K2 > K3 is satisfied.

13. A light receiving and emitting sensor according to claim 7 or 12, wherein when viewed from a direction perpendicular to the substrate, the distance between the center of gravity of the area of ​​the first light emitting region and the center of gravity of the area of ​​the second light receiving region is K3, and the relationship K1 > K3 is satisfied.

14. An image forming apparatus equipped with the light receiving and emitting sensor according to any one of claims 1 to 13.

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