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

Abstract

To prevent a reduction in measurement target value caused by detection of irregularly reflected light and regularly reflected light in a mixed state, while achieving an irregularly reflected light detection system for detecting irregularly reflected light and a regularly reflected light detection system for detecting regularly reflected light, with one light emitting and receiving sensor.SOLUTION: A light emitting and receiving sensor 10 has a substrate 11, a first light emitting element 14, a first light receiving element 15, a second light emitting element 16, and a second light receiving element 17. The first light receiving element 15 is arranged at a position where it can receive regularly reflected light of light emitted from the first light emitting element 14. The second light receiving element 17 is arranged at a position where it can receive irregularly reflected light of light emitted from the second light emitting element 16. When the distance between the area center of gravity C1 of a first light emitting area 14a of the first light emitting element 14 and the area center of gravity C2 of a first light receiving area 15a of the first light receiving element 15 is defined as K1, and the distance between the area center of gravity C3 of a second light emitting area 16a of the second light emitting element 16 and the area center of gravity C4 of a second light receiving area 17a of the second light receiving element 17 is defined as K2, K2>K1 is satisfied.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

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

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

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

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

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

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

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

[0009] 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 light reflected 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-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 relationship K2>K1 is satisfied.

[0010] An image forming apparatus according to another aspect of the present disclosure includes the light receiving and emitting sensor. [Effects of the Invention]

[0011] According to the present disclosure, a diffuse reflection light detection method for detecting diffuse reflection light and a specular reflection light detection method for detecting specular reflection light can be realized using a single light receiving and emitting sensor, while preventing a decrease in the measurement accuracy of the value to be measured due to the detection of a mixture of diffuse reflection light and specular reflection light. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an image forming apparatus equipped with a light receiving and emitting sensor according to the first embodiment. [Figure 2] FIG. 2 is an explanatory diagram for explaining the arrangement of the light receiving and emitting sensors, and is a diagram of the intermediate transfer unit as viewed from below. [Figure 3] FIG. 3 is a block diagram showing the configuration of a control system including a controller. [Figure 4] FIG. 4 is an explanatory diagram for explaining the principle of detecting black toner, where (a) shows the case where black toner is not present on the intermediate transfer belt, and (b) shows the case where black toner is present on the intermediate transfer belt. [Figure 5] Figure 5 is an explanatory diagram for explaining the principle of color toner detection, where (a) shows a case where color toner is not present on the intermediate transfer belt, and (b) shows a case where color toner is present on the intermediate transfer belt. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a schematic diagram for explaining the layout of the light receiving elements on the wiring board, and corresponds to the view seen in the direction of the arrow VII in FIG. [Figure 8] FIG. 8 is a view corresponding to FIG. 7 and shows the second embodiment. [Figure 9] FIG. 9 is an explanatory diagram showing how the position of the reflected light changes when the position of the measurement object is shifted. [Figure 10] FIG. 10 is a view corresponding to FIG. 7 and shows the third embodiment. [Figure 11] FIG. 7 is a view corresponding to FIG. 6 and showing an example of another embodiment. [Figure 12] FIG. 10 is a view equivalent to FIG. 6, showing another example of another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] (Embodiment 1) 1 is a schematic diagram showing an image forming apparatus 100 equipped with a light receiving and emitting sensor 10 according to this embodiment. The image forming apparatus 100 is configured as a tandem color printer.

[0015] [Overall configuration of image forming device] The image forming apparatus 100 includes a paper feed section 1, a vertical conveyance path 2, a pair of registration rollers 3, an intermediate transfer section 4, an image forming section 50, a secondary transfer section 6, a fixing device 7, a discharge conveyance path 8, a discharge tray 9, a light receiving and emitting sensor 10, and a controller 30 (FIG. 3). The image forming section 50 is equipped with four image forming mechanisms 5B, 5M, 5C, and 5Y.

[0016] The image forming apparatus 100 performs the following image forming process: Paper P is transported from a paper feed cassette 1a in a paper feed unit 1 to a vertical transport path 2 by a pickup roller 1b and a separation roller pair 1c (the roller pair on the left of the pickup roller 1b in FIG. 1), and is then transported to a secondary transfer unit 6 via a registration roller pair 3.

[0017] In the image forming unit 50, toner images of each color, yellow, cyan, magenta, and black, formed on each photosensitive drum 51 (the photosensitive drum 51 rotates counterclockwise in FIG. 1) serving as an image carrier are sequentially transferred in multiple layers onto an intermediate transfer belt 43 of the intermediate transfer unit 4 described below, forming a color image.

[0018] The color image formed here is secondarily transferred by the secondary transfer unit 6 from the intermediate transfer belt 43 onto the paper P conveyed from the paper feed cassette 1a. The color image is formed on the paper P.

[0019] Thereafter, the paper P onto which the unfixed color image has been transferred is separated from the intermediate transfer belt 43 and transported to the fixing device 7. Then, the amount of heat required for fixing is supplied to the paper P at the nip formed by the pressure contact between the fixing roller 7a and the pressure roller 7b, and the color image is fixed by further pressure being applied between the fixing roller 7a and the pressure roller 7b. After the fixing process has been completed in the fixing device 7, the paper P is discharged onto the discharge tray 9 via the discharge conveyance path 8. The fixing roller 7a has a built-in heater (not shown) that is controlled so that the surface of the fixing roller 7a reaches a predetermined temperature required for fixing.

[0020] 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.

[0021] Next, we will explain in detail the configuration of the image forming unit 50, which is a main component of the image forming apparatus 100. The image forming unit 50 is made up of image forming mechanisms 5B, 5M, 5C, and 5Y, and four exposure devices 53 that emit laser light corresponding to each color based on image data input from a computer or the like.

[0022] The image forming mechanisms 5B, 5M, 5C, and 5Y are arranged in a line below the intermediate transfer unit 4. The image forming mechanisms 5B, 5M, 5C, and 5Y are arranged, from the upstream side in the movement direction of the intermediate transfer belt 43, for yellow (Y), cyan (C), magenta (M), and black (B), and all consist of image forming units with substantially the same configuration. Therefore, the same reference numerals are used for parts with the same configuration in the image forming mechanisms 5B, 5M, 5C, and 5Y. In the following description of the image forming mechanisms 5B, 5M, 5C, and 5Y, the identification symbols "Y," "C," "M," and "B" are omitted unless otherwise specified, and the mechanisms are simply referred to as the image forming mechanisms 5.

[0023] The image forming mechanism 5 includes a photosensitive drum 51, a charging device 52, a primary transfer member (primary transfer roller) 54, a cleaning device 55, and a developing device 56. These components are assembled into a housing made of resin or the like to form a single unit, which is attached to the main body of the image forming apparatus 100. During image formation, in each image forming mechanism 5, the peripheral surface of each photosensitive drum 51 is uniformly charged by the charging device 52, and the charged peripheral surface of the photosensitive drum 51 is irradiated with laser light corresponding to each color based on the image data. As a result, an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 51. Developer is supplied from the developing device 56 to the electrostatic latent image, forming yellow, magenta, cyan, and black toner images on the peripheral surface of each photosensitive drum 51. These toner images are transferred onto the intermediate transfer belt 43 in a superimposed state by a transfer bias applied to the primary transfer roller 54. Residual toner on the photosensitive drum 51 that was not transferred during the primary transfer is removed by the cleaning device 55.

[0024] [Layout of light receiving and emitting sensors] The light receiving and emitting sensor 10 is a registration sensor that detects registration marks r1 to r4 (see FIG. 2) formed by the image forming mechanisms 5B, 5M, 5C, and 5Y in an end region on one side in the width direction of the intermediate transfer belt 43. The registration marks r1 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.

[0025] FIG. 2 is an explanatory diagram for explaining the arrangement of the light receiving and emitting sensors 10, and is a diagram of the intermediate transfer unit 4 as seen from below.

[0026] As shown in this figure, the light emitting and receiving sensor 10 is disposed opposite one end of the outer peripheral surface (the lower surface in this example) of the intermediate transfer belt 43 in the width direction. The light emitting and receiving sensor 10 is a reflective optical sensor that irradiates light toward the intermediate transfer belt 43, receives the reflected light (specularly reflected light and diffusely reflected light in this example), and outputs a signal (electrical signal) corresponding to the amount of reflected light received. The signal output from the light emitting and receiving sensor 10 is input to a controller 30 (described later), and the controller 30 executes calibration control (toner concentration correction processing) (described later) based on the signal received from the light emitting and receiving sensor 10. Note that the number of light emitting and receiving sensors 10 is not limited to one; for example, two light emitting and receiving sensors 10 may be disposed on both sides of the outer peripheral surface of the intermediate transfer belt 43 in the width direction.

[0027] [Control system configuration] 3 is a block diagram showing the configuration of a control system including the controller 30. The controller 30 is connected to the process device 50A, the setting operation unit 40, the light receiving and emitting sensor 10, etc. so as to be able to send and receive signals.

[0028] The process device 50A is a device necessary for the image forming process, and includes, for example, the photosensitive drum 51, the charging device 52, the exposure device 53, the developing device 56, the fixing device 7, and the like.

[0029] 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.

[0030] 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.

[0031] The print control unit 31 executes a print process on the paper P by controlling the process device 50A based on image data transmitted from an external terminal, for example.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] [Detection principle of light-emitting and receiving sensors] Next, the principle of detection of black toner and color toner by the light receiving and emitting sensor 10 will be briefly described with reference to FIGS.

[0036] 4 is an explanatory diagram for explaining the principle of detecting black toner, where (a) shows a case where black toner is not present on the intermediate transfer belt, and (b) shows a case where black toner is present on the intermediate transfer belt. In order to explain the principle, Fig. 4 shows a schematic diagram of a light-emitting element 201 that emits light, a light-receiving element 202 that receives light, and an intermediate transfer belt 203 onto which toner is transferred, separate from the actual device.

[0037] As shown in FIG. 4(a), when there is no black toner on the intermediate transfer belt 203, the light emitted from the light-emitting element 201 is specularly reflected from the surface of the intermediate transfer belt 203 and enters the light-receiving element 202. On the other hand, when there is black toner on the intermediate transfer belt 203 as shown in FIG. 4(b), a portion of the light incident on the belt 203 from the light-emitting element 201 is absorbed by the black toner, reducing the amount of specularly reflected light reflected on the intermediate transfer belt 203 and the amount of light incident on the light-receiving element 202. As a result, the magnitude of the output signal (electrical signal) output from the light-receiving element 202 also decreases. Therefore, by arranging the light-receiving element 202 in a position where it can receive the specularly reflected light of the light emitted from the light-emitting element 201, it is possible to detect the density of the black toner based on the output signal from the light-receiving element 202.

[0038] 5A and 5B are explanatory diagrams for explaining the principle of color toner detection, where (a) shows a case where color toner is not present on the intermediate transfer belt, and (b) shows a case where color toner is present on the intermediate transfer belt. In Fig. 5, a light-emitting element 301, a light-receiving element 302, and an intermediate transfer belt 303 are shown schematically, separate from the actual device.

[0039] In the example of Fig. 5, the position of the light receiving element 302 is different from that in the case of detecting black toner (in the case of Fig. 4). That is, the light receiving element 302 is disposed at a position where it can receive diffusely reflected light from color toner (in the example of this figure, it is disposed closer to the light emitting element 301 than the position where it can receive specularly reflected light).

[0040] 5(a), when there is no color toner on the intermediate transfer belt 303, the light emitted from the light-emitting element 301 is specularly reflected from the surface of the intermediate transfer belt 303, but the output signal of the light-receiving element 302 does not change because the light-receiving element 302 is not located beyond the point of this specularly reflected light. On the other hand, when there is color toner on the intermediate transfer belt 303 as shown in FIG. 5(b), part of the light incident on the intermediate transfer belt 303 from the light-emitting element 301 is diffusely reflected by the color toner and enters the light-receiving element 302. Therefore, by placing the light-receiving element 302 at a position away from the specular reflection position and at a position where it can receive the diffusely reflected light, it is possible to detect the density of the color toner based on the output signal of the light-receiving element 302.

[0041] [Details of the light receiving and emitting sensor] The light receiving and emitting sensor 10 mounted on the image forming apparatus 100 is configured to be able to detect the density of black toner and the density of color toner based on the above-mentioned detection principle.

[0042] A specific configuration of the light receiving and emitting sensor 10 will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 2. The left side of Fig. 6 corresponds to the front side of the image forming apparatus 100 (hereinafter referred to as the front side of the apparatus), and the right side of Fig. 6 corresponds to the rear side of the image forming apparatus 100 (hereinafter referred to as the rear side of the apparatus).

[0043] The light receiving and emitting sensor 10 includes a wiring board 11, a first element substrate 12A and a second element substrate 12B fixed to a main surface (one surface) of the wiring board 11, a first light emitting element 14 and a first light receiving element 15 formed on the first element substrate 12A, a second light emitting element 16 and a second light receiving element 17 formed on the second element substrate 12B, a housing 18 attached to the main surface of the wiring board 11 to form an element accommodating space S, and a lens unit 19 supported by the housing 18. In this example, the first light emitting element 14 and the second light emitting element 16 are configured as light emitting diodes (LEDs), and the first light receiving element 15 and the second light receiving element 17 are configured as photodiodes (PDs).

[0044] In the following, first, each component constituting the light receiving and emitting sensor 10 will be described, and then the arrangement and configuration of the four elements 14 to 17 will be described in detail.

[0045] 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.

[0046] The first element substrate 12A and the second element substrate 12B are formed of, for example, semiconductor substrates and are mounted (laminated) on the main surface of the wiring substrate 11. The first element substrate 12A and the second element substrate 12B are disposed adjacent to each other along the surface direction (parallel to the main surface) of the main surface of the wiring substrate 11. In this example, the semiconductor substrate is formed of a Si (silicon) substrate. The first element substrate 12A and the second element substrate 12B are both rectangular in shape and elongated in the predetermined direction (see FIG. 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.

[0047] 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).

[0048] 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.

[0049] The second light-emitting element 16 and the second light-receiving element 17 are formed on the surface of the second element substrate 12B opposite to the wiring substrate 11. The second light-emitting element 16 and the second light-receiving element 17 are an element pair provided to detect color toner, and their positions are set based on the above-mentioned color toner detection principle (see FIG. 5).

[0050] That is, the second light-emitting element 16 is positioned to emit light toward the measurement irradiation position M, and the second light-receiving element 17 is positioned so as to receive the diffusely reflected light of the light emitted from the second light-emitting element 16.

[0051] Furthermore, the second light receiving element 17 is disposed at a position where it does not detect specularly reflected light of light emitted from the second light emitting element 16. Specifically, in this example, the second light receiving element 17 is disposed on the second light emitting element 16 side (the right side in FIG. 6) of a line that passes through the measurement illuminated position M and extends in the vertical direction. In other words, the second light receiving element 17 is disposed on the opposite side (the right side in FIG. 6) of the measurement illuminated position M from the specular reflection side of light emitted from the second light emitting element 16.

[0052] Moreover, the second light receiving element 17 is disposed at a position where it does not detect specularly reflected light of light emitted from the first light emitting element 14. Specifically, in this example, the second light receiving element 17 is disposed on the side of the first light emitting element 14 opposite to the side where the first light receiving element 15 that receives the specularly reflected light is located (the specular reflection side of light).

[0053] 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).

[0054] The first light-emitting element 14 and the second light-emitting element 16 are each composed of, for example, a plurality of semiconductor layers. The plurality of semiconductor layers are formed by epitaxial growth on a semiconductor substrate (the first element substrate 12A or the second element substrate 12B) using, for example, an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus. The first light-receiving element 15 and the second light-receiving element 17 are each composed of an n-type semiconductor substrate (the first element substrate 12A or the second element substrate 12B) with a p-type semiconductor region provided thereon, thereby forming a p-n junction at the interface therebetween.

[0055] 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.

[0056] 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.

[0057] The first light receiving side lens 192 collects light emitted from the first light emitting element 14 and specularly reflected at the measurement irradiation position M, and guides the light to the first light receiving element 15 (more specifically, the first light receiving region 15a of the first light receiving element 15).

[0058] The second light-emitting side lens 193 condenses the light emitted from the second light-emitting element 16 and guides it to the irradiation position M for measurement.

[0059] The second light receiving side lens 194 collects the light emitted from the second light emitting element 16 and diffusely reflected at the measurement irradiation position M, and guides it to the second light receiving element 17 (more specifically, the second light receiving region 17a of the second light receiving element 17).

[0060] These lenses 191 to 194 are configured by, for example, convex lenses, spherical lenses, aspherical lenses, etc. It should be noted that the lenses 191 to 194 are not necessarily required.

[0061] The housing 18 prevents unintended light (stray light) from being received by the light receiving elements 15, 17. Specifically, the housing 18 has a peripheral wall portion 18a, a lid portion 18b, a first light-shielding wall 18c, and a second light-shielding wall 18d. In this example, the housing 18 is integrally molded from, for example, a resin material. The housing 18 may also be formed by combining multiple members.

[0062] Peripheral wall 18a is a frame-shaped member that surrounds an element accommodating space S that accommodates elements 14 to 17. An opening on one end of peripheral wall 18a is closed by wiring board 11, and an opening on the other end is closed by lid 18b. Thus, lid 18b, wiring board 11, and peripheral wall 18a form element accommodating space S.

[0063] The first light-shielding wall 18c and the second light-shielding wall 18d are provided to protrude from the surface of the lid portion 18b facing the wiring board 11.

[0064] The first light-shielding wall 18c is disposed so as to block the space between the first light-emitting element 14 and the first light-receiving element 15 when viewed from a direction (a direction perpendicular to the plane of the paper in FIG. 6) orthogonal to the arrangement direction (predetermined direction) of the four elements 14 to 17. In this way, the first light-shielding wall 18c prevents a portion of the light emitted from the first light-emitting element 14 from being directly detected by the first light-receiving element 15. The first light-shielding wall 18c also functions as a guide wall that guides the emitted light from the first light-emitting element 14 and the specularly reflected light of the emitted light. Further guide walls may be added along the light guide paths of the emitted light and the specularly reflected light.

[0065] 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.

[0066] [Emission control of each light-emitting element] Next, a detailed description will be given of the light emission control of the light emitting elements 14, 16 provided in the light receiving and emitting sensor 10. The light emission control of the light emitting elements 14, 16 is realized by the function of the calibration control section 32 of the controller 30.

[0067] When performing the calibration control, the calibration control unit 32 selectively causes the first light-emitting element 14 for detecting black toner or the second light-emitting element 16 for detecting color toner to emit light depending on the timing at which each of the registration marks r1 to r4 passes through the measurement irradiation position M directly above the light-emitting and receiving sensor 10.

[0068] Specifically, the calibration control unit 32 causes only the first light-emitting element 14 to emit light at the time when the black registration mark r1 passes through the measurement irradiation position M and before and after that time, and acquires (calculates) the density of the black registration mark r1 based on the magnitude of the output signal output from the first light-receiving element 15 after the emission.

[0069] 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.

[0070] [Details of the 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.

[0071] FIG. 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 are aligned, but this is not necessarily required. Furthermore, the outer edges of the first and second light-emitting elements 14 and 16 and the outer edges of the first and second light-emitting regions 14a and 16a are aligned, but this is not necessarily required. 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. Furthermore, the shape of each of the light-receiving regions 15a, 17a and each of the light-emitting regions 14a, 16a is not limited to a rectangular shape and may be, for example, a circular shape or a diamond shape.

[0072] The first light receiving element 15, the first light emitting element 14, the second light receiving element 17, and the second light emitting element 16 are arranged in this order from one side to the other side in the longitudinal direction of the wiring board 11 (a predetermined direction, which in this example is the main scanning direction).

[0073] The first light-emitting element 14 and the first light-receiving element 15 are arranged near both ends in the longitudinal direction of the first element substrate 12A. A pair of bonding pads 21 for connecting bonding wires is formed on both sides of the first light-emitting element 14 in the substrate width direction of the first element substrate 12A. The pair of bonding pads 21 are electrically connected to the first light-emitting element 14.

[0074] The second light-emitting element 16 and the second light-receiving element 17 are arranged near both ends in the longitudinal direction of the second element substrate 12B. A pair of bonding pads 22 for connecting bonding wires is formed on both sides in the substrate width direction of the second light-emitting element 16 on the second element substrate 12B. The pair of bonding pads 22 is electrically connected to the second light-emitting element 16.

[0075] 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.

[0076] 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.

[0077] Therefore, in this embodiment, a straight line passing through the areal centroid positions C1, C2 of the first light-emitting region 14a of the first light-emitting element 14 and the first light-receiving region 15a of the first light-receiving element 15, which are formed using the same photomask, is defined as a first reference line L12. Furthermore, in this embodiment, a straight line passing through the areal centroid positions C3, 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, which serves as a reference line for specifying the design positional relationship with respect to this first reference line L12. Here, the area center positions C1, C2, C3, and C4 are the centroid positions of the area defined by the outer edges of the first light-emitting area 14a, the first light-receiving area 15a, the second light-emitting area 16a, and the second light-receiving area 17a when viewed from the vertical direction of the wiring board 11 (hereinafter referred to as the board vertical direction), and are the geometric centroid positions of the area that are determined without taking into account the mass distribution within the area.

[0078] 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 substrate.

[0079] In addition, 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 passing through the center position in the width direction and extending in the predetermined direction in this example. Thus, the widthwise center line of the first element substrate 12A coincides with the first reference line L12. Furthermore, the widthwise center line of the second element substrate 12B coincides with the second reference line L34. Thus, these straight lines are all located on the same straight line.

[0080] In this embodiment, the distance between the second light-emitting element 16 and the second light-receiving element 17 in the alignment direction (predetermined direction) is set to be greater than the distance between the first light-emitting element 14 and the first light-receiving element 15 in the alignment direction (predetermined direction) (see Figures 6 and 7).

[0081] 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 7) 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 substrate perpendicular direction.

[0082] 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 7) 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.

[0083] In this example, the second separation distance K2 is set to be larger than the first separation distance K1, as shown in Fig. 7. That is, in Fig. 7, the relationship K2>K1 is satisfied.

[0084] Here, a first distance ratio R1 (=K2 / K1) can be defined as the ratio between the second separation distance K2 and the first separation distance K1, and this first distance ratio is preferably greater than 1.0 and not greater than 1.6, and even more preferably 1.3.

[0085] 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. 7, the relationships K1>K3 and K2>K3 are satisfied.

[0086] 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 or more and 1.7 or less, 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 or more and 2.1 or less, and more preferably 1.8.

[0087] [Action and effect] 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 board 11. The first light receiving element 15 is arranged at 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 at a position where it can receive diffusely reflected light of light emitted from the second light emitting element 16.

[0088] 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.

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

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

[0091] Moreover, 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. 7).

[0092] According to this configuration, it is possible to make the incident angle θ1 of the light incident from the second light emitting element 16 onto the measurement irradiation position M as large as possible, thereby making it possible to obtain the above-mentioned effects more reliably.

[0093] On the other hand, since the first separation distance K1 is relatively narrow, the incident angle 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 incident angle 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 incident angle 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.

[0094] 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.

[0095] 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.

[0096] 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 board 11. In this embodiment, when viewed from the board 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 C1 of the first light emitting region 14a of the first light emitting element 14 and the area centroid C4 of the second light receiving region 17a of the second light receiving element 17. That is, the relationship K2>K3 is satisfied (see FIG. 7).

[0097] This configuration allows the second separation distance K2 to be relatively wide, thereby 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 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 vertical 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 allows the accuracy of color toner density measurement based on the output signal of the second light-receiving element 17 to be as improved as possible.

[0098] 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.

[0099] 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 more 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.

[0100] In this embodiment, the first separation distance K1 is set to be larger than the third separation distance K3, that is, the relationship K1>K3 is satisfied (see FIG. 7).

[0101] 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 rising excessively, thereby preventing a decrease in 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 vertical direction). This makes it easier for the second light-receiving element 17 to receive diffused light from the measurement object B. This improves the accuracy of color toner density measurement based on the output signal of the second light-receiving element 17.

[0102] 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 light-receiving element 15, 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 light-receiving element 15, 17.

[0103] 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 thermally protecting the light receiving elements 15 and 17.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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, it is possible to minimize the transfer of heat between the first element substrate 12A and the second element substrate 12B. This makes it possible to more reliably prevent the heat generated by the first light-emitting elements 14 formed on the first element substrate 12A from being transmitted to the second light-receiving elements 17 formed on the second element substrate 12B.

[0108] (Embodiment 2) 8 is a view equivalent to FIG. 7 and shows embodiment 2. 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 configurations are the same as embodiment 2. In FIG. 8, the same components as those in FIG. 7 are denoted by the same reference numerals, and their description will be omitted as appropriate.

[0109] 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.

[0110] 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.

[0111] In this example, in order to achieve the area relationship A1>A2 described above, 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. 8), 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 be the same size. That is, 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.

[0112] 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).

[0113] For example, the aspect ratio (=H1 / V1) of the first light-emitting element 14 is preferably 1.5 or more and 2.1 or less, and more preferably 1.8. The aspect ratio (=H2 / V2) of the second light-emitting element 16 is preferably 1.0 or more and 1.4 or less, and more preferably 1.2.

[0114] [Action and effect] As described above, in this embodiment, 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 when viewed from the direction perpendicular to the substrate.

[0115] 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 changes from the preset distance for some reason, it is possible to prevent the first light receiving element 15 and the second light receiving element 17 from having difficulty detecting the reflected light.

[0116] That is, when the distance between the light receiving and emitting sensor 10 and the measurement object B changes, the reflection position of the specularly reflected light emitted from the first light emitting element 14 shifts in the element alignment direction (the predetermined direction). In FIG. 9, as an example, a state in which the distance has decreased due to a positional shift 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 shift 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.

[0117] 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 change in the distance between the light-receiving and -emitting sensor 10 and the measurement object B, 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, since the diffusely reflected light from the measurement object B has lower optical directionality than the specularly reflected light, a change 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 makes it possible to prevent the range of diffusely reflected light of the light emitted from the second light-emitting element 16 from unnecessarily expanding and reaching the first light-receiving element 15, for example, when detecting the toner concentration by causing the first light-emitting element 14 and the second light-emitting element 16 to emit light simultaneously. This makes it possible to prevent the first light-receiving element 15 from receiving unnecessary light, which would reduce the accuracy of measuring the black toner concentration.

[0118] In this embodiment, the first light-emitting region 14a of the first light-emitting element 14 is set to be longer than the second light-emitting region 16a of the second light-emitting element 16 in the predetermined direction.

[0119] 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. 9), 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 a change in the distance between the measurement object B and the light-receiving sensor 10 as described above, the specularly reflected light and the first light-receiving region 15a of the first light-receiving element 15 overlap, making it easier for the first light-receiving element 15 to receive the specularly reflected light. Therefore, the accuracy of measuring the concentration of black toner based on the output signal of the first light-receiving element 15 can be improved as much as possible.

[0120] 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.

[0121] 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.

[0122] (Embodiment 3) 10 is a view equivalent to FIG. 9 and shows a third embodiment. In this third 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 in the first embodiment. Except for this point, the other configuration is the same as that of the first embodiment. In FIG. 10, the same components as those in FIG. 7 are denoted by the same reference numerals, and their description will be omitted as appropriate.

[0123] 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). That is, the relationship B1>B2 is satisfied.

[0124] 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 greater than 1.8, and it is even more preferable that it be 1.5.

[0125] 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 V3 of the first light-receiving region 15a of the first light-receiving element 15 and the dimension V4 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. 10) are set to be the same size. In other words, the first light-receiving region 15a of the first light-receiving element 15 is formed so as to be longer than the second light-receiving region 17a of the second light-receiving element 17 only in the substrate length direction.

[0126] The aspect ratio of the 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 element 15 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 element 17 in the substrate length direction by the dimension V4 in the substrate width direction).

[0127] As an example, the aspect ratio (=H3 / V3) 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 element 17 is set to, for example, 0.75.

[0128] [Action and effect] In this embodiment, when viewed from a direction perpendicular to the wiring board 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.

[0129] This configuration prevents the first light-receiving element 15 and the second light-receiving element 17 from having difficulty detecting reflected light when the distance between the measurement object B (in this example, the toner constituting the registration marks r1 to r4) and the light-emitting / receiving sensor 10 changes 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 second 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 when the distance between the measurement object B and the light-emitting / receiving sensor 10 changes and the specularly reflected light is misaligned as described above. On the other hand, since the diffusely reflected light from the measurement object B has lower optical directionality than the specularly reflected light, a slight change in the distance between the light-emitting / receiving 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 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 prevents the second light receiving element 17 from receiving unnecessary light, which would reduce the accuracy of measuring the color toner density based on the output signal of the second light receiving element 17.

[0130] Moreover, in this embodiment, there is no need to increase the size of the first light-emitting element 14 (the area of ​​the 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.

[0131] 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.

[0132] 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. 9), 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 density of black toner based on the output signal of the first light receiving element 15 can be improved as much as possible.

[0133] Furthermore, 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.

[0134] In such an optical receiving and emitting sensor 10, the distance between the first light-emitting element 14 and the irradiated position for measurement 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.

[0135] (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 to this, and the following embodiment may be adopted, for example.

[0136] (1) In each of the above-described embodiments, 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 predetermined direction, but the arrangement order of the elements 14 to 17 is not limited to this and may be any order. Figures 11 and 12 are views corresponding to Figure 6 that show an example.

[0137] 11, a configuration is adopted in which the first light-emitting element 14, the first light-receiving element 15, the second light-receiving element 17, and the second light-emitting element 16 are arranged in this order along a predetermined direction (i.e., a configuration in which the first light-receiving element 15 and the first light-emitting element 14 in FIG. 6 are swapped). With this, the first light-emitting element 14, which is a heat source, is not located between the first light-receiving element 15 and the second light-receiving element 17, so the influence of heat generated by the first light-emitting element 14 on the first light-receiving element 15 and the second light-receiving element 17 can be minimized. Note that the arrangement order of the first light-receiving element 15 and the second light-receiving element 17 in FIG. 11 may also be swapped.

[0138] 12, a configuration is adopted in which the first light-emitting element 14, the first light-receiving element 15, the second light-emitting element 16, and the second light-receiving element 17 are arranged in this order along a predetermined direction (i.e., a configuration in which the second light-emitting element 16 and the second light-receiving element 17 in FIG. 11 are further swapped). In this way, the light-emitting elements 14, 16, which serve as heat sources, and the light-receiving elements 15, 17 are arranged alternately, and the heat generated from the light-emitting elements 14, 16 can be dispersed and made uniform in the longitudinal direction of the wiring board 11. Therefore, it is possible to prevent a decrease in the photoelectric conversion accuracy of the light-receiving elements 15, 17 due to a rise in temperature.

[0139] (2) In each of the above embodiments, 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, according to this arrangement, the second light-receiving element 17 is arranged on the opposite side (right side in FIG. 6 ) of the first light-emitting element 14 from the direction of light emitted from the first light-emitting element 14 (leftward in FIG. 6 ). Therefore, when control is executed to cause both the first light-emitting element 14 and the second light-emitting element 16 to emit light as described above, the specularly reflected light of the light emitted from the first light-emitting element 14 is unlikely to be received by the second light-receiving element 17. Therefore, it is possible to prevent the specularly reflected light of the first light-emitting element 14 from being incident on the second light-receiving element 17, thereby preventing a decrease in the accuracy of density measurement of the color registration marks r2 to r4 based on the output signal of the second light-receiving element 17.

[0140] (3) In the above embodiments, 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 of each color in the main scanning direction by detecting the width of this pulse signal. The calibration control unit 32 may, for example, correct the start position of the exposure device 53 writing an electrostatic latent image corresponding to each color to correct the calculated amount of color misregistration.

[0141] (4) In the above-described embodiments, two element substrates 12A and 12B (or element substrate 13) are arranged on the main surface of wiring substrate 11, but this is not limited thereto, and all of the elements 14 to 17 may be mounted on a single element substrate. Also, in the above-described embodiments, the elements 14 to 17 are mounted on the main surface of wiring substrate 11 via element substrates 12A and 12B (or element substrate 13), but this is not limited thereto, and the wiring substrate and element substrate may be integrated into a single substrate.

[0142] (5) In each of the above embodiments, both the first light-emitting element 14 and the second light-emitting element 16 are configured to emit light toward a single, common, predetermined measurement irradiation position M, but this is not limited to this. That is, the measurement irradiation position M may be set separately for each of the first light-emitting element 14 and the second light-emitting element 16. In this case, the measurement irradiation position M is set at two locations spaced apart from each other in the predetermined direction (in this example, the direction corresponding to the main scanning direction).

[0143] (6) In each of the above embodiments, the light receiving and emitting sensor 10 is arranged so that the predetermined direction, which is the arrangement direction of each of the elements 14 to 17, is along the main scanning direction, but this is not limited to this, and the predetermined direction may also be arranged so that it is along the sub-scanning direction (the movement direction of the intermediate transfer belt 43).

[0144] (7) In the above embodiments, 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.

[0145] (8) In each of the above-described embodiments, 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 may be applied.

[0146] (9) In each of the above embodiments, 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.

[0147] (10) The light receiving and emitting sensor of the present disclosure includes any combination of the configurations of the above-described embodiments. [Explanation of symbols]

[0148] 10: Light receiving and emitting sensor 11: Wiring board (substrate) 12A: First element substrate 12B: Second element substrate 13: Element substrate 14: First light-emitting element 14a: First light-emitting region 15: First light receiving element 15a: 1st light receiving area 16: Second light-emitting element 16a: Second light-emitting region 17: Second light receiving element 17a: 2nd light receiving area 21: Bonding pad 100: Image forming device B: Measurement object C1: Center of gravity of the first light-emitting area C2: Center of gravity of the first light receiving area C3: Center of gravity of the second light-emitting area C4: Center of gravity of the second light receiving area K1: 1st separation distance K2: 2nd separation distance K3: 3rd separation distance

Claims

1. A light receiving and emitting sensor that irradiates a light onto a measurement object and detects reflected light from the measurement object, A substrate; 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; the first light-emitting element includes a first light-emitting region, and the second light-emitting element includes a second light-emitting region; the first light receiving element includes a first light receiving region, and the second light receiving element includes a second light receiving region; the first light receiving element is disposed at a position where it can receive specularly reflected light of light emitted from the first light emitting element, the second light receiving element is disposed at a position where it can receive diffusely reflected light of light emitted from the second light emitting element, When viewed from a 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 light-receiving and receiving sensor satisfies the relationship K2 > K1.

2. 2. The light receiving and emitting sensor according to claim 1, 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 of the substrate, A light receiving and emitting sensor that satisfies the relationship K2>K3 when 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 is K3 when viewed from a direction perpendicular to the substrate.

3. 2. The light receiving and emitting sensor according to claim 1, 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 of the substrate, A light receiving and emitting sensor that satisfies the relationship K1>K3 when 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 is K3 when viewed from a direction perpendicular to the substrate.

4. 4. The light emitting and receiving sensor according to claim 1, The light receiving and emitting sensor has a ratio K2 / K1 of the distance K2 to the distance K1 that is greater than 1.0 and not greater than 1.

6.

5. 3. The light receiving and emitting sensor according to claim 2, The light receiving and emitting sensor has a ratio K2 / K3 of the distance K2 to the distance K3 of 1.5 or more and 2.1 or less.

6. 4. The light receiving and emitting sensor according to claim 3, The light emitting and receiving sensor has a ratio K1 / K3 of the distance K1 to the distance K3 of 1.1 or more and 1.7 or less.

7. 4. The light emitting and receiving sensor according to claim 1, a first element substrate and a second element substrate stacked on the one surface of the substrate and arranged adjacent to each other; the first light emitting element and the first light receiving element are provided on the first element substrate, The light emitting and receiving sensor, wherein the second light emitting element and the second light receiving element are provided on the second element substrate.

8. 8. The light receiving and emitting sensor according to claim 7, The light receiving and emitting sensor, wherein the first element substrate and the second element substrate are disposed adjacent to each other with a gap therebetween.

9. 2. The light receiving and emitting sensor according to claim 1, A light receiving and emitting sensor, wherein the first light receiving element, the first light emitting element, the second light receiving element, and the second light emitting element are arranged in this order along a predetermined direction on the one surface of the substrate.

10. 2. The light receiving and emitting sensor according to claim 1, An optical sensor, wherein 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 along a predetermined direction on the one surface of the substrate.

11. 2. The light receiving and emitting sensor according to claim 1, An optical sensor, wherein 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 along a predetermined direction on the one surface of the substrate.

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

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