Optical sensor module

Abstract

To provide an optical sensor module capable of inhibiting stray light components from being mixed and improving sensing accuracy.SOLUTION: An optical sensor module SM comprises a sensor substrate 3, a first light-blocking wall 51 and a second light-blocking wall 52. The sensor substrate 3 includes: a substrate 30 with a mounted surface 3M; and an element group 3E in which a light-emitting receiving pair of a first light-emitting element 33 and a first light receiving element 34, a second light receiving element 34 and a second light-emitting element 36 are arranged in row on the mounted surface 3M. The first light-blocking wall 51 is arranged between the first light-emitting element 33 and the first light receiving element 34. The second light-blocking wall 52 is arranged between the second light-emitting element 35 and the second light receiving element 36. The first light receiving element 34 receives regular reflection light of first measurement light L11 emitted from the first light-emitting element 33. The second light receiving element 36 receives irregular reflection light L3 of second measurement light L12 emitted from the second light-emitting element 35. A front portion of the mounted surface 3M between the light-emitting receiving pair 31 and the second light receiving element 36 is an open space OS.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present disclosure relates to an optical sensor module including a light emitting element and a light receiving element. [Background technology]

[0002] An optical sensor module is known that includes a light-emitting element that emits measurement light to be irradiated onto a measurement object and a light-receiving element that receives reflected light of the measurement light. The optical sensor module is used, for example, to detect patch images formed on an intermediate transfer belt of a tandem image forming apparatus for measuring toner concentration and color shift. Patent Documents 1 and 2 disclose optical sensor modules that include a pair of a first light-emitting element and a first light-receiving element for detecting specularly reflected light from the patch image and a pair of a second light-emitting element and a second light-receiving element for detecting diffusely reflected light from the patch image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7195808 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-90597 Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical sensor module described above, it is desirable for each light receiving element to detect only specularly reflected light or diffusely reflected light from a measurement object such as a patch image. However, stray light that is not intended to be detected may enter the light receiving element and interfere with accurate sensing of the measurement object.

[0005] An object of the present disclosure is to provide an optical sensor module that can suppress the inclusion of stray light components and improve sensing accuracy. [Means for solving the problem]

[0006] An optical sensor module according to one aspect of the present disclosure includes a sensor substrate including a substrate having a mounting surface, and an element group arranged on the mounting surface in a row in the following order: a light-emitting and light-receiving pair of a first light-emitting element and a first light-receiving element, a second light-receiving element, and a second light-emitting element; a first light-shielding wall arranged in front of the mounting surface between the first light-emitting element and the first light-receiving element; and a second light-shielding wall arranged in front of the mounting surface between the second light-emitting element and the second light-receiving element. The first light-receiving element is positioned to receive specularly reflected light from a measurement object of first measurement light emitted from the first light-emitting element. The second light-receiving element is positioned to receive diffusely reflected light from the measurement object of second measurement light emitted from the second light-emitting element. An open space is provided in front of the mounting surface between the light-emitting and light-receiving pair and the second light-receiving element. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an optical sensor module that can suppress the inclusion of stray light components and improve sensing accuracy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view that schematically shows the internal structure of a color printer to which the optical sensor module of the present disclosure is applied. [Figure 2] FIG. 2 is a perspective view showing an example of the arrangement of a concentration sensor, which is an example of an optical sensor module. [Figure 3] 3A and 3B are schematic diagrams showing the principle of detecting black toner. [Figure 4] 4A and 4B are schematic diagrams showing the principle of color toner detection. [Figure 5A] FIG. 5A is a cross-sectional view showing an optical sensor module according to a first example of the basic embodiment of the present disclosure. [Figure 5B] FIG. 5B is a cross-sectional view showing a comparative example of the first example. [Figure 6A] FIG. 6A is a cross-sectional view showing an optical sensor module according to a second example of the basic embodiment. [Figure 6B] FIG. 6B is a cross-sectional view showing a comparative example of the second example. [Figure 7] 7A and 7B are perspective views showing the appearance of an optical sensor module according to a specific embodiment of the present disclosure. [Figure 8] 8(A) is a top view of the optical sensor module shown in FIG. 7, FIG. 8(B) is a bottom view, and FIG. 8(C) is a side view. [Figure 9] 9(A) is a perspective view of the bottom surface of the housing bottom plate, and FIG. 9(B) is a perspective view of the top surface of the housing bottom plate. [Figure 10] FIG. 10 is a cross-sectional view taken along the line XX in FIG. 8(B). [Figure 11] FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. 9(B), showing the state before the sensor substrate is mounted. [Figure 12] FIG. 12 is a cross-sectional view showing the same cross section as FIG. 11 of the housing bottom plate, with an enlarged view of the main part in a state where the sensor board is attached. [Figure 13] FIG. 13 shows the same cross section as FIG. 11 of the housing bottom plate, and is a cross section for explaining the protruding length and bottom width of the light-shielding wall. DETAILED DESCRIPTION OF THE INVENTION

[0009] The optical sensor module of the present disclosure will be described in detail below with reference to the drawings. The optical sensor module of the present disclosure is a module that measures the physical properties of an object by irradiating the object with measurement light and receiving the reflected light. There are no particular limitations on the object to be measured, and it can be a solid, semi-solid, liquid, powder, etc. There are also no particular limitations on the physical properties to be measured, as long as they can be analyzed from the reflected light. For example, the optical sensor module of the present disclosure is suitable for measuring the color and density of the object to be measured. In the embodiment described below, an optical sensor module that is installed in a color printer to detect the density of toner used in image formation is exemplified.

[0010] [Color printer instructions] First, the configuration of a color printer to which the optical sensor module of the present disclosure is applied will be described. Figure 1 is a cross-sectional view that schematically shows the internal structure of a tandem color printer 1. The color printer 1 includes image forming units 2Y, 2C, 2M, and 2Bk, an optical scanning device 23, an intermediate transfer unit 28, and a fixing unit 29, all housed in a main body housing 10. A paper output tray 11 is provided on the top surface of the main body housing 10. A sheet output port 12 opens opposite the paper output tray 11. A manual paper feed tray 13 is provided on a side wall of the main body housing 10, and a paper feed cassette 14 that stores sheets for automatic paper feeding, etc., is provided in the bottom of the main body housing 10.

[0011] Image forming units 2Y, 2C, 2M, and 2Bk are units that form toner images of yellow, cyan, magenta, and black, respectively, and are arranged in tandem at a predetermined interval horizontally. Each image forming unit 2Y, 2C, 2M, and 2Bk includes a photosensitive drum 21 having a peripheral surface that supports an electrostatic latent image and a toner image, a charger 22 that charges the peripheral surface of the photosensitive drum 21, a developer 24 that applies developer to the electrostatic latent image to form a toner image, yellow, cyan, magenta, and black toner containers 25Y, 25C, 25M, and 25Bk, respectively, that supply toner of each color to the developer 24, a primary transfer roller 26 that performs primary transfer of the toner image formed on the photosensitive drum 21, and a cleaning device 27 that removes residual toner from the peripheral surface of the photosensitive drum 21. An optical scanning device 23 scans the peripheral surface of each photosensitive drum 21 with a beam in the main scanning direction as the scanned surface, forming an electrostatic latent image on the peripheral surface for forming a toner image.

[0012] The intermediate transfer unit 28 performs primary transfer of the toner images formed on the photosensitive drums 21. The intermediate transfer unit 28 includes a transfer belt 281 that rotates while contacting the circumferential surface of each photosensitive drum 21, and a drive roller 282 and a driven roller 283 around which the transfer belt 281 is wound. The toner images on the photosensitive drums 21 of each color are primarily transferred and superimposed onto the same location on the transfer belt 281. As a result, a full-color toner image is formed on the transfer belt 281. A secondary transfer roller 154 is disposed opposite the drive roller 282, sandwiching the transfer belt 281 between them to form a secondary transfer nip T. The full-color toner image on the transfer belt 281 is secondarily transferred onto a sheet at the secondary transfer nip T.

[0013] The fixing unit 29 includes a fixing roller 291 with a built-in heat source, and a pressure roller 292 that forms a fixing nip N together with the fixing roller 291. The fixing unit 29 applies heat and pressure to the sheet, onto which a toner image has been transferred in the secondary transfer nip T, in the fixing nip N, thereby performing a fixing process in which the toner is fused to the sheet. The sheet that has undergone the fixing process is discharged from the sheet discharge port 12 toward the paper discharge tray 11.

[0014] A density sensor 16 is disposed inside the main body housing 10. The density sensor 16 is an example of an optical sensor module of the present disclosure. The density sensor 16 is disposed near the secondary transfer nip T, facing the outer circumferential surface of the transfer belt 281 on which the toner image is carried. The density sensor 16 optically detects the density of the toner image formed on the transfer belt 281 and converts it into an electrical signal.

[0015] FIG. 2 is a perspective view showing an example of the arrangement of the density sensor 16. In FIG. 2, the density sensor 16 is illustrated as a first density sensor 16A and a second density sensor 16B spaced apart from each other in the main scanning direction. The first density sensor 16A is disposed at a first density detection position DP1 on the toner carrying surface 28T of the transfer belt 281, and the second density sensor 16B is disposed at a second density detection position DP2, facing each other. The two density sensors 16A and 16B optically detect toner detection patches dp carried on the toner carrying surface 28T. The toner detection patches dp include, for example, density detection patches for detecting the toner concentration of each color and position detection patches for detecting the printing position of each color. The transfer belt 281 rotates in the direction indicated by the white arrow in FIG. 2. The first density sensor 16A detects the toner concentration along a first inspection line DL1 extending from the first density detection position DP1 in the sub-scanning direction. The second density sensor 16B detects the toner density along a second inspection line DL2 that extends in the sub-scanning direction from the second density detection position DP2. An embodiment in which only one of the first density sensor 16A and the second density sensor 16B is disposed opposite the transfer belt 281 may also be adopted.

[0016] [Toner detection principle] Next, the principle of optically detecting toner on transfer belt 281 will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram showing the detection principle of black toner BT, and Figure 4 is a schematic diagram showing the detection principle of color toner CT. A light-emitting element E1 and a light-receiving element E2 are arranged facing the toner carrying surface 28T of transfer belt 281. The light-emitting element E1 is, for example, an LED (Light Emitting Diode) that can emit light of a predetermined wavelength. The light-receiving element E2 is, for example, a PD (Photo Diode) that receives light, photoelectrically converts it, and outputs a current according to the amount of light.

[0017] FIG. 3A shows the light emission and reception state when there is no black toner BT on the transfer belt 281. The toner carrying surface 28T is a smooth surface that generates specular reflection when irradiated with light. Measurement light L1 is emitted from the light-emitting element E1. The measurement light L1 is irradiated at a predetermined emission angle θ1 toward the density detection position DP on the toner carrying surface 28T. The measurement light L1 is reflected by the toner carrying surface 28T, generating specularly reflected light L2. The specularly reflected light L2 is incident on the light-receiving element E2. The light-receiving element E2 outputs a current AM1 corresponding to the amount of light received.

[0018] FIG. 3B shows the light emission and reception state when black toner BT is present on the transfer belt 281. A portion of the measurement light L1 irradiated toward the toner carrying surface 28T is absorbed by the black toner BT. In other words, the specularly reflected light L2 is substantially not generated in the area of ​​the toner carrying surface 28T where black toner BT is present. As a result, the amount of specularly reflected light L2 incident on the light receiving element E2 decreases. The light receiving element E2 outputs a current AM2 corresponding to the reduced amount of light. Naturally, the relationship AM1>AM2 holds. Whether or not black toner BT is present is detected based on the fluctuation in the current output of the light emitting element E1 accompanying such a change in the amount of received specularly reflected light L2.

[0019] Figure 4(A) shows the light emission and reception state when no color toner CT is present on the transfer belt 281. Measurement light L1 is emitted from the light-emitting element E1. The emission optical system for measurement light L1 is adjusted so that measurement light L1 is irradiated onto the concentration detection position DP at an emission angle θ2 larger than the emission angle θ1 in Figure 3(A). Measurement light L1 is reflected by the toner carrying surface 28T, generating specularly reflected light L2. Light-receiving element E2 is positioned at a position where specularly reflected light L2 does not enter. Therefore, the output of light-receiving element E2 is essentially zero.

[0020] FIG. 4B shows the light emission and reception state when color toner CT is present on the transfer belt 281. A portion of the measurement light L1 irradiated toward the toner carrying surface 28T is irradiated onto the color toner CT and diffusely reflected. In other words, not all of the measurement light L1 becomes specularly reflected light L2, but a portion becomes diffusely reflected light L3. A portion of the generated diffusely reflected light L3 is incident on the light receiving element E2. The light receiving element E2 outputs a current AM3 corresponding to the amount of diffusely reflected light L3 received. The color toner CT is detected based on the change in output of the light receiving element E2 from 0 to AM3. The optical sensor module described in the following embodiments applies the above-described detection principle.

[0021] [First example of basic embodiment] 5A is a cross-sectional view showing an optical sensor module SM1 according to a first example of the basic embodiment of the present disclosure. The optical sensor module SM1 corresponds to the density sensor 16 of the color printer 1 illustrated in FIG. 1. The optical sensor module SM1 includes a sensor substrate 3, a lens unit 4, a first light-shielding wall 51, and a second light-shielding wall 52. The object to be measured by the optical sensor module SM1 is a toner patch printed on the toner bearing surface 28T of the transfer belt 281.

[0022] The sensor substrate 3 includes a substrate 30 having a mounting surface 3M, and an element group 3E arranged in a row on the mounting surface 3M. A circuit pattern for mounting the element group 3E is printed on the mounting surface 3M of the substrate 30. The sensor substrate 3 is arranged so that the mounting surface 3M faces the toner carrying surface 28T. A semiconductor substrate such as a silicon substrate may be used as the substrate 30, and the sensor substrate 3 may be mounted such that each element of the element group 3E is directly formed on the semiconductor substrate.

[0023] The element group 3E includes a first light-emitting / light-receiving pair 31 for detecting black toner BT and a second light-emitting / light-receiving pair 32 for detecting color toners CT. The first light-emitting / light-receiving pair 31 consists of a first light-emitting element 33 and a first light-receiving element 34 arranged at a predetermined interval on the mounting surface 3M. The second light-emitting / light-receiving pair 32 consists of a second light-emitting element 35 and a second light-receiving element 36 arranged at a predetermined interval on the mounting surface 3M at a position different from the first light-emitting / light-receiving pair 31.

[0024] The first light-emitting element 33 and the second light-emitting element 35 are LEDs that emit light of a predetermined wavelength. The first light-receiving element 34 and the second light-receiving element 36 are PDs that output a current corresponding to the amount of light received. The elements of the element group 3E are arranged in a line in the main scanning direction shown in FIG. 2. Specifically, the elements of the element group 3E are arranged in a line on the mounting surface 3M in the order of the first light-emitting element 33, the first light-receiving element 34, the second light-receiving element 36, and the second light-emitting element 35. The elements of the element group 3E do not necessarily have to be arranged in a strict line, and may be arranged in a line with an offset that is equivalent to a line. The arrangement direction of the element group 3E may also be the sub-scanning direction.

[0025] The lens unit 4 is disposed in front of the mounting surface 3M, i.e., between the sensor substrate 3 and the toner carrying surface 28T. The lens unit 4 includes a first lens portion 41, a second lens portion 42, a third lens portion 43, and a fourth lens portion 44 as lenses for condensing light. On the optical path of the first light-emitting / receiving pair 31, the first lens portion 41 is disposed in front of the first light-emitting element 33, and the second lens portion 42 is disposed behind the first light-receiving element 34. On the optical path of the second light-emitting / receiving pair 32, the third lens portion 43 is disposed in front of the second light-emitting element 35, and the fourth lens portion 44 is disposed behind the second light-receiving element 36. These four lens portions are held by a holder portion 40. Note that the first lens portion 41 to the fourth lens portion 44 are shown schematically in FIGS. 5A, 5B, and 6.

[0026] The first lens unit 41 collects light emitted by the first light-emitting element 33 to generate a first measurement light beam L11 that is irradiated as a spot at a predetermined position on the toner carrying surface 28T. The second lens unit 42 collects specularly reflected light L2 from the first measurement light beam L11 that is reflected by the toner carrying surface 28T and guides the light to the first light-receiving element 34. In other words, the first light-receiving element 34 is positioned to receive the specularly reflected light L2. The third lens unit 43 collects light emitted by the second light-emitting element 35 to generate a second measurement light beam L12 that is irradiated as a spot at a predetermined position on the toner carrying surface 28T. The fourth lens unit 44 collects diffusely reflected light L3 from the second measurement light beam L12 that is reflected by the toner carrying surface 28T and guides the light to the second light-receiving element 36. The second light-receiving element 36 is positioned to receive the optical image of the diffusely reflected light L3 generated by the fourth lens unit 44.

[0027] The first light-shielding wall 51 and the second light-shielding wall 52 are non-transparent members that do not allow light to pass through. The first light-shielding wall 51 is disposed in front of the mounting surface 3M, between the first light-emitting element 33 and the first light-receiving element 34. The first light-shielding wall 51 prevents light emitted from the first light-emitting element 33 from traveling directly toward the first light-receiving element 34 without passing through the toner carrying surface 28T. In other words, the first light-shielding wall 51 prevents light before being collected by the first lens unit 41 from being received by the first light-receiving element 34. The second light-shielding wall 52 is disposed in front of the mounting surface 3M, between the second light-emitting element 35 and the second light-receiving element 36. The second light-shielding wall 52 prevents light emitted from the second light-emitting element 35 from traveling directly toward the second light-receiving element 36. In other words, the second light-shielding wall 52 prevents light before being collected by the third lens unit 43 from being received by the second light-receiving element 36.

[0028] An open space OS is provided in front of the mounting surface 3M between the first light-emitting / receiving pair 31 and the second light-emitting / receiving pair 32, or in this embodiment, between the first light-receiving element 34 and the second light-receiving element 36. The open space OS is a non-light-shielding space in which there is essentially no light-shielding component. In other words, the open space OS is a space that does not have the light-shielding object 500 shown in FIG. 5B. The open space OS is partitioned by the first light-shielding wall 51, the second light-shielding wall 52, and the lens unit 4. Note that the open space OS does not have to be a complete space, and small protrusions or structures that do not have an optical effect may be present.

[0029] 5B is a cross-sectional view showing an optical sensor module SM1A according to a comparative example of the first example. The configuration of the optical sensor module SM1A is the same as that of the optical sensor module SM1 of the first example, except that a light-reflecting shield 500 is present in a location corresponding to the open space OS. The shield 500 is disposed in front of the mounting surface 3M, between the first light receiving element 34 and the second light receiving element 36.

[0030] If a light-shielding object 500 is present in the open space OS, in addition to the light that should be received and detected, a reflected component by the light-shielding object 500 may be incident on the first light-receiving element 34 and the second light-receiving element 36. As shown in FIG. 5B , stray light SL1 generated for some reason between the second lens unit 42 and the first light-receiving element 34 may be reflected by the light-shielding object 500 and incident on the first light-receiving element 34. For example, the stray light SL1 may be generated when a portion of the component of the first measurement light L11 that is specularly reflected by the toner carrying surface 28T passes through the second lens unit 42, and the light reflected by the light-shielding object 500 or the light sequentially reflected by the first lens unit 41 and the toner carrying surface 28T is incident on the light-receiving surface of the first light-receiving element 34. Furthermore, stray light SL2 generated for some reason between the fourth lens unit 44 and the second light-receiving element 36 may be reflected by the light-shielding object 500 and incident on the second light-receiving element 36.

[0031] In the optical sensor module SM1A of the comparative example, it may happen that the first light receiving element 34 receives light in which stray light SL1 is superimposed on specularly reflected light L2, and the second light receiving element 36 receives light in which stray light SL2 is superimposed on diffusely reflected light L3. In this case, the first light receiving element 34 and the second light receiving element 36 output a current larger than the original photoelectric conversion current, reducing sensing accuracy.

[0032] In contrast, in the optical sensor module SM1 of the first example, an open space OS is formed in front of the mounting surface 3M between the first light receiving element 34 and the second light receiving element 36. Since there is no light reflecting object such as the light blocking object 500 in the open space OS, unnecessary reflected light is unlikely to occur. This makes it possible to prevent stray light SL1, SL2 other than the specular reflected light L2 or diffuse reflected light L3 that should be detected from entering the first light receiving element 34 or the second light receiving element 36. This makes it possible to provide an optical sensor module SM1 with improved sensing accuracy.

[0033] [Second example of basic embodiment] 6A is a cross-sectional view showing an optical sensor module SM2 according to a second example of the basic embodiment of the present disclosure. Like the first example, the optical sensor module SM2 includes a sensor substrate 3, a lens unit 4, a first light-shielding wall 51, and a second light-shielding wall 52. The difference from the first example is the arrangement of the elements that make up the first light-emitting / receiving pair 31.

[0034] In the optical sensor module SM2, the elements of the element group 3E are arranged in a line in the main scanning direction on the mounting surface 3M in the following order: first light receiving element 34, first light emitting element 33, second light receiving element 36, and second light emitting element 35. That is, in the second example, the element arrangement of the second light emitting / receiving pair 32 is the same as in the first example, but the element arrangement of the first light emitting / receiving pair 31 is reversed from that in the first example. To match this element arrangement, the arrangement of the first lens portion 41 and the second lens portion 42 of the lens unit 4 in the second example is also reversed from that in the first example. An open space OS, where there is no light-shielding wall or the like, is located in front of the mounting surface 3M between the first light emitting element 33 and the second light receiving element 36. The rest of the configuration of the optical sensor module SM2 is the same as in the first example, so a description thereof will be omitted here. As is clear from the first and second examples, the open space OS may be provided between the first light emitting / receiving pair 31 and the second light receiving element 36 in front of the mounting surface 3M.

[0035] 6B is a cross-sectional view showing an optical sensor module SM2A according to a comparative example of the second example. The configuration of the optical sensor module SM2A is the same as that of the optical sensor module SM2 of the second example, except that a light-reflecting shield 500 is present in a location corresponding to the open space OS. The shield 500 is disposed in front of the mounting surface 3M, between the first light-emitting element 33 and the second light-receiving element 36.

[0036] In the optical sensor module SM2A of the comparative example, stray light SL generated for some reason between the fourth lens unit 44 and the second light receiving element 36 may be reflected by the light-shielding object 500 and enter the second light receiving element 36. In this case, the second light receiving element 36 receives light in which the stray light SL is superimposed on the diffusely reflected light L3 that should be detected. As a result, the second light receiving element 36 outputs a current greater than the intended photoelectric conversion current, resulting in reduced sensing accuracy. In contrast, in the optical sensor module SM2 of the second example, there is no light-reflecting object, such as the light-shielding object 500, in the open space OS, making it difficult for unnecessary reflected light to occur. Therefore, stray light SL other than the diffusely reflected light L3 that should be detected can be prevented from entering the second light receiving element 36. This allows for the provision of an optical sensor module SM2 with improved sensing accuracy. Furthermore, in the optical sensor module SM2 of the second example, the first light receiving element 34, the first light emitting element 33, and the second light receiving element 36 are arranged in this order, so that light is emitted from the first light emitting element 33 toward the first light receiving element 34 (to the left in FIG. 6A). Therefore, the light from the first light emitting element 33 is less likely to be incident on the second light receiving element 36.

[0037] [Specific embodiment] The first and second examples above illustrate schematic embodiments of the optical sensor module of the present disclosure. Next, a specific embodiment of the optical sensor module of the present disclosure will be described. FIG. 7(A) is a bottom perspective view showing the appearance of an optical sensor module SM according to a specific embodiment, and FIG. 7(B) is a top perspective view. FIG. 8(A) is a top view of the optical sensor module SM, FIG. 8(B) is a bottom view, and FIG. 8(C) is a side view. The optical sensor module SM also corresponds to the density sensor 16 of the color printer 1 illustrated in FIG. 1.

[0038] The optical sensor module SM includes a sensor substrate 3, a lens unit 4, and a housing 6. As shown in FIG. 8(B), the sensor substrate 3 includes a substrate 30 and an element group 3E mounted on the substrate 30, similar to the basic embodiment described above. The element group 3E includes a first light-emitting / light-receiving pair 31 for detecting black toner BT and a second light-emitting / light-receiving pair 32 for detecting color toner CT. The first light-emitting / light-receiving pair 31 is made up of a first light-emitting element 33 and a first light-receiving element 34. The second light-emitting / light-receiving pair 32 is made up of a second light-emitting element 35 and a second light-receiving element 36. The element group 3E is arranged in a row in the order of the first light-emitting element 33, the first light-receiving element 34, the second light-receiving element 36, and the second light-emitting element 35.

[0039] The lens unit 4 includes a lens portion 4R that condenses light and a holder portion 40 that holds the lens portion 4R. As in the basic embodiment described above, the lens portion 4R includes a first lens portion 41, a second lens portion 42, a third lens portion 43, and a fourth lens portion 44 (see FIG. 5A). These four lens portions 41, 42, 43, and 44 are arranged consecutively in the arrangement direction of the element group 3E to form a lens block. The holder portion 40 has a rectangular parallelepiped shape that surrounds the lens block.

[0040] The lens unit 4 further includes a cylindrical protrusion 45 and abutment portions 46 for positioning in the height direction. The cylindrical protrusion 45 protrudes from the underside of the holder portion 40. The cylindrical protrusions 45 are provided near one diagonal corner of the rectangular lens unit 4. The abutment portions 46 are provided near the other diagonal corner of the lens unit 4, and are convex portions that protrude less from the underside of the holder portion 40 than the cylindrical protrusions 45. The cylindrical protrusions 45 are protrusions for positioning the lens unit 4 in the horizontal direction. The abutment portions 46 are protrusions for positioning the lens unit 4 in the height direction. The cylindrical protrusions 45 may also be used as protrusions for positioning the optical sensor module SM itself.

[0041] The housing 6 is a rectangular parallelepiped housing that includes a bottom plate 61 and side plates 62 and has a cavity capable of accommodating the lens unit 4. The lens unit 4 is fitted into the housing 6. The bottom plate 61 faces the underside of the lens unit 4. The side plates 62 stand upright from the periphery of the bottom plate 61 and cover the side surfaces of the lens unit 4. The bottom plate 61 and the side plates 62 are engaged with each other at their engaging portions and are integrated together.

[0042] 9(A) is a perspective view of the bottom plate 61 of the housing 6 as seen from below, and FIG. 9(B) is a perspective view of the same as seen from above. The first light-shielding wall 51 and the second light-shielding wall 52, which are also illustrated in the basic embodiment, are provided upright on the top surface 61A (first surface) of the bottom plate 61. The side ends of the first light-shielding wall 51 and the second light-shielding wall 52 are connected to each other by a pair of side walls 53. As a result, a rectangular cylindrical space is formed above the top surface 61A by the first light-shielding wall 51, the second light-shielding wall 52, and the pair of side walls 53. This rectangular cylindrical space is the open space OS in this embodiment.

[0043] A substrate accommodating portion 612 is provided on a lower surface 61B (second surface) of the bottom plate 61. The substrate accommodating portion 612 is a recess that accommodates the sensor substrate 3. The bottom plate 61 has a plurality of holes formed therethrough in the thickness direction. The plurality of holes are a first opening 613, a second opening 614, a third opening 615, and a circular hole 616. When the sensor substrate 3 is accommodated in a predetermined position in the substrate accommodating portion 612, the first opening 613 is located opposite the first light-emitting element 33, the second opening 614 is located opposite the second light-emitting element 35, and the third opening 615 is located opposite the first light-receiving element 34 and the second light-receiving element 36.

[0044] Circular holes 616 are formed near each of the four corners of the rectangular bottom plate 61. The cylindrical protrusions 45 and abutment portions 46 of the lens unit 4 pass through the circular holes 616. The protruding portions of the cylindrical protrusions 45 that pass through the circular holes 616 are used to position the lens unit 4 in the horizontal direction. A circuit board (not shown) is attached below the bottom plate 61. The lower end surfaces of the abutment portions 46 abut against the circuit board that is in contact with the lower surface 61B of the bottom plate 61, thereby positioning the lens unit 4 in the vertical direction. Control ICs, electronic components, connectors, etc. for operating each element of the sensor board 3 are mounted on the circuit board.

[0045] 8(B). The lens unit 4 is fitted into the housing 6 in a manner that the lens portion 4R covers the bottom plate 61 on the sensor substrate 3. The first light-shielding wall 51 protrudes less from the bottom plate 61 than the second light-shielding wall 52. Therefore, the lens portion 4R, which is disposed so as to straddle the first light-shielding wall 51 and the second light-shielding wall 52, is inclined so that the side of the first light-shielding wall 51 is lower. Note that the four lens portions 41, 42, 43, and 44 included in the lens portion 4R may each have a convex lens surface on both the upper and lower surfaces of the lens unit 4.

[0046] 10 shows a state in which the optical sensor module SM emits the first measurement light L11 and the second measurement light L12 toward the density detection position DP where the measurement object TG is printed on the toner carrying surface 28T of the transfer belt 281. It also shows a state in which the specularly reflected light L2 and the diffusely reflected light L3 from the measurement object TG are incident on the optical sensor module SM. As described above, the measurement object TG is black toner BT and color toner CT.

[0047] The first lens unit 41 is disposed at a position facing the first opening 613 of the bottom plate 61. The first lens unit 41 collects light emitted from the first light-emitting element 33 and passing through the first opening 613, and irradiates the first measurement light L11 at the concentration detection position DP. The second lens unit 42 and the fourth lens unit 44 are disposed at a position facing the third opening 615 across the open space OS. The second lens unit 42 collects specularly reflected light L2 of the first measurement light L11 from the concentration detection position DP, and directs the light to the first light-receiving element 34. The first light-shielding wall 51 blocks light emitted from the first light-emitting element 33 that directly travels toward the first light-receiving element 34.

[0048] The third lens unit 43 is disposed at a position facing the second opening 614. The third lens unit 43 collects light emitted from the second light-emitting element 35 and passing through the second opening 614, and irradiates the concentration detection position DP with the second measurement light L12. The fourth lens unit 44 collects a portion of the diffusely reflected light of the second measurement light L12 generated at the concentration detection position DP, and causes the diffusely reflected light to be incident on the second light-receiving element 36 as diffusely reflected light L3. The second light-shielding wall 52 blocks light emitted from the second light-emitting element 35 that directly travels toward the second light-receiving element 36.

[0049] The arrangement order of the element groups on the sensor substrate 3 in this embodiment is the same as the arrangement order of the element group 3E in the first example of the basic embodiment shown in FIG. 5A above. Therefore, the specularly reflected light L2 and the diffusely reflected light L3 pass through the open space OS. There are substantially no light-reflecting objects in the open space OS, i.e., between the first light-shielding wall 51 and the second light-shielding wall 52. Therefore, unnecessary reflected light is less likely to occur between the first light-shielding wall 51 and the second light-shielding wall 52. Therefore, stray light other than the specularly reflected light L2 or the diffusely reflected light L3 that should be detected can be prevented from entering the first light-receiving element 34 or the second light-receiving element 36. The arrangement order of the element group 3E in the second example shown in FIG. 6A may also be applied to this embodiment. In this case, the light passing through the open space OS becomes the first measurement light L11 and the diffusely reflected light L3.

[0050] [Shading wall details] 11 is a cross-sectional view taken along line XI-XI in FIG. 9(B), illustrating the state before the sensor substrate 3 is attached to the substrate accommodating portion 612 of the bottom plate 61. FIG. 12 is a cross-sectional view showing the same cross section as FIG. 11, with an enlarged view of a main part, illustrating the state after the sensor substrate 3 is attached to the substrate accommodating portion 612. The state in FIG. 12 illustrates the positional relationship between the bottom plate 61 and the sensor substrate 3 in the completed state of the optical sensor module SM shown in FIG.

[0051] When the sensor board 3 is mounted in a predetermined position in the board accommodating section 612, it is desirable to form a gap G between the mounting surface 3M of the sensor board 3 and the bottom surface 51B of the first light-shielding wall 51 and the bottom surface 52B of the second light-shielding wall 52, as shown in the enlarged view of a main part in FIG. 12 . The first light-emitting element 33 and the second light-emitting element 35, which are LEDs, generate heat when they emit light. This causes the sensor board 3 to become hot. If the mounting surface 3M and the bottom surfaces 51B and 52B are in contact with each other, heat is conducted from the sensor board 3 to the first light-shielding wall and the second light-shielding wall. In this case, thermal deformation or thermal degradation of the first light-shielding wall 51 and the second light-shielding wall 52 may become apparent.

[0052] By forming the gap G, it is possible to block a direct heat conduction path between the mounting surface 3M and the bottom surfaces 51B, 52B. Therefore, it is possible to suppress thermal deformation and thermal deterioration of the light-shielding walls 51, 52. The gap G can be set to, for example, about 10 μm to several hundred μm. The gap G may be adjusted, for example, by adjusting the height of the abutment portion 46. Note that if thermal deformation of the light-shielding walls 51, 52 is not an issue, the mounting surface 3M may abut the bottom surfaces 51B, 52B.

[0053] A first tapered surface 54 and a second tapered surface 55 are formed on the bottom surfaces 51B, 52B of the light-shielding walls 51, 52. The first tapered surface 54 is formed in a region of the bottom surface 51B of the first light-shielding wall 51 closer to the first light-emitting element 33. The first tapered surface 54 is a tapered surface that slopes upward, i.e., away from the mounting surface 3M, as it approaches the first light-emitting element 33. The second tapered surface 55 is formed in a region of the bottom surface 52B of the second light-shielding wall 52 closer to the second light-emitting element 35. The second tapered surface 55 is a tapered surface that slopes upward, away from the mounting surface 3M, as it approaches the second light-emitting element 35. As a result, the gap G is a tapered space that widens toward the light-emitting elements 33, 35. An embodiment in which either the first tapered surface 54 or the second tapered surface 55 is not formed may be adopted.

[0054] When a gap G is formed between the mounting surface 3M of the sensor substrate 3 and the bottom surfaces 51B, 52B, light may pass through the gap G from the first light-emitting element 33 directly toward the first light-receiving element 34. Similarly, light may pass through the gap G from the second light-emitting element 35 directly toward the second light-receiving element 36. The first tapered surface 54 and the second tapered surface 55 serve to return light that passes directly toward the light-receiving element side back toward the light-emitting element side.

[0055] 12 includes an enlarged view of the periphery of the second tapered surface 55. As indicated by the arrows in the figure, light traveling toward the second light receiving element 36 is reflected in multiple stages in the tapered space between the second tapered surface 55 and the mounting surface 3M, increasing the probability that the light will be returned toward the second light emitting element 35. If the bottom surface 52B and the mounting surface 3M were parallel, the light emitted from the second light emitting element 35 toward the second light receiving element 36 would simply be reflected between the bottom surface 52B and the mounting surface 3M while traveling through the gap G, making it more likely to reach the second light receiving element 36.

[0056] Referring to FIG. 13, an explanation is added regarding the sizes of the first light-shielding wall 51 and the second light-shielding wall 52. In the protruding length from the bottom plate 61 forward, in other words, in the protruding length in the emission directions of the measurement lights L11 and L12, the second light-shielding wall 52 has a longer protruding length than the first light-shielding wall 51. In FIG. 13, the protruding length of the first light-shielding wall 51 from the upper surface 61A of the bottom plate 61 is indicated by H1. The protruding length H2 of the second light-shielding wall 52 is about twice the length of H1.

[0057] Unwanted stray light is likely to be superimposed on the irregular reflection light L3 received by the second light-receiving element 36, which is the light that should originally be received. Also, as described based on FIGS. 3(A) and 4(A), the emission angle θ2 of the second measurement light L12 is larger than the emission angle θ1 of the first measurement light L11. Therefore, unless a relatively high wall is interposed between the second light-emitting element 35 and the second light-receiving element 36, unwanted stray light that does not go toward the transfer belt 281 is likely to enter the second light-receiving element 36. Therefore, by setting the relationship as H1 < H2, the entry of the stray light into the second light-receiving element 36 can be suppressed.

[0058] In the arrangement direction of the element group on the sensor substrate 3, the bottom width W2 of the second light-shielding wall 52 is longer than the bottom width W1 of the first light-shielding wall 51. The bottom width W2 has a length of twice or more the bottom width W1. By setting the relationship as W1 < W2, the width that can be shielded between the second light-emitting element 35 and the second light-receiving element 36 becomes longer. Therefore, it becomes easier to shield the stray light. Thus, by satisfying both the relationship of H1 < H2 and the relationship of W1 < W2, the entry of stray light into the second light-receiving element 36 can be more effectively suppressed.

[0059] [Summary of the Present Disclosure] The specific embodiments described above include the following disclosed configurations.

[0060] An optical sensor module according to one aspect of the present disclosure comprises a sensor substrate including a substrate having a mounting surface, and a group of elements arranged in a row on the mounting surface in the following order: a light-emitting / receiving pair of a first light-emitting element and a first light-receiving element, a second light-receiving element, and a second light-emitting element; a first light-shielding wall arranged in front of the mounting surface between the first light-emitting element and the first light-receiving element; and a second light-shielding wall arranged in front of the mounting surface between the second light-emitting element and the second light-receiving element, wherein the first light-receiving element is arranged in a position to receive specularly reflected light from a measurement object of the first measurement light emitted from the first light-emitting element, and the second light-receiving element is arranged in a position to receive diffusely reflected light from the measurement object of the second measurement light emitted from the second light-emitting element, and an open space is provided in front of the mounting surface between the light-emitting / receiving pair and the second light-receiving element.

[0061] According to this aspect, an open space without a light-shielding wall or the like is formed between the light-emitting / receiving pair of the first light-emitting element and the first light-receiving element and the second light-receiving element. Since there are no objects that reflect light in the open space, unnecessary reflected light is less likely to occur. Therefore, stray light other than the specularly reflected light or diffusely reflected light that should be detected can be prevented from entering the first light-receiving element or the second light-receiving element. Therefore, the sensing accuracy of the optical sensor module can be improved. The "forward" direction of the mounting surface corresponds to the direction in which the first measurement light and the second measurement light are emitted.

[0062] In the above-mentioned optical sensor module, the element group may be arranged in a row on the mounting surface in the order of the first light-emitting element, the first light-receiving element, the second light-receiving element, and the second light-emitting element, and the front of the mounting surface between the first light-receiving element and the second light-receiving element may be the open space.

[0063] In this arrangement of the light-emitting element and the light-receiving element, if an object such as a light-shielding wall is present in the open space, stray light generated by light other than specularly reflected light reflecting off the object may be superimposed on the specularly reflected light and incident on the first light-receiving element. Furthermore, stray light generated by light other than diffusely reflected light that should be incident on the second light-receiving element reflecting off the object may be superimposed on the second light-receiving element. As a result, the first light-receiving element and the second light-receiving element may detect a greater amount of light than they should, resulting in a decrease in sensing accuracy. According to the above-described embodiment, such a decrease in sensing accuracy can be suppressed.

[0064] In the above-mentioned optical sensor module, the element group may be arranged in a row on the mounting surface in the order of the first light receiving element, the first light emitting element, the second light receiving element, and the second light emitting element, and the front of the mounting surface between the first light emitting element and the second light receiving element may be the open space.

[0065] In this arrangement of the light-emitting element and the light-receiving element, if an object such as a light-shielding wall is present in the open space, stray light generated by light other than the diffused light that should be incident on the second light-receiving element being reflected by the object may be superimposed on the second light-receiving element. As a result, the second light-receiving element may detect a greater amount of light than it should, resulting in a decrease in sensing accuracy. According to the above embodiment, such a decrease in sensing accuracy can be suppressed.

[0066] The optical sensor module may further include a lens unit arranged in front of the mounting surface and including a lens portion that focuses the first measurement light and the specularly reflected light, and the second measurement light and the diffusely reflected light, and a housing into which the lens unit is fitted, and the first light-shielding wall and the second light-shielding wall may be erected on the housing.

[0067] According to this aspect, the light-collecting effect of the lens section allows for efficient sensing. Another advantage is that the housing into which the lens unit is fitted can be used to accurately position the first and second light-shielding walls relative to the lens section.

[0068] In the above-mentioned optical sensor module, the housing may include a bottom plate and side plates that stand up from the periphery of the bottom plate and cover the side surfaces of the lens unit, and the bottom plate may include a first surface on which the first light-shielding wall and the second light-shielding wall are stood up, a second surface having a recess in which the sensor substrate is housed, and openings that allow the first measurement light and the specularly reflected light, and the second measurement light and the diffusely reflected light to pass through.

[0069] According to this aspect, the bottom plate of the housing has a recess, which allows the bottom plate to have a positioning function for the sensor board, thereby simplifying the assembly work of the optical sensor module.

[0070] In the optical sensor module, a gap may be formed between the mounting surface and the bottom surfaces of the first light-shielding wall and the second light-shielding wall.

[0071] Generally, light-emitting elements generate heat when they emit light. According to the above aspect, the formation of the gap can suppress heat conduction from the sensor substrate on which the first light-emitting element and the second light-emitting element are mounted to the first light-shielding wall and the second light-shielding wall. Therefore, thermal deformation and thermal deterioration of the first light-shielding wall and the second light-shielding wall can be suppressed.

[0072] The optical sensor module may include a first tapered surface formed on a bottom surface of the first light-shielding wall and inclined in a direction away from the mounting surface toward the first light-emitting element, and a second tapered surface formed on a bottom surface of the second light-shielding wall and inclined in a direction away from the mounting surface toward the second light-emitting element.

[0073] When the above-mentioned gaps are formed between the mounting surface and the first and second light-shielding walls, light may travel directly from the first light-emitting element to the first light-receiving element, and light may travel directly from the second light-emitting element to the second light-receiving element. According to the above-mentioned aspect, the first tapered surface and the second tapered surface can reflect the light that would otherwise travel directly from the light-emitting element to the light-receiving element, and return it to the light-emitting element side.

[0074] In the optical sensor module, the second light-shielding wall may have a longer forward protrusion length than the first light-shielding wall.

[0075] In the second light receiving element that receives the diffusely reflected light, unnecessary stray light is likely to be superimposed on the diffusely reflected light that should be received. According to the above aspect, by using the second light-shielding wall that has a longer protrusion length than the first light-shielding wall, the height that can be blocked is increased, making it easier to block the stray light.

[0076] In the above optical sensor module, the second light-shielding wall may have a bottom width greater than the bottom width of the first light-shielding wall in the row arrangement direction.

[0077] According to this aspect, by using the second light-shielding wall having a longer bottom width than the first light-shielding wall, the width that can be shielded is increased, making it easier to shield the stray light. In this aspect, if the second light-shielding wall has a longer protrusion length than the first light-shielding wall, it becomes even easier to shield the stray light.

[0078] In the above-mentioned optical sensor module, the open space is a space partitioned by the first light-shielding wall, the second light-shielding wall, and a pair of side walls connecting the ends of the first light-shielding wall and the second light-shielding wall, and the open space may be positioned at a position through which the first measurement light or the specularly reflected light and the diffusely reflected light pass.

[0079] According to this aspect, an open space is formed between the first and second light-shielding walls. In other words, no object that reflects light exists between the first and second light-shielding walls. Therefore, it is possible to make it more difficult for unnecessary reflected light to occur between the first and second light-shielding walls. [Explanation of symbols]

[0080] 1 color printer 16 Concentration sensor (optical sensor module) 3 Sensor board 3E element group 3M mounting surface 30 boards 31, 32 First light-emitting / receiving pair (light-emitting / receiving pair), second light-emitting / receiving pair 32 33, 34 First light emitting element, first light receiving element 35, 36 Second light emitting element, second light receiving element 36 4 Lens unit 4R lens section 51 First Light-Shielding Wall 52 Second Light-Shielding Wall 53 Side wall (pair of side walls) 54, 55 First tapered surface, second tapered surface 6. Housing 61 Bottom plate 61A, 61B Top surface (first surface), bottom surface (second surface) 612 Substrate accommodation section (recess) 613, 614, 615 1st opening, 2nd opening, 3rd opening (opening) 62 Side Panel G Gap H1, H2 protrusion length L11, L12 First measuring beam, second measuring beam L2 Specular reflection light L3 Diffuse reflected light OS open space SM, SM1, SM2 Optical Sensor Modules TG measurement object W1, W2 bottom width

Claims

1. a sensor substrate including a substrate having a mounting surface, and an element group arranged in a row on the mounting surface in the order of a light emitting / receiving pair of a first light emitting element and a first light receiving element, a second light receiving element, and a second light emitting element; a first light-shielding wall disposed in front of the mounting surface between the first light-emitting element and the first light-receiving element; a second light-shielding wall disposed in front of the mounting surface between the second light-emitting element and the second light-receiving element, the first light receiving element is disposed at a position where it receives specularly reflected light of the first measurement light emitted from the first light emitting element by the measurement object; the second light receiving element is disposed at a position where it receives diffused light of the second measurement light emitted from the second light emitting element and reflected from the measurement object; an open space in front of the mounting surface between the light emitting and receiving pair and the second light receiving element;

2. 2. The optical sensor module according to claim 1, the element group is arranged on the mounting surface in a row in the order of the first light-emitting element, the first light-receiving element, the second light-receiving element, and the second light-emitting element; the open space is in front of the mounting surface between the first light receiving element and the second light receiving element.

3. 2. The optical sensor module according to claim 1, the element group is arranged on the mounting surface in a row in the order of the first light receiving element, the first light emitting element, the second light receiving element, and the second light emitting element, the open space is in front of the mounting surface between the first light-emitting element and the second light-receiving element.

4. The optical sensor module according to any one of claims 1 to 3, a lens unit disposed in front of the mounting surface and including a lens portion configured to condense the first measurement light and the specular reflection light, and the second measurement light and the diffuse reflection light; a housing into which the lens unit is fitted, The optical sensor module, wherein the first light-shielding wall and the second light-shielding wall are provided upright on the housing.

5. 5. The optical sensor module according to claim 4, the housing includes a bottom plate and side plates extending from a peripheral edge of the bottom plate and covering side surfaces of the lens unit; The bottom plate includes a first surface on which the first light-shielding wall and the second light-shielding wall are erected, a second surface having a recess in which the sensor substrate is housed, and an opening that allows the first measurement light and the specularly reflected light, and the second measurement light and the diffusely reflected light to pass through.

6. The optical sensor module according to any one of claims 1 to 3, A gap is formed between the mounting surface and bottom surfaces of the first light-shielding wall and the second light-shielding wall.

7. 7. The optical sensor module according to claim 6, a first tapered surface formed on a bottom surface of the first light-shielding wall, the first tapered surface inclined in a direction away from the mounting surface as it approaches the first light-emitting element.

8. 7. The optical sensor module according to claim 6, a second tapered surface formed on a bottom surface of the second light-shielding wall, the second tapered surface inclined in a direction away from the mounting surface as it approaches the second light-emitting element.

9. The optical sensor module according to any one of claims 1 to 3, The second light-shielding wall has a longer forward protrusion length than the first light-shielding wall.

10. The optical sensor module according to any one of claims 1 to 3, The optical sensor module, wherein the width of the bottom surface of the second light-shielding wall is greater than the width of the bottom surface of the first light-shielding wall in the row arrangement direction.

11. 10. The optical sensor module according to claim 9, The optical sensor module, wherein the width of the bottom surface of the second light-shielding wall is greater than the width of the bottom surface of the first light-shielding wall in the row arrangement direction.

12. The optical sensor module according to any one of claims 1 to 3, the open space is a space defined by the first light-shielding wall, the second light-shielding wall, and a pair of side walls connecting ends of the first light-shielding wall and the second light-shielding wall, The open space is disposed at a position through which the first measurement light or the specularly reflected light and the diffusely reflected light pass.

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