Optical sensor module

Abstract

To provide an optical sensor module that suppresses the inclusion of light components outside the detection target and improves sensing accuracy.SOLUTION: A light sensor module comprises a sensor substrate, a lens unit, and a cover. The sensor substrate comprises a substrate having a mounting surface and a light emitting element and a light receiving element arranged on the mounting surface. The lens unit is positioned in front of the mounting surface and comprises a lens portion that focuses the measurement light emitted from the light emitting element and the reflected light incident on the light receiving element, and a holder portion surrounding the lens portion. The cover covers at least a portion of the surface of the holder portion.SELECTED DRAWING: Figure 1

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 from 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 Document 1 discloses an optical sensor module that includes a lens unit with a lens portion disposed in front of a sensor substrate on which a light-emitting element and a light-receiving element are mounted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6484331 Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical sensor module described above, it is desirable for the light receiving element to detect only the reflected light from the measurement object such as the patch image, but other light that is not intended to be detected may enter the light receiving element and hinder 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 light components that are not the detection target 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, a light-emitting element and a light-receiving element arranged on the mounting surface, a lens unit arranged in front of the mounting surface and including a lens portion that focuses measurement light emitted from the light-emitting element and reflected light incident on the light-receiving element, and a holder portion around the lens portion, and a cover that covers at least a portion of the surface of the holder portion. [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 light components that are not the detection target 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 the manner in which light is emitted and received in the first example. [Figure 6] FIG. 6 is a cross-sectional view showing an optical sensor module according to a second example of the basic embodiment. [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 shows the same cross section as FIG. 10 of the optical sensor module, and is a cross section for explaining the details of the cover and lens portion. 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] FIG. 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, a second light-shielding wall 52, and a housing 6 serving as a cover. The sensing object of the optical sensor module SM1 is a toner patch printed on the toner bearing surface 28T of the transfer belt 281. In FIG. 5A, the density detection position DP where the toner patch is formed is illustrated as an example of the sensing position.

[0022] The sensor substrate 3 includes a mounting surface 3M facing the lens unit 4 and an element group 3E arranged in a row on the mounting surface 3M. The sensor substrate 3 is mounted on a circuit board 30 on which a circuit pattern is formed. The sensor substrate 3 is disposed 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 sensor substrate 3, and the elements of the element group 3E may be 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; they may be arranged in a line with an offset that can be considered as a line. Furthermore, the arrangement direction of the element group 3E may be the sub-scanning direction. Note that the order of the elements in the first light-emitting / light-receiving pair 31 may be reversed. That is, the element group 3E may be arranged in a line on the mounting surface 3M in the order of the first light-receiving element 34, the first light-emitting element 33, the second light-receiving element 36, and the second light-emitting element 35.

[0025] The lens unit 4 is disposed in front of the mounting surface 3M, that is, between the sensor substrate 3 and the toner carrying surface 28T. The lens unit 4 includes a holder portion 40 and a lens portion that focuses light. The holder portion 40 is located around the lens portion. The holder portion 40 is a rectangular parallelepiped member and includes a first surface 4A that faces the mounting surface 3M, a second surface 4B that is opposite the first surface 4A and faces the toner carrying surface 28T, and a side surface 4C between the first surface 4A and the second surface 4B.

[0026] The lens units include a first lens unit 41, a second lens unit 42, a third lens unit 43, and a fourth lens unit 44. On the optical path of the first light-emitting / receiving pair 31, the first lens unit 41 is disposed in front of the first light-emitting element 33, and the second lens unit 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 unit 43 is disposed in front of the second light-emitting element 35, and the fourth lens unit 44 is disposed behind the second light-receiving element 36. These four lens units are held by a holder unit 40. Note that the first lens unit 41 to the fourth lens unit 44 are shown schematically in FIGS. 5A, 5B, and 6.

[0027] The first lens unit 41 focuses the light emitted by the first light-emitting element 33 to generate a first measurement light beam L11 that is irradiated as a spot onto the concentration detection position DP on the toner carrying surface 28T. The second lens unit 42 focuses the specularly reflected light beam L2 of the first measurement light beam L11 from the toner carrying surface 28T and directs it to the first light-receiving element 34. In other words, the first light-receiving element 34 is positioned to receive the specularly reflected light beam L2. The third lens unit 43 focuses the light emitted by the second light-emitting element 35 to generate a second measurement light beam L12 that is irradiated as a spot onto the concentration detection position DP. The fourth lens unit 44 focuses the diffusely reflected light beam L3 of the second measurement light beam L12 from the toner carrying surface 28T and directs it 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 beam L3 generated by the fourth lens unit 44.

[0028] 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.

[0029] The housing 6 includes a side plate 62 and a top plate 63. The housing 6 houses the sensor board 3 and the lens unit 4. The side plate 62 and the top plate 63 form a housing structure that constitutes a cover that covers at least a portion of the surface of the holder part 40. Between the housing 6 and the circuit board 30, a light-shielding wall holding part 610 is arranged that holds the first light-shielding wall 51 and the second light-shielding wall 52 in predetermined positions.

[0030] The side plate 62 covers the side surface 4C of the holder unit 40 in a manner that it is in close contact with the side surface 4C. The top plate 63 covers a portion of the second surface 4B, which is the surface on the object side of the holder unit 40. The top plate 63 has a top plate opening 63H that exposes the lens portions 41, 42, 43, and 44 of the lens unit 4. Measurement light is irradiated onto the measurement object through the top plate opening 63H, and reflected light from the measurement object is received through the top plate opening 63H. In areas other than the top plate opening 63H, the top plate 63 covers the second surface 4B in a manner that it is in close contact with the second surface 4B. The holder unit 40 has a peripheral portion that surrounds the periphery of the lens portions 41, 42, 43, and 44. The top plate 63 covers the second surface 4B at the peripheral portion. The opening edge of the top plate opening 63H is located forward near the edge of the sensor substrate 3.

[0031] In the first example of the optical sensor module SM1, the first light-emitting element 33 projects a first measurement light L11 toward the concentration detection position DP, and the first light-receiving element 34 receives the specularly reflected light L2, thereby detecting black toner BT. The second light-emitting element 35 projects a second measurement light L12 toward the concentration detection position DP, and the second light-receiving element 36 receives the diffusely reflected light L3, thereby detecting color toner CT. It is desirable for the optical sensor module SM1 to detect only the specularly reflected light L2 and the diffusely reflected light L3. However, other light not intended to be detected may enter the first light-receiving element 34 or the second light-receiving element 36 and interfere with accurate sensing. One example of such other light is external light OL, such as illumination light or natural light, present around the optical sensor module SM1.

[0032] External light OL may pass through the lens unit 4 and be received by the first light receiving element 34 or the second light receiving element 36. As indicated by the dotted arrows in FIG. 5A, external light OL easily enters the optical sensor module SM1 from the side surface 4C or the peripheral portion of the second surface 4B of the holder part 40. The external light OL that enters is reflected in multiple stages by the first surface 4A and the mounting surface 3M of the lens unit 4, becoming stray light. This stray light may be received by the first light receiving element 34 and the second light receiving element 36, superimposed on the light that should be received.

[0033] However, in the optical sensor module SM1 of this embodiment, the side surface 4C of the holder portion 40 is covered by the side plate 62, and the peripheral portion of the second surface 4B is covered by the top plate 63. In other words, the side plate 62 and the top plate 63 of the housing 6 can encase the side surface 4C of the lens unit 4 and the second surface 4B, which is the surface of the holder portion 40. This not only mechanically protects the lens unit 4 but also blocks external light OL directed toward the sensor substrate 3. This prevents external light components from entering the first light receiving element 34 and the second light receiving element 36. This improves the sensing accuracy of the optical sensor module SM1. Furthermore, the lens unit 4 can be positioned simply by fitting it into the housing 6. This simplifies the assembly of the optical sensor module SM2.

[0034] [Second example of basic embodiment] In the optical sensor module SM1 according to the first example, the opening edge of the top plate opening 63H is located forward near the edge of the sensor substrate 3. Providing such a top plate 63 is effective in suppressing the entry of external light OL. However, there is a possibility that the light emitted by the second light-emitting element 35 may be received by the second light-receiving element 36 via an unintended optical path.

[0035] 5B, of the light emitted from the second light-emitting element 35, non-measurement light L13 that is not condensed by the third lens portion 43 may pass through the holder portion 40 of the lens unit 4 and be irradiated onto the toner carrying surface 28T. If color toner is present in the area irradiated with the non-measurement light L13, diffuse reflection occurs, and some of the diffusely reflected light L14 may be incident on the second light-receiving element 36. In this case, the sensing accuracy of the optical sensor module SM1 decreases.

[0036] 6 is a cross-sectional view showing an optical sensor module SM2 according to a second example of the basic embodiment of the present disclosure. The second example is an embodiment that alleviates the problem shown in FIG. 5B. Like the first example, the optical sensor module SM2 includes a sensor substrate 3, a lens unit 4, a first light-shielding wall 51, a second light-shielding wall 52, and a housing 6. The difference from the first example is the coverage area of ​​the lens unit 4 by the top panel 63 of the housing 6.

[0037] The top plate 63 has an extension 63A that narrows the top plate opening 63H compared to the first example. The extension 63A is a portion that covers the second surface 4B of the holder 40 in front of the second light-emitting element 35 in the direction perpendicular to the mounting surface 3M. The extension 63A blocks the non-measurement light L13 emitted in a straight direction from the second light-emitting element 35. This prevents the non-measurement light L13 from passing through the holder 40 and irradiating the toner carrying surface 28T, and prevents the diffused reflection light L14 from passing through the lens unit 4 and being received by the second light-receiving element 36 or the first light-receiving element 34.

[0038] [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.

[0039] 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.

[0040] The lens unit 4 includes a lens portion 4R that focuses 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. These four lens portions 41, 42, 43, and 44 are arranged in series 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, and a second surface 4B, which is the upper surface of the holder portion 40, is recessed in the area of ​​the lens block.

[0041] 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.

[0042] The housing 6 is a rectangular parallelepiped housing including a bottom plate 61, side plates 62, and a top plate 63, and has a cavity capable of accommodating the lens unit 4. The side plates 62 and the top plate 63 are integral. The lens unit 4 is fitted into the housing 6. The bottom plate 61 faces the lower surface of the lens unit 4, i.e., the first surface 4A. The side plates 62 are rectangular tubular bodies sized to surround the periphery of the bottom plate 61 and cover the side surface 4C (see FIG. 10 ) of the holder portion 40 of the lens unit 4. The side plates 62 are bonded to the outer periphery of the bottom plate 61 and are integrated. The top plate 63 covers the upper surface of the holder portion 40, i.e., the second surface 4B. The top plate 63 has a top plate opening 63H. The top plate opening 63H exposes the lens portion 4R of the lens unit 4.

[0043] 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 were also exemplified in the basic embodiment described above, are provided upright on the top surface 61A of the bottom plate 61. The side ends of the first light-shielding wall 51 and the second light-shielding wall 52 are connected 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 an open space OS with no light-shielding objects present.

[0044] A substrate accommodating portion 612 is provided on the lower surface 61B 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.

[0045] 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.

[0046] 10 is a cross-sectional view taken along line XX in FIG. 8(B). The lens unit 4 is fitted into the housing 6 with the lens portion 4R covering the bottom plate 61 on the sensor substrate 3. The holder portion 40, which surrounds the periphery of the lens portion 4R, is sandwiched between the top plate 63 and bottom plate 61 of the housing 6. The lens unit 4 is positioned and held by the engagement of the bottom plate 61 and the side plate 62. The side plate 62 covers the side surface 4C of the holder portion 40. In other words, the side plate 62 shields the side surface 4C of the holder portion 40 from light. The top plate 63 covers the second surface 4B of the holder portion 40, shielding the second surface 4B other than the lens portion 4R from light. The side plate 62 and the top plate 63 prevent external light from entering the optical sensor module SM.

[0047] As in the second example of the basic embodiment, the top plate 63 has an extension 63A. The extension 63A covers the second surface 4B of the holder 40 in front of the second light-emitting element 35 in the direction perpendicular to the mounting surface 3M. The extension 63A blocks the non-measurement light L13 emitted in a straight direction from the second light-emitting element 35. This prevents the non-measurement light L13 from passing through the holder 40 and irradiating the toner carrying surface 28T. This prevents the reflected light of the non-measurement light L13 from re-entering the optical sensor module SM.

[0048] The lens section 4R of the lens unit 4 is disposed so as to straddle the first light-shielding wall 51 and the second light-shielding wall 52. The first light-shielding wall 51 protrudes less from the bottom plate 61 than the second light-shielding wall 52. Therefore, the lens section 4R is inclined so that the side of the first light-shielding wall 51 is lower. The four lens sections 41, 42, 43, and 44 included in the lens section 4R each have a convex lens surface on both the upper and lower surfaces of the lens unit 4.

[0049] 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.

[0050] 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.

[0051] 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 second measurement light L12 at the concentration detection position DP. 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 L3 to be incident on the second light-receiving element 36. The presence of the first light-shielding wall 51 prevents the light emitted from the first light-emitting element 33 from traveling directly toward the first light-receiving element 34. The second light-shielding wall 52 blocks the light emitted from the second light-emitting element 35 that travels directly toward the second light-receiving element 36.

[0052] 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 groups 3E in the basic embodiment shown in FIGS. 5A and 6. Therefore, specularly reflected light L2 and 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 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 first light-emitting element 33 and the first light-receiving element 34 may be reversed from that shown in FIG. 10.

[0053] [Explanation of the detailed structure of the optical sensor module] The detailed structure of the optical sensor module SM will be described with reference to Figures 11 and 12. Figure 11 is a cross-sectional view taken along line XI-XI in Figure 9(B), illustrating the state before the sensor substrate 3 is attached to the substrate accommodating portion 612 of the bottom plate 61. Figure 12 shows the same cross section as Figure 10, illustrating the state after the sensor substrate 3 has been attached to the substrate accommodating portion 612. When a sensor substrate 3 in which an element group 3E is directly formed on a semiconductor substrate is used, the sensor substrate 3 mounted on a control circuit board is attached to the substrate accommodating portion 612.

[0054] When the sensor board 3 is mounted in the board accommodation portion 612, it is desirable to form a gap between the mounting surface 3M and the bottom surfaces of the first light-shielding wall 51 and the second light-shielding wall 52 in order to suppress heat conduction. The gap is, for example, about 10 μm to several hundred μm. The first light-emitting element 33 and the second light-emitting element 35 generate heat when they perform light-emitting operation, which causes the temperature of the sensor board 3 to rise accordingly. By forming the gap, heat transfer from the sensor board 3 to the light-shielding walls 51 and 52 is suppressed, and thus thermal deformation and thermal degradation of the light-shielding walls 51 and 52 can be suppressed.

[0055] The sizes of the first light-shielding wall 51 and the second light-shielding wall 52 will be described. Both light-shielding walls 51 and 52 have a substantially triangular shape in a cross-sectional view. In terms of the forward protrusion length from the bottom plate 61, in other words, the protrusion length in the emission direction of the measurement light L11 and L12, the second light-shielding wall 52 has a longer protrusion length than the first light-shielding wall 51. The protrusion length of the second light-shielding wall 52 is approximately twice the protrusion length of the first light-shielding wall 51. In the arrangement direction of the element groups on the sensor substrate 3, the bottom width of the second light-shielding wall 52 is longer than the bottom width of the first light-shielding wall 51.

[0056] The second light-receiving element 36, which receives the diffusely reflected light L3, is prone to superimposing unnecessary stray light on the diffusely reflected light L3 that it should receive. Furthermore, as described with reference to FIGS. 3A and 4A, the emission angle θ2 of the second measurement light L12 is greater than the emission angle θ2 of the first measurement light L11. Therefore, unless a relatively high and wide wall is interposed between the second light-emitting element 35 and the second light-receiving element 36, stray light that is not directed toward the transfer belt 281 is likely to be incident on the second light-receiving element 36. As in this embodiment, by making the second light-shielding wall 52 longer than the first light-shielding wall 51 in terms of the protrusion length and the bottom width, the incidence of stray light on the second light-receiving element 36 can be suppressed.

[0057] The positional relationship between the second light-shielding wall 52 and the extension 63A of the top panel 63 will now be explained. The edge Ed of the extension 63A, which blocks the non-measurement light L13, is located between the second light-emitting element 35 and the second light-shielding wall 52. Specifically, it extends between a perpendicular line F1 extending directly above the second light-emitting element 35 and a perpendicular line F2 extending directly above the rising portion 521 of the second light-shielding wall 52. If the edge Ed is located in a position that does not exceed the perpendicular line F1, the effect of blocking the non-measurement light L13 is reduced. If the edge Ed is located in a position that exceeds the perpendicular line F2, it may block the measurement light L12. By setting the position of the edge Ed according to this embodiment, it is possible to suppress the intrusion of light components not to be detected without interfering with the irradiation of the measurement light L12.

[0058] Protrusions 47 are provided on both sides of the lens portion 4R of the lens unit 4. The protrusions 47 have a flat surface that is higher than the lens portion 4R. When viewed as a whole, the protrusions 47 are at the highest position. The edge Ed of the top plate opening 63H is adjacent to the protrusions 47. The protrusions 47 mechanically protect the lens portion 4R. Of the four lens portions provided in the lens portion 4R, the third lens portion 43 has the lens surface at the highest position. The protrusions 47 are positioned higher than the third lens portion 43. Therefore, even if the lens unit 4 hits any abutting surface, the protrusions 47 will come into contact with the abutting surface. Since the lens portion 4R does not interfere with the abutting surface, the possibility of it being damaged is reduced.

[0059] The light-emitting areas and light intensities of the first light-emitting element 33 and the second light-emitting element 35 may be set as appropriate. For example, the light-emitting area of ​​the second light-emitting element 35 that emits the second measurement light L12 that generates the diffusely reflected light L3 may be larger than the light-emitting area of ​​the first light-emitting element 33. In this embodiment, the non-measurement light L13 of the second light-emitting element 35 easily passes through the holder 40. Therefore, the advantage of covering the holder 40 with the extension 63A of the top plate 63 and blocking the non-measurement light L13 is significant. [Explanation of symbols]

[0060] 1 color printer 16 Concentration sensor (optical sensor module) 3 Sensor board 3E element group 3M mounting surface 30 boards 31 First light-emitting / receiving pair (light-emitting / receiving pair) 32 Second light-emitting / receiving pair 33 First light-emitting element (light-emitting element) 34 First light receiving element (light receiving element) 35 Second light-emitting element (light-emitting element) 36 Second light receiving element (light receiving element) 4 Lens unit 4A, 4B, 4C 1st side, 2nd side, side 4R lens section 40 Holder part 51 First Light-Shielding Wall 52 Second Light-Shielding Wall 6 Housing (cover) 61 Bottom plate 62 Side Panel 63 Top plate (cover) 63A Extension 63H Top panel opening (opening) SM, SM1, SM2 Optical Sensor Modules L11 First measuring beam L12 2nd measurement light L2 Specular reflection light L3 Diffuse reflected light Edge (edge ​​of cover)

Claims

1. a sensor substrate including a substrate having a mounting surface and a light emitting element and a light receiving element arranged on the mounting surface; a lens unit disposed in front of the mounting surface, the lens unit including a lens portion configured to collect measurement light emitted from the light-emitting element and reflected light incident on the light-receiving element, and a holder portion disposed around the lens portion; a cover that covers at least a portion of the surface of the holder portion; An optical sensor module comprising:

2. 2. The optical sensor module according to claim 1, the lens unit includes a first surface facing the mounting surface and a second surface opposite to the first surface, The cover covers at least a portion of the surface of the holder portion on the second surface.

3. 3. The optical sensor module according to claim 2, the lens unit includes a side surface between the first surface and the second surface, The cover has a housing structure including a top plate that covers at least a portion of the surface of the holder portion on the second surface, and a side plate that covers the side surface.

4. 4. The optical sensor module according to claim 3, the holder portion has a shape that surrounds the periphery of the lens portion, The top plate includes an opening that exposes the lens portion.

5. 4. The optical sensor module according to claim 3, a bottom plate that can be fitted with the cover having the housing structure; The optical sensor module, wherein the holder portion is sandwiched between the top plate and the bottom plate.

6. The optical sensor module according to any one of claims 1 to 5, 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; 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; the cover includes a portion that covers a surface of the holder portion in front of the second light-emitting element in a direction perpendicular to the mounting surface.

7. 7. The optical sensor module according to claim 6, a light-shielding wall disposed in front of the mounting surface between the second light-emitting element and the second light-receiving element, The edge of the cover is located between the second light-emitting element and the light-shielding wall.

8. 7. The optical sensor module according to claim 6, an emission area of ​​the second light-emitting element being larger than an emission area of ​​the first light-emitting element;

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