Optical Sensors

Abstract

To prevent a reduction in detection accuracy that may be caused by reflected light from a surface to be irradiated in an optical sensor, such as a toner sensor.SOLUTION: A housing has a first opening and a second opening. The first opening is provided in a first light guide path arranged between a light emitting device and a first area to be irradiated of a surface to be irradiated. The first opening is arranged such that light output from the light emitting device is directed to the first area to be irradiated. The second opening is provided in a second light guide path arranged between the first area to be irradiated and a first light receiving unit. The second opening is arranged such that irregularly reflected light from a toner image passes the second opening when the toner image passes through the first area to be irradiated, and regularly reflected light and irregularly reflected light or diffraction light from a surface of a rotating body do not pass through the second opening when the surface passes through the first area to be irradiated.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an optical sensor and an image forming apparatus. [Background technology]

[0002] An image forming apparatus forms a toner image on a photosensitive drum, transfers the toner image from the photosensitive drum to an intermediate transfer body, and further transfers the toner image from the intermediate transfer body to a sheet. In particular, an optical sensor is used to check the transfer position and color reproducibility of the toner image (Patent Document 1). Such an optical sensor is called a toner sensor. Toner remaining on the intermediate transfer body is cleaned by a cleaning blade. In order to improve the durability of this cleaning blade, an uneven shape such as grooves may be formed on the surface of the intermediate transfer body (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-191835 A [Patent Document 2] JP 2015-125187 A [Patent Document 3] JP 2013-044878 A Summary of the Invention [Problem to be solved by the invention]

[0004] The toner sensor receives specularly reflected light from the surface (base) of the intermediate transfer body to detect the intermediate transfer body, and receives diffusely reflected light from the toner to detect the toner. However, when grooves or the like are formed on the surface of the intermediate transfer body, the specularly reflected light from the base decreases and the diffusely reflected light from the base increases. As a result, it becomes difficult to accurately detect the specularly reflected light from the base. Furthermore, when detecting the toner, the diffusely reflected light from the base enters the toner sensor, making it difficult to accurately detect the toner. Therefore, an object of the present invention is to suppress a decrease in detection accuracy that may occur due to reflected light from the irradiated surface in an optical sensor such as a toner sensor. [Means for solving the problem]

[0005] The present invention relates to, for example, A light emitting element that irradiates light onto an illuminated surface that is set on a part of the surface of a rotating body; a first light receiving unit that receives diffusely reflected light from a toner image formed on a surface of a rotating body; and a second light receiving unit that receives specularly reflected light from the surface of the rotating body; a circuit board on which the light emitting element, the first light receiving unit, and the second light receiving unit are mounted; a housing having a first opening and a second opening, the housing being provided to surround the light emitting element, the first light receiving unit, and the second light receiving unit; the first opening is provided in a first light guide path disposed between the light emitting element and a first irradiated region of the irradiated surface, and is disposed such that light output from the light emitting element is directed toward the first irradiated region; The second opening is provided in a second light guide path arranged between the first irradiated area and the first light receiving unit, and is arranged so that when the toner image passes through the first irradiated area, diffusely reflected light from the toner image passes through, and when the surface of the rotating body passes through the first irradiated area, specularly reflected light from the surface, and diffusely reflected light or diffracted light do not pass through. Effect of the Invention

[0006] According to the present invention, it is possible to suppress a decrease in detection accuracy in an optical sensor that may occur due to reflected light from an illuminated surface. [Brief description of the drawings]

[0007] [Figure 1] FIG. [Diagram 2] FIG. 4 is a diagram for explaining a test pattern. [Diagram 3] FIG. [Figure 4] FIG. 4 is a diagram illustrating grooves in an intermediate transfer belt. [Diagram 5] FIG. 4 is a diagram illustrating grooves in an intermediate transfer belt. [Figure 6] A graph explaining BRDF. [Figure 7] 1A and 1B are diagrams illustrating an optical sensor. [Figure 8] FIG. 2 is a diagram illustrating an optical path of an optical sensor. [Figure 9] FIG. 2 is a diagram illustrating an optical path of an optical sensor. [Figure 10] 1A and 1B are diagrams for explaining diffracted light of various orders; [Figure 11] 1A and 1B are diagrams for explaining diffracted light of various orders; [Figure 12] 1A and 1B are diagrams for explaining diffracted light of various orders; [Figure 13] FIG. 2 is a diagram illustrating the diffraction angles of various orders. [Figure 14] 11A to 11C are diagrams illustrating diffracted light of various orders in a comparative example. [Figure 15] 11A to 11C are diagrams illustrating diffracted light of various orders in a comparative example. [Figure 16] 11A to 11C are diagrams illustrating diffracted light of various orders in a comparative example. [Figure 17] 6A and 6B are diagrams for explaining detection results of a test pattern. [Figure 18] FIG. 2 is a diagram for explaining an optical path in a convergent optical system. [Figure 19] FIG. 2 is a diagram for explaining an optical path in a convergent optical system. [Figure 20]FIG. 2 is a diagram for explaining an optical path in a diverging optical system. [Figure 21] FIG. 2 is a diagram for explaining an optical path in a diverging optical system. [Figure 22] FIG. 11 is a diagram showing another example of the installation position of the optical sensor. [Figure 23] FIG. 2 is a diagram illustrating an optical path of an optical sensor. [Figure 24] FIG. 2 is a diagram illustrating an optical path of an optical sensor. [Diagram 25] FIG. 2 is a diagram illustrating an optical path of an optical sensor. [Figure 26] FIG. 2 is a diagram illustrating an optical path of an optical sensor. [Figure 27] 6A and 6B are diagrams for explaining detection results of a test pattern. [Figure 28] Graph illustrating the BRDF of a belt with anisotropic reflectance properties. [Figure 29] FIG. 13 is a diagram for explaining an optical path of an optical sensor according to a fourth embodiment. [Diagram 30] FIG. 13 is a diagram for explaining the optical path of diffracted light according to the fourth embodiment. [Diagram 31] FIG. 13 is a diagram for explaining the diffraction angle of diffracted light according to the fourth embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a plurality of features, not all of these features are essential to the invention, and the plurality of features may be combined in any manner. Furthermore, in the accompanying drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0009] <Example 1> 1. Overall configuration of image forming device As shown in Fig. 1, image forming apparatus 100 is an electrophotographic color laser printer. It is equipped with process cartridges 7Y, 7M, 7C, and 7K that are detachably attached to the main body of image forming apparatus 100. The four process cartridges 7Y, 7M, 7C, and 7K have the same structure, but each form an image using toner of a different color, such as yellow (Y), magenta (M), cyan (C), and black (K). Hereinafter, the symbols YMCK will be omitted except when each color is individually described.

[0010] The process cartridge 7 has a photosensitive drum 1 which is an image carrier, a charging roller 2 which is a charger, and a developing roller 24 which is a developer. The charging roller 2 uniformly charges the surface of the photosensitive drum 1 using a charging voltage. The exposure device 3 forms an electrostatic latent image by irradiating the surface of the photosensitive drum 1 with light according to an image signal. The developing roller 24 develops the electrostatic latent image with toner using a developing voltage to form a toner image.

[0011] The intermediate transfer unit includes an intermediate transfer belt 12a, a driving roller 12b that drives the intermediate transfer belt 12a, and a driven roller 12d that rotates following the intermediate transfer belt 12a. The intermediate transfer belt 12a is an endless belt type intermediate transfer body, but a drum-shaped intermediate transfer body may also be used. The primary transfer roller 26 is disposed inside the intermediate transfer belt 12a so as to face the photosensitive drum 1. The primary transfer roller 26 transfers the toner image formed on the photosensitive drum 1 onto the intermediate transfer belt 12a using a primary transfer voltage. The multi-color toner image formed by multiple transfer of four color toner images onto the intermediate transfer belt 12a is conveyed to the secondary transfer roller 16 as the intermediate transfer belt 12a rotates.

[0012] The paper feed roller 9 feeds the sheet S from a paper feed cassette 11 that stores the sheet S to a conveying path. The conveying roller pair 10 conveys the fed sheet S to a registration roller pair 17. The registration roller pair 17 conveys the sheet S conveyed from the feeding device to a secondary transfer roller 16. The secondary transfer roller 16 transfers the toner image on the intermediate transfer belt 12a to the conveyed sheet S. The fixing device 14 fixes the toner image on the surface of the sheet S. The paper discharge roller pair 20 discharges the sheet S with the fixed toner image.

[0013] The cleaning blade 22a is a cleaning member that cleans the toner remaining on the intermediate transfer belt 12a. The optical sensor 31 is an optical sensor that detects a test image formed on the intermediate transfer belt 12a. The test image may include a pattern for adjusting the formation position of each of the YMCK toner images, and a pattern for adjusting the density (tone) and color of the toner image.

[0014] 2. Calibration of image forming device Calibration performed by forming a test pattern on the intermediate transfer belt 12a includes registration control and density control. Registration control refers to adjusting the image formation position, which reduces color misregistration. Density control refers to controlling the density of the toner image, which improves color reproducibility.

[0015] As shown in FIG. 2, the image forming apparatus 100 performs calibration during a period when the image forming apparatus 100 is not forming an image input by a user. The image forming apparatus 100 forms a test pattern 30 on the intermediate transfer belt 12a, and optically detects the test pattern 30 with an optical sensor 31. In this example, two optical sensors 31 are arranged to face the driving roller 12b of the intermediate transfer belt 12a. The two optical sensors 31 are arranged at different positions in the width direction of the intermediate transfer belt 12a. The direction parallel to this width direction may be defined as the y direction. The rotation axis of the driving roller 12b is also parallel to the y direction. The movement direction of the intermediate transfer belt 12a may be defined as the x direction. The direction perpendicular to both the x direction and the y direction may be defined as the z direction. Three or more optical sensors 31 may be arranged.

[0016] 3. Registration Control 3, the controller 29 is a control circuit that performs overall control of the image forming apparatus 100, and may include, for example, a storage device and a CPU (Central Processing Unit). The controller 29 has a registration control unit 29a that performs registration control, and a density control unit 29b that performs density control of the toner image.

[0017] The registration control unit 29a controls the exposure device 3 so that the scanning speed of the exposure device 3 becomes a predetermined target value and the amount of exposure light becomes a predetermined target value. Furthermore, the registration control unit 29a adjusts the exposure start timing of the exposure device 3 based on the detection result of the test pattern 30 by the optical sensor 31. This adjusts the image formation positions of YMCK and corrects color misregistration. Note that the adjustment of the image formation position includes adjustment of the position of the toner image in the main scanning direction, the position in the sub-scanning direction, and the width (magnification) of the toner image in the main scanning direction.

[0018] The registration control unit 29a controls the image forming apparatus 100 to form i rows of test patterns 30 for detecting color shift for each color on the intermediate transfer belt 12a, where i is an integer equal to or greater than 2. The registration control unit 29a detects the test patterns 30 using i optical sensors 31 to obtain the amount of color shift. The amount of color shift includes the relative amount of color shift in the main scanning direction between each color, the relative amount of color shift in the sub-scanning direction, the magnification in the main scanning direction, and the relative inclination. Based on the detection result, the registration control unit 29a corrects the write timing (exposure start timing) of the image for each color so that the relative amount of color shift for each color is reduced.

[0019] 4. Toner image density control The density of a toner image may vary depending on the temperature and humidity conditions of the environment in which the image forming apparatus 100 is installed and the degree of use of the image forming stations for each color. To correct this variation, the density control unit 29b controls the image forming apparatus 100 to form a test pattern 30 for density detection on the intermediate transfer belt 12a. The density control unit 29b detects the density of the test pattern 30 with an optical sensor 31, and controls the density factor based on the detection result so as to obtain the desired density characteristics.

[0020] Specifically, the density control unit 29b controls the high-voltage power supply 29c to set density factors such as the charging voltage, the developing voltage, and the amount of exposure light to specific values, and starts forming the test pattern 30. Image data for forming the test pattern 30 may be generated by the host computer 27 or by the controller 29. The density control unit 29b stores the adjustment results of the density factors in a memory or the like, and uses the adjustment results when forming an image input by a user on the sheet S.

[0021] 5. Intermediate Transfer Belt Structure As shown in Fig. 4(A), the intermediate transfer belt 12a may have a plurality of grooves 83 formed therein to reduce friction with the cleaning blade 22a. Fig. 4(B) is a cross-sectional view of the intermediate transfer belt 12a cut parallel to the zy plane.

[0022] As shown in Fig. 4(A), the fine grooves 83 are formed substantially parallel to the x direction. As shown in Fig. 4(B), the intermediate transfer belt 12a has a base layer 81 and a surface layer 82 formed on the base layer 81. The base layer 81 is the thickest layer among the multiple layers constituting the intermediate transfer belt 12a. The surface layer 82 constitutes the surface (outer peripheral surface) of the intermediate transfer belt 12a and carries the toner transferred from the photosensitive drum 1.

[0023] The base layer 81 may be, for example, a layer of about 70 μm in thickness, in which carbon black is dispersed and mixed as an electrical resistance adjusting agent in polyethylene naphthalate resin. The polyethylene naphthalate resin is merely one example of the material for the base layer 81, and any thermoplastic resin may be used. Materials such as polyimide, polyester, polycarbonate, polyarylate, acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene sulfide (PPS), polyvinylidene fluoride (PVdF), and mixed resins of these may be used. As the electrical resistance adjusting agent (conductive agent), for example, an ionic conductive agent may be used in addition to an electronic conductive agent.

[0024] The surface layer 82 may be a layer having a thickness of about 3 μm, in which an electrical resistance adjusting agent (e.g., zinc oxide) is dispersed and mixed into an acrylic resin. A resin material (curable resin) may be adopted as the material for the surface layer 82 from the viewpoint of strength such as abrasion resistance and crack resistance. Among the curable resins, for example, an acrylic resin obtained by curing an acrylic copolymer containing unsaturated double bonds may be adopted. As the electrical resistance adjusting agent (conductive agent), for example, an ionic conductive agent may be adopted in addition to an electronic conductive agent.

[0025] In general, the combination of urethane rubber and acrylic resin has a large friction resistance due to sliding. Therefore, the cleaning blade 22a is likely to turn over, and the cleaning blade 22a is likely to wear due to repeated use. In order to reduce friction, the surface of the intermediate transfer belt 12a may be subjected to fine unevenness processing. For example, the average interval d of the multiple grooves 83 in the y direction may be 2 μm or more and 10 μm or less. The grooves 83 may be called groove shapes or groove portions. The grooves 83 are provided in substantially the entire area of ​​the outer circumferential surface of the intermediate transfer belt 12a. In the y direction B, the multiple grooves 83 are formed in substantially the entire area of ​​the contact area where the cleaning blade 22a and the intermediate transfer belt 12a contact each other. The grooves 83 may not be provided in the area of ​​the surface layer 82 of the intermediate transfer belt 12a where the cleaning blade 22a does not contact.

[0026] Generally, techniques for forming fine irregularities include polishing, cutting, and imprinting. Any processing technique that can obtain the desired distance d can be used. From the viewpoint of processing cost and productivity, imprinting may be used, taking advantage of the photocuring properties of the acrylic resin that is the base material of the surface layer 82.

[0027] The width (groove width) w of the groove 83 is the width of the opening in the y direction, which is approximately perpendicular to the longitudinal axis direction of the groove 83. The groove width w is the distance of the section where the thickness of the surface layer 82 is relatively thin. The thickness of the surface layer 82 is the thickest at the outermost surface 84. The groove width w is, for example, 1.2 μm. The groove width w may be less than the average particle size of the toner. More specifically, the groove width w may be less than half the average particle size of the toner. By making the groove width w smaller than the average particle size of the toner, the toner is less likely to enter the groove 83, and the toner is more reliably cleaned by the cleaning blade 22a. In order to suppress the collapse of the convex portion of the mold used to form the groove 83, the groove width w may be, for example, 0.5 μm or more. More specifically, the groove width w may be 0.5 μm or more and 6 μm or less. Furthermore, the groove width w may be 1 μm or more and 2 μm or less.

[0028] The depth (groove depth) l of the groove 83 is defined as the depth from the opening (outermost surface 84) of the groove 83 to the bottom of the groove 83 in the thickness direction of the intermediate transfer belt 12a. The groove depth l is, for example, 0.45 μm at the beginning of use (when new) of the intermediate transfer belt 12a. For example, the groove depth l may be 0.2 μm or more and less than the thickness of the surface layer 82 at the beginning of use of the intermediate transfer belt 12a. If the groove depth l is too small, the groove 83 is likely to disappear or cleaning failures may occur due to scraping of the surface layer 82. If the groove depth l is less than the thickness of the surface layer 82, the groove 83 does not reach the base layer 81 and exists only in the surface layer 82. Here, the thickness of the surface layer 82 may be designed to be 1 μm or more and 5 μm or less from the viewpoint of reducing a decrease in durability due to being too thin and cracking of the surface layer due to being too thick. More typically, the thickness of the surface layer 82 is set to be equal to or greater than the thickness at which the grooves 83 do not reach the base layer 81, and equal to or less than 3 μm.

[0029] The interval d between the grooves 83 is defined as the distance from one end (e.g., left end) of the opening of the j-th groove 83 in the y direction to one end (e.g., left end) of the opening of the j+1-th groove 83 in the y direction. j is an integer of 1 or more. A plurality of grooves 83 are formed at an equal pitch (approximately the same interval d) of 3.7 μm in almost the entire area in the y direction. The interval d may be defined based on the right end of the opening, or may be defined as the interval between the bottoms of two adjacent grooves 83. If the interval d is too small, it may be difficult to form a uniform uneven shape. Also, if the interval d is too large, it may be difficult to suppress wear of the cleaning blade 22a. Therefore, the interval d may be designed to be 2 μm or more and 10 μm or less, or more specifically, 3 μm or more and 4 μm or less.

[0030] In FIG. 4A, the groove 83 is formed substantially parallel to the y direction. Furthermore, the groove 83 is formed continuously and substantially linearly around one circumference in the circumferential direction (rotation direction) of the intermediate transfer belt 12a. However, the extending direction of the groove 83 may be parallel to the direction intersecting with the y direction. As shown in FIG. 5A, the extending direction of the groove 83 may have an angle with respect to the conveying direction of the intermediate transfer belt 12a. This angle θ may be, for example, 45 degrees or less, and more specifically, 10 degrees or less. Typically, θ may be set to approximately zero. The groove 83 having the angle θ may be formed by using a mold having a convex portion formed obliquely with respect to the rotation direction of a cylinder forming the mold. The groove 83 may be formed by holding the mold having a convex portion formed substantially parallel to the rotation direction of the cylinder forming the mold obliquely with respect to the x direction.

[0031] 6. Diffraction Phenomenon Fig. 5(B) shows the diffraction phenomenon caused by a reflection type diffraction grating. In general, the equation showing the diffraction angle from a reflection type diffraction grating is expressed by the following (Equation 1).

[0032] d[sin(θi)+sin(θm)]=mλ (Formula 1) d is the spacing of the diffraction grating. λ is the wavelength of the light ray. θi is the angle of incidence of the light ray with respect to the normal direction of the diffraction grating. θm is the angle of reflection (diffraction angle). m is the diffraction order (m = positive or negative integers of ±0, ±1, ±2, ...). When m = 0 (i.e., in the case of specular reflection), θi = θm = 0. Therefore, for specular reflected light, the spacing d of the grating and the wavelength λ of the light ray do not affect the diffraction angle. For other orders, the reflected lights constructively interact at a diffraction angle θm where the optical path difference of each reflected light is an integer multiple of the wavelength, depending on the spacing d and the wavelength λ of the light ray. Expanding (Equation 1) for the diffraction angle θm gives the following (Equation 2).

[0033] sinθm=mλ / d-sinθi (Formula 2) If the angle of incidence with respect to the normal to the irradiation surface is defined as negative, the following tendency exists. The larger the incident angle θi, the larger the right side of (Equation 2) becomes, and the larger the diffraction angle θm becomes. The larger the light wavelength λ, the larger the right side of (Equation 2) becomes, and the larger the diffraction angle θm becomes. The smaller the grating interval d, the larger the right side of (Equation 2) becomes, and the larger the diffraction angle θm becomes. In the intermediate transfer belt 12a, the average interval d of the grooves 83 formed on the surface corresponds to the grating interval d. Therefore, the light from the light-emitting element of the optical sensor 31 is diffracted by the multiple grooves 83.

[0034] 7. Scattering characteristics of intermediate transfer belt FIG. 6(A) is a graph showing the angular distribution characteristic of scattered light (hereinafter, abbreviated as "BRDF" by taking the initial letters of bidirectional reflectance distribution function). The vertical axis shows the relative reflected light intensity of scattered light. The horizontal axis shows the reflection angle. The solid line shows the BRDF obtained by irradiating the surface of the intermediate transfer belt 12a, on which a plurality of grooves 83 (uneven shape) with a spacing d of 3.7 μm are formed, with light of λ=622 nm at an incident angle of -20°. The BRDF was measured using a small and simple scattering measurement device Mini-Diff V1 by Cybernet Corporation. In FIG. 6(A), an intermediate transfer belt 12a (hereinafter, abbreviated as "coated belt") that is not subjected to fine uneven processing on the surface and is merely coated with acrylic resin is used as a comparative example. The dashed line shows the BRDF of the comparative example.

[0035] As can be seen from Figure 6(A), the BRDF of the coated belt has a broad diffuse reflection component relative to the peak of the specular reflection light. In contrast, the BRDF of the intermediate transfer belt 12a, which has been subjected to fine unevenness, has a diffraction phenomenon in which the amount of zero-order specular reflection light decreases and the amount of reflected light increases at periodic angles. The intensity of the diffracted light decreases as the order m increases.

[0036] The BRDF of the intermediate transfer belt 12a with the uneven surface has diffuse reflection components around each order of diffracted light. Therefore, the diffuse reflection components of the BRDF of the intermediate transfer belt 12a with the uneven surface are significantly stronger than the diffuse reflection components of the BRDF of the coated belt.

[0037] 8. Toner sensor configuration FIG. 7(A) is a schematic perspective view of the optical sensor 31. FIG. 7(B) is an exploded perspective view showing the components of the optical sensor 31. While x, y, and z are directions based on the image forming apparatus 100, x1, y1, and z1 are directions based on the optical sensor 31. The x1 direction is the short side direction of the optical sensor 31. In the first embodiment, the x direction and the x1 direction are not parallel. The y1 direction is the long side direction of the optical sensor 31. In the first embodiment, the y direction and the y1 direction are parallel. The z1 direction is the height direction of the optical sensor 31 (the normal direction of the circuit board 34). In the first embodiment, the z direction and the z1 direction are not parallel.

[0038] Fig. 8 shows a cross-sectional view of the optical path with the x1 direction as the line of sight. That is, a cross-section passing through the rotation axis of the driving roller 12b and the center of the LED 35 is shown. Fig. 9(A) is a cross-sectional view explaining the irradiated area 47 where diffusely reflected light occurs when viewed with the y direction as the line of sight. Fig. 9(B) is a schematic cross-sectional view explaining the irradiated area 50 where specularly reflected light occurs when viewed with the y direction as the line of sight. These cross-sections are cut parallel to the height direction and short side direction of the optical sensor 31, and correspond to cuts normal to the y direction.

[0039] The optical sensor 31 is disposed so as to face the substantially cylindrical surface formed by the intermediate transfer belt 12a being wound around the drive roller 12b. As shown in Fig. 7(A) and Fig. 7(B), the optical sensor 31 has a cover member 32, a housing 33, and a circuit board 34. An LED 35, which is a light-emitting element, a first light-receiving unit 36, and a second light-receiving unit 37 are mounted on the circuit board 34. In addition, a straight line connecting the center of the mounting position of the LED 35, the center of the mounting position of the first light-receiving unit 36, and the center of the mounting position of the second light-receiving unit 37 is substantially parallel to the rotation axis of the drive roller 12b.

[0040] 7B, the LED 35 has a light-emitting chip 35a surrounded by a light-transmitting member 35b. The light-transmitting member 35b is a light-transmitting member (e.g., resin or glass). The light emitted from the light-emitting chip 35a is scattered at the boundary surface of the light-transmitting member 35b, and as a result, the light is emitted from almost the entire surface of the light-transmitting member 35b.

[0041] A part of the light emitted from the LED 35 is reflected by the surface of the intermediate transfer belt 12a to become diffusely reflected light, which is detected by the first light receiving unit 36. A part of the light emitted from the LED 35 is reflected by the surface of the intermediate transfer belt 12a to become specularly reflected light, which is detected by the second light receiving unit 37. That is, the first light receiving unit 36 ​​has a plurality of light receiving elements that receive the diffusely reflected light. The second light receiving unit 37 has a plurality of light receiving elements that receive the specularly reflected light. These multiple light receiving elements are arranged parallel to the short side direction (x1 direction) of the circuit board 34. The number of light receiving elements in each unit is, for example, 16. By configuring the first light receiving unit 36 ​​and the second light receiving unit 37 with multiple light receiving elements in this way, even if there is a deviation within the tolerance range in the positional relationship between the cylindrical surface of the drive roller 12b and the optical sensor 31, the reflected light can be sufficiently detected.

[0042] As shown in FIG. 7B, a first opening 40, a second opening 41, and a third opening 42 are provided on the upper surface of the housing 33. The first opening 40 forms a part of a light guide path through which light from the LED 35 toward the intermediate transfer belt 12a passes. The second opening 41 forms a part of a light guide path through which reflected light from the intermediate transfer belt 12a toward the first light receiving unit 36 ​​and the second light receiving unit 37 passes. The third opening 42 forms a part of a light guide path through which light from the LED 35 toward the intermediate transfer belt 12a passes. The housing 33 may be provided with a light shielding wall 38. The light shielding wall 38 prevents the light from the LED 35 from directly entering the first light receiving unit 36 ​​and the second light receiving unit 37.

[0043] A first lens unit 43, a second lens unit 44, and a third lens unit 45 may be provided on the back side of the cover member 32 (the side where the housing 33 is arranged). The first lens unit 43 functions so that the light passing through the first opening 40 forms a desired spot on the irradiated surface. The second lens unit 44 functions so that the diffusely reflected light from the intermediate transfer belt 12a forms an image on the first light receiving unit 36, and the regular reflected light from the intermediate transfer belt 12a forms an image on the second light receiving unit 37. The third lens unit 45 functions so that the light passing through the third opening 42 forms a desired spot on the irradiated surface. The first lens unit 43, the second lens unit 44, and the third lens unit 45 may be provided individually or integrally.

[0044] 9. Optical path for detecting diffusely reflected light In Fig. 8, the y direction and the y1 direction are parallel to the width direction of the intermediate transfer belt 12a. Therefore, the extension direction of the groove 83 is parallel to the direction from the back of the paper to the front. In Fig. 9(A), the transport direction of the intermediate transfer belt 12a, which is the transport direction of the portion not in contact with the drive roller 12b, is parallel to the x direction. The extension direction of the groove 83 is also parallel to the x direction.

[0045] As shown in Figures 8 and 9(A), the light output from the LED 35 passes through the first opening 40 and enters the first lens portion 43. The light that enters the first lens portion 43 passes through the flat portion 32a, which is a part of the upper surface of the cover member 32, and enters the surface of the intermediate transfer belt 12a. This incident light is referred to as first irradiation light 46. As shown in Figures 8 and 9(A), the irradiated region 47 is the irradiated region of the first irradiation light 46 for detecting diffusely reflected light.

[0046] The housing 33 is made of black resin. This reduces stray light. The cover member 32 is made of transparent resin (translucent resin). The refractive index of the cover member 32 is different from the refractive index of the space in front of and behind the cover member 32. Therefore, the first irradiation light 46 is refracted by the surface of the first lens portion 43 and the flat portion 32a and is irradiated to the irradiated area 47. The material of the cover member 32 is set to polystyrene with a refractive index of 1.59, for example. The lens radius of the first lens portion 43 is designed so that the light emitting chip 35a is located at the focal point of the first lens portion 43. Therefore, the first irradiation light 46 incident on the first lens portion 43 becomes approximately parallel light and is irradiated to the intermediate transfer belt 12a.

[0047] As shown in FIG. 8, the first opening 40 and the first lens portion 43 are disposed at a position shifted to the right (in the +y1 direction) of a perpendicular line from the LED 35 to the rotation axis of the drive roller 12b. The perpendicular line is parallel to the normal line of the circuit board 34. The first irradiation light 46 is also a light ray that travels in a direction inclined to the right of this perpendicular line. As shown in FIG. 8, an irradiation angle θD1 is defined here. The irradiation angle θD1 of the first irradiation light 46 is, for example, -25°. Here, the irradiation angle is defined as - and the reflection angle as +, but + and - are omitted when the magnitude of the angle is of interest.

[0048] As shown in Fig. 9(A), the first opening 40 and the first lens portion 43 are disposed at a position shifted to the right of the perpendicular line of the LED 35. In Fig. 9(A), the right is the direction parallel to the short-side direction of the circuit board 34 (+x1 direction). As a result, also in Fig. 9(A), the first irradiation light 46 becomes a light ray inclined to the right. As shown in Fig. 9(A), an irradiation angle θD2 is defined. The irradiation angle θD2 of the first irradiation light 46 is, for example, -11.5°.

[0049] 8, a first light receiving area 48, which is an area in which the first light receiving unit 36 ​​can receive reflected light, is an area from point 48a to point 48b. Point 48a is a point obtained by extending a line connecting the left corner 36a of the first light receiving unit 36 ​​to the upper right corner 41b of the second opening 41 along the light guide path. Point 48b is a point obtained by extending a line connecting the right corner 36b of the first light receiving unit 36 ​​to the lower left corner 41c of the second opening 41 along the light guide path.

[0050] In FIG. 9(A), the first light receiving area 48' that the first light receiving unit 36 ​​can receive light is in the range from point 48c to point 48d. Point 48c is a point obtained by extending a line connecting the left corner 36c of the first light receiving unit 36 ​​to the upper right corner 41f of the second opening 41 along the light guide path. Point 48d is a point obtained by extending a line connecting the right corner 36d of the first light receiving unit 36 ​​to the upper left corner 41e of the second opening 41 along the light guide path. Since the second lens portion 44 has a cylindrical shape, the surface of this cylinder is shown as an arc in FIG. 9(A). The dimensions of the second opening 41 shown in FIG. 8 are different from the dimensions of the second opening 41 shown in FIG. 9(A). Therefore, the dimensions of the first light receiving area 48 shown in FIG. 8 are different from the dimensions of the first light receiving area 48' shown in FIG. 9(A).

[0051] 8 and other figures, the first irradiated area 47 is smaller than the first light-receiving area 48. Therefore, the range that the first light-receiving unit 36 ​​can detect is actually the first irradiated area 47. In other words, the first light-receiving unit 36 ​​for detecting diffusely reflected light detects the diffusely reflected light from the first irradiated area 47.

[0052] 10. Optical path for detecting specularly reflected light As shown in FIG. 8 and FIG. 9(B), the housing 33 is provided with a third opening 42 for irradiating the intermediate transfer belt 12a with light. The cover member 32 is provided with a third lens portion 45 for irradiating the intermediate transfer belt 12a with light, separate from the first lens portion 43. The light output from the LED 35 passes through the third opening 42 and enters the third lens portion 45. The light that enters the third lens portion 45 passes through a flat portion 32a provided on the upper surface of the cover member 32 and enters the surface of the intermediate transfer belt 12a. This incident light is referred to as a second irradiation light 49. The second irradiated region 50 is an area where the second irradiation light 49 is irradiated to detect the regular reflection light. The lens radius of the third lens portion 45 is designed so that the light emitting chip 35a is located at the focus of the third lens portion 45. Therefore, the second irradiation light 49 that enters the third lens portion 45 becomes substantially parallel light and is irradiated onto the intermediate transfer belt 12a.

[0053] As shown in Fig. 8, the third opening 42 and the third lens portion 45 are disposed at a position shifted to the left (-y direction) with respect to the perpendicular line to the LED 35. In Fig. 8, the second irradiation light 49 is a light beam inclined to the left with respect to the perpendicular line. Here, the irradiation angle of the second irradiation light 49 is defined as θS1. The irradiation angle θS1 of the second irradiation light 49 is, for example, -19.1°.

[0054] 9B, the third opening 42 and the third lens portion 45 are disposed substantially directly above the LED 35. Therefore, the second irradiation light 49 is a light ray that travels substantially in the normal direction of the irradiated surface (irradiation angle θS2≒0°). In other words, the second irradiated area 50 is a different area from the first irradiated area 47.

[0055] 8, the second light receiving area 51, which is the range in which the second light receiving unit 37 can receive light, is the range from point 51a to point 51b. Point 51a is an extension of a line connecting the left corner 37a of the second light receiving unit 37 to the lower right corner 41d of the second opening 41. Point 51b is an extension of a line connecting the right corner 37b of the second light receiving unit 37 to the upper left corner 41a of the second opening 41.

[0056] 9(B), a second light receiving area 51' that can receive light by the second light receiving unit 37 in the belt conveyance direction A ranges from point 51c to point 51d. Point 51c is a point obtained by extending a line connecting the left corner 37c of the second light receiving unit 37 to the upper right corner 41f of the second opening 41 along the light guide path. Point 51d is a point obtained by extending a line connecting the right corner 37d of the second light receiving unit 37 to the upper left corner 41e of the second opening 41 along the light guide path.

[0057] 8 and 9(B), the dimensions of the second irradiated region 50 are smaller than the dimensions of the second light receiving regions 51, 51'. As a result, the substantial range in which the second light receiving unit 37 can detect light is the second irradiated region 50. In other words, the second light receiving unit 37 detects the specularly reflected light from the second irradiated region 50.

[0058] 11. Diffraction light caused by light irradiated by the toner sensor Fig. 10 shows the optical path of the diffracted light of the first irradiation light 46 as viewed from the downstream side in the transport direction of the intermediate transfer belt 12a. Fig. 11 shows the optical path of the diffracted light of the second irradiation light 49 as viewed from the downstream side in the transport direction of the intermediate transfer belt 12a. Fig. 12(A) shows the diffracted light of the first irradiation light 46 as viewed from the width direction of the intermediate transfer belt 12a. Fig. 12(B) shows the diffracted light caused by the second irradiation light 49 as viewed from the width direction of the intermediate transfer belt 12a. The interval d of the grooves 83 of the intermediate transfer belt 12a is 3.7 μm, and the wavelength λ of the LED 35 is 850 nm.

[0059] Regarding the diffracted light of the first irradiation light 46 detected by the first light receiving unit 36, the m-th order diffraction angle is given by Equation 2. By substituting the irradiation angle θi of the diffracted light generated by the first irradiation light 46 shown in Fig. 10 with θD1 and performing calculations, the table shown in Fig. 13(A) is obtained (θD1 is -25°). As shown in Fig. 10 and Fig. 13(A), the diffracted light directed toward a position close to the first light receiving unit 36 ​​is the -6th order, -5th order, and -4th order diffracted light.

[0060] 12(A), the diffraction angle of the diffracted light of the first irradiation light 46 can also be calculated by replacing the irradiation angle θi with θD2 in Equation 2 (θD2=-11.5°). As a result, the diffraction angle of each diffracted light is near +11.5°. Therefore, the diffracted light is unlikely to enter the second opening 41.

[0061] 11 and 12(B), the second irradiation light 49 for the second light receiving unit 37 is inclined with respect to the perpendicular line (irradiation angle θS) in Fig. 11, but is parallel to the perpendicular line in Fig. 12(B). When the diffraction angle is calculated from Equation 2 when m=-1, 0, +1 (θS1=-19.1°), the diffraction angle shown in the table of Fig. 11 and Fig. 13(B) is obtained.

[0062] 12B, the diffracted light of the second irradiation beam 49 can also be calculated by replacing the irradiation angle θi with θS2 (θS2=0°) in Equation 2. As a result, the diffraction angles of the diffracted light are all near 0°.

[0063] 12.Detection performance of optical sensors In order to more clearly explain the effect of this embodiment, the performance of the optical sensor 31 of this embodiment is compared with that of the optical sensor of the comparative example. Figures 14, 15, 16(A) and 16(B) show the optical sensor 31' of the comparative example. Note that Figures 14, 15, 16(A) and 16(B) showing the comparative example correspond to Figures 10, 11, 12(A) and 12(B) showing the embodiment, respectively. The same reference numerals are given to elements common or similar between the embodiment and the comparative example, and their description will be omitted. In the embodiment and the comparative example, the shape of the groove 83 of the intermediate transfer belt 12a and the light wavelength of the LED 35 are the same.

[0064] The difference between the optical sensor 31' of the comparative example and the optical sensor 31 of the embodiment is shown in FIG. 16(A). In the comparative example, the first irradiation light 46 is irradiated to the intermediate transfer belt 12a in a direction substantially normal to the circuit board 34 (toward the rotation axis of the drive roller 12b) (irradiation angle θD2≒0°). That is, in the comparative example, the first opening 40 and the first lens portion 43 are arranged so that the irradiation angle θD2≒0° is satisfied. As explained in FIG. 6(A), diffuse reflection components exist around the diffracted light. Therefore, even if the first light receiving unit 36 ​​is arranged away from the diffracted light, the diffuse reflection components occurring around the diffracted light will enter the first light receiving unit 36. As a result, the performance of detecting toner in the comparative example is significantly reduced.

[0065] More specifically, as shown in Fig. 16(A), the irradiation direction and the normal direction of the irradiated surface are parallel, so that the -5th order diffracted light is incident on the vicinity of the first light receiving unit 36, as shown in Fig. 14. Therefore, diffuse reflection components occurring around the diffracted light are incident on the first light receiving unit 36, and the toner detection performance is significantly degraded.

[0066] 12A, the irradiation angle θD2 of the first irradiation light 46 of the optical sensor 31 is −11.5°. Therefore, the diffuse reflection components generated around the diffracted light are less likely to be incident on the first light receiving unit 36. Therefore, the toner detection performance of the optical sensor 31 of the embodiment is excellent.

[0067] Fig. 17(A) shows the output value of the first light receiving unit 36 ​​of the optical sensor 31 of the embodiment. Fig. 17(B) shows the output value of the first light receiving unit 36 ​​of the optical sensor 31' of the comparative example. Here, it is shown that the test patterns 30 having optical densities of 20%, 40%, 60%, 80% and 100% are detected by the optical sensors 31, 31'. As described above, the first light receiving unit 36 ​​is a light receiving unit that detects diffusely reflected light from toner.

[0068] The optical sensor 31 of the embodiment employs a configuration that avoids regular reflection light and diffracted light from the intermediate transfer belt 12a. As shown in Figures 17(A) and 17(B), the output value 60 of the optical sensor 31 obtained when detecting the surface of the intermediate transfer belt 12a is lower than the output value 60 of the optical sensor 31'. Therefore, the difference 61 between the output value when detecting the test pattern 30 with a density of 100% and the output value 60 when detecting the intermediate transfer belt 12a becomes large. Therefore, the optical sensor 31 can accurately detect the diffuse reflection light from the toner.

[0069] On the other hand, the optical sensor 31' of the comparative example detects a large amount of diffuse reflection components occurring around the diffracted light from the intermediate transfer belt 12a. As shown in FIG. 17B, the output value 60 when the intermediate transfer belt 12a is detected becomes relatively high. Therefore, the difference 61 becomes relatively small. Therefore, the optical sensor 31' of the comparative example cannot detect the diffuse reflection light from the toner with a high degree of accuracy compared to the configuration of the first embodiment.

[0070] 13. Effects of Example 1 The irradiation direction of the first irradiation light 46 is inclined from the normal to the irradiated surface in both the transport direction and width direction of the intermediate transfer belt 12a. As a result, the detection performance of the first light receiving unit 36 ​​is improved. Since the specularly reflected light caused by the first irradiation light 46 is directed away from the first light receiving unit 36 ​​in both the transport direction and width direction of the intermediate transfer belt 12a, the detection performance of the first light receiving unit 36 ​​is improved.

[0071] The detection performance of the first light receiving unit 36 ​​in the first embodiment is improved mainly for the following two reasons. The first reason is that the first irradiation light 46 is diffracted in the width direction of the intermediate transfer belt 12a by the groove 83. In the conveying direction, the irradiation direction of the first irradiation light 46 is inclined with respect to the normal line of the irradiated surface, so the diffracted light moves away from the second opening 41 and the second lens unit 44. The second reason is that the first irradiation light 46 moves toward a position shifted from the rotation axis of the cylindrical driving roller 12b. This causes the tangent plane of the irradiated area to be inclined. As a result, the regular reflection light and the diffracted light of the first irradiation light 46 move toward a position away from the second opening 41 and the second lens unit 44.

[0072] In the first embodiment, the first irradiation light 46 is described as a parallel light for convenience, but it is not essential that the first irradiation light 46 is a parallel light. Figs. 18 and 19 show a case where the first irradiation light 46 is a convergent light. Figs. 20 and 21 show a case where the first irradiation light 46 is a divergent light. In either case, by employing the toner sensor (optical sensor 31) of the first embodiment, the toner detection accuracy is improved. In the first embodiment, the second irradiation light 49 is also described as a parallel light, but the second irradiation light 49 may be a convergent light or a divergent light.

[0073] In the first embodiment, a first lens unit 43, a second lens unit 44, and a third lens unit 45 are provided between the LED 35 and the irradiated surface. However, since it is sufficient that the first irradiation light 46 is tilted in both the transport direction and the width direction of the intermediate transfer belt 12a, the lens units are not essential. For example, the same effect can be obtained if the first opening 40 provided in the housing 33 is disposed at a position shifted from the position directly above the LED 35 in both the transport direction and the width direction. In other words, it is possible to tilt the first irradiation light 46 in both the transport direction and the width direction even without the lens units.

[0074] In the first embodiment, the second opening 41 used by the first light receiving unit 36 ​​to detect diffusely reflected light from the intermediate transfer belt 12a also serves as an opening for the second light receiving unit 37 to detect specularly reflected light from the intermediate transfer belt 12a. However, more strictly speaking, the through hole including the second opening 41 may have a step. That is, the opening for the first light receiving unit 36 ​​to detect diffusely reflected light may be composed of points 41b, 41c, 41e, and 41f. The opening for the second light receiving unit 37 to detect specularly reflected light may be composed of points 41a, 41d, 41e, and 41f. The opening for detecting diffusely reflected light and the opening for detecting specular reflected light may be combined, or the opening for detecting diffusely reflected light and the opening for detecting specular reflected light may be provided independently in the housing 33.

[0075] In the first embodiment, the third lens unit 45 has a lens for detecting diffusely reflected light from the intermediate transfer belt 12a and a lens for detecting regularly reflected light. However, these may be realized by a single dual-purpose lens.

[0076] In the first embodiment, the first light receiving unit 36 ​​and the second light receiving unit 37 are described as each having a plurality of light receiving elements. However, when the first light receiving unit 36 ​​and the second light receiving unit 37 can each detect light sufficiently, each may be realized by a single light receiving element.

[0077] <Example 2> In the first embodiment, the outer peripheral surface (side surface) of the cylindrical shape formed by the intermediate transfer belt 12a being wound around the driving roller 12b is the irradiated surface. This improves the accuracy of toner detection because the irradiated surface is less likely to vibrate. On the other hand, as shown in FIG. 22, a flat portion is formed on the intermediate transfer belt 12a between the driving roller 12b and the driven roller 12d. The toner sensor (optical sensor 31) may be disposed so as to utilize this flat portion as the irradiated surface.

[0078] FIG. 23 is a schematic cross-sectional view of the optical sensor 31 as viewed from the downstream side in the transport direction of the intermediate transfer belt 12a. FIG. 24(A) shows the optical path of diffusely reflected light of the optical sensor 31 as viewed from the width direction of the intermediate transfer belt 12a. FIG. 24(B) shows the optical path of specularly reflected light of the optical sensor 31 as viewed from the width direction of the intermediate transfer belt 12a. The only difference is that the irradiated surface is changed from a cylindrical side surface to a flat surface, and the rest is as already described. Here, too, the interval d between the grooves 83 of the intermediate transfer belt 12a is assumed to be 3.7 μm. The light wavelength λ of the LED 35 is also assumed to be 850 nm. The first irradiation light 46, the second irradiation light 49, the first light receiving area 48, and the second light receiving area 51 are also the same as those in the first embodiment. The x direction is parallel to the transport direction of the flat portion of the intermediate transfer belt 12a and parallel to the short side direction (x1 direction) of the optical sensor 31. The y direction is parallel to the width direction of the intermediate transfer belt 12a, and is parallel to the longitudinal direction (y1 direction) of the optical sensor 31. The z direction is parallel to the height direction (z1 direction) of the optical sensor 31. In other words, the circuit board 34 is disposed substantially horizontally.

[0079] As shown in FIG. 24(A), the first irradiation light 46 is irradiated onto the flat surface of the intermediate transfer belt 12a so as to be inclined with respect to the normal line of the flat surface. Specifically, in the second embodiment, the emission angle of the first irradiation light 46 with respect to the normal line of the LED 35 is the same as that in the first embodiment. However, since the installation angle of the optical sensor 31 is changed, the irradiation angle θD2 is 6.2°. Although the irradiation angle θD2 is small, the regular reflection light and the diffracted light generated in the irradiated area 47 are unlikely to enter the second opening 41. This is because the emission angle of the first irradiation light 46 in the optical sensor 31 and the size and arrangement of the second opening 41 are designed as described in the first embodiment. Therefore, in the second embodiment, the detection performance of the first light receiving unit 36 ​​is also improved.

[0080] The condition is that the regular reflection light and the diffracted light caused by the first irradiation light 46 travel in a direction away from the first light receiving unit 36 ​​in both the conveying direction and the width direction. The light guide path from the LED 35 and the light guide path to the first light receiving unit 36 ​​are designed in this manner. That is, the arrangement of the first opening 40 and the second opening 41 with respect to the LED 35 satisfies this condition. When the first lens unit 43 and the second lens unit 44 are employed, the first lens unit 43 and the second lens unit 44 are arranged so as to satisfy these conditions. Thus, the detection performance of the first light receiving unit 36 ​​is improved.

[0081] <Example 3> The third embodiment relates to an example in which the diffuse reflection component of the reflection characteristics of the intermediate transfer belt 12a is large. More specifically, in the third embodiment, the intermediate transfer belt 12a does not have the grooves 83 on the surface thereof, but has a large diffuse reflection component.

[0082] 1. Scattering characteristics of intermediate transfer belt FIG. 6(B) shows an example of the angular distribution characteristic (BRDF) of scattered light of the intermediate transfer belt 12a of Example 3. This measurement was performed using a small, simple scattering measurement device Mini-Diff V1 from Cybernet Corporation. The wavelength λ of the light is 622 nm. The angle of incidence with respect to the surface of the intermediate transfer belt 12a is -20°. The solid line shows the BRDF of Example 3. The dashed line shows the BRDF of the comparative example (an intermediate transfer belt with little diffuse reflection component and strong regular reflection).

[0083] 6B, in the BRDF of the intermediate transfer belt 12a in Example 3, the diffuse reflection component spreads around the peak of the specular reflection light. In the BRDF of the comparative example, the peak of the specular reflection light is high, and the diffuse reflection component occurring around it is very small.

[0084] 2. Toner sensor configuration Fig. 25 is a schematic cross-sectional view showing the optical path of the optical sensor 31 in Example 3 as viewed from the downstream side in the conveying direction. Fig. 26(A) is a schematic cross-sectional view showing the path of diffusely reflected light of the optical sensor 31 as viewed from the width direction. Fig. 26(B) is a schematic cross-sectional view showing the path of specularly reflected light of the optical sensor 31 as viewed from the width direction.

[0085] The only difference between the third embodiment and the first embodiment is the BRDF of the intermediate transfer belt 12a, and the structure and arrangement of the optical sensor 31 are the same. By adopting the optical sensor 31 in this way, the first light receiving unit 36 ​​can detect the toner with high accuracy even in cases where the diffuse reflection component of the irradiated light is strong.

[0086] 3. Comparative Example The optical sensor 31' of the comparative example described in the embodiment 1 is also adopted in the embodiment 3, and the performance of the embodiment 3 is compared with the performance of the comparative example. The structure of the optical sensor 31' and the installation angle with respect to the intermediate transfer belt 12a are as already described.

[0087] 6B, in the intermediate transfer belt 12a of the third embodiment, strong diffuse reflection components exist around the specular reflection light. It is required to prevent this diffuse reflection component from entering the first light receiving unit 36. In the third embodiment, the first irradiation light 46 is inclined in the width direction and also in the transport direction. Therefore, the specular reflection light generated in the irradiated region 47 and the strong diffuse reflection component generated in the vicinity thereof are less likely to enter the first light receiving unit 36.

[0088] Fig. 27(A) shows the detection result of the test pattern 30 for Example 3. Fig. 27(B) shows the detection result of the test pattern 30 for the comparative example. Here too, five test patterns 30 with densities differing by 20% were detected, along with the background (surface) of the intermediate transfer belt 12a.

[0089] The first light receiving unit 36 ​​is a light receiving element for detecting diffuse reflection from the toner. In the optical sensor 31, the irradiation direction of the first irradiation light 46 is tilted with respect to the normal line of the irradiated area 47 in order to avoid diffuse reflection of light occurring on the surface of the intermediate transfer belt 12a. As a result, the output value 60 when detecting the surface of the intermediate transfer belt 12a is low. In addition, since the difference 61 described above becomes large, the diffuse reflection of light from the toner can be sufficiently detected.

[0090] 27B, in the optical sensor 31' of the comparative example, the diffuse reflection component generated by the intermediate transfer belt 12a is large, so the output value 60 increases. As a result, the difference 61 becomes small, and it becomes difficult to adequately detect the diffuse reflection light from the toner.

[0091] 4. Effects of Example 3 The effects of the third embodiment are basically the same as those of the first embodiment. By tilting the first irradiation light 46 from the normal line of the irradiated surface in both the conveying direction and the width direction, the detection performance of the first light receiving unit 36 ​​is improved. Furthermore, the regular reflection light generated by the first irradiation light 46 travels in a direction away from the first light receiving unit 36 ​​in both the conveying direction and the width direction. Therefore, the detection performance of the first light receiving unit 36 ​​is improved.

[0092] In the third embodiment, an intermediate transfer belt 12a having a large diffuse reflection component is used. However, depending on the manufacturing method and material of the intermediate transfer belt 12a, the BRDF may be different in the conveying direction and the width direction (anisotropy). Even in such a case, the optical sensor 31 functions effectively. FIG. 28 shows an example of the angular distribution characteristic (BRDF) of the scattered light of the intermediate transfer belt 12a having anisotropy. In FIG. 28, the solid line shows the BRDF in the width direction, and the dashed line shows the BRDF in the conveying direction. As can be seen from FIG. 28, the diffuse reflection component spreads out relative to the peak of the regular reflection light in the width direction, but the diffuse reflection component is small in the conveying direction. Even in the case where the intermediate transfer belt 12a having anisotropy is used in this way, the optical sensor 31 can accurately detect the diffuse reflection light from the toner.

[0093] In the third embodiment, the optical sensor 31 is described as detecting the side surface of the cylindrical shape. However, the arrangement of the optical sensor 31 in the second embodiment may be applied to the intermediate transfer belt 12a in the third embodiment. That is, the optical sensor 31 may be arranged with respect to the intermediate transfer belt 12a so as to detect the flat portion.

[0094] <Example 4> 1. Toner sensor configuration The optical sensor 31 according to the fourth embodiment will be described in detail with reference to Fig. 29(A) to Fig. 31. Fig. 29(A) shows a cross-sectional view of an optical path when the line of sight is in the x1 direction. Fig. 29(B) is a cross-sectional view for explaining a first irradiated region 47 when the line of sight is in the y direction.

[0095] In the fourth embodiment, the optical sensor 31 is also disposed to face the side of the substantially cylindrical shape formed by the intermediate transfer belt 12a being wound around the drive roller. In Figs. 29(A) to 30(B), the y direction and the y1 direction are also parallel to the width direction of the intermediate transfer belt 12a. Therefore, the direction in which the multiple grooves 83 are aligned is the y1 direction. In Figs. 29(A) and 30(A), the extension direction of the multiple grooves 83 is the direction from the back of the paper to the front.

[0096] In the fourth embodiment, the LED 35, the first light receiving unit 36, and the second light receiving unit 37 are also arranged side by side in the y1 direction. The distance between the first light receiving unit 36 ​​and the LED 35 is longer than the distance between the second light receiving unit 37 and the LED 35. Therefore, in FIG. 29(A), the first irradiated region 47 is arranged on the right side of the second irradiated region 50. Note that the second irradiated region 50 for detecting the specularly reflected light has already been described in the first to third embodiments. Therefore, in the fourth embodiment, a detailed description of the second irradiated region 50 is omitted.

[0097] 2. Optical path for detecting diffusely reflected light As shown in FIG. 29(A) and FIG. 29(B), the first irradiation light 46 detected by the first light receiving unit 36 ​​is output from the LED 35 and passes through the first opening 40 and the first lens unit 43. The first opening 40 and the first lens unit 43 are disposed at a position shifted to the right (+y1 direction) with respect to the normal line from the LED 35 toward the intermediate transfer belt 12a. The first irradiation light 46 is also a light ray that advances in a direction inclined to the right with respect to the normal line. Here, the normal line is the normal line of the mounting surface of the circuit board 34, and is parallel to the z1 direction. In this way, since the first irradiation light 46 is inclined to the right with respect to the normal line, the specular reflection light (m=0th order light) of the first irradiation light 46 also advances in a direction away from the second opening 41 and the first light receiving unit 36. Here, an irradiation angle θD3 is defined. The irradiation angle θD3 is, for example, −28°.

[0098] 29(B), when the line of sight is in the y1 direction, the first opening 40 and the first lens portion 43 are disposed in the normal direction of the LED 35. The irradiation angle θD4 is 0°.

[0099] In the fourth embodiment as well, the first irradiated area 47 is smaller than the first light receiving areas 48, 48'. Therefore, the first light receiving unit 36 ​​actually detects diffusely reflected light from the first irradiated area 47. In the fourth embodiment as well, the refractive index and radius of the first lens portion 43 are set so that the focal length of the first lens portion 43 is equal to the distance from the first lens portion 43 to the light emitting point of the LED 35. Therefore, the first irradiation light 46 emitted from the first lens portion 43 is irradiated to the first irradiated area 47 as parallel light.

[0100] 3. Diffraction of the first irradiation light Figures 30(A) and 30(B) are cross-sectional views showing the optical path of the diffracted light of the first irradiation beam 46. In particular, Figure 30(A) shows a cross-sectional view of the optical path when the line of sight is in the x1 direction. Figure 30(B) shows a cross-sectional view of the optical path when the line of sight is in the y direction. Figure 31 also shows the reflection angle (which may be called the diffraction angle or the emission angle) of the diffracted light of the first irradiation beam 46.

[0101] As shown in FIG. 30(A) and FIG. 30(B), the diffracted light does not enter the second opening 41 and the first light receiving unit 36. More specifically, the second opening 41 and the first light receiving unit 36 ​​are disposed between the incident position of the diffracted light of the -5th order and the incident position of the diffracted light of the -6th order so that the diffracted light of the -5th order to the -6th order does not enter the second opening 41 and the first light receiving unit 36. Furthermore, the irradiation angle θD3 of the first irradiation light 46 is set to a relatively large angle (-28°). Therefore, the second opening 41 and the first light receiving unit 36 ​​are disposed away from the diffracted light of the -1st order and the diffracted light of the +1st order, which have a large amount of light. In this way, the diffracted light of low orders does not enter the second opening 41 and the first light receiving unit 36. As described with reference to FIG. 6 related to the first embodiment, the amount of diffracted light on the low order side, such as the -1st order and the 1st order, is relatively large. Furthermore, when the amount of m-th order diffracted light is compared with the amount of (m+1)-th order diffracted light, the amount of low-order (m-th order) diffracted light is greater (when m is a positive integer). Therefore, the second opening 41 and the first light receiving unit 36 ​​are disposed at a position that avoids ±1-th order diffracted light and where m-th to (m+1)-th order diffracted light are not incident. As a result, significant diffracted light is not incident on the first light receiving unit 36.

[0102] 4. Technical ideas derived from Example 4 In the fourth embodiment, the LED 35, the first light receiving unit 36, and the second light receiving unit 37 are arranged in line along the y1 direction (width direction of the groove 83) in which the multiple grooves 83 are arranged. The first irradiation light 46 is irradiated at an angle from the normal direction of the irradiated surface to the y1 direction. The inclination (irradiation angle) of the first irradiation light 46 is set so that the traveling direction of the first irradiation light 46 moves away from the second opening 41 and the first light receiving unit 36. Furthermore, the first light receiving unit 36 ​​is arranged farther from the LED 35 than the second light receiving unit 37. This makes it possible for the first light receiving unit 36 ​​to avoid strong reflected light (diffracted light) of low orders such as -1st order, 0th order, and +1st order among the reflected light from the irradiated surface.

[0103] Furthermore, the irradiation angle of the first irradiation light 46 is set within a range where the m-th order diffracted light and the (m+1)-th order diffracted light are not incident on the second opening 41 and the first light receiving unit 36. This makes it possible for the first light receiving unit 36 ​​to reliably avoid the diffracted light from the irradiated surface.

[0104] In the fourth embodiment, the first light receiving unit 36 ​​is disposed between the −5th order diffracted light and the −6th order diffracted light. In particular, the first light receiving unit 36 ​​may be disposed approximately in the center between the −5th order diffracted light and the −6th order diffracted light. More specifically, as shown in FIG. 30(A), the light receiving angle θDD of the first light receiving unit 36 ​​may be set to 52°. In the fourth embodiment, if θDD is between 46° and 58°, the first light receiving unit 36 ​​can reliably avoid the −5th order diffracted light and the −6th order diffracted light. Therefore, the approximately central portion refers to a range (46° to 58°) in which the light receiving angle θDD is 52°±6°.

[0105] In the fourth embodiment, the first irradiation light 46 is parallel light. The parallel light is realized by arranging the first lens unit 43 and the LED 35 so that the focal length of the first lens unit 43 is equal to the distance from the first lens unit 43 to the LED 35. Furthermore, the first irradiated area 47 is set to be smaller than the first light receiving area 48. As a result, the reflected light also becomes approximately parallel light, and the irradiation range (beam diameter) of the reflected light becomes smaller. Therefore, it is possible to ensure a wide area that is not irradiated with diffracted light.

[0106] In the fourth embodiment, it is assumed that the first irradiation light 46 is parallel light, but this is only an example. It is not essential that the first irradiation light 46 is parallel light. The installation position of the first light receiving unit 36 ​​has variation (tolerance) associated with mass production of the optical sensor 31. The position of the first light receiving unit 36 ​​is designed so that diffracted light does not enter the first light receiving unit 36 ​​even if the installation position of the first light receiving unit 36 ​​varies within the tolerance. If the radius of the first lens portion 43 is set larger, the first irradiation light 46 becomes divergent light. Conversely, if the radius of the first lens portion 43 is set smaller, the first irradiation light 46 becomes convergent light. For example, the arrangement of the fourth embodiment can sufficiently secure a range in which diffracted light is not irradiated even if the first irradiation light 46 becomes a 5° convergent light or a 5° divergent light with respect to a parallel light.

[0107] In Example 4, the intermediate transfer belt 12a is wound around a roller to form a cylindrical surface on a part of the surface of the intermediate transfer belt 12a. In Example 4, the irradiated surface is a cylindrical surface. However, as in Example 2, the above-mentioned effect is achieved even if the irradiated surface is a flat surface.

[0108] As described above, the configuration of the fourth embodiment makes it difficult for diffracted light to be incident on the first light receiving unit 36. As a result, in the optical sensor 31 such as a toner sensor, a decrease in detection accuracy that may occur due to reflected light from the irradiated surface is suppressed.

[0109] <Technical ideas derived from examples> <Point 1> The LED 35 is an example of a light-emitting element that irradiates light onto an irradiated surface that is set on a part of the surface of the rotating body. The first light-receiving unit 36 ​​is an example of a first light-receiving unit that receives diffusely reflected light from a toner image formed on the surface of the rotating body. The second light-receiving unit 37 is an example of a second light-receiving unit that receives specularly reflected light from the surface of the rotating body. The circuit board 34 is an example of a circuit board on which the light-emitting element, the first light-receiving unit, and the second light-receiving unit are mounted. The housing 33 is an example of a housing that has a first opening and a second opening and is provided to surround the light-emitting element, the first light-receiving unit, and the second light-receiving unit. As illustrated in FIG. 8 and the like, the first opening 40 is provided in a first light guide path that is arranged between the light-emitting element and a first irradiated region of the irradiated surface. Furthermore, the first opening 40 is arranged so that the light (first irradiation light 46) output from the light-emitting element is directed toward the first irradiated region 47. As illustrated in FIG. 8 and the like, the second opening 41 is provided in a second light guide path that is arranged between the first irradiated region 47 and the first light-receiving unit 36. Furthermore, the second opening 41 is disposed at a position that satisfies the following condition: That is, when a toner image passes through the first irradiated region 47, diffusely reflected light from the toner image passes through the second opening 41. Furthermore, when the surface of a rotating body passes through the first irradiated region 47, specularly reflected light from the surface, and diffusely reflected light or diffracted light do not pass through the second opening 41. This makes it possible to suppress a decrease in detection accuracy that may occur in an optical sensor such as a toner sensor due to reflected light from the irradiated surface.

[0110] <Point 2> As shown in FIG. 1 and the like, the rotating body may be an endless belt stretched around a cylindrical driving roller 12b and / or a driven roller 12d. In this case, the surface of the rotating body may be a cylindrical side surface formed by winding the endless belt around the driving roller 12b. As shown in FIG. 8 and FIG. 9(A), the first irradiation light 46 is light that is emitted from the first opening 40 and proceeds to the first irradiated region 47. The light emitting element and the first opening are arranged so that the first irradiation light 46 is inclined with respect to the normal line of the cylindrical side surface in both the rotation direction of the rotating body and the width direction of the driving roller 12b (the axial direction of the rotating body). This makes it possible to suppress a decrease in detection accuracy that may occur due to reflected light from the irradiated surface in an optical sensor such as a toner sensor.

[0111] <Point 3> As shown in Fig. 22, the surface of the rotating body may be a plane that exists between the driving roller 12b and the driven roller 12d on the outer circumferential surface of the endless belt. As shown in Fig. 23 and Fig. 24(A), the first irradiation light 46 is inclined with respect to the normal line of the plane in both the rotation direction of the rotating body and the width direction of the driving roller (the axial direction of the rotating body). The light emitting element and the first opening are arranged so that this condition is satisfied. This makes it possible to suppress a decrease in detection accuracy that may occur due to reflected light from the irradiated surface in an optical sensor such as a toner sensor.

[0112] <Point 4> 10 and 12(A), the first opening 40 and the light-emitting element are arranged so that the specularly reflected light formed by the reflection of the first irradiation light 46 on the first irradiated region 47 travels in a direction away from the second opening 41 and the first light-receiving unit 36. This allows the first light-receiving unit 36 ​​to accurately detect the diffusely reflected light from the toner image.

[0113] <Point 5> A plurality of grooves (e.g., groove 83) may be formed on the surface of the rotating body. The first opening 40, the second opening 41, and the light-emitting element are arranged so that diffracted light generated by the first irradiation light 46 being incident on the first irradiated region 47 is unlikely to be incident on the second opening 41. This allows the first light-receiving unit 36 ​​to accurately detect diffusely reflected light from the toner image.

[0114] <Point 6> 5A, the grooves 83 may extend parallel to the direction of rotation of the rotor. In such a case, diffracted light may occur, and the optical sensor 31 described in the first to third embodiments may be effective.

[0115] <Point 7> 28, the reflection characteristics (scattering characteristics) of the surface of the rotating body may be different between the rotation direction of the rotating body and the width direction of the rotating body. In such a case, the optical sensor 31 described in relation to the first to third embodiments will be effective.

[0116] <Points 8 and 9> A first lens (e.g., first lens portion 43) may be disposed between first opening 40 and first irradiated region 47. A second lens (e.g., second lens portion 44) may be disposed between first irradiated region 47 and second opening 41.

[0117] <Points 10-13> The housing 33 may have a third opening 42 and a fourth opening (e.g., a part of the second opening 41). The third opening 42 is provided in a third light guide path arranged between the light emitting element and a second irradiated area 50 of the irradiated surface, which is different from the first irradiated area. The third opening 42 is arranged so that the light output from the light emitting element is directed toward the second irradiated area 50. As illustrated in FIG. 8 and the like, the fourth opening is provided in a fourth light guide path arranged between the second irradiated area 50 and the second light receiving unit 37. The fourth opening is arranged so that when the surface of the rotating body passes through the second irradiated area 50, the specular reflected light from the surface passes through the fourth opening. This makes it possible to accurately detect the specular reflected light from the surface of the rotating body. A third lens (e.g., the third lens portion 45) may be arranged between the third opening 42 and the second irradiated area 50. The second opening and the fourth opening may be the same opening (e.g., the second opening 41).

[0118] As shown in FIG. 8 and other figures, the optical path through which the first irradiation light 46 passes is an example of a first light guide path that guides the light output from the light-emitting element to the irradiated surface that is a part of the surface of the rotating body. As shown in FIG. 8 and other figures, the optical path through which the diffusely reflected light passes from the first irradiated area 47 toward the first light-receiving unit 36 ​​is an example of a second light guide path that guides the diffusely reflected light from the irradiated area of ​​the irradiated surface to which light is irradiated. The first light guide path (first opening) satisfies the following conditions. The first condition is that the irradiated area moves away from the intersection point between the normal line passing through the center of the light-emitting element among the normal lines to the mounting surface of the light-emitting element and the surface of the rotating body in a first direction that is the moving direction of the rotating body. The second condition is that the irradiated area moves away from the intersection point in a second direction that is perpendicular to the first direction and parallel to the rotation axis of the rotating body (drive roller 12b). In other words, the center of the first illuminated area 47 is shifted from the position where the normal line passing through the LED 35 among the normal lines of the circuit board 34 intersects with the surface of the rotating body (the position directly above the LED 35). This shift occurs in both the rotation direction of the rotating body and the width direction of the rotating body. This makes it possible to suppress a decrease in detection accuracy that may occur in an optical sensor such as a toner sensor due to reflected light from the illuminated surface.

[0119] <Points 14, 23> The photosensitive drum 1, intermediate transfer belt 12a, secondary transfer roller 16, etc. form an image forming section that forms a toner image on sheet S via a rotating body. An optical sensor 31 detects specularly reflected light from the surface of the rotating body and diffusely reflected light from the toner image carried on the surface of the rotating body. A controller 29 functions as a correction section that corrects the formation position of the toner image or the density of the toner image based on the detection result of the optical sensor 31. This makes it possible to perform color shift correction, density correction of the toner image, and color correction with high accuracy.

[0120] <Point 15> As shown in FIG. 4(A), a plurality of grooves 83 may be formed on the surface of the rotating body. As shown in FIG. 29(A), the first irradiation light 46 is light emitted from the first opening and proceeds to the first irradiated region. The light emitting element and the first opening are arranged so that the first irradiation light 46 is inclined from the normal line of the cylindrical surface generated in a part of the surface of the rotating body toward the direction in which the plurality of grooves are arranged. As shown in FIG. 29(A) and FIG. 30(A), the second opening may be arranged at a position that avoids the m-th order diffracted light and the (m+1)-th order diffracted light (m is an integer) of the light originating from the first irradiation light 46 irradiated to the irradiated surface.

[0121] <Point 16> As shown in Figure 29 (A), the first opening and the light-emitting element may be arranged so that the specularly reflected light formed by reflection of the first irradiation light 46 at the first irradiated region travels in a direction away from the second opening and the first light-receiving unit.

[0122] <Point 17> As shown in FIG. 30(A), the second opening may be disposed at a position that avoids the −1st to +1st order diffracted light of the light originating from the first irradiation light 46 that is irradiated to the irradiated surface.

[0123] <Point 18> 30(A), the second aperture is disposed at a position avoiding the m-th order diffracted light and the (m+1)-th order diffracted light among the light originating from the first irradiation light irradiated to the irradiated surface. In particular, the second aperture may be disposed at a substantially central portion between the m-th order diffracted light and the (m+1)-th order diffracted light. m is, for example, -6.

[0124] <Point 19> 30(A), the first light receiving unit can be disposed at a position where m-th order diffracted light and (m+1)-th order diffracted light are not incident on the light originating from the first irradiation light 46 irradiated to the irradiated surface (m is an integer). m is, for example, −6.

[0125] <Point of View 20> 30(A), the first light receiving unit, the second light receiving unit, and the light emitting element may be arranged in a line along the direction (y, y1 direction) in which the grooves 83 formed in the rotor are arranged. The first light receiving unit may be arranged farther from the light emitting element than the second light receiving unit.

[0126] <Points 21 and 22> 30(A) and the like, a first lens (e.g., first lens portion 43) may be disposed between the first opening and the first irradiated region. The focal point of the first lens may substantially coincide with the position of the light emitting element.

[0127] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0128] 31: optical sensor, 32: housing, 34: circuit board, 35: LED, 36: first light receiving unit, 40: first opening, 41: second opening

Claims

1. A light emitting element that irradiates light onto an irradiated surface that is set on a part of the surface of a rotating body; a first light receiving unit that receives diffusely reflected light from a toner image formed on a surface of a rotating body; a second light receiving unit that receives specularly reflected light from a surface of the rotating body; a circuit board on which the light emitting element, the first light receiving unit, and the second light receiving unit are mounted; a housing having a first opening and a second opening, the housing being provided to surround the light emitting element, the first light receiving unit, and the second light receiving unit; the first opening is provided in a first light guide path disposed between the light emitting element and a first irradiated region of the irradiated surface, and is disposed such that light output from the light emitting element is directed toward the first irradiated region; The second opening is provided in a second light guide path arranged between the first irradiated area and the first light receiving unit, and is arranged so that when the toner image passes through the first irradiated area, diffusely reflected light from the toner image passes through, and when the surface of the rotating body passes through the first irradiated area, specularly reflected light from the surface, and diffusely reflected light or diffracted light do not pass through.

2. The rotating body is an endless belt stretched between a cylindrical driving roller and a driven roller, the surface of the rotating body is a cylindrical side surface formed by winding the endless belt around the driving roller or the driven roller, 2. The optical sensor of claim 1, wherein the light-emitting element and the first opening are arranged so that first illumination light, which is light emitted from the first opening and travels to the first illuminated area, is inclined in both the rotational direction of the rotating body and the axial direction of the rotating body with respect to the normal to the cylindrical side surface.

3. The rotating body is an endless belt stretched between a cylindrical driving roller and a driven roller, the surface of the rotating body is a plane that exists between the driving roller and the driven roller on the outer circumferential surface of the endless belt, 2. The optical sensor of claim 1, wherein the light-emitting element and the first opening are arranged so that first illumination light, which is light emitted from the first opening and travels to the first irradiated area, is inclined in both the rotation direction of the rotating body and the axial direction of the rotating body with respect to the normal to the plane.

4. The optical sensor of claim 2 or 3, characterized in that the first opening and the light-emitting element are arranged so that the specular reflected light formed by the reflection of the first irradiation light at the first irradiated area travels in a direction away from the second opening and the first light-receiving unit.

5. A plurality of grooves are formed on the surface of the rotor, An optical sensor as described in any one of claims 2 to 4, characterized in that the first opening, the second opening and the light-emitting element are arranged so that diffracted light generated by the first irradiation light being incident on the first irradiated region is less likely to be incident on the second opening.

6. 6. The optical sensor according to claim 5, wherein the plurality of grooves extend parallel to a direction of rotation of the rotating body.

7. 5. The optical sensor according to claim 1, wherein the reflection characteristics of the surface of the rotating body are different between the rotation direction of the rotating body and the width direction of the rotating body.

8. The optical sensor according to claim 1 , further comprising a first lens disposed between the first opening and the first illuminated region.

9. 9. The optical sensor according to claim 1, further comprising a second lens disposed between the first illuminated region and the second opening.

10. the housing has a third opening and a fourth opening; the third opening is provided in a third light guide path arranged between the light emitting element and a second irradiated area of ​​the irradiated surface which is different from the first irradiated area, and is arranged such that light output from the light emitting element is directed toward the second irradiated area; The optical sensor according to any one of claims 1 to 9, characterized in that the fourth opening is provided in a fourth light guide path arranged between the second irradiated area and the second light receiving unit, and is arranged so that specularly reflected light from the surface of the rotating body passes through when the surface passes through the second irradiated area.

11. The optical sensor according to claim 10 , further comprising a third lens disposed between the third opening and the second illuminated area.

12. 12. The optical sensor according to claim 10, wherein the second opening and the fourth opening are the same opening.

13. The first opening and the light emitting element are arranged so that a specular reflection light formed by the first irradiation area being reflected by the first irradiation area, which is a light emitted from the first opening and traveling to the first irradiation area, travels in a direction away from the second opening and the first light receiving unit.

2. The optical sensor according to claim 1.

14. the first light receiving unit, the second light receiving unit, and the light emitting element are arranged in a line along a direction in which a plurality of grooves formed on the rotating body are arranged, The first light receiving unit is disposed farther from the light emitting element than the second light receiving unit.

2. The optical sensor according to claim 1.

15. The optical sensor according to claim 1 , further comprising a first lens disposed between the first opening and the first illuminated area.

16. 16. The optical sensor according to claim 8, wherein a focal point of the first lens substantially coincides with a position of the light emitting element.

Images