Optical inspection device and image forming device

Abstract

To reduce the irradiation diameter of a light beam on a measuring object and align the angles of incidence of rays of light in the light beam on the measuring object, thereby improving resolution in detecting the diffusion distribution of reflected light from the measuring object.SOLUTION: An optical inspection device 3 comprises: a surface light source 4; optical elements 5 including a collimator lens 51; an aperture member 6 having an aperture 61 that regulates a light beam passing through the collimator lens 51; and a light receiver 7. The diameter D1 of the aperture 61 is smaller than an effective diameter of an optical element, of the optical elements 5, which is arranged closer to the surface light source 4 than the aperture 61, and the length L1 in the axial direction of the aperture 61 is larger than the diameter D1 of the aperture 61.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, there has been an increasing demand for higher image quality in image forming devices such as printers and MFPs. One of the evaluation indices for the image quality of printed materials output by image forming devices is the gloss of a toner image.

[0003] Generally, the gloss of a toner image is measured by measuring the reflected light of light irradiated onto the toner image. The diffuse distribution of the reflected light varies depending on the surface shape and scattering characteristics of the toner image. When a toner image has high gloss, the surface irregularities of the toner image are minute, so the diffuse distribution of the reflected light from the toner image of the incident light has a stronger specular reflection component. On the other hand, when a toner image has low gloss, the surface irregularities of the toner image are large, so compared to when the toner image has high gloss, the diffuse distribution of the reflected light has a weaker specular reflection component and a stronger component of light scattered in various directions. The gloss of a toner image is measured based on this diffuse distribution of the reflected light.

[0004] As a background art in this technical field, Patent Document 1 describes an apparatus that enables the gloss value of an object to be measured to be detected simply and accurately (see abstract). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-4541 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 describes a diaphragm (5a) for the projection light (L1), but does not describe its specific configuration, and the disclosed configuration does not allow the diaphragm (5a) to regulate the spread angle of the light beam, which results in a large irradiation diameter and spread angle of the light beam on the measurement object.

[0007] The diffuse distribution of reflected light from a measurement object, such as a toner image, changes due to minute changes in the surface irregularities and scattering characteristics of the object. However, if the irradiated diameter of the light beam on the measurement object is large and the incident angles of each light beam on the object are uneven, the effects of minute changes in the irregularities are averaged out, and the beam's original divergence angle is large. As a result, even when the surface irregularities or scattering characteristics change, the change in the diffuse distribution of reflected light is small, resulting in reduced sensitivity. In other words, the resolution when detecting the diffuse distribution of reflected light is reduced.

[0008] An object of the present invention is to reduce the irradiation diameter of the light beam on the object to be measured, align the incident angles of each light beam in the light beam on the object to be measured, and thereby increase the resolution when detecting the diffuse distribution of reflected light from the object to be measured. [Means for solving the problem]

[0009] The above-mentioned problems of the present invention are solved by the following means.

[0010] (1) An optical inspection device that irradiates a measurement object with light and receives reflected light, comprising: a surface light source; an optical element including a collimator lens that makes a light beam emitted from the surface light source closer to parallel light; an aperture member having an aperture that regulates the light beam that has passed through the collimator lens; and a light receiver that receives light that has passed through the aperture and is reflected by the measurement object and obtains outputs at a plurality of positions, wherein the diameter of the aperture is smaller than the effective diameter of an optical element that is arranged closer to the surface light source than the aperture, and the axial length of the aperture is larger than the diameter of the aperture. The shape of the tip of the aperture member is a conical portion so as to be parallel to the surface of the object to be measured. , optical inspection equipment.

[0011] (2) The optical inspection device according to (1), wherein the optical receiver is composed of a plurality of photosensors.

[0012] (3) The optical inspection device according to (1), wherein the light receiver is a one-dimensional line sensor.

[0013] (4) The optical inspection device according to (1), wherein the light receiver is a two-dimensional area sensor.

[0014] (5) The optical inspection device according to (1), wherein the optical inspection device is disposed within an image forming device.

[0015] (6) The optical inspection device according to (1), wherein the object to be measured is a sheet-like recording medium.

[0016] (7) The optical inspection device according to (1), wherein the object to be measured is a toner image on a sheet-like recording medium.

[0017] (8) The optical inspection device according to (1), wherein the aperture member is positioned closer to the object to be measured than the optical element among the optical elements that is positioned closest to the object to be measured.

[0018] (9) The optical inspection device according to (1), wherein the angle of incidence of light on the optical axis of the light beam irradiated onto the object to be measured is set to 60 degrees.

[0019] (10) The optical inspection device according to (1), wherein the optical path length from the tip of the aperture to the object to be measured is set to 5 mm or less.

[0020] (11) When the maximum distance between the outermost rays of the light beams irradiated onto the object to be measured is defined as the irradiation diameter, the diameter of the aperture and the length of the aperture in the axial direction are and the incident angle of the light beam irradiated onto the measurement object and the optical path length to the measurement object are The optical inspection device according to (9) or (10) above, wherein the irradiation diameter is set to be 5 mm or less.

[0021] (12) The optical inspection device according to (1), wherein the optical element includes a beam expander disposed between the collimator lens and the aperture member to expand or reduce the diameter of the light beam.

[0022] (13) The optical inspection device described in (12) above, wherein D / D1 is set to be 2 or more and 5 or less, where D1 is the diameter of the aperture and D is the light beam width on the end face of the aperture facing the surface light source.

[0023] (14) The optical inspection device according to (1), wherein the collimator lens has a numerical aperture NA of 0.5 or more.

[0024] (15) An image forming apparatus equipped with the optical inspection device described in (1) above. [Effects of the Invention]

[0025] According to the present invention, the irradiation diameter of the light beam on the object to be measured can be reduced, and the incident angle of each light beam in the light beam on the object to be measured can be aligned, thereby improving the resolution when detecting the diffuse distribution of reflected light from the object to be measured. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a cross-sectional view schematically showing the configuration of an optical inspection device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view schematically showing the aperture member shown in FIG. [Figure 3] 10A and 10B are diagrams for explaining the relationship between the shape of an aperture and the irradiation diameter. [Figure 4] 10A and 10B are diagrams for explaining the relationship between the diameter of an aperture and the beam width on the end face of the aperture. [Figure 5A] 5A and 5B are diagrams for explaining the relationship between the distribution of light irradiated onto the object to be measured and the output distribution shape of the light receiver in the present embodiment. [Figure 5B] 5A and 5B are diagrams for explaining the relationship between the distribution of light irradiated onto the object to be measured and the output distribution shape of the light receiver in the present embodiment. [Figure 5C] 10A and 10B are diagrams for explaining the relationship between the distribution of light irradiated onto the measurement object and the output distribution shape of the light receiver in a comparative example. [Figure 5D] 10A and 10B are diagrams for explaining the relationship between the distribution of light irradiated onto the measurement object and the output distribution shape of the light receiver in a comparative example. [Figure 6A] FIG. 10 is a diagram showing an output distribution shape acquired by a photoreceiver when a mirror surface is used as a measurement object. [Figure 6B] 10A and 10B are diagrams showing output distribution shapes acquired by a light receiver when various types of paper are used as measurement objects. [Figure 6C] 10A and 10B are diagrams illustrating output distribution shapes acquired by a light receiver when toner images formed on the same type of paper and having different glossiness due to different fixing conditions are used as measurement objects. [Figure 7] 1 is a cross-sectional view schematically illustrating a configuration of an image forming apparatus in which an optical inspection device according to the present embodiment is mounted. [Figure 8] FIG. 2 is a block diagram showing a main part of a control configuration of an image forming apparatus including an optical inspection device. [Figure 9A] 10A and 10B are diagrams illustrating an example of a toner image formed in a margin at a side edge perpendicular to the conveyance direction of a sheet of paper. [Figure 9B] 10A and 10B are diagrams illustrating an example of a toner image formed in a margin at an end of a sheet in the transport direction. DETAILED DESCRIPTION OF THE INVENTION

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the accompanying drawings. In each drawing, the same or similar components are denoted by the same reference numerals, and redundant explanations thereof will be omitted as appropriate.

[0028] 1 is a cross-sectional view schematically showing the configuration of an optical inspection device 3 according to one embodiment of the present invention. This optical inspection device 3 is disposed inside an image forming device 100 (see FIG. 7), such as a printer or an MFP.

[0029] As shown in Fig. 1, the optical inspection device 3 irradiates a measurement object 31 with light and receives reflected light. The measurement object 31 is, for example, a sheet-like recording medium such as paper, or a toner image on a sheet-like recording medium. The optical inspection device 3 includes a surface light source 4, an optical element 5, an aperture member 6, a light receiver 7, and a scattered light receiver 8.

[0030] The surface light source 4 has a planar light-emitting surface (e.g., 0.76 mm x 0.76 mm) so as to ensure a sufficient amount of light. In this embodiment, a white LED is used for the surface light source 4. The white LED is formed, for example, by sealing a GaN-based blue LED chip with a resin material in which a yellow fluorescent substance is dispersed. However, the surface light source 4 is not limited to this configuration. The angle of incidence of light on the optical axis CL of the light beam irradiated onto the measurement object 31 is set to 60 degrees. In other words, the surface light source 4 is positioned so that the angle of incidence of light emitted from the surface light source 4 with respect to the measurement object 31 is 60 degrees.

[0031] The optical element 5 includes a collimator lens 51 and a beam expander 52. The collimator lens 51 and the beam expander 52 are arranged along the optical axis CL. The collimator lens 51 is an optical element that converts the light beam emitted from the surface light source 4 into parallel light. Here, in order to increase the light utilization efficiency, a bright collimator lens 51 with a numerical aperture NA of 0.5 or more (for example, a numerical aperture NA of 0.68) is used. This allows a large amount of light from the surface light source 4 to be captured.

[0032] The beam expander 52 is disposed between the collimator lens 51 and the aperture member 6 and is an optical element that expands or reduces the diameter of the beam. The beam expander 52 is configured by combining a convex lens 53 (for example, a focal length f = 18 mm) and a concave lens 54 (for example, a focal length f = 6 mm). Because the diameter of the beam emitted from the collimator lens 51 is large, the beam expander 52 is used to narrow the beam diameter while maintaining the beam angle. For example, the beam diameter φ5 after the second surface of the collimator lens 51 is narrowed to a beam diameter φ1.7 after the second surface of the concave lens 54. In other words, the use of the beam expander 52 increases the beam passing through the aperture 61 of the aperture member 6, thereby increasing the amount of light reaching the photodetector 7. Note that if a sufficient amount of light reaches the photodetector 7, the beam expander 52 can be omitted.

[0033] FIG. 2 is an enlarged cross-sectional view schematically showing the aperture member 6 shown in FIG. As shown in FIG. 2 , the aperture member 6 has an aperture 61 that restricts the light beam that has passed through the collimator lens 51. The aperture 61 is a through-hole formed in the aperture member 6 along the optical axis CL. The light emitted from the surface light source 4 cannot be converted into completely parallel light even with the collimator lens 51. This is because the surface light source 4 emits light from the entire light-emitting surface, and light is also incident on the collimator lens 51 from outside the optical axis CL. The aperture 61 has an axial length L1 (thickness) (e.g., L1 = 3 mm) so that only nearly parallel light B1 reaches the measurement object 31. In this embodiment, the axial length L1 of the aperture 61 is set to be larger than the diameter D1 of the aperture 61. Light B2 that is angled with respect to the optical axis CL hits the inner wall of the aperture 61, is attenuated, and is not emitted, and only nearly parallel light B1 is emitted from the aperture 61.

[0034] Even if the divergence angle of the light beam is restricted as described above, completely parallel light is not emitted from aperture 61. Therefore, in order to reduce irradiation diameter D2 on measurement object 31 (see FIGS. 3, 5A, etc.), aperture 61 needs to have a small diameter D1 and be positioned close to measurement object 31. Irradiation diameter D2 is the maximum distance between the outermost rays of the light beam irradiated onto measurement object 31 on said measurement object 31. In this embodiment, diameter D1 of aperture 61 is set smaller than the effective diameter of the optical element 5 that is positioned closer to surface light source 4 than aperture 61.

[0035] 3 is a diagram illustrating the relationship between the shape of aperture 61 and irradiation diameter D2. Diameter D1 and axial length L1 of aperture 61 are set so that irradiation diameter D2 is 5 mm or less.

[0036] As shown in FIG. 3, the irradiation diameter D2 of the light beam emitted from the aperture 61 on the measurement object 31 is expressed by the following formula, where D1 is the diameter of the aperture 61, L1 is the length (thickness) in the axial direction, α is the angle of incidence, and L2 is the optical path length to the measurement object 31. D2=2×x / tanα+x / tan(90+θ-α)+x / tan(90-θ-α) where: x=(D3 / 2)×sinα D3 = D1 + 2 × L2 × tanθ θ=Arctan(D1 / L1) is.

[0037] Fig. 4 is a diagram for explaining the relationship between diameter D1 of aperture 61 and light beam width D on the end face of aperture 61. As shown in Fig. 4, when the diameter of aperture 61 is D1 and the light beam width (light beam diameter) on the end face of aperture 61 on the surface light source 4 side is D, D / D1 is set to be 2 or more and 5 or less.

[0038] As shown in FIG. 1, aperture member 6 is arranged closer to measurement object 31 than the optical element of optical elements 5 that is arranged closest to measurement object 31 (here, concave lens 54 of beam expander 52). The optical path length L2 from the tip of aperture 61 (the end on the measurement object 31 side) to measurement object 31 is set to 5 mm or less. In order to bring aperture member 6 closer to measurement object 31, the shape near the tip of aperture member 6 is made into a conical portion 62 so that it is parallel to the surface of measurement object 31. Therefore, here, the optical path length L2 from the tip of aperture 61 to the surface of measurement object 31 is brought closer to approximately 3 mm.

[0039] The photoreceiver 7 receives light reflected by the measurement object 31 after passing through the aperture 61, and obtains outputs corresponding to the amount of light received at each of a plurality of positions. In this embodiment, the photoreceiver 7 is a linear sensor (one-dimensional line sensor). Here, for example, a C-MOS or CCD linear sensor (photodiode array) with a pixel pitch of 63.5 μm and 128 pixels is used. Here, the photoreceiver 7 sequentially outputs analog voltages of 128 pixels.

[0040] The light receiver 7 is placed at a position where it forms an angle of 60 degrees with respect to the normal to the surface of the object to be measured 31, on the opposite side of the surface light source 4 across the point of light incidence. Therefore, specularly reflected light, which is reflected by the object to be measured 31 at an angle of 60 degrees and has an equal angle of incidence and reflection, and its surrounding light are incident on the light receiver 7. The optical path length L3 from the object to be measured 31 to the light receiver 7 is set to 12 mm here. A shorter optical path length L3 is desirable because the luminous flux width spreads even during this length.

[0041] The scattered light receiver 8 is placed in a position normal to the surface of the object to be measured 31, that is, vertically above the point of incidence of light in FIG. 1. Therefore, scattered light reflected by the object to be measured 31 is incident on the scattered light receiver 8. As will be described later, the scattered light receiver 8 is provided to determine the color of the toner image and to detect the reading timing of the receiver 7. However, if the optical inspection device 3 is used in an environment where such information is not necessary, the scattered light receiver 8 can be omitted.

[0042] As described above, the optical inspection device 3 of this embodiment includes the surface light source 4, the optical element 5 including the collimator lens 51, the aperture member 6 having the aperture 61 that regulates the light beam that has passed through the collimator lens 51, and the light receiver 7. The diameter D1 of the aperture 61 is smaller (e.g., φ0.5) than the effective diameter of the optical element of the optical element 5 that is arranged closer to the surface light source 4 than the aperture 61, and the axial length L1 of the aperture 61 is greater than the diameter D1 of the aperture 61.

[0043] To improve the resolution of the diffuse distribution of reflected light detected by the light receiver 7, such as a linear sensor, it is necessary to improve the sensitivity of the output distribution shape of the light receiver 7 to minute changes in the shape and scattering characteristics of the toner image surface. Here, we consider the relationship between the distribution of the irradiated light (irradiation diameter D2 and incident angle) irradiated to the measurement object 31 and the output distribution shape of the light receiver 7.

[0044] 5A and 5B are diagrams for explaining the relationship in this embodiment between the distribution of irradiation light irradiated onto the measurement object 31 and the output distribution shape of the light receiver 7. Figures 5C and 5D are diagrams for explaining the relationship in a comparative example between the distribution of irradiation light irradiated onto the measurement object 31 and the output distribution shape of the light receiver 7.

[0045] In this embodiment, aperture 61 can restrict the light beam to a diameter narrower than the effective lens diameter of the optical element disposed on the surface light source 4 side of aperture 61 within optical element 5. Furthermore, by providing thickness to aperture 61, only light B1 that is nearly parallel is emitted from aperture 61 (see FIG. 2). This makes it possible to reduce irradiation diameter D2 on measurement object 31 and align the angle of incidence.

[0046] Therefore, as shown in Fig. 5A, when measuring a surface that is smooth and does not scatter, such as a mirror surface, a sharp distribution is obtained as the output distribution of the photodetector 7. Also, as shown in Fig. 5B, when measuring a toner image or the like that has an uneven surface and scattering properties, the spread angle of the light beam traveling from the measurement object 31 to the photodetector 7 changes due to the influence of the surface unevenness and scattering inside the toner. As a result, the output distribution shape obtained by the photodetector 7 becomes broad.

[0047] On the other hand, as shown in Fig. 5C, in the comparative example in which the irradiation diameter D2 on the measurement target 31 is large and the incident angle is non-uniform, even when measuring a mirror surface, the angle of the reflected light heading toward the light receiver 7 is non-uniform, resulting in a broad output distribution shape. Furthermore, as shown in Fig. 5D, when measuring a toner image or the like that has an uneven surface and scattering properties, the effect of minute changes in the surface unevenness is averaged out, and the divergence angle of the light beam is originally large. Therefore, even when the surface unevenness or scattering properties change, the change in the output distribution shape is small.

[0048] As described above, according to this embodiment, the irradiation diameter D2 of the light beam on the object to be measured 31 can be reduced, and the incident angles of each light beam in the light beam to the object to be measured can be aligned, thereby improving the resolution when detecting the diffuse distribution of reflected light from the object to be measured 31.

[0049] Furthermore, in this embodiment, by using a linear sensor (one-dimensional line sensor) for the light receiver 7, the diffusion distribution of reflected light can be detected with higher accuracy. The light receiver 7 is not limited to a linear sensor (one-dimensional line sensor) and may be a two-dimensional area sensor or may be composed of multiple photosensors. By using a two-dimensional area sensor for the light receiver 7, the two-dimensional diffuse distribution of reflected light can be detected with higher accuracy. By using multiple photosensors for the light receiver 7, the amount of specular reflected light and light other than specular reflected light can be detected, and the diffuse distribution of reflected light can be obtained.

[0050] Furthermore, in this embodiment, the aperture member 6 is located closer to the measurement object 31 than the optical element 5 that is arranged closest to the measurement object 31. This allows the distribution of the irradiation light irradiated onto the measurement object 31 (the irradiation diameter D2 and the incident angle) to be more regulated.

[0051] In this embodiment, the angle of incidence of light on the optical axis CL of the light beam irradiated onto the measurement object 31 is set to 60 degrees. Here, 60 degrees is not limited to the exact physical value of 60 degrees, but also includes the concept of approximately 60 degrees (for example, a difference of about 5 degrees). This makes it possible to accommodate measurement objects 31 with a wide range of gloss levels.

[0052] In addition, in this embodiment, the optical path length L2 from the tip of the aperture 61 to the object to be measured 31 is set to 5 mm or less, which reduces the influence of the spread of the irradiation diameter D2 caused by the spread angle of the light beam irradiated onto the object to be measured 31.

[0053] In this embodiment, the diameter D1 of the aperture 61 and the axial length L1 of the aperture 61 are set so that the irradiation diameter D2 is 5 mm or less. When the irradiation diameter D2 is large, a broad output distribution shape is obtained even when measuring a mirror surface, as shown in FIG. 5C, and the change in the output distribution shape is small even when measuring a toner image or the like with an uneven surface and scattering properties, as shown in FIG. 5D. In this embodiment, by setting the irradiation diameter D2 to 5 mm or less, the resolution when detecting the diffuse distribution of reflected light from the measurement object 31 can be further improved.

[0054] Furthermore, in this embodiment, the optical element 5 includes a beam expander 52 disposed between the collimator lens 51 and the aperture member 6. This makes it possible to reduce the beam diameter while maintaining the beam angle after the collimator lens 51, thereby increasing the beam passing through the aperture 61 and ensuring a large amount of light.

[0055] Furthermore, in this embodiment, by setting the luminous flux width D / (diameter D1 of aperture 61) to be equal to or greater than 2 and equal to or less than 5, the amount of light is not wasted and the risk of the luminous flux being vignetted by aperture 61 can be reduced. In other words, when reducing the luminous flux diameter using beam expander 52, in order to avoid wasting the amount of light, it is better if the luminous flux width D on the end face of aperture 61 facing the surface light source 4 is as close to diameter D1 of aperture 61 as possible. However, if it is too close, there is a higher risk that the luminous flux will be vignetted by aperture 61 and the amount of luminous flux passing through aperture 61 will be reduced due to decentering of the surface light source 4, optical element 5, and aperture 61.

[0056] Furthermore, in this embodiment, the brightness of the collimator lens 51 is set to a numerical aperture NA of 0.5 or more, so that the amount of light irradiated onto the measurement object 31 can be more secure. When using a surface light source 4, if the brightness of the collimator lens 51 is high, the light beam angle after the collimator lens 51 becomes large, resulting in a large irradiation diameter D2 on the measurement object 31. However, by regulating the light beam angle with the aperture 61, it is possible to reduce the irradiation diameter D2 on the measurement object 31 even if the brightness of the collimator lens 51 is high.

[0057] FIG. 6A is a diagram showing the output distribution shape acquired by the light receiver 7 when a mirror surface is used as the measurement object 31. FIG. 6B is a diagram showing the output distribution shape acquired by the light receiver 7 when various types of paper are used as the measurement object 31. FIG. 6C is a diagram showing the output distribution shape acquired by the light receiver 7 when toner images (solid black) with different glossiness formed on the same type of paper due to differences in fixing conditions are used as the measurement object 31. In FIGS. 6A to 6C, the horizontal axis indicates the position on the surface of the line sensor serving as the light receiver 7 as the number of pixels from the edge pixel, and the vertical axis indicates the output at each pixel of the line sensor.

[0058] As shown in FIG. 6A, when a mirror surface is used as the measurement object 31, the output distribution shape is narrow and sharp. As shown in FIG. 6B, when paper with minimal surface irregularities, such as Espritcoat (Paper A; manufactured by Nippon Paper Industries Co., Ltd.), changes in the spread angle of the light beam due to reflection are small. For this reason, when Espritcoat (Paper A) is used, the output distribution shape is narrow and sharp with a high peak value. On the other hand, when paper with a rough surface and significant irregularities, such as color copy paper (Paper C; manufactured by Mondi), the output distribution shape is broad with a low peak value. Therefore, it can be seen that glossiness can be determined from differences in the shape, such as the peak value and width, of the output distribution shape.

[0059] The measurement results shown in Figure 6C are for toner images (solid black) with different glossiness formed using the same type of paper, POD coated (Paper B; manufactured by Oji Paper Co., Ltd.), under different fixing conditions I and II. The glossiness can also be determined from the difference in output distribution shape, even with slight surface irregularities and changes in scattering characteristics due to differences in fixing conditions.

[0060] In this embodiment, the optical inspection device 3 is placed inside the image forming apparatus 100 (see FIG. 7). Here, when the optical inspection device 3 is placed before printing (upstream of the image forming unit 13 (see FIG. 7) in the paper transport direction), it can be used to determine the paper type. When the measurement object 31 is a sheet-like recording medium such as paper, information on the surface properties of the measurement object 31 can be obtained and fed back to the process conditions to be optimized. On the other hand, when the optical inspection device 3 is placed after printing (downstream of the image forming unit 13 in the paper transport direction) (see FIG. 7), it can measure the gloss of the toner image and feed back the result to the fixing conditions. When the measurement object 31 is a toner image on a sheet-like recording medium, it can be fed back to the fixing conditions, etc., and the desired image gloss can be stably obtained.

[0061] 7 is a cross-sectional view schematically showing the configuration of an image forming apparatus 100 equipped with the optical inspection device 3 of this embodiment. FIG. 8 is a block diagram showing the main parts of the control configuration of the image forming apparatus 100 including the optical inspection device 3.

[0062] 7, image forming apparatus 100 includes a first unit 1 that forms a toner image on a sheet of paper as a sheet-like recording medium, and a second unit 2 that inspects the paper on which the toner image has been formed by irradiating it with light. First unit 1 includes document reading section 11, paper feeding section 12, image forming section 13, fixing section 14, and engine control section 15 (see FIG. 8). Meanwhile, second unit 2 includes an optical inspection device 3.

[0063] The document reading unit 11 scans and exposes an image on the document, and reads the reflected light with a line image sensor to obtain an image signal. This image signal undergoes A / D conversion, compression, and other processing, and is then input as image data to the engine control unit 15. Note that the image data input to the engine control unit 15 may be received from an external device connected to the image forming apparatus 100.

[0064] The paper feed unit 12 supplies paper to the image forming unit 13. In this case, paper stored in a tray 121 in the paper feed unit 12 is supplied, but paper may also be supplied from an external paper feed device connected to the image forming apparatus 100.

[0065] Image forming unit 13 is configured here by arranging a plurality of photoconductors 131 in a vertical direction facing a single intermediate transfer belt 132. The plurality of photoconductors 131 are provided corresponding to the colors C (cyan), M (magenta), Y (yellow), and K (black). Image forming unit 13 forms a full-color toner image on paper supplied by paper feed unit 12.

[0066] The fixing unit 14 fixes the toner image onto the paper sheet on which the toner image has been formed. The fixing unit 14 has a pair of fixing members 141 (for example, a pair of rollers) that form a fixing nip portion, and a heater (not shown) that heats the fixing members 141. As the paper sheet passes through the fixing nip portion during the paper sheet transport process, the fixing unit 14 fixes the toner image onto the paper sheet through the action of pressure applied by the pair of fixing members 141 and the heat of the fixing members 141. The paper sheet that has been subjected to the fixing process by the fixing unit 14 is discharged onto the paper output tray 16.

[0067] As shown in FIG. 8 , the optical inspection device 3 provided in the second unit 2 includes a surface light source board 45, a light receiver board 75, a scattered light receiver board 85, and an optical inspection control unit 9. The surface light source board 45 includes the surface light source 4 and a driver 46 that operates the surface light source 4. The surface light source 4 emits white light to enable the color of the toner image to be determined. The light receiver board 75 includes the light receiver 7 and an AD converter 76 that sequentially converts the analog voltage output of the light receiver 7 into digital values. The scattered light receiver board 85 includes the scattered light receiver 8 and an AD converter 86 that converts the analog output of the scattered light receiver 8 into digital values. The scattered light receiver 8 includes a photodiode 81 with a red filter, a photodiode 82 with a green filter, and a photodiode 83 with a blue filter. Therefore, the scattered light receiver 8 can determine the color of the toner image. Furthermore, scattered light receiver 8 can obtain information on the timing of reading by light receiver 7 by determining whether or not a toner image is present.

[0068] The optical inspection control unit 9 includes a field programmable gate array (FPGA) 91 capable of high-speed processing, and a ROM 92. The FPGA 91 includes a line buffer 911, a RAM 912, a photoreceiver sensitivity correction unit 913, reflected light distribution data 914, a peak value measurement unit 915, a distribution width measurement unit 916, a paper type determination unit 917, a gloss control unit 918, a photoreceiver sensitivity setting unit 919, a corner solid detection unit 920, a color detection unit 921, and a control signal generation unit 922.

[0069] The line buffer 911 stores the reflected light distribution (here, digital values ​​of 128 pixels). The RAM 912 acquires white reference data, black reference data, and read data. The white reference data is the reflected light distribution obtained by reading a white reference plate. The black reference data is the reflected light distribution obtained by reading with the surface light source 4 turned off. The read data is the reflected light distribution obtained by reading a paper or toner image. The white reference data and black reference data are acquired in advance, before image formation. The photoreceiver sensitivity correction unit 913 normalizes the digital value of the reflected light distribution of the paper or toner image, setting the white reference data to 100% and the black reference data to 0%. The reflected light distribution data 914 is the digital value of the reflected light distribution normalized after sensitivity correction. The peak value measurement unit 915 measures the peak value of the reflected light from the toner image from the reflected light distribution of the toner image. The distribution width measurement unit 916 measures the distribution width of the reflected light from the paper from the reflected light distribution of the paper. The paper type determination unit 917 determines the paper type from the distribution width of the light reflected from the paper. The gloss control unit 918 determines fixing parameters (values ​​that increase or decrease gloss, such as fixing temperature) from the color, paper type, and peak value of the toner image. The receiver sensitivity setting unit 919 sets the sensitivity (exposure time) of the receiver 7 according to the paper type. The corner solid detection unit 920 determines the start and end positions of the toner image from the voltage difference between the paper (white) and the toner image (black / magenta / cyan, etc.). The color detection unit 921 determines the toner color from the voltage ratio of the color filter-equipped photodiodes 81-83. The control signal generation unit 922 generates control signals for sensitivity and reading timing to be sent to the receiver 7, and a control signal for light intensity to be sent to the surface light source 4.

[0070] The ROM 92 stores product-specific values ​​of the image forming apparatus 100. The product-specific values ​​include, for example, correlation data of toner color, paper type, peak value, and fixing parameters.

[0071] The engine control unit 15 provided in the first unit 1 is a computer equipped with a CPU, memories such as ROM and RAM, and an HDD as an auxiliary storage device, and controls processes related to image formation. For example, the engine control unit 15 has a fixing control unit 151 that controls the operation of the fixing unit 14. The fixing control unit 151 controls fixing conditions such as the temperature of the fixing member 141. Specifically, based on fixing parameters fed back from the gloss control unit 918 of the optical inspection device 3, the fixing control unit 151 increases or decreases the parameters that control the fixing unit 14 (such as the temperature of the fixing member 141) to adjust to the target gloss.

[0072] In the image forming apparatus 100, the optical inspection device 3 can measure the gloss of a toner image of, for example, 5 mm×5 mm printed on a sheet of paper while the sheet is being transported. Commercially available gloss meters measure reflectance using a photodiode, so fluctuations in paper position during transport directly lead to angular deviations in specular reflection, making measurement impossible. In contrast, the optical inspection device 3 of this embodiment uses a linear sensor for the light receiver 7, which widens the light receiving area and improves robustness against angular deviations, making it possible to monitor gloss while the paper is being transported.

[0073] 9A is a diagram showing an example of a toner image formed in a margin S at an end (left end in FIG. 9A) in a direction perpendicular to the transport direction F of a sheet of paper P. FIG. 9B is a diagram showing an example of a toner image formed in a margin S at an end (rear end in FIG. 9B) in the transport direction F of a sheet of paper P. As shown in Figures 9A and 9B, it is assumed that the gloss measurement of a toner image is performed by forming a toner mark M, such as a solid corner mark, in a margin S (non-image area) of paper P. The toner mark M as a toner image can be formed at any position in the margin S. The margin S is designed to be cut and removed in a later process.

[0074] A small image size is preferable because a large toner mark M results in an expanded non-image area and increased toner consumption. However, a small image size makes accurate measurement impossible because the image position shifts if the paper P slips during transport. To address this issue, the optical inspection device 3 itself is equipped with a read timing detection function. Because the scattered light from the paper P's surface and the scattered light from the toner image have different light intensities, this change is detected by the scattered light receiver 8 for toner color discrimination, and the optical inspection device 3 itself determines the measurement timing (read timing). These controls are implemented in the FPGA 91 that controls the optical inspection device 3. In addition, the FPGA 91 also has various functions, such as reading control for the receiver 7, measurement of reflectance and diffuse distribution from the read data, and toner color discrimination using the scattered light receiver 8. This allows gloss information to be measured and analyzed within the optical inspection device 3 without placing a burden on the CPU of the image forming device 100 itself.

[0075] In this way, when the optical inspection device 3 is installed in the image forming apparatus 100, the inspection results from the optical inspection device 3 are fed back to the printing conditions, making it possible to form higher quality images.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention. Furthermore, some of the configurations of the above embodiments can be added, deleted, or replaced.

[0077] For example, in the above-described embodiment, a white LED is used for the surface light source 4, but this is not limited to this. For example, if the optical inspection device 3 does not determine color, an LED of another color may be used for the surface light source 4.

[0078] Furthermore, in the above embodiment, the image forming apparatus 100 is a tandem type color image forming apparatus, but is not limited to this, and may be, for example, a black and white drum type image forming apparatus. [Explanation of symbols]

[0079] 3 Optical inspection equipment 31 Measurement object 4-sided light source 5 Optical Elements 51 Collimator lens 52 Beam Expander 6 Aperture member 61 Aperture 7 Receiver 100 Image forming device D Luminous flux width D1 Aperture diameter D2 Irradiation diameter L1 Axial length of aperture L2 optical path length M Toner mark (toner image) P Paper (recording medium)

Claims

1. An optical inspection device that irradiates a measurement object with light and receives reflected light, A surface light source, an optical element including a collimator lens that makes the light beam emitted from the surface light source closer to parallel light; an aperture member having an aperture for restricting the light beam passing through the collimator lens; a light receiver that receives reflected light from the object to be measured, the light beam having passed through the aperture, and obtains outputs at a plurality of positions; a diameter of the aperture is smaller than an effective diameter of an optical element of the optical element that is disposed closer to the surface light source than the aperture, An optical inspection device, wherein the axial length of the aperture is greater than the diameter of the aperture, and the shape of the aperture member near the tip is a conical portion so as to be parallel to the surface of the object to be measured.

2. The optical inspection device according to claim 1 , wherein the light receiver is composed of a plurality of photosensors.

3. The optical inspection device according to claim 1 , wherein the light receiver is a one-dimensional line sensor.

4. The optical inspection device according to claim 1 , wherein the light receiver is a two-dimensional area sensor.

5. The optical inspection device of claim 1 , wherein the optical inspection device is disposed within an image forming device.

6. 2. The optical inspection device according to claim 1, wherein the measurement object is a sheet-like recording medium.

7. 2. The optical inspection device according to claim 1, wherein the measurement object is a toner image on a sheet-like recording medium.

8. The optical inspection device according to claim 1 , wherein the aperture member is arranged closer to the object to be measured than the optical element arranged closest to the object to be measured among the optical elements.

9. 2. The optical inspection device according to claim 1, wherein an incident angle of light on an optical axis of the light beam irradiated onto the measurement object is set to 60 degrees.

10. 2. The optical inspection device according to claim 1, wherein the optical path length from the tip of the aperture to the object to be measured is set to 5 mm or less.

11. 11. The optical inspection device according to claim 9 or 10, wherein, when an irradiation diameter is defined as a maximum distance between outermost rays of the light beam irradiated onto the measurement object, the diameter of the aperture, the length of the aperture in the axial direction, the angle of incidence of the light beam irradiated onto the measurement object, and the optical path length to the measurement object are set so that the irradiation diameter is 5 mm or less.

12. The optical inspection device according to claim 1 , wherein the optical element includes a beam expander that is disposed between the collimator lens and the aperture member and that expands or reduces a beam diameter.

13. 13. The optical inspection device according to claim 12, wherein D / D1 is set to be 2 or more and 5 or less, where D1 is the diameter of the aperture and D is the light beam width on the end face of the aperture facing the surface light source.

14. 2. The optical inspection device according to claim 1, wherein the collimator lens has a numerical aperture NA of 0.5 or more.

15. An image forming apparatus comprising the optical inspection device according to claim 1.

Images