JP7005884B2 - Optical sensor, recording medium discrimination device, and image forming device - Google Patents

Description

The present invention relates to an optical sensor, a recording medium discrimination device, and an image forming device.

Some image forming devices that form an image on a recording medium using ink or toner use an optical sensor to detect the brand or surface condition of the recording medium. The optical sensor irradiates the recording medium with light linearly polarized from the irradiation system (S polarization), and the amount of change from S polarization to P polarization due to reflection on the recording medium is detected by the optical detector, and the polarization changes. There is a device that detects multiple diffused reflected light and internally diffused reflected light by receiving the component with a light detector (for example, Patent Document 1).

In an optical sensor, even if the light source unit is for irradiating linearly polarized light (S-polarized light), if the mounting method is such that stress acts directly on the light source unit, the polarization is in the opposite direction to the linearly polarized light (S-polarized light). The polarization ratio with the component (P-polarization) causes variation among individual sensors.
An object of the present invention is to reduce the variation in the polarization ratio on the light source side for each individual optical sensor.

In order to achieve the above object, the optical sensor according to the present invention emits linearly polarized light in the first polarization direction toward the surface of an object from an incident direction inclined with respect to the normal direction of the surface. The system and the linear polarization component in the second polarization direction, which is arranged on the optical path of the light diffusely reflected by the object in the incident plane of the object emitted from the irradiation system and is orthogonal to the first polarization direction, are separated. The irradiation system includes a light source unit including a light source that emits light , and a first light detector that receives a linear polarization component in a second polarization direction separated by the polarization optical element. It has a circuit board to which the light source unit is attached, and the light emission center of the light source unit, the illumination center of the light on the surface, and the center of the first light detector are each provided on the same plane, and the first light detector is provided. Can detect multiple diffused reflected light that is reflected multiple times on the surface of the object and whose polarization direction is rotated, and internal diffused reflected light that is reflected multiple times inside the object and whose polarization direction is rotated. Is fixed to the housing that holds the irradiation system, the first light detector, and the polarization optical element so as not to come into direct contact with the housing via the circuit board, and has a space in the light emission direction of the light source unit. The housing has a guide portion that regulates the rotation of the light source unit in the direction in which the light emitted from the light source unit and received by the first light detector is directed from the first polarization direction to the second polarization direction. The guide portion is characterized in that it is arranged along the circuit board and is arranged outside the fixed portion where the circuit board and the housing are fastened.

According to the present invention, the light source portion of the irradiation system is fixed to the housing holding the irradiation system, the photodetector, and the polarizing optical element via a space in the light emission direction of the light source portion. Therefore, it is possible to eliminate the direct stress on the light source portion and reduce the variation in the polarization ratio on the light source side for each optical sensor.

The figure explaining the schematic structure of the color printer which concerns on embodiment of this invention. The figure explaining the structure of the optical sensor which concerns on Embodiment 1 of this invention. The figure explaining the structure of the irradiation system and the housing of the optical sensor which concerns on Embodiment 1. FIG. The figure explaining the structure of the light source part. The figure explaining the general fixing structure of an irradiation system and a housing. The figure explaining the trouble by the fixed structure shown in FIG. The figure explaining the trouble by the fixed structure shown in FIG. The figure explaining the incident angle of the incident light to a recording medium. The figure explaining the arrangement of the 1st and 2nd photodetectors. The block diagram which shows the structure of the control system which concerns on this embodiment. The figure explaining the relationship between the output signal of the 1st and 2nd photodetectors and the brand of a recording medium. The flowchart which shows one Embodiment of the paper type discrimination process using the optical sensor which concerns on Embodiment 1. The enlarged view explaining the structure of the optical sensor which concerns on Embodiment 2 of this invention. The figure explaining the arrangement of the 1st to 4th photodetectors included in Embodiment 2. The flowchart which shows one Embodiment of the paper type discrimination process using the optical sensor which concerns on Embodiment 2. The schematic diagram for demonstrating the structure of the irradiation system of the optical sensor which concerns on Embodiment 3 of this invention. The schematic diagram for demonstrating the structure of the optical sensor which concerns on Embodiment 4 of this invention. The schematic diagram for demonstrating the structure of the optical sensor which concerns on Embodiment 5 of this invention. The figure explaining the housing shape of the modification 1 of the optical sensor which concerns on this invention. The figure explaining the fixed structure of the irradiation system of the modification 2 of the optical sensor which concerns on this invention. The figure for demonstrating the structure of the modification 3 of the optical sensor which concerns on this invention. The figure explaining the change of polarization by the reflection of a recording medium, and the classification of a reflection. The figure explaining the change of the polarization ratio by assembling the light source. The figure which shows the result of having measured the polarization ratio of the light emitted by a light source part. (A) and (b) are diagrams for explaining the insertion amount of the screw, and are diagrams showing the state at L = L1 in FIG. 24. (A) and (b) are diagrams for explaining the insertion amount of screws, and are diagrams showing the state of L> L1 in FIG. 24. The figure which showed the change of the output of the 1st photodetector and the 2nd photodetector in a paper brand. The figure which measured the variation of the output of the second photodetector by the optical sensor assembled under the same screw fastening condition.

Hereinafter, embodiments and modifications according to the present invention will be sequentially described with reference to the drawings. In each embodiment and modification, those having the same function and configuration are designated by the same reference numerals, and duplicate description will be omitted as appropriate. Drawings may be partially omitted to aid in understanding some configurations.

FIG. 1 shows a schematic configuration of a color printer 2000 as an embodiment of an image forming apparatus to which the present invention is applied. The color printer 2000 is a tandem multicolor printer that forms a full-color toner image by superimposing four colors (black, cyan, magenta, and yellow). The color printer 2000 includes an optical scanning device 2010, photoconductor drums (2030a, 2030b, 2030c, 2030d) as four image carriers, four cleaning units (2031a, 2031b, 2031c, 2031d), and four charging devices (2032a). , 2032b, 2032c, 2032d), four developing rollers as developer carriers (2033a, 2033b, 2033c, 2033d), transfer belts 2040 as transfer bodies wound around rollers as a plurality of rotation support members, 1, Transfer rollers (2041a, 2041b, 2041c, 2041d) as secondary transfer members, secondary transfer rollers 2042 as secondary transfer members, fixing device 2050, paper feed rollers 2054 and discharge rollers 2058 as medium feed members, storage tray 2060. It is equipped with a paper output tray 2070, a communication control device 2080, an optical sensor 2245, and a control means 2090 that collectively controls each of the above parts. The communication control device 2080 controls bidirectional communication with the host device 3000 (for example, a personal computer) via a network or the like.

The photoconductor drum 2030a, the charging device 2032a, the developing roller 2033a, and the cleaning unit 2031a are used as one unit to form an image forming station that forms a black image. The photoconductor drum 2030b, the charging device 2032b, the developing roller 2033b, and the cleaning unit 2031b are used as one unit to form an image forming station for forming a cyan image.
The photoconductor drum 2030c, the charging device 2032c, the developing roller 2033c, and the cleaning unit 2031c are used as one unit to form an image forming station for forming a magenta image. The photoconductor drum 2030d, the charging device 2032d, the developing roller 2033d, and the cleaning unit 2031d are used as one unit to form an image forming station that forms a yellow image.

A photosensitive layer is formed on the surface of each of the photoconductor drums (2030a, 2030b, 2030c, 2030d). That is, the surface of each photoconductor drum is the surface to be scanned. Each photoconductor drum (2030a, 2030b, 2030c, 2030d) is rotationally driven in the direction of the arrow in FIG. 1 by a drive source. Each charging device (2032a, 2032b, 2032c, 2032d) uniformly charges the surface of the corresponding photoconductor drum. The optical scanning device 2010 is charged with light modulated for each color based on multicolor image information (black image information, cyan image information, magenta image information, yellow image information) from the control means 2090. It scans the surface of each photoconductor drum.

As a result, a latent image corresponding to the image information is formed on the surface of each photoconductor drum (2030a, 2030b, 2030c, 2030d). The latent image formed here moves in the direction of the corresponding developing rollers (2033a, 2033b, 2033c, 2033d) with the rotation of the photoconductor drums (2030a, 2030b, 2030c, 2030d). As the developing rollers (2033a, 2033b, 2033c, 2033d) rotate, toner as a developer from the corresponding toner cartridge is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller (2033a, 2033b, 2033c, 2033d) comes into contact with the surface of the corresponding photoconductor drum, it migrates only to the portion of the surface irradiated with light and adheres to the surface. That is, each developing roller (2033a, 2033b, 2033c, 2033d) adheres toner to a latent image formed on the surface of the corresponding photoconductor drum (2030a, 2030b, 2030c, 2030d) to visualize it. Here, the image (toner image) to which the toner is attached moves in the direction of the transfer belt 2040 as the photoconductor drums (2030a, 2030b, 2030c, 2030d) rotate. The yellow, magenta, cyan, and black toner images are sequentially first transferred onto the transfer belt 2040 at the sites facing the transfer rollers (2041a, 2041b, 2041c, 2041d) and superposed to form a multicolored color image. Will be done.

Paper P is stored in the storage tray 2060. In the vicinity of the storage tray 2060, a paper feed roller 2054 for taking out the paper P from the storage tray 2060 one by one is arranged. The ejected paper P is fed by the resist roller pair 2056 toward the secondary transfer portion in the gap between the transfer belt 2040 and the secondary transfer roller 2042 at a predetermined timing. Then, the toner image on the transfer belt 2040 is transferred to the paper P at the secondary transfer unit and sent to the fixing device 2050.
In the fixing device 2050, heat and pressure are applied to the paper P, whereby the toner is fixed on the paper P. The fixed paper P is sent to the output tray 2070 via the discharge roller 2058, and is sequentially stacked on the output tray 2070.
Each cleaning unit (2031a, 2031b, 2031c, 2031d) removes post-transcriptional toner (residual toner) remaining on the surface of the corresponding photoconductor drum. The surface of the photoconductor drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

As described above, in the color printer 2000, the toner image is transferred to the surface Pa of the paper P which is a sheet-shaped recording medium typified by printing paper, and the image is heated and pressed by the fixing device 2050 under predetermined conditions. Is fixed to form an image. What must be considered in image formation is the image formation conditions such as the heating amount and pressure at the time of fixing, which is one example of the image formation conditions. In particular, in order to perform high quality image formation, the image formation conditions are set on paper. It is necessary to set individually according to the brand (type) of P. This is because the image quality of the paper P is greatly affected by its material, thickness, humidity, smoothness, coating condition, and the like. For example, with regard to smoothness, depending on the fixing conditions, the fixing rate of the toner in the recesses may be low due to the unevenness of the paper surface. Therefore, color unevenness will occur unless fixing is performed under the correct conditions according to the paper P.
Furthermore, with the progress of image forming devices and the diversification of expression methods in recent years, there are more than hundreds of types of paper P for printing paper alone, and each type has different specifications such as basis weight and thickness. There are a wide variety of brands. In the following, the most detailed classification of paper P including differences in specifications such as basis weight and thickness will be described as a brand, and the discrimination for specifying a brand will also be described as discrimination at the brand level. In order to form a high-quality image, it is necessary to set detailed image forming conditions according to each of these brands.
In recent years, the number of brands of recording media such as plain paper, gloss-coated paper, matte-coated paper, coated paper typified by art-coated paper, plastic sheets, and special paper with embossed surface has increased. There is.

The color printer 2000 includes an optical sensor 2245 that irradiates the paper P with light and receives the reflected light to optically detect the paper P. The optical sensor 2245 is used to identify the brand of paper P contained in the storage tray 2060. The optical sensor 2245 may be separately installed outside the storage tray 2060 as a single recording medium detecting means.

Here, the reflected light from the paper will be described with reference to FIG. 22. The reflected light can be considered separately as the reflected light reflected on the surface of the paper and the reflected light reflected inside the paper. The reflected light reflected on the surface of the paper is further reflected by the normal reflection, the reflected light reflected in the diffusion direction by one reflection, and the reflection reflected by the unevenness of the paper surface multiple times and reflected in the diffusion direction. It can be classified as light. Hereinafter, for convenience, each reflected light is also referred to as "normally reflected light", "diffuse reflected light", and "multiple diffuse reflected light". On the other hand, the reflected light reflected inside the paper (hereinafter also referred to as "internal diffuse reflected light"), when the paper is general printing paper, has many reflections at the interface between the fibers and holes inside the paper. Since it repeats several times, the reflection direction can be regarded as isotropic, and the intensity distribution can be approximated to the Lambert distribution. As a result, the reflected light from the paper can be classified into normal reflected light, diffused reflected light, multiple diffused reflected light and internally diffused reflected light.
The polarization directions of the specularly reflected light and the diffusely reflected light are the same as the polarization directions of the irradiation light. On the other hand, the multiple diffuse reflection light and the internal diffuse reflection light contain a polarization component orthogonal to the polarization direction of the irradiation light. Here, the polarization direction is rotated by the reflection on the paper when the irradiation light is reflected on the surface inclined in the direction of rotation with respect to the traveling direction.

The optical sensor for discriminating the paper brand disclosed in Patent Document 1 irradiates the paper with linearly polarized light (S-polarized light) and detects the amount of change from S-polarized light to P-polarized light due to reflection on the paper. .. By receiving the component whose polarization has changed, the above-mentioned multiple diffuse reflection light and internal diffuse reflection light are detected, and the magnitude thereof is used as a parameter for brand discrimination.
In the following, when the polarization that changes due to the reflection of the paper is referred to, the light to be irradiated is basically the S polarization, and the component changed by the reflection is described as the P polarization. However, as an embodiment of the optical sensor, an optical sensor may be configured such that the light to be irradiated is P-polarized and the S-polarized component changed by reflection is detected.

In an optical sensor for discriminating general paper, the polarization ratio of the light source is not high for cost reduction. Even a light source for irradiating linearly polarized light contains a polarizing component in the opposite direction. That is, the light source of the disclosed optical sensor also includes P-polarization, not a light source completely composed of S-polarization. Here, when the light from the light source contains a P-polarized component, the P derived from the light source is more than the polarized component that changes due to the reflection (multiple diffuse reflection or internal diffuse reflection) on the paper that is the object of discrimination. If the polarized component is detected as diffusely reflected light, it becomes difficult to distinguish it. Therefore, as a configuration for detecting the change in polarization, it is necessary to have a configuration that does not include the P polarization component derived from the light source as much as possible, for example, does not detect it in the detection direction near the specular reflection.
However, completely eliminating the P-polarization component derived from the light source to a level that cannot be detected by the optical sensor ultimately requires an increase in the polarization ratio of the light source, resulting in high cost. Therefore, in order to improve the accuracy, the optical sensor detects the P polarization component derived from the light source, while improving the reproducibility of the polarization ratio of the light source for each optical sensor. That is, if the reproducibility of the polarization ratio for each optical sensor is high, the discriminability is maintained. What should be avoided in the system for paper discrimination is the situation where the amount of P-polarization component derived from the light source is different for each optical sensor, and it is included in the output of the optical sensor that created the table and the optical sensor as a mass production machine. It suffices if the P polarization component derived from the light source is reproduced.
For this reason, the optical sensor is required to reduce the variation in the output of the optical sensor due to the difference in the polarization ratio.

There are three main factors that affect the polarization characteristics: stress on the light source, the amount of light emitted, and the certainty of the installation position in the optical system. Generally, in a light source such as a semiconductor laser, the polarization ratio changes when an external stress is applied to the light source element itself. As an example, as a means for the light source element to stabilize the polarization, a structure having a slit in one direction is provided near the laser emitting portion, and this structure is deformed by an external stress. This is because it will be stored.
Further, it is known that in a light source such as a semiconductor laser, there is a correlation between the amount of light emitted and the polarization ratio.
The polarization ratio also changes depending on the installation position in the optical system. This is due to an error in the assembly of the light source and other components that make up the optical sensor. The direction of the linear polarization of the light source is determined by the relative positional relationship with respect to the target plane to be irradiated, the polarization direction to be received by the light receiving element, and the like. For example, as shown in FIG. 22, when the light source is assembled with the light source shifted in the rotation direction of the light beam with respect to the design installation position, the object to be irradiated has more P than the characteristics of the light source alone. Polarization is included. FIG. 23A shows an example in which the light source is correctly installed and the target plane can be irradiated with linearly polarized light as S-polarized light only. FIG. 23B shows an example in which the light source is assembled so as to be displaced in the rotation direction of the light beam, and the linearly polarized light is irradiated to the target plane as P-polarized light.

In the optical sensor of the present embodiment, as an example, the P-polarized component contained in the diffusely reflected light when irradiated with S-polarized light is used as a means for discriminating the paper brand. That is, the P polarization component is a component whose polarization is changed for the first time due to reflection on the paper P, and is also an index showing the degree of scattering of light reflection on the paper P. That is, the P polarization component is information unique to the object necessary for discriminating the paper brand. However, due to the above factors, the polarization ratio of the optical sensor also varies, and the quality of the P polarization component derived from the light source is different for each optical sensor. This is because the photodetector detects the P-polarized component derived from the light source together with the P-polarized component due to the reflection by the paper P.

(Embodiment 1)
As shown in FIG. 2, the optical sensor 2245 according to the present embodiment is for maintaining the positional relationship between the irradiation system 100, the second photodetection system 101, the first photodetection system 102, the collimating lens 12, and these parts. It includes a housing 21 and a dark box 190 in which these are stored. The housing 21 and the dark box 190 may be common parts or separate parts.
The dark box 190 is a metal box member, for example, an aluminum box member, and has a black alumite treatment on the surface in order to reduce the influence of ambient light and stray light. The dark box 190 may be made of resin, and the material is not limited here. The dark box 190 is formed with an opening 191 for irradiating the surface Pa of the paper P, which is the surface of the object, with the irradiation light emitted from the irradiation system 100.
The irradiation system 100 emits linearly polarized light in the first polarization direction toward the surface Pa of the paper P from an incident direction inclined with respect to the normal direction of the surface Pa. The collimating lens 12 is ejected from the irradiation system 100 and fixedly arranged on the optical path (opening hole 21a) of light.
The housing 21 is formed with an opening hole 21a, an opening hole 21b, and an opening hole 21c that guide the light emitted from the irradiation system 100 to the opening 191. The opening hole 21b is a passage through which the light positively reflected by the surface Pa of the paper P passes through the opening 191. The opening hole 21c is a passage through which the light diffusely reflected by the surface Pa of the paper P in the incident surface of the paper P passes. It is a passage through. The collimating lens 12 is fixedly arranged in the housing 21 on the optical path (opening hole 21a) of the light emitted from the irradiation system 100.

The second photodetection system 101 is arranged on an optical path (opening hole 21b) of light emitted from the irradiation system 100 and specularly reflected by the surface Pa of the paper P, and receives the specularly reflected light. It has a light receiving element 15 as a device.
The first light detection system 102 is arranged on an optical path (opening hole 21c) of light diffusely reflected by the surface Pa of the paper P in the incident surface of the paper P, and is a second light orthogonal to the first polarization direction. A polarization filter 16 is provided as a polarization optical element that separates linear polarization components in the polarization direction. The first photodetection system 102 has a light receiving element 17 as a first photodetector that receives a linear polarization component in the second deflection direction separated by the polarizing filter 16. The polarizing filter 16 is fixedly arranged in the housing 21 on an optical path (opening hole 21c) of light diffusely reflected in the normal direction of the surface Pa of the paper P.
The processing unit 109 identifies the paper P based on the output signals from the light receiving element 15 and the light receiving element 17. In the present embodiment, since the optical sensor 2245 and the processing unit 109 are separated , the recording medium discrimination device 300 (see FIG. 2 ) is configured by the optical sensor 2245 and the processing unit 109. That is, the color printer 2000, which is an image forming apparatus, includes a recording medium discrimination apparatus 300.
The optical sensor 2245 and the processing unit 109 may not be arranged individually, but the processing unit 109 may be integrally arranged with the optical sensor 2245. In this case, the optical sensor 2245 having the processing unit 109 also serves as a recording medium discrimination member. In the present embodiment, the processing unit 109 is provided in the control means 2090.

In the XYZ three-dimensional Cartesian coordinate system shown in FIG. 2, the direction orthogonal to the surface Pa of the paper P will be described as the Z-axis direction, and the plane parallel to the surface Pa of the paper P will be described as the XY plane. Then, it is assumed that the optical sensor 2245 is arranged on the + Z side of the paper P as an example. In the following, the center of the illuminated area on the surface Pa of the paper P will be abbreviated as “illuminated center”. Further, the light passing through the collimating lens 12 is also referred to as "irradiation light".
By the way, when light is incident on the boundary surface of the paper P, the surface including the incident light ray and the normal of the boundary surface set at the incident point is called an “incident surface”. In the following, the direction parallel to the incident light ray will be described as the X'axis direction, and the direction orthogonal to the incident light ray will be described as the Z'axis direction in the incident plane. Further, in the embodiment, the expressions S-polarized and P-polarized are used not only for the incident light on the paper P but also for the reflected light. This is an expression based on the polarization direction of the incident light on the paper P for convenience of explanation, and the same polarization direction as the incident light (S polarization in this embodiment) in the incident plane is S-polarized and orthogonal to it. The direction of polarization is referred to as P polarization. In the embodiment, the light emission direction of the light source unit is the X'axis direction, and the light emission direction axis of the light source unit is the X'axis.

In the present embodiment, as shown in FIG. 3, the irradiation system 100 includes a light source unit 111 that emits light and a circuit board 112 to which the light source unit 111 is attached. The optical sensor 2245 is connected to the control means 2090, which is a control unit for controlling the light source unit 111, via the circuit board 112. In the present embodiment, the control means 2090 has a function as a control unit, but a control unit that controls the light source unit 111 may be provided separately from the control means 2090.
The light source unit 111 is attached to and arranged in the housing 21 so as to face one end of the opening hole 21a formed in the housing 21. The light source unit 111 includes a package 115 and a light source 116 mounted on the package 115. In the present embodiment, the light source 116 is a vertical cavity type surface emitting laser (VCSEL) array, and as shown in FIG. 4, a plurality of light sources 116 formed on the same (one) substrate. It has a light emitting unit 111A of. In the light source 116 shown in FIG. 4, nine light emitting units 111A are two-dimensionally arranged on the same substrate, and an electrode pad 113 is connected to each light emitting unit 111A. When the light source 116 has a plurality of light emitting units 111A such as a VCSEL array, a speckle peculiar to the case where an object such as paper P causing diffuse reflection is irradiated with a semiconductor laser beam having a long coherence distance. It is possible to reduce the variation in the sensor output depending on the pattern. Although the case where the light source 116 of the light source unit 111 includes a VCSEL array having nine light emitting units 111A is described here, the present invention is not limited to this.

In a general irradiation system 100, as shown in FIG. 5, in order to improve the accuracy of the distance between the light source unit 111 and the collimating lens 12, the portion of the housing 21 in which the light source unit 111 is opened by the opening hole 21a (this In many cases, the position is determined by contacting the bottom portion 211a1) located in the X'axis direction in the embodiment. However, in this mounting method, as shown in FIG. 6, a gap S may occur between the housing 21 and the circuit board 112 within the range of the height tolerance of the housing 21 and the light source unit 111. If the light source unit 111 is fixed to the housing 21 with the gap S generated, the light source unit 111 is sandwiched between the bottom portion 211a1 and the circuit board 112 as shown in FIG. 7, and the light source unit 111 is used as a fulcrum. The stress F from the circuit board 112 is applied to the light source unit 111. When the stress F is applied, the polarization ratio changes, which causes a decrease in discrimination accuracy. The generation of such stress F is the same not only in the case where the light source unit 111 and the circuit board 112 are individually configured, but also in the case of one light source unit in which the light source unit 111 and the circuit board 112 are integrated. Is.
For this reason, a general optical sensor is a sensor that uses the change in polarization due to the reflection of the paper P as a parameter for discrimination, and in particular, when performing subdivided discrimination such as discriminating up to a brand, the above-mentioned It is necessary to consider and reduce the individual difference in the polarization of the light source unit 111 as described above.

As shown in FIG. 3, the irradiation system 100 in the present embodiment is arranged with respect to the housing 21 by being fastened and fixed by a fastening member 114 such as a screw via a circuit board 112. The light source unit 111 is attached to the circuit board 112 so as to project in the light emission direction (X'axis direction). When fixing the irradiation system 100 to the housing 21, the light source unit 111 has dimensions and a circuit so as to be non-contact with the housing 21 when the circuit board 112 and the housing 21 come into contact with each other. The positional relationship with the substrate 112 is set . That is, in the optical sensor 2245, the light source unit 111 is fixed to the housing 21 holding the irradiation system 100, the first photodetection system 102, and the second photodetection system 101 via the circuit board 112 without directly contacting the light source unit 111. There is.
Therefore, when the light source unit 111 is fixed to the housing 21, stress is directly applied to the light source unit 111, and it is possible to reduce the change in the polarization ratio of the light source unit 111.

Further, the housing 21 has a structure in which the contact area with the circuit board 112 is only around the fastening and fixing portion 213 between the circuit board 112 and the housing 21, and the contact area area is small within a range in which stable holding is possible. ing. That is, in the present embodiment, in order to avoid a change in the polarization ratio of the light source unit 111, the light source unit 111 is not sandwiched between the light source unit 111 and the housing 21 due to the shape error of the housing 21, and the stress F is not applied. .. That is, the housing 21 is formed with a plurality of boss portions 210 that serve as fixing portions for fixing the light source portion 111, and a recess 211 for accommodating the light source portion 111. The recess 211 is recessed in the light emission direction (X'axis direction) of the light source unit 111. An opening hole 21a is opened in the bottom portion 211a of the recess 211. The distance S1 from the bottom portion 211a to the mounting surface 210a of the boss portion 210 to which the circuit board 112 is fixed is the surface 111a located in the light emission direction (X'axis direction) of the light source unit 111 from the mounting surface 111b of the light source unit 111. It is formed to be larger than the height (protrusion amount) S2 up to. Therefore, when the circuit board 112 to which the light source portion 111 is attached is fixed to the attachment surface 210a of the boss portion 210, a space S1a is formed between the surface 111a of the light source portion 111 and the bottom portion 211a of the housing 21. That is, the light source unit 111 emits light to the housing 21 that holds the irradiation system 100, the polarizing filter 16, and the light receiving element 17 so as not to be sandwiched between the housing 21 in the light emission direction (X'axis direction) of the light source unit 111. It is fixed to the housing 21 in the direction (X'axis direction) via the space S1a.

FIG. 25 (b) shows a configuration in which the end face 115a of the package 115 shown in FIG. 25 (a) and the housing 21 are not in contact with each other and the circuit board 112 on which the package 115 is mounted and the housing 21 are in contact with each other. Using the configuration in which the end face 115a of the package 115 of the light source unit 111 and the housing 21 are in contact with each other, the change in the polarization ratio of the light emitted by the light source unit 111 during the fastening process of the screw 114 was measured. FIG. 24 shows the measurement result. The stress on the light source element 116 was changed by the rotation speed (insertion amount L) of the screw 114 to be fastened.
From this result, it can be confirmed that the polarization ratio changes significantly only in the configuration on the side shown in FIG. 25 (b) where the end face 115a of the package 115 and the housing 21 are in contact with each other. In FIG. 24, the change can be confirmed from the screw position (the position where the circuit board 112 starts to bend) at which stress starts to be generated with respect to the package 115. 25 (a), 25 (b), 26 (a), and 26 (b) are diagrams for explaining the screw insertion amount L in the above two configurations. 25 (a) and 25 (b) show the state of L = L1 in FIG. 24, FIG. 26 (a) and FIG. 26 (b) show the state of L> L1 in FIG. 24.

From the above, the light source portion 111 does not come into pressure contact with the bottom portion 211a and is not subjected to stress F. Therefore, it is possible to eliminate the direct stress F on the light source unit 111 (irradiation system 100) and reduce the variation in the polarization ratio of the optical sensor 2245 for each individual.
As the configuration of the light source unit, the light source unit in which the light source unit 111 and the circuit board 112 are integrated may be used. Even in this case, the surface 111a of the light source unit 111 does not come into close contact with the bottom portion 211a of the housing 21, and the light of the light source unit 111 is not sandwiched between the housing 21 in the light emission direction (X'axis direction) of the light source unit 111. It is fixed to the housing 21 via the space S1a in the injection direction (X'axis direction). As a result, the stress F is not received, and the variation in the polarization ratio of each individual optical sensor can be reduced.

Here, in a configuration in which the end surface 115a of the package 115 and the housing 21 are in contact with each other, stress is applied by fastening screws in the same manner as in the measurement of FIG. 24, and the reflected light is measured on a plurality of sheets P. The measurement position of the paper P in this measurement is the same position. FIG. 27 shows changes in the outputs of the first photodetector and the second photodetector during measurement. Here, the first photodetector is a detector that detects specular reflection, and the second photodetector is a detector that includes a polarization filter and detects a change component of polarization. 27 (a) shows the output change of the first photodetector, and FIG. 27 (b) shows the output change of the second photodetector. The configuration measured in FIG. 27 is the configuration of FIG.
The line segments shown in FIGS. 27 (a) and 27 (b) are the results of the measured paper brands. In the photodetector (second photodetector) that detects the change in polarization, as shown in FIG. 27 (b), it can be confirmed that the influence of the change in the polarization ratio due to stress is remarkable. Although it depends on the paper brand, a change of about 0 to 5% was observed in this experiment. On the other hand, in the photodetector (first photodetector) that detects specular reflection, as shown in FIG. 27 (a), the change is not so much seen. From this, it can be said that the stress on the light source element 116 is particularly sensitive to the light detection related to the polarization in the reflection on the paper P.
That is, the output of the second photodetector varies, and when the object is discriminated more finely, especially the brand, the brands having similar reflection characteristics may be erroneously discriminated. Therefore, in the present embodiment, the end face 115a of the package 115 and the housing 21 do not come into contact with each other, but the circuit board 112 on which the package 115 is mounted and the housing 21 come into contact with each other, reducing the variation in the polarization ratio for each individual optical sensor. I'm letting you.
Therefore, the identification of the paper brand by the optical sensor in the present embodiment is performed by collating with the value of the database prepared in advance. The database is the output of each photodetector measured by the photosensor, which is the prototype, but if the screw insertion amount L becomes an error factor and the output of the second photodetector varies from optical sensor to optical sensor. , Invites you to make a mistake in the paper brand.
FIG. 28 is an optical sensor (12 units in each configuration) assembled under the same screw fastening conditions, and measures the variation in the output of the second photodetector. In this measurement, the same place on the same paper was measured, and the standardized value was shown for the average value of 12 units for each configuration. As described above, the configuration in which the package 115 and the housing 21 according to the present invention are not in contact with each other has an effect of reducing the variation in the output of the second photodetector (individual sensor difference). Therefore, according to the present embodiment, it is possible to stably determine the paper brand.

The fixing method of the light source unit 111 (irradiation system 100) is not limited to the fastening and fixing by the fastening member 114, and may be, for example, an adhesive fixing method using a UV curable resin or the like. Even in this case, the circuit board 112 may be adhesively fixed to each boss portion 210. The reference numeral A1 in FIG. 3 indicates the fixing pitch of the fastening fixing portion 213 by the fastening member 114.

As shown in FIG. 8, the irradiation system 100 is arranged so that linearly polarized S-polarized light is emitted from the light source unit 111 with respect to the paper P. The collimating lens 12 is arranged on the optical path (21a) of the light emitted from the light source unit 111, and the light is made substantially parallel light. The light passing through the collimating lens 12 passes through the opening 191 provided in the dark box 190 and illuminates the surface Pa of the paper P at the position facing the opening 191. In FIG. 8, the incident angle θ of the light of the light source unit 111 (irradiation system 100) on the paper P is 80 °. Here, as shown in FIG. 9, the light receiving element 15 is arranged on the + X side of the illumination center in the X -axis direction. The angle ψ1 formed by the line L1 connecting the center of illumination and the center of the light receiving element 15 and the surface Pa of the paper P is 170 °. The light emitting center, the illumination center, the center of the polarizing filter 16, the center of the light receiving element 17, and the center of the light receiving element 15 of the light source unit 111 exist on substantially the same plane. Further, the angle ψ2 formed by the line L2 connecting the center of illumination and the centers of the polarizing filter 16 and the light receiving element 17 and the surface Pa of the paper P is 150 °. In FIGS. 8 and 9, the configuration of the housing 21 is omitted.

In the present embodiment, since the light emitting center, the lighting center, and the center of the light receiving element 17 of the light source unit 111 of the irradiation system 100 are substantially on the same plane, diffuse reflection is reflected once on the surface Pa of the paper P and the polarization direction is rotated. The light is not detected by the light receiving element 17. On the other hand, the multiple diffused reflected light that is reflected multiple times on the surface Pa of the paper P and the polarization direction is rotated, and the internal diffused reflected light that is reflected multiple times inside the paper P and the polarization direction is rotated are the above planes in the reflection path. After deviating from, the light reflected on this plane is included again by being reflected multiple times. Therefore, the multiple diffuse reflected light and the internal diffuse reflected light are also detected by the light receiving element 17 which is on the same plane as the emission center of the light source unit 111 of the irradiation system 100 and the illumination center.

Diffuse reflected light, multiple diffuse reflected light, and internally diffuse reflected light are incident on the polarizing filter 16. Here, since the polarization direction of the diffusely reflected light is the same S polarization as the polarization direction of the irradiation light, the diffusely reflected light is shielded (shielded) by the polarizing filter 16. On the other hand, the polarization directions of the multiple diffuse reflection light, the internal diffuse reflection light and the background reflected light are rotated with respect to the polarization direction of the irradiation light. Therefore, the P-polarized component contained in the multiple diffuse reflected light and the internal diffuse reflected light passes through the polarizing filter 16. That is, the light receiving element 17 receives only the P polarization component contained in the multiple diffuse reflection light and the internal diffuse reflection.
For convenience, the P-polarized component contained in the internally diffuse reflected light is also referred to as "P-polarized component of the internally diffuse reflected light". Further, the S-polarized component contained in the internally diffuse reflected light is also referred to as "the S-polarized component of the internally diffuse reflected light". The inventors have confirmed that the amount of internally diffuse reflected light correlates with the thickness and density of the paper P. This is because the amount of internally diffuse reflected light depends on the path length when passing through the fibers of the paper P.

Next, the configuration of the control means 2090 will be described. As shown in FIG. 10, the control means 2090 is a CPU 2091, a ROM 2092 in which a program described by a code decodable by the CPU 2091 and various data used when executing the program are stored, and a working memory. It has a RAM 2093, an amplifier circuit 2094, an A / D conversion circuit 2095 that converts an analog signal into a digital signal, and the like. The control means 2090 controls each part of the color printer 2000 in response to the request from the higher-level device 3000 described in FIG. 1, and sends the image information from the higher-level device 3000 to the optical scanning device 2010 to control the image forming operation. ..
The control means 2090 includes a processing unit 109 that identifies a brand of paper P as a recording medium according to the signal level of the output signal from the optical sensor 2245. The processing unit 109 is mainly composed of the CPU 2091 and the ROM 2092.
The light receiving element 15 and the light receiving element 17 output an electric signal (photoelectric conversion signal) corresponding to the amount of received light to the processing unit 109. The value output to the processing unit 109 may be an average value of electric signals for a certain period of time (hereinafter referred to as sampling time).

In the present embodiment, the signal level in the output signal of the light receiving element 15 when the light flux from the irradiation system 100 is applied to the paper P is referred to as “S01”, and the signal level in the output signal of the light receiving element 17 is referred to as “S02”. ..
The control means 2090 having the processing unit 109 is based on the output signal “S01” of the light receiving element 15 and the output signal “S02” of the light receiving element 17 when the light flux from the irradiation system 100 is applied to the paper P. Estimate (specify) the brand of P. Here, with respect to the paper P of a plurality of brands that the color printer 2000 can handle, the values of S01 and S02 are measured in advance for each brand of the paper P in the pre-shipment process such as the adjustment process, and the measurement result is referred to as "paper P discrimination table". It is stored in ROM 2092 of the control means 2090.

FIG. 11 shows the measured values of S01 and S02 for 30 brands of paper P sold in Japan. The square frame shown by the broken line in FIG. 11 indicates the variation range of the same brand. For example, if the measured values of S01 and S02 are "◇", the processing unit 109 identifies the brand D. If the measured values of S01 and S02 are "■", the processing unit 109 identifies the brand C as the closest. If the measured values of S01 and S02 are "◆", it is estimated by the processing unit 109 to be either brand A or brand B. At this time, for example, the difference between the average value and the measured value of the brand A and the difference between the average value and the measured value of the brand B are calculated by the control means 2090, and the issue with the smaller calculation result is processed. Specified by part 109. Further, the control means 2090 recalculates the variation including the measured value assuming that it is the brand A, and recalculates the variation including the measured value assuming that it is the brand B. Then, the brand with the smaller recalculated variation may be selected by the processing unit 109.

By the way, when the power of the color printer 2000 is turned on, the paper P is supplied to the storage tray 2060, and the like, the control means 2090 determines the paper type of the paper P by the output signal from the optical sensor 2245 and the processing unit 109. Perform processing. The paper type discrimination process performed by the control means 2090 will be described with reference to the flowchart shown in FIG. In the paper type discrimination process by the processing unit 109 of the control means 2090 using the optical sensor 2245, in step ST1 of FIG. 12, a plurality of light emitting units 111A of the optical sensor 2245 are made to emit light. In the paper type discrimination process, in step ST2, the values of the signal levels S01 and S02 are obtained from the output signals of the light receiving element 15 and the light receiving element 17. In the paper type discriminating process, in step ST3, the paper discriminating table stored in ROM 2092 is referred to, and the brand of paper P is specified from the obtained values of S01 and S02. In the paper type discrimination process, in step ST4, the brand of the specified paper P is stored in the RAM 2093, and the paper type discrimination process is terminated. That is, the processing unit 109 (control means 2090) according to the first embodiment identifies the paper P based on the signal levels of the output signals of the light receiving elements 17 and 15 which are the first and second photodetectors.

Upon receiving the print job request from the user, the control means 2090 reads out the brand of the paper P stored in the RAM 2093, and sets the development conditions and the transfer conditions, which are examples of the optimum image forming conditions for the brand of the paper P, into the ROM 2092. Obtained from the development / transfer table stored in. Then, the control means 2090 controls the developing device and the transfer device of the image station of each color in the case of color printing according to the optimum developing conditions and transfer conditions. For example, the transfer voltage and the amount of toner are controlled. As a result, a high quality image is formed on the paper P. That is, the color printer 2000 includes a control means 2090 that functions as an adjustment device that adjusts image formation conditions according to the paper P as an object specified by the recording medium discrimination device 300. Further, the control means 2090, which is an adjusting device, has a function of identifying a brand of paper P based on the signal level of the output signal of the optical sensor 2245 and adjusting image forming conditions according to the identified brand. ..

(Embodiment 2)
Due to the influence of ambient light and stray light, it is assumed that the paper type will be erroneously determined.
Therefore, in this embodiment, as shown in FIG. 13, the number of photodetection systems is increased with respect to the configuration of the first embodiment. The optical sensor 2245A shown in FIG. 13 includes a third photodetection system 103 and a fourth photodetection system 104 in the configuration of the optical sensor 2245 including two light receiving elements 15 and 17. The third photodetector system 103 includes a light receiving element 18 as a third photodetector. The fourth photodetector system 104 includes a polarizing filter 19 as a polarizing optical element and a light receiving element 20 as a fourth photodetector. That is, the optical sensor 2245A according to the second embodiment includes the first to fourth photodetection systems 101 to 104.
In the optical sensor 2245A, the opening holes 21a to 21c and the opening holes 21d and 21e are formed in the housing 21. The opening hole 21d is a passage through which light diffusely reflected by the surface Pa of the paper P passes in the incident surface of the paper P, and the opening hole 21e is diffusely reflected by the surface Pa of the paper P in the incident surface of the paper P. It is a passage through which light passes.
The light receiving element 18 is arranged on the optical path (opening hole 21d) of the light diffusely and reflected by the paper P in the incident surface of the paper P. The light receiving element 18 is arranged at a position where it receives surface diffuse reflection light, multiple diffuse reflection, and internal diffuse reflection light.
The polarizing filter 19 is arranged on the optical path (opening hole 21e) of the light diffusely reflected by the paper P in the incident surface of the paper P, and the light receiving element 20 is arranged on the optical path (opening hole 21e) of the same light. The polarizing filter 19 receives the separated light. Like the polarizing filter 16, the polarizing filter 19 is installed so as to transmit P-polarized light, and the light receiving element 20 is arranged at a position where it receives multiple diffuse reflection and internal diffuse reflection light.

In the present embodiment, in the optical sensor 2245A, the center of the light emitting unit 111 of the irradiation system 100, the center of illumination, the center of the polarizing filter 19, and the center of the light receiving element 18 and the light receiving element 20 are substantially on the same plane. exist. As shown in FIG. 14, the angle ψ3 formed by the line L3 connecting the center of illumination and the center of the light receiving element 18 and the surface Pa of the paper P is 120 °. Further, the angle ψ4 formed by the line L4 connecting the center of illumination and the center of the light receiving element 20 and the surface Pa of the paper P is 90 °.

Next, the paper type discrimination process performed by the processing unit 109 of the output signal from the optical sensor 2245A and the control means 2090 will be described below. When the light from the irradiation system 100 is applied to the paper P, the signal level in the output signal of the light receiving element 18 amplified by the amplifier circuit 2094 of the control means 2090 described with reference to FIG. 10 is set to "S03". The signal level in the output signal of 20 is called "S04". Further, in the present embodiment, the light receiving element 18 and the light receiving element 20 are provided at a position closer to the illumination center than the light receiving element 17 so that S03 and S04 have substantially the same size as S02, and the captured light angle is reflected. Is larger than the capture angle of the reflected light by the light receiving element 17. It is not always necessary to make the output signal levels of all the photodetectors equal. For example, when the output signal of the light receiving element 15 which is the second photodetector for detecting the positively reflected light is amplified by another amplifier circuit 2094, the first photodetector, the third photodetector, and the fourth photo The output signal levels of the light receiving elements 17, 18 and 20 which are detectors may be made equal. The processing unit 109 (control means 2090) according to the second embodiment is based on the signal levels of the output signals of the light receiving elements 17, 15, 18, and 20, which are the first, second, third, and fourth photodetectors. And specify the paper P.

In the paper type discrimination process by the processing unit 109 of the control means 2090 using the optical sensor 2245A, in step ST11 shown in FIG. 15, a plurality of light emitting units 111A of the optical sensor 2245 are simultaneously made to emit light. In the paper type discrimination process, in step ST12, the values of the signal levels S01 to S04 are obtained from the output signals of the light receiving elements 15, 17, 18, and 20. In the paper type discriminating process, in step ST13, the paper discriminating table stored in ROM 2092 is referred to, and the brand of paper P is specified from the obtained values of S01, S02, S03, and S04. In the paper type discrimination process, in step ST14, the brand of the specified paper P is stored in the RAM 2093, and the paper type discrimination process is terminated. In this case, regarding the paper P of a plurality of brands that the color printer 2000 can handle, the values of S01, S02, S03, and S04 are measured in advance for each brand of the paper P in the pre-shipment process such as the adjustment process, and the measurement result is ". It may be stored in ROM 2092 of the control means 2090 as a "paper P discrimination table".

In this way, a plurality of first to fourth photodetection systems 101 to 104 (light receiving elements 17, 15, 18, 20 and deflection filters 16, 19) for detecting light reflected in different directions are provided. By discriminating the paper P using the output level of the output signal, which is the detection value of each of the light receiving elements 15, 17, 18, and 20, it is possible to accurately discriminate even if there is ambient light or stray light.
In the case of the configuration including the first to fourth plurality of photodetection systems 101 to 104, the control means 2090 roughly narrows down the paper types using the signal levels S01 and S02, and the signal levels S03 and S04. May be used to specify the brand of paper P. In this way, a plurality of photodetection systems (light receiving elements 15, 17, 18, 20 and deflection filters 16, 19) for detecting light reflected in different directions are provided, and the light receiving elements 15, 17, 18, respectively. By discriminating the paper P using the output level of the output signal at 20, accurate discrimination can be performed even if there is ambient light or stray light.
In the present embodiment, the configuration including the third and fourth photodetection systems 103 and 104 as the photodetection system has been described, but the optical sensor 2245 described in the first embodiment has the third photodetection system 103. It may be an optical sensor provided with three photodetection systems in which the above is added.

(Embodiment 3)
As shown in FIG. 16, the optical sensor 2245B according to the present embodiment is provided with a fifth light detection system 105 for confirming the amount of light emitted by the light emitting unit 111A in the light source unit 111. The fifth photodetection system 105 has a beam splitter 23 as an optical element arranged immediately after the light emitting unit 111A and separating a part of the irradiation light, and a fifth photodetector for receiving the separated light by the beam splitter 23. It has a light receiving element 22 of the above. The light receiving element 22 and the beam splitter 23 are installed in the light source unit 111. In this embodiment, the signal level in the output signal of the light receiving element 22 is referred to as "S05".
The fifth photodetection system 105 needs to be installed in the front portion of the opening hole 21a of the housing 21 in the optical path in order to confirm the light emission amount of the light emitting unit 111A. This is because when the fifth photodetection system 105 is arranged behind the opening hole 21a of the housing 21 in the optical path, the amount of light detected by the light receiving element 22 passes through the opening hole 21a of the total luminous flux of the irradiation light. This is because it is the amount of light of the luminous flux and is different from the amount of light emitted by the light emitting unit itself. That is, in the present embodiment, the irradiation light amount and the light emission amount of the light emitting unit 111A are different.

In the present embodiment, the processing unit 109 (control means 2090) adjusts the amount of light emitted from the light emitting unit 111A equally based on S05 so that the polarization ratio of the irradiation light for each optical sensor does not vary. In this case, the amount of light emitted to the paper P varies from optical sensor to optical sensor due to the reason for the opening hole 21a. Therefore, when specifying the brand of the paper P, the processing unit 109 uses the signal levels S01 / S05, S02 / S05, S03 / S05, and S04 / S05 obtained as examples, which are normalized by the amount of light emitted. Make a determination. That is, the processing unit 109 (control means 2090) according to the third embodiment is the light receiving elements 17, 15, 18, 20, and 22 which are the first, second, third, fourth, and fifth photodetectors. The paper P is specified based on the signal level of the output signal. Further, in the present embodiment, the processing unit 109 controls the light emitting unit 111A to keep the light emitting amount at a predetermined amount based on S05, which is the signal level of the output signal of the light receiving element 22.
In this way, by keeping the amount of light emitted by the light emitting unit 111A constant, it is possible to avoid the existence of an individual having a reduced polarization ratio depending on the individual optical sensor, and by extension, more accurate discrimination becomes possible.

(Embodiment 4)
As shown in FIG. 17, the optical sensor 2245C according to the present embodiment has a rotation direction indicated by an arrow B about the X'axis of the light source unit 111 and the circuit board 112 in the housing 21 as a configuration of the irradiation system 100. It is provided with guide units 212A and 212B for regulating the above. The guide portions 212A and 212B are arranged outside the fastening and fixing portion 213 between the circuit board 112 and the housing 21.
By providing the guide portions 212A and 212B in this way, it is possible to reduce the variation in the installation position in the rotation direction B about the X'axis. As a result, for the reason described with reference to FIG. 22, it is possible to avoid the existence of an individual having a reduced polarization ratio depending on the individual optical sensor, and by extension, more accurate discrimination becomes possible. In this modification, an example is shown in which the guide portions 212A and 212B on two sides parallel to the Z'axis are provided in the housing 21, but the shape is limited to this shape as long as the rotation direction can be specified. It's not a thing.
Further, in the present embodiment, the surface 111b of the light source unit 111 located in the light emission direction (X'axis direction) of the light source unit 111 is arranged in the opening 21a. In the present embodiment, the circuit board 112 is fixed to the housing 21 so as to form a space S1b between the surface 112a of the circuit board 112 located in the light emission direction and the bottom portion 211a of the recess 211. That is, when the light source unit 111 and the circuit board 112 have different configurations , the space in the light emission direction is the space S1c in the opening 21a, and the light source unit and the circuit board are integrally configured. The space in the light emission direction is the space S1a2.
In this way, depending on the size of the light source portion 111 and the opening 21a, the surface 111b may be arranged in the opening 21a and fixed to the housing 21 so that the surface 112a of the circuit board 112 and the bottom portion 211a do not come into contact with each other. F is not received, and the variation in the polarization ratio of each individual optical sensor can be reduced.

(Embodiment 5)
In the first to fourth embodiments, the processing unit 109 has been described as being installed outside each optical sensor 2245 to 2245C, but the optical sensor 2245D according to the present embodiment is an optical sensor 2245D as shown in FIG. It is equipped with a processing unit 109. In this case, the installation location of the processing unit 109 includes the dark box 190, but is not limited to the dark box 190.
It is preferable that the optical sensor 2245D itself includes the processing unit 109 because the processing load of the control means 2090 can be reduced and the recording medium discrimination device can be configured by the optical sensor 2245D alone.
In the first to fifth embodiments, the housing 21 does not block the center of the optical path of the irradiation light.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to such a specific embodiment, and unless otherwise specified in the above description, the present invention described in the claims. Various modifications and changes are possible within the scope of the above.

(Modification 1)
In the modified example 1 shown in FIG. 19, the irradiation system 100 is fixed to the housing 21 via the circuit board 112 at a position far from the light source unit 111 within a range that can be installed. That is, in the present embodiment, the width C of the recess 211 that intersects the light emitting direction from the light source portion 111 is made larger than that of the first embodiment, and the fixing pitch of the fastening fixing portion 213 by the fastening member 114 represented by the reference numeral A2. Is wider than the fixed pitch A1 of the first embodiment. This is because the stress F applied to the light source unit 111 corresponds to the moment of the force applied for fixing. As a result, it is possible to avoid the existence of an individual having a reduced polarization ratio depending on the individual optical sensor due to the stress F described above, and by extension, more accurate discrimination becomes possible.

(Modification 2)
In each embodiment, the case where the fastening and fixing portions 213 of the housing 21 and the circuit board 112 are held at four places has been described, but the housing 21 and the circuit board 112 are held at a small number of places within a range where the positional relationship can be maintained. Is desirable. This is because stress applied to the circuit board 112 and the light source unit 111 is generated depending on the shape error of the contact portion, and the error factor is omitted. For example, in order to hold the flat circuit board 112, it is desirable to hold it at three points as shown in FIG. 20, and the fastening and fixing portions 213 of the housing 21 and the circuit board 112 may be held at three places.

(Modification 3)
In each embodiment, a condenser lens, which is at least one optical element, may be provided in front of each light receiving element (on the incident side). FIG. 21 shows a modified example in which the condenser lenses 171 and 172 are arranged in front (incident side) of the light receiving elements 15 and 17 constituting the optical sensor 2245 described in the first embodiment.
When the condenser lenses 171 and 172 are arranged in front of the light receiving elements 15 and 17 (on the incident side) in this way, it is possible to reduce the variation in measurement at the signal level of the output signal. The reproducibility of the measurement is important for the optical sensor that discriminates the paper P based on the amount of reflected light. The optical sensor is installed on the premise that the measurement surface and the surface Pa of the paper P are in the same plane at the time of measurement. However, the surface Pa of the paper P may be inclined or lifted with respect to the measurement surface due to bending , vibration, or the like, and the surface Pa of the paper P may not be flush with the measurement surface. This causes a change in the light intensity distribution of the reflected light and changes in the amount of received light, so that it is difficult to make a detailed determination in a stable manner. Therefore, by arranging a condensing lens in front of each light receiving element, the amount of received light can be stabilized even if the light intensity distribution of the reflected light changes.
Of course, the configuration in which the condenser lens, which is at least one optical element, is provided in front of the light receiving element (incident side) is equivalent to the application to the first embodiment by applying to the configurations of the second to fourth embodiments. The effect can be obtained.

By using a photodiode (PD) having a sufficiently large light receiving area for each light receiving element or by narrowing the beam diameter of the irradiation light, the inconvenience when the surface Pa of the paper P is not flush with the measurement surface is solved. be able to.
A photodiode in which the light receiving region is arrayed may be used for each light receiving element, and the light receiving region may have a sufficiently large light receiving region with respect to the shift amount of the reflected light intensity distribution as a whole. In this case, even if the light intensity distribution of the reflected light is shifted, the output level of each light receiving element can be stabilized by using the maximum signal among the signals detected by each photodiode. In addition, when a plurality of photodiodes are arrayed, by reducing the light receiving area of each photodiode, the fluctuation of the output due to the deviation of the center of the incident light and the light receiving area can be reduced, so that more accurate detection can be performed. It can be carried out.

The relationship between the amount of specularly reflected light of S-polarization and the amount of specularly reflected light of P-polarization and the smoothness, thickness, and basis weight of the target paper P is obtained in advance and stored in ROM 2092 of the control means 2090 as a database. I will do it. Then, with reference to this database, the smoothness, thickness, and basis weight of the paper P, which is the object, are specified based on the output signals (signal levels) of the optical sensors 2245, 2245A, 2245B, 2245C, and 2245D. Image formation conditions may be adjusted according to the specified smoothness, thickness and basis weight.

In each embodiment, the case where there is one storage tray 2060 has been described, but the present invention is not limited to this, and there may be a plurality of storage trays 2060. In this case, it is preferable to provide optical sensors having the same configuration for each storage tray.

In each embodiment, each optical sensor is arranged in the vicinity of the storage tray 2060, and the brand of the paper P stored in the storage tray 2060 is specified by each optical sensor. The issue identification time is not limited to such a form.
As an example , the brand of the paper P may be specified during the transportation of the paper P. In this case, the optical sensors 2245, 2245A, 2245B, 2245C, and 2245D are arranged in the vicinity of the paper transport path. Specifically, the optical sensor 2245 is arranged in the transport path between the paper feed roller 2054 and the secondary transfer roller 2042, and the paper P transported toward the secondary transfer portion is irradiated with light from the optical sensor 2245. Then, there is a configuration for specifying the brand.
Further , the brand of the paper P may be specified before the paper P is filled in the storage tray 2060. In this case, each optical sensor is installed outside the color printer 2000. Specifically , each optical sensor may be placed on the upper surface of the exterior of the color printer 2000 , and the optical sensor can be easily held by an operator like a handy scanner and can be detached from the color printer 2000. , When specifying the brand of paper P, each optical sensor may be held by hand to specify the brand of paper P.

In each embodiment, the object specified (estimated and identified) by the optical sensors 2245, 2245A, 2245B, 2245C, and 2245D has been described as paper P as an example of a recording medium, but is not limited to paper P. do not have.

In each embodiment, the color printer 2000 has been described as an example of the image forming apparatus, but the form of the image forming apparatus is not limited to this. For example, it may be a laser printer that forms a monochrome image. Further, an image forming apparatus other than a printer, for example, a copying machine, a facsimile, or a multifunction device in which these are integrated may be used.
In each embodiment, the case where the color printer 2000 having four photoconductor drums (2030a, 2030b, 2030c, 2030d) is used as the image carrier has been described, but the present invention is not limited to such an embodiment. For example, a color printer having five photoconductor drums as an image carrier may be used.
In each embodiment, the intermediate transfer type image forming apparatus in which the toner image is transferred from the photoconductor drums 2030a, 2030b, 2030c, and 2030d to the paper P via the transfer belt 2040 has been described, but the present invention is limited to such an embodiment. It is not something that will be done. For example, a monochrome or color image forming apparatus in which the toner image is directly transferred from the photoconductor drum to the paper P may be used.
In each embodiment, the optical sensors 2245, 2245A, 2245B, 2245C, and 2245D are applied to an electrophotographic image forming apparatus that forms an image using a toner image on paper P, but the image forming apparatus to be applied is applied. The image forming apparatus may be an image forming apparatus that forms an image by spraying ink on the paper P.

The effects described in each of the embodiments and modifications of the present invention are merely a list of the most suitable effects resulting from the present invention, and the effects according to the present invention are described in the embodiments of the present invention. It is not limited to things.

12 Collimated lens 15 Second photodetector (light receiving element)
16 Polarized optical element (polarizing filter)
17 First photodetector (light receiving element)
18 Third photodetector (light receiving element)
19 Polarized optical element (polarizing filter)
20 4th photodetector (light receiving element)
21 Housing 21b-21e Optical path 22 Fifth photodetector (light receiving element)
23 Optical element (beam splitter)
101 2nd light detection system 102 1st light detection system 103 3rd light detection system 104 4th light detection system 105 5th light detection system 109 Processing unit 100 Irradiation system 111 Light source unit 111A Multiple light emitting units 112 Circuit board 115 Package 116 Light source 151, 171 Optical element 190 Dark box 212A, 212B Guide unit 300 Recording medium discrimination device 2000 Image forming device 2010 Optical scanning device 2090 Adjustment device (printer control device)
2245 (A, B, C) Optical sensor 2245D Optical sensor, recording medium discrimination device B Rotational direction of light source F Stress P Object, recording medium Pa Surface of object, incident surface (surface of recording medium)
S01 to S05 Signal level of the output signal of the photodetector S1a1, S1a2, S1a3 Space X'Light emission direction of the light source

Japanese Unexamined Patent Publication No. 2012-127937

Claims (18)

An irradiation system that emits linearly polarized light in the first polarization direction toward the surface of the object from an incident direction inclined with respect to the normal direction of the surface.
Within the incident plane of the object ejected from the irradiation system, it is arranged on the optical path of the light diffusely reflected by the object and separates the linear polarization component in the second polarization direction orthogonal to the first polarization direction. It is provided with a polarizing optical element for receiving light, and a first light detector that receives a linear polarization component in the second polarization direction separated by the polarizing optical element.
The irradiation system has a light source unit including a light source that emits light, and a circuit board to which the light source unit is attached.
The light emission center of the light source unit, the illumination center of the light on the surface, and the center of the first photodetector are provided on the same plane.
The first light detector includes multiple diffuse reflected light that is reflected multiple times on the surface of the object and whose polarization direction is rotated, and internal diffuse reflected light that is reflected multiple times inside the object and whose polarization direction is rotated. Can be detected,
The light source unit is fixed to the housing holding the irradiation system, the first photodetector, and the polarization optical element so as not to come into direct contact with the housing via the circuit board, and the light source unit of the light source unit. It has a space in the direction of light emission,
The housing regulates the rotation of the light source unit in the direction in which the light emitted from the light source unit and received by the first photodetector is directed from the first polarization direction to the second polarization direction. Has a guide section
The guide portion is an optical sensor arranged along the circuit board and outside the fixed portion where the circuit board and the housing are fastened. The optical sensor according to claim 1, further comprising a second photodetector, which is arranged on an optical path of light emitted from the irradiation system and specularly reflected by the object, and receives the specularly reflected light. The optical sensor according to claim 1 or 2, wherein the light source has a plurality of light emitting units. The optical sensor according to any one of claims 1 to 3, wherein the light source unit includes a package on which the light source is mounted. The optical sensor according to any one of claims 1 to 4, wherein the polarized optical element is arranged on an optical path of light diffusely reflected in the normal direction of the surface of the object. It comprises at least one third light detector arranged on the optical path of the light diffusely reflected by the object in the incident plane of the object, and the third light detector is from the first light detector. The optical sensor according to any one of claims 1 to 5 , wherein the third light detector is provided at a position close to the illumination center and can detect the multiple diffused reflected light and the internally diffused reflected light . At least one optical element, which is arranged on the optical path of light diffusely reflected by the object and separates linear polarization in the second polarization direction in the incident plane of the object, and the at least one optical element. The fourth light detector is provided at a position closer to the illumination center than the first light detector, and the fourth light detector is provided with at least one fourth light detector that receives the separated light. The optical sensor according to any one of claims 1 to 6, which can detect the multiple diffused reflected light and the internally diffused reflected light . In the optical path of the light emitted by the irradiation system, an optical element arranged immediately after the light source portion to separate a part of the irradiation light and a fifth photodetector for receiving the separated light by the optical element are provided. The optical sensor according to any one of claims 1 to 7. The optical sensor according to claim 2, further comprising a processing unit for identifying the object based on the output signals of the first photodetector and the second photodetector. The optical sensor according to claim 6, further comprising a processing unit that identifies the object based on the output signals of the first, second, and third photodetectors. The optical sensor according to claim 7, further comprising a processing unit that identifies the object based on the output signals of the first, second, third, and fourth photodetectors. The optical sensor according to claim 8, further comprising a processing unit that identifies the object based on the output signals of the first, second, third, fourth, and fifth photodetectors. The optical sensor according to claim 12, wherein the processing unit controls the light emission amount of the light source unit to be maintained at a specified amount based on the output signal of the fifth photodetector. A recording medium discrimination device including an optical sensor and a processing unit that identifies an object based on an output signal from the optical sensor.
The recording medium discriminating device in which the optical sensor is the optical sensor according to any one of claims 1 to 8. A recording medium discriminating device including the optical sensor according to at least any one of claims 9 to 13. In an image forming apparatus that forms an image on a recording medium,
The image forming apparatus provided with the recording medium discriminating device according to claim 14 or 15, wherein the recording medium is an object. The image forming apparatus according to claim 16, further comprising an adjusting device for adjusting image forming conditions according to an object specified by the recording medium discriminating device. The image forming apparatus according to claim 17, wherein the adjusting device identifies a brand of the recording medium based on a signal level of an output signal of the optical sensor, and adjusts image forming conditions according to the specified brand.

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