JP2016148521A - Optical sensor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: since a conventional optical sensor determines an object and its brand by referring to a recording sheet determination table including the size of reflection light to be received measured in advance as representative values of respective brands, an incident angle needs to be easily and accurately set, but an error in the incident angle is not taken into consideration.SOLUTION: An optical sensor of the present invention comprises: an irradiation part that irradiates a surface of an object with light having an angle with respect to a normal line of the surface and can change the angle; and a light detection part that detects light emitted from the irradiation part and reflected on the object and outputs a signal, and sets the angle on the basis of the signal output from the light detection part.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical sensor and an image forming apparatus.

  There is known an optical method for irradiating a recording medium with light and receiving reflected light or transmitted light to detect the brand or surface state of the recording medium.

  For example, Patent Document 1 discloses a recording material discriminating apparatus that discriminates the type of recording material using reflected light and transmitted light.

  Patent Document 2 discloses an optical sensor that identifies the brand of recording paper from the amount of P-polarized light component contained in the internally diffuse reflected light and the amount of surface regular reflected light.

  Patent Document 3 discloses an optical sensor that identifies a brand of recording paper from the amount of light in an approximately regular reflection direction of irradiated light with an incident angle of 80 deg.

  However, the techniques disclosed in Patent Documents 1 to 3 do not consider the setting of the incident angle.

  Therefore, an object of the present invention is to provide an optical sensor capable of easily and accurately setting an incident angle.

  In the optical sensor of the present invention, in order to solve the above-described problem, light having an angle with respect to a normal line of the surface is emitted toward the surface of the object, and the irradiation unit capable of changing the angle; and A light detection unit that detects light reflected from the object and outputs a signal, and sets the angle based on the output signal.

  According to the optical sensor of the present invention, the incident angle can be easily and accurately set.

1 is a schematic configuration diagram of a color printer according to an embodiment of the present invention. It is a block diagram of the optical sensor which concerns on one Embodiment of this invention. It is a figure which shows the printer control apparatus which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the incident angle which concerns on one Embodiment of this invention, and the output from a light receiver. It is a figure which shows the light source which concerns on one Embodiment of this invention. It is a figure which shows the shift | offset | difference of the incident angle which concerns on one Embodiment of this invention. It is a figure which shows the positional relationship of the irradiation part which concerns on one Embodiment of this invention, a light receiver, and a polarizing filter. It is a figure which shows the classification | category of the reflected light from a paper when the paper which concerns on one Embodiment of this invention is irradiated. It is a figure which shows the measured value of S01 and S02 about the recording paper of 30 brands sold in the country which concerns on one Embodiment of this invention. It is a figure which shows the printer control apparatus which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the light emission part which concerns on one Embodiment of this invention, and the output from a light receiver. It is a flowchart figure which shows the procedure which selects the selective light emission part which concerns on one Embodiment of this invention. It is a figure which shows the light source which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the number of light emission parts which concerns on one Embodiment of this invention, and the contrast ratio of a speckle pattern. It is a block diagram of the optical sensor which concerns on one Embodiment of this invention. It is a block diagram of the optical sensor which concerns on one Embodiment of this invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration of a color printer 2000 according to an embodiment. The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow). 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), four developing rollers (2033a, 2033b, 2033c, 2033d), transfer A belt 2040, a transfer roller 2042, a fixing device 2050, a paper feed roller 2054, a paper discharge roller 2058, a paper feed tray 2060, a paper discharge tray 2070, a communication control device 2080, an optical sensor 2245, and a program for comprehensively controlling the above-described units. And a like printer controller 2090. The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The printer control device 2090 includes a CPU, a ROM that stores a program written in code readable by the CPU, various data used when the program is executed, a RAM that is a working memory, an amplifier circuit And an A / D conversion circuit for converting an analog signal into a digital signal. The printer control device 2090 controls each unit in response to a request from the host device, and sends image information from the host device to the optical scanning device 2010.

  Although FIG. 1 shows an example in which the printer control device 2090 is installed outside the optical sensor 2245, the optical sensor 2245 itself may include the printer control device 2090.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, and the cleaning unit 2031a are used as a set, and constitute an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, and the cleaning unit 2031b are used as a set, and constitute an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, and the cleaning unit 2031c are used as a set, and constitute an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, and the cleaning unit 2031d are used as a set, and constitute an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is a surface to be scanned. Each photosensitive drum is rotated in the direction of the arrow in the plane of FIG. 1 by a rotation mechanism (not shown). Each charging device uniformly charges the surface of the corresponding photosensitive drum. The optical scanning device 2010 is correspondingly charged with light modulated for each color based on multi-color image information (black image information, cyan image information, magenta image information, yellow image information) from the printer control device 2090. Each surface of the photosensitive drum is scanned.

  Thereby, a latent image corresponding to the image information is formed on the surface of each photosensitive drum. The latent image formed here moves in the direction of the corresponding developing roller as the photosensitive drum rotates. As each developing roller rotates, toner from a corresponding toner cartridge (not shown) is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface and adheres to the surface. In other words, each developing roller causes toner to adhere to the latent image formed on the surface of the corresponding photosensitive drum so as to be visualized. Here, the toner-attached image (toner image) moves in the direction of the transfer belt 2040 as the photosensitive drum rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are superimposed to form a multicolor image.

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060. The paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060. The recording paper is sent out toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the toner image on the transfer belt 2040 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing device 2050.

  In the fixing device 2050, heat and pressure are applied to the recording paper, thereby fixing the toner on the recording paper. The recording paper fixed here is sent to a paper discharge tray 2070 via a paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070. Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

  By the way, in an image forming apparatus such as a digital copying machine or a laser printer, a toner image is transferred onto the surface of a sheet-like recording medium represented by printing paper, and the image is fixed by heating and pressing under predetermined conditions. Image. Conditions that must be taken into consideration in image formation are conditions such as the heating amount and pressure during fixing, and in particular, in order to perform high-quality image formation, it is necessary to individually set printing conditions according to the recording medium.

  This is because the image quality on the recording medium is greatly influenced by the material, thickness, humidity, smoothness, coating state, and the like. For example, with regard to smoothness, depending on the fixing conditions, the toner fixing rate for the concave portions in the unevenness on the surface of the printing paper is lowered. Therefore, color unevenness occurs unless fixing is performed under the correct conditions according to the recording medium.

  Furthermore, with recent advances in image forming devices and diversification of expression methods, there are hundreds of types of recording media, even on printing paper alone, and there are differences in specifications such as basis weight and thickness for each type. There are a wide variety of brands. In the following description, the most detailed classification of paper including differences in specifications such as basis weight and thickness is also referred to as brand and discrimination for identifying brand is also referred to as discrimination at the brand level. In order to form a high quality image, it is necessary to set fine printing conditions according to each of these brands.

  In recent years, the brands of plain paper, gloss coated paper, mat coated paper, coated paper typified by art coated paper, plastic sheets, and special paper with an embossed surface are increasing.

  In the conventional image forming apparatus, when the paper is filled in the paper feed tray, the user himself / herself has to set the paper brand for each tray in the control unit. For this reason, there are problems such as inconvenience that must be set by the user and setting mistakes because the user is required to have knowledge for identifying the brand of the paper. In addition, when the brand of the paper to be printed is unknown, there is a problem that it is not known which brand is suitable for setting.

  Therefore, the color printer 2000 includes the optical sensor 2245 as described above.

  The optical sensor 2245 is used to specify the brand of recording paper stored in the paper feed tray 2060 as an example. Note that the optical sensor 2245 may be separately installed outside the paper feed tray 2060 as a single measuring device.

  FIG. 2 is a diagram illustrating an example of the optical sensor 2245. The optical sensor 2245 includes an irradiation unit 11, two light receivers (15, 17), a polarizing filter 16, and a dark box 190 in which these are stored. The irradiation unit 11 includes a light source 13 and a collimating lens 18, and the two light receivers (15, 17) are connected to a printer control device 2090 that is a control unit.

  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.

  Here, in the XYZ three-dimensional orthogonal coordinate system, the direction orthogonal to the surface of the recording paper 12 is described as the Z-axis direction, and the plane parallel to the surface of the recording paper 12 is described as the XY plane. The optical sensor 2245 is assumed to be disposed on the + Z side of the recording paper 12 as an example.

  In the following, the center of the illumination area on the surface of the recording paper 12 is abbreviated as “illumination center”. The light that has passed through the collimating lens 18 is also referred to as “irradiation light”.

  Further, when light is incident on the boundary surface of the medium, a surface including the incident light beam and the normal of the boundary surface set up at the incident point is called an “incident surface”. In the following description, in the incident plane, the direction parallel to the incident light beam is defined as the X′-axis direction, and the direction orthogonal to the incident light beam is defined as the Z′-axis direction.

  In the following description, expressions such as S-polarized light and P-polarized light are used for reflected light as well as incident light on the recording paper. For convenience of explanation, this is the polarization direction of incident light on the recording paper. In the incident plane, the same polarization direction as the incident light (S-polarized light in the present embodiment) is called S-polarized light, and the polarization direction orthogonal thereto is called P-polarized light.

  3 shows an example of the printer control device 2090. The printer control device 2090 includes the storage memory 19, and FIG. 4 is a diagram showing the relationship between the incident angle and the output of the light receiver 15. As shown in FIG. Here, the incident angle is an angle formed by the incident light from the irradiation unit and the normal direction (Z axis) of the recording paper 12.

  As shown in FIG. 4, the incident angle from the irradiation unit 11 can be changed to a to e, and the output of the light receiver 15 is different for each incident angle a to e.

  In FIG. 4, since the output of the light receiver 15 at the incident angle b is closest to the output signal set value 20, the incident angle of the irradiation unit 11 is set to b. The output signal set value 20 is an output level corresponding to the set incident angle of 80 degrees, and is stored in advance in the storage memory 19 shown in FIG. 3, and the set incident angle b is also stored in the storage memory 19.

  Since the output of the vertical axis and the light receiver is usually amplified by a circuit using an operational amplifier or the like, the absolute amount depends on the amplification factor. There is no meaning as a number, and the above shows an example.

  FIG. 5 shows an example of the light source 13. Here, the light source 13 has a plurality of light emitting portions 14 (P1 to P5) formed on the same substrate. Here, for each light emitting portion of the light source 13, a vertical cavity surface emitting laser (VCSEL) or the like is used. Each light emitting portion of the light source 13 is connected to the electrode pad 27 through the wiring member 26. The light source 13 shown here includes a surface emitting laser array (VCSEL array). The light emitting unit of the light source 13 includes five light emitting units arranged on a substantially straight line with respect to the Z′-axis direction, and each light emitting unit is wired so that it can emit light independently. The light source 13 is arranged so that S-polarized linearly polarized light is emitted from the recording paper. The collimating lens 18 is disposed on the optical path of the light emitted from the light source 13 and makes the light substantially parallel light. Light passing through the collimating lens 18 passes through an opening 191 provided in the dark box 190 and illuminates the recording paper.

  FIG. 6 shows an example of the incident angle deviation. Here, the incident angle θ of the light from the light source 13 to the recording paper is 80 °. If the incident angle is deviated, the reflectance on the recording paper changes and the determination is wrong. Therefore, the definition of the incident angle is very important. The deviation of the incident angle is different for each light source.

  This occurs due to the positional relationship between the center of the light emitting unit and the center of the collimating lens 18. FIG. 7 shows an example of the positional relationship among the irradiation unit 11, the light receivers 15 and 17, and the polarizing filter 16.

  Here, as shown in FIG. 7, the light receiver 15 is disposed on the + X side of the illumination center in the X-axis direction. The angle ψ1 formed between the line L1 connecting the illumination center and the center of the light receiver 15 and the surface of the recording paper is 170 °. The center of the selective light emitting unit of the light source 13, the center of illumination, the center of the polarizing filter 16, the center of the light receiver 17, and the center of the light receiver 15 are present on substantially the same plane. The angle ψ2 formed by the line L2 connecting the illumination center and the centers of the polarizing filter 16 and the light receiver 17 and the surface of the recording paper is 90 °. That is, the line L2 coincides with the normal line of the recording paper surface at the center of illumination.

  FIG. 8 shows classification of reflected light from the paper when the paper is irradiated. Reflected light from the paper when the paper is illuminated can be divided into reflected light reflected by the surface of the paper and reflected light reflected inside the paper. The reflected light reflected on the surface of the paper is further reflected regularly, reflected light reflected in the diffusion direction by a single reflection, and reflected light reflected in the diffusion direction after being reflected multiple times by the irregularities on the paper surface. Can be classified. Hereinafter, for convenience, each reflected light is also referred to as “regular 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”) is reflected many times at the interface between the fibers and pores inside the paper when the paper is general printing paper. Since it is repeated once, the reflection direction can be regarded as isotropic, and the intensity distribution can be approximated to a Lambertian distribution. As a result, the reflected light from the paper can be classified into regular reflected light, diffuse reflected light, multiple diffuse reflected light, and internal diffuse reflected light. The polarization direction of the regular reflection light and the diffuse reflection light is the same as the polarization direction of the irradiation light. On the other hand, the multiple diffuse reflection light and the internal diffuse reflection light include a polarization component orthogonal to the polarization direction of the irradiation light. Here, the polarization direction is rotated by reflection on the paper when the irradiation light is reflected by a surface inclined in the direction of rotation with respect to the traveling direction.

  In the present embodiment, since the center of the selective light emitting unit of the light source 13, the center of illumination, and the center of the light receiver 17 are substantially on the same plane, 17 is not detected. On the other hand, multi-diffuse reflected light that has been reflected several times on the paper surface and whose polarization direction has been rotated, and internal diffuse reflected light that has been reflected several times inside the paper and whose polarization direction has been rotated, are separated from the plane by the reflection path and then multiple times. Since it includes light reflected again on this plane by reflection, it is also detected by the light receiver 17 on the same plane as the center of the light source 13 and the illumination center.

  The polarizing filter 16 receives diffuse reflection light, multiple diffuse reflection light, and internal diffuse reflection light. Here, since the polarization direction of the diffuse reflected light is the same S polarization as the polarization direction of the irradiation light, the diffuse reflected light is shielded (shielded) by the polarizing filter 16. On the other hand, since the polarization direction of the multiple diffuse reflection light and the internal diffuse reflection light is rotated with respect to the polarization direction of the irradiation light, the P polarization component included in the multiple diffuse reflection light and the internal diffuse reflection light is a polarization filter. 16 is transmitted. That is, the light receiver 17 receives only the multiple diffuse reflection light and the P polarization component included in the internal diffuse reflection.

  Hereinafter, for convenience, the P-polarized component included 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 “S-polarized component of the internally diffuse reflected light”.

  It has been confirmed by the inventors that the amount of internal diffuse reflected light has a correlation with the thickness and density of the recording paper. This is because the amount of the internal diffuse reflected light depends on the path length when passing through the fibers of the recording paper.

  The light receivers 15 and 17 output an electrical signal (photoelectric conversion signal) corresponding to the amount of received light to the printer control device 2090 that is a sheet specifying unit (see FIG. 2). Note that the value output to the printer control device 2090 may be an average value of electrical signals for a certain period of time (hereinafter referred to as sampling time).

  Hereinafter, the signal level in the output signal of the light receiver 15 when the light beam from the light source 13 is irradiated on the paper is referred to as “S01”, and the signal level in the output signal of the light receiver 17 is referred to as “S02”. The printer control device 2090 estimates (specifies) the brand of the paper based on the output signal “S01” of the light receiver 15 and the output signal “S02” of the light receiver 17 when the light flux from the light source 13 is irradiated onto the paper. . Here, regarding a plurality of brands of recording paper that can be handled by the color printer 2000, the values of S01 and S02 are measured in advance for each brand of the recording paper in a pre-shipment process such as an adjustment process, and the measurement result is displayed as a “recording paper discrimination table”. Is stored in the ROM of the printer control device 2090.

  FIG. 9 shows the measured values of S01 and S02 for 30 brands of recording paper sold in the country. In addition, the frame in FIG. 9 shows the variation range of the same brand. For example, if the measured value of S01 and S02 is “◇”, it is identified as a brand D. Further, if the measured values of S01 and S02 are “■”, the closest brand C is identified.

If the measured values of S01 and S02 are “♦”, it is 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, and the calculation result is specified as the smaller brand. In addition, the variation including the measurement value is recalculated on the assumption that it is the brand A, and the variation including the measurement value is recalculated on the assumption that it is the brand B, and the recalculated variation is small. You may choose the other brand.
By the way, the printer control device 2090 performs a paper type discrimination process of the recording paper when the color printer 2000 is turned on or when the recording paper is supplied to the paper feed tray 2060. The paper type discrimination process performed by the printer controller 2090 will be described below.

(1) The light emitting unit of the optical sensor 2245 is caused to emit light.
(2) The values of S01 and S02 are obtained from the output signals of the light receiver 15 and the light receiver 17.
(3) With reference to the recording paper discrimination table, the brand of the recording paper is specified from the obtained values of S01 and S02.
(4) The brand of the specified recording paper is stored in the RAM, and the paper type discrimination process is terminated.

  Upon receiving a print job request from the user, the printer control device 2090 reads the recording paper brand stored in the RAM, and obtains the development conditions and transfer conditions optimum for the recording paper brand from the development / transfer table. . Then, the printer control device 2090 controls the developing device and the transfer device at each station in accordance with the optimum development conditions and transfer conditions. For example, the transfer voltage and the toner amount are controlled. Thereby, a high quality image is formed on the recording paper.

  In order to accurately detect the S-polarized component of the internally diffuse reflected light, it is preferable that the following two light receiving conditions are further satisfied.

  (1) The detection of the S-polarized component contained in the internally diffuse reflected light is not performed at least in the direction in which the surface regular reflected light is included.

  This is because, in practice, it is difficult to completely irradiate the irradiation light with only the S-polarized light, and the reflected light on the surface also includes the P-polarized light component. For this reason, in the direction in which the surface regular reflection light is included, the P-polarized component incident on the polarization filter 16 increases. Then, it is difficult to completely separate the polarized light with the polarizing filter 16, and a part of the P-polarized component is transmitted according to the extinction ratio.

  Therefore, if the polarizing filter 16 and the light receiver 17 are arranged in the direction in which the surface regular reflection light is included, the light receiver 17 detects the amount of light including the P-polarized component and detects information inside the recording paper. It is impossible to detect the S-polarized component of the internal diffuse reflected light necessary for the detection with high accuracy. By the way, in order to completely separate only one polarization component from incident light, it may be possible to use a polarization filter having a high extinction ratio, but this leads to an increase in cost.

  (2) The detection of the internal diffuse reflected light is performed in the normal direction of the illumination center in the recording paper.

  This is because the internal diffuse reflection light can be regarded as complete diffuse reflection, so that the reflected light amount with respect to the detection direction can be approximated by a Lambertian distribution, and the reflected light amount is the largest in the normal direction of the illumination center. When the polarizing filter 16 and the light receiver 17 are arranged on the optical path of the light reflected in the normal direction of the illumination center, the S / N is high and the accuracy is the highest.

  FIG. 10 shows, as an example of the printer control device 2090, a printer control device 2090 having a storage memory 19 and a light emitting unit selecting unit 21 that selectively emits light from the light emitting unit.

  Here, among the light emitting units 14 shown in FIG. 5, a light emitting unit that emits light is selected by the light emitting unit selecting means 21 (hereinafter, the light emitting unit selected to emit light by the printer control device 2090 is selected as the selected light emitting unit). ).

  FIG. 11 is a diagram showing the relationship between the plurality of light emitting units 14 and the outputs from the light receiver 15. The light source 13 includes a plurality of light emitting units 14 (P1 to P5) as shown in FIG. 5, and the output of each light emitting unit and the output from the light receiver 15 are as shown in FIG. In this case, the light emitting unit P2 that is closest to the output signal set value 20 is the selective light emitting unit.

  Moreover, the output of the light emission part 14 (R1-R2) of another light source 13 and the output from the light receiver 15 are shown as an example of the difference between individual sensors. In this case, the light emitting part R4 that is closest to the output signal set value 20 is the selective light emitting part.

  FIG. 12 is a flowchart showing an example of a procedure for selecting a selected light emitting unit by the printer control device 2090 shown in FIG. 10 from a plurality of light emitting units 14 (P1 to P5) of the light source 13 shown in FIG.

  As shown in FIG. 12, the procedure for selecting the light emitting unit is as follows: (1) Assemble components such as the light source 13 to the sensor body, (2) Install a sample (glass plate) on the measurement surface, (3) In the processing unit Send a measurement start signal to a certain printer control device 2090 (some signal from a switch or the like) (4) The printer control device 2090 receives a measurement start signal and starts to emit light (initially all light sources are turned off) (5) The printer control device 2090 causes the light emitting unit 1 to emit light (6) The printer control device 2090 records the output level (P1) of the light receiving unit in the memory (7) the printer control device 2090 turns off the light emitting unit 1 (8) The printer control device 2090 causes the light emitting unit 2 to emit light. (9) The printer control device 2090 records the output level (P2) of the light receiving unit in the memory. (10) Printer control. The device 2090 turns off the light emitting unit 2 (hereinafter, P1 to P5 are acquired in the same manner until the light emitting unit 5 turns off) (11) Equivalent to an incident angle of 80 degrees recorded in the memory in advance by the printer control device 2090 The closest output level is specified from P1 to P5 with respect to the output level at that time (12) At the time of paper measurement, the sample is recorded in the printer controller 2090 so as to use the light emitting unit having the closest output level (13). As a result, the appropriate light emitting unit 14 is selected.

  By the way, if the light emitting unit recorded in the printer control device 2090 as the selected light emitting unit does not emit light for some reason, or if a failure such as a significant decrease in the amount of light emitted occurs, the selected light emitting unit is adjacent to the light emitting unit. The printer control device 2090 may switch to the unit (the other light emitting unit closest to the output signal set value). Note that the printer control device 2090 may switch the selected light emitting unit to the adjacent light emitting unit when the irradiation light quantity changes due to an environmental change such as a temperature change in addition to the failure.

  FIG. 13 shows a second embodiment of the present invention. As shown in FIG. 13, the light emitting part of the light source 13 may be composed of a plurality of VCSELs (hereinafter also referred to as light emitting points). This is because the speckle pattern can be suppressed when the selective light emitting unit is composed of a plurality of VCSELs.

  The speckle pattern suppression method will be described below. In order to improve the S / N in a sensor that discriminates printing paper from the amount of reflected light at the brand level, it is preferable to use a semiconductor laser as a light source. In this case, coherent light emitted from the semiconductor laser is recorded. A speckle pattern is generated by irregular reflection at each point of a rough surface such as the surface of paper and interference with each other. Since the speckle pattern varies depending on the light irradiation site, it causes variations in the amount of received light in the light receiver, leading to a decrease in identification accuracy. Therefore, conventionally, an LED or the like has been generally used as a light source.

  The inventors used a vertical cavity surface emitting laser array (VCSEL array) in which a plurality of light emitting portions are two-dimensionally arranged as a light source, and obtained a relationship between the number of light emitting portions and the contrast ratio of the speckle pattern (see FIG. 14). Here, a value obtained by standardizing the difference between the maximum value and the minimum value in the observation intensity of the speckle pattern is defined as the contrast ratio of the speckle pattern. Hereinafter, for convenience, the contrast ratio of the speckle pattern is also simply referred to as “contrast ratio”.

  The speckle pattern was observed using a beam profiler in the diffusion direction, and the contrast ratio was calculated from the observation results obtained by the beam profiler. Three types of plain paper (plain paper A, plain paper B, plain paper C) and glossy paper having different smoothnesses were used as samples. Plain paper A is plain paper with Oken-type smoothness of 33 seconds, plain paper B is plain paper with Oken-style smoothness of 50 seconds, and plain paper C has Oken-style smoothness of 100. It is plain paper for seconds.

  In the present embodiment, each of the five light emitting units of the light source 13 of the optical sensor 2245 includes four light emitting points. Here, the light emitting points of the selective light emitting units emit light simultaneously. As described above, here, the selected light emitting unit is selected as one light emitting unit that is closest to the specified incident angle (80 deg) when the position is adjusted at the time of shipment. As a result, the speckle pattern is suppressed, and an accurate amount of reflected light can be detected. Further, the recording paper identification accuracy can be increased.

  In addition, when incident light consists of a several light ray, there will exist an incident surface for every light ray, but here, for convenience, the board | substrate plane (YZ 'plane) which started from the center of the light emission point of a selective light emission part The incident surface with the normal to the incident ray is referred to as the incident surface on the recording paper.

  That is, the paper type determination process performed by the printer control apparatus 2090 may be as follows as an example.

(1) The light emitting unit of the optical sensor 2245 is caused to emit light.
(2) The values of S01 and S02 are obtained from the output signals of the light receiver 15 and the light receiver 17.
(3) When the value of S02 is 20 or more, the process proceeds to the brand identification process of (4) below, and when the value of S02 is smaller than 20, the processing unit switches the selected light emitting unit to the adjacent light emitting unit. Returning to the light emission of the light emitting part (1).
(4) With reference to the recording paper discrimination table, the brand of the recording paper is specified from the obtained values S01 and S02.
(5) The brand of the specified recording paper is stored in the RAM, and the paper type discrimination process is terminated.

  As the failure determination method described above, determination may be made by comparing with a range of representative values on the recording sheet determination table, for example, the values of S01 and S02 are nearly zero.

  By the way, when there is a risk of erroneous paper type discrimination due to disturbance light or stray light, the number of light detection systems may be increased.

  For example, as shown in FIG. 15, a light receiver 23 may be provided as the third light detection system, and a polarizing filter 24 and a light receiver 25 may be further provided as the fourth light detection system. The light receiver 23 is disposed at a position for receiving surface diffuse reflection light, multiple diffuse reflection, and internal diffuse reflection light. Like the polarizing filter 16, the polarizing filter 24 is installed in a direction that transmits P-polarized light, and the light receiver 25 is disposed at a position for receiving multiple diffuse reflections and internal diffuse reflection light. The center of the selective light emitting unit of the light source 13, the center of illumination, the center of the polarizing filter 24, and the centers of the light receiver 23 and the light receiver 25 are present on substantially the same plane. The angle ψ3 formed by the line L3 connecting the illumination center and the center of the light receiver 23 and the surface of the recording paper is 120 ° (see FIG. 16). The angle ψ4 formed by the line L4 connecting the illumination center and the center of the light receiver 25 and the surface of the recording paper is 150 ° (see FIG. 16).

  In this case, a paper type determination process performed by the printer control apparatus 2090 will be described below. In the following description, the signal level in the output signal of the light receiver 23 amplified by the amplifier circuit of the printer control device 2090 when the light from the light source 13 is irradiated onto the recording paper is “S03”. The signal level in the output signal is referred to as “04”. Further, the light receiver 23 and the light receiver 25 are provided closer to the illumination center than the light receiver 17 so that S03 and S04 are substantially the same size as S02, and the reflected light capture angle is set by the light receiver 17. This is larger than the reflected light taking-in angle. Note that the output signal levels of all the light detection systems are not necessarily equal. For example, when the output signal of the first light detection system that detects specularly reflected light is amplified by another amplifier circuit, the output signal levels of the second to fourth light detection systems may be made equal.

(1) The plurality of light emitting units of the optical sensor 2245 are caused to emit light simultaneously.
(2) The values of S00 to S04 are obtained from the output signals of the respective light receivers.
(3) The values of S01, S02, S03, and S04 are obtained.
(4) With reference to the recording paper discrimination table, the brand of the recording paper is specified from the obtained values S01, S02, S03, and S04.
(5) The brand of the specified recording paper is stored in the RAM, and the paper type discrimination process is terminated.

  In this case, with respect to a plurality of brands of recording paper that can be handled by the color printer 2000, the values of S01, S02, S03, and S04 are measured in advance for each brand of the recording paper in a pre-shipment process such as an adjustment process. The result is stored in the ROM of the printer control device 2090 as a “recording paper discrimination table”.

  In this way, even if there is disturbance light or stray light by providing a plurality of light receiving systems that detect light reflected in different directions, and discriminating the recording paper using the detection values in each light receiving system Accurate discrimination is possible.

  In this case, the printer control apparatus 2090 may narrow down the paper type roughly using S01 and S02, and specify the brand of the recording paper using S03 and S04.

  Moreover, although the case where the light source 13 has five light emission parts and the case where it has four light emission points was demonstrated in the said embodiment, it is not limited to this, The magnitude | size of the lens to be used, and the prescription | regulation of the angle to prescribe | regulate Thus, the number and interval of light emitting portions and light emitting points may be designed.

  Moreover, in the said embodiment, a condensing lens may be provided ahead of each light receiver. In this case, signal level measurement variations can be reduced. Measurement reproducibility is important for an optical sensor that discriminates recording paper based on the amount of reflected light. The optical sensor is installed on the assumption that the measurement surface and the surface of the recording paper are in the same plane at the time of measurement. However, the surface of the recording paper may be inclined or lifted with respect to the measurement surface due to deflection or vibration, and the recording paper surface may not be flush with the measurement surface. This causes a change in the light intensity distribution of the reflected light, the amount of received light changes, and it is difficult to perform detailed discrimination stably. Therefore, if a condenser lens is disposed in front of the light receiver, the amount of received light can be stabilized even if the light intensity distribution of the reflected light changes.

  In addition, by using a photodiode (PD) with a sufficiently large light receiving area for the light receiver or by narrowing the beam diameter of the irradiated light, the inconvenience when the recording paper surface is not flush with the measurement surface can be eliminated. Can do.

  Moreover, it is good also as a structure which has a light reception area | region large enough with respect to the shift amount of reflected light intensity distribution as a whole using PD by which the light reception area | region was arranged in the light receiver. In this case, even if the light intensity distribution of the reflected light is shifted, the output level of the light receiver can be stabilized by using the maximum signal among the signals detected by each PD. In addition, when a plurality of PDs are arrayed, by reducing the light receiving area of each PD, it is possible to reduce fluctuations in output due to the shift between the center of the incident light and the light receiving area, so that more accurate detection is performed. Can do.

  Further, the relationship between the light quantity of S-polarized regular reflection light and the light quantity of P-polarized regular reflection light and the smoothness, thickness and basis weight of the object (recording paper) is obtained in advance, and the database of the printer controller 2090 is used as a database. The smoothness, thickness and basis weight of the object (recording paper) are specified based on the output of the optical sensor 2245 with reference to the database, and the specified smoothness, thickness and Image forming conditions may be adjusted according to the basis weight.

  In the above embodiment, the case where there is one paper feed tray has been described. However, the present invention is not limited to this, and a plurality of paper feed trays may be provided. In this case, an optical sensor 2245 may be provided for each paper feed tray.

  In the above embodiment, the brand of the recording paper may be specified during conveyance. In this case, the optical sensor 2245 is disposed in the vicinity of the conveyance path. For example, the optical sensor 2245 may be disposed in the vicinity of the conveyance path between the paper feed roller 2054 and the transfer roller 2042.

  In the above embodiment, the brand of the recording paper may be specified before the paper is filled in the paper feed tray. In this case, the optical sensor 2245 is installed outside the color printer 2000. For example, the optical sensor 2245 may be placed on the upper surface of the exterior of the color printer 2000. Further, as an example, the optical sensor 2245 may have a shape that can be easily held by hand, and may have a configuration in which the optical sensor 2245 can be removed when specifying the brand of the recording paper.

  The object identified by the optical sensor 2245 is not limited to recording paper.

  In the above embodiment, the case of the color printer 2000 as the image forming apparatus has been described. However, the present invention is not limited to this. For example, a laser printer that forms a monochrome image may be used. Further, it may be an image forming apparatus other than a printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated.

  In the above embodiment, the case where the image forming apparatus has four photosensitive drums has been described. However, the present invention is not limited to this. For example, a printer having five photosensitive drums may be used.

  In the above embodiment, the image forming apparatus is described in which the toner image is transferred from the photosensitive drum to the recording paper via the transfer belt. However, the present invention is not limited to this, and the toner image is recorded from the photosensitive drum. It may be an image forming apparatus that is directly transferred to paper.

  The optical sensor 2245 can also be applied to an image forming apparatus that forms an image by spraying ink on recording paper.

2000 Color Printer 2010 Optical Scanning Device 2030 Photosensitive Drum 2031 Cleaning Unit 2032 Charging Device 2033 Developing Roller 2040 Transfer Belt 2042 Transfer Roller 2050 Fixing Device 2054 Paper Roll 2058 Paper Discharge Roller 2060 Paper Feed Tray 2070 Paper Discharge Tray 2080 Communication Control Device 2090 Printer control device 2245 Optical sensor 11 Irradiation unit 12 Object (recording paper)
13 Light source 14 Light emitter 15 Light receiver 16 Polarizing optical element 17 Light receiver 18 Collimator lens 19 Storage memory 20 Output signal setting value 21 Light emitter selection means 22 Light emitting point 23 Light receiver 24 Polarizing filter 25 Light receiver 26 Wiring member 27 Electrode pad 190 Dark box 191 opening

JP 2005-156380 A JP 2012-127937 A JP 2013-186282 A

Claims (13)

An irradiation unit that emits light having an angle with respect to the normal of the surface toward the surface of the object, and the angle can be changed;
A light detection unit that detects light reflected from the object and outputs a signal emitted from the irradiation unit, and
The optical sensor, wherein the angle is set based on an output signal from the light detection unit. A processing unit for identifying the object based on the output signal;
The processing unit has a storage memory for storing an output signal set value from the light detection unit at the set angle,
The optical sensor according to claim 1, wherein the angle is set based on the output signal setting value stored in the storage memory and the output signal from the light detection unit. The irradiation unit includes a light source having a plurality of light emitting units,
The processing unit is configured to select a light emitting unit based on the output signal set value stored in the storage memory and a plurality of signal values from the light detection unit, and
The optical sensor according to claim 2, further comprising:   The optical sensor according to claim 3, wherein the light emitting unit selection unit selects a light emitting unit having a signal value closest to the output signal set value from the plurality of light emitting units.   The optical sensor according to claim 4, wherein the light emitting unit selection unit can change the selected light emitting unit to another light emitting unit.   6. The changed light emitting unit is a light emitting unit adjacent to the selected light emitting unit, and is another light emitting unit that is second closest to the output signal setting value. Optical sensor.   The optical sensor according to claim 6, wherein the light emitting portion of the light source of the irradiating portion includes a plurality of light emitting points. An irradiation unit that emits linearly polarized light having a first polarization direction having an angle with respect to a normal line of the surface toward the surface of the object and being substantially parallel light by a collimator lens;
A first light detection system including a first light detector that detects light emitted from the irradiation unit and reflected by the object;
A polarization optical element that is disposed on an optical path of light diffusely reflected by the object and separates a linearly polarized light component in a second polarization direction orthogonal to the first polarization direction, and separated by the polarization optical element A second light detection system including a second light detector for receiving a linearly polarized light component in the second polarization direction;
A processing unit that identifies the object based on output signals of the first to second photodetectors;
The irradiation unit includes a light source having a plurality of light emitting units,
The optical sensor is capable of changing the angle, and sets the angle according to an output signal from the first photodetector. A third light detection system including at least one light detector disposed on an optical path of light diffusely reflected by the object;
The optical sensor according to claim 8, further comprising: a processing unit that identifies the object based on an output signal of at least one photodetector of the third light detection system. At least one optical element that is disposed on the optical path of light diffusely reflected by the object and separates linearly polarized light in the second polarization direction, and at least one that receives light separated by the at least one optical element. A fourth light detection system including two light detectors;
The optical sensor according to claim 9, further comprising: a processing unit that identifies the object based on an output signal of at least one photodetector of the fourth light detection system.   An image forming apparatus for forming an image on a recording medium, comprising the optical sensor according to claim 1, wherein the recording medium is an object.   The image forming apparatus according to claim 11, further comprising an adjusting device that adjusts an image forming condition in accordance with an object specified by the object specifying unit of the optical sensor. The adjustment device identifies the brand of the recording medium based on the output signal of the optical sensor,
The image forming apparatus according to claim 12, wherein image forming conditions are adjusted according to the specified brand.