JP2012131593A - Optical sensor and image forming system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sensor capable of specifying an object from among a number of kinds.SOLUTION: The optical sensor includes a light source 11, a collimate lens 12, two optical receivers (13, 15), a polarizing filter 14, two mirrors (21, 22), a box 16, a standard plate 17, a holding member 18, etc. The optical receiver 13 is arranged to receive a P-polarized component included in internal diffusion reflection light, and the optical receiver 15 is arranged to mainly receive front face regular reflected light. When paper type determination processing is carried out, an opening of the box 16 is opened, and when the paper type determination processing is not carried out, the opening is sealed.

Description

  The present invention relates to an optical sensor and an image forming apparatus, and more particularly to an optical sensor suitable for determining the type of an object and an image forming apparatus including the optical sensor.

  In an image forming apparatus such as a copying machine or a printer, in order to form a high-quality image on a plurality of types of sheet-like recording media, the type of the recording medium is determined before image formation, and according to the determination result. A device that sets image forming conditions suitable for the type of recording medium is known.

  The type of the recording medium is determined by measuring the amount of reflected light from the recording medium and the thickness of the recording medium, and referring to the relationship between the type of the recording medium acquired in advance and the amount of reflected light and the thickness. .

  For example, Patent Document 1 discloses a sheet material material discrimination device that discriminates the material of a moving sheet material based on a reflected light amount reflected from the surface of the sheet material and a transmitted light amount transmitted through the sheet material.

  Further, Patent Document 2 discloses an image forming apparatus having a determination unit that determines the presence / absence of a recording material accommodated in a sheet feeding unit and the presence / absence of a sheet feeding unit based on a detection output from a reflective optical sensor. Has been.

  As a method for measuring the thickness of the recording medium, a method using a transmitted light type, an ultrasonic wave or the like has been proposed.

  However, in the conventional discrimination method, only rough classification such as non-coated paper / coated paper / OHP sheet can be performed, which is insufficient for high-quality image formation.

  The present invention has been made under such circumstances, and a first object thereof is to provide an optical sensor capable of specifying an object from many types.

  A second object of the present invention is to provide an image forming apparatus capable of forming a high quality image.

  From the first viewpoint, the present invention is directed to an irradiation system that emits linearly polarized light in a first polarization direction toward a surface of a sheet-like object from a direction inclined with respect to the normal line of the surface; A first photodetector arranged on an optical path of light emitted from the irradiation system and specularly reflected by the object; and light of light diffusely reflected by the object within an incident surface of the object An optical element disposed on the road and transmitting a linearly polarized component in a second polarization direction orthogonal to the first polarization direction; a second photodetector for receiving light transmitted through the optical element; System, the first photodetector, the optical element, and the second photodetector are held, and has an opening serving as an optical path of a light beam directed to the object and a light beam reflected by the object A standard member for detecting the presence or absence of contamination in the housing. It is, in the standby state, and a sealing member covering the opening; an optical sensor comprising a.

  According to this, an object can be specified from many types.

  According to a second aspect of the present invention, there is provided an image forming apparatus for forming an image on a recording medium, comprising the optical sensor of the present invention having the recording medium as an object.

  According to this, a high quality image can be formed.

1 is a diagram for describing a schematic configuration of a color printer according to an embodiment of the present invention. FIG. 2A is a diagram for explaining the standby position of the optical sensor, and FIG. 2B is a diagram for explaining the discriminating position of the optical sensor. FIG. 2C and FIG. () Is a figure for demonstrating the raising / lowering mechanism of an optical sensor, respectively. It is a figure for demonstrating the structure of an optical sensor. It is a figure for demonstrating the opening part of the housing | casing of an optical sensor. FIGS. 5A to 5C are diagrams for explaining the position (sealing position) of the holding member when the optical sensor is in the standby position. FIGS. 6A to 6C are views for explaining the position (open position) of the holding member when the optical sensor is in the determination position. It is a figure for demonstrating the raising member and guide member of a raising / lowering mechanism. FIG. 8A and FIG. 8B are diagrams for explaining the operation of the hoisting mechanism. It is a figure for demonstrating a roller guide. It is a figure for demonstrating a surface emitting laser array. It is a figure for demonstrating the incident angle of the incident light to an irradiation target object. It is a figure for demonstrating an illumination area | region. It is a figure for demonstrating the arrangement position of the polarizing filter and the light receiver. It is a figure for demonstrating the arrangement position of the mirror 22 and the light receiver. It is a figure for demonstrating the state of an opening part when an optical sensor exists in a standby position. It is a figure for demonstrating the state of a recording paper and an opening part when an optical sensor exists in a discrimination position. FIG. 17A is a diagram for explaining surface regular reflection light, FIG. 17B is a diagram for explaining surface diffuse reflection light, and FIG. 17C is a diagram explaining internal diffuse reflection light. It is a figure for doing. It is a figure for demonstrating the light received with each light receiver. It is a figure for demonstrating the relationship between S1 and S2 and the brand of a recording paper. It is a figure for demonstrating the relationship between the position of a standard board, and the light reception position in a light receiver. It is a figure for demonstrating the modification of an optical sensor.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a color printer 2000 as an image forming apparatus according to an embodiment.

  The color printer 2000 is a tandem multi-color printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical scanning device 2010, four photosensitive drums (2030a, 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), four developing rollers (2033a, 2033b, 2033c, 2033d), 4 Toner cartridges (2034a, 2034b, 2034c, 2034d), transfer belt 2040, transfer roller 2042, fixing device 2050, paper feed roller 2054, registration roller pair 2056, paper discharge roller 2058, paper feed tray 2 60, the discharge tray 2070, a communication control device 2080, a printer control device 2090 for centrally controlling the optical sensor 2245, and the above units.

  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 described in a program written in code readable by the CPU, various data used when executing the program, a RAM as a working memory, an analog data An AD conversion circuit for converting the signal into digital data. 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.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a are used as a set and form an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image. Constitute.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, the toner cartridge 2034b, and the cleaning unit 2031b are used as a set and form an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image. Constitute.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c are used as a set, and form an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image. Constitute.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d are used as a set, and form an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image. Constitute.

  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.

  Based on the multicolor image information (black image information, cyan image information, magenta image information, yellow image information) from the higher-level device, the optical scanning device 2010 charges the light flux modulated for each color correspondingly. Irradiate each surface of the photosensitive drum. As a result, on the surface of each photoconductive drum, the charge disappears only in the portion irradiated with light, and a latent image corresponding to the image information is formed on the surface of each photoconductive drum. The latent image formed here moves in the direction of the corresponding developing roller as the photosensitive drum rotates.

  The toner cartridge 2034a stores black toner, and the toner is supplied to the developing roller 2033a. The toner cartridge 2034b stores cyan toner, and the toner is supplied to the developing roller 2033b. The toner cartridge 2034c stores magenta toner, and the toner is supplied to the developing roller 2033c. The toner cartridge 2034d stores yellow toner, and the toner is supplied to the developing roller 2033d.

  As each developing roller rotates, the toner 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 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, and the paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060 and conveys it to the registration roller pair 2056. Incidentally, the bundle of recording paper in the paper feed tray 2060 is urged upward so as to contact the paper feed roller 2054 by a spring mechanism (not shown).

  The registration roller pair 2056 sends the recording paper toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color 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.

  The optical sensor 2245 is a sensor for determining the type of recording paper stored in the paper feed tray 2060.

  When the optical sensor 2245 is not in operation, as shown in FIG. 2A as an example, the optical sensor 2245 is disposed at a position where the attachment and detachment of the paper feed tray 2060 is not hindered (hereinafter also referred to as “standby position” for convenience). ing. Further, the state of the optical sensor 2245 when in the standby position is referred to as a “standby state”.

  In operation, the optical sensor 2245, as shown in FIG. 2B as an example, is a position pressed on the surface of the recording paper on the top of the stack of recording paper (hereinafter, “discrimination position” for convenience). ”). Further, the state of the optical sensor 2245 when it is in the determination position is referred to as a “discrimination state”.

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

  As an example, as shown in FIG. 2C, a block in which a through hole and a screw hole are formed is attached to the + Y side of the optical sensor 2245.

  As an example, as shown in FIG. 2D, a round bar is inserted into the through hole of the block, and a screw bar is fitted into the screw hole. One end of the screw rod is fixed to the motor, and when the motor rotates, the screw rod also rotates, and the optical sensor 2245 moves, that is, moves up and down in the Z-axis direction. This motor is driven by the printer controller 2090. That is, the optical sensor 2245 is positioned at the standby position and the determination position by the printer control device 2090.

  Thus, the raising / lowering mechanism of the optical sensor 2245 is comprised by the block, the round bar, the screw rod, and the motor. Note that the lifting mechanism of the optical sensor 2245 may have a different configuration.

  As shown in FIG. 3 as an example, the optical sensor 2245 includes a light source 11, a collimating lens 12, two light receivers (13, 15), a polarizing filter 14, two mirrors (21, 22), a housing 16, A standard plate 17 and a holding member 18 are provided.

  The casing 16 is a box member made of aluminum, and the surface thereof is subjected to black alumite treatment in order to reduce the influence of disturbance light and stray light. In addition, the bottom plate has an opening that serves as an optical path for the light beam directed to the recording paper and the light beam reflected by the recording paper (see FIG. 4).

  The standard plate 17 is a plate-like member that is slightly smaller than the opening of the housing 16, and is configured by a fiber that partially diffuses and reflects inside when light from the light source 11 enters. ing. For example, a laminate of a plurality of papers or a sheet of glass wool can be used.

  The holding member 18 is a frame-like member whose outer shape is slightly larger than the opening of the housing 16, and a standard plate 17 is attached to one surface thereof. The center of the holding member 18 is an opening that serves as an optical path for the light flux from the light source 11 toward the standard plate 17 and the light flux reflected by the standard plate 17 toward each light receiving portion. That is, the light beam from the light source 11 is irradiated to the standard plate 17 without being lost, and the light beam reflected by the standard plate 17 is directed to each light receiver without being lost.

  When the optical sensor 2245 is in the standby position, the holding member 18, as an example shown in FIGS. 5A to 5C, covers the opening of the housing 16 (hereinafter referred to as “sealing position”). ”). At this time, the surface on the + Z side of the standard plate 17 is set to be substantially the same position as the surface on the −Z side of the bottom surface of the housing 16 with respect to the Z-axis direction. Hereinafter, the surface on the + Z side of the standard plate 17 is referred to as the surface of the standard plate 17.

  When the optical sensor 2245 is in the determination position, the holding member 18 is raised with one end in the short direction as a fulcrum as shown in FIGS. 6A to 6C as an example. It is in a position for opening the opening (hereinafter also referred to as “open position”).

  A raising / lowering mechanism for raising and lowering the holding member 18 from the sealed position to the opened position and from the opened position to the sealed position is shown in FIG. Here, the raising and lowering mechanism includes a push-up member 31, a guide member 32, a support member 35 that supports the holding member 18 so as to be raised and lowered, and a roller guide 36. The undulation mechanisms are respectively attached to both ends of the holding member 18 in the longitudinal direction (see FIG. 9).

  The push-up member 31 includes a columnar or prismatic column member, an arm member attached substantially horizontally near the + Z side end of the column member, a rotating member such as a bearing attached to the tip of the arm member, a column It is comprised from the disk-shaped pressing board attached to the -Z side edge part of a member.

  The pressing plate prevents the recording paper from being damaged when the column member is pressed against the recording paper. The rotating member rotates on the roller guide 36.

  The guide member 32 is a pipe-like member, and the column member of the push-up member 31 is inserted therein. The guide member 32 is formed with a slit for guiding the vertical movement of the column member of the push-up member 31. The slit also has a function of preventing the push-up member 31 from rotating.

  8A and 8B schematically show how the holding member 18 is raised and lowered by the raising and lowering mechanism. A counterbore hole is formed in the surface of the bottom plate of the housing 16 on the −Z side to prevent the pressing plate from being strongly pressed against the recording paper.

  The light source 11 has a plurality of light emitting units. Each light emitting unit is a vertical cavity surface emitting laser (VCSEL) formed on the same substrate. That is, the light source 11 includes a surface emitting laser array (VCSEL array). Here, as shown in FIG. 10 as an example, nine light emitting units (ch1 to ch9) are two-dimensionally arranged.

  The light source 11 is arranged so that a light beam that becomes S-polarized light is emitted in the −Z direction with respect to the recording paper.

  The light source 11 has a monitor system for monitoring the amount of emitted light flux. This monitor system includes, for example, a branching optical element that branches a part of the light beam emitted from the surface emitting laser array, and a light receiving element that receives the light beam branched by the branching optical element.

  The light source 11 has a drive circuit for driving the surface emitting laser array, and the drive circuit makes the light amount of the light beam emitted from the light source 11 constant based on the output signal of the light receiving element of the monitor system. The drive signal is controlled. This control is called APC (Auto Power Control).

  The collimating lens 12 is disposed on the optical path of the light beam emitted from the light source 11, and makes the light beam substantially parallel light.

  Here, the light source 11 and the collimating lens 12 are integrated and attached to the housing 16.

  The mirror 21 is disposed on the optical path of the light beam through the collimator lens 12 and bends the optical path of the light beam in a direction toward the opening of the housing 16. Here, as shown in FIG. 11 as an example, the light beam reflected by the mirror 21 is directed toward the center of the surface of the standard plate 17 with respect to the X-axis direction when the holding member 18 is in the sealing position. The incident angle θ to 17 is set to be 80 °. In FIG. 11, the holding member 18 is not shown in order to avoid complexity. In the following, the center of the illumination area (see FIG. 12) on the surface of the standard plate 17 is abbreviated as “illumination center”.

  By the way, when light is incident on the boundary surface of the medium, a surface including the incident light ray and the normal of the boundary surface set at the incident point is called an “incident surface”. Therefore, when the incident light is composed of a plurality of light beams, there is an incident surface for each light beam. Here, for convenience, the light incident surface incident on the illumination center is referred to as the incident surface of the standard plate 17. And That is, the plane that includes the illumination center and is parallel to the XZ plane is the incident plane of the standard plate 17.

  The polarizing filter 14 is disposed on the + Z side of the illumination center. The polarizing filter 14 is a polarizing filter that transmits P-polarized light and shields S-polarized light. Instead of the polarizing filter 14, a polarizing beam splitter having an equivalent function may be used.

  The light receiver 13 is disposed on the + Z side of the polarizing filter 14. Here, as shown in FIG. 13, the angle formed by the line L1 connecting the illumination center and the centers of the polarizing filter 14 and the light receiver 13 and the surface of the standard plate 17 is 90 °.

  Here, the polarizing filter 14 and the light receiver 13 are integrated and attached to the housing 16.

  As an example, as shown in FIG. 14, the mirror 22 is disposed on the optical path of the light beam regularly reflected by the surface of the standard plate 17, and bends the optical path of the light beam in the + Z direction.

  The light receiver 15 is disposed on the optical path of the light beam reflected by the mirror 22.

  Therefore, the center of the light source 11, the center of the light receiver 13, and the center of the light receiver 15 are all present on the incident surface of the standard plate 17.

  Here, when the optical sensor 2245 is in the standby position, the push-up member 31 is lowered by the weight of the push-up member 31 and the holding member 18, and as shown in FIG. Become. As a result, paper dust or the like enters the inside of the housing 16, and contamination of the optical system can be prevented. Therefore, the light beam emitted from the light source 11 at this time irradiates the surface of the standard plate 17. Then, the reflected light from the standard plate 17 is received by each light receiving unit. In addition, in order to avoid complexity, the display of the undulation mechanism is omitted in FIG.

  Further, when the optical sensor 2245 is in the determination position, the push-up member 31 is lifted by being pressed against the recording paper, and the position of the holding member 18 becomes the open position as shown in FIG. At this time, the recording sheet is located immediately below the opening. Therefore, the light beam emitted from the light source 11 at this time irradiates the surface of the recording paper. Then, the reflected light from the recording paper is received by each light receiving unit. In addition, in order to avoid complexity, the display of the undulation mechanism is omitted in FIG.

  Hereinafter, when it is not necessary to distinguish between the standard plate 17 and the recording paper, they are collectively referred to as an “irradiation target”.

  By the way, the reflected light when the irradiation object is irradiated with light can be divided into reflected light reflected on the surface of the irradiation object and reflected light reflected inside the irradiation object. Further, the reflected light reflected on the surface of the irradiation object can be divided into specularly reflected light and diffusely reflected light. Hereinafter, for convenience, the reflected light that is regularly reflected on the surface of the irradiation object is also referred to as “surface regular reflected light”, and the reflected light that is diffusely reflected is also referred to as “surface diffuse reflected light” (FIG. 17A and FIG. 17). B)).

  The surface of the irradiation object is composed of a flat portion and an inclined surface portion, and the smoothness of the surface is determined by the ratio. The light reflected by the plane portion becomes surface regular reflection light, and the light reflected by the slope portion becomes surface diffuse reflection light. The surface diffuse reflection light is reflected light that is completely scattered and reflected, and the reflection direction can be considered to be isotropic. And the light quantity of surface regular reflection light increases, so that smoothness becomes high.

  On the other hand, the reflected light from the inside of the irradiation object is only diffusely reflected light because it is scattered multiple times in the fibers inside. Hereinafter, for the sake of convenience, the reflected light from the inside of the irradiation object is also referred to as “internal diffuse reflected light” (see FIG. 17C). Similar to the surface diffuse reflection light, the internal diffuse reflection light is also a reflection light that has been completely scattered and reflected, and the reflection direction can be considered to be isotropic.

  The polarization direction of the surface regular reflection light and the surface diffuse reflection light is the same as the polarization direction of the incident light. On the other hand, it has been confirmed by the inventors' various experiments that the polarization direction of the internally diffuse reflected light is rotated from the polarization direction of the incident light. This is presumably because the light passes through the fiber and rotates during multiple scattering, and the polarization direction rotates.

  Therefore, the surface diffuse reflection light and the internal diffuse reflection light are incident on the polarizing filter 14. Since the polarization direction of the surface diffuse reflection light is the same S polarization as the polarization direction of the incident light, the surface diffuse reflection light is shielded by the polarization filter 14. On the other hand, since the polarization direction of the internal diffuse reflection light is rotated from the polarization direction of the incident light, the P-polarized component included in the internal diffuse reflection light is transmitted through the polarization filter 14. That is, the P-polarized component included in the internally diffuse reflected light is received by the light receiver 13 (see FIG. 18). In FIG. 18, the standard plate 17 and the holding member 18 are not shown in order to avoid complication.

  The inventors have confirmed from various experiments that the light quantity of the P-polarized component contained in the internally diffuse reflected light has a correlation with the thickness and density of the irradiation object. This is considered because the light quantity of the P-polarized component depends on the path length when passing through the fiber of the irradiation object.

  Only a part of the surface regular reflection light, the surface diffuse reflection light and the internal diffuse reflection light is incident on the light receiver 15. That is, the surface regular reflection light is mainly incident on the light receiver 15.

  The light receiver 13 and the light receiver 15 each output an electrical signal (photoelectric conversion signal) corresponding to the amount of received light to the printer control device 2090. In the following, the signal level in the output signal of the light receiver 13 when the light beam from the light source 11 is irradiated onto the irradiation object is referred to as “S1”, and the signal level in the output signal of the light receiver 15 is referred to as “S2”.

  Here, for a plurality of brands of recording paper that can be handled by the color printer 2000, the values of S1 and S2 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 expressed as a “recording paper discrimination table Is stored in the ROM of the printer control device 2090. FIG. 19 shows the measured values of S1 and S2 for 6 brands of plain paper (N1 to N6), 3 brands of matte coated paper (M1 to M3), and 9 brands of glossy coated paper (G1 to G9). ing.

  Conventionally, the glossiness of the recording paper surface is detected from the amount of specularly reflected light, and the smoothness of the recording paper surface is detected from the ratio of the amount of specularly reflected light and the amount of diffusely reflected light. I was trying to identify the recording paper. In contrast, in the present embodiment, not only the glossiness and smoothness of the surface of the recording paper but also information including the thickness and density, which are other characteristics of the recording paper, is detected from the reflected light and can be identified. The type of is expanded more than before.

  For example, as shown in FIG. 19, it is difficult to distinguish between plain paper and mat-coated paper only by information on the surface of the recording paper (horizontal axis) used in the conventional identification method. When the information inside the recording paper (vertical axis) is added to the information on the surface of the recording paper (vertical axis), not only distinction between plain paper and matte coated paper but also multiple brands of plain paper and multiple brands of matte coat Paper can also be distinguished from each other.

  That is, in the present embodiment, it is possible to specify the brand of the object from a plurality of recording papers having at least one of glossiness, smoothness, thickness, and density.

  In addition, regarding multiple brands of recording paper that can be handled by the color printer 2000, the optimum development conditions and transfer conditions at each station are determined for each brand of recording paper in the pre-shipment process such as the adjustment process, and the results of the determination are determined. It is stored in the ROM of the printer controller 2090 as a “development / transfer table”.

  The printer control device 2090 performs a paper type discrimination process for the recording paper when the color printer 2000 is turned on and 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 optical sensor 2245 is moved from the standby position to the determination position via the lifting mechanism.
(2) The light emitting units of the optical sensor 2245 are turned on simultaneously.
(3) The values of S1 and S2 are obtained from the output signals of the light receiver 13 and the light receiver 15.
(4) With reference to the recording paper discrimination table, the brand of the recording paper is specified from the obtained values of S1 and S2.
(5) 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 addition, when the optical sensor 2245 is in a standby state, the printer control device 2090 performs a monitoring process for monitoring the presence or absence of contamination in the housing 16 periodically (for example, every day).

  In this monitoring process, the standard plate 17 is irradiated with the light beam from the light source 11, and the output value of each light receiver is compared with the output value in the previous monitoring process to determine whether or not the inside of the casing 16 is contaminated. Detect. If the difference between the current output value and the previous output value exceeds a preset threshold value, the printer control device 2090 determines that the inside of the housing 16 is contaminated, and the display is not shown. A message is displayed and the user is notified.

  Note that when the monitoring process is being performed, the paper feeding operation is prohibited.

  As described above, according to the color printer 2000 according to the present embodiment, the optical scanning device 2010, the four image forming stations, the transfer belt 2040, the transfer roller 2042, the fixing device 2050, the paper feed tray 2060, the optical sensor 2245, and A printer control apparatus 2090 that controls the entire apparatus is provided.

  The optical sensor 2245 includes a light source 11, a collimating lens 12, two light receivers (13, 15), a polarizing filter 14, two mirrors (21, 22), a housing 16, a standard plate 17, a holding member 18, and the like. ing.

  The light receiver 13 receives the P-polarized light component contained in the internally diffuse reflected light, and the light receiver 15 is disposed so as to mainly receive the surface regular reflection light.

  The optical sensor 2245 opens the opening of the housing 16 when the paper type determination process is performed, and seals the opening when the paper type determination process is not performed. This makes it possible to prevent the inside of the housing 16 from being contaminated, and as a result, high discrimination accuracy of the optical sensor 2245 can be maintained.

  Further, since the printer control device 2090 periodically performs monitoring processing, the reliability of the discrimination accuracy of the optical sensor 2245 can be improved.

  Therefore, from the output signal of the light receiver 13 and the output signal of the light receiver 15, the type of recording paper can be identified stably and accurately from many types.

  Further, since the surface emitting laser array is used as the light source, a polarizing filter for making the irradiation light linearly polarized light is unnecessary. In addition, since the irradiation light can be easily converted into parallel light, and a light source having a plurality of light emitting units can be realized by downsizing, the downsizing and cost reduction of the optical sensor can be achieved.

  In addition, since the light source has a plurality of light emitting units, the amount of P-polarized component contained in the internally diffuse reflected light can be increased. Furthermore, by simultaneously lighting a plurality of light emitting units, the contrast ratio of the speckle pattern of reflected light can be reduced, and the discrimination accuracy can be improved.

  Further, since the surface of the standard plate 17 is at the same position as the surface of the recording paper with respect to the Z-axis direction, the aperture of the light receiving element included in each light receiver can be reduced. For example, FIG. 20 shows a case where the surface of the standard plate 17 is on the + Z side with respect to the surface of the recording paper. This also makes it possible to make the optical path for the monitoring process substantially the same as the optical path for the paper type discrimination process.

  In addition, since the opening is opened and closed by the undulation mechanism including the push-up member 31 and the guide member 32, the optical sensor can be prevented from becoming complicated, large, and expensive.

  Since the color printer 2000 includes the optical sensor 2245, as a result, a high-quality image can be stably formed. Furthermore, the troublesome printing that has to be set manually and the printing failure due to setting errors are eliminated.

  In the above embodiment, the case where the light applied to the recording paper is S-polarized light has been described. However, the present invention is not limited to this, and the light applied to the recording paper may be P-polarized light. However, in this case, a polarizing filter that transmits the S-polarized component is used instead of the polarizing filter 14.

  Moreover, although the said embodiment demonstrated the case where the light source 11 had a several light emission part, it is not limited to this, If the light quantity of the P polarization component of internal diffuse reflection light is securable, the light source 11 May have one light emitting portion.

  In the above embodiment, the light emitted from the surface emitting laser array may not be S-polarized light. However, in this case, for example, it is necessary to provide a polarizer between the collimating lens 12 and the mirror 21 so that the light applied to the recording paper becomes S-polarized light.

  In the above embodiment, a conventional LD (Laser Diode) may be used instead of the surface emitting laser array. However, in this case, as shown in FIG. 21 as an example, a polarizing filter 23 is required to make the light irradiated to the recording paper S-polarized light.

  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.

  Moreover, although the said embodiment demonstrated the case where incident angle (theta) with respect to the surface of an irradiation target object was 80 degrees in the optical sensor 2245, it is not limited to this. In addition, as incident angle (theta), it is preferable that it is 60 degrees-80 degrees.

  In the above embodiment, in the printer control apparatus 2090, at least a part of the processing according to the program by the CPU may be configured by hardware, or all may be configured by hardware.

  In the above embodiment, the color printer 2000 is described as the image forming apparatus. However, the present invention is not limited to this, and may be, for example, an optical plotter or a digital copying apparatus.

  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.

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

  The optical sensor 2245 can also be applied to apparatuses other than the image forming apparatus. For example, it is also possible to use for the apparatus which discriminates authenticity, such as a banknote and a stock certificate.

  In the optical sensor 2245, when the object is not paper, the standard plate 17 similar to the object is used.

  As described above, according to the optical sensor of the present invention, it is suitable for specifying an object from many types. The image forming apparatus of the present invention is suitable for forming a high quality image.

  DESCRIPTION OF SYMBOLS 11 ... Light source (a part of irradiation system), 12 ... Collimating lens (a part of irradiation system), 13 ... Light receiver (2nd photodetector), 14 ... Polarizing filter (optical element), 15 ... Light receiver ( 1st photodetector), 16 ... casing, 17 ... standard plate, 18 ... holding member (sealing member), 21 ... mirror (part of irradiation system), 22 ... mirror, 23 ... polarizing filter, 31 ... Push-up member (part of the drive mechanism), 32 ... Guide member (part of the drive mechanism), 2000 ... Color printer (image forming apparatus), 2010 ... Optical scanning device, 2030a, 2030b, 2030c, 2030d ... Photosensitive drum ( Image carrier), 2032a, 2032b, 2032c, 2032d ... charging device, 2033a, 2033b, 2033c, 2033d ... developing roller (part of developing device), 2040 ... transfer belt, 2042 ... transfer Over La (part of the transfer device), 2050 ... fixing device, 2090 ... printer controller (contamination detection device, processing device), 2245 ... optical sensor.

JP-A-10-160687 JP 2006-062842 A

Claims (7)

An irradiation system for emitting linearly polarized light in the first polarization direction toward the surface of the sheet-like object from a direction inclined with respect to the normal line of the surface;
A first photodetector disposed on an optical path of light emitted from the irradiation system and regularly reflected by the object;
An optical element disposed on an optical path of light diffusely reflected by the object and transmitting a linearly polarized light component having a second polarization direction orthogonal to the first polarization direction within an incident surface of the object;
A second photodetector for receiving light transmitted through the optical element;
The irradiation system, the first light detector, the optical element, and the second light detector are held, and an opening serving as an optical path of a light beam directed to the object and a light beam reflected by the object. A housing having;
An optical sensor comprising: a standard member for detecting the presence or absence of contamination in the housing; and a sealing member that covers the opening when in a standby state. The sealing member is supported so that one end can be raised and lowered,
The optical sensor according to claim 1, further comprising: a drive mechanism that raises the sealing member when the casing approaches the object and opens the opening. Irradiating the standard plate with a light beam from the irradiation system;
3. The contamination detection device according to claim 1, further comprising a contamination detection device configured to detect the presence or absence of contamination in the housing based on output signals of the first photodetector and the second photodetector. 4. Optical sensor. Irradiating the object with a light flux from the irradiation system;
The processing apparatus which specifies the said target object based on the output signal of a said 1st photodetector and a said 2nd photodetector is provided, The Claims 1-3 characterized by the above-mentioned. Optical sensor.   The optical sensor according to claim 1, wherein the irradiation system includes a surface emitting laser array having a plurality of light emitting units. In an image forming apparatus for forming an image on a recording medium,
An image forming apparatus comprising the optical sensor according to claim 1, wherein the recording medium is an object.   The image forming apparatus according to claim 6, further comprising an elevating mechanism for changing a distance between the optical sensor and the recording medium.

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