JP6685500B2 - Optical sensor, image forming apparatus, and object discrimination method - Google Patents

Description

The present invention relates to an optical sensor, relates to an image forming instrumentation 置及 beauty object determination method, and more particularly, to determine the optical sensor used for determination of the object, an image forming instrumentation 置及 beauty object comprising said optical sensor The present invention relates to an object discrimination method.

  2. Description of the Related Art In recent years, development of devices and the like for discriminating an object has been actively performed (see, for example, Patent Documents 1 to 7).

  However, in the devices and the like disclosed in Patent Documents 1 to 7, there is room for improvement in obtaining information for discriminating an object in detail.

The present invention is an irradiation means including a plurality of irradiation systems for irradiating an object with linearly polarized light of a predetermined polarization direction from different directions inclined to the object, and the irradiation means irradiating the object with each other. And a detection unit configured to individually detect a plurality of lights reflected in different directions, the irradiation unit having a light source common to at least two irradiation systems of the plurality of irradiation systems, and the light source, a plurality of light emitting portions is an optical sensor surface Ru emitting laser array der to emit light simultaneously.

  According to the present invention, it is possible to obtain information for discriminating an object more finely than in the past.

FIG. 1 is a diagram for explaining a schematic configuration of a color printer according to an embodiment of the present invention. 3 is an external view of the optical sensor 100. FIG. 4 is a diagram for explaining the configuration of the optical sensor 100. FIG. It is a figure for explaining an example of a surface emitting laser array. It is a figure for demonstrating the incident angle of the irradiation light with respect to a recording paper. FIG. 3 is a diagram (No. 1) for explaining that there is an incident angle of irradiation light that facilitates discrimination (identification) depending on the type of recording paper. It is a figure for demonstrating the arrangement position of a some light receiver. 8A is a diagram for explaining surface specular reflection light, FIG. 8B is a diagram for explaining surface diffuse reflection light, and FIG. 8C is a diagram for explaining internal diffuse reflection light. FIG. It is a figure for demonstrating the light received by the light receivers 13 and 15. It is a figure for demonstrating the relationship between signal levels S1 and S2 and the brand of recording paper. FIG. 11 is a diagram for explaining the configuration of the optical sensor of Modification 1. FIG. 11 is a diagram for explaining the configuration of the optical sensor of Modification 2. FIG. 11 is a diagram for explaining the configuration of the optical sensor of Modification 3; It is a figure for demonstrating the relationship between S4 / S1 and S3 / S2 and the brand of recording paper. 15A and 15B are views (No. 1 and No. 2) for explaining the influence of ambient light, respectively. FIG. 3 is a diagram for explaining another example of the surface emitting laser array. FIG. 11 is a diagram for explaining the configuration of the optical sensor of Modification 4; 18A to 18C are views (No. 1 to No. 3) for explaining changes in the detected light amount due to the displacement between the measurement surface and the recording paper surface. 19 (A) and 19 (B) are views (No. 2 and No. 3) for explaining that there is an incident angle of irradiation light, which facilitates discrimination (identification) depending on the type of recording paper. is there. 8 is a flowchart for explaining a recording sheet determination process. 9 is a flowchart for explaining a recording sheet determination process of modification 1.

  A color printer 2000 according to an embodiment of the present invention will be described below with reference to the drawings. It should be noted that in the following description, modification examples will be appropriately described.

  FIG. 1 shows a schematic configuration of a color printer 2000 of one embodiment.

  The color printer 2000 is a tandem-type multicolor printer that superimposes four colors (black, cyan, magenta, and yellow) to form a full-color image on a recording medium, and includes an optical sensor 100 and an optical scanning device 2010, 4. One photoconductor drum (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), transfer belt 2040, transfer roller 2042, fixing device 2050, paper feed roller 2054, paper discharge roller 2058, paper feed tray 2060, manual feed tray (not shown), paper discharge tray 2070, communication control device 2080, Control device 2090, an operation panel (not shown), and a printer housing 2200.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The control device 2090 includes a CPU, a ROM that stores a program written in a code readable by the CPU and various data used when the program is executed, a RAM that is a working memory, an amplifier circuit, It has an AD conversion circuit and the like for converting an analog signal into a digital signal. Then, the control device 2090 controls each unit according to a request from the host device and sends image information from the host device to the optical scanning device 2010. Optimal development conditions and transfer conditions are stored in the ROM as a “development / transfer table” for a plurality of brands of recording paper that can be used as a recording medium by the color printer 2000.

  The operation panel has a plurality of keys for an operator to perform various settings and various processes, and a display unit for displaying various information.

  The photoconductor 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 photoconductor 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 photoconductor 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 photoconductor 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.

  A photosensitive layer is formed on the surface of each of the photosensitive drums. Each photoconductor drum rotates in the direction of the arrow in the plane of FIG. 2 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 multicolor image information (black image information, cyan image information, magenta image information, yellow image information) from the control device 2090. The surface of each photoconductor drum is scanned. As a result, a latent image corresponding to the image information is formed on the surface of each photoconductor drum. That is, here, the surface of each photosensitive drum is the surface to be scanned. Each photoconductor drum is an image carrier. The latent image formed here moves toward 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 of the developing roller. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photoconductor drum, it moves only to the portion of the surface irradiated with light and adheres thereto. That is, each developing roller attaches toner to the latent image formed on the surface of the corresponding photoconductor drum to visualize the latent image. The image to which toner is attached (toner image) moves toward the transfer belt 2040 as the photoconductor drum rotates.

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

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is arranged near 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. The recording paper is sent 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 paper transferred here is sent to the fixing device 2050.

  In the fixing device 2050, heat and pressure are applied to the recording paper, so that the toner is fixed on the recording paper. The recording paper on which the toner has been fixed is sent to the paper ejection tray 2070 via the paper ejection roller 2058, and is sequentially stacked on the paper ejection tray 2070.

  Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photoconductor 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 100 is arranged outside the printer housing 2200 and near the operation panel, and is used to determine the brand of the recording paper.

  The optical sensor 100 is a so-called stationary type optical sensor. As shown in FIG. 2 as an example, the optical sensor 100 has an outer shape of a truncated pyramid, a slit having a predetermined depth is provided in the insertion direction of the recording paper M, and the recording paper M is inserted into the slit. It is like this. Further, inside the optical sensor 100, a processing device 110 for determining the brand of the recording paper is provided. In this specification, in the XYZ three-dimensional orthogonal coordinate system, the direction orthogonal to the surface of the recording paper M inserted into the slit is the Z-axis direction, and the direction in which the recording paper M is inserted into the slit is the + X direction.

  As shown in FIG. 3, the optical sensor 100 includes a plurality (eg, two) light sources (11, 11 ′), a plurality (eg, two) collimating lenses (12, 12 ′), and a plurality (eg, three). The sensor unit including the light receivers (13, 15, 19) and the polarization filter 14, the processing device 110, and the like.

  Here, the first irradiation system including the light source 11 and the collimator lens 12 and the second irradiation system including the light source 11 ′ and the collimator lens 12 ′ constitute an irradiation unit that irradiates the recording paper M with light. There is. Further, a detection system that individually detects a plurality of reflected lights from the recording paper M by a detection system that includes the light receiver 15, a detection system that includes the light receiver 19, and a detection system that includes the light receiver 13 and the polarization filter 14. Is configured.

  Each light source has a plurality of light emitting portions formed on the same substrate. Each light emitting unit is a vertical cavity surface emitting laser (VCSEL). That is, each light source includes a surface emitting laser array (VCSEL array). Here, as shown in FIG. 4, in the surface emitting laser array, nine light emitting portions (ch1 to ch9) are two-dimensionally arranged.

  The respective light sources are arranged so that the recording paper M is irradiated with S-polarized light. The incident angles θ1 and θ2 (see FIG. 5) of the light beams from the two light sources 11 and 11 'on the recording paper M are, for example, θ1 = 75 ° and θ2 = 60 °.

By the way, FIG. 6 shows glossiness measurement values (horizontal axis in FIG. 6) when measurement is performed at an incident angle of 60 ° for plain paper, matte coated paper, and gloss coated paper, and the incident angle is 75 °. The glossiness measurement value (vertical axis in FIG. 6) when the measurement is performed is shown. The theoretical value of the glossiness can be obtained by the following theoretical formula obtained by multiplying the Fresnel reflection formula and the formula expressing the surface roughness.

  Here, each point indicates the measured glossiness value of a different paper brand. Strictly speaking, even if the same brand is used, the glossiness varies slightly from sheet to sheet, so that each point represents a representative value of the glossiness measurement results of each sheet brand.

  Comparing the case of the incident angle of 60 ° and the case of the incident angle of 75 ° in FIG. 6, for the plain paper and the matte coated paper, the measured values of the glossiness are distributed more widely, and the difference between the measured values of the glossiness is large. It can be seen that the brand (feature) can be easily discriminated in the case of ° (a shallow angle to the paper). “Difference between measured glossiness values” means the absolute value of the difference between the representative value of glossiness of a certain brand A and the representative value of glossiness of a certain brand B.

  On the other hand, regarding gloss-coated paper, the brand (feature) is determined when the measured gloss value is more widely distributed and the angle of incidence is 60 ° (the angle that is deeper than the paper) with a large difference between the measured gloss values. You can see that it is easy to do.

  19 (A) and 19 (B) respectively show diagrams in which the horizontal axis and the vertical axis of FIG. 6 are one-dimensionally displayed.

  As can be seen from FIGS. 19 (A) and 19 (B), the denser the distribution of the lateral direction points indicating the glossiness measurement value, the harder the discrimination becomes, and the smaller the distribution, the easier the discrimination becomes.

  As is clear from the above description, it can be seen that the incident angle at which the brand of the recording paper can be easily discriminated changes depending on the refractive index and surface roughness of the recording paper.

  Returning to FIG. 5, each collimating lens is arranged on the optical path of the light flux from the corresponding light source, and makes the light flux substantially parallel light. The light flux passing through each collimator lens illuminates the recording paper M. In this specification, the center of the illumination area on the surface of the recording paper M is abbreviated as “illumination center”. Further, the light flux passing through each collimator lens is also referred to as “irradiation light”.

  By the way, when light is incident on a boundary surface of a medium, a surface including an incident light ray and a normal line of the boundary surface standing at the incident point is called an “incident surface”. Therefore, when the incident light is composed of a plurality of light rays, an incident surface exists for each light ray, but here, for convenience, the incident surface of the light ray incident on the illumination center is referred to as the incident surface on the recording paper M. And That is, the plane including the center of illumination and parallel to the XZ plane is the plane of incidence on the recording paper M.

  In this specification, not only incident light to the recording paper M but also reflected light is referred to as S-polarized light and P-polarized light. The expression is based on the polarization direction, and light having the same polarization direction as the incident light (here, S-polarized light) on the incident plane is called S-polarized light, and light having a polarization direction orthogonal to it is called P-polarized light.

  The polarization filter 14 is arranged on the + Z side of the center of illumination. The polarization filter 14 is a polarization filter that transmits P-polarized light and blocks S-polarized light. A polarization beam splitter having an equivalent function may be used instead of the polarization filter 14.

  The light receiver 13 is arranged on the + Z side of the polarization filter 14. As shown in FIG. 7, the angle ψ1 formed by the line L1 connecting the center of illumination, the center of the polarization filter 14 and the center of the light receiver 13 and the surface of the recording paper M is 90 °.

  The light receiver 15 is arranged on the + X side of the center of illumination in the X-axis direction. The angle ψ2 formed by the line L2 connecting the center of illumination and the center of the light receiver 15 and the surface of the recording paper M is 170 °.

  The light receiver 19 is arranged on the + X side of the center of illumination in the X-axis direction. An angle ψ3 formed by the line L3 connecting the center of illumination and the center of the light receiver 19 and the surface of the recording paper M is 150 °.

  Here, the center of the light source 11, the center of the light source 11 ′, the center of the illumination, the center of the polarization filter 14, the center of the light receiver 13, the center of the light receiver 15, and the center of the light receiver 19 are the XZ plane. Exist on substantially the same plane parallel to, but may be offset from each other in the Y-axis direction.

  Further, a light source for irradiating the recording paper M with light at an angle different from the above may be added, and a light receiver corresponding to the added light source may be added.

  Incidentally, the reflected light from the recording paper when the recording paper is illuminated can be considered separately as reflected light reflected on the surface of the recording paper and reflected light reflected inside the recording paper. Further, the reflected light reflected on the surface of the recording paper can be considered separately as the specular reflected light and the diffuse reflected light. Hereinafter, for convenience, the reflected light specularly reflected on the surface of the recording paper is also referred to as “surface specular reflected light”, and the reflected light diffusely reflected is also referred to as “surface diffuse reflected light” (FIGS. 8A and 8B). )reference).

  The surface of the recording paper is composed of a flat surface portion and a sloped surface portion, and the smoothness of the recording paper surface is determined by the ratio. The light reflected by the flat surface portion becomes the surface regular reflection light, and the light reflected by the inclined surface portion becomes the surface diffuse reflection light. The surface diffuse reflection light is the reflection light that is completely scattered and reflected, and the reflection direction can be considered to be isotropic. Then, as the smoothness increases, the light amount of the surface regular reflection light increases.

  On the other hand, when the recording paper is a general printing paper, the reflected light from the inside of the recording paper is only diffuse reflected light because it is multiply scattered in the fibers inside the recording paper. Hereinafter, for convenience, the reflected light from the inside of the recording paper is also referred to as “internal reflected light or internal diffuse reflected light” (see FIG. 8C). Like the surface diffuse reflection light, the internal reflection light is also the reflection light that is completely scattered and reflected, and the reflection direction can be considered to be isotropic.

  The polarization directions of the surface specular reflection light and the surface diffuse reflection light toward the light receiver are the same as the polarization directions of the incident light (irradiation light). By the way, in order for the polarization direction to rotate on the surface of the recording paper, the incident light must be reflected by a surface inclined in the direction of rotation with respect to the incident direction. Here, since the center of the light source, the center of illumination, and the center of each light receiver are on the same plane, the reflected light whose polarization direction is rotated on the surface of the recording paper is not reflected in any light receiver direction.

  On the other hand, the polarization direction of the internally reflected light toward the light receiver is rotated with respect to the polarization direction of the incident light. It is considered that this is because the light that has entered the inside of the recording paper is transmitted through the fiber and is rotated while being multiple-scattered and the polarization direction is rotated.

  Reflected light in which surface diffuse reflected light and internal reflected light are mixed is incident on the polarization filter 14 (see FIG. 9). In FIG. 9, the light source 11 ', the collimator lens 12', and the light receiver 19 are omitted for convenience.

  Since the surface diffuse reflection light that enters the polarization filter 14 has the same S-polarized light as the incident light, it is shielded by the polarization filter 14. On the other hand, since the internally reflected light is a mixture of S-polarized light and P-polarized light, the P-polarized light component passes through the polarization filter 14. That is, the P-polarized component contained in the internally reflected light is received by the light receiver 13. Note that, hereinafter, for convenience, the P-polarized component included in the internally reflected light is also referred to as “P-polarized internally reflected light”. Further, the S-polarized component included in the internally reflected light is also referred to as “S-polarized internally reflected light”.

  The inventors have confirmed that the amount of P-polarized internal reflection light has a correlation with the thickness and density of the recording paper. This is because the amount of P-polarized internal reflection light depends on the path length when passing through the fibers of the recording paper.

  The surface specularly reflected light and only a part of the surface diffused reflected light and the internal diffused reflected light are incident on the light receivers 15 and 19. That is, the surface specularly reflected light mainly enters the light receivers 15 and 19.

  Each of the light receivers 13, 15, and 19 outputs an electric signal (current signal) corresponding to the amount of received light to the processing device 110. In the following, the signal level of the output signal of the light receiver 13 and the signal level of the output signal of the light receiver 15 when the recording sheet is irradiated with the light flux from the light source 11 will be referred to as "S2". Further, the signal level of the output signal of the photodetector 13 and the signal level of the output signal of the photodetector 19 when the recording sheet is irradiated with the light flux from the light source 11 'are "S3'".

  FIG. 10 shows, as an example, the measured values of S1 and S2 for 30 brands of recording paper sold in Japan. In addition, the frame in FIG. 10 shows the variation range of the same brand. By using both S1 and S2, it is possible to further narrow down or specify a candidate brand among a plurality of brands narrowed down only by the measured values of S1 and S2. As an example, FIG. 10 shows only the relationship between each brand and the measured values of S1 and S2 in the case where the paper type of the discrimination target is plain paper, but the similar relationship also applies to glossy paper and the like.

  Hereinafter, a process of discriminating the brand of the recording paper M whose brand is unknown by using a plurality of light receivers (brand discriminating process) will be described.

The work performed by the worker in the brand identification process will be described.
1. The recording paper M is inserted into the slit of the optical sensor 100.
2. Input the discrimination processing request through the operation panel. This determination processing request is notified from the operation panel to the processing device 110 of the optical sensor 100 via the control device 2090.
3. After a lapse of a predetermined time (for example, about 5 seconds), the recording paper M is pulled out from the slit of the optical sensor 100.

Upon receiving the determination processing request, the processing device 110 starts the brand determination processing.
(1) A plurality of light emitting units of the light source 11 are turned on at the same time.
(2) The values of S1 and S2 are obtained from the output signals of the light receivers 13 and 15.
(3) Turn off the plurality of light emitting units of the light source 11.
(4) A plurality of light emitting units of the light source 11 'are turned on at the same time.
(5) The values of S1 'and S3' are obtained from the output signals of the light receivers 13 and 19.
(6) Turn off the plurality of light emitting units of the light source 11 '.
(7) The processing device 110 identifies (estimates) the brand of the recording paper based on S1 and S2 if the value of S1 is less than or equal to a certain value, and if the value of S1 is more than the certain value, S1 ′ and S3. (8) The specified recording paper brand is stored in the RAM, and the paper type determination process ends.

  The process of identifying the brand will be described with reference to S1 and S2. In FIG. 10, for example, if the measured values of S1 and S2 are “⋄”, it is identified as the brand D. Further, if the measured values of S1 and S2 are “■”, the closest brand C is specified. Further, if the measured values of S1 and S2 are “♦”, it is either brand A or brand B. In this case, 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 brand with the smaller calculation result is narrowed down and specified. Good. Alternatively, for example, assuming that it is the brand A, the variation is recalculated including the measured value, and assuming that it is the brand B, the variation is recalculated including the measured value, and the recalculated variation is calculated. You may narrow down and specify the stock with the smaller.

  By the way, in the above, after the reflected light of the irradiation light from the light source 11 is detected by the two light receivers 13 and 15, the reflected light of the irradiation light from the light source 11 ′ is detected by the two light receivers 13 and 15. The lighting order of the light sources 11 and 11 'is not limited to this. Further, the two light sources 11 and 11 'may be turned on at the same time. Further, when S1 is equal to or less than a certain value and the brand is specified based on S1 and S2, the brand may be further narrowed down by using S3 'or S1'. Similarly, when S1 is a certain value or more and a brand is specified based on S1 'and S3', the brand may be further narrowed down by using S1 or S2. The determination result is notified to the control device 2090. Then, the brand identification process ends.

  The control device 2090 displays the determination result from the processing device 110 on the display unit of the operation panel and stores it in the RAM.

  When the discriminated brand of recording paper is displayed on the display section of the operation panel, the operator sets the discriminated recording paper in the paper feed tray 2060. Note that the brand of the recording paper displayed on the display unit of the operation panel may be registered in the control device 2090 by the operator using the keys of the operation panel.

  Upon receiving the print job request from the user, the control device 2090 reads the brand of the recording paper stored in the RAM, and finds the optimum developing conditions and transfer conditions for the brand of the recording paper from the developing / transfer table.

  Then, the control device 2090 controls the developing device and the transfer device of each station according to the optimum developing condition and transfer condition. For example, the transfer voltage and the toner amount are controlled. As a result, a high quality image is formed on the recording paper.

  Conventionally, the glossiness of the recording paper surface is detected from the light amount of the specular reflection light, and the smoothness of the recording paper surface is detected from the ratio of the light amount of the specular reflection light and the diffuse reflection light to identify the recording paper. I was there. However, the accuracy of brand identification of plain paper / gloss coated paper / matte coated paper differs depending on the incident angle θ of the irradiation light with respect to the recording paper. Therefore, with the information on the reflected light obtained by the unique incident angle used in the conventional identification method, it is possible to distinguish between plain paper and gloss-coated paper (discrimination of the type of recording paper), but with high accuracy for both. It was difficult to make both brand identifications compatible.

  On the other hand, the optical sensor 100 according to the present embodiment includes an irradiation system that irradiates the recording paper with light at a plurality of different incident angles, and individually outputs a plurality of reflected light reflected corresponding to the plurality of irradiation angles. By the detection, the brand can be discriminated with high accuracy for both plain paper and glossy paper.

  Hereinafter, an example of the recording sheet determination process using the optical sensor 100 of the present embodiment will be described with reference to FIG. The flowchart of FIG. 20 is based on the processing algorithm executed by the processing device 110. The control flow here starts when the user inserts the recording sheet M into the slit of the optical sensor 100 and inputs a recording sheet determination request to the processing device 110 via an operation panel (not shown) or a personal computer. To be done.

  In the first step T1, the light source 11 is turned on. That is, a plurality of light emitting portions of the light source 11 are caused to emit light at the same time, and the recording paper M is irradiated with light at an incident angle θ1.

  In the next step T2, the type of the recording paper M is estimated based on the output signals of the light receivers 13 and 15. Specifically, the type of the recording paper M is estimated from the relationship between the signal levels S01 and S02 in the output signals of the light receivers 13 and 15 and FIG. More specifically, the recording paper discrimination table is referred to, and the type of the recording paper M is estimated from the obtained values of S01 and S02. Then, the types of recording paper estimated as the values of S01 and S02 are stored in the RAM.

  In the next step T3, the light source 11 is turned off.

  In the next step T4, it is determined whether the estimated type is plain paper or matte coated paper (hereinafter referred to as "plain paper or the like"). If the determination here is affirmative, the process proceeds to step T5, and if the determination is negative, the process proceeds to step T6.

  In step T5, the brand of the recording paper M is estimated based on the output signals of the light receivers 13 and 15. Since the output signal of the light receiver 15 is the detection result at the incident angle θ1 suitable for brand identification of plain paper or the like, it is possible to easily estimate the brand of the recording paper M estimated to be plain paper or the like. Specifically, with reference to the recording paper discrimination table, the brand of recording paper is estimated from the values of S01 and S02 stored in the RAM in step T2. When step T5 is executed, the flow moves to step T8.

  In step T6, the light source 11 'is turned on. That is, a plurality of light emitting units of the light source 11 'are caused to emit light at the same time, and the recording paper M is irradiated with light at an incident angle θ2.

  In the next step T7, the type of the recording paper M is estimated based on the output signals of the light receivers 13 and 19. Specifically, the brand of the recording paper M is estimated from the obtained values of S01 'and S03' with reference to the recording paper discrimination table. Then, the types of the recording paper M estimated to have the values of S01 'and S03' are stored in the RAM.

  In this case, since the output signal of the light receiver 19 is the detection result at the incident angle θ2 suitable for the brand determination of the gloss coated paper, it is not estimated to be plain paper or the like in step T3 (estimated to be gloss coated paper). It is possible to easily estimate the brand of the recording paper M.

  In the next step T8, the light source 11 'is turned off. When step T8 is executed, the flow ends.

  After performing the recording paper discrimination processing as described above, the processing device 110 sends the brand of the recording paper M estimated in step T5 or step T7 to the control device 2090.

  The control device 2090 adjusts image forming conditions (for example, developing conditions and transfer conditions) according to the estimated brand of the recording paper. Specifically, the specified brand of the recording paper stored in the RAM is read out, and the optimum developing conditions and transfer conditions for the brand of the recording paper are obtained from the developing / transfer table. Then, the developing device including the developing roller and the transfer device including the transfer roller in each station are controlled according to the optimum developing condition and the transferring condition. For example, the transfer voltage and the toner amount are controlled. As image forming conditions, instead of or in addition to the transfer voltage and the toner amount, for example, the developing bias by the developing device, the charging potential by the charging device, the exposure amount by the optical scanning device 2010, etc. may be controlled. In any case, it is preferable that the image forming conditions to be controlled be tabulated and stored in the ROM.

  The user sets the recording paper M for which the brand has been determined on the paper feed tray 2060 or the manual feed tray of the color printer 2000 and prints. In this case, since the image forming process is performed under the optimum image forming condition for the recording paper, a high quality image can be formed on the recording paper.

  The optical sensor 100 according to the present embodiment described above includes a sensor unit including a light source (11, 11 ′), a collimating lens (12, 12 ′), a plurality of light receivers (13, 15, 19), and a polarization filter 14. , A processing device 110 and the like.

  That is, the optical sensor 100 according to the present embodiment irradiates a plurality of (for example, two) linearly polarized light (for example, S-polarized light) having a predetermined polarization direction onto the recording paper as an object from different directions inclined to the recording paper. The irradiating means including the irradiating systems 10 and 10 ', and the detecting means for individually detecting a plurality of lights emitted from the irradiating means and reflected by the recording paper.

  In this case, linearly polarized light can be made incident on the recording paper at a suitable incident angle for each recording paper, and a plurality of reflected lights from the recording paper can be individually detected.

  As a result, it is possible to obtain information for discriminating the recording paper more finely than before.

  Conventionally, the brand is identified by causing light from a light source to enter the recording paper at a unique incident angle and detecting the light reflected thereby. On the other hand, in the present embodiment, by detecting the reflected light of the light incident on the recording paper at a plurality of different incident angles, it is possible to realize a high brand identification accuracy for a plurality of paper types, which has been difficult in the past. Is possible.

  Further, since the detection means includes a plurality of first detection systems (light receivers 15 and 19) individually arranged on the optical paths of a plurality of lights emitted from the plurality of irradiation systems and specularly reflected by the recording paper, Specular reflection light for each irradiation system can be detected.

  Further, the detection means includes a second detection system arranged on the optical path of the light emitted from the irradiation means and diffusely reflected by the recording paper in the direction orthogonal to the surface of the recording paper.

  In this case, the internal diffuse reflection light from the recording paper can be detected with high accuracy, and information for improving the determination accuracy of the recording paper can be acquired.

  The second detection system includes a photodetector (light receiver 13) disposed on the optical path of the light emitted from the irradiation unit and diffused and reflected by the recording paper in a direction orthogonal to the surface of the object, and the light detector. The polarization filter 14 is arranged on the optical path of light between the detector and the recording paper, and transmits a linear polarization component (for example, P polarization component) of a polarization direction orthogonal to a predetermined polarization direction.

  In this case, for example, the P-polarized light component of the internal diffuse reflection light from the recording paper can be detected with high accuracy, and information for improving the determination accuracy of the recording paper can be acquired.

  Further, the detection means includes a third detection system arranged on the optical path of the light emitted from the irradiation means and diffusely reflected by the recording paper in a direction different from the direction orthogonal to the surface of the recording paper.

  In this case, the surface diffuse reflection light from the recording paper can be detected with high accuracy, and information for further improving the determination accuracy of the recording paper can be acquired.

  Further, since the irradiation unit has a light source in each irradiation system, the light amount loss is small and the light utilization efficiency is excellent as compared with the case where the light from the light source is separated into a plurality of systems by using a half mirror.

  Further, since the light source includes the surface emitting laser array, it is possible to emit linearly polarized light having a stable polarization direction. Further, speckle can be reduced by simultaneously lighting a plurality of light emitting units.

  Further, since the optical sensor 100 further includes the processing device 110 that estimates the type and brand of the recording paper based on the output of the detection unit, the recording paper can be discriminated by the optical sensor 100 itself. The optical sensor 100 may not include the processing device 110. In this case, the control device 2090 may control the processing device 110 to determine the recording paper. Further, the control device 2090 may perform a part of the control performed by the processing device 110.

  Further, since the color printer 2000 can appropriately adjust the image forming conditions (for example, developing conditions and transfer conditions) according to the brand of the recording paper estimated by the optical sensor 100, the recording can be performed regardless of the brand of the recording paper. High quality images can be formed on paper.

  Further, the recording paper information measuring method of the present embodiment differs from the recording paper M in the step of irradiating the recording paper M with a plurality of linearly polarized light having a predetermined polarization direction from different directions inclined with respect to the recording paper M. Individually detecting a plurality of light reflected in the direction.

  In this case, linearly polarized light can be made incident on the recording paper at a suitable incident angle for each recording paper, and a plurality of reflected lights from the recording paper can be individually detected.

  As a result, it is possible to obtain information for discriminating the recording paper more finely than before.

  Further, in the irradiation step, since the recording paper M is irradiated with a plurality of linearly polarized lights at different timings, a plurality of reflected lights of each linearly polarized light can be individually and accurately detected in the detecting step. It should be noted that if a plurality of linearly polarized lights are irradiated at the same time, the reflected lights of the plurality of linearly polarized lights will be detected at the same time in the step of detecting, so it is difficult to individually accurately detect the plurality of reflected lights of the respective linearly polarized lights. is there.

  Further, in the detecting step, a plurality of lights (a plurality of specular reflection lights) specularly reflected in different directions on the recording paper M are detected at different timings. Therefore, the recording is performed based on the power of the specular reflection light detected previously. Information for estimating the type of the paper M can be obtained, and information for estimating the brand of the recording paper M can be obtained based on the power of specular reflection light detected later.

  Further, the object discriminating method of the present embodiment includes a first irradiation step of irradiating the recording paper M with linearly polarized light having a predetermined polarization direction from a first direction inclined to the recording paper, and the first irradiation. A first detection step of detecting the light specularly reflected by the recording paper M during the step, and a first estimation step of estimating the type of the recording paper M based on the detection result of the first detection step; A second irradiation step of irradiating the recording paper M with linearly polarized light from a second direction inclined with respect to the recording paper according to the type of the recording paper estimated in the first estimating step; A second detection step of detecting the light specularly reflected by the recording paper M during the irradiation step of, and a second estimation step of estimating the characteristics of the recording paper M based on the detection result of the second detection step. ,including.

  In this case, the recording paper can be discriminated more finely than in the past.

<Modification 1>
By the way, the optical sensor 100 of the above embodiment includes the light source 11 ′ and the collimator lens 12 ′, but instead of this, as in the optical sensor 200 of the modified example 1 shown in FIG. The plurality of (for example, two) mirrors 32 and 33 may be used to irradiate the recording paper M as the determination target with a plurality of (for example, two) incident angles (from the incident direction).

  Here, the light source 11 emits a light beam in a direction parallel to the Z axis. The collimator lens 12 is arranged on the optical path of the light from the light source 11 so that the optical axis is parallel to the Z axis. The beam splitter 31 is arranged on the optical path of light passing through the collimator lens 12 and splits the light into transmitted light and reflected light. The beam splitter 31 is preferably a half mirror that can equalize the amounts of transmitted light and reflected light.

  The mirror 33 bends the optical path of the light beam (transmitted light) that has passed through the beam splitter 31 so that the incident angle on the recording paper is 75 °.

  The mirror 32 bends the optical path of the light beam (reflected light) that has passed through the beam splitter 31 so that the incident angle on the recording paper is 60 °.

  The light receiver 15 receives and detects the surface specular reflection light incident on the recording paper at 75 °, and the light receiver 19 receives and detects the surface specular reflection light incident on the recording paper at 60 °.

  In this case, one light source is sufficient to cause the light flux to enter the recording paper M at two different incident angles, and the cost can be reduced. Further, by adding a beam splitter and a mirror in the same manner, it is possible to make a light beam enter the recording paper M at three or more different incident angles using a single light source.

  Moreover, the optical sensor 200 of the first modification includes a light blocking unit that can selectively block one of the transmitted light and the reflected light from the beam splitter 31.

  This light blocking means includes a light blocking member 250, a first light blocking position where the light blocking member 250 is on the optical path of the transmitted light from the beam splitter 31, and a position on the optical path of the reflected light from the beam splitter 31. And an actuator (not shown) for moving between the two light shielding positions. Here, the first light blocking position is the position on the optical path of the light reflected by the mirror 33, and the second light blocking position is the position on the optical path of the light reflected by the mirror 32.

  The light blocking member 250 may be any member that blocks light, but from the viewpoint of suppressing the return light to the light source 11, it is preferably a member that scatters light or converts light into heat.

  The actuator is not particularly limited as long as it can move the light blocking member 250 between the first and second light blocking positions. For example, it may be a linear actuator that linearly moves the light blocking member 250 or a rotary actuator that rotates the light blocking member 250. The actuator is controlled by the processing device 110.

  Note that a light blocking member for blocking the transmitted light from the beam splitter 31 and a light blocking member for blocking the reflected light may be separately provided. In this case, each light blocking member may be moved by a single actuator or a plurality of actuators.

  Hereinafter, the recording sheet determination process using the optical sensor 200 of the first modification will be described with reference to the flowchart of FIG. The flowchart of FIG. 21 is based on the processing algorithm executed by the processing device 110. The control flow here starts when the user inserts the recording paper M into the slit of the optical sensor 200 and inputs a recording paper determination request to the processing device 110 via an operation panel (not shown) or a personal computer. To be done. Initially, the light blocking member 250 is located at the second light blocking position that blocks the reflected light from the beam splitter 31. That is, here, the second light blocking position is the initial position of the light blocking member 250.

  In the first step U1, the light source 11 is turned on. That is, the plurality of light emitting units of the light source 11 are caused to emit light at the same time. As a result, of the transmitted light and the reflected light from the beam splitter 31, the reflected light is blocked by the light blocking member 250, and the transmitted light is incident on the recording paper M at the incident angle θ1.

  In the next step U2, the type of the recording paper M is estimated based on the output signals of the light receivers 13 and 15. Specifically, the type of the recording paper M is estimated from the relationship between the signal levels S01 and S02 in the output signals of the light receivers 13 and 15 and FIG. More specifically, the recording paper discrimination table is referred to, and the type of the recording paper M is estimated from the obtained values of S01 and S02. Then, the types of recording paper estimated as the values of S01 and S02 are stored in the RAM.

  In the next step U3, it is determined whether the estimated type is plain paper or matte coated paper (hereinafter referred to as "plain paper or the like"). If the determination here is affirmative, the process proceeds to step U4, and if the determination is negative, the process proceeds to step U5.

  In step U4, the brand of the recording paper M is estimated based on the output signals of the light receivers 13 and 15. Since the output signal of the light receiver 15 is the detection result at the incident angle θ1 suitable for brand identification of plain paper or the like, it is possible to easily estimate the brand of the recording paper M estimated to be plain paper or the like. Specifically, with reference to the recording paper discrimination table, the brand of recording paper is estimated from the values of S01 and S02 stored in the RAM in step U2. When step U4 is executed, the flow moves to step U7.

  In step U5, the light blocking member 250 is moved from the second light blocking position to the first light blocking position (the position that blocks the transmitted light from the beam splitter 31). As a result, of the transmitted light and the reflected light from the beam splitter 31, the transmitted light is blocked by the light blocking member 250, and the reflected light is incident on the recording paper M at the incident angle θ2.

  In the next step U6, the brand of the recording paper M is estimated based on the output signals of the light receivers 13 and 19. Specifically, the brand of the recording paper M is estimated from the obtained values of S01 'and S03' with reference to the recording paper discrimination table. Then, the types of the recording paper M estimated to have the values of S01 'and S03' are stored in the RAM.

  In this case, since the output signal of the light receiver 19 is the detection result at the incident angle θ2 suitable for the brand identification of the gloss coated paper, it is not estimated to be plain paper or the like in step U3 (estimated to be gloss coated paper). It is possible to easily estimate the brand of the recording paper M.

  In the next step U7, the light source 11 is turned off. When step U7 is executed, the flow ends.

  After performing the recording paper discrimination processing as described above, the processing device 110 sends the brand of the recording paper M estimated in step U4 or step U6 to the control device 2090.

  The controller 2090 adjusts image forming conditions (for example, developing conditions and transfer conditions) according to the estimated brand of the recording paper, as in the above embodiment.

  The user sets the recording paper M for which the brand has been determined on the paper feed tray 2060 or the manual feed tray of the color printer 2000 and prints. In this case, since the image forming process is performed under the optimum image forming condition for the recording paper, a high quality image can be formed on the recording paper.

  In the modified example 1 described above, the irradiation unit transmits the light from the light source 11 common to at least two (for example, two) irradiation systems among the plurality (for example, two) of irradiation systems and the light from the light sources 11. And a beam splitter 31 (separation optical element) for separating the light into reflected light.

  In this case, it is possible to irradiate the recording paper M with more light flux than the number of light sources, and it is possible to acquire information for improving the discriminating accuracy of the recording paper while reducing cost.

  Further, the irradiation unit further includes a reflection unit including mirrors 32 and 33 for reflecting the transmitted light and the reflected light from the beam splitter 31 toward the recording paper M.

  In this case, the transmitted light and the reflected light from the beam splitter 31 can be incident on the recording paper M at a desired incident angle.

  Further, the irradiation means further has a light shielding means capable of selectively shielding one of the transmitted light and the reflected light from the beam splitter 31, so that the transmitted light and the reflected light are irradiated onto the recording paper M at different timings. The reflected light can be detected at different timings. As a result, information for further improving the discrimination accuracy of the recording paper M can be acquired.

<Modification 2>
Further, as in the optical sensor 300 of the second modification shown in FIG. 12, of the light emitted from the light source 11 and passing through the collimator lens 12, the light (transmitted light) that has passed through the beam splitter 31 is made to go straight to directly record the recording paper. A configuration may be employed in which the light (reflected light) that is incident on M and reflected by the beam splitter 31 is reflected by the mirror 32 toward the recording paper M. In this case, the mirror 33 can be omitted, and the number of parts can be further reduced and the cost can be reduced. Further, in this case, it is preferable to match the emission direction of the light source 11 with a desired incident angle with respect to the recording paper M. Of the light emitted from the light source 11 and passing through the collimator lens 12, the reflected light from the beam splitter 31 is directly incident on the recording paper M, and the transmitted light from the beam splitter 31 is reflected by the mirror 33 toward the recording paper M. You may employ the structure made to. In this case, the mirror 32 can be omitted. Further, in this case, it is preferable that the reflection direction of the reflected light from the beam splitter 31 is adjusted to a desired incident angle with respect to the recording paper M. Further, in any of the above cases, a reflection member may be added, and in short, it is preferable that the incident direction of the irradiation light is finally adjusted to a desired incident angle with respect to the recording paper M.

  By the way, when there is a risk of erroneous paper type discrimination due to the influence of ambient light or stray light, the number of detection systems including light receivers in each detection means may be increased.

  The optical sensor 300 of the second modification also has a light blocking unit including the light blocking member 250 capable of selectively blocking one of the transmitted light and the reflected light from the beam splitter 31 as in the first modification (FIG. 12).

  The recording sheet determination process using the optical sensor 300 of the second modification can be performed by the procedure of the flowchart of FIG. 21, as in the first modification.

<Modification 3>
For example, like the optical sensor 400 of the modification 3 shown in FIG. 13, the light receiver 17 may be further provided. Reflected light in which surface diffuse reflected light and internal reflected light are mixed is incident on the light receiver 17. At the position of the light receiver 17, the light amount of the internal reflected light is much smaller than the light amount of the surface diffuse reflected light, and therefore the received light amount of the light receiver 17 can be regarded as the light amount of the surface diffuse reflected light.

  The angle ψ4 formed by the line L4 connecting the center of illumination and the center of the light receiver 17 and the surface of the recording paper is 120 °, for example. Here, the center of the light source (11, 11 ′), the center of illumination, the center of the polarization filter 14, and the center of each light receiver are on substantially the same plane, but even if they are offset from each other in the Y-axis direction. good.

  In this case, the brand identification process performed by the processing device 110 will be described below.

  In the following, the signal levels in the output signals of the light receivers 17 and 19 when the light flux from the light source 11 is applied to the recording paper are “S4” and “S3”, and the light flux from the light source 11 ′ is the recording paper. The signal levels of the output signals of the light receivers 17 and 15 when the light is irradiated on the light are referred to as “S4 ′” and “S2 ′”.

(1) A plurality of light emitting units of the light source 11 are turned on at the same time.
(2) The values of S1, S2, S3 and S4 are obtained from the output signals of the light receivers 13, 15, 17, and 19.
(3) Turn off the plurality of light emitting units of the light source 11.
(4) A plurality of light emitting units of the light source 11 'are turned on at the same time.
(5) The values of S1 ′, S2 ′, S3 ′ and S4 ′ are obtained from the output signals of the photo detectors 13, 15, 17, and 19.
(6) Turn off the plurality of light emitting units of the light source 11 '.
(7) The processing device 110 identifies the brand of the recording paper based on S3 / S1 and S4 / S2 if the value of S1 is below a certain value, and if the value of S1 is above a certain value, S3 ′ / Based on S1 ', S4' / S3 ', the brand of the recording paper is specified (6) The determination result is notified to the control device 2090. Then, the brand identification process ends.

  In this case, regarding recording papers of a plurality of brands compatible with the color printer 2000, S3 / S1, S4 / S2, S3 ′ / S1 ′, and S4 are previously prepared for each brand of recording papers in a pre-shipping process such as an adjusting process. “/ S3” is measured, and the measurement result is recorded in the processing device 110 as a “recording paper discrimination table”. FIG. 14 shows the values of S4 / S1 and S3 / S2 for each brand as an example.

  In this way, a plurality of (two) light receivers for individually detecting a plurality (for example, two) of diffused lights reflected in different directions are provided, and the ratio of output values of the plurality of light receivers is calculated. By discriminating the recording paper using the value, it is possible to discriminate accurately even if there is ambient light or stray light.

  Further, in this case, the control device 2090 roughly narrows down the paper type using S1 and S2 or S1 ′ and S2 ′, and discriminates the brand of the recording paper using S4 / S1 and S3 / S2. Is also good.

  Further, in this case, the control device 2090 roughly narrows down the paper types using S1 and S2 or S1 ′ and S2 ′, and uses S4 ′ / S1 ′ and S3 ′ / S2 ′ to select the brand of recording paper. May be determined.

  Further, in this case, the control device 2090 roughly narrows down the paper types by using S1, S2, S1 ′ and S2 ′, and S4 / S1 and S3 / S2 and S4 ′ / S1 ′ and S3 ′ / S2 ′ The brand of the recording paper may be discriminated by using.

  Although S4 / S1 is used here as the calculation method using S1 and S4, the calculation method is not limited to this. Similarly, the calculation method using S2 and S3 is not limited to S3 / S2.

  Although S4 '/ S1' is used here as the calculation method using S1 'and S4', the present invention is not limited to this. Similarly, the calculation method using S2 'and S3' is not limited to S3 '/ S2'.

  15 (A) and 15 (B) show the results of examining the influence of ambient light in the case of making a decision using only S1 and S2 and the case of making a decision using S4 / S1 and S3 / S2. It is shown. When performing discrimination using only S1 and S2, as shown in FIG. 15 (A), if there is ambient light, the detection value in each light receiving system becomes large, and there is a risk of erroneous discrimination. On the other hand, in the case of making a determination using S4 / S1 and S3 / S2, as shown in FIG. 15B, S4 / S1 and S3 / S2 are almost the same as when there is no ambient light, even when there is ambient light. It is possible to make a correct decision without changing.

  By the way, in the above-mentioned embodiment and each modification, since each light source has the surface emitting laser array which emits linearly polarized light, the polarization filter for making the emitted light linearly polarized light is unnecessary. Further, since the emitted light can be easily parallelized and a compact light source having a plurality of light emitting portions can be realized, the optical sensor 100 can be downsized and the cost can be reduced.

  Further, when the surface emitting laser array is used, high-density integration, which has been difficult with the conventionally used LED or the like, can be realized. Therefore, since all the laser light can be concentrated near the optical axis of the collimator lens, it is possible to make a plurality of light beams substantially parallel while keeping the incident angle constant, and it is possible to easily realize the collimator optical system.

  Further, since each light source has a plurality of light emitting parts, by turning on all the light emitting parts at the same time, it is possible to increase the light amount and the transmitted light amount of the P-polarized component included in the internally reflected light.

  By the way, the diffuse reflection light includes A: “S-polarized light reflected on the surface”, B: “S-polarized light reflected on the inside”, and C: “P-polarized light reflected on the inside”. Of these, "P-polarized light reflected inside" is separated by a polarization filter and the amount of light thereof is detected, whereby the determination can be subdivided, but irradiation with a high amount of light is required for the following reasons.

  When the irradiation light is S-polarized light, the ratio of “P-polarized light reflected inside” is about 40% at maximum in the diffuse reflection light (A + B + C). An inexpensive polarizing filter mounted on a general optical sensor has a low transmittance and is attenuated to about 80% by the polarizing filter. Therefore, the “P-polarized light reflected inside” is attenuated when it is separated by the polarization filter, and becomes about 30%.

  In the conventional optical sensor, the type of the recording paper is discriminated from the recording papers of about 2 to 3 types (for example, coated paper and plastic sheet) according to the light amount of the diffuse reflection light (A + B + C).

  In the above-described embodiment and each modification, the type of the recording paper is discriminated from at least 10 types of the recording paper only by the “P-polarized light reflected inside”. That is, more than five times the detailed paper discrimination is performed as compared with the conventional discrimination of two types of recording paper. Therefore, higher resolution is required with a smaller amount of light than in the past. However, if a photodetector with high resolution is used, it is possible to discriminate even with a low light amount, but this leads to an increase in cost.

  Therefore, in the above-described embodiment and each modified example, high resolution is obtained by increasing the irradiation light amount. Specifically, as described above, since the internal diffuse reflection light amount is attenuated to substantially 30% of the diffuse reflection light (A + B + C), the irradiation light amount needs to be 3.3 times the conventional light amount. . Further, in order to perform the paper discrimination which is five times as detailed as the conventional one, it is necessary to irradiate a light amount of about 3.3 × 5 times as much as the conventional one. As described above, it is necessary to increase the irradiation light amount in proportion to the determination of many types of recording paper.

  In the above-described embodiment and each modified example, since S-polarized light is emitted, when a non-polarized light source such as an LED is used, it is necessary to make linearly polarized light through a polarizing filter before irradiation. At this time, since an inexpensive polarization filter similar to the above is used, the amount of light applied to the recording paper is about 40% (= 50% (cut amount of P-polarized light) × 80% of the amount of light emitted from the LED. (Attenuation at the polarization filter)). Therefore, in the case of the LED light source, the irradiation light amount of 40 times (= 3.3 × 5 ÷ 0.4) or more as compared with the conventional case is required.

  However, the irradiation light quantity of an inexpensive LED is about several mW (1 mW as a typical value), and it is difficult to secure the irradiation light quantity of at least 40 mW or 50 mW or more. On the other hand, in the surface-emitting laser array, it is easy to secure a desired irradiation light amount by turning on a plurality of light-emitting units at the same time. Therefore, in the surface emitting laser array, it is possible to secure the irradiation light amount necessary when the number of types of paper is discriminated more than before.

  Further, since each light source has a plurality of light emitting units, the contrast of the speckle pattern of the reflected light can be increased by turning on the plurality of light emitting units at the same time as compared with the case where only one light emitting unit is turned on. The ratio can be reduced and the discrimination accuracy can be improved.

  Further, since the surface emitting laser array is used, more stable irradiation of linearly polarized light becomes possible. This makes it possible to accurately detect the light amount of the P-polarized component contained in the internally reflected light.

  Since the color printer according to the above-described embodiment and each modification includes the optical sensor 100, as a result, a high-quality image can be formed. Further, the conventional troublesomeness of manual setting and printing failure due to setting error are eliminated.

  In addition, in the above-described embodiment and each modified example, the case where the light irradiated on the recording paper is S-polarized in the optical sensor has been described, but the invention is not limited to this, and the light irradiated on the recording paper is P light. It may be polarized light. However, in this case, a polarization filter that transmits S-polarized light is used instead of the polarization filter 14.

  Further, in the above-described embodiment and each modified example, at least some of the light emitting portions of the plurality of light emitting portions in the surface emitting laser array may be different from other light emitting portion spacings (see FIG. 16).

  Further, in the above-described embodiment and each modified example, the case where each light source has a plurality of light emitting units has been described, but the present invention is not limited to this, and at least one light source has a single light emitting unit. Is also good.

  Further, in the above-described embodiment and each modification, the two light sources 11 and 11 'are turned on at different timings, but the lighting timings of the two light sources 11 and 11' may be at least partially overlapped. In this case, the same effect can be obtained.

<< Variation 4 >>
Further, as in the optical sensor 500 of the modification 4 shown in FIG. 17, a conventional LD (Laser Diode) or LD array may be used as the light source (11, 11 ′) instead of the surface emitting laser array. good. However, in this case, as shown in FIG. 17 as an example, a polarization filter 25 that transmits only linearly polarized light in a predetermined polarization direction out of the light from the light source 11, and a predetermined polarization out of the light from the light source 11 ′. A polarization filter 25 'that transmits only the linearly polarized light in the direction is required.

  The optical sensor 500 of the modified example 4 described above, each light source includes an LD, and a polarized light that transmits a linearly polarized light of a predetermined polarization direction of the light on the optical path of the light between the LD and the recording paper M. The filters are in place.

  In this case, the information for identifying the recording paper can be obtained using the conventional LD.

  Further, in the above-described embodiment and each modification, it is preferable that the condenser lens is arranged in front of at least one light receiver. In this case, the change in the amount of light detected by the light receiver can be reduced.

  Further, in the above-described embodiment and each modification, the processing device 110 notifies the control device 2090 of the signal level in the obtained output signal of each light receiver, and the control device 2090 side discriminates the brand of the recording paper. good. In this case, the "recording paper discrimination table" is stored in the ROM of the control device 2090.

  Further, in the above-described embodiment and each modified example, the optical sensor 100 may have a built-in power source. In this case, the power supply from the color printer 2000 is unnecessary.

  In addition, in the above-described embodiment and each modified example, data may be exchanged between the optical sensor 100 and the control device 2090 wirelessly.

  Further, in the above-described embodiment and each modified example, the optical sensor 100 may include a paper sensor and an LED that is turned on when the paper sensor detects a recording paper. In this case, the operator can surely and easily know that the recording paper has been inserted to the predetermined position.

  Further, in the above-described embodiment and each modified example, the optical sensor 100 may acquire the output signal of each light receiver at every predetermined sampling time. For example, when P data are obtained for each light receiver, P output levels may be averaged for each light receiver and the average value may be used as the measured value.

  By the way, reproducibility of measurement is important for an optical sensor that discriminates a recording sheet based on the amount of reflected light. In an optical sensor that discriminates a recording paper based on the amount of reflected light, a measurement system is installed on the assumption that the measurement surface and the surface of the recording paper are on the same plane at the time of measurement. However, in some cases, the surface of the recording paper is inclined or lifted with respect to the measurement surface due to the reasons such as bending and vibration, and the surface of the recording paper may not be flush with the measurement surface. In this case, the amount of reflected light changes, and stable and detailed determination is difficult. Here, specular reflection will be described as an example.

  FIG. 18A shows the case where the measurement surface and the surface of the recording paper are on the same plane. At this time, the photodetection system can receive specular reflection.

  FIG. 18B shows a case where the surface of the recording paper is inclined by the angle α with respect to the measurement surface. At this time, if the positional relationship between the light irradiation system and the light detection system is the same as in the case of FIG. 18A, the light detection system receives light in a direction deviated from the specular reflection direction by 2α. Since the reflected light intensity distribution moves with the shift, if the distance between the center position of the irradiation region and the photodetection system is L, the photodetection system receives light at a position deviated from the regular reflection light receiving position by L × tan2α. It will be. Further, the actual incident angle deviates from the specified incident angle θ by α, and the reflectance from the recording paper changes. Therefore, the amount of detected light changes, and as a result, it becomes difficult to make a detailed determination.

  Further, FIG. 18C shows a case where the surface of the recording paper is displaced from the measurement surface by d in the height direction, that is, the Z-axis direction. At this time, if the positional relationship between the light irradiation system and the light detection system is the same as in the case of FIG. 18A, the reflected light intensity distribution moves due to the shift, so that the light detection system moves from the regular reflection light receiving position. Light is received at a position shifted by 2d × sin θ. Therefore, the amount of detected light changes, and as a result, it becomes difficult to make a detailed determination.

  In the case of FIG. 18 (B) and FIG. 18 (C), a condenser lens is arranged in front of the photodetector of the photodetection system with respect to the movement amount so that the photodetection system reliably detects specularly reflected light. Even if the reflected light intensity distribution moves, it can be dealt with by condensing.

  Alternatively, even if a photodiode (PD) having a sufficiently large light receiving area is used for the light receiver or the beam diameter of the irradiation light is narrowed, it is possible to eliminate the inconvenience when the surface of the recording paper is not flush with the measurement surface. You can

  Further, an array of PDs may be used as the light receiver, and the light receiving area may be sufficiently large with respect to the amount of movement of the reflected light intensity distribution. In this case, even if the reflected light intensity distribution moves, the maximum signal of the signals detected by each PD may be the signal of the specularly reflected light. Further, when PDs are arrayed, by reducing the light receiving areas of the individual PDs, fluctuations in the output due to the deviation of the centers of the specularly reflected light and the light receiving areas can be reduced, so that more accurate detection can be performed. it can.

  Here, for the sake of convenience, the regular reflection is described, but regarding the surface diffuse reflection, the internal diffuse reflection, and the transmitted light, the detected light amount changes due to the deviation between the measurement surface and the recording paper surface, but in the same manner as the case of the regular reflection. Can respond.

  Further, in the above-described embodiment and each modified example, the case where there is one sheet feeding tray has been described, but the present invention is not limited to this, and there may be a plurality of sheet feeding trays.

  Further, the object to be discriminated by using the optical sensor of the present invention is not limited to the recording paper, and in short, it may be any object that can optically discriminate the material (for example, using the optical sensor).

  Further, in the above-described embodiment and each modified example, the case where the color printer 2000 is used as the image forming apparatus has been described, but the present invention is not limited to this, and may be, for example, an optical plotter or a digital copying apparatus.

  Further, in the above-described embodiment and each modified example, the case where the image forming apparatus has four photosensitive drums has been described, but the present invention is not limited to this.

  The optical sensor 100 can also be applied to an inkjet type image forming apparatus that forms an image by spraying ink on a recording sheet.

  The thought process by which the inventors came up with the above-described embodiment and each modified example will be described below.

  An image forming apparatus such as a digital copying machine or a laser printer transfers a toner image onto the surface of a recording medium typified by printing paper and heats and pressurizes it under a predetermined condition to fix the image to form an image. Image forming conditions such as phenomenon conditions, transfer conditions, and fixing conditions must be taken into consideration in image formation. Particularly, in order to perform high quality image formation, the image forming conditions are individually set according to the recording medium. There is a need.

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

  Furthermore, with recent advances in image forming apparatuses and diversification of expression methods, there are more than several hundred types of recording media, even printing paper, and there are differences in specifications such as basis weight and thickness for each type. There are various brands. In order to form a high quality image, it is necessary to set fine image forming conditions according to each of these brands.

  In addition, in recent years, the number of brands of plain paper, gloss coated paper, matte coated paper, coated paper typified by art coated paper, plastic sheet, and special paper having an embossed surface is increasing.

  In the current image forming apparatus, it is necessary for the user to set the brand of paper and the fixing condition for each tray at the time of printing. For this reason, the user is required to have knowledge for identifying the paper type, and it is troublesome that the user needs to input the setting contents corresponding to the paper type each time. If the setting contents are incorrect, the optimum image cannot be obtained.

  By the way, Patent Document 1 discloses a surface property identification device including a sensor for contacting the surface of a recording material and scanning the surface to identify the surface property of the surface of the recording material.

  Japanese Unexamined Patent Application Publication No. 2004-242242 discloses a printing apparatus that determines a paper type from a pressure value detected by a pressure sensor coming into contact with the paper.

  Patent Document 3 discloses a recording material discrimination device that discriminates the type of recording material using reflected light and transmitted light.

  Patent Document 4 discloses a sheet material quality determination device that determines the material of a moving sheet material based on the amount of reflected light reflected on the surface of the sheet material and the amount of transmitted light transmitted through the sheet material.

  Patent Document 5 discloses an image forming apparatus having a determination unit that determines the presence / absence of a recording material housed in a paper feed unit and the presence / absence of a paper feed unit based on a detection output from a reflective optical sensor. There is.

Patent Document 6 discloses an image forming apparatus that irradiates a recording medium with light and detects the light amounts of two polarized components of the reflected light to determine the surface property of the recording medium.
Patent Document 7 discloses an optical sensor that identifies a brand of recording paper by using a P-polarized component of surface specular reflection light and internal diffuse reflection light.

  However, in the sheet material quality determination device disclosed in Patent Document 4 and the image forming apparatus added to Patent Documents 5 and 6, it is possible to identify (determine) uncoated paper / coated paper / OHP. Only the difference in the sheet, it was not possible to specify the brand required for high quality image formation.

  By the way, FIG. 6 shows the theoretical values of the glossiness (θ = 60 °, 75 °, 80 °) at the incident angle θ degrees with respect to the glossiness at the incident angle 60 degrees, and the incident angle with respect to the glossiness at the incident angle 60 degrees. It is a graph showing the measured value for each brand of the recording paper of the glossiness at 75 degrees.

  Comparing the differences between brands on each axis, θ = 60 ° is effective in discriminating brands on the recording paper when the differences between brands on the horizontal axis are large, and θ = 60 ° when the differences between brands on the vertical axis are large. It is shown that 75 ° is effective. Further, as shown in FIG. 6, the difficulty of brand identification of plain paper / gloss coated paper / matte coated paper differs depending on the incident angle θ of the irradiation light on the recording paper. As an example, plain paper is easier to discriminate as the incident angle θ of irradiation light is larger, and gloss-coated paper is easier to discriminate as the incident angle θ of irradiation light is smaller. However, the optical sensor disclosed in Patent Document 7 is configured such that the incident angle of the irradiation light from the light source on the recording paper has a unique value. Therefore, there is room for improvement in the configuration of the optical sensor disclosed in Patent Document 7 for accurately discriminating many types of printing paper.

  Therefore, the inventors have devised the above-described embodiment and each modified example after earnestly studying.

  11, 11 '... Light source, 13 ... Photodetector (photodetector), 14 ... Polarization filter (polarizing optical element, part of detection system), 15 ... Photodetector (detection system), 17 ... Photodetector (detection system) , 19 ... Light receiver (detection system), 25, 25 '... Polarization filter (separate polarization optical element), 31 ... Beam splitter (separation optical element), 32 ... Mirror (part of reflection means), 33 ... Mirror ( Part of the reflection means), 110 ... Processing device, 2000 ... Color printer (image forming device), M ... Recording paper (object, recording medium).

JP, 2002-340518, A JP, 2003-292170, A JP, 2005-156380, A Japanese Unexamined Patent Publication No. 10-160687 JP, 2006-062842, A JP, 11-249353, A JP2012-128393A

Claims (10)

Irradiation means including a plurality of irradiation systems for irradiating an object with linearly polarized light of a predetermined polarization direction from different directions inclined with respect to the object,
A detection means for individually detecting a plurality of lights emitted from the irradiation means and reflected in different directions on the object,
The said irradiation means has a light source common to at least 2 irradiation systems among said some irradiation system, The said light source is an optical sensor which is a surface emitting laser array which a several light emission part emits simultaneously.   The detection means includes a plurality of detection systems individually arranged on an optical path of a plurality of lights emitted from the irradiation means and specularly reflected in different directions by the object. The optical sensor described. The detection means is
A photodetector disposed on the optical path of light that is irradiated from the irradiation means and is diffusely reflected in the object in a direction orthogonal to the surface of the object,
A polarizing optical element which is arranged on an optical path of light between the object and the photodetector and which transmits a linearly polarized light component of a polarization direction orthogonal to the predetermined polarization direction. Item 3. The optical sensor according to Item 1 or 2.   The detection means includes a detection system arranged on the optical path of light emitted from the irradiation means and diffusely reflected by the object in a direction different from the direction orthogonal to the surface of the object. The optical sensor according to claim 1.   The optical sensor according to claim 1, wherein the irradiation unit has a separation optical element that separates light from the light source into transmitted light and reflected light.   The optical sensor according to claim 5, wherein the irradiation unit further includes a light shielding unit capable of selectively shielding one of the transmitted light and the reflected light from the separation optical element.   7. The irradiating means further comprises a reflecting means for reflecting at least one of the transmitted light and the reflected light from the separation optical element toward the object, and the irradiating means further comprises: Optical sensor.   The optical sensor according to any one of claims 1 to 7, further comprising a processing device that estimates a type and a characteristic of the target object based on an output of the detection unit. In an image forming apparatus that forms 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. First irradiating means for irradiating the object with linearly polarized light of a predetermined polarization direction at a first incident angle; second irradiating means for irradiating linearly polarized light at a second incident angle smaller than the first incident angle; No. 1 first photodetector capable of receiving light emitted from the irradiation unit and specularly reflected by the object; and second photodetector capable of receiving light emitted from the second irradiation unit and specularly reflected by the object. And a third photodetector capable of receiving the light diffusely reflected in the direction orthogonal to the surface of the object by the irradiation by the first irradiation unit or the second irradiation unit. An object determination method using an optical sensor,
The object is irradiated with light at the first incident angle by the first irradiation means, the light specularly reflected by the object is detected by the first photodetector, and the light is orthogonal to the surface of the object. A first detection step of detecting the light diffusely reflected in the direction described above by the third photodetector;
The object is irradiated with light at the second incident angle by the second irradiation means, the light specularly reflected by the object is detected by the second photodetector, and is orthogonal to the surface of the object. A second detection step of detecting the light diffusely reflected in the direction of
A first estimation step of estimating the type of the object based on the detection result of the first detection step;
If the estimated type is plain paper, the brand of the object is estimated based on the result of the first detection step without performing the second detection step, and the estimated type is not plain paper. If the object identification method comprising a second estimation step, the estimating stocks of the object based on the result by the second detection step.