JP2017020870A - Optical sensor, image forming apparatus, object information measurement method, and object determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain information for determining an object in detail compared with a prior art.SOLUTION: An optical sensor 100 comprises: irradiation means including a plurality of (for example, two) irradiation systems 10 and 10' that irradiate a recording sheet being an object with linearly polarized light (for example, s-polarized light) in a predetermined polarization direction from directions inclined with respect to the recording sheet and different from each other; and detection means that individually detects a plurality of rays of light emitted from the irradiation means and reflected on the recording sheet. In this case, the optical sensor can obtain information for determining the object in detail compared with a prior art.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical sensor, an image forming apparatus, an object information measuring method, and an object discriminating method, and more specifically, an optical sensor used for discriminating an object, an image forming apparatus including the optical sensor, and an object The present invention relates to an object information measurement method used for discrimination and an object discrimination method for discriminating an object.

  In recent years, devices and the like for discriminating objects have been actively developed (see, for example, Patent Documents 1 to 7).

  However, the devices and the like disclosed in Patent Documents 1 to 7 have room for improvement with regard to obtaining information for finely discriminating an object.

  The present invention includes an irradiation unit including a plurality of irradiation systems that irradiate a target with linearly polarized light having a predetermined polarization direction from different directions inclined with respect to the target, and the target irradiated with the target by the target. An optical sensor comprising: a detecting unit that individually detects a plurality of lights reflected in different directions.

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

1 is a diagram for describing a schematic configuration of a color printer according to an embodiment of the present invention. FIG. 1 is an external view of an optical sensor 100. FIG. 2 is a diagram for explaining a configuration of an optical sensor 100. FIG. It is a figure for demonstrating 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. 6 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 regular reflection light, FIG. 8B is a diagram for explaining surface diffuse reflection light, and FIG. 8C is a diagram explaining internal diffuse reflection light. It is a figure for doing. It is a figure for demonstrating the light received with the light receivers 13 and 15. FIG. It is a figure for demonstrating the relationship between signal level S1, S2 and the brand of a recording paper. It is a figure for demonstrating the structure of the optical sensor of the modification 1. FIG. It is a figure for demonstrating the structure of the optical sensor of the modification 2. FIG. It is a figure for demonstrating the structure of the optical sensor of the modification 3. FIG. It is a figure for demonstrating the relationship between S4 / S1 and S3 / S2, and the brand of a recording paper. FIGS. 15A and 15B are diagrams (No. 1 and No. 2) for explaining the influence of disturbance light, respectively. The figure for demonstrating the other example of a surface emitting laser array It is a figure for demonstrating the structure of the optical sensor of the modification 4. FIGS. 18A to 18C are diagrams (No. 1 to No. 3) for explaining the change in the detected light amount due to the deviation between the measurement surface and the recording paper surface, respectively. FIGS. 19A and 19B are diagrams (No. 2 and No. 3) for explaining that there is an incident angle of irradiation light that can be easily determined (identified) depending on the type of recording paper. is there. It is a flowchart for demonstrating a recording paper discrimination | determination process. 10 is a flowchart for explaining a recording sheet discrimination process according to a first modification.

  A color printer 2000 according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, modifications will be described as appropriate.

  FIG. 1 shows a schematic configuration of a color printer 2000 according to an embodiment.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image on a recording medium by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical sensor 100, an optical scanning device 2010, and 4. Four photosensitive drums (2030a, 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), and 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 program described in a code decodable by the CPU, a ROM storing various data used when executing the program, a RAM as a working memory, an amplifier circuit, An AD conversion circuit that converts an analog signal into a digital signal is included. The 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. It should be noted that optimum development conditions and transfer conditions are stored in the ROM as “development / transfer tables” for a plurality of brands of recording paper that the color printer 2000 can handle as recording media.

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

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

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

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

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. Each photosensitive drum is rotated 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. Each surface of the photosensitive drum is scanned. Thereby, a latent image corresponding to the image information is formed on the surface of each photosensitive drum. That is, here, the surface of each photosensitive drum is a surface to be scanned. Each photosensitive drum is an image carrier. The latent image formed here moves in the direction of the corresponding developing roller as the photosensitive drum rotates.

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

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

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

  In the fixing device 2050, heat and pressure are applied to the recording paper, whereby the toner is fixed on the recording paper. Here, the recording paper on which the toner is fixed 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 100 is disposed outside the printer housing 2200 and near the operation panel, and is used to determine the brand of the recording paper.

  This optical sensor 100 is a so-called stationary optical sensor. As shown in FIG. 2 as an example, the optical sensor 100 has a quadrangular pyramid shape, 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 that. Further, inside the optical sensor 100, a processing device 110 for discriminating brands of recording paper is provided. In the present 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 defined as the Z-axis direction, and the direction in which the recording paper M is inserted into the slit is defined as the + X direction.

  As shown in FIG. 3, the optical sensor 100 includes a plurality (for example, two) of light sources (11, 11 ′), a plurality (for example, two) collimating lenses (12, 12 ′), and a plurality (for example, three). Sensor unit including the light receiving device (13, 15, 19) and the polarizing filter 14, the processing device 110, and the like.

  Here, the first irradiation system including the light source 11 and the collimating lens 12 and the second irradiation system including the light source 11 ′ and the collimating lens 12 ′ constitute irradiation means for irradiating the recording paper M with light. Yes. Further, a detection means for individually detecting a plurality of reflected lights from the recording paper M by a detection system including the light receiver 15, a detection system including the light receiver 19, and a detection system including 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.

  Each light source is disposed so that the recording paper M is irradiated with S-polarized light. In addition, incident angles θ1 and θ2 (see FIG. 5) of the light fluxes from the two light sources 11 and 11 ′ to the recording paper M are θ1 = 75 ° and θ2 = 60 ° as an example.

Incidentally, FIG. 6 shows a gloss measurement value (horizontal axis in FIG. 6) when measuring at an incident angle of 60 ° with respect to plain paper, matte coated paper, and gloss coated paper, and an incident angle of 75 °. The glossiness measurement value (vertical axis in FIG. 6) when 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 representing the surface roughness.

  Here, each point shows the measured gloss value of a different paper brand. Precisely, even for the same brand, the glossiness is slightly different for each sheet of paper, so each point represents a representative value of the glossiness measurement result of each paper brand.

  In FIG. 6, when the incident angle is 60 ° and the incident angle is 75 °, the glossy measurement values are more widely distributed and the difference between the glossy measurement values is large for plain paper and matte coated paper. In the case of ° (shallow angle with respect to the paper), it can be seen that the brand (feature) is easy to distinguish. The “difference between measured gloss values” means the absolute value of the difference between the representative value of gloss of a brand A and the representative value of gloss of a brand B.

  On the other hand, for gloss coated paper, brands (features) are distinguished when the measured gloss value is more widely distributed and the difference between the measured gloss values is large at an incident angle of 60 ° (a deep angle with respect to the paper). It turns out that it is easy to do.

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

  As can be seen from FIG. 19A and FIG. 19B, the denser the distribution of the points in the horizontal direction indicating the glossiness measurement value, the harder it is to discriminate, and the more sparse, the easier it is to discriminate.

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

  Returning to FIG. 5, each collimating lens is disposed on the optical path of the light beam from the corresponding light source, and the light beam is made substantially parallel light. The light flux through each collimating lens illuminates the recording paper M. In the present specification, the center of the illumination area on the surface of the recording paper M is abbreviated as “illumination center”. Further, the light flux that passes through each collimating lens is also referred to as “irradiation light”.

  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 center of illumination is referred to as the incident surface of the recording paper M. And That is, the plane including the illumination center and parallel to the XZ plane is the incident plane on the recording paper M.

  In this specification, the expressions S-polarized light and P-polarized light are used for reflected light as well as incident light on the recording paper M. For the sake of easy understanding, this description is based on the incident light incident on the recording paper M. The expression is based on the polarization direction, and light having the same polarization direction as that of incident light (here, S-polarized light) in the incident plane is referred to as S-polarized light, and light having a polarization direction orthogonal thereto is referred to as P-polarized light.

  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. As shown in FIG. 7, the angle ψ1 formed by the line L1 connecting the illumination center, the center of the polarizing 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 disposed on the + X side of the illumination center with respect to the X-axis direction. The angle ψ2 formed by the line L2 connecting the illumination center and the center of the light receiver 15 and the surface of the recording paper M is 170 °.

  The light receiver 19 is disposed on the + X side of the illumination center with respect to the X-axis direction. The angle ψ3 formed by the line L3 connecting the illumination center 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 illumination, the center of the polarizing 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. However, they may be shifted from each other in the Y-axis direction.

  Further, a light source that irradiates 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.

  By the way, the reflected light from the recording paper when the recording paper is illuminated can be divided into reflected light reflected on the surface of the recording paper and reflected light reflected on the inside of the recording paper. Further, the reflected light reflected on the surface of the recording paper can be divided into specularly reflected light and diffusely reflected light. Hereinafter, for the sake of convenience, the reflected light that is regularly reflected on the surface of the recording paper 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” (FIGS. 8A and 8B). )reference).

  The surface of the recording paper is composed of a flat portion and a slope portion, and the smoothness of the recording paper 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, when the recording paper is a general printing paper, the reflected light from the inside of the recording paper is scattered only in the fibers inside the recording paper and thus becomes only the diffuse reflected light. Hereinafter, for convenience, the reflected light from the inside of the recording paper is also referred to as “internally reflected light or internally diffused reflected light” (see FIG. 8C). Similar to the surface diffuse reflection light, the internal reflection light is also a reflection light that is completely scattered and reflected, and the reflection direction can be considered to be isotropic.

  The polarization directions of the surface regular reflection light and the surface diffuse reflection light toward the light receiver are the same as the polarization direction 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 the 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 the direction of any light receiver.

  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. This is presumably because the light that has entered the inside of the recording paper passes through the fiber, rotates while being scattered multiple times, and the polarization direction rotates.

  Reflected light in which surface diffuse reflected light and internal reflected light are mixed enters the polarizing filter 14 (see FIG. 9). In FIG. 9, for convenience, the light source 11 ′, the collimating lens 12 ′, and the light receiver 19 are omitted.

  Since the surface diffuse reflection light incident on the polarizing filter 14 is the same S-polarized light as the incident light, it is shielded by the polarizing filter 14. On the other hand, since the internally reflected light includes both S-polarized light and P-polarized light, the P-polarized light component is transmitted through the polarizing filter 14. That is, the P polarization component included in the internally reflected light is received by the light receiver 13. 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 contained 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 internally reflected light has a correlation with the thickness and density of the recording paper. This is because the amount of P-polarized internally reflected light depends on the path length when passing through the fibers of the recording paper.

  Only a part of the surface regular reflection light and the surface diffuse reflection light and the internal diffuse reflection light are incident on the light receivers 15 and 19. That is, the surface regular reflection light is mainly incident on the light receivers 15 and 19.

  The light receivers 13, 15, and 19 each output an electrical signal (current signal) corresponding to the amount of received light to the processing device 110. In the following, it is assumed that the signal level in the output signal of the light receiver 13 and the signal level in the output signal of the light receiver 15 are “S2” when the recording paper is irradiated with the light flux from the light source 11. 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 recording paper is “S1 ′”, and the signal level in the output signal of the light receiver 19 is “S3 ′”.

  FIG. 10 shows measured values of S1 and S2 as an example for 30 brands of recording paper sold in the country. 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 candidate brands among a plurality of brands narrowed down only by the measured values of S1 and S2. FIG. 10 shows only the relationship between each brand and the measured values of S1 and S2 when the paper type of the discrimination target is plain paper as an example, but there is a similar relationship with gloss paper and the like.

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

The work performed by the worker during the brand determination process will be described.
1. The recording paper M is inserted into the slit of the optical sensor 100.
2. A determination processing request is input via 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 predetermined time (for example, about 5 seconds), the recording paper M is pulled out from the slit of the optical sensor 100.

When receiving the discrimination processing request, the processing device 110 starts the brand discrimination processing.
(1) A plurality of light emitting units of the light source 11 are turned on simultaneously.
(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 simultaneously.
(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 specifies (estimates) the brand of the recording paper based on S1 and S2 if the value of S1 is not more than a certain value, and if the value of S1 is not less than the certain value, S1 ′ and S3. (8) The brand of the specified recording paper is stored in the RAM, and the paper type discrimination process is terminated.

  A process for specifying a brand will be described with reference to examples of S1 and S2. In FIG. 10, for example, if the measured values of S1 and S2 are “」 ”, it is identified as a brand D. Further, if the measured values of S1 and S2 are “■”, the closest brand C is identified. Further, if the measured values of S1 and S2 are “♦”, it is either the brand A or the brand B. In this case, for example, the difference between the average value and the measured value for the brand A and the difference between the average value and the measured value for the brand B are calculated, and the brand with the smaller calculation result is specified. Good. Or, for example, assuming that it is a brand A and recalculating the variation including the measurement value, and assuming that it is the brand B, recalculating the variation including the measurement value and recalculating the variation. 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, 11 ′ is not limited to this. Further, the two light sources 11, 11 'may be turned on simultaneously. Further, when the brand is specified based on S1 and S2 when S1 is equal to or smaller than a certain value, the brand may be further narrowed down 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 using S1 or S2. The determination result is notified to the control device 2090. Then, the brand identification process is terminated.

  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 brand of the determined recording paper is displayed on the display unit of the operation panel, the operator sets the recording paper whose brand has been identified 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 a key on the operation panel.

  Upon receiving a print job request from the user, the control device 2090 reads the brand of the recording paper stored in the RAM, and obtains development conditions and transfer conditions optimal for the brand of the recording paper from the development / transfer table.

  Then, the control device 2090 controls the developing device and the transfer device at each station according to the optimum developing 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.

  Conventionally, the glossiness of the surface of the recording paper is detected from the amount of specularly reflected light, and the smoothness of the surface of the recording paper is detected from the ratio of the amount of specularly reflected light and the amount of diffusely reflected light to identify the recording paper. It was. However, the accuracy of brand discrimination of plain paper, gloss coated paper, and mat coated paper varies depending on the incident angle θ of the irradiation light with respect to the recording paper. For this reason, the reflected light information obtained by the unique incident angle used in the conventional identification method can distinguish between plain paper and gloss coated paper (discrimination of the type of recording paper), but it is highly accurate for both. It was difficult to achieve both brand identification.

  On the other hand, the optical sensor 100 of the present embodiment includes an irradiation system that irradiates light at a plurality of different incident angles with respect to the recording paper, and individually reflects a plurality of reflected lights reflected corresponding to the plurality of irradiation angles. By detecting, it becomes possible to discriminate brands with high accuracy for both plain paper and glossy paper.

  Hereinafter, an example of a recording sheet determination process using the optical sensor 100 of the present embodiment will be described with reference to FIG. The flowchart in FIG. 20 is based on a processing algorithm executed by the processing device 110. The control flow here starts when the recording paper M is inserted into the slit of the optical sensor 100 by the user and a recording paper determination request is input to the processing device 110 via an operation panel (not shown) or a personal computer. Is 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 simultaneously, 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 type of the recording sheet M is estimated from the obtained values S01 and S02 with reference to the recording sheet discrimination table. Then, the recording paper type estimated as the values of S01 and S02 is 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 or not the estimated type is plain paper or matte coated paper (hereinafter referred to as “plain paper or the like”). If the determination here is affirmed, the process proceeds to step T5. 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 a detection result at an incident angle θ1 suitable for brand identification of plain paper or the like, the brand of the recording paper M estimated to be plain paper or the like can be easily estimated. Specifically, referring to the recording sheet discrimination table, the brand of the recording sheet 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 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 θ 2.

  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 values of S01 'and S03' obtained with reference to the recording paper discrimination table. The type of the recording sheet M estimated as the values of S01 'and S03' is stored in the RAM.

  In this case, since the output signal of the light receiver 19 is a detection result at an incident angle θ2 suitable for brand identification of gloss coated paper, it was not estimated as plain paper or the like at step T3 (estimated to be gloss coated paper). The brand of the recording paper M can be easily estimated.

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

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

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

  The user sets the recording paper M on which the brand identification has been made on the paper feed tray 2060 or the manual feed tray of the color printer 2000 and performs printing. In this case, since the image forming process is performed under the optimal image forming conditions 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 light source (11, 11 ′), a collimator lens (12, 12 ′), a plurality of light receivers (13, 15, 19), and a polarizing filter 14. And a processing device 110.

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

  In this case, linearly polarized light can be 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, brands are discriminated by making light from a light source incident on a recording sheet at a unique incident angle and detecting the reflected light. On the other hand, in this 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 high brand discrimination accuracy for a plurality of paper types that 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 the plurality of lights irradiated from the plurality of irradiation systems and regularly reflected by the recording paper, Regular reflection light can be detected for each irradiation system.

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

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

  The second detection system includes a photodetector (light receiver 13) disposed on an optical path of light emitted from the irradiation unit and diffusely reflected in a direction perpendicular to the surface of the object by the recording paper, and the light. A polarizing filter disposed on the optical path of light between the detector and the recording paper and transmitting a linearly polarized component (for example, a P-polarized component) having a polarization direction orthogonal to a predetermined polarization direction.

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

  Further, the detection means includes a third detection system disposed on the optical path of the light irradiated from the irradiation means and diffusely reflected in a direction different from the direction perpendicular to the surface of the recording paper.

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

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

  Further, since the light source includes a surface emitting laser array, linearly polarized light with a stable polarization direction can be emitted. Further, speckle can be reduced by simultaneously lighting a plurality of light emitting units.

  Further, since the optical sensor 100 further includes a processing device 110 that estimates the type and brand of the recording paper based on the output of the detection means, the optical sensor 100 itself can determine the recording paper. Note that the optical sensor 100 may not include the processing device 110. In this case, the control performed by the processing device 110 may be performed by the control device 2090 to determine the recording paper. Further, the control device 2090 may perform 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, development conditions and transfer conditions) according to the brand of the recording paper estimated by the optical sensor 100, the recording paper can be used regardless of the brand of the recording paper. High quality images can be formed on paper.

  In addition, 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 lights having a predetermined polarization direction from different directions inclined with respect to the recording paper M. Individually detecting a plurality of lights reflected in the direction.

  In this case, linearly polarized light can be 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 irradiating step, the recording paper M is irradiated with a plurality of linearly polarized light at different timings, so that the reflected light of each linearly polarized light can be detected individually and accurately in the detecting step. If a plurality of linearly polarized lights are irradiated simultaneously, the reflected light of a plurality of linearly polarized lights is detected at the same time in the detecting step, and it is difficult to detect a plurality of reflected lights of each linearly polarized light individually with high accuracy. is there.

  In the detection step, a plurality of light regularly reflected in different directions on the recording paper M (a plurality of regular reflection lights) are detected at different timings, so that recording is performed based on the power of the regular reflection light detected first. 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 the specular reflection light detected later.

  Further, the object discrimination 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 with respect to the recording paper, and the first irradiation. A first detection step for detecting light specularly reflected by the recording paper M during the process, a first estimation step for estimating the type of the recording paper M based on a detection result in 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 estimation step; A second detection step of detecting the light regularly reflected by the recording paper M during the irradiation step, and a second estimation step of estimating the characteristics of the recording paper M based on the detection result in the second detection step; ,including.

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

<< Modification 1 >>
Incidentally, the optical sensor 100 of the above embodiment includes the light source 11 ′ and the collimating lens 12 ′. Instead of this, like the optical sensor 200 of the first modification shown in FIG. A plurality of (for example, two) mirrors 32 and 33 may be used to irradiate light (from the incident direction) to the recording sheet M as a discrimination target at a plurality of (for example, two) incident angles.

  Here, the light source 11 emits a light beam in a direction parallel to the Z-axis. The collimating 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 disposed on the optical path of the light passing through the collimator lens 12 and separates the light into transmitted light and reflected light. The beam splitter 31 is preferably a half mirror that can equalize the amount 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 becomes 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 surface regular reflection light incident on the recording paper at 75 °, and the light receiver 19 receives and detects surface regular reflection light incident on the recording paper at 60 °.

  In this case, a single 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. Similarly, by adding a beam splitter and a mirror, it is possible to make a light beam incident on the recording paper M at three or more different incident angles using a single light source.

  Further, the optical sensor 200 according to the first modification includes a light shielding unit that can selectively shield one of the transmitted light and the reflected light from the beam splitter 31.

  The light shielding means includes a light shielding member 250, a first light shielding position that is the position of the light shielding member 250 on the optical path of the transmitted light from the beam splitter 31, and the position of the reflected light from the beam splitter 31 on the optical path. And an actuator (not shown) for moving between the two light shielding positions. Here, the first light shielding position is a position on the optical path of the light reflected by the mirror 33, and the second light shielding position is a 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 is preferably a member that scatters or photothermally converts light from the viewpoint of suppressing return light to the light source 11.

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

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

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

  In the first step U1, 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 simultaneously. As a result, among the transmitted light and reflected light from the beam splitter 31, the reflected light is shielded by the light shielding member 250, and the transmitted light is incident on the recording paper M at an 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 type of the recording sheet M is estimated from the obtained values S01 and S02 with reference to the recording sheet discrimination table. Then, the recording paper type estimated as the values of S01 and S02 is stored in the RAM.

  In the next step U3, it is determined whether or not the estimated type is plain paper or matte coated paper (hereinafter referred to as “plain paper or the like”). If the determination here is affirmed, the process proceeds to step U4. 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 a detection result at an incident angle θ1 suitable for brand identification of plain paper or the like, the brand of the recording paper M estimated to be plain paper or the like can be easily estimated. Specifically, referring to the recording sheet discrimination table, the brand of the recording sheet 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 (a position where the transmitted light from the beam splitter 31 is blocked). As a result, among the transmitted light and reflected light from the beam splitter 31, the transmitted light is shielded by the light shielding member 250, and the reflected light is incident on the recording paper M at an 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 values of S01 'and S03' obtained with reference to the recording paper discrimination table. The type of the recording sheet M estimated as the values of S01 'and S03' is stored in the RAM.

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

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

  After performing the recording sheet determination process as described above, the processing apparatus 110 sends the brand of the recording sheet M estimated in step U4 or step U6 to the control apparatus 2090.

  The control device 2090 adjusts image forming conditions (for example, development conditions and transfer conditions) in accordance with the estimated brand of recording paper in the same manner as in the above embodiment.

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

  In the first modification described above, the irradiating means includes a light source 11 common to at least two (for example, two) irradiation systems among a plurality (for example, two) of irradiation systems, and transmits light from the light sources 11 as transmitted light. And a beam splitter 31 (separation optical element) that separates 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 recording paper discrimination accuracy while reducing the cost.

  The irradiating means further includes reflecting means including mirrors 32 and 33 for reflecting the transmitted light and reflected light from the beam splitter 31 toward the recording paper M.

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

  Further, since the irradiating means further includes a light shielding means capable of selectively shielding one of the transmitted light and the reflected light from the beam splitter 31, the recording paper M is irradiated with the transmitted light and the reflected light 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, like the optical sensor 300 of the second modification shown in FIG. 12, the light (transmitted light) emitted from the light source 11 and transmitted through the beam splitter 31 out of the light passing through the collimator lens 12 is directly advanced to directly record the recording paper. A configuration in which the light (reflected light) incident on M and reflected by the beam splitter 31 is reflected by the mirror 32 toward the recording paper M may be employed. In this case, the mirror 33 can be omitted, and the number of parts can be further reduced and the cost can be reduced. In this case, it is preferable to match the emission direction of the light source 11 to 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 | adopt the structure to make. In this case, the mirror 32 can be omitted. In this case, it is preferable to match the reflection direction of the reflected light from the beam splitter 31 with a desired incident angle with respect to the recording paper M. In any of the above cases, a reflecting member may be added. 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 possibility of erroneous paper type discrimination due to the influence of disturbance light or stray light, the number of detection systems including light receivers in each detection means may be increased.

  Similarly to the first modification, the optical sensor 300 according to the second modification also includes a light shielding unit including a light shielding member 250 that can selectively shield one of the transmitted light and the reflected light from the beam splitter 31 (FIG. 12).

  The recording sheet determination process using the optical sensor 300 of the second modification can also be performed according to the procedure of the flowchart of FIG.

<< Modification 3 >>
For example, a light receiver 17 may be further provided as in the optical sensor 400 of Modification 3 shown in FIG. 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 internally reflected light is very small compared to the light amount of the surface diffuse reflected light, so that the received light amount of the light receiver 17 can be regarded as the light amount of the surface diffuse reflected light.

  An angle ψ4 formed by a line L4 connecting the illumination center and the center of the light receiver 17 and the surface of the recording paper is 120 ° as an example. Here, the center of the light source (11, 11 ′), the center of illumination, the center of the polarizing filter 14, and the center of each light receiver are present on substantially the same plane, but may be shifted from each other in the Y-axis direction. good.

  In this case, the brand determination 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 beam from the light source 11 is irradiated onto the recording paper are “S4” and “S3”, and the light beam from the light source 11 ′ is the recording paper. The signal levels in the output signals of the light receivers 17 and 15 when the light is irradiated are referred to as “S4 ′” and “S2 ′”.

(1) A plurality of light emitting units of the light source 11 are turned on simultaneously.
(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 simultaneously.
(5) The values of S1 ′, S2 ′, S3 ′ and S4 ′ are obtained from the output signals of the light receivers 13, 15, 17, and 19.
(6) Turn off the plurality of light emitting units of the light source 11 ′.
(7) If the value of S1 is equal to or less than a certain value, the processing device 110 identifies the brand of the recording paper based on S3 / S1, S4 / S2, and if the value of S1 is equal to or greater than the certain value, S3 ′ / The brand of the recording paper is specified based on S1 ′ and S4 ′ / S3 ′ (6) The discrimination result is notified to the control device 2090. Then, the brand identification process is terminated.

  In this case, with respect to a plurality of brand recording papers that can be handled by the color printer 2000, S3 / S1, S4 / S2, S3 ′ / S1 ′, and S4 for each brand of the recording paper in a pre-shipment process such as an adjustment process. '/ S3' is measured, and the measurement result is recorded in the processing apparatus 110 as a “recording paper discrimination table”. FIG. 14 shows values of S4 / S1 and S3 / S2 for each brand as an example.

  As described above, a plurality (two) of light receivers that individually detect a plurality of (for example, two) diffused lights reflected in different directions are provided, and a ratio of output values of the plurality of light receivers is calculated. By discriminating the recording paper using the value, accurate discrimination is possible even if there is disturbance light, stray light, or the like.

  In this case, the control device 2090 roughly narrows the paper type using S1 and S2 or S1 ′ and S2 ′, and determines the brand of the recording paper using S4 / S1 and S3 / S2. Also good.

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

  In this case, the control device 2090 roughly narrows down the paper types using S1, S2, S1 ′ and S2 ′, and S4 / S1, S3 / S2, S4 ′ / S1 ′ and S3 ′ / S2 ′. May be used to determine the brand of the recording paper.

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

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

  FIG. 15A and FIG. 15B show the results of examining the influence of disturbance light in the case of determination using only S1 and S2 and the case of determination using S4 / S1 and S3 / S2. It is shown. When making a determination using only S1 and S2, as shown in FIG. 15A, if there is disturbance light, the detection value in each light receiving system becomes large, and there is a risk of erroneous determination. On the other hand, when discriminating 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 disturbance light, even if there is disturbance light. The correct determination can be made without changing.

  By the way, in the said embodiment and each modification, since each light source has the surface emitting laser array which inject | emits a linearly polarized light, the polarizing filter for making an emitted light into a linearly polarized light is unnecessary. In addition, since the emitted light can be easily converted into parallel light and a compact light source having a plurality of light emitting units can be realized, the optical sensor 100 can be reduced in size and cost.

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

  In addition, since each light source has a plurality of light emitting units, the light amount and the transmitted light amount of the P-polarized component included in the internally reflected light can be increased by lighting all the light emitting units simultaneously.

  By the way, the diffusely reflected light includes A: “S-polarized light reflected by the surface”, B: “S-polarized light reflected internally”, and C: “P-polarized light reflected internally”. Among these, “P-polarized light reflected internally” is separated by a polarizing filter and the amount of light detected can be subdivided for discrimination, but irradiation with a high amount of light is necessary for the following reasons.

  When the irradiation light is S-polarized light, the ratio of “P-polarized light reflected internally” in the diffuse reflected light (A + B + C) is about 40% at the maximum. 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, “P-polarized light reflected inside” attenuates when separated by the polarization filter, and is substantially about 30%.

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

  In the embodiment and each of the modified examples, the type of recording paper is determined from at least 10 types of recording paper only by “P-polarized light reflected internally”. That is, detailed paper discrimination more than five times compared with the conventional two types of recording paper types is performed. Therefore, high resolution is required with a smaller amount of light than before. However, if a light receiver having a high resolution is used, it is possible to discriminate even with a low amount of light, but this leads to an increase in cost.

  Therefore, in the above-described embodiment and each modification, high resolution is obtained by increasing the amount of irradiation light. Specifically, as described above, the amount of internal diffuse reflected light is attenuated to about 30% of the diffuse reflected light (A + B + C), and therefore, the irradiation light amount is required to be 3.3 times the conventional light amount. . Furthermore, in order to perform detailed paper discrimination five times that of the prior art, it is necessary to irradiate a light amount of about 3.3 × 5 times that of the prior art. Thus, it is necessary to increase the amount of irradiation light in proportion to discriminating many types of recording paper.

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

  However, the irradiation light quantity of an inexpensive LED is about several mW (typically 1 mW), 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 amount of irradiation light by simultaneously lighting a plurality of light emitting units. Therefore, in the surface emitting laser array, it is possible to secure an irradiation light amount necessary for determining the type of paper more than before.

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

  Furthermore, since a surface emitting laser array is used, more stable linearly polarized light can be irradiated. Thereby, the light quantity of the P polarization component contained in the internally reflected light can be detected with high accuracy.

  Since the color printer according to the embodiment and each modification includes the optical sensor 100, a high-quality image can be formed as a result. Furthermore, the troublesome printing that has to be manually set and the printing failure due to setting mistakes are eliminated.

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

  Moreover, in the said embodiment and each modification, as for the some light emission part in a surface emitting laser array, at least one part light emission part space | interval may differ from other light emission part space | intervals (refer FIG. 16).

  Moreover, although the said embodiment and each modification demonstrated the case where each light source had a several light emission part, it is not limited to this, At least 1 light source has a single light emission part. Also good.

  In the embodiment and each modification, the two light sources 11 and 11 ′ are turned on at different timings. However, 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.

<< Modification 4 >>
In addition, as in the optical sensor 500 of 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 light from the light source 11, and predetermined polarization out of light from the light source 11 ′. A polarizing filter 25 ′ that transmits only the linearly polarized light in the direction is required.

  The optical sensor 500 of the modification 4 described above, each light source includes an LD, and polarization that transmits linearly polarized light in a predetermined polarization direction out of the light on the optical path between the LD and the recording paper M. A filter is placed.

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

  Moreover, in the said embodiment and each modification, it is preferable that the condensing lens is arrange | positioned ahead of the at least 1 light receiver. In this case, it is possible to reduce the change in the amount of light detected by the light receiver.

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

  Moreover, in the said embodiment and each modification, the optical sensor 100 may incorporate the power supply. In this case, power supply from the color printer 2000 is not necessary.

  Further, in the above-described embodiment and each modification, data exchange between the optical sensor 100 and the control device 2090 may be performed wirelessly.

  In the above embodiment and each modification, 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.

  In the above embodiment and each modification, the optical sensor 100 may acquire the output signal of each light receiver every predetermined sampling time. For example, when P pieces of 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 a measurement value.

  Incidentally, the 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 in the same plane at the time of measurement. However, the recording paper surface may be inclined or lifted with respect to the measurement surface for reasons such as deflection and vibration, and the recording paper surface may not be flush with the measurement surface. In this case, the amount of reflected light changes and it is difficult to make a stable and detailed determination. Here, specular reflection will be described as an example.

  FIG. 18A shows a case where the measurement surface and the surface of the recording paper are the same plane. At this time, the light detection system can receive regular reflection.

  FIG. 18B shows a case where the surface of the recording paper is inclined by an 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 shifted by 2α from the regular reflection direction. Since the reflected light intensity distribution moves with the shift, if the distance between the center position of the irradiation region and the light detection system is L, the light detection system receives light at a position shifted by L × tan 2α from the regular reflection light receiving position. It will be. Further, the actual incident angle is deviated by α from the prescribed incident angle θ, and the reflectance from the recording paper changes. For this reason, a change occurs in the detected light quantity, and as a result, detailed discrimination becomes difficult.

  FIG. 18C shows a case where the surface of the recording paper is displaced by d in the height direction, that is, the Z-axis direction 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 reflected light intensity distribution is moved with the shift, so the light detection system is moved from the regular reflection light receiving position. Light is received at a position shifted by 2d × sin θ. For this reason, a change in the detected light amount occurs, and as a result, detailed discrimination becomes difficult.

  In the case of FIGS. 18B and 18C, a condensing lens is disposed in front of the light detector of the light detection system with respect to the movement amount so that the light detection system reliably detects the specular reflection light. Even when the reflected light intensity distribution moves, it can be dealt with by condensing.

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

  Further, it is possible to use a PD arrayed in a light receiver and have a light receiving region that is 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 is moved, the maximum signal among the signals detected by the PDs may be set as a regular reflected light signal. In addition, when PDs are arrayed, by reducing the light receiving area of each PD, output fluctuations due to misalignment between the center of the regular reflected light and the light receiving area can be reduced, so that more accurate detection can be performed. it can.

  For the sake of convenience, specular reflection has been described here, but the amount of detected light varies due to the deviation between the measurement surface and the recording paper surface for surface diffuse reflection, internal diffuse reflection, and transmitted light as well. Can respond.

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

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

  Further, in the above-described embodiment and each modification, the case of the color printer 2000 as the image forming apparatus has been described. 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 and each modification, 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 100 can also be applied to an inkjet image forming apparatus that forms an image by spraying ink onto a recording sheet.

  Below, the thought process which the inventors came up with the said embodiment and each modification is demonstrated.

  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 represented by printing paper and heats and presses it under predetermined conditions to fix the image and form an image. Image formation conditions such as phenomenon conditions, transfer conditions, and fixing conditions must be taken into consideration in image formation. In particular, in order to perform high-quality image formation, the image formation conditions are individually set according to the recording medium. There is a need.

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

  Furthermore, with recent advances in image forming devices and diversification of expression methods, there are hundreds of types of recording media, even on printing paper alone, and there are differences in specifications such as basis weight and thickness for each type. There are a wide variety of brands. In order to form a high quality image, it is necessary to set fine image forming conditions corresponding to each of these brands.

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

  In the current image forming apparatus, the user himself / herself needs to set paper brands and fixing conditions for each tray during printing. For this reason, the user is required to have knowledge for identifying the paper type, and the user has to input the setting contents corresponding to the paper type by himself / herself. If the setting contents are incorrect, an optimum image cannot be obtained.

  By the way, Patent Document 1 discloses a surface property identification device provided with a sensor that identifies the surface property of the surface of the recording material by contacting and scanning the surface of the recording material.

  Patent Document 2 discloses a printing apparatus that determines a paper type from a pressure value detected by a pressure sensor contacting a paper.

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

  Patent Document 4 discloses a sheet material material discriminating apparatus that discriminates the material of a moving sheet material on the basis of a reflected light amount reflected from the surface of the sheet material and a transmitted light amount transmitted through the sheet material.

  Patent Document 5 discloses an image forming apparatus having a determining unit that determines the presence / absence of a recording material accommodated in a paper feeding unit and the presence / absence of a paper feeding unit based on a detection output from a reflective optical sensor. Yes.

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

  However, in the sheet material material discriminating apparatus disclosed in Patent Document 4 and the image forming apparatuses held in Patent Document 5 and Patent Document 6, it is possible to identify (discriminate) the non-coated paper / coated paper / OHP. The only difference was the sheet, and it was not possible to identify the brands that were necessary for high-quality image formation.

  By the way, FIG. 6 shows the theoretical value of the glossiness at the incident angle θ degree (θ = 60 °, 75 °, 80 °) with respect to the glossiness at the incident angle of 60 °, and the incident angle with respect to the glossiness at the incident angle of 60 °. It is the graph showing the measured value according to brand of the recording paper of the glossiness at 75 degree | times.

  Comparing the differences between the brands on each axis, in the brand identification of the recording paper, θ = 60 ° is effective when the difference between the brands on the horizontal axis is large, and θ = 60 when the difference between the brands on the vertical axis is large. 75 ° is effective. Further, as shown in FIG. 6, the difficulty of discriminating brands of plain paper, gloss coated paper, and mat coated paper varies depending on the incident angle θ of the irradiation light with respect to the recording paper. As an example, the plain paper is easier to discriminate as the incident angle θ of the irradiation light is larger, and the gloss coated paper is easier to discriminate the brand as the incident angle θ of the irradiation light is smaller. However, the optical sensor disclosed in Patent Document 7 has a configuration in which the incident angle of the irradiation light from the light source with respect to the recording paper takes a unique value. Therefore, the configuration of the optical sensor disclosed in Patent Document 7 has room for improvement in order to identify various types of printing paper with high accuracy.

  Therefore, the inventors have come up with the above-described embodiment and each modified example after intensive studies.

  DESCRIPTION OF SYMBOLS 11, 11 '... Light source, 13 ... Light receiver (light detector), 14 ... Polarizing filter (polarization optical element, a part of detection system), 15 ... Light receiver (detection system), 17 ... Light receiver (detection system) , 19 ... Light receiver (detection system), 25, 25 '... Polarization filter (another polarization optical element), 31 ... Beam splitter (separation optical element), 32 ... Mirror (part of reflection means), 33 ... Mirror ( Part of reflecting means), 110... Processing device, 2000... Color printer (image forming apparatus), M... Recording paper (object, recording medium).

JP 2002-340518 A JP 2003-292170 A JP 2005-156380 A JP-A-10-160687 JP 2006-062842 A JP 11-249353 A JP 2012-128393 A

Claims (16)

An irradiation unit including a plurality of irradiation systems for irradiating the object with linearly polarized light having a predetermined polarization direction from different directions inclined with respect to the object;
An optical sensor comprising: a plurality of lights individually detected from the irradiation means and reflected by the object in different directions.   The detection unit includes a plurality of detection systems individually arranged on an optical path of a plurality of lights irradiated from the irradiation unit and regularly reflected in different directions by the object. The optical sensor described. The detection means includes
A photodetector disposed on the optical path of light emitted from the irradiation means and diffusely reflected by the object in a direction orthogonal to the surface of the object;
A polarizing optical element disposed on an optical path of light between the object and the photodetector and transmitting a linearly polarized light component having 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 an optical path of light emitted from the irradiation means and diffusely reflected by the object in a direction different from a direction orthogonal to the surface of the object. The optical sensor as described in any one of Claims 1-3. The irradiation means includes
A light source common to at least two of the plurality of irradiation systems;
The optical sensor according to claim 1, further comprising 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.   The said irradiation means further has a reflection means for reflecting at least one of the said transmitted light and the said reflected light from the said separation optical element toward the said target object, The Claim 5 or 6 characterized by the above-mentioned. Optical sensor.   The optical sensor according to claim 1, wherein the irradiation unit includes a light source in each irradiation system.   The optical sensor according to claim 5, wherein the light source includes a surface emitting laser array. The light source includes a laser diode;
6. Another polarizing optical element that transmits linearly polarized light in the predetermined polarization direction of the light is disposed on an optical path of the light between the laser diode and the object. The optical sensor as described in any one of -9.   The optical sensor according to claim 1, further comprising a processing device that estimates a type and a feature of the object based on an output of the detection unit. 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. Irradiating the object with a plurality of linearly polarized light in a predetermined polarization direction from different directions inclined with respect to the object;
And individually detecting a plurality of lights reflected in different directions by the object.   The object information measuring method according to claim 13, wherein, in the irradiating step, the object is irradiated with the plurality of linearly polarized light at different timings.   The object information measuring method according to claim 14, wherein in the detecting step, a plurality of lights regularly reflected by the object in different directions are detected at different timings. Irradiating the object with linearly polarized light in a predetermined polarization direction from a first direction inclined with respect to the object;
Detecting light specularly reflected by the object;
Estimating the type of the object based on the detection result in the detecting step;
Irradiating the object with the linearly polarized light from a second direction inclined with respect to the object according to the type of the object estimated in the estimating step;
Detecting light specularly reflected by the object;
Estimating the characteristics of the object based on the detection result in the detecting step.