JP6380629B2 - Optical sensor and image forming apparatus - Google Patents

Description

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

  A so-called electrophotographic image forming apparatus such as a digital copying machine or a laser printer transfers a toner image onto a recording medium such as a recording paper, and records the toner image on a recording paper or the like by heating and pressing under a predetermined condition. An image is formed by fixing on a medium. In such an image forming apparatus, it is necessary to consider conditions such as a heating amount and a pressure when fixing a toner image. In particular, when forming a high-quality image, the toner image is fixed. It is necessary to individually set the conditions for this according to the type of the recording medium.

  This is because the image quality recorded on the recording medium is greatly influenced by the material, thickness, humidity, smoothness, coating state, and the like of the recording medium. In particular, regarding smoothness, depending on the fixing conditions, the toner fixing rate in the concave portion of the recording medium becomes low, and a high-quality image cannot be obtained.

  On the other hand, in the paper manufacturing industry and the like, the smoothness of paper is evaluated based on the measurement result of an air leak test with a simple measuring method as an index of the surface state of paper such as recording paper. This smoothness index is used in the paper industry. For example, in the development of a copying machine, development has been made to optimize printing conditions using the smoothness of paper as one of the standards. That is, as an index indicating the paper surface state, a measurement result by an air leak test is used rather than an index indicating a general surface state such as the root mean square height Ra.

  However, although the air leak test is easy to measure, there are problems that the apparatus becomes large and the measurement takes time. For this reason, there has been a demand for a small sensor that can be installed in an apparatus such as an image forming apparatus at a low price and can inspect the surface condition of the paper, that is, the smoothness, similar to the air leak test.

  As a recording medium identification sensor such as recording paper, a method of detecting a frictional resistance of a surface with a stylus probe as described in Patent Document 1, a pressure sensor as described in Patent Document 2, and the like. There is a method for detecting the stiffness (rigidity) of the recording medium. Further, as described in Patent Document 3, as a method for identifying a recording medium in a non-contact manner, the surface of the recording medium is imaged by an imaging element such as an area sensor, and the type of the recording medium is determined from the captured image. There is a way to identify.

  Another non-contact recording medium identification method is a reflected light method. In the reflected light system, light emitted from a light source such as a light emitting diode (LED) is irradiated onto a recording medium to be identified, and the brand of the recording medium is identified by the amount of light reflected from the recording medium. is there. This reflected light system has the following three methods.

  As described in Patent Document 4, the first method detects the amount of reflected light in the regular reflection direction of light irradiated on the surface of a recording medium, and records based on the detected amount of light in the regular reflection direction. This is a method for identifying the brand of the medium. More specifically, in Patent Document 4, the brand of the recording medium is identified by detecting the amount of light in the regular reflection direction and the amount of light transmitted through the paper. Therefore, the identification is not performed only by the amount of light in the regular reflection direction.

  As described in Patent Literature 5, the second method includes a plurality of light amount detection units. Specifically, it detects not only the amount of reflected light in the regular reflection direction of the light irradiated on the surface of the recording medium but also the amount of scattered reflected light, and the detected amount of light in the regular reflection direction and the amount of scattered reflected light. This is a method for identifying brands and the like of recording media based on the above.

  In the third method, as described in Patent Document 6, the reflected light in the regular reflection direction of the light irradiated on the surface of the recording medium is separated by a polarization beam splitter, and the light quantity of the separated light is measured. In this method, the brand of the recording medium is identified based on the measured light quantity.

  On the other hand, there are inspection apparatuses and inspection methods described in Patent Documents 7 and 8 as methods for foreign matter inspection and the like.

  Compared with a generally known optical element as shown in Patent Document 5, the incident angle is detected at a considerably shallow angle of 70 ° to 88 °, and the detection capture angle is 10 ° or less. Details of the technique for improving the detection accuracy by doing so are described in Patent Document 9.

  However, since the methods described in Patent Documents 1 and 2 are contact methods, there is a problem that the surface of recording paper or the like as a recording medium is damaged. Further, the methods described in Patent Documents 3 to 6 are not accurate enough to detect the smoothness of the recording medium in detail as in the air leak test.

  Further, as described in Patent Document 9, in principle, it is expected that the detection accuracy is improved as the capturing angle of the scattering angle of the light scattered by the recording medium is reduced. However, as an actual sensor, the aperture becomes very small, and the processing accuracy of the aperture shape and the amount of light passing through the aperture become very small. Such a decrease in the amount of light is affected by noise, which leads to a decrease in detection accuracy. In Patent Document 9, a high-quality component processing method and materials that can maintain a highly accurate aperture shape are used to reduce the tolerance to the utmost limit, and to a detector that is ultra-sensitive and excellent in noise resistance. By using this, it was possible to detect the smoothness of the paper.

  However, considering the manufacturing cost, it is desirable to use an aperture of a low-cost material such as a resin, a photodiode made of silicon, or the like. For that purpose, it is required to obtain as much light as possible. That is, it is desired that the aperture shape be as large as possible and the detection accuracy be improved.

  The present invention has been made in view of the above, and an object of the present invention is to provide a small optical sensor capable of identifying a recording medium with high accuracy at low cost.

According to one aspect of this embodiment includes a light source, irradiating the recording medium with light emitted from the light source, a photodetector for detecting the intensity of the specular reflection light in the recording medium, wherein the The angle θ1 of the optical axis connecting the light source and the center of the irradiation area formed on the recording medium with respect to the normal of the surface of the recording medium is 75 ° ≦ θ1 ≦ 85 ° , and The angle θ2 of the optical axis connecting the center of the irradiation area formed on the recording medium and the photodetector is the same as the angle θ1 with respect to the surface normal, and the spread is on the side where the angle is smaller than the angle θ2. Of the reflected light reflected in the irradiated area on the recording medium with respect to the normal of the surface of the recording medium, the angle is θx1, the spread angle on the side larger than the angle θ2 is θx2, and the light When the angle of light incident on the detector is θ,
| Θx1 |> | θx2 |
θx1 + θ1 <θ <θx2 + θ1
What der satisfy the, the incorporation full angular width | θx1 | + | θx2 | is, 5 ° ≦ | θx1 | + | θx2 | a ≦ 15 ° der wherein Rukoto.

  ADVANTAGE OF THE INVENTION According to this invention, the small optical sensor which can identify a recording medium with high precision can be provided at low cost.

Explanatory drawing of experimental equipment used for study of invention Correlation diagram between detection angle and correlation function in optical sensor (1) Correlation diagram between detection angle and detected light intensity in optical sensor Correlation diagram between detection angle and correlation coefficient in optical sensor (2) Correlation diagram between detection angle and correlation coefficient in optical sensor (3) Explanatory drawing of aperture plate (1) Structure of aperture plate Explanatory drawing of aperture plate (2) Structure diagram of the optical sensor in the first embodiment Structure diagram of aperture plate used for optical sensor in first embodiment Explanatory drawing of the process part of the optical sensor in 1st Embodiment Flowchart of a detection method using an optical sensor in the first embodiment Relationship between smoothness and process conditions Structure diagram of optical sensor according to second embodiment The principal part enlarged view of the optical sensor in 2nd Embodiment Structure diagram of aperture plate used for optical sensor in second embodiment Structure diagram of optical sensor according to third embodiment The principal part enlarged view of the optical sensor in 3rd Embodiment Structure diagram of image forming apparatus according to fourth embodiment

  The form for implementing this invention is demonstrated below. In addition, about the same member etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

[First Embodiment]
First, the contents of the study conducted up to this embodiment will be described. In the present application, the recording paper may be described as a recording medium.

  Specifically, an aperture plate having an opening with an intake angle of about 10 ° is provided, and a method for detecting paper smoothness with high accuracy while suppressing a decrease in the amount of light incident on the specular reflection detector is studied. Went. With this study, the paper smoothness can be detected with high accuracy by setting the angle θ of the light incident on the opening in the aperture plate so as to satisfy the following expressions (1) and (2). It came to the result. The present embodiment is based on the results obtained in this examination.

The angle of the optical axis connecting the light source and the center of the irradiation area formed on the recording paper with respect to the normal of the surface of the recording paper is θ1, and the optical axis is formed on the recording paper with respect to the normal of the surface of the recording paper. The angle of the optical axis connecting the center of the irradiation area and the photodetector is θ2, the spread angle on the side smaller than the angle θ2 is θx1, and the spread angle on the side larger than the angle θ2 is θx2. .

| Θx1 |> | θx2 | (1)

θx1 + θ1 <θ <θx2 + θ1 (2)

Hereinafter, the details of the study will be described in detail.

  First, in order to detect the smoothness of the recording paper, an experiment was conducted to find the optimum incident angle. Specifically, the experiment was performed using the experimental apparatus shown in FIG. In the experiment, the light source 10, the specular reflection light detector 30, and the recording paper 20 are used so that light emitted from the light source 10 and passing through the collimator lens 11 is reflected on the recording paper 20 and enters the specular reflection light detector 30. Arranged. That is, the angle (incident angle) θe1 of the optical axis of light incident on the recording paper 20 from the light source 10 with respect to the normal line of the paper surface of the recording paper 20 and the reflected light incident on the regular reflection light detector 30. It arrange | positions so that the angle (detection angle) (theta) e2 of the optical axis of light may become equal.

  Next, the incident angle θe1 and the detection angle θe2 are changed from 60 ° to 90 °. At this time, the light source 10 and the regular reflection light detector 30 are simultaneously moved so that the incident angle θe1 and the detection angle θe2 are the same. A high-precision photogoniometer was used for the measurement. A laser diode (LD) was used as the light source 10, and the collimator lens 11 made parallel light having a beam diameter of about 1 mm. For the regular reflection light detector 30, a photodiode (PD) having a detection area of about 2 mm square was used. The light that enters the PD, which is the regular reflection light detector 30, enters through a lens not shown in FIG. The experiment was conducted by setting the total angle width of light taking in the regular reflection light detector 30 to about 0.5 ° and changing the incident angle θe1 and the detection angle θe2 in increments of 0.1 °. The LD that is the light source 10 has a constant light emission intensity by keeping the current value constant. The light that has entered the PD that is the specular reflection light detector 30 is converted into a current corresponding to the amount of light that has entered the PD that is the specular reflection light detector 30, and is further converted into a voltage by an operational amplifier. By reading this voltage value, it is possible to detect the amount of light incident on the PD which is the regular reflection light detector 30.

  In the experiment, 30 types of plain paper to be the recording paper 20 were selected. The selected 30 types of plain paper are almost the same as the types of paper distributed in the market. The smoothness of this plain paper is measured in advance with a smoothness measuring device. The recording paper 20 and the like are installed so that the area where the smoothness measurement is performed on the plain paper and the area where the measurement is performed in the above-described experimental apparatus are substantially the same area. FIG. 2 shows the relationship between the incident angle θe1 and the detection angle θe2 and the correlation coefficient. In FIG. 2, the horizontal axis represents the detection angle as a representative of the incident angle θe1 and the detection angle θe2. Moreover, the value of the correlation coefficient in the above was calculated based on the formula shown in the following formula 1. Further, the incident angle θe1 and the detection angle θe2 mean angles with respect to the normal line on the paper surface of the recording paper.

図２に示されるように、入射角θｅ１及び検出角θｅ２は約８０°において、相関係数がピークとなっており、ピークとなる相関関数の値は０．８に近い。これに対し、入射角θｅ１及び検出角θｅ２が５°ずれている８５°や７５°においては、相関係数の値は、約０．７となる。相関係数の値が０．７を下回ってしまうと、記録紙２０の平滑度計測としては不十分であり、記録紙２０の平滑度で複写機の制御を行うには、相関係数が０．７以上であることが求められる。従って、後述するように本実施の形態における光学センサを記録紙２０の平滑度センサとして用いる場合には、記録紙２０への光の入射角θｅ１及び検出角θｅ２は、８０±５°の範囲、即ち、７５°≦θｅ１（θｅ２）≦８５°であることが好ましい。また、検出角θｅ２が大きいと、搬送中の紙のばたつきなどによる影響を受けてしまうが、相関係数が０.４を下回らない、７０°から８８°の範囲であれば、記録紙２０の平滑度センサとして用いることが可能である。

As shown in FIG. 2, when the incident angle θe1 and the detection angle θe2 are about 80 °, the correlation coefficient has a peak, and the value of the correlation function at the peak is close to 0.8. On the other hand, when the incident angle θe1 and the detection angle θe2 are shifted by 5 °, the value of the correlation coefficient is about 0.7. If the value of the correlation coefficient falls below 0.7, the measurement of the smoothness of the recording paper 20 is insufficient, and the correlation coefficient is 0 for controlling the copying machine with the smoothness of the recording paper 20. .7 or more is required. Therefore, as will be described later, when the optical sensor according to the present embodiment is used as the smoothness sensor of the recording paper 20, the incident angle θe1 and the detection angle θe2 of light on the recording paper 20 are in the range of 80 ± 5 °, That is, it is preferable that 75 ° ≦ θe1 (θe2) ≦ 85 °. Further, if the detection angle θe2 is large, it is affected by flapping of the paper being conveyed, but if the correlation coefficient is not less than 0.4, and is in the range of 70 ° to 88 °, the recording paper 20 It can be used as a smoothness sensor.

  Using the experimental apparatus shown in FIG. 1, when the incident angle θe1 was fixed at 80 ° and the detection angle θe2 was changed, the amount of light detected by the regular reflection light detector 30 was examined. The result is shown in FIG. The paper used for the measurement this time is coated paper 3A, plain paper 3B and 3C. The smoothness is 5200 sec for the coated paper 3A and 120 sec and 40 sec for the plain papers 3B and 3C, respectively. As is apparent from the angle dependence shown in FIG. 3, the coated paper 3A has a light intensity peak at a regular reflection angle of about 80 °, while the plain papers 3B and 3C have a light intensity peak. The peak is shifted in a large angular direction by about 5 °.

  As shown in FIG. 3, it is generally known that the intensity of light detected at the regular reflection angle is maximum in the case of paper with high smoothness such as coated paper 3 </ b> A. However, it is not known that paper with low smoothness, such as plain papers 3B and 3C, has the maximum strength at a position shifted by about 5 ° from the regular reflection angle of 80 °. Experiments that have been tested on paper, not on general scatterers, have a long history, and are not currently known at all, particularly in the field of smoothness sensors for recording paper 20.

  In general, the intensity of the reflected light amount is said to have a correlation with the smoothness of the recording paper 20. Certainly, as shown in FIG. 3, there is a correlation when the detection angle θe2, which is an angle for regular reflection, is 80 °. However, when the detection angle θe2 is 85 °, the correlation is lost. That is, when the detection angle θe2 is 85 °, the amount of reflected light on the coated paper 3A is drastically reduced. On the other hand, the amounts of light on the plain papers 3B and 3C are increased, and the relationship between the detected reflected light amounts is as follows. It is reversed. This lowers the correlation with the paper smoothness. This is because the intensity peak positions of the plain papers 3B and 3C are shifted in a large angular direction by about 5 ° from the angle at which regular reflection occurs.

  Furthermore, the contents of FIG. 3 obtained in the experiment were analyzed in detail, and the improvement of detection accuracy was examined. As described above, in the case of recording paper with low smoothness, the reflection intensity peak deviates from the regular reflection by about 5 °, resulting in a large angle value. Specifically, the angle of regular reflection is 80 °, but the peak is 85 °. The reversal of the light intensity occurs between the recording paper with low smoothness and the recording paper with high smoothness at a value exceeding 83 ° on the large angle side and below 70 ° on the small angle side. Since the regular reflection angle is 80 °, the difference from the regular reflection angle is + 3 ° at 83 ° and −10 ° at 70 °. That is, with respect to the center of the optical axis in the regular reflection light, the angle is 3 ° on the large angle side and 10 ° on the small angle side. If the smaller side is wider than the larger angle side, the type of recording paper can be detected more accurately.

  Furthermore, an experiment was conducted to confirm this result.

In the experimental apparatus shown in FIG. 1, with the incident angle θe1 fixed at 80 °, the reflection intensity angle dependency was measured for 17 types of paper. FIG. 4 shows the relationship between the correlation coefficient (R ² ) with the smoothness and the detection angle θe2. Although it varies depending on the total angle of light capturing in the regular reflection light detector 30, the total angle of light capturing is relatively small and the total angle of light capturing is 5 ° (± 2.5 °). The detection angle θe2 at which the correlation coefficient is the highest was 76 °.

  In general, it is assumed that the correlation increases at 80 °, which is the regular reflection angle where the amount of light increases, but the correlation is highest when it is shifted by −4 ° from 80 °, which is the regular reflection angle. That is contrary to expectations. As described above, this is considered to be caused by the fact that the peak of the light intensity is shifted at the detection angle of the specular reflection light in the case of paper with low smoothness recording. As described above, the relationship between the correlation coefficient obtained by the experiment as shown in FIG. 4 and the detection angle is disclosed for the first time in this experiment. As described above, the present embodiment is based on the result of earnest research on improving the performance of the recording paper 20 as a smoothness sensor.

Therefore, by satisfying the equation shown in the following (1), the correlation with the smoothness can be increased, and the detection accuracy is increased. The spread angle on the minus side (side with a small detection angle) from the optical axis in the regular reflection direction is θx1, and the spread angle on the + side (side with a large detection angle) is θx2.

| Θx1 |> | θx2 | (1)

Even when the equation (1) is satisfied, in actual measurement, if the capture angle is reduced, the amount of light incident on the PD which is the specular reflection light detector 30 is reduced, and the recording paper 20 Therefore, it is necessary to examine the width of the capture angle. Next, an examination was made on the allowable value of how much the capture angle can be increased. Specifically, as shown in FIG. 5, the same experiment as described above was performed by changing the capture angle. Specifically, when the capture angle is 5 ° (± 2.5 °), 10 ° (± 5 °), and 15 ° (± 7.5 °). The relationship between the correlation coefficient (R ² ) with the smoothness of and the detection angle θe2 was examined.

  As shown in FIG. 5, even if the detection angle θe2 is set to 80 °, the detection width of the detection angle θe2 exceeds the range of 75 ° to 85 ° and the measured value is detected when the total angle width of light capture exceeds 10 °. Therefore, the correlation with the smoothness becomes worse. In addition, when the total angle width of light capture increases, the correlation coefficient decreases as shown in FIG. Specifically, the peak of the correlation coefficient is about 0.79 when the total angle of light capture is 5 °, and the peak of the correlation coefficient is when the total angle of light capture is 10 °. When the total angle width of light capture is 15 °, the correlation coefficient peak is slightly higher than 0.76. If the light capture angle is reduced, the amount of light is reduced and cannot be detected by a general PD. Therefore, a capture angle as large as possible is desired. For this reason, it is preferable that the total angle width of the capture is about 10 °.

Next, in the case where the total angle width of capture is 10 °, optimal numerical values are calculated for the spread angles θx1 and θx2. As described above, the optimum angle from the regular reflection angle is 10 ° for the smaller angle and 3 ° for the larger angle. If the width to be detected is assigned as 10 ° at the ratio of 10 ° and 3 °,
θx1 = −7.8 °
θx2 = + 2.2 °
It becomes.

  As a method for obtaining such a light taking-in angle, for example, as shown in FIG. 6, a method of installing an aperture plate 70 having an opening 71 in front of the regular reflection light detector 30 is conceivable. . By providing the aperture plate 70 in this way, the reflected light from the recording paper 20 passes through the opening 71 of the aperture plate 70 and enters the regular reflection light detector 30. As shown in FIG. 7, the shape of the opening 71 in the aperture plate 70 is such that the distance from the optical axis center corresponding to the spread angle θx1 is Aa, and the distance from the optical axis center corresponding to the spread angle θx2 is Ab. It is formed as follows. Further, in the direction perpendicular to the directions at the distance Aa and the distance Ab, the distance from the center of the optical axis is Ac. The distance Aa is a distance on the side where the angle is smaller than the center of the optical axis, and is formed to have a length corresponding to θx1, and the distance Ab is a distance on the side where the angle is larger than the center of the optical axis. It is formed to have a length corresponding to θx2. Further, the light scattering on the recording paper 20 has a general Lambertian distribution in the lateral direction. Therefore, based on the result shown in FIG. 5, the distance Ac has a full angle width of 10 ° (± 5 °). It is formed to have a length corresponding to.

Here, as shown in FIG. 8, when the distance La from the irradiation area center to the aperture plate 70 is assumed to be set so that the surface of the aperture plate 70 is perpendicular to the optical axis center, The distances Aa and Ab in the aperture plate 70 are:
Aa = La × tan (θx1)
Ab = La × tan (θx2)
It is formed and installed to become.

(Optical sensor)
Next, the optical sensor in the first embodiment will be described. FIG. 9 shows an optical sensor in the present embodiment. The optical sensor according to the present embodiment includes a light source 110, a lens 120 that collects light emitted from the light source 110, a regular reflection light detector 130 that detects light regularly reflected on the recording paper 20, and a regular reflection light detector. An aperture plate 170 is provided in front of 130. The light source 110 is formed by an LED (Light Emitting Diode) or the like, and the light emitted from the light source 110 is applied to the recording paper 20 through the lens 120. The light irradiated on the recording paper 20 is reflected on the recording paper 20. The specular reflection light detector 130 is formed of a photodiode or the like, and detects specularly reflected light among the light reflected on the recording paper 20. An aperture 171 is formed in the aperture plate 170, and only light that has passed through the aperture 171 in the aperture plate 170 can be incident on the regular reflection light detector 130. That is, by using the aperture plate 170, it is possible to make light having a predetermined angle incident on the regular reflection light detector 130. The angle θ11 of light incident on the recording paper 20, that is, the angle (incident angle) θ11 of the optical axis connecting the light source 110 and the center of the irradiation area on the recording paper 20 with respect to the normal of the surface of the recording paper 20 is 80 °. The specular reflection detector 130 is connected to a processing unit 150, which controls the optical sensor and performs various calculations.

  Note that the optical sensor in this embodiment includes a housing 160 having an opening 161 on the bottom surface side, and the light source 110, the lens 120, the specular reflection detector 130, the aperture plate 170, and the like are provided in the housing 160. It is installed inside. Further, the angle (detection angle) θ12 of the optical axis connecting the center of the irradiation area on the recording paper 20 and the regular reflection light detector 130 with respect to the normal of the surface of the recording paper 20 is set. In the present embodiment, the incident angle θ11 determined by the position of the light source 110 and the detection angle θ12 determined by the positions of the opening 171 and the regular reflection light detector 130 in the aperture plate 170 are equally set to 80 °.

  In the present embodiment, since the recording paper 20 is preferably irradiated with parallel light with high accuracy, a lens 120 is provided. For example, a lens 120 having a focal length f = 9 mm and a diameter of 2 mmφ is used. The lens 120 is disposed so that the light emitting point of the LED serving as the light source 110 is located at the focal position of the lens 120.

  The specular reflection light detector 130 is also fixed in the housing 160 as in the case of the light source 110. In the present embodiment, the regular reflection light detector 130 is a photodiode (PD). The used PD has a size of about 5 mm square, and a light detection surface serving as a light receiving surface is 3 mm square.

  As shown in FIG. 10, the shape of the opening 171 formed in the aperture plate 170 is a rectangular shape in which the length of one side is (Aa1 + Ab1) and the length of the other side is 2 × Ac1. ing. The opening 171 is formed in a rectangular shape so that it can be easily processed. Aa1 is a distance on the side having a smaller angle than the optical axis center, Ab1 is a distance on a side having a larger angle than the optical axis center, and Ac1 is a distance from the optical axis center in a direction perpendicular to the directions in Aa1 and Ab1. It is. Here, when La is 16 mm and the opening 171 in the aperture plate 170 is formed so that θa1 is 7.8 ° and θa2 is 2.2 °, Aa1 is about 4.8 mm and Ab1 is about 1 .2mm. Further, Ac1 is formed to be about 3.0 mm. Thus, the angle connecting the center of the irradiation area on the recording paper 20 and the center of the opening 171 of the aperture plate 170 is smaller than the angle that is the center of the optical axis. Ac1 regulates the lateral scattered light capturing and assumes a general Lambertian distribution, and Ac1 was calculated with the total capturing angular width of 10 ° (± 5 °).

(Position of recording paper 20)
The object detected by the optical sensor in the present embodiment is the recording paper 20. For example, the recording paper 20 is conveyed by a conveyance roller (not shown) and moves along the guide. For this reason, the distance between the optical sensor and the recording paper 20 in the present embodiment is controlled so as to be always constant.

(Housing 160)
In the optical sensor according to the present embodiment, as described above, the light source 110, the lens 120, the regular reflection light detector 130, and the like are housed in the housing 160. In the optical sensor according to the present embodiment, the recording paper 20 is irradiated with light from the opening 161 of the housing 160, and the regular reflection light detector 130 receives the regular reflection light from the recording paper 20 of the irradiated light. It has become. The casing 160 is formed of black ABS resin or the like that absorbs light, and disturbance light is removed by the casing 160. Inside the housing 160, the light source 110, the lens 120, the specular reflection light detector 130, and the like are formed so as to be fixed.

(Processing unit 150)
Next, the processing unit 150 of the optical sensor in the present embodiment will be described. As shown in FIG. 11, the processing unit 150 is connected to a specular reflection light detector 130 of an optical sensor. The processing unit 150 includes an I / O unit 151 that controls input / output of signals from the specular reflection light detector 130, an arithmetic processing unit 152 that performs various operations such as signal processing, and an averaging process that performs averaging processing and the like. The processing unit 153 includes a storage unit 154 that stores various types of information. The optical sensor in the present embodiment is connected to an image forming apparatus or the like via the processing unit 150.

(Detection method using an optical sensor, etc.)
Next, a detection method using the optical sensor in this embodiment will be described with reference to FIG.

  First, as shown in step 102 (S102), the reflected light intensity detection operation using the optical sensor in the present embodiment is started. Specifically, the operation of turning on the power or a signal notifying the start of printing is sent to the image forming apparatus connected to the optical sensor in the present embodiment, whereby the optical sensor in the present embodiment is changed. The reflected light intensity detection operation used is started.

  Next, as shown in step 104 (S104), the recording paper 20 is conveyed. When the recording paper 20 is transported in this way, the light emitted from the light source 110 is irradiated to the transported recording paper 20 through the lens 120, and the regular reflection light on the recording paper 20 is reflected into the regular reflection light detector 130. Is incident on. In the state in which the recording paper 20 is being conveyed, the recording paper 20 is irradiated with light, and the specular reflection from the one end of the recording paper 20 to the other end is detected by detecting the specular reflection light on the recording paper 20. Light can be detected.

  Next, as shown in step 106 (S106), the reflected light intensity detection on the recording paper 20 is completed, and the measurement result is transmitted to the processing unit 150.

  Next, as shown in step 108 (S108), the processing unit 150 performs a process of averaging the light intensities detected by the regular reflection light detector 130. This averaging process is performed in the averaging processing unit 153 in the processing unit 150.

  Next, as shown in step 110 (S110), the processing unit 150 calculates the smoothness based on the averaged light intensity. Specifically, the arithmetic processing unit 152 in the processing unit 150 calculates the smoothness from the light intensity based on a predetermined conversion formula stored in the storage unit 154 in the processing unit 150. For example, when the intensity of the specularly reflected light detected by the specularly reflected light detector 130 is X (mV), the smoothness Y (sec) is based on a conversion formula of Y = 0.46 × X + 19.8. Smoothness can be calculated.

  Next, as shown in step 112 (S112), in the processing unit 150, based on the calculated smoothness, an image forming process condition at the time of fixing when printing on the recording paper 20 in the image forming apparatus is determined. Specifically, based on the relationship between the smoothness shown in FIG. 13 stored in the storage unit 154 in the processing unit 150 and the printing conditions, the condition closest to the calculated smoothness is set as the image forming process condition at the time of fixing. decide.

  Next, as shown in step 114 (S114), printing is performed on the recording paper 20 in the image forming apparatus, and an image is formed on the recording paper 20.

  As described above, the smoothness can be detected using the optical sensor according to the present embodiment, and the printing conditions of the image forming apparatus can be set based on the detected smoothness.

[Second Embodiment]
Next, a second embodiment will be described. In this embodiment, as shown in FIG. 14, a lens 221 is provided between the recording paper 20 and the aperture plate 270. Accordingly, the lens 221, the aperture plate 270, and the regular reflection light detector 130 are installed in this order from the recording paper 20 side. For example, in the first embodiment, the lens 221 is provided at a position where the aperture plate 170 is installed. Thus, by providing the lens 221, the reflected light from the recording paper 20 can be collimated or condensed, and the amount of light incident on the regular reflection light detector 130 can be increased. . Note that an opening 271 is formed in the aperture plate 270.

  The lens 221 has a function of condensing parallel light on the regular reflection light detector 130. Ideally, when the area of the regular reflection light detector 130 is small, only substantially parallel light can be collected. On the other hand, when the regular reflection light detector 130 has a finite effective diameter, light slightly deviated from parallel light can be collected. In the present application, the angle deviated from the parallel light is referred to as a light taking-in angle. The total angle width of light capture depends on the area of the light receiving surface in the regular reflection light detector 130 and the NA value of the lens 221. If the total angle width of light capture is large, the width of the detection angle θ22 is widened and an error occurs. The following describes a specific method for limiting the capture angle using a lens.

  As shown in FIG. 14, the lens 221 is disposed between the recording paper 20 and the regular reflection light detector 130 at the center of the optical axis centered on the regular reflection (θ11 = θ22) light beam. The lens 221 is arranged in accordance with the f value, for example, the specular reflection light detector 130 so that the light receiving region 131 is before or after the focal position or at the focal position. In the description of the present embodiment, the case where the regular reflection light detector 130 is installed in front of the focal position of the lens 221 will be described.

  As shown in FIG. 15, light incident at an incident angle φs 1 near the upper end of the lens 221 and light incident at an incident angle φs 2 near the lower end of the lens 221 are collected by the lens 221. Light is incident on the aperture plate 270. Of the light that has entered the aperture plate 270, the light that has passed through the opening 271 of the aperture plate 270 enters the light receiving region 131 of the regular reflection light detector 130. As a result, the amount of light incident on the regular reflection light detector 130 can be increased, or the regular reflection light detector 130 having a small light receiving area 131 can be used. In the present embodiment, for example, the positions of the lens 221, the aperture plate 270, and the regular reflection light detector 130 are adjusted so that the incident angle φs1 is 7.8 ° and the incident angle φs2 is 2.2 °. Yes. Thus, in the present embodiment, the angle connecting the center of the irradiation area on the recording paper 20 and the center of the lens 221 is smaller than the angle serving as the center of the optical axis.

  As shown in FIG. 16, the shape of the opening 271 in the aperture plate 270 is such that the distance from the optical axis center corresponding to the incident angle φs1 is Ra, and the distance from the optical axis center corresponding to the incident angle φs2 is Rb. It is formed as follows. In addition, the distance Ra and the distance Rb are formed so that the distance in the direction perpendicular to the direction is Rc. The distance Ra is a distance on the side where the angle is smaller than the center of the optical axis, and the distance Ab is a distance on the side where the angle is larger than the center of the optical axis. Further, the light scattering on the recording paper 20 has a general Lambertian distribution in the lateral direction. Therefore, based on the result shown in FIG. It is formed to have a length corresponding to.

  In the present embodiment, the aperture plate 270 may not be provided as long as the positions of the lens 221 and the regular reflection light detector 130 are adjusted.

  Thus, in the present embodiment, since the lens 221 is provided, the reflected light from the recording paper 20 can be incident on the regular reflection light detector 130 without waste, and the SN ratio is improved and detection is performed. Accuracy can be improved.

  The contents other than the above are the same as in the first embodiment.

[Third Embodiment]
Next, a third embodiment will be described. In this embodiment, as shown in FIGS. 17 and 18, the position of the regular reflection light detector 130 is adjusted and installed. This eliminates the need to provide an aperture plate or the like in the present embodiment.

  As described above, as shown in FIG. 3, in the case of the low smoothness paper shown in the plain papers 3B and 3C, the angle indicating the high light intensity is shifted by about 5 ° from the position of the regular reflection. For this reason, the light receiving region 131 in the regular reflection light detector 130 is moved to the side with the smaller light receiving angle. Specifically, the regular reflection light detector 130 is installed so that the incident angle θ11 is 80 ° and the light receiving angle θ23 is 74 °.

  The contents other than the above are the same as in the first embodiment.

[Fourth Embodiment]
Next, a fourth embodiment will be described. The present embodiment is an image forming apparatus. A color printer 2000 as an image forming apparatus according to the present embodiment will be described with reference to FIG.

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

The printer control device 2090 includes a CPU, a program written in a code readable by the CPU, a ROM storing various data used when executing the program, a RAM as a working memory, an analog data An AD conversion circuit for converting the signal into digital data. The printer control device 2090 controls each unit in response to a request from the host device, and sends image information from the host device to the optical scanning device 2010.
The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a are used as a set and form an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image. Configure.

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

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

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

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is a surface to be scanned. Each photosensitive drum is rotated in the direction of the arrow in the plane of FIG. 19 by a rotation mechanism (not shown). Each charging device uniformly charges the surface of the corresponding photosensitive drum.

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

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

  As each developing roller rotates, the toner from the corresponding toner cartridge is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface of the developing roller and adheres thereto. 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 and conveys it to the registration roller pair 2056. The registration roller pair 2056 sends the recording paper toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color image on the transfer belt 2040 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing device 2050.

  In the fixing device 2050, heat and pressure are applied to the recording paper, thereby fixing the toner on the recording paper. The recording paper fixed here is sent to a paper discharge tray 2070 via a paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

  The optical sensor 2245 is used to detect the smoothness of the recording paper stored in the paper feed tray 2060. This optical sensor 2245 uses any one of the optical sensors in the first to third embodiments.

  In these optical sensors, the housing 160 is a resin box member, for example, an ABS box member, and the surface is blackened to reduce the influence of disturbance light and stray light. Here, in the XYZ three-dimensional orthogonal coordinate system, the direction orthogonal to the surface of the recording paper is described as the Z-axis direction, and the plane parallel to the surface of the recording paper is described as the XY plane. The optical sensor 2245 is assumed to be disposed on the + Z side of the recording paper.

  In addition, regarding a plurality of brands of recording paper that can be handled by the color printer 2000, optimum development conditions and transfer conditions at each station are determined in advance for the smoothness of the recording paper in a pre-shipment process such as an adjustment process. The determination result is stored in the ROM of the printer control device 2090 as a “development / transfer table”.

  The printer control device 2090 performs recording paper smoothness detection processing when the color printer 2000 is turned on or when the recording paper is supplied to the paper feed tray 2060.

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

  In the present embodiment, since the smoothness of the recording paper can be detected, an optimum fixing condition can be set for the smoothness of the recording paper, and an image forming apparatus with low power consumption can be provided.

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

  In the above embodiment, the brand of the recording paper may be specified during conveyance. In this case, the optical sensor 2245 is disposed in the vicinity of the conveyance path. For example, the optical sensor 2245 may be disposed in the vicinity of the conveyance path between the paper feed roller 2054 and the registration roller pair 2056. The object identified by the optical sensor 2245 is not limited to recording paper.

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

  In the above embodiment, the case where the image forming apparatus has four photosensitive drums has been described. However, the present invention is not limited to this.

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

  Further, the object identified by the optical sensor in the above-described embodiment is not limited to recording paper.

  As mentioned above, although the form which concerns on implementation of this invention was demonstrated, the said content does not limit the content of invention.

DESCRIPTION OF SYMBOLS 10 Light source 20 Recording paper 30 Regular reflection light detector 70 Aperture board 71 Aperture part 110 Light source 120 Lens 130 Regular reflection light detector 131 Light reception area 150 Processing part 151 I / O part 152 Arithmetic processing part 153 Average processing part 154 Storage part 160 Housing 170 Aperture plate 171 Opening 221 Lens 270 Aperture plate 271 Opening

JP 2002-340518 A JP 2003-292170 A JP 2005-156380 A JP-A-10-160687 JP 2006-62842 A JP 11-249353 A JP-A-8-5573 Japanese Patent No. 3349069 JP 2012-194445 A

Claims (6)

A light source;
A photodetector for irradiating the recording medium with light emitted from the light source and detecting the intensity of specularly reflected light in the recording medium ;
Have,
The angle θ1 of the optical axis connecting the light source and the center of the irradiation area formed on the recording medium with respect to the normal of the surface of the recording medium is 75 ° ≦ θ1 ≦ 85 ° ,
The angle θ2 of the optical axis connecting the center of the irradiation area formed on the recording medium and the photodetector is the same as the angle θ1 with respect to the normal of the surface of the recording medium, and the angle is larger than the angle θ2. The spread angle on the small side is θx1, the spread angle on the side larger than the angle θ2 is θx2,
Of the reflected light reflected in the irradiated area on the recording medium with respect to the normal of the surface of the recording medium, the angle θ of the light incident on the photodetector,

| Θx1 |> | θx2 |

θx1 + θ1 <θ <θx2 + θ1

It der to satisfy the,
The incorporation full angular width | θx1 | + | θx2 | is, 5 ° ≦ | θx1 | + | θx2 | optical sensor, characterized in ≦ 15 ° der Rukoto. Between the recording medium and the photodetector, an aperture plate having an opening is provided,
The aperture in the aperture plate has the angle θ2 as the optical axis center, the distance from the optical axis center on the side smaller than the angle θ2 as Aa1, and the light on the side larger in the angle θ2 When the distance from the axis center is Ab1,

Aa1> Ab1

The optical sensor according to claim 1, wherein the optical sensor is installed to be Between the recording medium and the photodetector, an aperture plate having an opening is provided,
The angle of the optical axis connecting the center of the irradiation area formed on the recording medium and the center of the opening in the aperture plate with respect to the normal of the surface of the recording medium is smaller than the angle θ1. The optical sensor according to claim 1, wherein the aperture plate is installed. A lens is provided between the recording medium and the photodetector,
The angle of the optical axis connecting the center of the irradiation area formed on the recording medium and the center of the lens with respect to the normal of the surface of the recording medium is smaller than the angle θ1. The optical sensor according to claim 1, wherein the optical sensor is installed. The recording medium is paper,
5. The optical sensor according to claim 1, wherein the smoothness of the recording medium is detected based on the intensity of light detected by the photodetector. 6. In an image forming apparatus for forming an image on the recording medium,
An image forming apparatus comprising the optical sensor according to any one of 1 to 5 above.

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