JP2007057892A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide at a high speed, high image quality printer by optimizing the paper type detection timing of a paper type detection optical sensor and comparatively accurately detecting the paper type, in a short time, thereby ensuring quick, accurate paper type detection, and optimally controlling image formation. <P>SOLUTION: The image forming apparatus includes an emission means set in the position where an arbitrary quantity of light can be emitted to the surface of a recording material from an oblique direction; a first light-receiving means set in the position, where the first light-receiving means can receive specularly reflected light from the light source; a second light-receiving means set at a position where light having an angle different from the incident angle of the emitting means can be detected; and a control means, capable of controlling the quantity of light emitted by the emission means and conditions for image formation. The image forming apparatus is characterized by detecting the quantities of light, by alternating the turning on and turning off of the light source. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser printer having a function of controlling printing conditions based on a result of a reflection type or transmission type optical sensor that detects reflected light or transmitted light of a recording material. Is.

  An image forming apparatus such as a copying machine or a laser printer includes a latent image carrier that carries a latent image, and a developing device that visualizes the latent image as a developer image by applying a developer to the latent image carrier. A transfer unit that transfers the developer image by the developing device to a recording material conveyed in a predetermined direction, and the recording material that has received the transfer of the developer image by the transfer unit is heated under predetermined fixing processing conditions. A fixing device for fixing the developer image on the recording material by applying pressure is provided.

  Conventionally, in such an image forming apparatus, for example, the size and type (hereinafter also referred to as a paper type) of a recording material as a recording material is set by a user on an operation panel or the like provided in the main body of the image forming apparatus. Then, control is performed so as to set the fixing processing conditions (for example, the fixing temperature and the conveyance speed of the recording material passing through the fixing device).

  Alternatively, a development condition, a transfer condition, a conveyance condition, or a fixing condition are variably controlled according to the type of the recording material by using a sensor for determining the recording material in the image forming apparatus.

  In particular, in the latter image forming apparatus, as proposed in Patent Document 1, for example, the light emitting element and the light emitted from the light emitting element are reflected by the detection surface and installed at a position where the reflected light is received. In some cases, a reflective optical sensor including the first received light sensor and a second received light sensor installed at an angle different from that of the received light sensor may be installed. With such a sensor, it is possible to discriminate between glossy paper with high glossiness and plain paper with low glossiness.

Since such an optical sensor is affected by dirt, a cleaning mechanism is provided or measures are taken to remove the dirt.
Japanese Patent Laid-Open No. 2-138805

  However, the image forming apparatus disclosed in Patent Document 1 has the following problems.

  In the case of detecting the light amount with high accuracy with the configuration of the optical sensor as in Patent Document 1, it is necessary to perform a preliminary operation until the light amount after the light amount change is stabilized due to a temperature rise of the light source or the like. Therefore, since a long time is required for the preliminary operation, there is a problem that the detection time becomes long.

  For the reasons described above, when detecting using a light source having a plurality of light amounts or using a plurality of light sources, it has been very difficult to detect the light amount accurately and stably. Further, when a cleaning mechanism is provided, the cost is increased by providing the mechanism.

  The purpose of the first, second, third, fourth, fifth, and sixth inventions according to the present application is to optimize the paper type detection timing of the paper type detection optical sensor and perform more accurate detection in a short time. It is an object of the present invention to provide an image forming apparatus that performs accurate paper type detection in a short time and performs optimal image formation control.

  In order to achieve the above object, the image forming apparatus of the first and third inventions according to the present application includes an irradiation unit installed at a position where the surface of the recording material can be irradiated with an arbitrary amount of light from an oblique direction, and a light source thereof A first light receiving means installed at a position capable of receiving the specularly reflected light, a second light receiving means installed at a position capable of detecting light having an angle different from the incident angle of the irradiation means, and the irradiation means And a control unit capable of controlling the light amount and the image forming conditions.

  The image forming apparatuses according to the second and fourth aspects of the present application are the first irradiating means installed at a position where the surface of the recording material can be irradiated with an arbitrary amount of light from an oblique direction, and the regular reflection light of the light source The first light receiving means installed at a position capable of receiving light, the second light receiving means installed at a position capable of detecting light having an angle different from the incident angle of the irradiation means, and the first to A second irradiating unit disposed on the opposite side of the second light receiving unit; and a control unit capable of controlling the light quantity and image forming conditions of the first and second irradiating units.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: a reflective optical sensor installed at a position where the surface of the recording material in the paper feed cassette can be detected; and a position of the recording material installed on the recording material conveyance path. Has a recognizable sensor.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: a reflective optical sensor installed at a position where the surface of the recording material can be detected on the recording material conveyance path; and the amount of light of the reflective optical sensor can be controlled. Control means.

  The first, second, third, fourth, fifth, and sixth inventions according to the present application repeatedly perform lighting with a plurality of light amounts or a plurality of light sources, and obtain a detection result in a stable light amount state or By adopting it, it is possible to stably detect the reflected or transmitted light quantity of the recording material in a short time, and it is possible to accurately detect the paper type in a short time, so that a stable high image quality can be output. An image forming apparatus can be realized.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 is a diagram that best represents a configuration necessary for achieving the present invention, and is a schematic cross-sectional view showing a schematic configuration of a reflective optical sensor that detects the surface property of a recording material and its base.

  As shown in FIG. 1, the sensor unit 123 includes an LED 1111 which is light irradiation means mounted obliquely (however, the light source may not be an LED, for example, a xenon tube or a halogen lamp), a first phototransistor (at this time) The light receiving element may be a photodiode or a CCD or CMOS sensor 1112, and the second phototransistor (the light receiving element may be a photodiode or a CCD or CMOS sensor 1113). At this time, the LED 1111 is mounted obliquely with respect to the detection surface as shown in FIG. However, you may irradiate diagonally with the light guide which is not shown in figure, without mounting LED diagonally.

  The sensor unit 123 is configured to maintain a certain distance from the detection surface by an intermediate member such as a roller 1116 (at this time, even if there is no intermediate member such as a roller, the detection surface and the sensor unit are maintained at a certain distance). Alternatively, it may be configured such that the detection surface is within the detectable range of the sensor).

  The second phototransistor 1113 is desirably in the opposite direction of the LED at the same angle as the incident angle α ° of the LED. The greater the angle of incidence, the greater the amount of specular reflection.

  The first phototransistor 1112 is preferably on the same side as the LED or at a location away from the incident angle of the LED. In the embodiment of FIG. 1, the incident angle of the first phototransistor 1112 is shown as 0 °.

  Light using the LED 1111 as a light source is applied to the surface of the recording material 1114. Regular reflection light and diffuse reflection light from the recording material 1114 are incident on the second phototransistor 1113 and the first phototransistor 1112, respectively. A CPU (not shown) (which may be an ASIC or DSP) capable of controlling the light amount of the LED repeats the lighting of the LED and the light amount change at a predetermined timing.

  First, the CPU emits the LED 1111 with a light amount for detection by the first phototransistor 1112. Subsequently, the second phototransistor 1113 emits light with a detection light amount (at this time, the light is temporarily turned off between the first detection light amount and the second detection light amount). May be). Then, the light emission with the above two kinds of light amounts is repeated (three kinds or more may be used instead of two kinds). Thereafter, the light amounts of the first phototransistor 1112 and the second phototransistor are detected at a predetermined timing necessary for paper type detection.

  FIG. 2 shows received light amounts of the second phototransistor 1113 and the first phototransistor 1112 when the LED light amount at this time is changed.

  The ratio between the output of the second phototransistor 1113 and the output of the first phototransistor 1112 is detected, and the surface property of the recording material is read. Among OHT, gloss paper, and plain paper, OHT has the highest glossiness and the lowest ratio of diffuse reflection light to regular reflection light. Next, the diffuse reflection light with respect to gloss paper, plain paper and regular reflection light increases.

  FIG. 3 is a schematic cross-sectional view in the case of detecting the ground.

  When no paper is set in the paper cassette, the light emitted from the LED is applied to the underlying surface of the detection portion. The regular reflection light and the diffuse reflection light from the base enter the second phototransistor 1113 and the first phototransistor 1112 respectively.

  FIG. 4 is a diagram illustrating a configuration of the image forming apparatus.

  In the figure, 101 is an image forming apparatus, 102 is a paper cassette, 126 is a paper tray, 103 and 125 are paper feed rollers, 104 is a transfer belt drive roller, 105 is a transfer belt, and 106 to 109 are yellow, magenta, cyan, and black. Photosensitive drums 110 to 113 are transfer rollers, 114 to 117 are yellow, magenta, cyan, and black cartridges, 118 to 121 are yellow, magenta, cyan, and black optical units, and 122 is a fixing unit.

  The image forming apparatus uses an electrophotographic process to transfer a yellow, magenta, cyan, and black image on a recording material in an overlapping manner, and heat-fixes the toner image with a fixing roller based on temperature control.

  Each color optical unit is configured to form a latent image by exposing and scanning the surface of each photosensitive drum with a laser beam, and a series of these image forming operations is performed from a predetermined position on the recording material to be conveyed. The scanning is controlled in synchronization so that the image is transferred.

  Further, the image forming apparatus feeds and conveys a recording material, which is a recording material, a transfer belt drive motor that drives a transfer belt drive roller, a photosensitive drum drive motor that drives each color photosensitive drum and the transfer roller, A fixing drive motor for driving the fixing roller is provided.

  A control CPU (not shown) provided in the image forming apparatus applies a desired amount of heat to the recording material by the fixing unit 122 to fuse and fix the toner image on the recording material.

  Next, the operation of the control CPU will be described with reference to FIG.

  FIG. 5 is a diagram showing the configuration of each unit controlled by the control CPU.

  In the figure, 10 is a CPU, 11 is a paper type detection sensor, 12 to 15 are equipped with a polygon mirror, a motor and a laser, and scans the laser on the surface of the photosensitive drum to draw a desired latent image, 16 A paper feed motor for transporting the recording material, 17 is a paper feed solenoid used to start driving a paper feed roller for feeding the recording material, and 19 is primary charging, development, and primary required for the electrophotographic process. High voltage power source for controlling transfer and secondary transfer bias, 20 is a drum drive motor for driving the photosensitive drum and transfer roller, 21 is a belt drive motor for driving the rollers of the transfer belt and the fixing unit, and 22 is a fixing unit and a low pressure. The power supply unit is controlled by a control CPU to monitor the temperature with a thermistor (not shown) and keep the fixing temperature constant.

  Reference numeral 23 denotes an ASIC, which performs motor speed control inside the paper type detection sensor 11 and the optical units 12 to 15 and speed control of the paper feed motor based on an instruction from the control CPU 10.

  The speed control of the motor is performed by detecting a tack signal from a motor (not shown) and outputting an acceleration or deceleration signal to the motor so that the interval between the tack signals becomes a predetermined time. For this reason, it is more advantageous that the control circuit is composed of a hardware circuit of the ASIC 23, so that the control load on the CPU 10 can be reduced.

  At a predetermined timing for detection by the paper type detection sensor, the LED is turned on from the output port of the CPU 10 or the ASIC 23. The output MSSR of the second phototransistor 1113 and the output MSDR of the first phototransistor 1112 are input to the AD port of the CPU 10 or ASIC 23, and the CPU 10 or the ASIC 23 recognizes the amount of light received by the ASIC 23 phototransistor. Thereafter, based on the control flow described later, the type of the medium is determined from the ratio of the regular reflection light and the irregular reflection light, and the respective calculation results are stored in a register in the CPU 10 or the ASIC 23. Further, when the amount of received light is extremely low at this time, it is determined that the LED has failed.

  When the control CPU 10 receives a print command in response to an instruction from a host computer (not shown), the paper type detection sensor 11 determines the presence / absence of a recording material and the state of the cassette. The motor 20 and the belt drive motor 21 are driven, and the paper feed solenoid 17 is driven to convey the recording material to a predetermined position. The CPU 10 reads the register in the ASIC 23, determines the type of the fed recording material, and variably controls the developing bias condition of the high voltage power source 19 according to the result.

  For example, in the case of so-called rough paper where the surface fibers of the recording material are rough, control is performed to prevent toner scattering by lowering the developing bias than plain paper and suppressing the amount of toner adhering to the surface of the recording material. This is because the amount of toner adhering to the surface of the recording material is large especially in the case of rough paper, so that the problem that the image quality deteriorates due to the scattering of the toner due to the paper fibers is solved.

  Further, the CPU 10 determines the type of the fed recording material, and variably controls the temperature condition of the fixing unit 22 according to the result.

  This is particularly effective in the case of OHT, when the fixing property of the toner adhering to the surface of the recording material is poor, the OHT permeability is deteriorated.

  Further, the CPU 10 determines the type of the fed recording material, and variably controls the recording material conveyance speed according to the result. The variable control of the conveyance speed is realized by the CPU 10 setting the speed control register value of the ASIC 23 that controls the speed control.

  For example, the fixing temperature condition is changed for a transmissive recording material such as OHT, and the transmissive recording material is controlled by increasing the fixing temperature in order to increase the transparency. Alternatively, the recording material conveyance speed may be changed and controlled depending on whether the type of the recording material is a transmissive type.

  Alternatively, in the case of glossy paper or the like, it is possible to improve the image quality by improving the fixability of the toner adhering to the surface of the recording material and increasing the gloss.

  FIG. 6 shows a control flow of light amount adjustment by paper.

  In order to detect the paper type, it is necessary to adjust in advance so that the sensor emits light with a correct light amount.

  Adjustment is performed by the output of a reference chart (which may be paper). At a predetermined timing, the CPU or ASIC turns on the LED after confirming that there is a cassette and paper (chart).

  If there is no cassette or paper, the adjustment ends with an adjustment failure.

  Subsequently, the CPU or ASIC takes in the output from the second phototransistor and the output from the first phototransistor, and adjusts and saves each LED light emission amount so that each output becomes a constant output. To do. However, this adjustment is not necessary when a single unit is equipped with an adjustment mechanism and adjustment is performed in a separate process.

  Next, initial background data α is acquired. FIG. 7 shows an initial background data detection flow.

  At a predetermined timing, the CPU or ASIC turns on the LED after confirming that there is a cassette and no paper. If there is no cassette or there is paper, the process ends without performing detection. The CPU or ASIC takes in the output from the second phototransistor and the output from the first phototransistor, and outputs the second phototransistor output (α2) of the initial background data and the first of the initial background data. The phototransistor output (α1) is stored.

  In the same manner, the second photo and transistor output (β2) on the latest base and the first phototransistor output (β1) on the latest base at the timing when the paper is not in the cassette and the base can be detected. Import and save.

  FIG. 8 shows a flow at the time of detection.

  The detection flow will be described. At a predetermined timing, the CPU or ASIC turns on the LED after confirming that there is a cassette and paper. The CPU or ASIC captures the output (θ2) from the second phototransistor and the output (θ1) from the first phototransistor, averages it with the previously stored detection result, and stores it. . At that time, the CPU or ASIC confirms that the background data (α1, α2) at the time of shipment and the immediately previous background data (β1, β2) are stored. The detection result is corrected by the following equation with a coefficient γ proportional to the rate.

  FIG. 7 shows the amount of light received by the first phototransistor after the correction, and FIG. 8 shows the amount of light received by the second phototransistor. Further, FIG. 9 shows the ratio of the amount of light received by the second phototransistor to the amount of light received by the first phototransistor at that time.

  The amount of light is changed to an amount appropriate for the reflectance of the paper, and the paper type discrimination measurement is performed. FIG. 9 shows the ratio of the amount of light received by the second phototransistor to the amount of light received by the first phototransistor at that time.

  In the paper type discrimination, the ratio of the amount of light received by the second phototransistor to the amount of light received by the first phototransistor is compared with the threshold value 9-1, and if the ratio is lower than the threshold value 9-1, the type of media is Judge as plain paper. Further, when it is smaller than the threshold value 9-2 and larger than the threshold value 9-1, it is determined that the gloss paper has a high glossiness, and when it is larger than the threshold value 9-2, it is determined as OHT. From this ratio, the type of the recording material is determined, and based on the determination result, the print mode is set and the LED is turned off. After the LED is turned off, the detection is terminated and the system waits until the next detection timing.

  By repeating the above operation at a predetermined timing, an appropriate print mode can be set.

  As described above, in this embodiment, the surface property of the recording material is detected with high accuracy by the paper type detection sensor, and as a result, the CPU or ASIC determines the developing condition of the high voltage power source, the control temperature condition of the fixing unit, or the recording material. The conveyance speed is variably controlled.

  Since the operation content of the image forming apparatus is the same as that of the first embodiment, the same reference numerals are used to denote the same parts as in the first embodiment, and the description thereof is omitted, which is different from the first embodiment. Only the configuration and detection method of paper type detection will be described.

  FIG. 10 is a schematic cross-sectional view showing a schematic configuration of a reflective optical sensor for detecting the surface property of a recording material, a transmitted light detection light source for detecting the transmittance of the recording material, and a light transmission plate.

  As shown in FIG. 10, the sensor unit 123 includes an LED 1111 which is light irradiation means mounted obliquely (however, the light source may not be an LED, for example, a xenon tube or a halogen lamp), a first phototransistor (this Sometimes the light receiving element may be a photodiode or a CCD or CMOS sensor) 1112, the second phototransistor (at this time the light receiving element may be a photodiode or a CCD or CMOS sensor) 1113, a transmitted light detecting LED 1117, a light transmitting plate 1118. At this time, as shown in FIG. 10, the transmitted light detection LED 1117 is installed on the opposite side of the first and second phototransistors with respect to the recording material, and the amount of light emitted from the transmitted light detection LED 1117 is the light transmission plate. It passes through 1118 and is installed at a position that can be detected by a phototransistor.

  Light using the LED 1111 as a light source is applied to the surface of the recording material 1114. The specularly reflected light and diffusely reflected light from the recording material 1114 are incident on the second phototransistor 1113 and the first phototransistor 1112, respectively, and the transmitted light detection LED 1117 is transmitted through the light transmitting plate 1118 and the recording material 1114. The light enters the first phototransistor 1112. A CPU (not shown) (which may be an ASIC or DSP) capable of controlling the light amount of the LED repeats the lighting of the LED and the light amount change at a predetermined timing.

  First, the CPU emits the LED 1111 with a light amount for detection by the first phototransistor 1112. Subsequently, the second phototransistor 1113 emits light with a detection light amount (at this time, the light is temporarily turned off between the first detection light amount and the second detection light amount). May be). Subsequently, the LED 1111 is turned off and the transmitted light detection LED 1117 is turned on. The above series of operations is repeated. (At this time, the amount of transmitted light may be changed.) Thereafter, the amounts of light of the first phototransistor 1112 and the second phototransistor are detected at a predetermined timing required for paper type detection.

  FIG. 11 shows the amount of light received by the first phototransistor 1112 by the transmitted light detection LED at this time. The transmittance of the recording material is obtained from the amount of received light. Among OHT, thin paper, plain paper, and thick paper, OHT has the highest transmittance and receives the most transmitted light. Next, the amount of transmitted light decreases in the order of thin paper, plain paper, and thick paper.

  Since the operation content of the image forming apparatus is the same as that of the first embodiment, the same reference numerals are used to denote the same parts as in the first embodiment, and the description thereof is omitted, which is different from the first embodiment. Only the configuration and detection method of paper type detection will be described.

  First, the paper type detection sensor 124 installed on the conveyance path in the schematic cross-sectional view of the image forming apparatus in FIG. 4 will be described.

  FIG. 12 shows a chart showing the detection timing of the sensor.

  When a CPU (not shown) receives a print start signal from a controller (not shown), it starts a print preparation operation. After the start timing 601, the driving of the optical reflection sensor 124 for detecting the paper type is started 605.

  First, the CPU emits the LED 1111 with a light amount for detection by the first phototransistor 1112. Subsequently, the second phototransistor 1113 emits light with a detection light amount (at this time, the light is temporarily turned off between the first detection light amount and the second detection light amount). May be). Subsequently, the LED 1111 is turned off and the transmitted light detection LED 1117 is turned on. The above series of operations is repeated.

  Thereafter, the CPU starts a printing operation, and starts the paper type detection 603 after the recording material reaches a position where the optical reflection sensor 124 for detecting the paper type can be detected. After the detection, the driving of the sensor is stopped 606.

  Because a certain cycle is started during the print preparation operation, detection can be performed in a state where the temperature of the sensor LED is stable, and detection can be performed at the same timing as detection timing during continuous printing. The variation in the detection result due to the printing conditions can be suppressed, and the detection accuracy can be improved as compared with the case of simply detecting.

  Next, the paper type detection sensor 123 installed in the paper feed cassette in the schematic cross-sectional view of the image forming apparatus in FIG. 4 will be described.

  A CPU (not shown) starts 601 a print preparation operation and printing in a print mode that has already been determined. The recording material is fed, reaches the top sensor, and the timing 602 when the sensor reacts, or after a certain time from the timing, the paper type detection sensor 123 installed in the cassette is then set in the cassette. The paper set in the cassette is detected 603 at a timing at which the recording material being detected can be detected. After the detection, the driving of the sensor is stopped 606.

  As a result, detection can be performed in a state where the temperature of the LED of the sensor is stable, and detection can be performed at the same timing as the detection timing during continuous printing, so variation in detection results due to printing conditions can be suppressed. The detection accuracy can be improved compared to the case where the detection is simply performed.

It is typical sectional drawing which shows schematic structure which concerns on Example 1 of this invention. It is a graph which shows the recording material reflected light quantity which concerns on Example 1 of this invention. It is typical sectional drawing which shows schematic structure which concerns on Example 1 of this invention. 1 is a schematic cross-sectional view illustrating an image forming apparatus according to Embodiment 1 of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus according to Embodiment 1 of the present invention. It is a flowchart which shows the control flow which concerns on Example 1 of this invention. It is a flowchart which shows the control flow which concerns on Example 1 of this invention. It is a flowchart which shows the control flow which concerns on Example 1 of this invention. It is a figure which shows the light reception light quantity of a 2nd phototransistor with respect to the light reception light quantity of the 1st phototransistor which concerns on Example 1 of this invention. It is a schematic cross section which shows schematic structure based on Example 2 of this invention. It is a figure which shows the light-receiving light quantity of the 1st phototransistor with respect to LED for the transmitted light detection which concerns on Example 2 of this invention. It is a timing chart which shows the detection timing which concerns on Example 3 of this invention.

Explanation of symbols

10 Control CPU
11 Paper type detection sensor 16 Paper feed motor 17 Paper feed solenoid 19 High voltage power supply 20 Drum drive motor 21 Belt drive motor 22 Fixing unit 23 ASIC
DESCRIPTION OF SYMBOLS 101 Image forming apparatus 102 Paper cassette 103 Paper feed roller 104 Transfer belt drive roller 105 Transfer belt 106-109 Photosensitive drum 110-113 Transfer roller 114-117 Cartridge 118-121 Optical unit 122 Fixing unit 123 Sensor unit 124 Sensor unit 125 Paper feed Roller 126 Paper tray 1111 LED
1112 First phototransistor 1113 Second phototransistor 1114 Recording material 1115 Base 1116 Roller 1117 Transmitted light detection LED
1118 Light transmission plate

Claims (6)

Irradiation means installed at a position where the surface of the recording material can be irradiated with an arbitrary amount of light from an oblique direction, a first light receiving means installed at a position capable of receiving specular reflection light of the light source, and incidence of the irradiation means In an image forming apparatus comprising: a second light receiving unit installed at a position where light having an angle different from the angle can be detected; and a control unit capable of controlling a light amount and image forming conditions of the irradiation unit.
An image forming apparatus characterized in that, in the irradiating means, at least two types of light quantities are repeatedly changed at least twice at a predetermined interval, and a detection result is acquired at a predetermined timing. A first irradiating means installed at a position where the surface of the recording material can be irradiated with an arbitrary amount of light from an oblique direction, a first light receiving means installed at a position where the specularly reflected light of the light source can be received, and irradiation A second light receiving means installed at a position where light having an angle different from the incident angle of the means can be detected, and a second irradiation means installed on the opposite side of the recording material from the first or second light receiving means. And an image forming apparatus having control means capable of controlling the light quantity and image forming conditions of the first and second irradiation means,
An image forming apparatus characterized in that in the first irradiation unit and the second irradiation unit, a light amount is repeatedly changed at a predetermined interval, and a detection result is acquired at a predetermined timing. Irradiation means installed at a position where the surface of the recording material can be irradiated with an arbitrary amount of light from an oblique direction, a first light receiving means installed at a position capable of receiving specular reflection light of the light source, and incidence of the irradiation means Second light receiving means installed at a position where light having an angle different from the angle can be detected, and the first and second light receiving means can receive light when there is no recording material on the optical path of the second irradiation means. In an image forming apparatus having a diffusing material installed at a position, and a control unit capable of controlling a light amount and image forming conditions of the irradiation unit,
An image forming apparatus characterized in that at the time of detecting the diffusing material, at least two types of light quantities are repeatedly changed at least twice at a predetermined interval in the irradiating means, and a detection result is acquired at a predetermined timing. . A first irradiating means installed at a position where the surface of the recording material can be irradiated with an arbitrary amount of light from an oblique direction, a first light receiving means installed at a position where the specularly reflected light of the light source can be received, and irradiation A second light receiving means installed at a position where light having an angle different from the incident angle of the means can be detected, and a second irradiation means installed on the opposite side of the recording material from the first or second light receiving means. And when there is no recording material on the optical path of the second irradiating means, the diffusing material installed at a position where the first and second light receiving means can receive light, and the light amounts of the first and second irradiating means And an image forming apparatus having a control means capable of controlling image forming conditions.
An image forming apparatus characterized in that, at the time of detecting the diffusing material, the first irradiating unit and the second irradiating unit repeatedly change the light amount at a predetermined interval and acquire a detection result at a predetermined timing. In an image forming apparatus having a reflective optical sensor installed at a position where the surface of a recording material in a paper feed cassette can be detected, and a sensor capable of recognizing the position of the recording material installed on a recording material conveyance path,
An image forming apparatus, wherein a detection timing of a recording material set in a cassette next to the recording material is determined based on a sensor output capable of recognizing a position of the recording material being conveyed in the apparatus. . In an image forming apparatus, comprising: a reflective optical sensor installed at a position where the surface of the recording material can be detected on the recording material conveyance path; and a control unit capable of controlling the amount of light of the reflective optical sensor.
The control unit starts light emission at a predetermined light emission cycle during an image formation preparation operation, and acquires a detection result after the recording material reaches the reflective optical sensor. apparatus.

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