JP2007276355A - Quantity-of-light detection circuit, quantity-of-light measuring apparatus, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quantity-of-light detection circuit, a quantity-of-light measuring apparatus, and an image forming apparatus, which obtain a quantity-of-light measurement result as desired regardless of the sensitivity of a light detection element. <P>SOLUTION: A sensor pixel circuit (130) is provided with: a quantity-of-light sensor (57) which is serially connected to a charge amplifier (150), and generate a current according to a quantity-of-light irradiated from an organic electroluminescence element (63); a capacitor (131) connected in parallel to the quantity-of-light sensor (57); and a selection transistor (132)which is connected between a parallel circuit having the quantity-of-light sensor (57) and the capacitor (131), and the charge amplifier (150), and opens and closes an electric connection between the parallel circuit and the charge amplifier (150). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light amount detection circuit, a light amount measurement device, and an image forming apparatus.

  A photosensitive body charged in advance at a predetermined potential is exposed according to image information to form an electrostatic latent image, the electrostatic latent image is developed with toner, and the visualized toner image is transferred to a recording paper. As an exposure device used in an image forming apparatus applying the so-called electrophotographic process to obtain an image by heating and fixing, a light beam using a laser diode as a light source passes through a rotating polygonal mirror called a polygon mirror on the photoreceptor. Each light emitting unit is formed using a method of forming an electrostatic latent image by scanning, and a light emitting element array in which light emitting elements (hereinafter referred to as LEDs) and organic electroluminescent materials are arranged in a line. There is known a system in which an electrostatic latent image is formed on a photoreceptor by individually controlling lighting (ON / OFF).

  In general, an exposure apparatus including a light-emitting element array using LEDs or organic electroluminescent materials as a constituent element selectively illuminates each light-emitting element in the very vicinity of the photoconductor to irradiate the photoconductor with exposure light. The image forming apparatus equipped with a laser diode has no moving parts like a rotating polygon mirror in an image forming apparatus using a laser diode, and has high reliability and quietness. A large optical space serving as a path for the image forming apparatus is unnecessary, and the image forming apparatus can be downsized.

  In particular, an exposure apparatus equipped with an organic electroluminescence element as a light emitting element integrates a drive circuit composed of a switching element made of a thin film transistor (hereinafter referred to as TFT) and an organic electroluminescence element on a substrate such as glass. Therefore, the structure and manufacturing process are simple, and there is a possibility that further downsizing and cost reduction can be realized as compared with an exposure apparatus in which an LED is mounted as a light emitting element.

However, on the other hand, it is known that the organic electroluminescence element undergoes so-called light quantity deterioration in which the light emission luminance gradually decreases with the driving thereof. An organic electroluminescence element applied to a general display device or the like has a light emission luminance of about 1000 [cd / m ² ] at most, but is applied to an exposure device mounted on an image forming apparatus such as an electrophotographic apparatus. For example, assuming that the specifications of an image forming apparatus are 600 dpi (dot / inch) and 20 ppm (pages / minute), the organic electroluminescence element is required to have an emission luminance of 10,000 [cd / m ² ] or more. The driving conditions are very severe with high voltage and large current. For this reason, the organic electroluminescence element applied to the exposure apparatus is more susceptible to the deterioration of the amount of light than that applied to the display apparatus, so that the exposure amount of each organic electroluminescence element is equal to the initial state. In order to maintain it, some exposure correction is required.

  It is also known that the light emission luminance of an organic electroluminescence element has temperature dependence. This temperature dependency is determined by the organic material constituting the organic electroluminescence element, and can have both positive characteristics and negative characteristics. The above-described image forming process of the electrophotographic apparatus includes a step of fixing the toner image on the recording paper by heat and pressure. Since the apparatus has a heat source capable of generating a large amount of heat, the temperature change inside the apparatus is prevented. Along with this, the emission luminance of the organic electroluminescence element changes. Also in this case, exposure amount correction for correcting the exposure amount of each organic electroluminescence element is required.

  In addition, since it is difficult to prevent variation in emission luminance between individual organic electroluminescence elements, exposure amount correction is also required to prevent variation in exposure amount between elements.

  With regard to exposure amount correction, for example, a configuration disclosed in Patent Document 1 is known for an image forming apparatus equipped with an exposure apparatus using a conventional organic electroluminescence element. The exposure apparatus in Patent Document 1 has a configuration in which a light receiving sensor is arranged on a glass substrate on which an organic electroluminescence element is formed, and the exposure amount of each organic electroluminescence element is detected by the light receiving sensor.

  Further, according to Patent Document 1, the exposure amount Pgn of the n-th organic electroluminescence element in the exposure apparatus is measured in advance by an inspection jig, and at this time, the exposure amount Phn is also measured by the above-described light receiving sensor. Based on this, a correction coefficient Pgn / Phn is calculated, and the correction coefficient is stored in a storage unit mounted on the exposure apparatus or the image forming apparatus. Then, after incorporating the exposure apparatus into the image forming apparatus, by appropriately determining the new drive current of the organic electroluminescence element based on the light amount detection result by the light receiving sensor described above and the correction coefficient stored in the storage means, The initial exposure amount of the organic electroluminescence device can always be maintained.

Japanese Patent Laid-Open No. 2004-082330

  In such an image forming apparatus, in order to perform high-precision light amount correction, a light amount detection element is provided for each organic electroluminescence element, and each light amount detection element measures the light amount of each organic electroluminescence element. It is desirable.

  By the way, in such an image forming apparatus, the demand for downsizing of the apparatus is increasing. Therefore, an element array composed of a plurality of light emitting elements is arranged on a glass substrate, and a light quantity detecting element for detecting light output from the light emitting elements is integrated to form the light quantity detecting element. A configuration in which the light is emitted to the photosensitive member is also conceivable. In that case, it is necessary to use a material having a high light transmittance, such as polysilicon, for the light detection element. However, a photodetecting element using a material having a high light transmittance has a low sensitivity.

  The present invention has been made in view of the above circumstances, and provides a light amount detection circuit, a light amount measurement device, and an image forming apparatus capable of obtaining a desired light amount measurement result regardless of the sensitivity of the light detection element. The purpose is to do.

  The present invention provides, firstly, a photodetecting element that is connected in series to a charge amplifier and generates a current corresponding to the amount of light irradiated, a capacitive element connected in parallel with the photodetecting element, and the photodetecting element Provided is a light amount detection circuit including a parallel circuit having a capacitor and a capacitor and a selection transistor connected between the charge amplifier and opening and closing an electrical connection between the parallel circuit and the charge amplifier. It is.

  With this configuration, the amount of light applied to the light amount detection element can be reflected in the charge accumulated in the capacitor element. Then, the selection transistor allows the connection between the capacitive element and the charge amplifier to be turned on and off, and the target period of the light quantity detection can be controlled according to the sensitivity of the light detection element and the required light quantity measurement accuracy. The light quantity measurement result can be obtained.

  The present invention secondly provides the light quantity detection circuit according to the first aspect, wherein the light detection element is provided with a polycrystalline silicon.

  With this configuration, a material having high light transmittance such as polycrystalline silicon can be applied to the light detection element.

  Thirdly, the present invention includes the light amount detection circuit according to the first or second aspect and the charge amplifier, and the selection transistor is arranged between the parallel circuit and the charge amplifier in a first period. Electrically connected to electrically disconnect between the parallel circuit and the charge amplifier in a second period starting from the end of the first period, and starting from the end of the second period In the third period, the parallel circuit and the charge amplifier are electrically connected, and in the first period, the charge from the charge amplifier is accumulated in the capacitive element, and in the third period, the charge amplifier A light quantity measuring device is provided in which the charge consumed by the photodetecting element from the end of the first period to the end of the third period is transferred to the charge amplifier.

  With this configuration, by performing charge transfer between the charge amplifier and the light amount detection circuit, it is possible to drive a light amount detection operation such as start and end of light amount detection and reading of the light amount measurement result.

  Fourthly, the present invention provides the light amount measuring apparatus according to the third aspect, wherein the charge amplifier has two input signal terminals, a non-inverting input terminal and an inverting input terminal, and one output signal terminal. An amplifier, an amplifier capacitive element connected between one input terminal and an output terminal of the operational amplifier, and an electrical connection between both ends of the first capacitive element connected in parallel with the first capacitive element A charge / discharge selection transistor that opens and closes a connection, and the charge / discharge selection transistor electrically connects both ends of the first capacitive element at least in the first period, and the third period There is provided a light amount measuring apparatus that electrically cuts off connection between both ends of the first capacitive element.

  With this configuration, it is possible to drive a light amount detection operation such as start and end of light amount detection and reading of a light amount measurement result using an integration circuit using an operational amplifier.

  The fifth aspect of the present invention is the light amount measuring apparatus according to the third or fourth aspect, wherein the charge amplifier is connected to a plurality of the light amount detection circuits connected in parallel to each other, The light amount detection operation with one unit from the start of the period to the end of the third period is performed independently for each light amount detection circuit, and the third period in the light amount detection operation between the light amount detection circuits. The light quantity measuring device performed at the timing which does not overlap is provided.

  With this configuration, it is possible to perform light amount measurement using a single charge amplifier for a plurality of light amount detection circuits, so that the circuit scale can be reduced and the cost of the light amount measurement device can be reduced.

  Sixthly, the present invention provides the light quantity measuring device according to the fifth aspect, wherein the plurality of charge amplifiers each connected to the plurality of light quantity detection circuits are provided, and the operation is performed for each charge amplifier. The light quantity measuring device which advances simultaneously is provided.

  With this configuration, since the light quantity measurement operation is performed simultaneously between the plurality of charge amplifiers, the time required for the light quantity measurement can be shortened and the light quantity can be efficiently measured for the plurality of light quantity detection circuits.

  Seventhly, the present invention provides the light quantity measuring device according to any one of the third to sixth aspects, wherein the period from the start of the second period to the end of the third period is a light quantity detection. There is provided a light amount measuring apparatus having a longer period than an exposure period in a target light emitting element.

  With this configuration, for example, even when the sensitivity of the light quantity detection element is low or the exposure period of the light emitting element is short, the light quantity detection period is controlled using the selection transistor so that it is longer than the exposure period. Measurement results can be obtained.

  Eighthly, the present invention includes a plurality of light emitting elements that expose an image carrier to form an image, and the light quantity measuring device according to any one of the third to seventh aspects, and the light quantity measuring device includes: The light quantity detection circuit is provided corresponding to each light emitting element, and an image forming apparatus for detecting the light quantity of light emitted from the light emitting element is provided.

  With this configuration, a desired light quantity measurement result can be obtained for each of the plurality of light emitting elements that form an image by exposing the image carrier.

  The ninth aspect of the present invention is the image forming apparatus according to the eighth aspect, wherein the light emitting elements are arranged and formed in a main scanning direction, and the light quantity measuring device is provided for each predetermined number in the main scanning direction. An image forming apparatus that performs light amount measurement on one light emitting element in parallel is provided.

  With this configuration, since one light emitting element only needs to emit light for each predetermined number in the main scanning direction, the influence of light from adjacent light emitting elements can be suppressed and highly accurate light amount detection can be performed.

  The tenth aspect of the present invention is the image forming apparatus according to any one of the eighth and ninth aspects, wherein the light emission is measured with reference to the light amount of the light emitted by the light emitting element measured by the light amount measurement device. An image forming apparatus further including a light amount correction unit that corrects the light amount of light emitted from the element is provided.

  With this configuration, since the light amount correction is performed using the light amount measurement result measured for each issuing element, it is possible to provide an image forming apparatus that performs accurate light amount correction.

  An eleventh aspect of the present invention is the image forming apparatus according to any one of the eighth to tenth aspects, wherein the light emitting element is provided with an organic electroluminescent element. .

  With this configuration, it is possible to reduce the size and cost by using the organic electroluminescence element, and it is possible to detect each light quantity of the organic electroluminescence element with a desired accuracy. It is possible to provide a high-quality image forming apparatus that can cope with deterioration and the like.

  According to the present invention, it is possible to provide a light amount detection circuit, a light amount measurement apparatus, and an image forming apparatus that can obtain a desired light amount measurement result regardless of the sensitivity of the light detection element.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments relating to the basic configuration of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, an image forming apparatus 1 has four color development stations, a yellow development station 2Y, a magenta development station 2M, a cyan development station 2C, and a black development station 2K, arranged in a stepwise manner in the vertical direction. Is provided with a paper feed tray 4 in which a recording paper 3 as a recording medium is accommodated, and at a position corresponding to each of the developing stations 2Y to 2K, a conveyance path of the recording paper 3 supplied from the paper feed tray 4 is provided. The recording paper transport path 5 is configured in the vertical direction from the top to the bottom.

  The developing stations 2Y to 2K form toner images of yellow, magenta, cyan, and black sequentially from the upstream side of the recording paper conveyance path 5, and the yellow developing station 2Y is photosensitive to the photoreceptor 8Y and the magenta developing station 2M. 8M, cyan developing station 2C includes a photosensitive member 8C, black developing station 2K includes a photosensitive member 8K, and each developing station 2Y to 2K includes a series of electrophotographic systems such as a developing sleeve and a charger described later. The member which implement | achieves the image development process in is included.

  Further, exposure devices 13Y, 13M, 13C, and 13K for exposing the surfaces of the photoreceptors 8Y to 8K to form electrostatic latent images are disposed below the developing stations 2Y to 2K.

  The developing stations 2Y to 2K are different in the color of the filled developer, but the configuration is the same regardless of the development color. Therefore, the development is performed except when it is particularly necessary to clarify the following explanation. A description will be given without specifying specific colors such as the station 2, the photoconductor 8, and the exposure device 13.

  FIG. 2 is a configuration diagram showing the periphery of the developing station 2 in the image forming apparatus 1 of the present invention. In FIG. 2, the developing station 2 is filled with a developer 6 which is a mixture of carrier and toner. 7a and 7b are stirring paddles for stirring the developer 6. The toner in the developer 6 is charged to a predetermined potential by friction with the carrier by the rotation of the stirring paddles 7a and 7b. The inside of 2 is sufficiently stirred and mixed. The photoreceptor 8 is rotated in the direction D3 by a driving source (not shown). A charger 9 charges the surface of the photoconductor 8 to a predetermined potential. Reference numeral 10 denotes a developing sleeve, and 11 denotes a thinning blade. The developing sleeve 10 has a magnet roll 12 having a plurality of magnetic poles formed therein. The layer thickness of the developer 6 supplied to the surface of the developing sleeve 10 is regulated by the thinning blade 11 and the developing sleeve 10 is rotated in the direction D4 by a driving source (not shown). The developer 6 is supplied to the surface of the developing sleeve 10 by the action of the above, and an electrostatic latent image formed on the photoconductor 8 is developed by an exposure device 13 described later, and the developer 6 not transferred to the photoconductor 8 is developed. Collected in the developing station 2.

  In this embodiment, as will be described later, the developing station 2 is configured to be movable in the horizontal direction at a predetermined timing for correcting the light emission amount of the light emitting element (organic electroluminescence element). This configuration is illustrated in FIG. 16, but in FIG. 2, the development contact cam 210, the tension spring 211, the development side spring-loaded boss 212, and the main body-side spring-loaded boss 213 shown in FIG. Omitted.

  Reference numeral 13 denotes an exposure apparatus. The exposure device 13 has a light emitting element array in which organic electroluminescence elements as exposure light sources are arranged in a line at a resolution of 600 dpi (dot / inch), and the photosensitive member 8 charged to a predetermined potential by the charger 9 is provided. On the other hand, an electrostatic latent image of maximum A4 size is formed by selectively turning on / off the organic electroluminescence element according to the image data. When a predetermined potential (developing bias) is applied to the developing sleeve 10, a potential gradient is generated between the electrostatic latent image portion and the developing sleeve 10. Then, the Coulomb force acts on the toner in the developer 6 that is supplied to the surface of the developing sleeve 10 and is charged to a predetermined potential, and only the toner out of the developer 6 adheres to the photoreceptor 8, and electrostatic The latent image is visualized.

  As will be described in detail later, the exposure apparatus 13 is provided with a light amount sensor as a light amount measuring means for measuring the light emission amount of the organic electroluminescence element.

  Reference numeral 16 denotes a transfer roller. The transfer roller 16 is provided at a position facing the recording paper conveyance path 5 with respect to the photoconductor 8, and is rotated in the direction D5 by a driving source (not shown). A predetermined transfer bias is applied to the transfer roller 16, and the toner image formed on the photoconductor 8 is transferred to the recording paper 3 conveyed through the recording paper conveyance path 5.

  Hereinafter, returning to FIG.

  A toner bottle 17 stores yellow, magenta, cyan, and black toners. A toner transport pipe (not shown) is provided from the toner bottle 17 to each of the developing stations 2Y to 2K, and supplies toner to each of the developing stations 2Y to 2K.

  Reference numeral 18 denotes a paper feed roller, which rotates in a direction D1 by controlling an electromagnetic clutch (not shown), and feeds the recording paper 3 loaded in the paper feeding tray 4 to the recording paper transport path 5.

  A registration paper 19 and a pinch roller 20 pair are provided as a nip conveyance means on the inlet side in the recording paper conveyance path 5 positioned between the paper supply roller 18 and the transfer portion of the most upstream yellow developing station 2Y. The registration roller 19 and the pinch roller 20 pair temporarily stop the recording paper 3 conveyed by the paper supply roller 18 and convey it in the direction of the yellow developing station 2Y at a predetermined timing. This temporary stop restricts the leading edge of the recording paper 3 in parallel with the axial direction of the registration roller 19 and pinch roller 20 pair, thereby preventing the recording paper 3 from skewing.

  Reference numeral 21 denotes a recording paper passage detection sensor. The recording paper passage detection sensor 21 is constituted by a reflective sensor (photo reflector), and detects the leading edge and the trailing edge of the recording paper 3 based on the presence or absence of reflected light.

  When the power transmission is controlled by an electromagnetic clutch (not shown) and the rotation of the registration roller 19 is started, the recording paper 3 is conveyed in the direction of the yellow developing station 2Y along the recording paper conveyance path 5, but the rotation of the registration roller 19 is started. Starting from the timing, the electrostatic latent image writing timing by the exposure devices 13Y to 13K arranged in the vicinity of the developing stations 2Y to 2K, development bias ON / OFF, transfer bias ON / OFF, etc. Be controlled.

  Hereinafter, the description will be continued with reference to FIG.

  Since the distance from the exposure device 13 shown in FIG. 2 to the development region (near the portion where the distance between the photoconductor 8 and the development sleeve 10 is the narrowest) is a design matter, for example, exposure by the exposure device 13 is started and the photoconductor 8 is started. The time for the latent image formed above to reach the development area is also a design matter.

  In the present embodiment, starting from the rotation start timing of the registration roller 19, as described later, when printing a plurality of pages continuously, between the recording paper and the recording paper conveyed through the recording paper conveyance path 5 (that is, In between the sheets), the light quantity of the organic electroluminescence elements constituting the exposure device 13 is set and turned on, and the developing bias is controlled to be turned off with respect to the latent image position formed on the photosensitive member 8. Yes.

  Hereinafter, returning to FIG.

  A fixing unit 23 is provided as a nip conveying means on the exit side in the recording paper conveying path 5 located further downstream of the black developing station 2K at the most downstream side. The fixing device 23 includes a heating roller 24 and a pressure roller 25.

  Reference numeral 27 denotes a temperature sensor for detecting the temperature of the heating roller 24. The temperature sensor 27 is a ceramic semiconductor obtained by sintering at a high temperature using a metal oxide as a main raw material, and can measure the temperature of a contacted object by applying a change in load resistance depending on the temperature. it can. The output of the temperature sensor 27 is input to an engine control unit 42 which will be described later, and the engine control unit 42 controls the power supplied to a heat source (not shown) built in the heating roller 24 based on the output of the temperature sensor 27, The surface temperature of the heating roller 24 is controlled to be about 170 ° C.

  When the recording paper 3 on which the toner image is formed is passed through the nip portion formed by the heating roller 24 and the pressure roller 25 that have been controlled in temperature, the toner image on the recording paper 3 is added to the heating roller 24. The toner image is fixed on the recording paper 3 by being heated and pressurized by the pressure roller 25.

  Reference numeral 28 denotes a recording paper trailing edge detection sensor that monitors the discharge state of the recording paper 3. Reference numeral 32 denotes a toner image detection sensor. The toner image detection sensor 32 is a reflective sensor unit that uses a plurality of light emitting elements (both visible light) having different emission spectra and a single light receiving element, and changes the image color between the background of the recording paper 3 and the image forming portion. Accordingly, the image density is detected by utilizing the fact that the absorption spectrum is different. Further, since the toner image detection sensor 32 can detect not only the image density but also the image forming position, in the image forming apparatus 1 in the embodiment, two toner image detection sensors 32 are provided in the width direction of the image forming apparatus 1, and the recording paper 3 is provided. The image formation timing is controlled based on the detection position of the image positional deviation amount detection pattern formed in the above.

  Reference numeral 33 denotes a recording paper transport drum. The recording paper transport drum 33 is a metal roller whose surface is covered with rubber having a thickness of about 200 μm, and the fixed recording paper 3 is transported along the recording paper transport drum 33 in the direction D2. At this time, the recording sheet 3 is cooled by the recording sheet conveying drum 33 and is bent and conveyed in the direction opposite to the image forming surface. As a result, curling that occurs when a high density image is formed on the entire surface of the recording paper can be greatly reduced. Thereafter, the recording paper 3 is conveyed in the direction D6 by the kicking roller 35 and discharged to the paper discharge tray 39.

  Reference numeral 34 denotes a face-down paper discharge unit. The face-down paper discharge unit 34 is configured to be rotatable about the support member 36. When the face-down paper discharge unit 34 is opened, the recording paper 3 is discharged in the direction D7. In the closed state, the face-down paper discharge unit 34 is formed with ribs 37 along the conveyance path on the back so as to guide the conveyance of the recording sheet 3 together with the recording sheet conveyance drum 33.

  Reference numeral 38 denotes a driving source, which employs a stepping motor in this embodiment. A peripheral portion of each developing station 2Y to 2K including a paper feed roller 18, a registration roller 19, a pinch roller 20, photoconductors 8Y to 8K, and a transfer roller 16 (see FIG. 2), a fixing device 23, and a recording paper. The conveying drum 33 and the kicking roller 35 are driven.

  A controller 41 receives image data from a computer (not shown) via an external network, and develops and generates printable image data. As will be described in detail later, a controller CPU (not shown) mounted on the controller 41 receives light amount measurement data of an organic electroluminescence element as a light emitting element from the exposure devices 13Y to 13K and generates light amount correction data. In addition to the light amount correction means, it is also a light amount setting means for setting the light amount of the organic electroluminescence element based on the light amount correction data.

  Reference numeral 42 denotes an engine control unit. The engine control unit 42 controls the hardware and mechanism of the image forming apparatus 1, forms a color image on the recording paper 3 based on the image data and the light amount correction data transferred from the controller 41, and the fixing unit 23 described above. The overall control of the image forming apparatus 1 including the temperature control of the heating roller 24 is performed.

  Reference numeral 43 denotes a power supply unit. The power supply unit 43 supplies power of a predetermined voltage to the exposure devices 13Y to 13K, the drive source 38, the controller 41, and the engine control unit 42, and supplies power to the heating roller 24 of the fixing unit 23. The power supply unit also includes a so-called high-voltage power supply system such as a charging potential for charging the surface of the photoconductor 8, a developing bias applied to the developing sleeve (see FIG. 2), and a transfer bias applied to the transfer roller 16. . The engine control unit 42 controls the power supply unit 43 to adjust not only the ON / OFF of the high-voltage power supply but also the output voltage value and the output current value.

  The power supply unit 43 includes a power supply monitoring unit 44 so that at least the power supply voltage supplied to the engine control unit 42 and the output voltage of the power supply unit 43 can be monitored. This monitor signal is detected by the engine control unit 42 to detect a drop in power supply voltage that occurs when the power switch is turned off or a power failure occurs, and particularly an output abnormality of the high-voltage power supply.

  The operation of the image forming apparatus 1 configured as described above will be described with reference to FIGS.

  In the following description, FIG. 1 is mainly used for the description relating to the overall configuration and operation of the image forming apparatus 1, and the colors are divided into the developing stations 2Y to 2K, the photoconductors 8Y to 8K, and the exposure devices 13Y to 13K. Although described separately, the description relating to a single color, such as exposure and development processes, will be mainly described with reference to FIG. 2, and for the sake of simplicity, description will be made without distinguishing colors such as the developing station 2, the photoconductor 8, and the exposure device 13.

<Initialization operation>
First, an initialization operation when the image forming apparatus 1 is turned on will be described.

  When the power is turned on, an engine control CPU (not shown) mounted in the engine control unit 42 performs an error check on the electrical resources constituting the image forming apparatus 1, that is, a register / memory capable of writing / reading. To do. When this error check is completed, the engine control CPU (not shown) starts to rotate the drive source 38. As described above, the peripheral portion of each developing station 2Y to 2K including the paper feed roller 18, the registration roller 19, the pinch roller 20, the photoconductors 8Y to 8K, and the transfer roller 16 by the driving source 38, the fixing device 23, and the recording paper conveyance The drum 33 and the kicking roller 35 are driven. However, immediately after the power is turned on, the feeding roller 18 and the registration roller 19 involved in the conveyance of the recording paper 3 are immediately turned off by the electromagnetic clutch (not shown) for transmitting the driving force to the recording roller 3 and the recording paper 3 is conveyed. There is no control.

  Hereinafter, the description will be continued with reference to FIG.

  As the driving source 38 (see FIG. 1) rotates, the stirring paddles 7a and 7b and the developing sleeve 10 of the developing station 2 also start to rotate, whereby the developer 6 composed of toner and carrier filled in the developing station 2 is developed. While rotating around the station 2, the toner is given a negative charge by the friction between the toner and the carrier.

  The engine control CPU (not shown) starts the rotation of the drive source 38 (see FIG. 1) and controls the power supply unit 43 (see FIG. 1) to turn on the charger 9 after a predetermined time has elapsed. The surface of the photoconductor 8 is charged to a potential of, for example, −650 V by the charger 9. The photosensitive member 8 is rotated in the direction D3, and the engine control CPU (not shown) determines the power supply unit 43 (FIG. 1) after the charged region reaches the developing region, that is, the closest position between the photosensitive member 8 and the developing sleeve 10. For example, a developing bias of −250 V is applied to the developing sleeve 10. At this time, the surface potential of the photosensitive member 8 is −650 V, and the developing bias applied to the developing sleeve 10 is −250 V. Therefore, the lines of electric force are directed from the developing sleeve 10 to the photosensitive member 8 and have a negative charge. The Coulomb force acting on the toner is in the direction from the photoconductor 8 to the developing sleeve 10. Therefore, the toner does not adhere to the photoreceptor 8.

  As described above, the power supply unit 43 (see FIG. 1) has a function of monitoring an output abnormality (for example, leakage) of the high-voltage power supply, and an engine control CPU (not shown) is connected to the charger 9 and the developing sleeve 10 with high power. It is possible to check for abnormalities when a voltage is applied.

  The engine control CPU 91 (see FIG. 7) executes light amount correction of the exposure device 13 at the end of the series of initialization operations or at another predetermined timing as will be described later. The engine control CPU 91 mounted on the engine control unit 42 (see FIG. 1) outputs a request to create dummy image information for light amount correction to the controller 41 (see FIG. 1). Based on this creation request, the controller 41 (see FIG. 1) generates dummy image information for light amount correction, and based on this, the organic electroluminescence elements constituting the exposure apparatus 13 are actually controlled to be turned on at the time of initialization. .

  As will be described in detail later, the image forming apparatus 1 according to the present invention includes an exposure device 13 provided with a light emitting element array in which a plurality of light emitting elements (organic electroluminescence elements) are formed in a row. Is an image forming apparatus that performs image formation by exposing the photosensitive member 8 that is an image carrier, and a light amount setting unit that sets a light amount of a light emitting element (organic electroluminescence element) (a controller mounted on the controller 41 described above) CPU) and light quantity measuring means (a light quantity sensor provided in the above-described exposure apparatus 13) for measuring the light quantity of the light emitting element (organic electroluminescence element).

  Further, the image forming apparatus 1 according to the present invention includes an exposure device 13 provided with a light emitting element array in which a plurality of light emitting elements (organic electroluminescence elements) are formed in a row, and a photoconductor on which a latent image is formed by the exposure device 13. 8 and a developing means (developing sleeve 10 constituting the developing station 2) for developing and developing the latent image formed on the photoconductor 8, as will be described in detail later. Light quantity setting means (controller CPU mounted on the controller 41) for setting the light quantity of the light emitting element (organic electroluminescence element), and light quantity measuring means (the exposure apparatus 13 described above) for measuring the light quantity of the light emitting element (organic electroluminescence element). A light quantity sensor).

  At a predetermined timing as will be described later, an organic electroluminescence element as an exposure light source constituting the exposure apparatus 13 emits light, and this light amount is measured, so that the photosensitive member 8 can be corrected even if the light amount and thus the exposure amount on the photosensitive member is corrected. Therefore, the toner does not adhere and the toner is not wasted. Further, toner adheres to the transfer roller 16 that rotates in contact with the photosensitive member 8, and in image formation performed following the initialization operation, the toner attached to the transfer roller 16 adheres to the back surface of the recording paper 3 and the recording paper 3. No pollution.

  In this light amount correction, the region where the photoconductor 8 is exposed by turning on the organic electroluminescent element is close to the developing sleeve 10 and passes through the so-called developing region, that is, in the measurement period for measuring the light amount of the organic electroluminescent element. It is desirable to turn off the developing bias applied to the developing sleeve 10 for the exposed region of the photosensitive member 8. This makes it possible to more effectively prevent the toner from adhering to the photoreceptor 8.

<Image forming operation>
Next, the operation of the image forming apparatus 1 during image formation will be described with reference to FIG. 1 and FIG.

  When the image information is transferred from the outside to the controller 41, the controller 41 develops the image information in an image memory (not shown) as binary image data that can be printed. When the development of the image information is completed, a controller CPU (not shown) mounted on the controller 41 issues a startup request to the engine control unit 42. The activation request is received by an engine control CPU (not shown) mounted on the engine control unit 42, and the engine control CPU (not shown) receiving the activation request immediately rotates the drive source 38 to prepare for image formation. To start.

  When the preparation for image formation is completed through the above-described process, an engine control CPU (not shown) mounted on the engine control unit 42 controls an electromagnetic clutch (not shown) to rotate the paper feed roller 18 to perform recording. The conveyance of the paper 3 is started. The paper supply roller 18 is, for example, a half-moon roller that lacks a part of the entire circumference. The paper supply roller 18 conveys the recording paper 3 in the direction of the registration roller 19 and stops rotating when it rotates once. When the leading edge of the conveyed recording paper 3 is detected by the recording paper passing sensor 21, an engine control CPU (not shown) controls an electromagnetic clutch (not shown) after providing a predetermined delay period to register rollers. 19 is rotated. As the registration roller rotates, the recording paper 3 is supplied to the recording paper conveyance path 5.

  An engine control CPU (not shown) independently controls the electrostatic latent image writing timing by each of the exposure devices 13Y to 13K, starting from the rotation start timing of the registration roller 19. Since the electrostatic latent image writing timing directly affects color misregistration and the like in the image forming apparatus 1, the writing timing is not directly generated by an engine control CPU (not shown). Specifically, an engine control CPU (not shown) presets the electrostatic latent image writing timing by each exposure device 13 in a timer (not shown) such as hardware, and rotates the registration roller 19 described above. As a starting point, timer operations corresponding to the exposure apparatuses 13Y to 13K are simultaneously started. Each timer outputs an image data transfer request to the controller 41 when a preset time has elapsed.

  The controller CPU (not shown) of the controller 41 that has received the image data transfer request is synchronized with the timing signal (clock signal, line synchronization signal, etc.) generated by the timing generation unit (not shown) of the controller 41. The value image data is transferred independently to each of the exposure devices 13Y to 13K. In this way, binary image data is sent to the exposure devices 13Y to 13K, and on / off of the organic electroluminescence elements constituting the exposure devices 13Y to 13K is controlled based on the binary image data, and a photoconductor corresponding to each color. 8Y to 8K are exposed.

  The latent image formed by the exposure is visualized by toner contained in the developer 6 supplied onto the developing sleeve 10 as shown in FIG. The visualized toner images of the respective colors are sequentially transferred to the recording paper 3 conveyed through the recording paper conveyance path 5. The recording paper 3 on which the transfer of the four color toner images has been completed is conveyed to the fixing device 23, and is nipped and conveyed by the overheating roller 24 and the pressure roller 25 constituting the fixing device 23. The toner image is recorded on the recording paper by this heat and pressure. 3 is fixed.

  When the image to be formed is a plurality of pages, the engine control CPU (not shown) detects the trailing edge of the recording paper 3 of the first page by the recording paper passage detection sensor 21 and then temporarily rotates the registration roller 19. Then, after a predetermined time has elapsed, the paper feed roller 18 is rotated to start the conveyance of the next recording paper 3, and after the predetermined time has elapsed, the registration roller 19 is again rotated to start the recording paper 3 of the next page. Is supplied to the recording paper conveyance path 5. Thus, by controlling the rotation ON / OFF timing of the registration roller 19, it is possible to set the sheet interval between the recording sheets 3 when an image is formed over a plurality of pages. The time between the sheets (hereinafter referred to as the sheet interval) varies depending on the specifications of the image forming apparatus 1, but is generally set to about 500 ms. Of course, the normal image forming operation (that is, the exposure operation for the photosensitive member 8 by the exposure device 13) is not performed during the period between the sheets.

  FIG. 3 is a block diagram of the exposure device 13 in the image forming apparatus 1 according to the embodiment of the present invention. Hereinafter, the structure of the exposure apparatus 13 will be described in detail with reference to FIG. In FIG. 3, 50 is a colorless and transparent glass substrate. In the present embodiment, cost-effective borosilicate glass is used as the glass substrate 50. However, heat generation from a light emitting element or a control circuit or a drive circuit formed by a thin film transistor on the glass substrate 50 is more efficiently radiated. If necessary, glass containing a thermal conductivity additive factor such as MgO, Al2O3, CaO, ZnO, or quartz may be used.

  On the surface A of the glass substrate 50, an organic electroluminescence element as a light emitting element is formed with a resolution of 600 dpi (dot / inch) in a direction perpendicular to the drawing (main scanning direction). Reference numeral 51 denotes a lens array in which rod lenses (not shown) made of plastic or glass are arranged in a line, and the light emitted from the organic electroluminescence element formed on the surface A of the glass substrate 50 is erecting at an equal magnification. The image is guided to the surface of the photoreceptor 8 as an image. The positional relationship among the glass substrate 50, the lens array 51, and the photoconductor 8 is adjusted so that one focal point of the lens array 51 is the surface A of the glass substrate 50 and the other focal point is the surface of the photoconductor 8. . That is, when the distance L1 from the surface A to the surface closer to the lens array 51 and the distance L2 from the other surface of the lens array 51 to the surface of the photosensitive member 8, L1 = L2.

  For example, 52 is a relay substrate in which an electronic circuit is formed on a glass epoxy substrate. 53a is a connector A, 53b is a connector B, and at least a connector A 53a and a connector B 53b are mounted on the relay board 52. The relay board 52 temporarily relays image data, light quantity correction data, and other control signals supplied from the outside to the exposure apparatus 13 through a cable 56 such as a flexible flat cable, etc., via a connector B 53b, and these signals are made of glass. Passed to the substrate 50.

  Since it is difficult to directly mount the connector on the surface of the glass substrate 50 in consideration of bonding strength and reliability in various environments, in this embodiment, as a connection means between the connector A 53a of the relay substrate 52 and the glass substrate 50. An FPC (Flexible Printed Circuit) is employed (not shown), and the glass substrate 50 and the FPC are bonded on the glass substrate 50 in advance using, for example, an ACF (Anisotropic Conductive Film). For example, it is configured to be directly connected to the formed ITO (Indium Tin Oxide) electrode.

  On the other hand, the connector B 53b is a connector for connecting the exposure apparatus 13 to the outside. In general, connection by ACF or the like often has a problem of bonding strength, but by providing the connector B 53b for the user to connect the exposure apparatus 13 on the relay substrate 52 in this way, an interface directly accessed by the user. Sufficient strength can be secured.

  Reference numeral 54a denotes a casing A which is formed by bending a metal plate, for example. An L-shaped portion 55 is formed on the side of the housing A 54 a facing the photoconductor 8, and the glass substrate 50 and the lens array 51 are disposed along the L-shaped portion 55. The end surface of the case A 54a on the side of the photoconductor 8 and the end surface of the lens array 51 are aligned with each other, and the end portion of the glass substrate 50 is supported by the case A 54a. If the molding accuracy is ensured, the positional relationship between the glass substrate 50 and the lens array 51 can be adjusted with high accuracy. As described above, since the casing A 54a is required to have dimensional accuracy, it is preferable that the casing A 54a be made of metal. Further, by making the casing A 54a made of metal, it is possible to suppress the influence of noise on electronic components such as a control circuit formed on the glass substrate 50 and an IC chip surface-mounted on the glass substrate 50. It is.

  A housing B is obtained by molding a resin. A notch (not shown) is provided in the vicinity of the connector B 53b of the housing B 54b, and the user can access the connector B 53b from this notch. From the controller 41 (see FIG. 1) already described via the cable 56 connected to the connector B 53b, the image data, the light amount correction data, the control signal such as the clock signal and the line synchronization signal, and the drive power for the control circuit are transferred to the exposure apparatus 13. A driving power source for the organic electroluminescence element which is a light emitting element is supplied.

  4A is a top view of the glass substrate 50 related to the exposure apparatus 13 in the image forming apparatus 1 according to the embodiment of the present invention, and FIG. 4B is an enlarged view of the main part thereof. Hereinafter, the configuration of the glass substrate 50 in the embodiment will be described in detail with reference to FIG.

  In FIG. 4, a glass substrate 50 is a rectangular substrate having a thickness of about 0.7 mm and at least a long side and a short side, and a plurality of organic electroluminescences that are light emitting elements in the long side direction (main scanning direction). Elements 63 are formed in a row. In the embodiment, the organic electroluminescence element 63 necessary for at least A4 size (210 mm) exposure is arranged in the long side direction of the glass substrate 50, and the long side direction of the glass substrate 50 has an arrangement space for the drive control unit 58 described later. Including 250 mm. In the embodiment, the glass substrate 50 is described as a rectangle for the sake of simplicity. However, a notch is provided in a part of the glass substrate 50 for positioning when the glass substrate 50 is attached to the housing A 54a. It may be accompanied by deformation.

  A drive 58 receives binary image data, light amount correction data, and control signals such as a clock signal and a line synchronization signal supplied from the outside of the glass substrate 50, and controls driving of the organic electroluminescence element 63 based on these signals. The control unit includes an interface unit that receives these signals from the outside of the glass substrate 50 and an IC chip (source driver 61) that controls the driving of the organic electroluminescence element 63 based on the control signal received through the interface unit. Yes.

  Reference numeral 60 denotes an FPC (flexible printed circuit) as an interface means for connecting the connector A 53a of the relay substrate 52 and the glass substrate 50, and is directly connected to a circuit pattern (not shown) provided on the glass substrate 50 without using a connector or the like. ing. As already described, binary image data, light amount correction data and control signals such as clock signals and line synchronization signals supplied to the exposure apparatus 13 from the outside, a driving power source for the control circuit, and the organic electroluminescence element 63 as a light emitting element. Is supplied to the glass substrate 50 via the FPC 60 after passing through the relay substrate 52 shown in FIG.

  Reference numeral 63 denotes an organic electroluminescence element, which is an exposure light source in the exposure apparatus 13. In the embodiment, 5120 organic electroluminescence elements 63 are formed in a row at a resolution of 600 dpi in the main scanning direction, and each organic electroluminescence element 63 is independently controlled to be turned on / off by a TFT circuit described later. The

  A source driver 61 is supplied as an IC chip for controlling the driving of the organic electroluminescence element 63 and is flip-chip mounted on the glass substrate 50. Considering the surface mounting on the glass surface, the source driver 61 adopts a bare chip product. The source driver 61 is supplied with control-related signals such as a power supply, a clock signal, and a line synchronization signal and 8-bit light amount correction data from the outside of the exposure apparatus 13 via the FPC 60. The source driver 61 is a drive current setting unit for the organic electroluminescence element 63. More specifically, it is based on light amount correction data generated by a controller CPU (not shown) mounted on the controller 41 (see FIG. 1), which is a light amount correction unit and a light amount setting unit of the organic electroluminescence element 63. The source driver 61 sets a drive current for driving each organic electroluminescence element 63. The operation of the source driver 61 based on the light amount correction data will be described in detail later.

  In the glass substrate 50, the joint portion of the FPC 60 and the source driver 61 are connected, for example, via an ITO circuit pattern (not shown) having a metal formed on the surface, and the FPC 60 is connected to the source driver 61 as drive current setting means. Control signals such as light quantity correction data, a clock signal, and a line synchronization signal are input via the control signal. Thus, the FPC 60 as the interface means and the source driver 61 as the drive parameter setting means constitute the drive control unit 58.

  Reference numeral 62 denotes a TFT (Thin Film Transistor) circuit formed on the glass substrate 50. The TFT circuit 62 includes a shift register, a data latch unit, and the like, a gate controller (not shown) that controls the timing of turning on / off the organic electroluminescence element 63, and a drive circuit that supplies a drive current to each organic electroluminescence element 63 (Not shown, hereinafter referred to as a pixel circuit), and further includes a switching circuit (selection signal generation circuit 140) for turning on / off a light amount sensor 57 described later. One pixel circuit is provided for each organic electroluminescence element 63, and is provided in parallel with the light emitting element row formed by the organic electroluminescence element 63. A drive current value for driving each organic electroluminescence element 63 is set in this pixel circuit by a source driver 61 which is a drive parameter setting means.

  A gate controller (not shown) constituting the TFT circuit 62 is supplied with a control signal such as a power supply, a clock signal, and a line synchronization signal and binary image data from the outside of the exposure apparatus 13 via the FPC 60, and the gate controller (FIG. (Not shown) controls the lighting / extinguishing timing of each light emitting element based on these power sources and signals. The operations of the gate controller and the pixel circuit (both not shown) will be described in detail later with reference to the drawings. The configuration of the TFT circuit 62 on the sensor side will be described in detail later.

  Reference numeral 64 denotes sealing glass. When the organic electroluminescence element 63 is affected by moisture, the light emission characteristics are extremely deteriorated due to shrinkage of the light emitting region over time (shrinking) and non-light emitting portions (dark spots) in the light emitting region. Sealing is necessary to block moisture. In the embodiment, a solid sealing method in which the sealing glass 64 is attached to the glass substrate 50 via an adhesive is employed. However, the sealing region is generally from the light emitting element array formed by the organic electroluminescence element 63 in the sub-scanning direction. About 2000 μm is required, and in the embodiment, 2000 μm is secured as a sealing margin.

  57 is a light quantity sensor formed on the upper surface of the organic electroluminescence element 63 (in FIG. 4B). The light quantity sensor 57 measures the light quantity of each organic electroluminescence element 63. In principle, it is necessary to measure the amount of light by individually lighting the organic electroluminescence elements 63 one by one, but the light amount sensor sufficiently separated from the organic electroluminescence element 63 to be measured is used. In this embodiment, the light quantity sensor 57 is composed of a plurality of light quantity sensors because the light emission is hardly affected (the emitted light from the organic electroluminescence element 63 is attenuated). It is possible to measure the amount of light simultaneously.

  In the present embodiment, the organic electroluminescence element 63, the TFT circuit 62, and the light quantity sensor 57 are integrated and formed as a monolithic device of polysilicon. That is, since the light transmittance of the low-temperature polysilicon constituting the TFT circuit 62 is relatively high, even in a so-called bottom emission configuration in which exposure light is extracted from the glass substrate 50 side, the light amount corresponding to each organic electroluminescence element 63 is obtained. The sensor 57 can be embedded adjacent to the TFT circuit 62. The light quantity sensor in this case is formed on the entire surface immediately below the light emitting surface of each organic electroluminescence element 63, but may be formed corresponding to a part thereof.

  The outputs of the plurality of light quantity sensors 57 are input to the source driver 61 described above through wiring not shown. The output of the light quantity sensor (light quantity sensor output), which will be described later, is subjected to voltage conversion by the charge accumulation method in the source driver 61, further amplified by a predetermined amplification factor, then analog-to-digital conversion, and digital data after this digital conversion (Hereinafter referred to as light quantity measurement data) is output to the outside of the exposure apparatus 33 via the FPC 60, the relay substrate 52, and the cable 56 (both see FIG. 3). As will be described in detail later, the light quantity measurement data is received and processed by a controller CPU (not shown) mounted on the controller 41 (see FIG. 1) to generate 8-bit light quantity correction data.

  FIG. 5 is a block diagram showing the configuration of the controller 41 in the image forming apparatus 1 according to the embodiment of the present invention. Hereinafter, the operation of the controller 41 will be described with reference to FIG. 5, and the light amount correction will be described in more detail.

  In FIG. 5, reference numeral 80 denotes a computer. The computer 80 is connected to a network 81, and transfers image information, the number of prints, and print job information such as a print mode (for example, color / monochrome) to the controller 41 via the network 81. 82 is a network interface. The controller 41 receives the image information and print job information transferred from the computer 80 via the network interface 82, develops the image information into printable binary image data, and conversely detected by the image forming apparatus side. Error information or the like is transmitted as so-called status information to the computer 80 via the network 81.

  A controller CPU 83 controls the operation of the controller 80 based on a program stored in the ROM 84. A RAM 85 is used as a work area for the controller CPU 83, and temporarily stores image information, print job information, and the like received via the network interface 82.

  Reference numeral 86 denotes an image processing unit. The image processing unit 86 can perform printing by performing image processing (for example, image development processing based on printer language, color correction, edge correction, screen generation, etc.) on a page basis based on image information and print job information transferred from the computer 80. Binary image data is generated and stored in the image memory 65 in units of pages.

  Reference numeral 66 denotes a light amount correction data memory constituted by a rewritable nonvolatile memory such as an EEPROM.

  FIG. 6 is an explanatory diagram showing the contents of the light amount correction data memory in the image forming apparatus 1 according to the embodiment of the present invention.

  Hereinafter, the data structure and data contents in the light amount correction data memory will be described with reference to FIG.

  As shown in FIG. 6, the light quantity correction data memory 66 has three areas from a first area to a third area. Each area includes 5120 8-bit data equal to the number of organic electroluminescence elements 63 (see FIG. 4) constituting the exposure apparatus 13 (see FIG. 3), and occupies a total of 15360 bytes.

  First, data DD [0] to DD [5119] stored in the first area will be described with reference to FIGS. 3 and 4 in FIG.

  The already-explained exposure apparatus 13 (see FIG. 3) includes a step of adjusting the light quantity of each organic electroluminescence element 63 (see FIG. 4) constituting the exposure apparatus 13 in the manufacturing process. In this step, the exposure apparatus 13 is attached to a predetermined jig (not shown), and the organic electroluminescence element 63 is individually controlled to be turned on based on a control signal supplied from the outside of the exposure apparatus 13.

  Further, a CCD camera provided on a jig (not shown) measures the two-dimensional exposure amount distribution of each organic electroluminescence element 63 at the image plane position of the photoreceptor 8 (see FIG. 3). A jig (not shown) calculates the potential distribution of the latent image formed on the photoconductor 8 based on the exposure amount distribution, and further correlates with the toner adhesion amount based on the actual development condition (development bias value). Calculate the latent image cross section. In a jig (not shown), the driving current value for driving the organic electroluminescence element 63 is changed {as described above, the TFT circuit 62 (see FIG. 4) is connected via the source driver 61 (see FIG. 4). A current value for driving the organic electroluminescence element 63 can be set by programming an analog value in the pixel circuit to be configured. } A driving current value at which all of the latent image cross-sectional areas formed by the individual organic electroluminescence elements 63 become substantially equal, that is, a setting value for the pixel circuit (setting data for the source driver 61 from the viewpoint of control) To extract.

  Now, assuming that the light emission area of the organic electroluminescence element 63 and the light emission quantity distribution in the light emission surface are equal and normal development conditions are assumed, the above-described latent image cross-sectional area is substantially proportional to the exposure amount. Furthermore, “(light emission) light amount when the exposure time is constant” and “exposure amount” are synonymous, and generally, the light emission light amount and driving current value of the organic electroluminescence element 63 (that is, a set value for the pixel circuit). Since the drive current setting for all pixel circuits is the same, the light emission quantity of each organic electroluminescence element 63 is measured once, and the latent image cross-sectional area of each organic electroluminescence element 63 is constant. It is also possible to obtain a setting value for the pixel circuit to be set (setting data for the source driver 61 as described above) by calculation.

  In the first area of the light quantity correction data memory 66, the setting data for the source driver 61 obtained in this way is stored. The number thereof is 5120 equal to the number of organic electroluminescence elements 63 constituting the exposure apparatus 13 as described above (that is, equal to the number of pixel circuits). As described above, the first area of the light quantity correction data memory 66 stores “the set value of the source driver 61 for equalizing the cross-sectional areas of the latent images formed by the individual organic electroluminescence elements 63 in the initial state”. .

  Next, data ID [0] to ID [5119] stored in the second area will be described with reference to FIGS.

  At the same time that the jig acquires the data stored in the first area, the jig obtains 8-bit light quantity measurement data based on the output of the light quantity sensor 57 (see FIG. 4) via the source driver 61 (see FIG. 4) of the exposure apparatus 13. get. As a result, “light quantity measurement data when the cross-sectional areas of the latent images formed by the individual organic electroluminescence elements 63 in the initial state are equal” can be acquired. The 8-bit light quantity measurement data ID [n] is stored in the second area.

  Now, the driving condition of the organic electroluminescence element 63 when acquiring ID [n] by the jig needs to be the same as that at the time of measuring the light amount. In the embodiment, as will be described later, one line period of the image forming apparatus 1 is used. A 350 μs (raster period) is applied a plurality of times to give a lighting period of about 30 ms in total.

  In this way, data stored in the first area and the second area in the manufacturing process of the exposure apparatus 13 is acquired, and these data are written from the jig to the light amount correction data memory 66 by electrical communication means (not shown). .

  Next, data ND [0] to ND [5119] stored in the third area will be described with reference to FIG. 6, FIG. 4, and FIG.

  The image forming apparatus 1 according to the embodiment of the present invention includes a light amount correction unit (light amount correction unit) that corrects each light amount of the organic electroluminescence element 63 substantially equally based on a measurement result by the light amount sensor 57 serving as a light amount measurement unit. Controller CPU 83 (see FIG. 5)}, and based on the output of the light quantity correction means, the light quantity setting means (also the controller CPU 83) sets the light quantity of each organic electroluminescence element 63 at the time of image formation. In the third area, a light amount setting value of each organic electroluminescence element 63 when image formation is performed by the controller CPU 83 as light amount correction means, that is, light amount correction data is written.

  In the image forming apparatus 1 according to the embodiment, the exposure apparatus 13 is configured at a predetermined timing, which will be described later, such as when the image forming apparatus 1 is initialized, when the image forming operation is started, between sheets, when the image forming operation is completed. As described above, the amount of light of the organic electroluminescence element 63 to be measured is measured. The controller CPU 83 makes the light quantity measurement data measured at these times equal to the “latent image sectional areas formed by the individual organic electroluminescence elements 63 in the initial state” stored in the first area in the manufacturing process of the exposure apparatus 13. The setting value of the source driver 61 for performing the process is the same as the “cross-sectional area of the latent image formed by each organic electroluminescence element 63 in the initial state” stored in the second area in the manufacturing process of the exposure apparatus 13. Light quantity correction data is generated based on the "light quantity measurement data". That is, the controller CPU 83 functions as a light amount correction unit that refers to the light amount of the organic electroluminescence element 63 detected by the light amount sensor 57 and corrects the light amount of the element.

  Hereinafter, the calculation content of the light amount correction data by the controller CPU 83 will be described, but in order to clarify the point of the present invention, the light amount at the time of light amount measurement is first assumed to be equal to that at the time of image formation.

  DD [n] (n is the value in the main scanning direction) stored in the first area is “the set value of the source driver 61 for equalizing the cross-sectional areas of the latent images formed by the individual organic electroluminescence elements 63 in the initial state”. Individual organic electroluminescence element numbers (hereinafter the same), “light quantity measurement data when the latent image cross-sectional areas formed by the individual organic electroluminescence elements 63 in the initial state are equal” stored in the second area is ID [ n], when the light quantity measurement data newly measured in the initialization operation or the like is PD [n], the new light quantity correction data ND [n] written in the third area is based on (Expression 1). Generated by. The light quantity measurement data ID [n] corresponds to the measured light quantity of the organic electroluminescence element, but the light quantity correction data ND [n] is a current value passed through each element set in the source driver 61. Applicable.

  The light quantity correction data ND [n] generated in this way is once written in the third area of the light quantity correction data memory 66 (see FIG. 5). Thereafter, prior to image formation, the light quantity correction data ND [n] is copied from the light quantity correction data memory 66 to a predetermined area of the image memory 65 (see FIG. 5). The light amount correction data ND [n] copied to the image memory 65 when forming an image is temporarily stored together with binary image data in a buffer memory 88 (see FIG. 5), which will be described later, and a printer interface 87 (see FIG. 5). ) To the engine control unit 42 (see FIG. 5).

  The light quantity measurement data is subjected to voltage conversion by the charge accumulation method in the source driver 61. The charge accumulation method is effective for improving the S / N ratio. However, since the output (current value) of the light quantity sensor 57 (see FIG. 4) is very small, a certain accumulation time is required for charge accumulation. This will be described later.

  Hereinafter, the description will be continued returning to FIG.

  Reference numeral 88 denotes a buffer memory. The binary image data stored in the image memory 65 and the light amount correction data described above are temporarily stored in the buffer memory 88 when transferred to the engine control unit 42. The buffer memory 88 is constituted by a so-called dual port RAM in order to absorb the difference between the transfer speed from the image memory 65 to the buffer memory 88 and the data transfer speed from the buffer memory 88 to the engine control unit 42.

  Reference numeral 87 denotes a printer interface. The binary image data and light amount correction data in page units stored in the image memory 65 are transferred to the engine control unit 42 via the printer interface 87 in synchronization with the clock signal and line synchronization signal generated by the timing generation unit 67. The

  FIG. 7 is a block diagram showing the configuration of the engine control unit 42 in the image forming apparatus 1 according to the embodiment of the present invention. Hereinafter, the operation of the engine control unit 42 will be described in detail with reference to FIG.

  In FIG. 7, reference numeral 90 denotes a controller interface. The controller interface 90 receives light amount correction data transferred from the controller 41, binary image data in units of pages, and the like.

  An engine control CPU 91 controls an image forming operation in the image forming apparatus 1 based on a program stored in the ROM 92. A RAM 93 is used as a work area when the engine control CPU 91 operates. 94 is a so-called rewritable nonvolatile memory such as an EEPROM. The nonvolatile memory 94 stores information on the lifetime of the constituent elements such as the rotation time of the photoconductor 8 of the image forming apparatus 1 and the operation time of the fixing device 23 (see FIG. 1).

  Reference numeral 95 denotes a serial interface. Information from sensors such as the recording paper passage detection sensor 21 (see FIG. 1) and the recording paper trailing edge detection sensor 28 (see FIG. 1) and the output of the power supply monitoring unit 44 (see FIG. 1) are not shown in the figure. Is converted into a serial signal having a predetermined cycle and received by the serial interface 95. The serial signal received by the serial interface 95 is converted into a parallel signal and then read by the engine control CPU 91 via the bus 99.

  On the other hand, control for an actuator group 96 such as an electromagnetic clutch (not shown) for controlling the starting and stopping of the paper feed roller 18 and the drive source 38 (both see FIG. 1) and the driving force transmission to the paper feed roller 18 (see FIG. 1). Signals and control signals for the high voltage power supply control unit 97 that manages potential settings such as development bias, transfer bias, and charging potential are sent to the serial interface 95 as parallel signals. The serial interface 95 converts the parallel signal into a serial signal and outputs it to the actuator group 96 and the high voltage power supply control unit 97. As described above, in the embodiment, sensor inputs and actuator control signals that do not need to be detected at high speed are all output via the serial interface 95. On the other hand, for example, a control signal for driving / stopping the registration roller 19 that requires a certain high speed is directly connected to the output terminal of the engine control CPU 42.

  An operation panel 98 is connected to the serial interface 95. The instruction given to the operation panel 98 by the user is recognized by the engine control CPU 91 via the serial interface 95. In the embodiment, an operation panel is provided as an instruction input means for inputting a user instruction. Based on the input to the operation panel, the light quantity of the organic electroluminescence element 63 constituting the exposure apparatus 13 is measured, and the light quantity May be corrected. This instruction can of course be given from an external computer or the like via the controller 41. As a specific usage mode, for example, when the user discovers density unevenness on the printing surface when performing a large amount of printing, the user forcibly corrects the amount of light to ensure image quality. Is assumed. If the image forming apparatus 1 is on standby, the user can instruct the execution of forced light amount correction at any time, and even during image formation, the image forming apparatus 1 is shifted to offline to temporarily form an image. Thus, the user can instruct execution of light amount correction.

  In any case, when a light quantity correction request is input from the operation panel 98 or the like as an instruction unit, the engine control CPU 91 starts driving the components of the image forming apparatus 1 as described in <Initialization Operation>. , A request to create dummy image information for light amount correction is output to the controller 41. Based on this request, the controller CPU 83 mounted on the controller 41 generates dummy image information for light amount correction, and the organic electroluminescence element 63 constituting the exposure apparatus 13 is controlled to be lit based on this. At this time, the light quantity sensor 57 provided in the exposure apparatus 13 described above detects the light quantity of each organic electroluminescence element 63, and the light quantity of each organic electroluminescence element 63 is substantially equal based on the detection result of this light quantity. The amount of light is corrected so that

  Next, the operation when measuring the amount of light of the organic electroluminescence element 63 will be described in detail with reference to FIGS. 1, 5 and 6 in FIG.

  As will be described later, the correction of the amount of light is performed at the timing specified by the user using the operation panel 98 or the like after the initialization operation immediately after the image forming apparatus 1 is started up, before starting printing, between sheets, after starting printing. Next, a case where the light amount measurement is executed at the time of initialization operation of the image forming apparatus 1 will be described. The image forming apparatus 1 according to the embodiment is configured to be capable of forming a full-color image, and has exposure apparatuses 13Y to 13K (see FIG. 1) corresponding to four colors as described above. For the sake of simplicity, only the operation for one color will be described and described as an exposure apparatus 13. In the situation shown below, for example, it is assumed that the drive source 38 (see FIG. 1), the developing station 2 (see FIG. 2), and the like have already been activated as described in detail in <Initialization Operation>.

  Since the image forming operation is managed by the engine control unit 42 in the image forming apparatus 1, the light quantity correction sequence is started by the engine control CPU 91 of the engine control unit 42. First, the engine control CPU 91 outputs to the controller 41 a request for creating dummy image information that is different from the regular binary image data related to image formation.

  The engine control unit 42 and the controller 41 are connected by a bidirectional serial interface (not shown), and can exchange a request command (request) and an acknowledgment (response information) with respect to each other. The dummy image information creation request issued by the engine control CPU 91 is output from the controller interface 90 to the controller 41 via the bus 99 using this bidirectional serial interface (not shown).

  Based on this request, the controller CPU 83 mounted on the controller 41 directly creates dummy image information, that is, binary image data used for light quantity measurement, in the image memory 65. Further, the controller CPU 83 stores “the source driver 61 for equalizing the latent image sectional areas formed by the individual organic electroluminescence elements 63 in the initial state” stored in the first area (see FIG. 6) of the light amount correction data memory 66. “Setting value” DD [n] (n: 0 to 5119) is read, and this value is written in a predetermined area of the image memory 65. When these processes are completed, the controller CPU 83 outputs response information to the engine control unit 42 via the printer interface 87.

  The engine control CPU 91 of the engine control unit 42 that has received the response information immediately sets a write timing for the exposure apparatus 13. That is, the engine control CPU 91 sets the timing for writing the electrostatic latent image by the exposure device 13 to a timer, which is hardware (not shown), and starts the operation of the timer as soon as response information is received (this function is originally provided with a plurality of exposure devices). This is to determine the start timing for each color of 13. Such a strict timing setting is not necessary in the measurement of the light quantity, and for example, 0 may be set in the timer). Each timer outputs an image data transfer request to the controller 41 when a preset time has elapsed. The controller 41 that has received the image data transfer request transfers the binary image data to the exposure device 13 in synchronization with the timing signal (clock signal, line synchronization signal, etc.) generated by the timing generator 67 via the controller interface 90. . At the same time, the light intensity setting value already written in the image memory 65 is also transferred to the exposure apparatus 13 in synchronization with the timing signal.

  The binary image data transferred in synchronization with the timing signal in this manner is input to the TFT circuit 62 of the exposure apparatus 13, and at the same time, the light amount setting value is input to the source driver 61 of the exposure apparatus 13. The exposure device 13 controls the lighting and extinguishing of the corresponding organic electroluminescence element 63 based on the input binary image data, that is, ON / OFF information. At this time, the light quantity of each organic electroluminescence element 63 is measured by the light quantity sensor 57.

  As described above, the lighting of the organic electroluminescence element 63 is controlled, and the light amount is measured by the light amount sensor 57. The output (analog current value) of the light quantity sensor 57 is converted into a voltage by the charge accumulation method in the source driver 61, amplified with a predetermined amplification factor, and then subjected to analog-digital conversion to obtain 8-bit light quantity measurement data (digital data). ) As output from the source driver 61.

  The light quantity measurement data output from the source driver 61 is transferred from the engine control unit 42 to the controller 41 via the controller interface 90 and received by the controller CPU 83 of the controller 41.

  FIG. 8 is a circuit diagram of the exposure device 13 in the image forming apparatus 1 according to the embodiment of the present invention. Hereinafter, the lighting control by the TFT circuit 62 and the source driver 61 will be described in more detail with reference to FIG.

  The TFT circuit 62 is roughly divided into a pixel circuit 69 and a gate controller 68. One pixel circuit 69 is provided for each organic electroluminescence element 63, and N groups are provided on the glass substrate 50 with the M pixels of the organic electroluminescence element 63 as one group.

  In the embodiment, one group is 8 pixels (that is, M = 8), and this group is 640. Therefore, the total number of pixels is 8 × 640 = 5120 pixels. Each pixel circuit 69 supplies a current to the organic electroluminescence element 63 and drives it, and a current value supplied by the driver when controlling the lighting of the organic electroluminescence element 63 (that is, a drive current value of the organic electroluminescence element 63). ) Is stored in a capacitor included therein, and the organic electroluminescence element 63 can be driven at a constant current according to a drive current value programmed in advance at a predetermined timing.

  The gate controller 68 includes a shift register that sequentially shifts input binary image data, a latch unit that is provided in parallel with the shift register and collectively holds the input after a predetermined number of pixels have been input to the shift register, It consists of a control part which controls these operation timings (both not shown). The gate controller 68 is supplied with binary image data (image information converted by the controller 41 at the time of image formation and dummy image information converted by the controller 41 at the time of light quantity measurement) from the controller 41, and this binary image data, that is, ON. The SCAN_A and SCAN_B signals are output based on the / OFF information, and thereby the timing of turning on / off the organic electroluminescence element 63 connected to the pixel circuit 69 and the timing of the current program period for setting the drive current are controlled. .

  On the other hand, the source driver 61 has a number of D / A converters 72 (640 in the embodiment) corresponding to the number N of groups of the organic electroluminescence elements 63 inside. The source driver 61 sets a drive current for each organic electroluminescence element 63 based on the 8-bit light amount correction data supplied via the FPC 60.

  FIG. 9 is an explanatory diagram showing a current program period and a lighting period of the organic electroluminescence element 63 according to the exposure device 13 in the image forming apparatus 1 of the embodiment of the present invention. Hereinafter, the lighting control according to the embodiment will be described in more detail with reference to FIG. In order to simplify the description, one pixel group consisting of 8 pixels (for example, “pixel number in the main scanning direction” = 1 to 8 in FIG. 9) will be described.

  In the embodiment, one line period (raster period) of the exposure apparatus 13 is set to 350 μs, and 1/8 (43.77 μs) of the one line period is set to a drive current for the capacitor formed in the current program unit 71. It is used as the program period for setting the value.

  First, the gate controller 68 (see FIG. 8) sets the program period by turning on the SCAN_A signal and turning off the SCAN_B signal for the pixel of pixel number = 1. During the program period, 8-bit light amount correction data is supplied to the D / A converter 72 built in the source driver 61 (see FIG. 8), and current is supplied by an analog level signal obtained by D / A conversion of the supplied digital data. The capacitor of the program unit 71 (see FIG. 8) is charged. This program period is executed regardless of ON / OFF of the binary image data input to the gate controller 68. Thus, an analog value based on the 8-bit light amount correction data is written to the capacitor formed in the current program unit 71 every time one line period. That is, the accumulated charge of the capacitor formed in the current program unit 71 is always refreshed, and the driving current of the organic electroluminescence element 63 determined based on this is always kept constant.

  When the program period is completed, the gate controller 68 (see FIG. 8) immediately sets the lighting period by switching the SCAN_A signal to OFF and the SCAN_B signal to ON. As already described, the binary image data is supplied to the gate controller 68 (see FIG. 8) according to the time of image formation and the measurement of the amount of light. If the image data is OFF even during the lighting period, organic electroluminescence is provided. The element 63 is not lit. On the other hand, when the image data is ON, the organic electroluminescence element 63 continues to be lit for the remaining 306.25 μs (350 μs−43.75 μs) (actually there is a switching time of the control signal, so the light emission time is slightly shortened). ). As already described, in the embodiment, when measuring the amount of light of the organic electroluminescence element 63, a measurement period of 30 ms is assumed, so that the number of times of lighting at the time of measuring the amount of light is, for example, 100 times (that is, 100 lines). The dummy image information is generated by the controller 41.

  On the other hand, when the program period for the pixel circuit 69 (see FIG. 8) with the pixel number = 1 shown in FIG. 9 ends, the gate controller 68 (see FIG. 8) immediately applies to the pixel circuit 69 (see FIG. 8) with pixel number = 8. Sets the current program period. Thereafter, as in the procedure for the pixel circuit having the pixel number 1, as soon as the program period for the pixel circuit having the pixel number 8 is completed, the process proceeds to the lighting period of the organic electroluminescence element 63 (see FIG. 8) having the pixel number.

  In this way, the gate controller 68 (see FIG. 8) sets the pixel number in the main scanning direction = “1 → 8 → 2 → 7 → 3 → 6 → 4 → 5 → 1. Will be set. By adopting such a lighting order, the lighting timing of the nearest pixel is adjacent in time between adjacent pixel groups, so that the image step at the time of forming one line can be made inconspicuous.

  Here, the value set in the pixel circuit 69 (see FIG. 8) in the current program period is, for example, 8-bit light amount correction data as described above. Since the organic electroluminescence element 63 (see FIG. 8) is formed by a coating process such as spin coating, the adjacent pixel correlation becomes extremely high. Due to this effect, the light emission luminance of the organic electroluminescence element 63 (see FIG. 8) in the vicinity of the specific organic electroluminescence element 63 (see FIG. 8) becomes almost the same. Accordingly, since the correlation between the light amount correction data with respect to these adjacent organic electroluminescence elements 63 (see FIG. 8) is very high, for example, the light amount correction data with the pixel number = 1 and the light amount correction data with the pixel number = 8 do not change greatly. .

  In the current program period controlled by the gate controller 68 (see FIG. 8), the current value according to the light amount correction data is supplied to the pixel circuit 69 (see FIG. 8), and the capacitor in the pixel circuit 69 (see FIG. 8). Is charged by a so-called constant current source, and the time required for charging is (Equation 2).

  According to (Equation 2), the charging time is proportional to the capacitance, and if the capacitance C increases due to an increase in the wiring capacitance accompanying wiring routing, the charging time increases. In the embodiment, in order to dispose the source driver on the extended line of the light emitting element array and at the end in the long side direction of the glass substrate 50, in the pixel group farthest from the source driver 61 (see FIG. 8), If so, there is a concern about charging delay due to wiring capacity.

  However, in the embodiment, what is supplied by the source driver 61 (see FIG. 8) is light amount correction data, and since the value of the light amount correction data is high in one pixel group as described above, the same pixel. Within the group, V in (Equation 2) hardly changes. After all, in the current programming process, the difference in V between sequentially selected pixel numbers dominates the charging time, but the difference in V between originally selected pixel numbers is very small, so the charging time is very short. It becomes. Therefore, the shortage of the current program period due to the increase in the wiring length from the source driver 61 (see FIG. 8) has almost no problem in the embodiment, and as described so far, the source driver 61 ( The distance between the pixel circuit 69 (see FIG. 8) and the pixel circuit 69 (see FIG. 8) can be greatly separated.

  This situation is greatly different from a display that uses a current programming method to set a drive current for each pixel unit and reproduces multiple gradations such as 64 gradations and 256 gradations for each pixel unit. It can be said that this is a merit unique to the exposure apparatus 13 that can control lighting / extinction based on image data and set a drive current by a current programming method based on multi-value light quantity correction data.

<Light intensity measurement operation>
Next, the light quantity measurement unit 120 that is a part related to light quantity measurement in the image forming apparatus according to the embodiment of the present invention will be described. The light quantity measuring unit 120 measures the quantity of light emitted from the organic electroluminescence element 63.

  FIG. 10 is an explanatory diagram showing a main configuration of the light quantity measurement unit 120 according to the embodiment of the present invention. As shown in FIG. 10, the light quantity measurement unit 120 outputs a sensor selection signal to each of the plurality of sensor pixel circuits 130 provided corresponding to each of the plurality of organic electroluminescence elements 63 and each of the sensor pixel circuits 130. A selection signal generation circuit 140 to output and 16 detection processing circuits 170A to 170P are provided. The light quantity measurement unit 120 is an example of a light quantity measurement device, and the sensor pixel circuit 130 is an example of a light quantity detection circuit.

  The detection processing circuits 170 </ b> A to 170 </ b> P have the same configuration and will be described as the detection processing circuit 170 when it is not necessary to distinguish them. Further, the number of detection processing circuits 170 is not limited to 16, and m (m is a positive integer of 1 or more) may be provided.

  As described above, the sensor pixel circuit 130 and the selection signal generation circuit 140 are integrated and formed as a monolithic device of polysilicon together with the organic EL element and the TFT circuit 62. Therefore, in the sensor pixel circuit 130, the TFT circuit 62, and the like, when the same type of element such as a transistor is formed, it can be formed in the same process, so that the manufacturing process can be simplified.

  The selection signal generation circuit 140 is connected to the engine control unit 42 via the FPC 60 and is connected to each sensor pixel circuit 130 via the selection signal lines SEL1 to SEL5120. Note that “X” of the symbol “SELX” of the selection signal lines SEL1 to SEL5120 is the sensor pixel number SPNO given to the sensor pixel circuit 130 to be connected, and is selected when it is not necessary to distinguish them. This will be described as the signal line SEL.

  The selection signal generation circuit 140 generates a sensor selection signal for controlling the operation of the sensor pixel circuit 130 based on the sensor control input SC input from the engine control unit 42 via the FPC 60 via the selection signal line SEL. Output to the sensor pixel circuit 130. Thereby, the light amount detection timing can be controlled for each of the sensor pixel circuits 130.

  The sensor pixel circuit 130 is connected to the selection signal generation circuit 140 via the selection signal line SEL, and is connected to the detection processing circuits 170A to 170P via any of the driver lines RoA to RoP. The light amount is detected based on the sensor selection signal input from the selection signal generation circuit 140 and a sensor pixel circuit output signal is output to the detection processing circuit 170. Note that “X” of the code “RoX” of the driver lines RoA to RoP is an output ID (A to P) given to the detection processing circuit 170 as a connection destination, and it is not necessary to distinguish these This will be described as a driver line Ro.

  The detection processing circuits 170A to 170P are provided in the source driver 61 and are connected to the sensor pixel circuits 130 through the driver lines RoA to RoP, respectively, and from the sensor output signal lines DoA to DoP to the engine control unit through the FPC 60. 42. Then, the sensor pixel circuit output signal from the sensor pixel circuit 130 is acquired, and the light quantity measurement data is output to the FPC 60. Note that “X” of the symbol “DoX” of the sensor output signal lines DoA to DoP is the output ID (A to P) of the detection processing circuit 170 to be connected. The output signal line Do will be described.

  The sensor pixel circuit 130 is divided into a plurality of groups, and is connected to any one of the driver lines RoA to RoP according to the division. These sections of the sensor pixel circuit 130 will be described with reference to FIG.

  FIG. 11 is an explanatory diagram showing groups of sensor pixel circuits in the light amount measurement unit 120 according to the embodiment of the present invention. As shown in FIG. 11, the organic electroluminescence elements 63 are formed in a row at a resolution of 5120 elements and 600 dpi in the main scanning direction. Each of the organic electroluminescence elements 63 is assigned an identification number (hereinafter referred to as ELNO). This ELNO is a sequential number starting from 1, and is assigned in order from the organic electroluminescence element 63 formed at the end in the main scanning direction.

  5120 sensor pixel circuits 130 are formed in one-to-one correspondence with the organic electroluminescence elements 63, and each detects the light amount of the corresponding organic electroluminescence element 63. And the identification number (henceforth SPNO) of the sensor pixel circuit 130 is attached with the same number as ELNO of the corresponding organic electroluminescence element 63. For example, the SPNO of the sensor pixel circuit 130 provided corresponding to the organic electroluminescence element 63 having an ELNO of 3000 is 3000.

  Then, 320 (5120 ÷ 16 = 320) sensor groups are configured with n sensor pixel circuits 130 (hereinafter, n = 16 in the description of the present embodiment) having consecutive SPNOs as one unit. Yes. Each sensor group is assigned a group number of 1 to 320 in order from the smallest SPNO included in the sensor group. In each sensor group, line IDs a, b,..., P are assigned in order from the sensor pixel circuit 130 having the smallest SPNO. That is, the sensor pixel circuit 130 is given the same line ID every n (16).

  Further, 20 sensor groups (320 ÷ 16 = 20) with m sensor groups having consecutive group NOs (as described above, m is the number of arithmetic processing circuits 170 and m = 16 in the present embodiment) as one unit. ) Block is configured. Each block is assigned block numbers 1 to 20 in order from the smallest group number included in the sensor group.

  In each block, output IDs A, B,..., P are assigned in order from the sensor group with the smallest group number. The sensor pixel circuits 130 included in the sensor groups with output IDs A, B,..., P are respectively connected to the detection processing circuits 170A, 170B, DoP via driver lines DoA, DoB,. ..., connected to 170P. In other words, the same output ID is assigned to every m (16) sensor groups.

  In the following description, a group ID represented by a combination of a block NO and an output ID is also used as identification information for each sensor group for convenience. For example, a sensor group with a group number of 17 has a block number of 2 and an output ID of A, so the group ID is 2A.

  FIG. 12 is a circuit diagram illustrating a partial internal configuration of the light amount measurement unit 120 of the present embodiment. As shown in FIG. 12, the sensor pixel circuits 130 belonging to the same sensor group are connected to the same driver line Ro. Each sensor group is connected to a driver line Ro with the same output ID (A to P). For example, the groups 1A, 2A... 20A (20 groups in total) are connected to the driver line RoA, and the groups 1P, 2P,... 20P are connected to the driver line RoP.

  The driver lines RoA to RoP are connected to detection processing circuits 170A to 170P provided in the source driver 61, respectively. That is, a total of 16 detection processing circuits 170A to 170P are provided in the source driver 61 in correspondence with all the driver lines RoA to RoP. On the other hand, the selection signal generation circuit 140 is formed in the TFT circuit 62 as in the gate controller 68 shown in FIG. The selection signal generation circuit 140 (and the selection transistor 132: FIG. 13) is a switching circuit that inputs a sensor drive signal for driving the light amount sensor at a predetermined timing to be described later to the sensor pixel circuit 130 via the selection line SelX. Function as.

  FIG. 13 is a circuit diagram showing an internal configuration of the sensor pixel circuit 130 and the output processing circuit 170 according to the embodiment of the present invention.

  As shown in FIG. 13, the sensor pixel circuit 130 is connected in parallel to the light amount sensor 57, the light amount sensor 57, the capacitor 131 constituting the capacitive element, and the light amount sensor 57 and the capacitor 131 in series. And a switching selection transistor 132 for switching electrical connection with the charge amplifier 150 via the line Ro. The potential at one end, which is the side to which the light quantity sensor 57 and the selection transistor 132 of the capacitor 131 are connected, is Vs. Note that the other ends of the light quantity sensor 57 and the capacitor 131 are fixed to a predetermined potential Vp. The light quantity sensor 57 is an example of a light quantity detection element.

  The selection transistor 132 forms a switching circuit of the light amount sensor together with the selection signal generation circuit 140. The selection line Sel is connected to the gate of the selection transistor 132, and a sensor selection signal including an ON / OFF signal output from the selection signal generation circuit 140 is input to the selection transistor 132, and the selection transistor 132 is set according to the sensor selection signal. Performs ON / OFF operation.

  Then, a total of 20 sensor groups (block numbers 1 to 20) with the same output ID (A to P), in other words, a total of 320 sensor pixel circuits (16 × 20) 130 have the same output ID. Is connected to one driver line Ro marked with. Each driver line Ro is connected to the detection processing circuit 170.

  The detection processing circuit 170 includes a charge amplifier 150 and an analog / digital converter (hereinafter referred to as ADC) 160. The charge amplifier 150 is connected between an inverting input terminal and an output terminal of the operational amplifier 151, and an operational amplifier 151 having two input signal terminals, a non-inverting input terminal and an inverting input terminal, and one output signal terminal. The capacitor 152 is an example of the amplifier capacitance element, and the charge / discharge selection transistor 153 is connected in parallel with the capacitor 152.

  The non-inverting input terminal of the operational amplifier 151 is fixed to a predetermined reference voltage Vref, and the sensor pixel circuit 130 is connected to the inverting input terminal via a driver line Ro. Note that the output voltage of the operational amplifier 151 is Vro.

  A signal line CHG is connected to the gate of the charge / discharge selection transistor 153, and the charge / discharge selection transistor 153 performs an ON / OFF operation in accordance with a charge reset signal including an ON / OFF signal. The charge reset signal input via the signal line CHG is one of the sensor control inputs SC shown in FIG.

  The above-described charge amplifier 150 forms a sensor driving unit in cooperation with the capacitor 131 of the sensor pixel circuit 130.

  The ADC 160 is connected to the output terminal of the operational amplifier 151 of the charge amplifier 150. Based on the AD conversion start trigger signal SMPL which is one of the sensor control inputs SC, the output voltage Vro of the charge amplifier 150 is taken in and converted from analog to digital, and light quantity measurement data is output.

  FIG. 14 is a timing chart showing a light amount detection operation regarding each light amount sensor according to the embodiment of the present invention. In other words, this corresponds to a timing chart of the light amount measurement data reading operation performed for each light amount sensor 57. As described above, the output of the light amount sensor 57 which is the basis of the light amount measurement data is subjected to voltage conversion by the charge accumulation method in the source driver 61, and further amplified by a predetermined amplification factor and then converted from analog to digital. The following timing chart corresponds to this process.

  As shown in the timing charts of FIGS. 14A to 14G, the light amount measurement data based on the light amount sensor output of the light amount sensor 57 is obtained by using the charge of the capacitor 131 previously stored when the selection transistor 132 is switched. Extraction is performed by irradiating the light amount sensor 57 of the organic electroluminescence element 63 with light, and measurement is performed based on the charge of the capacitor 152 used to compensate for the lost charge. Therefore, in this embodiment, it corresponds to the light quantity sensor output based on the electric charge lost by the light irradiation of the organic electroluminescence element 63.

  Here, FIG. 14A is a diagram showing the charge state (charge state) of the capacitor 152 in the charge amplifier 150, FIG. 14B is a diagram showing the operation of the selection transistor 132, and FIG. FIG. 14D is a diagram showing the lighting timing of the organic electroluminescence element 63, FIG. 14D is a diagram showing the potential (Vs) on one end side to which the selection transistor 132 of the capacitor 131 is connected, and FIG. 14E is the output of the operational amplifier 151. FIG. 14F is a diagram showing the voltage (Vro), FIG. 14F is a diagram showing the AD conversion start trigger signal (SMPL) to be supplied to the analog / digital converter (ADC) 160, and FIG. It is a figure which shows the state from which data was obtained.

  First, the selection transistor 132 is turned on by receiving an ON signal from the selection signal generation circuit 140 at the timing from time t1 to time t2 via the selection line Sel (see FIG. 14B), and FIG. As shown in d), the capacitor 131 is charged, and the potential Vs on one end side of the capacitor 131 becomes the reference voltage Vref (S1: reset step). This reset step is an example of the first period.

  When the selection transistor 132 is turned off at time t2 (see FIG. 14B), the charge charged in the capacitor 131 is discharged and reduced by the photocurrent Is flowing through the light amount sensor 57, and FIG. As shown, the potential Vs on one end side of the capacitor 131 gradually decreases from the reference voltage Vref (S2: light irradiation discharge step).

  Then, after elapse of a predetermined time in this state, at time t3, the charge / discharge selection transistor 153 of the charge amplifier 150 is turned OFF (see FIG. 14A), the charge of the capacitor 152 becomes movable, and the charge amplifier 150 Is in a state in which the amount of light of the organic electroluminescence element 63 can be measured (S3: measurement start step).

  Further, when the charge / discharge selection transistor 153 is turned off, the selection transistor 132 is turned on at the same time as the time t3 or at a time t4 after a predetermined time from the time t3 (see FIG. 14B). Charge is supplied from the capacitor 152 of the charge amplifier 150 to the capacitor 131 from which charge has been lost between t2 and time t4. As a result, the potential at one end of the capacitor 131 returns to Vref (see FIG. 14D), and the output voltage Vro of the operational amplifier 151 of the charge amplifier 150 increases as shown in FIG. 14E (S4: Charge transfer step). It should be noted that since the photocurrent Is of the light quantity sensor 57 flows during the charge transfer step S4, Vro rises although it is a very small value. Note that the period from time t2 to t4 is an example of a second period, and the period from time t4 to t5 (charge transfer step) is an example of a third period.

  Thereafter, at time t5, the selection transistor 132 is turned off again, and Vro is determined. The analog / digital converter (ADC) 160 reads this determined voltage in conjunction with the AD conversion start trigger signal SMPL (see FIG. 14F) at the same time as the time t5 or after a predetermined time from the time t5. Thus, as shown in FIG. 14G, the effective light quantity measurement data is output from the light quantity measurement unit 120 via the sensor output signal line Do, whereby the light quantity measurement data reading operation is completed at time t8 (S5: Lead step).

  At time t6 after the AD conversion start trigger signal SMPL is input, the charge / discharge selection transistor 153 of the charge amplifier 150 is turned on (see FIG. 14A), and the capacitance of the capacitor 152 is reset.

  In addition, after the selection transistor 130 is turned off at the accumulation period of the above-described steps S2 to S4, that is, at time t2, the charge / discharge selection transistor 153 of the charge amplifier 150 is turned off, and the selection transistor 130 is turned on at time t5. The timing setting is preferably as short as possible from the viewpoint of shortening the waiting time of the image printing apparatus. However, from the viewpoint of ensuring a predetermined SN and voltage detection resolution, it is desirable that the potential difference Vout between the output voltage Vro and the reference voltage Vref determined at time t5 be as large as possible as shown in FIG. In this case, it is required to secure an accumulation period as long as possible. Therefore, the accumulation time is set from both viewpoints.

  As shown in FIG. 14C, in the light quantity measurement unit 120 of the present embodiment, the light emission operation of the organic electroluminescence element 63 is one raster period of the image forming apparatus 1 including the lighting Telon that is turned on and the program period Tpro that is turned off. Has Tras. The raster period Tras is a short period of about 350 μs as described above. Further, when the light amount sensor 57 is made of a material having a high light transmittance such as polysilicon, the photocurrent Is flowing based on the irradiated light becomes a very small amount.

  Therefore, in the present embodiment, the organic electroluminescence element 63 that is the target of light amount detection is driven in a plurality of raster periods Tras from time t0 to time t7, and the accumulation period from step S2 to step S4 is determined. Set over multiple raster periods. One raster period Tras is one line period of the exposure apparatus 13 described above, that is, one unit of a light emission period (exposure period) of the organic electroluminescence element 63 in the image forming apparatus 1. Therefore, predetermined SN and voltage detection resolution can be ensured by performing light amount detection for one raster period Tras or more, that is, for one light emission period or more of the light emitting element.

  In this way, the electrical connection between the charge amplifier 150 and the light quantity sensor 57 / capacitor 131 is switched by the selection transistor 132 provided in the sensor pixel circuit 130, so that a desired accumulation period is accurately switched. be able to.

  In addition, the light quantity sensor 57, the capacitor 131, and the driver line Ro are cut off by the selection transistor 132 during a period from time t2 to time t4. Therefore, the influence of noise from the charge amplifier 150 and the driver line Ro on the light quantity sensor 57 and the capacitor 131 is eliminated, so that the light quantity can be detected with high accuracy.

  Next, the selection signal generation circuit 140 that outputs a sensor selection signal will be described. FIG. 15 is a circuit diagram showing an internal configuration of the selection signal generation circuit 140 according to the embodiment of the present invention. As shown in FIG. 15, the selection signal generation circuit 140 includes 5120 AND circuits 141, a group selection signal output circuit 142, and a line selection signal output circuit 143.

  As shown in FIG. 15, the AND circuit 141 is a circuit that outputs a logical product of three inputs. Signals input to the AND circuit 141 are output from the selection timing signal ROEN, which is one of the sensor control inputs SC, the group selection signal gs output from the group selection signal output circuit 142, and the line selection signal output circuit 143. The line selection signal ls. Each output of the AND circuit 141 is input to the gate of the selection transistor 132 of the sensor pixel circuit 130 via the selection lines SEL1 to SEL5120.

  The block selection signal GSelDAT and the block switching clock signal GSelCLK are input to the group selection signal output circuit 142 as the sensor control input SC. The group selection signal output circuit 142 outputs group selection signals gs1 to gs20 based on the input block switching signal GSelDAT and block switching clock signal GSelCLK. These group selection signals gs1 to gs20 are generated corresponding to the respective block IDs shown in FIG. 11, and are AND circuits connected to the sensor pixel circuits 130 of the sensor groups to which the blocks NO1 to 20 are attached, respectively. 141 is output.

  FIG. 16 is a circuit diagram showing an internal configuration of the group selection signal output circuit 142 according to the embodiment of the present invention. As shown in FIG. 16, the group selection signal output circuit 142 is a shift register having 20 D flip-flops DFFg1, DFFg2,... DFFg20 connected in series. The D flip-flops DFFg1 to DFFg20 output group selection signals gs1 to gs20, respectively.

  The line selection signal output circuit 143 receives the line switching signal LSelDAT and the line switching clock signal LSelCLK as the sensor control input SC. The line selection signal output circuit 143 outputs line selection signals lsa to lsp based on the input line switching signal LSelDAT and line switching clock signal LSelCLK. The line selection signals lsa to lsp are generated corresponding to the line IDs shown in FIG. 11, and are AND circuits connected to the sensor pixel circuits 130 of the sensor groups to which the lines IDa to p are attached, respectively. 141 is output. For example, the line selection signal lsa is output to the AND circuit 141 connected to the sensor pixel circuit 130 whose line ID is a, that is, the sensor pixel circuit 130 whose SPNO is 1, 17,.

  FIG. 17 is a circuit diagram showing an internal configuration of the line selection signal output circuit 143 according to the embodiment of the present invention. As shown in FIG. 17, the line selection signal output circuit 143 is a shift register including 16 D flip-flops DFFla, DFFlb,... DFFlp connected in series. The D flip-flops DFFla to DFFlp respectively output line selection signals lsa to lsp.

  Next, the operation of the selection signal generation circuit 140 will be described with reference to FIGS. FIG. 18 is a diagram showing a partial configuration of the selection signal generation circuit 140 according to the embodiment of the present invention, and FIG. 19 is a timing chart for explaining the operation of the selection signal generation circuit 140 according to the embodiment of the present invention. . 18 and 19, an operation for generating a selection signal to be output to the selection signal line SEL259 will be described.

  As shown in FIG. 18, the sensor pixel circuit 130 with SPNO of 259 connected to the selection signal line SEL259 has a block NO of 2 and a line ID of c. In addition to ROEN, a group selection signal gs2 and a line selection signal lsc are input. That is, the input of the AND circuit 141 is connected to the output of the second stage D flip-flop DFFg2 in the group selection signal generation circuit 142 and the output of the third stage D flip-flop DFFlc in the line selection signal generation circuit 143. The

  As shown in FIG. 19, first, the line selection signal lsc is turned on at the rise of the line switching clock signal LSelCLK inputted for the third time after the line switching signal LSelDAT is turned on to the line selection signal generation circuit 143. It becomes. In this way, the sensor pixel circuit 130 whose line ID is c is selected.

  Next, the group selection signal gs2 is turned ON at the rise of the group switching clock signal GSelCLK input for the second time after the group switching signal GSelDAT is turned ON to the group selection signal generation circuit 142. In this way, the sensor pixel circuit 130 with the block ID 2 is selected.

  When the sensor selection timing signal ROEN for selecting one of the sensor pixel circuits 130 is input to the selection signal generation circuit 140, all the signals input to the AND circuit 141 are turned on. A sensor selection signal output via the signal line SEL259 is turned ON.

  Thereafter, when ROEN is turned off, the sensor selection signal is also turned off. When the group switching clock signal GSelCLK input for the third time rises, the group selection signal gs2 is turned OFF, and when the line switching clock signal LSelCLK input for the fourth time rises, the line selection signal lsc is turned OFF.

  In the above description, the case where the sensor selection signal output via the selection signal line SEL259 is ON has been described. However, at the timing when the sensor selection signal of the selection signal line SEL259 is ON, the block NO is 2 and the line ID is c. All the selection transistors 132 of the sensor pixel circuit 130 are turned on, that is, the sensor selection signals of the selection signal lines SEL259, SEL275, SEL291,... SEL483, SEL499 are turned on. This means that the light quantity detection operation is simultaneously switched by simultaneously switching the selection transistors 132 of the sensor pixel circuits 130 having the same block NO and the same line ID.

  Next, a light amount detection sequence of the entire light amount measurement unit 120 will be described. In the present embodiment, the light amount detection operation of one sensor pixel circuit 130 to which a predetermined line ID is assigned in each sensor group is performed in parallel for all sensor groups. Hereinafter, the light amount detection operation of the entire sensor group per line ID is referred to as group read. In this embodiment, since there are 16 sensor pixel circuits 130 with line IDs a to p for each sensor group, the light quantity detection for all the organic electroluminescence elements 63 is performed by performing group reading 16 times. Is called.

  First, the group read operation described above will be described. FIG. 20 is a timing chart for explaining the operation of the group read according to the embodiment of the present invention, and shows the group read related to the line ID “a”.

  As shown in FIG. 20, first, when the group switching signal GSelDAT is input at the start of the group read for the line IDa, the sensor selection circuit is set to the sensor pixel circuit whose block NO is 1 by the input of the group switching clock signal GSelCLK. , SEL241 are simultaneously output to the selection signal lines SEL1, SEL17,. In the sensor pixel circuit 130 (block ID is 1 and line ID is a) to which the sensor selection signal is input, the reset step S1 and the light irradiation discharge step S2 are started simultaneously.

  Then, each time the group switching clock signal GSelCLK is input, the block NO is sequentially switched from 1. That is, the reset step S1 and the light irradiation discharge step S2 regarding the sensor pixel circuit 130 of different blocks NO are sequentially started.

  Next, when the group switching signal GSelDAT is input before the start of the charge transfer step, the sensor selection signal is connected to the sensor pixel circuit 130 whose block NO is 1 by the input of the group switching clock signal GSelCLK. Are simultaneously output to the lines SEL1, SEL17,. In the sensor pixel circuit 130 (block ID is 1 and line ID is a) to which the sensor selection signal is input, the charge transfer step S4 and the read step S5 are started simultaneously. That is, charge transfer is simultaneously performed between the 16 sensor pixel circuits 130 whose line IDs of the sensor groups 1A to 1P are a and the detection processing circuits 170A to 170P.

  Then, each time the group switching clock signal GSelCLK is input, the block NO is sequentially switched from 1. That is, a sensor selection signal is sequentially output to the sensor pixel circuits 130 in different blocks NO, and the charge transfer step S4 and the read step S5 are started.

  In this way, the light amount detection operation (group read for line IDa) is performed for all the sensor pixel circuits 130 with line ID a.

  Here, the plurality of sensor pixel circuits 130 with the same output ID are connected to the same driver line Ro. In such a configuration, a single charge amplifier 150 can simultaneously perform a plurality of sensor pixel circuits 130 via the same driver line Ro. Therefore, the reset step S1 is connected to the same driver line Ro. A plurality of sensor pixel circuits 130 may be performed simultaneously. In the light irradiation discharge step S2, the sensor pixel circuit 130 is electrically disconnected from the driver line Ro. Therefore, the reset step S2 is also performed simultaneously in the plurality of sensor pixel circuits 130 connected to the same driver line Ro. May be.

  However, at least in the charge transfer step S4 (see FIG. 14: from time t4 to time t5), charge transfer is performed from each sensor pixel 130 to the detection processing circuit 170 via the driver line Ro. Therefore, the charge transfer step S4 is the same. It cannot be performed simultaneously in the plurality of sensor pixel circuits 130 connected to the driver line Ro.

  Therefore, in the light quantity measurement unit 120 of this embodiment, as shown in the timing chart of FIG. 20, in the group read related to the same line ID, the charge transfer step is performed for each of the sensor pixel circuits 130 to which the same output ID is assigned. Since the timing is controlled so that S4 does not overlap, the light amount detection of the plurality of light amount sensors 57 can be efficiently performed by one detection processing circuit 170. That is, since the light amount detection of the plurality of light amount sensors 57 can be performed by one detection processing circuit 170, it is not necessary to provide the detection processing circuit 170 as a pair with the sensor pixel circuit 130, thereby reducing the circuit scale and reducing the manufacturing cost. Can be suppressed.

  Furthermore, since the light irradiation / discharge step S2 that can be performed simultaneously is performed at a timing at which some of the sensor pixel circuits 130 with the same output ID are partially overlapped with each other, the time required for light amount detection is shortened. can do.

  As described above, the timing of the light amount detection operation can be switched for each of the plurality of sensor pixel circuits 130 using the selection transistor 132 provided in each sensor pixel circuit 130. Reduced and efficient light quantity detection can be performed.

  FIG. 21 is a timing chart for explaining the overall operation of the light amount measurement unit 120 according to the embodiment of the present invention. As shown in FIG. 21, the light amount detection operation of the entire light amount measurement unit 120 is started with the line switching signal LSelDAT input to the selection signal generation circuit 140 as a trigger. Each time the line switching clock signal LSelCLK is input, the group ID of the group lead is switched. Note that a period Tbl is given between the group reads for each line ID.

  In this embodiment, since there are 16 line IDs from a to p, it is possible to read out the light amount detection results in all the light amount sensors 57 in the period Tall by performing group read 16 times.

  As described above, the sensor pixel circuits 130 having the same line ID are sequentially detected one by one, so that when detecting the light quantity, the organic electroluminescence elements for each number of line IDs (16 in the present embodiment) in the main scanning direction. 63 should emit light. As a result, it is possible to suppress the influence of light other than the organic electroluminescence element 63 to be detected, for example, the light from the adjacent organic electroluminescence element 63, so-called crosstalk, and to detect the light quantity with high accuracy.

  In addition, when performing light quantity correction, each of the bright current and the dark current is detected, and the light quantity detection is performed by reflecting each light quantity detection result on the light emission quantity of the organic electroluminescence element 63. By performing the light amount measurement operation performed a plurality of times, it is possible to perform light amount correction with higher accuracy.

  In the embodiment, the lighting time of the organic electroluminescence element 63 constituting the exposure apparatus 13 is fixed, and the current value is changed to change the current value, so that the light amount of the organic electroluminescence element 63 is controlled. The present invention can be easily applied to a so-called PWM method in which the driving current value of a light emitting element such as the organic electroluminescence element 63 is fixedly set, and the light amount of the light emitting element is controlled by changing the lighting time. In this case, the contents of the first area described with reference to FIG. 6 may be replaced with “setting value of driving time for equalizing latent image cross-sectional areas”.

  Also, depending on the exposure apparatus, there are a plurality of light-emitting element arrays composed of organic electroluminescence elements, etc., and a latent image is formed by performing multiple exposures at substantially the same position with respect to the rotation direction of the photoreceptor. Is also known. Even in such an exposure apparatus, it is possible to apply the technical idea of the present invention by setting the light amount and the PWM time so that a latent image formed by a plurality of exposures does not contribute to development. . In such an exposure apparatus, a single light emitting element array does not form a latent image that contributes to development. For example, a sequence in which the amount of light is measured in units of lines between sheets can be considered.

  In the embodiment, the light quantity of the organic electroluminescence element 63 is measured using a light quantity sensor configured as a monolithic device of polysilicon same as the TFT circuit and the organic electroluminescence element. The technical idea of the present invention is It is not limited to. For example, the present invention can also be applied to a configuration in which a plurality of film-like light amount sensors are formed of amorphous silicon and arranged along the end surface of the glass substrate 50 (see FIG. 4).

  As described above, the image forming apparatus to which the electrophotographic method is applied has been described in the embodiment, but the present invention is not limited to the electrophotographic method. Since an RGB light source can be easily realized by an organic electroluminescence element, for example, a plurality of exposure apparatuses each having an R light source, a G light source, and a B light source are arranged as exposure light sources, and photographic paper is directly applied based on image data of each RGB color. Needless to say, the present invention can also be easily applied to an image forming apparatus that exposes the light.

  The light quantity detection circuit, the light quantity measurement device, and the image forming apparatus of the present invention have an effect that a desired light quantity measurement result can be obtained regardless of the sensitivity of the light detection element. For example, a printer, a copying machine, a facsimile machine, It is useful for an image forming apparatus used for a photo printer or the like.

1 is a configuration diagram of an image forming apparatus according to a basic embodiment of the present invention. The block diagram which shows the periphery of the developing station in the image forming apparatus of the embodiment Configuration diagram of an exposure apparatus in the image forming apparatus of the embodiment (A) is a top view of a glass substrate according to the exposure apparatus in the image forming apparatus of the embodiment, (b) is an enlarged view of the main part 2 is a block configuration diagram showing a configuration of a controller in the image forming apparatus of the embodiment. Explanatory drawing which shows the content of the light quantity correction data memory in the image forming apparatus of the embodiment Block configuration diagram showing a configuration of an engine control unit in the image forming apparatus of the embodiment Circuit diagram of exposure apparatus in image forming apparatus of same embodiment Explanatory drawing which shows the electric current program period which concerns on the exposure apparatus in the image forming apparatus of the embodiment, and the lighting period of an organic electroluminescent element Explanatory drawing which shows the main structures of the light quantity measurement part which concerns on embodiment of this invention. Explanatory drawing which shows the group of the sensor pixel circuit in the light quantity measurement part which concerns on embodiment of this invention. Circuit diagram showing a part of the internal configuration of the light quantity measurement unit of the present embodiment 1 is a circuit diagram showing an internal configuration of a sensor pixel circuit and an output processing circuit according to an embodiment of the present invention. It is a timing chart which shows the light quantity detection operation regarding each light quantity sensor which concerns on embodiment of this invention. 1 is a circuit diagram showing an internal configuration of a selection signal generation circuit according to an embodiment of the present invention. The circuit diagram which shows the internal structure of the group selection signal output circuit which concerns on embodiment of this invention 1 is a circuit diagram showing an internal configuration of a line selection signal output circuit according to an embodiment of the present invention. The figure which shows the structure of a part of selection signal generation circuit which concerns on embodiment of this invention Timing chart for explaining the operation of the selection signal generation circuit according to the embodiment of the present invention Timing chart for explaining group read operation according to an embodiment of the present invention Timing chart for explaining the overall operation of the light quantity measuring unit according to the embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2, 2Y, 2M, 2C, 2K Developing station 3 Recording paper 4 Paper feed tray 5 Recording paper conveyance path 6 Developer 8, 8Y, 8M, 8C, 8K Photoconductor 10 Developing sleeve 13, 13Y, 13M, 13C, 13K exposure apparatus 19 registration roller 20 pinch roller 21 recording paper passage detection sensor 41 controller 42 engine control unit 43 power supply unit 50 glass substrate 51 lens array 57 light quantity sensor 61 source driver 62 TFT circuit 63 organic electroluminescence element 64 sealing glass 65 Image memory 66 Light amount correction data memory 67 Timing generation unit 68 Gate controller 69 Pixel circuit 70 Driver unit 71 Current program unit 72 D / A converter 80 Computer 83 Controller CPU
87 Printer interface 90 Controller interface 91 Engine control CPU
98 operation panel 120 light quantity measurement unit 130 sensor pixel circuit 131 capacitor 132 selection transistor 140 selection signal generation circuit 141 AND circuit 142 group selection signal output circuit 143 line selection signal output circuit 150 charge amplifier 151 operational amplifier 152 capacitor 153 charge / discharge selection transistor 160 Analog to digital converter (ADC)
170, 170A-170P detection processing circuit DFFg1-DFFg20, DFFla-Dfflp D flip-flop

Claims (11)

A photodetecting element connected in series with the charge amplifier and generating a current corresponding to the amount of light irradiated;
A capacitive element connected in parallel with the photodetecting element;
A light quantity detection circuit comprising: a parallel circuit having the photodetecting element and the capacitive element; and a selection transistor connected between the charge amplifier and opening and closing an electrical connection between the parallel circuit and the charge amplifier. The light amount detection circuit according to claim 1,
The light detection element is a light amount detection circuit including polycrystalline silicon. A light amount detection circuit according to claim 1 or 2,
The charge amplifier,
The selection transistor electrically connects the parallel circuit and the charge amplifier in a first period, and the parallel circuit and the charge amplifier in a second period starting from the end of the first period. Electrically connecting between the parallel circuit and the charge amplifier in a third period starting from the end of the second period,
In the first period, the charge from the charge amplifier is accumulated in the capacitive element,
In the third period, the light quantity measuring device in which the charge consumed by the photodetecting element from the end of the first period to the end of the third period is transferred to the charge amplifier. The light quantity measuring device according to claim 3,
The charge amplifier is connected between an operational amplifier having two input signal terminals of a non-inverting input terminal and an inverting input terminal and one output signal terminal, and between one input terminal and an output terminal of the operational amplifier. An amplifier capacitive element, and a charge / discharge selection transistor that is connected in parallel with the first capacitive element and opens and closes an electrical connection between both ends of the first capacitive element,
The charge / discharge selection transistor electrically connects both ends of the first capacitor element at least in the first period, and electrically connects both ends of the first capacitor element in the third period. Light quantity measuring device that cuts off. The light quantity measuring device according to claim 3 or 4,
A plurality of the light amount detection circuits connected in parallel to each other are connected to the charge amplifier,
The light amount detection operation with one unit from the start of the first period to the end of the third period is performed independently for each of the light amount detection circuits, and the light amount detection operation in the light amount detection operation between the light amount detection circuits. A light quantity measurement device that is performed at a timing at which the third period does not overlap. The light quantity measuring device according to claim 5,
A plurality of charge amplifiers each connected to a plurality of the light quantity detection circuits;
A light quantity measuring device in which operations performed for each charge amplifier proceed simultaneously. The light quantity measuring device according to any one of claims 3 to 6,
The light quantity measuring device, wherein a period from the start of the second period to the end of the third period is longer than an exposure period in a light emitting element that is a target of light quantity detection. A plurality of light emitting elements for exposing the image carrier to form an image;
A light quantity measuring device according to any one of claims 3 to 7,
The light quantity detection circuit of the light quantity measuring device is provided corresponding to each light emitting element, and detects an amount of light emitted from the light emitting element. The image forming apparatus according to claim 8, wherein
The light emitting elements are arranged in the main scanning direction,
The light quantity measuring device is an image forming apparatus that performs light quantity measurement on one light emitting element in parallel in a predetermined number in the main scanning direction. The image forming apparatus according to any one of claims 8 and 9,
An image forming apparatus further comprising: a light amount correction unit that refers to a light amount of light emitted from the light emitting element measured by the light amount measuring device and corrects a light amount of light emitted from the light emitting element. The image forming apparatus according to any one of claims 8 to 10,
The light emitting element is an image forming apparatus configured with an organic electroluminescence element.

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