JP2009154530A - LIGHT EMITTING DEVICE, ITS DRIVING METHOD, AND ELECTRONIC DEVICE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make exposure power on a photoreceptor constant without being affected by deterioration of an OLED element 106 in case it occurs. <P>SOLUTION: A light receiving sensor 105 is disposed in a substrate 13 in order to detect light emission intensity. A detection-correction LUT 204 is provided for correcting variations in detection. In order that light emission intensity be detected under the constant condition (temperature), a temperature sensor is disposed to detect light emission intensity when temperature reaches a specified temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting device, a driving method thereof, and an electronic device, and in particular, a light emitting device using various light emitting elements such as an organic light emitting diode (hereinafter referred to as “OLED (Organic Light Emitting Diode)”) element and a driving method thereof, And electronic devices.

  When the electronic apparatus is, for example, an electrophotographic image forming apparatus, a plurality of LEDs and OLED elements are arranged on the substrate as an optical head for forming an electrostatic latent image on an image carrier such as a photosensitive drum. A light emitting device is used.

  In general, an optical head using LEDs or OLED elements as light emitting elements selectively illuminates (emits) each light emitting element in the very vicinity of the photosensitive member, and irradiates the emitted light on the photosensitive member as exposure light. Therefore, an image forming apparatus equipped with these has no movable part like a rotary polygon mirror in an image forming apparatus using a laser diode, has high reliability and quietness, and guides light emitted from the laser diode to a photosensitive member. An optical system and a large optical space as a light path are not required, and the image forming apparatus can be downsized.

  In particular, an optical head using an OLED element as a light emitting element can integrally form a drive circuit composed of a switching element made of a thin film transistor (hereinafter referred to as TFT) and an OLED element on a substrate such as glass. Therefore, the structure and the manufacturing process are simple, and there is a possibility that further downsizing and cost reduction can be realized as compared with an optical head using LEDs as light emitting elements.

  However, on the other hand, it is known that the OLED element causes so-called light quantity deterioration in which the light emission intensity gradually decreases as the OLED element is driven. Therefore, some correction of emission intensity is required to maintain the emission intensity of each OLED element in the same state as the initial state.

  For example, the light amount deterioration occurs in proportion to the light emission time. For this reason, since the light emission time is biased between the OLED elements that are frequently used and the OLED elements that are not frequently used, it is necessary to individually correct the emission intensity for each OLED element.

  It is also known that the emission intensity of the OLED element has temperature dependence. This temperature dependency is determined by the organic material constituting the OLED element, and can have both a positive characteristic in which the emission intensity increases at a high temperature and a negative characteristic in the opposite direction. The image forming process in the above-described electrophotographic image forming apparatus includes a step of fixing the toner image on the recording paper by heat and pressure, and the apparatus has a heat source that generates a large amount of heat. As the temperature changes, the light emission intensity of the OLED element changes.

  Regarding the light emission intensity correction, for example, a configuration disclosed in Patent Document 1 is known in an image forming apparatus equipped with a conventional optical head using an OLED element. The exposure apparatus (light emitting apparatus) in Patent Document 1 has a configuration in which a light receiving sensor is arranged on a glass substrate on which OLED elements are formed, and the light emission intensity of each OLED element is detected by the light receiving sensor.

  Further, according to Patent Document 1, the emission intensity Pgn of the nth OLED element in the exposure apparatus is detected in advance by an inspection jig, and at this time, the emission intensity Phn is also detected by the above-described light receiving sensor. The correction coefficient Pgn / Phn is calculated, and this correction coefficient is stored in a storage unit mounted on the exposure apparatus or the image forming apparatus. After the exposure apparatus is incorporated into the image forming apparatus, the OLED element is always determined by appropriately determining a new driving current of the OLED element based on the light amount detection result by the light receiving sensor and the correction coefficient stored in the storage unit. The initial light emission intensity of the device can be maintained.

  Further, according to Patent Document 1, the light emission intensity correction operation can be performed based on a command from the printer controller at any point in time after initialization of the image forming apparatus, before printing, or between sheets.

Japanese Patent Laid-Open No. 2004-082330

  However, since the characteristics of the OLED element change depending on the temperature, the temperature of the OLED element at the time of detection varies depending on the timing of performing the light amount detection operation. As a result, there is a problem that the light amount detection cannot be performed correctly.

  Further, when the light receiving sensor is formed on the glass substrate, there is a problem that variation in optical path characteristics from the OLED element to the photoconductor cannot be corrected. Accordingly, a light emitting device and a driving method thereof capable of accurately correcting the light emission intensity of the OLED element by detecting the light amount with high accuracy in consideration of the variation in the optical path characteristic without depending on the temperature characteristic of the OLED element are desired. It was rare.

  The present invention solves at least one of the above-described problems, and can be realized as the following forms or application examples.

  Application Example 1 A light emitting element and a unit circuit provided corresponding to the light emitting element are provided, and the unit circuit drives the light emitting element according to light emission control data generated based on image data. A method of driving a light emitting device, wherein the light emitting device includes a temperature sensor and a light receiving sensor, a temperature detecting step of detecting a temperature of the light emitting device by the temperature sensor, and light received from the light emitting element. And generating the light emission control data by correcting the image data according to the light detection step detected by the temperature sensor, the temperature of the light emitting device detected by the temperature sensor, and the detected value of the light detected by the light receiving sensor. And a control process.

  According to this method, even when a light-emitting element whose light emission intensity varies with temperature is used, light emission control of the light-emitting element is performed according to the temperature during light emission driving and the detected value of light. Therefore, since the light emission intensity of the light emitting element that changes according to the temperature can be detected with high accuracy, it is possible to correct the image data correctly and generate the light emission control data. As a result, the light emission intensity of the light emitting element can be appropriately corrected (for example, to the initial light emission intensity).

  Application Example 2 In the driving method of the light emitting device, the control step converts the detected value into an effective value, and generates the light emission control data using the converted effective value as the detected value. Features.

  If the detection sensitivity of the light receiving sensor is high, the detection value varies greatly. In such a case, the detected value is converted into an effective value. In this way, the detection data is averaged, so that variations in detection values are suppressed. As a result, the accuracy of the detection value is improved, so that the image data can be corrected correctly, and the light emitting element can be corrected to an appropriate light emission intensity.

  Application Example 3 In the driving method of the light emitting device, the control step corrects the image data in accordance with the detection value so that a correction characteristic when generating the light emission control data is nonlinear. Generating the light emission control data.

  In a light emitting element, there are cases where the light emission intensity (light quantity) has a nonlinear characteristic (for example, gamma characteristic) with respect to the driving voltage (current). In such a case, by correcting the image data nonlinearly so as to compensate for its nonlinear characteristics, the light emission quantity of the light emitting element can be corrected correctly with respect to the image data. As a result, the light emitting element can be corrected to an appropriate light emission intensity.

  Application Example 4 In the driving method of the light emitting device, the light emitting device further includes a condensing lens array that condenses light of the light emitting element, and the control step includes the light emitting element and the light condensing. The image data is corrected in accordance with the positional relationship with the neutral lens array.

  Depending on the positional relationship between the condensing lens array and the light emitting element, the amount of light emitted from the condensing lens array may vary with respect to the original light emission intensity of the light emitting element. In such a case, by correcting this variation in advance, it is possible to correct the image data correctly and generate the light emission control data.

  Application Example 5 In the driving method of the light-emitting device, the light detection step is a step of detecting light from the light-emitting elements by a plurality of the light receiving sensors, and the control step is the detected plurality of light-emitting devices. The image data is corrected in accordance with the detection value of each light receiving sensor.

  According to this method, since the light (light quantity) from the light emitting element is detected by the plurality of light receiving sensors, the detection accuracy can be improved. As a result, by correcting the image data in accordance with the detection values of the plurality of light receiving sensors, it is possible to correct the image data correctly and generate the emission control data.

  Application Example 6 In the driving method of the light emitting device, the control step includes a conversion table in which a correction value for correcting the image data is determined corresponding to the detected temperature and the detected value of light. And correcting the image data.

According to this method, since the image data is corrected using the conversion table, it is possible to reduce the processing load related to the image data correction processing.

  Application Example 7 In the driving method of the light emitting device, the correction value of the conversion table is obtained by performing a predetermined calculation process from a correction value determined for at least one reference temperature. It is a value.

  According to this method, since the number of conversion tables provided can be reduced, the storage capacity can be reduced. In addition, it is possible to correct image data correctly at an arbitrary temperature.

  Application Example 8 In the driving method of the light emitting device, the temperature detecting step includes a step of detecting whether or not the temperature of the light emitting device is a specified temperature, and the light detecting step includes the temperature detection. The light from the light emitting element is detected after the temperature of the previous light emitting device is detected to be a specified temperature in the process.

  According to this method, the correction process is performed at a specified temperature, that is, always at a constant temperature, so that it is possible to correct the image data correctly and generate the light emission control data.

  Application Example 9 In the driving method of the light emitting device, the light detecting step detects light from the light emitting element at a plurality of the specified temperatures.

  According to this method, correction processing is performed at a plurality of specified temperatures. Therefore, for example, if the specified temperature is set in the temperature range of the light emitting device that can be taken when the light emitting device is used, that is, when the light emitting element is driven to emit light, the image can be obtained even when the assumed temperature range is wide. Light emission control data can be generated by correcting the data correctly.

  Application Example 10 In the driving method of the light emitting device, the image data is either on data for causing the light emitting element to emit light or off data for not causing the light emitting element to emit light. When the data is the on data, the light emission control data is generated by correcting the image data, and when the image data is the off data, the light emission control data is generated without correcting the image data. Features.

  According to this method, since correction is not performed for off-data, the processing load related to correction can be reduced. In addition, the circuit configuration necessary for correction can be simplified.

  Application Example 11 In the driving method of the light-emitting device, the light-emitting device further includes a counter that acquires data for calculating the number of times of light emission of the light-emitting element, and the light detection step is performed based on the acquired data. After calculating that the number of times of light emission has reached a predetermined number of times, the light from the light emitting element is detected.

  The light quantity of the light emitting element deteriorates (decreases) according to the number of times of light emission correlated with the light emission time. Therefore, for example, by acquiring data that can calculate the number of times of light emission of the light emitting element, and detecting the light from the light emitting element when the number of times of light emission reaches a predetermined number of times, the degree of deterioration of the light emitting element is detected. Can do. Therefore, in this way, it becomes possible to correct the image data correctly and generate the light emission control data according to the deterioration of the light emitting element.

  Application Example 12 A light emitting element and a unit circuit that drives the light emitting element to emit light are provided, and the unit circuit emits light to drive the light emitting element according to light emission control data generated based on image data. A temperature sensor that detects a temperature of the light emitting device, a light receiving sensor that detects light from the light emitting element, a temperature of the light emitting device detected by the temperature sensor, and the temperature detected by the light receiving sensor A controller that corrects the image data and generates the light emission control data in accordance with a detection value of light.

  According to this configuration, even when a light-emitting element that varies depending on the temperature is used, light emission control of the light-emitting element is performed in accordance with the temperature at the time of light emission driving and the detected value of light (for example, light amount). Accordingly, since the amount of light emitted from the light emitting element that changes according to the temperature can be detected with high accuracy, it is possible to correct the image data correctly and generate the light emission control data. As a result, the light emitting element can be corrected to an appropriate light emission intensity.

  Application Example 13 Electronic equipment comprising the light emitting device.

  This light emitting device is provided in various electronic devices. A typical example of the electronic apparatus is an electrophotographic image forming apparatus using, for example, the light emitting device according to each aspect shown in the application example described above as an exposure device for an image carrier such as a photosensitive drum. In such an image forming apparatus, since the amount of light emitted from the light emitting element can be detected with high accuracy, the light emission control data can be generated by correcting the image data correctly. As a result, it is possible to provide an image forming apparatus (electronic device) capable of correctly correcting the light emission intensity of the light emitting element with respect to the image data.

<A: First Embodiment>
FIG. 1 is a perspective view showing a partial configuration of an image forming apparatus using the light emitting device 10 according to the first embodiment of the present invention. As shown in the figure, the image forming apparatus includes a light emitting device 10, a condensing lens array 11, and a photosensitive drum 12 as an image carrier. The light emitting device 10 includes a large number of light emitting elements (not shown in FIG. 1) arranged linearly on the surface of the substrate 13. These light emitting elements selectively emit light according to the form of an image to be printed on a recording material such as paper, that is, image data. The photosensitive drum 12 is supported by a rotating shaft extending in the main scanning direction which is also the arrangement direction of the light emitting elements, and rotates in the sub scanning direction in which the recording material is conveyed with the outer peripheral surface facing the light emitting device 10. .

  The condensing lens array 11 is disposed in the gap between the light emitting device 10 and the photosensitive drum 12. The condensing lens array 11 includes a large number of gradient index lenses arranged in an array with each optical axis directed toward the light emitting device 10. As the condensing lens array 11, there is, for example, SLA (Selfoc (registered trademark) lens array) manufactured by Nippon Sheet Glass Co., Ltd.

  Light emitted from each light emitting element of the light emitting device 10 passes through each refractive index distribution type lens of the condensing lens array 11 and then reaches the surface of the photosensitive drum 12. The surface of the photosensitive drum 12 is exposed by the emitted light. Therefore, a latent image (electrostatic latent image) corresponding to desired image data is formed by the exposed portion. In the present embodiment, a minimum unit that is formed by light emission of each light emitting element and controls the area of the exposed portion is referred to as “dot”. Therefore, an area of an exposed portion is formed by a set of dots.

  FIG. 2 is a diagram illustrating a schematic configuration of the light emitting device 10. In addition to the optical head 100, the light-emitting device 10 includes a control circuit 200, a driver 300 that outputs a driving voltage, and an image forming apparatus (for example, a printer) in which the light-emitting device 10 is incorporated as a circuit for driving the optical head 100. A temperature sensor 400 for detecting the temperature inside the image sensor, an EEPROM 500 for storing a correction value for image data and a detection correction value at the time of light detection, which will be described later, and an analog signal from the light receiving sensor 105 built in the optical head 100 are converted into A / D converter 600. The control circuit 200 controls these and controls the processing for setting correction values for image data, which will be described later.

  In addition to the light receiving sensor 105, the optical head 100 includes a plurality of OLED elements 106, which are light emitting elements, a TFT control circuit 104 composed of TFTs, and a pixel circuit 108 as a unit circuit that drives each of the OLED elements 106 to emit light. These drive circuits 107 are formed on a transparent substrate 13 such as glass. Thus, by forming the light receiving sensor 105 on the substrate 13 on which the OLED element 106 is formed, there is an advantage that the amount of light taken in becomes large when detecting the amount of light. A part of the drive circuit such as the control circuit 200 may be formed on the substrate 13 on which the OLED element 106 is formed, or may be formed by being mounted on another printed circuit board or the like.

  In the image forming apparatus according to the present embodiment, correction value setting processing for correcting image data according to the deterioration degree of the light emission intensity of each OLED element 106, and image data is corrected using the set correction value. Print processing to print. Therefore, first, the operation of the printing process will be described, and then the correction value setting process will be described.

(Print processing operation)
The EEPROM 500 stores correction values for correcting image data for each dot, that is, each OLED element 106, and is transferred to the correction register 201 in the control circuit 200 when the power is turned on. In the control circuit 200, original image data (on (1) / off (0) binary data) input from the outside (not shown) and correction values (4 bits / bit) stored in the correction register 201 are stored. Based on the dot), 8-bit light emission control data is generated by a correction LUT (look-up table) 202 and output to the driver 300.

  When the original image data is on, the emission control data differs for each dot to be formed, that is, the OLED element 106, depending on the correction value. On the other hand, when the original image data is off, since the light emission control data is also off data, all the dots are the same regardless of the correction value. This is because when light emission is turned on, correction is required according to the variation in light emission intensity of each OLED element 106, but when light emission is turned off, correction is not necessary.

  The reason why the correction value width (4 bits) does not become the light emission control data width (8 bits) is that the input voltage-output current characteristics of the pixel circuit 108 described later are not linear characteristics. In addition to image data, character data, ruled line data, and the like are included in the data input from the outside. However, since any data becomes two-dimensional matrix data during processing by the optical head, All are described as image data in the specification.

  The driver 300 generates an analog voltage according to the input 8-bit light emission control data. The light emission control data output from the driver 300, that is, the generated analog voltage is input to the TFT control circuit 104 in the optical head 100. In the TFT control circuit 104, the analog voltage is distributed to each pixel circuit 108 in the drive circuit 107. Although not described in detail here, a circuit using a demultiplexer, a shift register, or the like is widely known as a circuit for realizing a function of distributing data. In this embodiment, these circuits can be used.

  Each pixel circuit 108 in the driving circuit 107 supplies a current corresponding to the input analog voltage to the OLED element 106, and the OLED element 106 changes its emission intensity according to the supplied current. Light is emitted at a light emission intensity corresponding to the analog voltage generated by the driver 300.

  FIG. 3 is an explanatory diagram showing a circuit diagram of the pixel circuit 108, which is the same as a circuit generally well known for an OLED display or the like. While the switching transistor T1 is selected by the SEL terminal and is turned on, an analog voltage corresponding to the light emission control data is stored in the capacitor C1. The drive transistor T2 outputs a constant current from the VEL terminal to the OLED element 106 in accordance with the voltage stored in the capacitor C1. At this time, when the original image data is on and the OLED element 106 emits light, the analog voltage generated according to the light emission control data is a voltage according to the correction value, and the drive transistor T2 operates in the saturation region. This is the voltage to be generated. On the other hand, when the original image data is off and the OLED element 106 does not emit light, the analog voltage generated according to the light emission control data is a voltage that turns off the drive transistor T2, and thus does not depend on the correction value.

  Incidentally, as described above, the emission intensity of the OLED element 106 gradually decreases with the emission time, so that the emission intensity decreases according to the usage time of the optical head 100. In addition, since the frequency of use of each OLED element 106 varies depending on the image data, the amount of decrease in the emission intensity of each OLED element 106 varies. That is, according to the use of the optical head 100, the OLED element 106 has a problem that the absolute light emission intensity decreases and a difference in relative light emission intensity occurs between the OLED elements 106 in the optical head 100. there were. The former affects the overall density of printing, and the latter appears as uneven printing.

  Therefore, in this embodiment, even if the optical head 100 is used for a long time, the decrease in the absolute light emission intensity of the OLED element 106 is controlled so as not to affect the printing, and the relative intensity within the optical head 100 is controlled. The light emission intensity of each OLED element 106 is detected and the detection result is fed back as a correction value so that the unevenness due to the difference in light emission intensity is suppressed, and the light emission intensity of each OLED element 106 is corrected and controlled. Yes.

(Correction value setting processing operation)
The light emission detection control of each OLED element 106 will be described. The light receiving sensor 105 formed on the same substrate 13 as each OLED element 106 detects light from each OLED element 106 in the form of current or voltage. In the present embodiment, light from one OLED element 106 is detected by a plurality of light receiving sensors 105. By doing so, it can be expected to improve the detection accuracy. Of course, one light receiving sensor 105 may be used to detect one OLED element 106.

  The detected current or voltage of the light receiving sensor 105 is output to the A / D converter 600 mounted outside the optical head 100. In the present embodiment, the average value of the detected plurality of light receiving sensors 105 is output. Of course, the detection value of each light receiving sensor 105 may be multiplied by a weighting coefficient in accordance with the installation position of the light receiving sensor 105, the light receiving sensitivity, and the like.

  In the A / D converter 600, the current or voltage output from the light receiving sensor 105 is digitally converted and output to the control circuit 200. In the control circuit 200, a 4-bit correction value (4 bits / dot) for each OLED element 106 based on the digitally converted detection data and the detection correction value of each OLED element 106 stored in the detection correction register 203. And stored in the correction register 201 and the EEPROM 500. The detection correction register 203 stores the detection correction value read from the EEPROM 500 in advance (when the image forming apparatus is powered on or when detection control described later is started).

  Here, algorithms for detection control and correction control will be described in detail. The detection control is control until the correction value for correcting the image data is derived from the detection data and the detection correction value using the detection correction LUT 204. The correction control is performed using the correction LUT 202 to correct the image data and the correction. This is control until light emission control data is generated from the value.

  First, detection control until a correction value for correcting image data is derived from detection data and a detection correction value using the detection correction LUT 204 will be described.

  FIG. 4 is an explanatory diagram showing the detection correction LUT 204. As shown in the figure, the detection correction LUT 204 corresponds to the detection data width (8 bits) and the detection correction value width (8 bits) of the emission intensity in each OLED element 106 detected by the light receiving sensor 105 and the A / D converter 600. It is a table to which a correction value (4 bits) is assigned. Accordingly, correction values are assigned corresponding to detection data for one OLED element 106 and detection correction values for that one OLED element 106.

  Here, the detection correction value will be described. The detection correction value is a value for correcting a detection error generated between the exposure intensity on the photosensitive member exposed by light emission of each OLED element 106 and the detection data of light from the OLED element 106. That is, this is a value indicating the correlation between the exposure intensity on the photoconductor for each OLED element 106 and the detection data.

  The following are assumed as detection errors. That is, the variation between individuals of the light receiving sensor 105 and the A / D converter 600 is included in the detection data. Further, when the light receiving sensor 105 is arranged in fewer than the OLED elements 106 or when the positional relationship between the OLED element 106 and the light receiving sensor 105 is not constant, each dot is determined depending on the distance from the OLED element 106 to the light receiving sensor 105 or the like. Variations occur in the detection data at. Further, since the light receiving sensor 105 is on the substrate 13, it does not include variations in optical path characteristics in the condensing lens array 11. It is the detection correction value that corrects these variations. As shown in FIG. That is, a value corresponding to each OLED element 106 is set and stored in the detection correction register 203.

  As the detection correction value, a value measured precisely before shipment may be used. Specifically, after the optical head 100 is manufactured and the condensing lens array 11 is assembled, the light emission amount of each OLED element 106 is accurately measured using a jig or the like. At this time, correction control is performed and settings are made so that the light output from each OLED element 106 has the same exposure intensity on the virtual photoconductor. In this state, for each OLED element 106, detection data is output using the light receiving sensor 105 and the A / D converter 600, so that the light condensing property is not included without including variations in the light receiving sensor 105 and the A / D converter 600. It is possible to detect the amount of light under conditions that include variations in the lens array 11 (the same conditions as the exposure conditions on the photoconductor). In addition, it is good also as measuring before shipment according to several light emission intensity | strength. In this way, detection accuracy can be increased. In this case, since each OLED element 106 has a plurality of detection correction values corresponding to a plurality of light emission intensities, it has a two-dimensional detection correction value.

  Therefore, in the detection control, the detection correction LUT 204 is used to detect the detection data for each OLED element 106 detected at the detection execution timing described later for each OLED element 106 and the detection corresponding to the OLED element 106 having the detection data. The correction value and the correction value assigned to the correction value are derived as the correction value of the OLED element 106.

  Here, in the present embodiment, as described above, the assigned correction value is a 4-bit correction value width with respect to the 8-bit detection data width and the 8-bit detection correction value width. This is because a high-precision correction value is calculated from high-precision detection data (8 bits) and a high-precision detection correction value (8 bits), and then the lower-order bits are rounded down to obtain a final correction value (4 bits). It is because it is doing. Therefore, the correction value is linear 4-bit data.

  With the above series of detection controls, a correction value for obtaining equal exposure intensity on the photosensitive drum 12 can be derived. Then, the data stored in the EEPROM 500 and the correction register 201 are updated with the correction value derived by the detection control.

  Next, a description will be given of control until light emission control data is generated from image data and a correction value using the correction LUT 202. FIG. 6 is an explanatory diagram showing the correction LUT 202. In the correction LUT 202, light emission control data for correcting the image data in accordance with the characteristic variation of each OLED element 106 is set for each OLED element 106 corresponding to the image data.

  The image data is binary (1 and 0) data for controlling whether each OLED element 106 emits light or not according to the dot to be formed. On the other hand, as shown in FIG. That is, a value corresponding to each OLED element 106 is set and stored in the correction register 201. As described above, the correction value is a value for causing each OLED element 106 to emit light with uniform light emission intensity.

  In this embodiment, the correction LUT 202 is a 4-bit linear correction value that has a gamma characteristic or a square characteristic that is a non-linear characteristic, and generates and assigns 8-bit light emission control data. By doing so, the data stored in the EEPROM 500 is not 8-bit light emission control data but a 4-bit correction value. Therefore, for example, in the case of the optical head 100 mounted on an image forming apparatus (for example, a printer) that performs printing at 600 dpi in A4 size, the number of OLED elements 106 is about 5000 (4960 in this embodiment), and all Circuits formed in the light emitting device 10 can be reduced by reducing the data amount of correction values stored in each of the OLED elements 106 (that is, Nos. 1 to 4960 dots) by half, or reducing the processing load related to storage capacity and correction. Can be simplified.

  Further, the execution timing of the above-described detection control and correction control will be described with reference to the flowchart of FIG. First, when the image forming apparatus (for example, printer) is turned on, the light emitting device 10 is turned on (step S1). Next, the light emitting device 10 reads the correction value from the EEPROM 500 to the correction register 201 as a preparation for printing based on print data including image data sent from the outside (step S2). At the same time, or at the stage where the reading process is completed, the control circuit 200 starts temperature detection by the temperature sensor 400 (step S3). If the image forming apparatus including the light emitting device 10 is ready for printing at the stage where the correction value has been read to the correction register 201 (step S20: Yes), the image data is sent from the outside according to the image data sent from the outside. Print.

  Usually, an image forming apparatus needs to be heated at a high temperature in the fixing process, and therefore has a function of warming up in the image forming apparatus, that is, a mechanism for intentionally generating heat. That is, for a while after the image forming apparatus is turned on, the temperature in the image forming apparatus changes rapidly. For example, when the above-described detection control is performed in such a situation, the characteristics of the OLED element 106 vary greatly depending on the temperature because of the temperature dependence as described above. It is practically impossible to correctly detect the degree of strength deterioration.

  Therefore, in the present embodiment, detection control is performed when the temperature detected by the temperature sensor 400 reaches a specified temperature, assuming that the temperature of each OLED element 106 at the time of detecting the amount of light is almost constant each time. did. Specifically, after the specified temperature is detected by the temperature sensor 400 (step S4), the control circuit 200 determines that each OLED element 106 is to detect the emission intensity when printing is in progress or not waiting for printing (step S10: No). A predetermined voltage is applied to emit light (step S11), light from each OLED element 106 is detected by the light receiving sensor 105 (step S12), and A / D conversion is performed by the A / D converter 600 (step S13). A detection correction value corresponding to the converted detection data is obtained using the detection correction LUT 204, and a correction value is newly assigned as described above (step S15). Of course, if printing is in progress or waiting for printing (step S10: Yes), the process waits until printing is completed.

  The data in the correction register 201 and the EEPROM 500 are updated with the assigned new correction value. Before a correction value is newly assigned using the detection correction LUT 204, it is necessary to read the detection correction value from the EEPROM 500 to the detection correction register 203 (step S14). This is because the temperature in the image forming apparatus is the specified temperature. Do it in advance without waiting for it to reach. In the present embodiment, detection control is performed after waiting for execution of printing in a waiting state, but of course, it may be interrupted.

  According to the configuration of the present embodiment, the light receiving sensor 105 is disposed in the substrate 13 in order to detect the light emission intensity of each OLED element 106. In addition, the detection accuracy comes from the characteristic variation of the light receiving sensor 105, the characteristic variation of the A / D converter 600, the difference between the exposure intensity on the photoconductor and the intensity of the light incident on the light receiving sensor 105 disposed in the substrate 13, and the like. In order to prevent the deterioration of the detection correction, a detection correction LUT 204 is arranged. As a result, even when the OLED element 106 whose light amount deterioration occurs in proportion to the light emission time is used, it is possible to prevent the light emission intensity of the optical head 100 from being lowered overall, and at the same time, Variations in exposure intensity for each dot formed by light emission can also be suppressed.

  In the present embodiment, the temperature sensor 400 is used to define the detection control timing. As a result, even when the OLED element 106 whose emission intensity greatly changes depending on the temperature is used, detection control is always performed under a constant condition (temperature), so that the emission intensity of the OLED element 106 is deteriorated. It becomes possible to detect correctly.

<B: Second Embodiment>
In the first embodiment, the timing for performing detection control is defined by the temperature detected by the temperature sensor 400. In the second embodiment, in addition to the temperature detected by the temperature sensor 400, data for calculating the number of times of light emission that correlates with the light emission time of the OLED element 106 is acquired, thereby defining the timing for performing detection control.

  FIG. 9 is a diagram illustrating a schematic configuration of the light emitting device 10 according to the second embodiment. As shown in the figure, the present embodiment has a configuration in which a print counter 700 is added to the light emitting device 10 in the first embodiment as means for obtaining data for calculating the number of times of light emission of the OLED element 106. . Since other configurations are the same as those of the first embodiment, description thereof will be omitted.

  The print counter 700 counts how many sheets have been printed after the power is turned on, or how many times each OLED element 106 has been lit after the power is turned on. Then, the count data is input to the control circuit 200. The control circuit 200 performs detection control and correction control according to the input count data.

  The execution timing of detection control and correction control in the present embodiment will be described using the flowchart shown in FIG. In addition, FIG. 10 adds step S5 in the flowchart (refer FIG. 8) which shows the implementation timing of the detection control and correction | amendment control in the said 1st Embodiment.

  First, the power source of the image forming apparatus (for example, a printer) and the power source of the light emitting device 10 are turned on (step S1). Next, the light emitting device 10 reads the correction value from the EEPROM 500 to the correction register 201 as a preparation for printing based on the print data sent from the outside (step S2). At the same time, or at the stage where the reading process is completed, the control circuit 200 starts temperature detection by the temperature sensor 400 (step S3). If the image forming apparatus including the light emitting device 10 is ready for printing at the stage where the correction value has been read to the correction register 201 (step S20: Yes), the image data is sent from the outside according to the image data sent from the outside. Print. Simultaneously with printing, the print counter 700 counts the accumulated print state after power-on. Then, as a result of the determination based on the count number, if the number of times of light emission has reached the specified value (step S5: Yes), the process proceeds to step S11 and the subsequent processing is performed.

  As described above, in this embodiment, detection control is performed when both the condition that the temperature detected by the temperature sensor 400 reaches the specified temperature and the condition that the cumulative printing count reaches the specified count are cleared. The temperature characteristics of the OLED element 106 vary depending not only on the temperature in the image forming apparatus but also on the temperature in the substrate 13. Therefore, in this embodiment, the detection control is performed without being affected by the temperature characteristics of the OLED element 106 by performing the detection control after the number of times of light emission of the OLED element 106 reaches the specified value and the substrate 13 is also sufficiently warmed. Can be performed.

  In the present embodiment, the temperature sensor 400 and the print counter 700 are used to define the detection control execution timing. As a result, even when the OLED element 106 that changes greatly depending on the temperature is used, detection control is always performed under a constant condition (temperature), so that pure degradation of the emission intensity of the OLED element 106 is detected. It becomes possible.

<C: Third Embodiment>
Next, a third embodiment will be described. In the first embodiment and the second embodiment described above, after the temperature detected by the temperature sensor 400 reaches one specified temperature (for example, 30 ° C.) in order to perform detection control under a constant condition (temperature) at all times. Although the detection control and the correction control are performed, in the third embodiment, the detection control and the correction control are performed at a temperature other than one specified temperature.

  For example, when the temperature of the image forming apparatus incorporating the light emitting device 10 rises slowly, the time until the temperature reaches the specified temperature becomes longer. Therefore, in printing performed until the specified temperature is detected, the light emission intensity is increased. Many situations that cannot be corrected correctly occur. Alternatively, for example, when the temperature at the time of use varies depending on the season or installation environment, the temperature of each OLED element 106 at the time of printing is different from the specified temperature, so that the image data may not be corrected correctly.

  Therefore, if correction processing is performed at a plurality of specified temperatures instead of one specified temperature, the correction processing can be performed within the temperature range when the light emitting device is used. Therefore, even when the assumed temperature range during use is wide, it is possible to correct the image data correctly and generate the light emission control data.

  In the present embodiment, two cases, ie, a case where detection control and correction control are performed at “C1: plural specified temperatures” and a case where detection control and correction control are performed at “C2: arbitrary temperature” will be described as examples. To do. In the present embodiment, the configuration of the light emitting device 10 is the same as that of the first embodiment and the second embodiment. Further, the execution timing of the detection control and the correction control is the same as that in the first embodiment and the second embodiment. Therefore, the description about these is abbreviate | omitted.

“C1: Multiple specified temperatures”
The detection control in this embodiment will be described with reference to FIG. 8 showing a flowchart in the first embodiment as an example. In this embodiment, in the specified temperature detection process in step S4, it is detected whether any of the four specified temperatures is 10 ° C, 20 ° C, 30 ° C, or 40 ° C. Then, for each OLED element 106, the detection correction LUT 204 determined for the specified temperature detected from the detection data obtained by the processing from step S11 to step S13 and the detection correction value stored in the detection correction register is used. The correction value of each OLED element 106 is derived.

  In the present embodiment, as shown in FIG. 11, the control circuit 200 includes four detection correction LUTs (204a, 204b, 204c, and 204d) corresponding to the specified temperatures of 10 ° C., 20 ° C., 30 ° C., and 40 ° C. Is provided. That is, in accordance with the temperature characteristics of each OLED element 106, all detection data and correction values corresponding to all detection correction values are assigned at each specified temperature. Therefore, in the detection control, a correction value for correcting the image data can be derived from the detection data and the detection correction value using the detection correction LUT 204 corresponding to the specified temperature detected by the temperature sensor 400.

  In the present embodiment, it is preferable to use a value that is precisely measured before shipment as the detection correction value. Specifically, after the optical head 100 is manufactured and the condensing lens array 11 is assembled, the amount of light emitted from each OLED element 106 is precisely measured for each specified temperature using a jig or the like. At this time, correction control is performed and settings are made so that the light output from each OLED element 106 has the same exposure intensity on the virtual photoconductor. In this state, by outputting detection data for each OLED element 106 using the light receiving sensor 105 and the A / D converter 600, the light collecting sensor 105 and the A / D converter 600 are not included, and the condensing lens is not included. It is possible to detect the amount of light under conditions including variations in the array 11 (the same conditions as the exposure conditions on the photoconductor).

  Through the above series of detection controls, it becomes possible to derive a correction value for obtaining an equal exposure intensity on the photosensitive drum 12 at each specified temperature. Then, the data stored in the EEPROM 500 and the correction register 201 are updated with the correction value derived by the detection control.

  In the present embodiment, the temperature detection process (step S4) may be continuously performed. When a new specified temperature is detected in step S4, a correction value for correcting the image data is detected from the detection data and the detection correction value using the detection correction LUT 204 corresponding to the newly detected specified temperature. Repeat the derivation process. For example, if the newly detected specified temperature is 40 ° C., the correction value is derived using the detection correction LUT 204d corresponding to 40 ° C. Thereafter, correction control until generation of light emission control data from the correction value is the same as in the first and second embodiments.

  In the present embodiment, the detection correction LUT 204 is provided corresponding to each specified temperature, but the present invention is not necessarily limited thereto. For example, a predetermined calculation process may be added to the detection correction LUT 204 for one specified temperature to generate the detection correction LUT 204 for another specified temperature. When the relationship between each specified temperature and the light emission intensity of each OLED element 106 at the specified temperature is expressed by some coefficient (for example, temperature coefficient), detection corresponding to the specified temperature that differs depending on the arithmetic processing is performed as described above. A correction LUT 204 can be generated.

  As an example, a detection correction LUT 204c corresponding to a specified temperature of 30 ° C. is used as a reference LUT, and a temperature coefficient calculation process is added thereto to generate a detection correction LUT 204b corresponding to 20 ° C. and a detection correction LUT 204d corresponding to 40 ° C. This is shown in FIG. Specifically, each correction value H3 assigned to the detection correction LUT 204c corresponding to 30 ° C. is multiplied or divided by the temperature coefficient K1, or the temperature coefficient K2 is added or subtracted. The correction value H4 and the correction value H2 assigned to the detection correction LUT 204d and the detection correction LUT 204b corresponding to ° C and 20 ° C are calculated, respectively, and the detection correction LUT 204d and the detection correction LUT 204b corresponding to 40 ° C and 20 ° C are generated. In this way, although the circuit scale is increased to perform the arithmetic processing, the storage capacity can be reduced to the extent that the detection correction LUT 204b and the detection correction LUT 204d are stored.

“C2: Arbitrary temperature”
As an example, the detection control in the present embodiment will be described with reference to step FIG. 8 in the first embodiment, similar to the plurality of specified temperatures. In the present embodiment, in the specified temperature detection process in step S4, the specified temperature is not a predetermined temperature, but a temperature when a predetermined time has elapsed from the start of detection. Therefore, the detected temperature is an arbitrary temperature unlike the specified temperature. For each OLED element 106, the detected arbitrary temperature detected from the detection data obtained by the processing from step S11 to step S13 and the detection correction value stored in the detection correction register 203 corresponds to the arbitrary temperature. A correction value of each OLED element 106 is derived using the detection correction LUT 204.

  In the present embodiment, the control circuit 200 has a function of generating a detection correction LUT 204n corresponding to an arbitrary temperature. That is, a detection correction LUT 204 corresponding to one reference temperature or a plurality of reference temperatures is provided, and a predetermined calculation process is added to the provided detection correction LUT 204 to generate a detection correction LUT 204n for the detected arbitrary temperature. When the relationship between the emission intensity of each OLED element 106 and the temperature is expressed by some coefficient (for example, temperature coefficient), the detection correction LUT 204 corresponding to the reference temperature is used by the arithmetic processing in this way. The detection correction LUT 204n for an arbitrary temperature can be generated. In this way, although the circuit scale increases to perform the arithmetic processing, the storage capacity corresponding to the capacity for storing the detection correction LUT 204n corresponding to the arbitrary temperature can be reduced. Note that the reference temperature may be the specified temperature described above.

  In the present embodiment, an example of a method for generating the detection correction LUT 204n corresponding to an arbitrary temperature is shown in FIG. FIG. 13A is a schematic diagram showing how the correction value Hn of the detection correction LUT 204n corresponding to the arbitrary temperature Tn ° C. is calculated and generated from the correction value H3 of the detection correction LUT 204c corresponding to one reference temperature “30 ° C.”. FIG. For example, when the light emission intensity of each OLED element 106 changes linearly with respect to temperature, the temperature coefficient K3 that is the slope of this line and the temperature difference ΔT between the detected temperature and the reference temperature (30 ° C.) In this example, the correction value Hn is obtained by adding (or subtracting) the multiplication values of and to the correction value H3, and the detection correction LUT 204n corresponding to the arbitrary temperature Tn ° C. is generated. When the emission intensity of each OLED element 106 is proportional to the temperature, the correction value Hn is obtained by multiplying or dividing the correction value H3 of the detection correction LUT 204c corresponding to the reference temperature of 30 ° C. by a temperature coefficient, A detection correction LUT 204n corresponding to the arbitrary temperature Tn ° C. can also be generated.

  In FIG. 13B, as an example of a plurality of reference temperatures, a detection correction LUT 204n corresponding to an arbitrary temperature Tn is calculated from a detection correction LUT 204a and a detection correction LUT 204d corresponding to two reference temperatures (10 ° C. and 40 ° C.). It is the schematic diagram which showed a mode that it produced | generated. As shown in the figure, the correction value corresponding to the arbitrary temperature Tn between the correction value H1 of the detection correction LUT 204a corresponding to the reference temperature of 10 ° C. and the correction value H4 of the detection correction LUT 204d corresponding to the reference temperature of 40 ° C. The case where the detection correction LUT 204n corresponding to the arbitrary temperature Tn is generated by obtaining Hn by linear interpolation is shown. Note that the interpolation is not necessarily linear but may be nonlinear interpolation.

  Thus, in the detection control, a correction value for correcting the image data can be derived from the detection data and the detection correction value using the detection correction LUT 204n corresponding to the arbitrary temperature detected by the temperature sensor 400. As a result, it is possible to derive a correction value for obtaining an equal exposure intensity on the photosensitive drum 12 at an arbitrary temperature by a series of detection controls. Then, the data stored in the EEPROM 500 and the correction register 201 are updated with the correction value derived by the detection control.

  In the present embodiment, the temperature detection process (step S4) may be continuously performed. When a new temperature is detected in step S4, a detection correction LUT 204 corresponding to the detected new temperature is calculated and generated, and a correction value for correcting the image data from the detection data and the detection correction value. The process of generating is repeated. Thereafter, correction control until generation of light emission control data from the correction value is the same as in the first and second embodiments.

<D: Modification>
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible. Also, two or more of the modifications shown below can be combined.

(Modification 1)
In each of the embodiments described above, the detection correction value is stored in the EEPROM 500 in the same manner as the correction value. However, the detection correction value is not limited to this and is stored in a read-only memory (ROM) that cannot be rewritten after shipment from the factory. An aspect may be sufficient. Unlike the correction value, the detection correction value is not updated after shipment from the factory. Therefore, the detection correction value only needs to be stored in a nonvolatile memory. In consideration of the entire system, the detection correction value is stored in the EEPROM 500 or in another ROM. You only have to select whether to store.

(Modification 2)
Each of the embodiments described above is a mode in which the light emission control data obtained by correcting the image data with the correction value is supplied to the optical head 100. However, the correction value is stored in the optical head 100, and the image data is stored in the optical head 100. A mode in which correction processing is performed may be used. In this case, since the output from the driver 300 does not include the content of correction, the output is binary image data, and the optical head 100 includes a correction memory instead of the correction register.

(Modification 3)
Each of the above-described embodiments is a mode in which various controls are performed after the correction value is read to the correction register 201 and the detection correction value is read to the detection correction register 203, but without using the correction register 201 or the detection correction register 203, A mode in which various controls are performed by directly communicating with the EEPROM 500 is also possible. In this case, although there is a demerit that it takes time for various controls, it is not necessary to prepare a register in the control circuit 200, so that the circuit scale can be reduced.

(Modification 4)
Each of the above embodiments is an aspect in which the correction LUT 202 and the detection correction LUT 204 are individually provided. However, as long as the functions described in the respective embodiments are provided, these may be combined into one LUT.

(Modification 5)
Each of the above-described embodiments is a mode in which the correction LUT 202 and the detection correction LUT 204 are used for detection control and correction control, respectively. However, if the functions described in each embodiment are provided, these functions are performed in the LUT. Instead, it may be realized by arithmetic processing. In this way, although the circuit scale increases to perform the arithmetic processing, the storage capacity can be suppressed to be small by the capacity for storing the LUT.

(Modification 6)
In each of the above embodiments, the light emitting element is an OLED element, but may be an inorganic light emitting diode or LED (Light Emitting Diode). In short, all elements that emit light in accordance with the supply amount of electric energy (application of electric field or supply amount of current) can be used as light-emitting elements.

<E: Electronic equipment>
Next, with reference to FIG. 14, an image forming apparatus which is one aspect of the electronic apparatus according to each of the above-described embodiments will be described. This image forming apparatus is a tandem type full color image forming apparatus using a belt intermediate transfer body system.

  In this image forming apparatus, four light-emitting devices 10 (10K, 10C, 10M, and 10Y) each having the same configuration are replaced with four photosensitive drums 110 (image bearing members having the same configuration). 110K, 110C, 110M, 110Y) are arranged at positions facing the image forming surface. The light emitting device 10 (10K, 10C, 10M, 10Y) has the same configuration as that of the light emitting device 10 according to each of the above embodiments.

  As shown in FIG. 14, this image forming apparatus is provided with a driving roller 121 and a driven roller 122, and an endless intermediate transfer belt 120 is wound around these driving roller 121 and driven roller 122. As shown by the arrows, the periphery of the driving roller 121 and the driven roller 122 is rotated. Although not shown, tension applying means such as a tension roller that applies tension to the intermediate transfer belt 120 may be provided.

  Around the intermediate transfer belt 120, four photosensitive drums 110 (110K, 110C, 110M, 110Y) having a photosensitive layer on the outer peripheral surface are arranged at predetermined intervals. The subscripts “K”, “C”, “M”, and “Y” mean that they are used to form black, cyan, magenta, and yellow visible images, respectively. The same applies to other members. The photosensitive drum 110 (110K, 110C, 110M, 110Y) is rotationally driven in synchronization with the driving of the intermediate transfer belt 120.

  Around each photosensitive drum 110 (110K, 110C, 110M, 110Y), there is a corona charger 111 (111K, 111C, 111M, 111Y), a light emitting device 10 (10K, 10C, 10M, 10Y), and a developing unit. 114 (114K, 114C, 114M, 114Y) are arranged. The corona charger 111 (111K, 111C, 111M, 111Y) uniformly charges the image forming surface (outer peripheral surface) of the corresponding photosensitive drum 110 (110K, 110C, 110M, 110Y). The light emitting device 10 (10K, 10C, 10M, 10Y) writes an electrostatic latent image on the charged image forming surface of each photosensitive drum. In each light emitting device 10 (10K, 10C, 10M, 10Y), a plurality of light emitting elements 20 are arranged along the bus (main scanning direction) of the photosensitive drum 110 (110K, 110C, 110M, 110Y). The electrostatic latent image is written by irradiating the photosensitive drum 110 (110K, 110C, 110M, 110Y) with light by the plurality of light emitting elements 20. The developing device 114 (114K, 114C, 114M, 114Y) has a visible image (that is, a visible image) on the photosensitive drum 110 (110K, 110C, 110M, 110Y) by attaching toner as a developer to the electrostatic latent image. ).

  The black, cyan, magenta, and yellow developed images formed by the four-color single-color image forming stations are superimposed on the intermediate transfer belt 120 by being sequentially primary-transferred onto the intermediate transfer belt 120. As a result, a full-color visible image is formed. Inside the intermediate transfer belt 120, primary transfer corotrons 112 (112K, 112C, 112M, 112Y) as four transfer units are arranged. The primary transfer corotron 112 (112K, 112C, 112M, 112Y) is disposed in the vicinity of the photosensitive drum 110 (110K, 110C, 110M, 110Y), and the photosensitive drum 110 (110K, 110C, 110M, 110Y). The electrostatic image is electrostatically attracted from the toner image to transfer the visible image to the intermediate transfer belt 120 passing between the photosensitive drum and the primary transfer corotron.

  A sheet 102 as an object (recording material) on which an image is to be finally formed is fed one by one from the sheet feeding cassette 101 by the pickup roller 103 and is subjected to secondary transfer with the intermediate transfer belt 120 in contact with the driving roller 121. Sent to the nip between the rollers 126. The full-color visible image on the intermediate transfer belt 120 is secondarily transferred to one side of the sheet 102 by the secondary transfer roller 126 and fixed on the sheet 102 through the fixing roller pair 127 as a fixing unit. . Thereafter, the sheet 102 is discharged onto a paper discharge cassette formed in the upper part of the apparatus by a paper discharge roller pair 128.

  Next, another embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This image forming apparatus is a rotary developing type full-color image forming apparatus using a belt intermediate transfer body system. As shown in FIG. 15, a corona charger 168, a rotary developing unit 161, the light emitting device 10 according to the above embodiment, and an intermediate transfer belt 169 are provided around the photosensitive drum 110. Yes.

  The corona charger 168 uniformly charges the outer peripheral surface of the photosensitive drum 110. The light emitting device 10 writes an electrostatic latent image on the charged image forming surface (outer peripheral surface) of the photosensitive drum 110. In the light emitting device 10, a plurality of light emitting elements 32 are arranged along the bus line (main scanning direction) of the photosensitive drum 110. The electrostatic latent image is written by irradiating the photosensitive drum 110 with light from these light emitting elements 32.

  The developing unit 161 is a drum in which four developing units 163Y, 163C, 163M, and 163K are arranged at an angular interval of 90 °, and can rotate counterclockwise about the shaft 161a. The developing units 163Y, 163C, 163M, and 163K supply yellow, cyan, magenta, and black toner to the photosensitive drum 110, respectively, and attach the toner as a developer to the electrostatic latent image, thereby the photosensitive drum 110. A visible image (ie, a visible image) is formed.

  The endless intermediate transfer belt 169 is wound around a driving roller 170a, a driven roller 170b, a primary transfer roller 166, and a tension roller, and is rotated around these rollers in a direction indicated by an arrow. The primary transfer roller 166 transfers the visible image to the intermediate transfer belt 169 that passes between the photosensitive drum 110 and the primary transfer roller 166 by electrostatically attracting the visible image from the photosensitive drum 110.

  Specifically, in the first rotation of the photosensitive drum 110, an electrostatic latent image for a yellow (Y) image is written by the light emitting device 10, and a developed image of the same color is formed by the developing device 163Y. The image is transferred to the transfer belt 169. Further, in the next rotation, the electrostatic latent image for the cyan (C) image is written by the light emitting device 10A, and a developed image of the same color is formed by the developing device 163C, and the intermediate transfer is performed so as to overlap the yellow developed image. Transferred to the belt 169. Then, during the four rotations of the photosensitive drum 110, yellow, cyan, magenta, and black visible images are sequentially superimposed on the intermediate transfer belt 169. As a result, a full-color visible image is formed on the intermediate transfer belt. 169. When images are finally formed on both sides of a sheet as an object on which an image is to be formed, the same color images of the front and back surfaces are transferred to the intermediate transfer belt 169, and then the front and back surfaces are transferred to the intermediate transfer belt 169. A full-color visible image is formed on the intermediate transfer belt 169 in such a manner that the visible image of the next color is transferred.

  The image forming apparatus is provided with a sheet conveyance path 174 through which a sheet passes. The sheets are picked up one by one from the paper feed cassette 178 by the pick-up roller 179, advanced through the sheet transport path 174 by the transport roller, and between the intermediate transfer belt 169 and the secondary transfer roller 171 in contact with the drive roller 170a. Pass through the nip. The secondary transfer roller 171 transfers the developed image to one side of the sheet by electrostatically attracting a full-color developed image from the intermediate transfer belt 169 collectively. The secondary transfer roller 171 can be moved closer to and away from the intermediate transfer belt 169 by a clutch (not shown). The secondary transfer roller 171 is brought into contact with the intermediate transfer belt 169 when a full-color visible image is transferred onto the sheet, and is separated from the secondary transfer roller 171 while the visible image is superimposed on the intermediate transfer belt 169.

  The sheet on which the image has been transferred as described above is conveyed to the fixing device 172 and is passed between the heating roller 172a and the pressure roller 172b of the fixing device 172, whereby the visible image on the sheet is fixed. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. In the case of double-sided printing, after most of the sheet passes through the paper discharge roller pair 176, the paper discharge roller pair 176 is rotated in the reverse direction and introduced into the double-sided printing conveyance path 175 as indicated by an arrow G. The Then, the visible image is transferred to the other surface of the sheet by the secondary transfer roller 171, the fixing process is performed again by the fixing device 172, and then the sheet is discharged by the discharge roller pair 176.

  Since the image forming apparatus illustrated in FIGS. 14 and 15 uses a light source (exposure means) employing an OLED element as the light emitting element 20, the apparatus is made smaller than when a laser scanning optical system is used. . Note that the light-emitting device 10 of the present invention can also be employed in electrophotographic image forming apparatuses other than those exemplified above. For example, the light emitting device according to the present invention is also applied to an image forming apparatus that directly transfers a visible image from a photosensitive drum to a sheet without using an intermediate transfer belt, and an image forming apparatus that forms a monochrome image. 10 can be applied.

  The use of the light emitting device according to the present invention is not limited to exposure of a photoreceptor. For example, the light emitting device of the present invention is employed in an image reading device such as a scanner as a line type optical head (illumination device) that irradiates a reading target such as an original with light. As this type of image reading apparatus, there is a scanner, a copying machine or a reading part of a facsimile, a barcode reader, or a two-dimensional image code reader for reading a two-dimensional image code such as a QR code (registered trademark). In addition, a light emitting device in which a plurality of light emitting elements are arranged in a plane is also used as a backlight unit disposed on the back side of the liquid crystal panel. A light-emitting device in which a plurality of light-emitting elements are arranged in a matrix is employed as a display device for various electronic devices.

1 is a perspective view illustrating a partial configuration of an image forming apparatus according to a first embodiment. The figure which shows schematic structure of the light-emitting device which concerns on 1st Embodiment. FIG. 3 is a circuit diagram showing a pixel circuit in the drive circuit according to the first embodiment. The figure which shows the detection correction | amendment LUT which concerns on 1st Embodiment. The figure which shows the detection register which concerns on 1st Embodiment. The figure which shows correction | amendment LUT which concerns on 1st Embodiment. The figure which shows the correction register which concerns on 1st Embodiment. The flowchart which shows the method of the detection control which concerns on 1st Embodiment. The figure which shows schematic structure of the light-emitting device which concerns on 2nd Embodiment. The flowchart which shows the method of the detection control which concerns on 2nd Embodiment. The figure which shows the detection correction | amendment LUT which concerns on 3rd Embodiment. The figure which shows the mode of the production | generation of the detection correction | amendment LUT by a calculation in 3rd Embodiment. FIG. 10 is a diagram illustrating a state in which a detection correction LUT corresponding to an arbitrary temperature by calculation is generated in the third embodiment, where (a) is one and (b) is two reference detection correction LUTs. FIG. 11 is a perspective view showing a specific example (image forming apparatus) of an electronic apparatus according to the invention. FIG. 11 is a perspective view showing a specific example (image forming apparatus) of an electronic apparatus according to the invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Light-emitting device, 100 ... Optical head, 104 ... TFT control circuit, 105 ... Light receiving sensor, 106 ... OLED element, 107 ... Drive circuit, 108 ... Pixel circuit, 200 ... Control circuit, 201 ... Correction register, 202 ... Correction LUT , 203 ... detection correction register, 204 ... detection correction LUT, 300 ... driver, 400 ... temperature sensor, 500 ... EEPROM, 600 ... A / D converter, 700 ... print counter.

Claims (13)

A light emitting device driving method comprising: a light emitting element; and a unit circuit provided corresponding to the light emitting element, wherein the unit circuit drives the light emitting element according to light emission control data generated based on image data. Because
The light emitting device has a temperature sensor and a light receiving sensor,
A temperature detecting step of detecting the temperature of the light emitting device by the temperature sensor;
A light detecting step of detecting light from the light emitting element by the light receiving sensor;
A control step of generating the light emission control data by correcting the image data according to the temperature of the light emitting device detected by the temperature sensor and the detected value of the light detected by the light receiving sensor;
A method for driving a light emitting device, comprising: A driving method of a light emitting device according to claim 1,
The control step converts the detected value into an effective value, and generates the light emission control data using the converted effective value as the detected value. A method of driving a light emitting device according to claim 1 or 2,
The control step generates the light emission control data by correcting the image data according to the detection value so that a correction characteristic at the time of generating the light emission control data becomes nonlinear. Device driving method. A driving method of a light emitting device according to any one of claims 1 to 3,
The light emitting device further includes a condensing lens array that condenses the light of the light emitting element,
The method of driving a light emitting device, wherein the control step corrects the image data in accordance with a positional relationship between the light emitting element and the condensing lens array. A driving method of a light emitting device according to any one of claims 1 to 4,
The light detection step is a step of detecting light from the light emitting elements by a plurality of the light receiving sensors,
The method of driving a light-emitting device, wherein the control step corrects the image data in accordance with each detected value of the plurality of light receiving sensors. A driving method of a light emitting device according to any one of claims 1 to 5,
The control step corrects the image data using a conversion table that defines a correction value for correcting the image data corresponding to the detected temperature and the detected value of the light. Driving method. A driving method of a light emitting device according to claim 6,
The method for driving a light-emitting device, wherein the correction value of the conversion table is a value obtained by performing a predetermined calculation process from a correction value determined for at least one reference temperature. A driving method of a light emitting device according to any one of claims 1 to 7,
The temperature detecting step includes a step of detecting whether or not the temperature of the light emitting device is a specified temperature,
The light detecting step detects the light from the light emitting element after the temperature detecting step detects that the temperature of the light emitting device is a specified temperature. A driving method of a light emitting device according to claim 8,
The light-detecting step detects light from the light-emitting element at a plurality of the specified temperatures. A method of driving a light emitting device according to any one of claims 1 to 9,
The image data is either on data that causes the light emitting element to emit light or off data that does not cause the light emitting element to emit light,
When the image data is the on data, the control step generates the light emission control data by correcting the image data, and when the image data is the off data, the light emission without correcting the image data. A method for driving a light emitting device, characterized by generating control data. A method of driving a light emitting device according to any one of claims 1 to 10,
The light emitting device further includes a counter for obtaining data for calculating the number of times of light emission of the light emitting element,
The light detecting step detects the light from the light emitting element after calculating that the number of times of light emission has reached a predetermined number from the acquired data. A light-emitting device, and a unit circuit that drives the light-emitting element to emit light, the unit circuit being a light-emitting device that drives the light-emitting element to emit light according to light-emission control data generated based on image data,
A temperature sensor for detecting the temperature of the light emitting device;
A light receiving sensor for detecting light from the light emitting element;
A controller that corrects the image data and generates the light emission control data according to the temperature of the light emitting device detected by the temperature sensor and the detected value of the light detected by the light receiving sensor;
A light emitting device comprising:   An electronic apparatus comprising the light emitting device according to claim 12.

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