Exposure device, LED head, and image formation device

Abstract

To detect temperature of a light-emitting element array more accurately.SOLUTION: An exposure device includes: an LED array; an LED driving driver circuit 127 for driving the LED array; a temperature sensor 129 for outputting a voltage in accordance with the temperature of the LED array; and a temperature detection circuit 130 for detecting temperature of the LED array from the voltage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an exposure device, an LED head, and an image forming apparatus. [Background technology]

[0002] An LED array, which is an array of many LEDs (Light-Emitting Diodes), is a light-emitting device used as an optical print head for electrophotography printing. In an LED array head, a large number of bonding pads for wire bonding are required to connect the LED array to the driving circuit.

[0003] In contrast, for example, as described in Patent Document 1, by forming the LED array and the driving circuit integrally, it is possible to eliminate the need for these bonding pads, and in this case, the number of wires can also be reduced.

[0004] Currently, the drive circuit and the LED array are integrated as follows. First, a semiconductor thin film having a light emitting layer made of GaAs, AlGaAs, InGaP or the like is formed by epitaxial growth on a GaAs substrate. The semiconductor thin film is lifted off from the GaAs substrate by chemical etching or the like, and is then attached to a dissimilar substrate by intermolecular bonding of Si, etc. A drive circuit is formed on the dissimilar substrate, and by connecting the drive circuit with an LED array formed by processing the semiconductor thin film via wiring, an LED array chip that integrates the LED array and drive circuit can be formed.

[0005] This technology eliminates the need to mount the LED array and the driving circuit on a COB (Chip On Board) substrate by die bonding. It also eliminates the need to connect the LED array and the driving circuit with wires, and eliminates the need for wire bonding pads on each, making it possible to miniaturize the LED array chip.

[0006] Furthermore, by replacing the LED array with a light-emitting thyristor array having a switching function, the drive circuit can be simplified and a smaller LED array chip can be formed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2011-018837 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in conventional technology, in order to measure the temperature of an LED head consisting of an LED array, it is necessary to place a temperature sensor such as a thermistor and its control circuit on the head substrate, which is the substrate on which the LED head is formed.Since the temperature sensor such as a thermistor must be formed separately from the head substrate and placed, it is far away from the heat generating point, making it difficult to detect the temperature accurately.

[0009] Therefore, one or more aspects of the present disclosure aim to make it possible to detect the temperature of a light-emitting element array more accurately. [Means for solving the problem]

[0010] An exposure apparatus according to one aspect of the present disclosure is characterized in that it comprises a light-emitting element array, an element driving circuit that drives the light-emitting element array, a semiconductor element for outputting a voltage according to the temperature of the light-emitting element array, and a temperature detection circuit that detects the temperature of the light-emitting element array from the voltage. Effect of the Invention

[0011] According to one or more aspects of the present disclosure, it is possible to detect the temperature of the light-emitting element array more accurately. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus including an exposure device according to a first embodiment. [Diagram 2] 1 is a block diagram illustrating a schematic configuration of a drive circuit according to a first embodiment. [Diagram 3] 1 is a schematic diagram for explaining the arrangement of a temperature sensor in a driver IC. [Figure 4] FIG. 4 is a schematic diagram for explaining connection of a temperature sensor. [Diagram 5] 4 is a graph showing a voltage detected by a temperature sensor and a temperature corresponding to the voltage. [Figure 6] FIG. 2 is a circuit diagram illustrating a configuration of a temperature detection circuit. [Figure 7] 11 is a graph for explaining the relationship between an analog output ATMP and a digital output DTMP indicating a detection result in a temperature detection circuit. [Figure 8] FIG. 11 is a waveform diagram for explaining adjustment of the lighting time of the LED array. [Figure 9] 1A and 1B are schematic diagrams for comparing the embodiment with a conventional example. [Figure 10] 11 is a cross-sectional view of a light-emitting thyristor head in the second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Embodiment 1 FIG. 1 is a cross-sectional view that shows a schematic configuration of an image forming apparatus 100 that includes an exposure device according to the first embodiment. In FIG. 1, capital K indicates an element related to black, capital Y indicates an element related to yellow, capital M indicates an element related to magenta, and capital C indicates an element related to cyan.

[0014] Image forming apparatus 100 is, for example, an electrophotographic color printer. In the image forming apparatus 100, four independent image forming units 101K, 101Y, 101M, and 101C are arranged along the direction from the insertion side to the ejection side of paper as a recording medium.

[0015] The image forming units 101K, 101Y, 101M, and 101C form toner images (developer images) using toner, which is a developer for black, yellow, magenta, and cyan, respectively. In addition to paper, OHP (Overhead Projector) paper, envelopes, copy paper, special paper, etc. can be used as recording media.

[0016] Image forming units 101K, 101Y, 101M, and 101C each include a photosensitive drum 102K, 102Y, 102M, and 102C as an image carrier, a charging roller 103K, 103Y, 103M, and 103C, respectively, a developing roller 104K, 104Y, 104M, and 104C, respectively, and a toner supply roller 105K, 105Y, 105Y, 105M, and 105C, respectively.

[0017] Each of the photoconductor drums 102K, 102Y, 102M, and 102C is an image carrier that carries an image. The charging rollers 103K, 103Y, 103M, and 103C are chargers that uniformly charge the surfaces of the photoconductor drums 102K, 102Y, 102M, and 102C, respectively. The developing rollers 104K, 104Y, 104M, and 104C are developers that deposit toner onto the electrostatic latent images formed on the surfaces of the photoconductor drums 102K, 102Y, 102M, and 102C, respectively, to form toner images of the respective colors that are visible images.

[0018] The toner supply rollers 105K, 105Y, 105M, and 105C are developer supplies that supply toner to the developing rollers 104K, 104Y, 104M, and 104C, respectively. The toner supply rollers 105K, 105Y, 105M, and 105C supply toner from the toner cartridges 106K, 106Y, 106M, and 106C, respectively, to the developing rollers 104K, 104Y, 104M, and 104C, respectively.

[0019] Further, developing blades 107K, 107Y, 107M, and 107C are in pressure contact with the developing rollers 104K, 104Y, 104M, and 104C, respectively. The developing blades 107K, 107Y, 107M, and 107C form a thin layer of toner on the surfaces of the developing rollers 104K, 104Y, 104M, and 104C, respectively.

[0020] The LED heads 108K, 108Y, 108M, and 108C, which are exposure devices, are disposed above the photoconductor drums 102K, 102Y, 102M, and 102C, respectively, at positions facing the photoconductor drums 102K, 102Y, 102M, and 102C, respectively.

[0021] Each of the LED heads 108K, 108Y, 108M, and 108C is equipped with an LED array 109K, 109Y, 109M, and 109C as a light-emitting element array that exposes the surface of each of the photosensitive drums 102K, 102Y, 102M, and 102C according to image data of the corresponding color and forms an electrostatic latent image on each of the photosensitive drums 102K, 102Y, 102M, and 102C.

[0022] The LED arrays 109K, 109Y, 109M, and 109C are disposed so as to face the photoconductor drums 102K, 102Y, 102M, and 102C, respectively. When there is no need to particularly distinguish between the LED arrays 109K, 109Y, 109M, and 109C, any of the LED arrays 109K, 109Y, 109M, and 109C will be referred to as the LED array 109.

[0023] A transfer unit is disposed below the photoconductor drums 102K, 102Y, 102M, and 102C. The transfer unit includes transfer rollers 110K, 110Y, 110M, and 110C as transfer devices, and a conveyor belt 111.

[0024] Transfer rollers 110K, 110Y, 110M, and 110C are disposed opposite photoconductor drums 102K, 102Y, 102M, and 102C, respectively, via conveyor belt 111, and are rollers that charge the paper to a polarity opposite to that of the toner and transfer the toner image of each color onto the paper.

[0025] The conveyor belt 111 is movable in the direction of the arrow d in Fig. 1. The conveyor belt 111 conveys the paper in the direction of the arrow d.

[0026] A paper feed mechanism for feeding paper to a conveyor belt 111 is disposed below the image forming apparatus 100. The paper feed mechanism includes a paper storage cassette 112, a paper color measurement unit 113, a hopping roller 114, and a registration roller 115.

[0027] The paper storage cassette 112 is a medium storage unit that stores paper. The paper color measuring unit 113 is a medium color measuring unit that measures the color of the paper stored in the paper storage cassette 112 .

[0028] The hopping roller 114 picks up a sheet of paper from the paper storage cassette 112 . The registration rollers 115 supply the sheet of paper picked up by the hopping roller 114 to the conveyor belt 111 .

[0029] Furthermore, a fixing unit 116 is provided on the discharge side of the conveyor belt 111. The fixing unit 116 has a heating roller and a backup roller, and fixes the toner transferred onto the paper by applying pressure and heat.

[0030] On the discharge side of the fixing unit 116, a discharge roller, a pinch roller, a paper stacker, and the like (not shown) are provided, and the paper on which the image has been fixed by the fixing unit 116 is discharged to the outside of the image forming apparatus 100.

[0031] The image forming apparatus 100 is also provided with a control circuit 117 as a controller that controls each unit of the image forming apparatus 100. The control circuit 117 can be configured, for example, by an ASIC (Application Specific Integrated Circuit).

[0032] The operation of the image forming apparatus will now be described. First, a sheet of paper is picked up from paper storage cassette 112 by hopping roller 114 and sent to registration roller 115. Next, the sheet is sent from registration roller 115 to conveyor belt 111, and is conveyed to image forming units 101K, 101Y, 101M, and 101C as conveyor belt 111 moves.

[0033] In each of the image forming units 101K, 101Y, 101M, and 101C, the surfaces of the photoconductor drums 102K, 102Y, 102M, and 102C are uniformly charged by the charging rollers 103K, 103Y, 103M, and 103C, respectively. Then, electrostatic latent images are formed on the surfaces of the photoconductor drums 102K, 102Y, 102M, and 102C by exposure to light by the LED heads 108K, 108Y, 108M, and 108C, respectively.

[0034] Toner layers formed by developing rollers 104K, 104Y, 104M, and 104C are electrostatically attached to the electrostatic latent images, and toner images of the corresponding colors are formed on the surfaces of the photoconductor drums 102K, 102Y, 102M, and 102C, respectively.

[0035] The toner images are transferred by transfer rollers 110K, 110Y, 110M, and 110C onto a sheet of paper conveyed by conveyor belt 111. The sheet of paper onto which the color toner images have been transferred is sent to a fixing unit .

[0036] The fixing device 116 fixes the color toner image onto the paper. As a result, a color image is formed on the paper. The paper on which the toner image has been formed is sandwiched between a discharge roller and a pinch roller (not shown) and discharged to a paper stacker. Through this process, a color image is formed on the paper.

[0037] FIG. 2 is a block diagram illustrating a schematic configuration of the driving circuit 120 according to the first embodiment. When the logic circuit power supplies VDD and VSS are applied, the power-on reset circuit 121 resets the memory cells of the memory circuit 125 and the registers of the shift register circuit 123, and sets the mode setting of the test circuit 122 to the initial value.

[0038] VDDH is applied to a constant current source circuit 126 and an LED driver circuit 127 as a power supply for driving an LED. VREF is applied as a reference voltage to the constant current source circuit 126 .

[0039] In addition, the driver circuit 120 determines the direction of data transfer by the LR signal. When the LR signal is Lo, LOADL, DATAL0 to DATAL3, and CLKL become input terminals, and LOADR, DATAR0 to DATAR3, and CLKR become output terminals. On the other hand, when the LR signal is Hi, LOADR, DATAR0 to DATAR3, and CLKR become input terminals, and LOADL, DATAL0 to DATAL3, and CLKL become output terminals.

[0040] The test circuit 122 sets various modes such as a test mode and a temperature detection circuit setting mode.

[0041] The shift register circuit 123 transfers the print data, current correction data, and mode setting data from LOADL, DATAL0 to 3, and CLKL, or LOADR, DATAR0 to 3, and CLKR, to the latch circuit 124 or the memory circuit 125. The print data is transferred to the latch circuit 124, and the current correction data and mode setting data are transferred to the memory circuit 125 and stored in the respective circuits.

[0042] The print data is transferred from the latch circuit 124 to a driver circuit 127 for driving the LEDs. The print data also serves as gradation data for selecting an LED to be driven by the LED driver circuit 127 and controlling the amount of energy, and is output at a timing controlled by the drive timing control circuit 128.

[0043] The current correction data is transferred from the memory circuit 125 to a constant current source circuit 126 and a driver circuit 127 for driving LEDs. The current correction data controls the constant current source circuit 126 and the LED driver circuit 127 to adjust the LED drive current and make the light quantity of the LED array 109 uniform.

[0044] The LED driver circuit 127 functions as an element drive circuit that drives the LED array 109, which is a light-emitting element array.

[0045] Here, the driver circuit 127 for driving LEDs and the LED array 109 are formed as separate semiconductor chips, but by arranging the LED array 109 in the vicinity of the driver circuit 127 for driving LEDs, the temperatures of the driver circuit 127 for driving LEDs and the LED array 109 can be accurately detected.

[0046] When detecting temperature, the test circuit 122 sets the mode of the temperature detection circuit 130 and determines how to handle the values ​​detected by the temperature sensors 129A to 129C.

[0047] The temperature detection circuit 130 detects the temperatures of the LED array 109 at the positions where the temperature sensors 129A to 129C are disposed, based on the voltages corresponding to the temperature sensors 129A to 129C, respectively. The temperature detection circuit 130 has functions of outputting an analog voltage, outputting a digital voltage, setting the hysteresis width of the comparator, providing feedback to the test circuit 122, adjusting the temperature characteristics of the bias circuit, and performing thermal shutdown and other processes. The temperature detection circuit 130 is capable of detecting temperature using a circuit independent of a driver IC that drives the LED.

[0048] The temperature sensors 129A to 129C are semiconductor elements for outputting a voltage according to the temperature of the LED array 109. Temperature sensors 129A to 129C are formed, for example, at three locations inside the driver IC, making it possible to sense the inside of the rectangular driver IC. Moreover, the temperature sensors 129A to 129C are formed by a semiconductor process for forming a semiconductor. In the first embodiment, three temperature sensors 129A to 129C are provided, but the number of temperature sensors is not limited to 3. The number of temperature sensors may be one or more.

[0049] FIG. 3 is a schematic diagram for explaining the arrangement of temperature sensors 129A, 129B, and 129C in driver integrated circuit (IC) 133. As shown in FIG.

[0050] The temperature sensors 129A, 129B, and 129C are formed in a semiconductor process within a driver IC 133 that is integrally formed in a semiconductor process with the LED driver circuit 127 that controls the light emission of the LED array 109. In other words, the temperature sensors 129A, 129B, and 129C are disposed in the same semiconductor chip as the LED driver circuit 127 that controls the light emission of the LED array 109. For this reason, the LED driver circuit 127 and the temperature sensors 129A, 129B, and 129C are included in one semiconductor chip.

[0051] Therefore, the temperature sensors 129A, 129B, and 129C can be disposed in the vicinity of the LED driver circuit 127, which is a heat source, and can measure the correct temperature. Furthermore, the driver IC 133 and the LED array 109 are usually arranged as close as possible to shorten the length of the connecting wires. Therefore, the temperature sensors 129A, 129B, and 129C formed integrally with the LED driver circuit 127 can be arranged close to the LED array 109, which is another heat source, and can therefore measure the correct temperature. It should be noted that a plurality of temperature sensors 129A, 129B, and 129C may be arranged depending on the size or characteristics of the driver IC 133, and the number is not limited to three.

[0052] The temperature sensors 129A, 129B, 129C, the constant current source circuit 126, the temperature detection circuit 130, and the LED driver circuit 127 are arranged in the same semiconductor chip, but here, the LED array 109 is connected to the semiconductor chip by wire bonding or the like.

[0053] FIG. 4 is a schematic diagram for explaining the connections of the temperature sensors 129A, 129B, and 129C. The temperature sensors 129A, 129B, and 129C are semiconductor elements in which the temperature gradient (K) changes linearly in a predetermined region including the temperature to be detected. Here, the temperature sensors 129A, 129B, and 129C may be BJTs (Bipolar Junction Transistors) or diodes formed in the semiconductor process of the driver IC 133.

[0054] As shown in FIG. 4, a voltage generated when a constant current is applied from the constant current source circuit 126 to the temperature sensors 129A, 129B, and 129C is output to a temperature detection circuit 130, and the temperature is detected.

[0055] FIG. 5 is a graph showing the voltages detected by the temperature sensors 129A, 129B, and 129C and the temperatures corresponding to the voltages. The voltage generated when a constant current is applied from the constant current source circuit 126 to the temperature sensors 129A, 129B, and 129C has a temperature gradient K with respect to the reference voltage RV.

[0056] FIG. 6 is a circuit diagram showing a schematic configuration of the temperature detection circuit 130. As shown in FIG. The temperature detection circuit 130 includes multiplexers 140A and 140B that function as selector circuits, a voltage follower 141 using an operational amplifier, a comparator 142 using an operational amplifier, and resistors 143A to 143D.

[0057] The multiplexer 140A receives the sensed voltage V A , V B , V C From the above, one voltage is selected as a target voltage, and the target voltage is output to the voltage follower 141.

[0058] The voltage follower 141 is a circuit that isolates the target voltage so that it does not change due to the influence of the load on the analog output ATMP side from the temperature detection circuit 130. The analog output ATMP output from the voltage follower 141 is input to the comparator 142 via a resistor 143C. Here, the analog output ATMP is an analog output corresponding to the target voltage.

[0059] A voltage corresponding to a set temperature, which is the temperature to be detected, is input to multiplexer 140B by resistors 143A and 143B. Here, if the temperature to be detected is fixed, resistors 143A and 143B may be fixed resistors, but if the temperature to be detected is changed, variable resistors are used as resistors 143A and 143B. Here, it is assumed that variable resistors are used as resistors 143A and 143B. The resistance values ​​of resistors 143A and 143B are set by control circuit 117 in accordance with the detected temperature.

[0060] The multiplexer 140B selects the voltage set by the resistors 143A and 143B, and outputs the selected voltage to the comparator 142 as a reference voltage. From the above, resistors 143A and 143B are variable resistors that change the reference voltage in order to change the set temperature.

[0061] The comparator 142 can detect whether or not the target voltage is within a predetermined range with respect to the reference voltage by comparing the reference voltage with the target voltage corresponding to the analog output ATMP. In other words, the comparator 142 can detect whether or not the temperature corresponding to the target voltage (also referred to as the detection target temperature) is within a predetermined range with respect to the set temperature corresponding to the reference voltage. The comparison result in the comparator 142 is output as the detection result in the temperature detection circuit 130 via a digital output DTMP.

[0062] Here, the temperature hysteresis width corresponding to the predetermined range can be set by resistors 143C and 143D. When the temperature hysteresis width is fixed, the resistors 143C and 143D may be fixed resistors, but when the temperature hysteresis width is changed, variable resistors are used as the resistors 143C and 143D. Here, it is assumed that variable resistors are used as the resistors 143C and 143D. In other words, the resistors 143C and 143D are variable resistors that change the hysteresis width of the comparator 142. Here, the resistance values ​​of the resistors 143C and 143D are set by the test circuit 122.

[0063] FIG. 7 is a graph for explaining the relationship between the analog output ATMP and the digital output DTMP indicating the detection result in the temperature detection circuit 130. As shown in FIG. Here, it is assumed that a voltage corresponding to a set temperature of 100° C. is set as the reference voltage by resistors 143A, 143B and multiplexer 140B. It is also assumed that a temperature hysteresis width of 10° C. is set by resistors 143C and 143D.

[0064] As shown in FIG. 7, the temperature detection circuit 130 outputs High as the digital output DTMP at time T1 when the analog output ATMP reaches the reference voltage corresponding to 100°C. Then, after the detected temperature exceeds 100° C., the detected temperature decreases, and at time T2 when the analog output ATMP reaches a voltage corresponding to 90° C., the temperature detection circuit 130 outputs Low as the digital output DTMP.

[0065] Similarly, at time T3 when the detected temperature reaches 100° C., a High level is output as the digital output DTMP, and at time T4 when the detected temperature drops to 90° C., a Low level is output as the digital output DTMP.

[0066] Here, the analog output ATMP is an analog voltage selected from the detection voltage output from the driver IC 133. For example, the analog output ATMP is fed back to the control circuit 117, and the control circuit 117 can use the analog output ATMP to generate current correction data for controlling the constant current source circuit 126 and the driver circuit 127 for driving the LEDs. It is also possible to correct the reference current of the constant current source circuit 126 based on this analog output ATMP.

[0067] The digital output DTMP is fed back to the control circuit 117 . The control circuit 117 uses the digital output DTMP to adjust the lighting time of the LED array 109 and correct the reduction in the amount of light energy due to heat generation, as shown in Fig. 8. For example, the control circuit 117 identifies a portion that has exceeded a set temperature, and adjusts the gradation value when transferring gradation data indicating the PWM output width, which is the print data for that portion.

[0068] The control circuit 117 can also use the digital output DTMP to perform a thermal shutdown to reset the driver IC 133. For example, when the digital output DTMP becomes High, the control circuit 117 detects abnormal heat generation and transfers print data to turn off all LEDs.

[0069] Furthermore, as a thermal shutdown function, when the digital output DTMP becomes High, it is also possible to send a signal to the power-on reset circuit 121 to perform a reset and return to the state when the power was turned on.

[0070] As described above, according to the first embodiment, it is possible to perform temperature detection within the driver IC 133, making it possible to detect heat generation in the driver IC 133, and since the temperature sensor 129 can be arranged in the vicinity of the heat generating location, it is possible to detect the temperature accurately.

[0071] Also, as shown in FIG. 9(A), conventionally, a temperature sensor 151 is arranged on a head substrate 150 for driving an LED array 109. However, as shown in FIG. 9(B), in this embodiment, such a temperature sensor 151 is not necessary, which is expected to reduce the space required for the head substrate 153 and to reduce costs by reducing the number of components.

[0072] In the embodiment described above, the LED array 109 is connected to the driver IC 133 by bonding or the like, but the first embodiment is not limited to such an example. For example, the LED array 109, the temperature sensors 129A, 129B, 129C, and the driver circuit 127 for driving LEDs can be integrally formed as a driver IC, which is a single semiconductor chip, by a semiconductor process. In such a case, the temperature of the driver circuit 127 for driving LEDs and the driver IC formed as the LED array 109 can be detected accurately.

[0073] Embodiment 2 In embodiment 2, a light-emitting thyristor head is described as an LED head, which is an optical print head used in an image forming apparatus 100, using an LED array chip, which is a chip having a drive circuit 120 including an LED array 109, as described in embodiment 1.

[0074] FIG. 10 is a cross-sectional view of a light-emitting thyristor head 180 according to the second embodiment. As shown in FIG. 10, the light emitting thyristor head 180 includes a base member 181 , a COB substrate 182 , a light emitting thyristor chip 183 , a lens array 184 , a lens holder 185 , and a clamper 186 .

[0075] The base member 181 is a member for fixing the COB board 182, and has an opening 181a on its side for fixing the COB board 182 and the lens holder 185 to the base member 181 using a clamper 186. The base member 181 is injection molded using an organic polymer material or the like.

[0076] The COB substrate 182 is a unit in which a light-emitting thyristor chip 183 is integrated onto a substrate. The light-emitting thyristor chip 183 is formed by forming the LED array 109, which is a light-emitting thyristor array, on an IC. In other words, the light-emitting thyristor chip 183 includes the drive circuit 120 described in the first embodiment.

[0077] Lens array 184 is a group of optical lenses in which a large number of columnar optical lenses are arranged along light-emitting thyristor chips 183 . The lens holder 185 is a part that holds the lens array 184 at a predetermined position on the base member 181 . The clamper 186 is a spring member that clamps each component part integrally through an opening 181 a provided in the base member 181 .

[0078] As described above, the light-emitting thyristor head 180 serving as the LED head in the second embodiment can incorporate a temperature sensor in the IC by using the drive circuit 120 described in the first embodiment.

[0079] Although the first embodiment described above uses a thyristor LED, the first embodiment is not limited to this example. For example, the first embodiment may use an LED array with only an anode and a cathode without using a gate. [Explanation of symbols]

[0080] 100 image forming apparatus, 108 LED head, 109 LED array, 117 control circuit, 127 LED driver circuit, 129 temperature sensor, 130 temperature detection circuit, 140 multiplexer, 141 voltage follower, 142 comparator, 143 resistor.

Claims

1. A light-emitting element array; an element driving circuit that drives the light-emitting element array; a semiconductor element for outputting a voltage according to a temperature of the light-emitting element array; a temperature detection circuit that detects the temperature of the light-emitting element array from the voltage. An exposure apparatus comprising:

2. The element driving circuit, the semiconductor element, and the temperature detection circuit are included in a semiconductor chip that is integrally formed by a semiconductor process.

2. The exposure apparatus according to claim 1 .

3. The light emitting element array is also included in the semiconductor chip that is integrally formed by a semiconductor process.

3. The exposure apparatus according to claim 2 .

4. the semiconductor chip includes a plurality of semiconductor elements including the semiconductor element, The temperature detection circuit includes: a multiplexer for selecting one voltage from a plurality of voltages corresponding to the plurality of semiconductor elements; a comparator for comparing the one voltage with a reference voltage which is a voltage corresponding to a set temperature which is a temperature detected by the temperature detection circuit.

3. The exposure apparatus according to claim 2 .

5. the semiconductor chip includes a plurality of semiconductor elements including the semiconductor element, The temperature detection circuit includes: a multiplexer for selecting one voltage from a plurality of voltages corresponding to the plurality of semiconductor elements; a comparator for comparing the one voltage with a reference voltage which is a voltage corresponding to a set temperature which is a temperature detected by the temperature detection circuit.

4. The exposure apparatus according to claim 3,

6. The temperature detection circuit includes a variable resistor that changes the reference voltage in order to change the set temperature.

5. The exposure apparatus according to claim 4,

7. The temperature detection circuit includes a variable resistor that changes the reference voltage in order to change the set temperature.

6. The exposure apparatus according to claim 5,

8. The temperature detection circuit includes a variable resistor for changing the hysteresis width of the comparator.

5. The exposure apparatus according to claim 4,

9. The temperature detection circuit includes a variable resistor for changing the hysteresis width of the comparator.

6. The exposure apparatus according to claim 5,

10. The temperature detection circuit further includes a variable resistor for changing a hysteresis width of the comparator.

7. The exposure apparatus according to claim 6,

11. The temperature detection circuit further includes a variable resistor for changing a hysteresis width of the comparator.

8. The exposure apparatus according to claim 7,

12. The exposure apparatus according to any one of claims 1 to 11 is provided. The LED head is characterized by:

13. The exposure apparatus according to any one of claims 1 to 11 is provided. An image forming apparatus comprising:

Images