JP2010214681A - Method for regulating light quantity of exposure head and method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for regulating the light quantity of an exposure head having a light emitting element of which the light quantity regulation time period is reduced, and to provide a method for forming an image. <P>SOLUTION: This method for regulating the light quantity of an exposure head includes a first imaging optical system, a second imaging optical system arranged in a first direction (X direction) of the first imaging optical system, a third imaging optical system arranged on a second direction side (Y direction) perpendicular to the first direction, and a detection means 11 that is provided at a position the distance of which from the third imaging optical system is smaller than that from the first imaging optical system so as to detect a light quantity of each light emitting element. The light quantity of the light emitting element imaged by the first imaging optical system is first detected, and next the light quantity of the light emitting element imaged by the third imaging optical system is detected. By comparing the light quantity of the initial value of each light emitting element with the detected quantity of the light emitting element, the emission light quantity of each light emitting element is regulated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure head light amount adjustment method and an image forming method in which a light amount adjustment time of a light emitting element is shortened.

  As an optical printer using an exposure head, there are an electrophotographic printer using an LED head and an electrophotographic printer using a liquid crystal line head. As the printer (image forming apparatus), a plurality of light emitting elements such as LEDs are arranged in the main scanning direction (first direction), and light emitted from the light emitting elements is imaged by a lens of an image forming optical system to be a photosensitive member. An exposure head for forming a latent image spot on a (latent image carrier) is known.

  In these printers, a plurality of imaging optical systems may be arranged in the first direction and a second direction (sub-scanning direction) orthogonal to the first direction. A lens with a negative optical magnification (an inverted imaging optical system) or a lens with a positive optical magnification (an upright imaging optical system) may be used as such an imaging optical system lens. is there. Patent Document 1 describes an example of an image forming apparatus using a lens (inverted imaging optical system) having a negative optical magnification.

  In a light emitting element such as an LED or an organic EL element, the amount of light decreases with the lapse of usage time, causing exposure unevenness of the exposure head. For this reason, the control which adjusts light quantity deterioration is needed. In Patent Document 2, as control for adjusting such light amount deterioration, first, the light amount value of each element is measured at the time of factory shipment, and is stored in a memory. Next, at the time of control to adjust the amount of light when using the product, the light intensity is measured using a sensor provided on the head substrate, and compared with the amount of light at the time of shipment. A method for adjusting the amount of light that eliminates the uneven exposure has been proposed.

JP 2008-173889 A JP 2004-82330 A

18 and 19 are a circuit diagram and a characteristic diagram showing the light amount detection of the light emitting element described in Patent Document 2. FIG. FIG. 18 shows a light quantity sensor and a light quantity detection circuit using photocurrent / voltage conversion. An operational amplifier (differential amplifier) Op, a capacitor Cf, and a resistor Rf are connected to a light receiving element (photodiode) Pd as a light amount sensor that receives output light of the light emitting element. The amount of light is detected by a voltage signal obtained at the output terminal Vout. As shown in FIG. 18, in order to prevent the operational amplifier Op from oscillating and malfunctioning, the signal band is limited using the capacitor Cf.

FIG. 19 is a characteristic diagram showing the relationship between the output voltage value of the light amount detection circuit and time. As described with reference to FIG. 18, the time until the output voltage converges within the error range (to a constant value Z) because the band of the light amount detection circuit is limited by the capacitor Cf or because of the slew rate of the light amount detection circuit itself. Time to reach) Ta, that is, a settling time exists. Tb after the lapse of Ta indicates a time for detecting the light amount of the light emitting element.

Thus, since the output value during the settling time Ta causes an error, it is necessary not to capture the detection result or to ignore it. In an exposure head in which a large number of light emitting elements are arranged on a substrate, it takes time to detect the amount of light of all the light emitting elements, and there is a demand for reducing the detection time as much as possible. For example, it is conceivable to consider the light quantity detection order of the light emitting elements, but Patent Document 2 does not mention the head pixel detection order (light quantity output value detection order of the light emitting elements). Therefore, in order to detect the light quantity of the next light emitting element after obtaining the output value of the light quantity detection of a certain light emitting element, there is a settling time until the output value of the next light emitting element rises to the constant value Z. For this reason, in order to detect the light quantity of all the light emitting elements, there existed a problem that settling time was accumulated and light quantity detection time became long.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to adjust the light amount of an exposure head by shortening the light amount adjustment time of the light emitting element in the exposure head in which a plurality of light emitting elements are arranged. And providing an image forming method.

The light amount adjustment method of the exposure head of the present invention that achieves the above object is
A first imaging optical system;
A second imaging optical system disposed in a first direction of the first imaging optical system;
A third imaging optical system disposed on a second direction side orthogonal to the first direction;
A means for detecting the amount of emitted light of each light emitting element provided at a position where the distance from the third imaging optical system is smaller than the distance from the first imaging optical system;
Have
Detecting a light emission amount of a light emitting element imaged by the first imaging optical system;
Detecting a light emission amount of a light emitting element imaged by the third imaging optical system;
Comparing the initial light emission amount of each light emitting element with the detected light emission amount of each light emitting element;
And a step of adjusting a light emission amount of each light emitting element based on the comparison result.

Further, the light amount adjustment method of the exposure head of the present invention,
The step of detecting the amount of emitted light of the light emitting element imaged by the first imaging optical system is performed prior to the step of detecting the amount of emitted light of the light emitting element imaged by the third imaging optical system. Do.

Further, the light amount adjustment method of the exposure head of the present invention,
The step of detecting the emitted light amount of the light emitting element imaged by the first imaging optical system is performed after the step of detecting the emitted light amount of the light emitting element imaged by the third imaging optical system. .

In the exposure head light amount adjustment method of the present invention, the light emitting element array formed by the plurality of light emitting elements arranged in the first direction corresponds to the image forming optical system in the second direction. Are arranged in multiple rows,
The first imaging optical system first detects the light emission amount of the light emitting element in the light emitting element row having a large distance from the light emission amount detecting means, and the light emission amount of the light emitting element in the light emitting element row having the small distance. A step of detecting

  In the exposure head light amount adjustment method of the present invention, the light emission amount of each light emitting element corresponding to the second imaging optical system after detection of the light emission amount of each light emitting element corresponding to the first imaging optical system is provided. A step of detecting.

  In the exposure head light amount adjustment method of the present invention, the distance from the light emission amount detection means is large in each of the light emitting element arrays corresponding to the first imaging optical system and the second imaging optical system. A step of detecting the light emission amount of the light emitting element in the light emitting element row first and detecting the light emission amount of the light emitting element in the light emitting element row having the small distance later.

  In the exposure head light amount adjusting method of the present invention, the imaging optical system has a negative optical magnification.

The image forming method of the present invention includes a latent image carrier, a first imaging optical system, a second imaging optical system disposed in a first direction of the first imaging optical system, A distance from the third imaging optical system disposed on the second direction side orthogonal to the first direction and the third imaging optical system is a distance from the first imaging optical system. And means for detecting the amount of emitted light of each light emitting element provided at a position smaller than,
Detecting a light emission amount of a light emitting element imaged by the first imaging optical system;
Detecting a light emission amount of a light emitting element imaged by the third imaging optical system;
A step of comparing the initial light emission amount of each light emitting element with the detected light emission amount of the light emitting element;
Adjusting the amount of emitted light of each light emitting element based on the comparison result;
And a step of forming a latent image on the latent image carrier by the output light of the light emitting element after adjusting the amount of emitted light.

It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is a characteristic view which shows embodiment of this invention. It is a characteristic view which shows the reference example of this invention. It is a characteristic view which shows embodiment of this invention. It is a block diagram which shows embodiment of this invention. It is a flowchart which shows embodiment of this invention. 1 is a schematic cross-sectional view showing an overall configuration of an embodiment of an image forming apparatus using an electrophotographic process of the present invention. It is explanatory drawing which shows the premise technique of this invention. It is explanatory drawing which shows the premise technique of this invention. It is explanatory drawing which shows the premise technique of this invention. It is a circuit diagram which shows the premise technique of this invention. It is a characteristic view which shows the prior art of this invention.

  An embodiment of the present invention will be described. 15-17 is explanatory drawing which shows the premise technique of this invention. FIG. 15 shows an arrangement relationship between a lens (ML) having a negative optical magnification and a light emitting element (dot). In FIG. 15, ML4 has two or more light emitting elements 2 arranged in the axial direction (X direction, first direction) of the photoconductor and the rotation direction (Y direction, second direction) of the photoconductor. A latent image is formed on the photoreceptor by the light emitting elements. For the sake of convenience, the light emitting elements 2 are numbered “1 to N”.

The light emitting element row 3a in the first column in the Y direction has “2, 4,... N” light emitting elements arranged from the left side to the right side in the X direction. In the light emitting element row 3b arranged in the second column in the Y direction, 1, 3,. Here, two or more lenses 4 are arranged in the X direction to form a lens array (MLA). In addition, a lens array can be configured by arranging two or more lenses in the X and Y directions.

  FIG. 16 is an explanatory diagram of an exposure head using a lens array having a negative optical magnification. When the number of light emitting elements (number of dots) for forming a one-line latent image in the axial direction of the photosensitive member increases, a lens array that is long in the axial direction of the photosensitive member is required. In such a case, a long exposure head can be formed by connecting a plurality of lens arrays having a certain length. FIG. 16A shows a schematic overall configuration of the long exposure head 10, and 5 n is a lens array of a part of the long exposure head. FIG. 16B is an enlarged view showing 5n of the lens array.

  In FIG. 16B, the exposure head has two or more light emitting elements 2 disposed on the substrate 1. Reference numeral 3 denotes a light emitting element group composed of two or more light emitting elements arranged on one lens 4. In the light emitting element group 3, two or more light emitting elements are arranged in the axial direction X of the photoreceptor and the rotation direction Y of the photoreceptor. Reference numeral 4 denotes a lens, and two or more lenses are arranged in the axial direction (main scanning direction, first direction) X of the photoconductor and the rotation direction (sub-scanning direction, second direction) Y of the photoconductor to constitute a lens array. ing.

  As shown in FIG. 16A, in the case where a plurality of lenses are connected in the axial direction of the photosensitive member, the position of the latent image spot formed on the latent image carrier when the manufacturing and assembly accuracy of the lens array decreases. The image quality may be deteriorated due to the deviation. In addition, variations between the pitches of the connecting portions of the lens arrays and registration displacement (positional displacement) may occur.

  FIG. 17 is an explanatory diagram showing a modification of FIG. In the configuration of FIG. 17, four light emitting element rows 3a to 3d are arranged in the second direction in the lens 4a of the imaging optical system. As described above, the total number of light emitting elements 2 and the number of light emitting element rows in a single lens can be arbitrarily set.

  FIG. 7 is an explanatory view showing a configuration example of an exposure head to which the exposure head light amount adjusting method of the present invention is applied. In FIG. 7, the substrate 1 is provided with a lens 4 of an imaging optical system and light amount detectors 11 to 13. A large number of light emitting elements 2 corresponding to each lens 4 are mounted on the substrate. The lens 4 has a plurality of 4a, 4d,..., 4n arranged in the first direction (X direction, main scanning direction). The lens 4 has a plurality of 4a, 4b, 4c arranged in the second direction (Y direction, sub-scanning direction).

FIG. 8 is an explanatory diagram showing an embodiment of the present invention, and FIG. 9 is a characteristic diagram showing a light amount output value in the configuration of FIG. In FIG. 8, Ea represents the distance from the light quantity detector 11 to the lens 4a, Eb represents the distance from the light quantity detector 11 to the lens 4b, and Ec represents the distance from the light quantity detector 11 to the lens 4b.
A large number of light emitting elements 2 are arranged in each lens in the first direction (X direction) and the second direction (Y direction). For example, in the lens 4c, the light emitting element rows 3a to 3d are arranged in the second direction. Light emitting elements A, B, C... N are provided in the first direction of the light emitting element array 3a. In this configuration, four light emitting element rows are arranged in the second direction (Y direction).

FIG. 9A shows the configuration of FIG. 8 again, and FIG. 9B is a characteristic diagram of the light amount output value. The characteristic Da in FIG. 9B corresponds to the light quantity of the light emitting element at the distance Ea, the characteristic Db corresponds to the light quantity of the light emitting element at the distance Eb, and the characteristic Dc corresponds to the light quantity of the light emitting element at the distance Ec. In the characteristic Da, the light output value converges to a constant value Za when the time Ka after lighting elapses. In the characteristic Db, the light output value converges to a constant value Zb when the time Kb after lighting elapses. In the characteristic Dc, the light output value converges to a constant value Zc when the time Kc after lighting elapses. As shown in FIG. 9B, the magnitude of the light amount output value of the light emitting element is inversely proportional to the distance from the light amount detector 11. In the present invention, the light quantity detection order of the light emitting elements is determined using the characteristics of the light quantity output value. That is, the light amounts of the light emitting elements having the same distance from the light amount detector are sequentially detected. In this case, the light output values of the respective light emitting elements are substantially constant, and the settling time can be shortened because the fluctuations in the output values are small in sequential detection. If the light quantity detection is performed in such an order, the entire light quantity detection time of the exposure head including a large number of light emitting elements can be shortened.

  As described above, in the detection of the light amount value of the light emitting element, the output value of the light amount detector differs depending on the distance between the light amount detector and the light emitting element, and the output value of the light amount detector differs. When the lens of the imaging optical system is spherical, when the width of the light amount detector is long in the main scanning direction (first direction), the light amount value detected by the light amount detector is the same as that in the main scanning direction. It depends more strongly on the distance in the sub-scanning direction (second direction) than on the distance. Therefore, in the same row of pixels (light emitting elements) in the main scanning direction (first direction) of the lens or in the head arrangement, almost the same output value of the light amount detector can be obtained when detecting the light amount.

  FIG. 10 is a characteristic diagram showing the prerequisite technology of the present invention. The characteristic Du is, for example, the characteristic in the case of detecting the light amount in order in the first direction for the light emitting elements in the same lens 4a in the example of FIG. In this case, the distances from the light quantity detector 11 to the lens 4b are approximately equal for each light emitting element. Further, for example, in the example of FIG. 8, the characteristic Dv is different from that in a different lens such as a light emitting element (second light emitting element) in the lens 4 b following a light emitting element (first light emitting element) in the lens 4 c. It is a characteristic in the case of detecting the light quantity of the light emitting element sequentially. In this case, the distances from the light quantity detector 11 of the first light emitting element and the second light emitting element are different. For this reason, the light amount output value once decreases like the characteristic Dr and then increases like Dv, and the detection time becomes long.

  FIG. 11 is an explanatory diagram showing an embodiment of the present invention. As shown in FIG. 8, it is assumed that light emitting elements A, B, C... N are provided in the first direction of the light emitting element array arranged in the lens 4c. In this example, the output value when the light amounts of the light emitting elements A, B, and C are sequentially detected is indicated by the characteristic Dw. Ga is a timing when the light emitting element A is turned on, Gb is a timing when the light emitting element A is turned off and the light emitting element B is turned on, and Gc is a timing when the light emitting element B is turned off and the light emitting element C is turned on.

  Fa is the timing of starting the acquisition of the light amount detection value of the light emitting element A, and the light amount detection of the light emitting element A is completed at time Tr. Fb is the timing of starting the acquisition of the light amount detection value of the light emitting element B, and the light amount detection of the light emitting element B is completed at time Ts. Tx is the time from the lighting of the light emitting element A to the extinguishing, and Ty is the time from the lighting of the light emitting element B to the extinguishing. As described with reference to FIG. 8, the light emitting elements A, B, C... Are arranged on the same lens, and the distances to the light amount detectors are substantially equal. Therefore, almost the same output value of the light amount detector can be obtained at the time of detecting the light amount. For this reason, even if the discharge time of the capacitor is shortened and the light quantity of the next light emitting element is detected, there is little error. As a result, the settling time is short, and the time from the end of the light amount detection of one light emitting element to the detection of the light amount of the next light emitting element is shortened.

As described with reference to FIG. 11, the first element is turned on, the settling time is waited, the detection value acquisition starts, the detection value acquisition is completed, the first element is turned off, the second element is turned on, and so on. The amount of light will be detected. In the control as in the timing chart of FIG. 11, when each element is sequentially turned on and off repeatedly, the output value of the light quantity detector becomes like the characteristic Dw of the timing chart. That is, by setting the detection order of the elements for detecting the light amount as in the embodiment, the output values of the Nth element and the (N + 1) th element can be set to the same level. As described above, the detected output value from the Nth element to the (N + 1) th element does not substantially change when detecting the amount of light. For this reason, the settling time can be shortened, and as a result, the total detection time of all elements can be shortened.

The ON / OFF response time and control time of the organic EL element (OPH) and the light / current conversion time of the photodiode of the light receiving element are sufficiently short compared with the response speed of the light quantity detection circuit. For this reason, the light amount detection time is substantially determined by the settling time and the detection capture time based on the response time of the light amount detection circuit. Since the output of a detection circuit using an OP amplifier as shown in FIG. 18 or a circuit in which an LPF (low-pass filter) is connected downstream of the light amount detection circuit shows the characteristics of the LPF.
* V = E × [1-exp (-t / CR)]
From the above equation, the settling time from the Nth element output to the (N + 1) th element output can be determined. Here, * V = output voltage and E = input voltage. By determining the settling time optimized for each detection element, the total detection time is shortened.

  1 and 2 are explanatory views showing an embodiment of the present invention. FIG. 2 is a partially enlarged view of the configuration of FIG. 7 and shows the correspondence relationship between the lenses 4 a to 4 f, the light emitting elements disposed therein, and the light amount detector 11. FIG. 1A shows the configuration of FIG. 2 again. Here, the light amounts of the light emitting elements in the lenses 4d to 4f are detected. In this example, the light amount detection of all the light emitting elements in the lens 4d is first performed, and then the light amount detection of all the light emitting elements in the lens 4e is performed. Subsequently, the light amount of all the light emitting elements in the lens 4f is detected.

  FIG. 1B shows the output value of the light amount detection. In this case, the output value of the light quantity detection can be expressed from a characteristic with a low output value to a characteristic with a high output value in the order of 4d, 4e, and 4f. In this example, by first detecting the light amount of all the light emitting elements in the lens 4d having the longest distance from the light amount detector 11, the outputs in the lens 4d are substantially equal. Next, by sequentially detecting the light amounts of all the light emitting elements in the lenses 4e and 4f, the output fluctuation of the light amount detector is suppressed and the settling time is shortened. The light amount detection time as a whole can be shortened by such light amount detection.

  FIG. 3 is an explanatory view showing a detailed example of the light emitting element 2 arranged in the single lens 4. In FIG. 3, four light emitting element rows 3 a to 3 d are provided in the lens 4 in the second direction (Y direction). Light emitting elements 1 to N are mounted on the light emitting element array 3a. Hereinafter, the light emitting elements N + 1 to M are mounted on the light emitting element array 3b, the light emitting elements M + 1 to L are mounted on the light emitting element array 3c, and the light emitting elements L + 1 to P are mounted on the light emitting element array 3d. In this example, for example, light amount detection of the light emitting elements in the light emitting element row 3a is performed, and then light amount detection of the light emitting elements in the light emitting element rows 3b, 3c, and 3d is sequentially performed. Also in this case, the light amount of the light emitting elements included in the light emitting element rows having the substantially same distance from the light amount detector is detected.

  FIG. 4 is an explanatory view showing a different embodiment of the present invention. In the example of FIG. 4A, it is assumed that four rows of light emitting element rows 3a to 3d are provided in the second direction in the lens 4d as described in FIG. In this example, the distance from the light quantity detector 11 increases in the order of the light emitting element arrays 3a, 3b, 3c, and 3d. For this reason, the output fluctuation is suppressed by detecting the light quantity detection every 3a, 3b, 3c, and 3d (in no particular order). Also in this case, as described with reference to FIG. 1B, the detection order takes into account the settling time characteristics, and the light amount detection time can be shortened.

  FIG. 5 is an explanatory view showing a different embodiment of the present invention. In the example of FIG. 5, it is assumed that the lens, the light emitting element, and the light quantity detectors 11 and 12 are arranged as described in FIG. That is, the lenses 4a, 4d,..., 4n are arranged in the first direction (X direction) on the upper side in the figure in the second direction (Y direction). In addition, lenses 4b, 4e,..., 4n + 1 are arranged on the middle side in the figure in the second direction (Y direction). Furthermore, lenses 4c, 4f,..., 4n + 2 are arranged on the lower side in the figure in the second direction (Y direction).

In the example of FIG. 5, first, the light amounts of all the light emitting elements in the lenses 4a, 4d,..., 4n arranged in the first direction on the upper side in the drawing in the second direction are detected. That is, for the lenses 4a, 4d,..., 4n having the longest distance from the light amount detectors 11, 12, the light amounts of all the light emitting elements in the lenses are sequentially detected in the direction of arrow R in the first direction. Next, for the lenses 4b, 4e,..., 4n + 1 on the middle side in the figure, the light amounts of all the light emitting elements in the lens are detected in the direction of arrow S in the first direction. Finally, with respect to the lower lenses 4c, 4f,..., 4n + 2, the light amounts of all the light emitting elements in the lens are detected in the direction of arrow T in the first direction. For this reason, the detection order takes into account the characteristics of the settling time, and the time for detecting the amount of light can be shortened.

  FIG. 6 is an explanatory view showing a different embodiment of the present invention. In the example of FIG. 6, the light amount detection of the light emitting elements in the lenses 4c, 4f arranged in the first direction is performed by firstly detecting the light emitting elements in the light emitting element rows 3a, 3f in the lenses 4c, 4f,. Carry out in the direction of the arrow u. Next, the light emitting elements in the light emitting element rows 3b and 3f are implemented in the direction of the arrow v. Subsequently, the light emitting elements of the light emitting element arrays 3c and 3g are implemented in the direction of the arrow w. Finally, the light emitting elements of the light emitting element rows 3d and 3h are implemented in the z direction as viewed from the arrow. For this reason, the detection order takes into account the characteristics of the settling time, and the time for detecting the amount of light can be shortened.

  FIG. 12 is a block diagram showing an embodiment of the present invention. In FIG. 12, the light emission control module 71 is provided with a control circuit 72, a memory 73, a light amount detection circuit 74, a light amount sensor 75, and a drive circuit 76 for the light emitting element 2. The head controller 70 transmits a control signal such as a drive command for the light emitting element 2 to the control circuit 72. The memory 73 stores the light quantity (initial value) at the time of factory shipment of all the light emitting elements 2 disposed in the exposure head. The control circuit 72 compares the light amount of each light emitting element when the exposure head is used detected by the light amount sensor 75 and the detection circuit 74 with the light amount of each light emitting element of the initial value stored in the memory 73, and each light emitting element. A control signal for adjusting the light quantity of 2 is formed. The control signal after the light amount adjustment is sent to the drive circuit 76 to control the driving of each light emitting element.

FIG. 13 is a flowchart showing an embodiment of the present invention. In the configuration described with reference to FIG. 1, the processing procedure of FIG. 13 will be described using an example in which a plurality of light emitting elements 1 to N are arranged in a single lens M and a plurality of lenses M are arranged in the second direction.
S1: Start of light quantity measurement.
S2: M is initialized to 1.
S3: N is initialized to 1.
S4: The light emitting element 1 in the lens M is turned on.
S5: Settling time period, waiting for light amount detection.
S6: Start of taking in the light amount detection.
S7: Completion of light amount detection.
S8: The light emitting element 1 is turned off.
S9: It is determined whether or not the light amount detection of all the light emitting elements in the lens M is completed.
S10: If the determination result in S9 is NO, the number of the light emitting element is incremented by 1 to 2, and the processing from S4 onward is repeated.
S11: If the determination result in S9 is YES, it is determined whether or not the light amount detection of the light emitting elements in all the lenses has been completed.
S12: If the determination result in S11 is NO, the lens number is incremented by 1 to 2, and the processing from S2 is repeated.
S13: If the determination result in S11 is YES, the light quantity measurement is terminated.

  In an embodiment of the present invention, a tandem color printer that exposes four photosensitive members with four exposure heads, simultaneously forms four color images, and transfers them to one endless intermediate transfer belt (intermediate transfer medium). The target is an exposure head used in (image forming apparatus).

FIG. 14 is a vertical side view showing an example of a tandem image forming apparatus using an organic EL element as a light emitting element. This image forming apparatus includes four exposure heads 101K, 101C, 101M, and 101Y having the same configuration and corresponding four photosensitive members (latent image carriers) 41K, 41C, 41M, and 41Y having the same configuration. They are arranged at the exposure positions.

  As shown in FIG. 14, this image forming apparatus is provided with a driving roller 51, a driven roller 52, and a tension roller 53, and an intermediate transfer belt that is circulated and driven in the direction indicated by the arrow (counterclockwise) by the tension roller 53. 50. Photosensitive members 41K, 41C, 41M, and 41Y are arranged at predetermined intervals with respect to the intermediate transfer belt 50. K, C, M, and Y added after the reference sign mean black, cyan, magenta, and yellow, respectively. The photoconductors 41 </ b> K to 41 </ b> Y are driven to rotate in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50. Around each photoconductor 41 (K, C, M, Y), a charging unit 42 (K, C, M, Y) and an exposure head 101 (K, C, M, Y) are provided.

  Further, a developing device 44 (K, C, M, Y) that applies a toner as a developer to the electrostatic latent image formed by the exposure head 101 (K, C, M, Y) to form a visible image; The primary transfer roller 45 (K, C, M, Y) and the cleaning device 46 (K, C, M, Y) are included. The emission energy peak wavelength of each line head 101 (K, C, M, Y) and the sensitivity peak wavelength of the photoconductor 41 (K, C, M, Y) are set to substantially coincide.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). The toner image, which is sequentially primary transferred onto the transfer belt 50 and sequentially superposed on the intermediate transfer belt 50 to become a full color, is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 66, and serves as a fixing unit. The toner is fixed on the recording medium P by passing through the fixing roller pair 61, and is discharged onto a paper discharge tray 68 formed in the upper part of the apparatus by a paper discharge roller pair 62.

  63 is a paper feed cassette in which a large number of recording media P are stacked and held, 64 is a pickup roller for feeding the recording media P from the paper feed cassette 63 one by one, and 67 is a secondary transfer portion of the secondary transfer roller 66. A pair of gate rollers for defining the supply timing of the recording medium P to the medium, 66 is a secondary transfer roller as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50, and 69 is an intermediate after the secondary transfer. This is a cleaning blade that removes toner remaining on the surface of the transfer belt 50.

  As described above, the light amount adjustment method and the image forming method of the exposure head in which the light amount adjustment time of the light emitting element of the present invention is shortened have been described based on the principle and the examples, but the present invention is not limited to these examples and various Deformation is possible.

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Light emitting element, 3 ... Light emitting element group (spot group), 3a-3h ... Light emitting element row | line | column, 4 ... Lens, 5n ... Lens array, 11-13 ... Light quantity detector, 41 (Y, M, C, K) ... Photoconductor, 50 ... Intermediate transfer belt, 70 ... Head controller, 71 ... Light emission control module, 72 ... Control circuit 73 ... Memory 74 ... Light quantity detection circuit 75 ... Light quantity sensor 76 ... Drive circuit 101 (Y, M, C, K) ... Exposure head, J ... -Light receiving element, Cf ... capacitor, Op ... operational amplifier (differential amplifier)

Claims (8)

A first imaging optical system;
A second imaging optical system disposed in a first direction of the first imaging optical system;
A third imaging optical system disposed on a second direction side orthogonal to the first direction;
A means for detecting the amount of emitted light of each light emitting element provided at a position where the distance from the third imaging optical system is smaller than the distance from the first imaging optical system;
Have
Detecting a light emission amount of a light emitting element imaged by the first imaging optical system;
Detecting a light emission amount of a light emitting element imaged by the third imaging optical system;
Comparing the initial light emission amount of each light emitting element with the detected light emission amount of each light emitting element;
Adjusting the amount of light emitted from each of the light emitting elements based on the comparison result. The step of detecting the amount of emitted light of the light emitting element imaged by the first imaging optical system is performed prior to the step of detecting the amount of emitted light of the light emitting element imaged by the third imaging optical system. The exposure head light amount adjusting method according to claim 1 to be performed. The step of detecting the emitted light amount of the light emitting element imaged by the first imaging optical system is performed after the step of detecting the emitted light amount of the light emitting element imaged by the third imaging optical system. The method for adjusting the light amount of an exposure head according to claim 1. Corresponding to a single imaging optical system in each imaging optical system, a plurality of light emitting element arrays formed by the light emitting elements arranged in the first direction are arranged in the second direction. Has been
In the first imaging optical system, the light emission amount of the light emitting element of the light emitting element array having a large distance from the light emission amount detection unit is detected first, and the light emission element having a small distance from the light emission amount detection unit 2. The exposure head light amount adjustment method according to claim 1, further comprising a step of detecting the light emission amount of the light emitting elements in the row later. 2. The exposure according to claim 1, further comprising: detecting a light emission amount of each light emitting element corresponding to the second imaging optical system after detecting a light emission amount of each light emitting element corresponding to the first imaging optical system. How to adjust the light intensity of the head. In each of the light emitting element arrays corresponding to the first image forming optical system and the second image forming optical system, the light emission amount of the light emitting elements in the light emitting element array having a large distance from the light emission element detection unit is first determined. The exposure head light amount adjusting method according to claim 1, further comprising a step of detecting and detecting a light emission amount of a light emitting element in a light emitting element array having a small distance later. 7. The exposure head light amount adjusting method according to claim 1, wherein the imaging optical system has a negative optical magnification. A latent image carrier, a first imaging optical system, a second imaging optical system disposed in a first direction of the first imaging optical system, and orthogonal to the first direction A third imaging optical system disposed on the second direction side, and the distance from the third imaging optical system provided at a position smaller than the distance from the first imaging optical system; A means for detecting the amount of light emitted from each light emitting element,
Detecting the amount of light emitted from the light emitting element formed on the latent image carrier by the first imaging optical system;
Detecting the amount of light emitted from the light emitting element formed on the latent image carrier by the third imaging optical system;
Comparing the initial light emission amount of each light emitting element with the detected light emission amount of each light emitting element;
Adjusting the amount of emitted light of each light emitting element based on the comparison result;
And a step of forming a latent image on the latent image carrier with the output light of the light emitting element after adjusting the amount of emitted light.

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