JP4921226B2 - Light quantity control apparatus, exposure apparatus, image forming apparatus, and light quantity control method - Google Patents

Description

  The present invention relates to a technique for controlling each light quantity of a plurality of light beams and an application technique thereof.

  Conventionally, an image forming apparatus and an image reading apparatus using a plurality of light emitting elements have been proposed. In these apparatuses, control is performed to keep the light quantity of the beam output from each light emitting element constant. According to Patent Document 1, an image reading device is described that causes a plurality of LEDs to emit light in order, determines a light amount correction value for each LED, and controls the light amount of each LED.

According to Patent Document 2, a method is described in which the light quantity of each LED is made uniform by applying any one of three correction data stored in a ROM in advance to a plurality of LEDs used in a printer.
JP 63-292863 A JP 63-142392 A

  Here, a case where a surface emitting laser is applied as a light source of the image forming apparatus is considered. Of the multiple light emitting points provided in the surface emitting laser, only one light emitting point selected at random is emitted to obtain data necessary for control, and other light emitting points are obtained based on this data. A method for executing light amount control is conceivable. This method has an advantage that the control time required for the light amount control can be shortened because it is not necessary to execute light emission, data acquisition and light amount control for each light emitting point.

  However, since this control method monitors only the light amount of one reference beam, the accuracy of the light amount control for other beams may vary. In particular, in the surface emitting laser, since there is always a variation in the current-light quantity characteristic for each light emitting point, there is a concern that the control accuracy may also vary.

  FIG. 10 is a graph showing an example of current-light quantity characteristics in the surface emitting laser. Reference numeral 1001 denotes the characteristic of the first light emitting point. Reference numeral 1002 denotes the characteristics of the second light emitting point. In this case, it can be seen that when the current is decreased by ΔI, the light amount of the reference beam is decreased by ΔP. On the other hand, if the current is reduced by ΔI in the same way for the second light emitting point, the amount of light also decreases by a larger ΔP ′. This shows the fact that the amount of change in the amount of light differs for each light emitting point even if the amount of change in the current is the same. Therefore, if the beam output from the first light emitting point is used as the reference beam during the light amount control, the accuracy of the light amount control for the second light emitting point is relatively lowered.

  In particular, the characteristics of red surface emitting lasers vary greatly from light emitting point to light emitting point due to manufacturing processes, materials, or physical factors, compared to the characteristics of infrared surface emitting lasers. Therefore, it can be said that the accuracy of light quantity control is more likely to be lowered in the red surface emitting laser. However, if a higher resolution of an electrophotographic image forming apparatus is pursued, a red surface emitting laser capable of making the spot diameter smaller than that of an infrared surface emitting laser will be required. Therefore, in the future, the above-described problem of light quantity control will be a problem that cannot be avoided.

  Accordingly, an object of the present invention is to provide a technique for maintaining the accuracy of light amount control for each light emitting element even when there is a variation in current-light amount characteristics among a plurality of light emitting elements. Other issues can be understood throughout the specification.

  The present invention is realized in, for example, a light amount control apparatus that can be applied to an exposure apparatus or an image forming apparatus. The light amount control device is a device that controls the light amount of the light beam output from each of the plurality of light emitting elements.

  The light quantity control device includes, for example, a holding unit, a light receiving unit, and a control unit. When the plurality of light-emitting elements are classified into a plurality of groups based on the similarity of the light-emitting characteristics, the holding unit is configured to represent a representative light-emitting element that represents the group in each group and each light emission different from the representative light-emitting element. The difference in light emission characteristics from the element is maintained. The light receiving means causes the representative light emitting element to emit light in each group, and receives the light beam output from the representative light emitting element. The control means performs light quantity control for the remaining light emitting elements belonging to the group based on the difference between the received light quantity of the light beam from the representative light emitting element and the light emission characteristics held in the holding means in each group.

  According to the present invention, it is possible to perform light amount control with relatively high accuracy even if there are variations in current-light amount characteristics among a plurality of light emitting elements. Of course, since the light amount control can be executed without lighting all the light emitting elements, there is an advantage that the time required for the light amount control can be shortened.

  An embodiment of the present invention is shown below. Of course, the individual embodiments described below will be helpful in understanding various concepts, such as the superordinate concept, intermediate concept and subordinate concept of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

[First Embodiment]
FIG. 1 is an exemplary block diagram illustrating a surface emitting laser and an APC circuit according to an embodiment. The light quantity control device 100 includes an APC circuit 101, a storage device 102, a light receiving element 103, and the like. APC is an abbreviation for Automatic Power Control (automatic power control). A surface emitting laser 110, which is an example of a light beam output device, includes six light emitting elements 1, 2, 3, 4, 5, and 6. Note that the number of light emitting elements is not limited to 6, and may be less than 6 or 6 or more. However, the greater the number of light emitting elements, the greater the effect of the present invention. In the present embodiment, the plurality of light emitting elements 1 to 6 are classified into a plurality of groups based on the similarity of the light emission characteristics.

  The storage device 102 is a storage unit such as a ROM. The element characteristic information 104 stored in the storage device 102 is information representing a difference in light emission characteristics between a representative light emitting element representing the group and each light emitting element different from the representative light emitting element in each group. Thus, the storage device 102 is an example of a holding unit that holds a difference in light emission characteristics. The element characteristic information 104 may be information on a difference in light emission characteristics measured at the time of factory shipment, or may be information measured dynamically as described later.

  The light receiving element 103 such as a photodiode (PD) receives the light beam reflected by the half mirror 105 serving as a beam separating unit out of the light beams output from the light emitting element. Then, the light receiving element 103 outputs an electrical signal corresponding to the amount of received light to the APC circuit 101. When the light amount control is executed, the APC circuit 101 causes the representative light emitting elements in each group to emit light, so that the light receiving element 103 receives only the light beam output from the representative light emitting elements.

  The APC circuit 101 is a control unit that performs light amount control on the remaining light emitting elements belonging to the group based on the difference between the received light amount of the light beam from the representative light emitting element in each group and the light emission characteristic held in the holding unit. It is an example.

  FIG. 2 is an exemplary block diagram for an APC circuit. Each unit may be realized by a logic circuit such as an ASIC, or may be realized by a CPU, a ROM, a RAM, and software.

  The control target selection unit 200 selects a light emitting element that is a target of light amount control, and outputs identification information (element number or the like) of the selected light emitting element to each unit. For example, the control target selection unit 200 recognizes which light emitting element belongs to which group and which light emitting element is the representative light emitting element based on the group classification information held in the storage device 102. The group classification information may be a part of the element characteristic information 104 described above, or may be stored as a table or file different from the element characteristic information 104. For example, the control target selection unit 200 reads out the element numbers of the representative light emitting elements in the first group, and requires a unit (for example, the lighting control unit 201, the first light amount control unit 202, the second light amount control). Section 203).

  The lighting control unit 201 turns on the light emitting element by causing a predetermined drive current to flow through the light emitting element selected by the control target selecting unit 200. The value of the drive current is set by the first light quantity control unit 202 or the second light quantity control unit 203, for example. When the light amount control is executed, the lighting control unit 201 lights only the representative light emitting elements in each group. That is, the lighting control unit 201 does not light the remaining light emitting elements belonging to the group.

  The first light quantity control unit 202 executes the light quantity control for the representative light emitting element by acquiring the change in the received light quantity for the representative light emitting element as the light emission characteristic when the drive current passed to the representative light emitting element is changed. To do. For example, the first light quantity control unit 202 sets the value of the drive current that is passed to the representative light emitting element to the lighting control unit 201. This value is changed at an appropriate timing. In addition, received light amount data obtained by A / D converting a signal corresponding to the received light amount output from the light receiving element 103 is input to the first light amount control unit 202. The first light quantity control unit 202 writes the value of the drive current for achieving the necessary light quantity into the storage device 102 as the light emission characteristic at that time from the current drive current value and the current received light quantity data. Thereafter, the first light amount control unit 202 specifies a drive current for achieving a light amount corresponding to an image signal for forming an image from the stored light emission characteristics according to the light emission characteristics, and turns on the lighting control unit. Set to 201.

  The second light quantity control unit 203 reads the difference in light emission characteristics for the remaining light emitting elements belonging to the group to which the representative light emitting element belongs, and reflects the read light emission characteristic difference in the obtained light emitting characteristics of the representative light emitting element. The light quantity control of each remaining light emitting element is executed. For example, the second light quantity control unit 203 is notified of the element numbers of the remaining light emitting elements from the control target selection unit 200, and reads out data on the difference in light emission characteristics corresponding to the notified element numbers from the storage device 102. Further, the second light quantity control unit 203 applies the difference data to the light emission characteristic (drive current-light quantity characteristic) at that time for the representative light emitting element acquired from the first light quantity control unit 202 or the storage device 102. As a result, the second light quantity control unit 203 determines the light emission characteristics at that time for the remaining light emitting elements different from the representative light emitting elements, and writes them in the storage device 102. Thereafter, the second light quantity control unit 203 specifies a drive current for achieving a light quantity corresponding to an image signal for forming an image from the stored light emission characteristics according to the light emission characteristics, and turns on the lighting control part. Set to 201.

FIG. 3 is a diagram illustrating an example of element characteristic information. The element characteristic information 104 includes, for each light emitting element, an element number, a difference in light emission characteristic, identification information of the belonging group, and information indicating whether it is a representative light emitting element. According to FIG. 3, each light emitting element is classified into two groups A and B. That is, the light emitting elements 1, 2, and 3 belong to the group A, and the light emitting elements 4, 5, and 6 belong to the group B. Note that the number of light emitting elements belonging to each group may be the same or different. Various group classification methods are conceivable. For example, paying attention to the similarity between the current-light quantity characteristics of the light emitting elements, there is a method of classifying those having relatively similar characteristics into the same group. In general, it would be desirable to classify the light emitting elements into the same group so that a suitable control result can be obtained when the light amount is controlled based on the light emission characteristics of the representative light emitting elements.

  FIG. 4 is a diagram illustrating an example of the current-light quantity characteristic. The horizontal axis indicates the drive current, and the vertical axis indicates the amount of received light. This figure shows the characteristics of the six light emitting elements described above. According to this figure, the characteristics of the light emitting elements 1, 2, and 3 are close to those of the remaining light emitting elements. On the other hand, the light emitting elements 4, 5, and 6 have similar characteristics as compared with the remaining light emitting elements. Therefore, the light emitting elements 1, 2, and 3 are classified into the group A, and the light emitting elements 4, 5, and 6 are classified into the group B. In addition, according to FIG. 1, although the light-emitting elements 1, 2, and 3 are also near physical distance, this is only an example. Even if the physical distance between the two light emitting elements is long, if the light emitting characteristics are similar, they are classified into the same group. For example, the light emitting elements 1, 4 and 6 in FIG. 1 may belong to the same group.

There are various methods for selecting a representative light emitting element which is a representative light emitting element within the group. For example, the selection condition may be that the peak light amount and the peak differential efficiency in the current-light amount characteristic are equal to or higher than those of other light emitting elements in the same group. The peak light amount is the maximum value (P _max ) of the received light amount in the current-light amount characteristic. The peak differential efficiency (ΔP / ΔI) is expressed as a change amount (ΔP) of the light amount with respect to a change amount (ΔI) of the drive current. According to such a selection condition, the representative light emitting element of group A is the light emitting element 1. The representative light emitting element of group B is the light emitting element 4.

  FIG. 5 is a diagram for explaining the difference between the light emission characteristics of the representative light emitting elements and the light emission characteristics of the other light emitting elements. The horizontal axis indicates the drive current, and the vertical axis indicates the amount of received light. Here, group A will be described.

As can be seen from FIGS. 4 and 5, the light emission characteristic (current-light quantity characteristic), which is the relationship between the drive current and the corresponding light quantity, is often different for each light emitting element. For example, assume that the drive current for each light emitting element belonging to group A is changed by ΔI. In this case, the amount of change in the light amount of each light emitting element is ΔP ₁ > ΔP ₂ > ΔP ₃ . Here, ΔP ₁ indicates the amount of light amount change for the light emitting element 1. ΔP ₂ indicates the amount of light amount change for the light emitting element 2. ΔP ₃ indicates the amount of light quantity change for the light emitting element 3. Therefore, the difference (ΔP ₁ −ΔP ₂ = 0.1) in the light emission characteristics of the light emitting element 2 with respect to the representative light emitting element is stored in the storage device 102. Similarly, the difference (ΔP ₁ −ΔP ₃ = 0.3) in the light emission characteristics of the light emitting element 3 is also stored in the storage device 102. For example, the second light quantity control unit 203 reads the difference data (= 0.1) for the light emitting element 2 to obtain the same light quantity as the light emitting element 1 in the light emitting element 2 as compared with the light emitting element 1. Recognizing that it is necessary to pass 0.1 times more current to the light emitting element 2. Note that the light emission characteristic difference data may be stored in, for example, the storage device 102 measured at the time of factory shipment, or may be dynamically measured and stored in the storage device 102 as described later.

  FIG. 6 is an exemplary flowchart showing a light amount control method according to the embodiment. In step S601, the APC circuit 101 determines whether it is time to execute light amount control. Since a general laser outputs a light beam forward and backward, the light amount of the light beam output forward can be estimated based on the light amount obtained by receiving the rear light beam. On the other hand, the edge emitting laser outputs a light beam only forward. Therefore, when the edge emitting laser is employed, it is necessary to guide the light beam to the light receiving element using the half mirror 105 as shown in FIG. Furthermore, when the present invention is applied to an exposure apparatus (optical scanning apparatus) of an image forming apparatus, one scanning cycle of the light beam is an image forming period in which the light beam is used to form an image, and an image is formed. Therefore, it is divided into a non-image forming period that is not used. Therefore, the APC circuit 101 determines that APC should be executed when the non-image forming period comes, and determines that APC should not be executed when the image forming period comes. If APC is to be executed, the process proceeds to step S602.

  In step S602, the control target selection unit 200 selects a group to be controlled. Since identification information is assigned to each of a plurality of groups, the control target selection unit 200 selects groups one by one in accordance with the identification information. In step S603, the control target selection unit 200 selects a representative light emitting element among the light emitting elements included in the selected group. For example, the control target selection unit 200 identifies the element number of the representative light emitting element based on the element characteristic information read from the storage device 102.

  In step S604, when the control target selection unit 200 outputs the element number of the representative light emitting element to the lighting control unit 201 and the first light amount control unit 202, the lighting control unit 201 turns on the light emitting element corresponding to the element number. In step S <b> 605, the first light amount control unit 202 uses the light receiving element 103 to measure the received light amount of the representative light emitting element. That is, the light beam output from the representative light emitting element is received by the light receiving element 103, and a signal corresponding to the amount of received light is output from the light receiving element 103. This signal is converted from an analog signal to a digital signal by an A / D converter and input to the first light quantity control unit 202.

  In step S606, the first light amount control unit 202 determines whether or not the received light amount satisfies a predetermined reference light amount. If it satisfies, the process proceeds to step S608. On the other hand, if not, the process proceeds to step S607. In step S607, the first light amount control unit 202 determines a change amount (correction amount) ΔI of the drive current so that the received light amount becomes a predetermined reference light amount, and sets the determined change amount in the lighting control unit 201. To do. The lighting control unit 201 reflects the set change amount ΔI in the drive current. Thereafter, the process returns to step S605.

  In step S <b> 608, the second light amount control unit 203 reads the light emission characteristic difference data from the storage device 102 for each of the remaining light emitting elements in the selected group. Note that the element numbers of the remaining light emitting elements other than the representative light emitting elements are extracted from the element characteristic information 104 by the control target selection unit 200 and notified to the second light amount control unit 203, for example. Note that the second light quantity control unit 203 may directly acquire the element numbers of the remaining light emitting elements by referring to the element characteristic information 104. In this case, the control target selection unit 200 may notify the second light quantity control unit 203 of the group identification information or the element number of the representative light emitting element.

In step S609, the second light amount control unit 203 executes light amount control of a light emitting element different from the representative light emitting element, using data of light emission characteristic difference. The light amount control of the light emitting element different from the representative light emitting element is executed by applying data of the difference in light emission characteristics to the change amount ΔI determined for the representative light emitting element. Referring to the element characteristic information 104, it can be seen that the difference data for the light emitting element 2 is “0.1”. Therefore, the change amount [Delta] I ₂ of the driving current for the light emitting element 2, and _{ΔI 2 = ΔI + ΔI × 0.1} , is calculated _{(ΔI 2 = 1.1 × ΔI)} . The drive current [Delta] I ₃ of light-emitting element 3, and _{ΔI 3 = ΔI + ΔI × 0.3} , is calculated _{(ΔI 3 = 1.3 × ΔI)} .

  According to the present invention, it is possible to perform light amount control with relatively high accuracy even if there are variations in current-light amount characteristics among a plurality of light emitting elements. Of course, since the light amount control can be executed without lighting all the light emitting elements, there is an advantage that the time required for the light amount control can be shortened.

  By classifying the plurality of light emitting elements into a plurality of groups based on the similarity of the light emission characteristics, the light quantity control of other light emitting elements can be performed with high accuracy. This is because the light emitting characteristics of the other light emitting elements are similar to the light emitting characteristics of the representative light emitting element. That is, similar ones belong to the same group. Note that if the light emission characteristic is relatively stable if there is no failure in the light emitting element, the light emission characteristic may be acquired at the time of shipment from the factory, and the group classification may be performed based on the acquired light emission characteristic.

  The light emission characteristic is, for example, a relationship (current-light quantity characteristic) between a drive current for driving the light emitting element and a corresponding light quantity. In this case, the difference in the light emission characteristics may be a difference in peak light amount that is the maximum value of the received light amount, or may be a peak differential efficiency expressed as a change amount of the light amount with respect to a change amount of the drive current. In particular, if the light emitting element having the maximum peak light quantity and peak differential efficiency within the group is selected as the representative light emitting element, it is easy to maintain the light quantity control accuracy for the light emitting element different from the representative light emitting element. This is because if the light emitting element having a small peak light quantity is used as a reference, the light quantity control accuracy for the other light emitting elements is lowered.

  Since the surface emitting laser has an advantage that it can irradiate a target with many light beams at one time, it may be suitably used in an exposure apparatus or an image forming apparatus. In particular, since the red surface emitting laser has a shorter wavelength than the infrared surface emitting laser, a finer image can be formed. However, it can be said that there is a need to apply the present invention because the variation in the emission characteristics between the light emitting elements of the red surface emitting laser is larger than the variation in the light emission characteristics between the light emitting elements of the infrared surface emitting laser.

  In the image forming apparatus, one scanning period of the light beam can be divided into an image forming period and a non-image forming period. Generally, since the ratio of the image forming period to the non-image forming period is 9: 1, it can be said that the non-image forming period is very short. On the other hand, it is desirable that the light amount control is executed in the non-image forming period in order not to deteriorate the image quality. Therefore, it can be said that the utility value of the present invention increases as the number of light emitting elements increases.

[Second Embodiment]
In the first embodiment, it has been described that acquisition of group classification and difference data of light emission characteristics is executed at the time of factory shipment. However, if the representative light emitting element breaks down or the amount of light suddenly decreases, the light amount control may not be performed for other light emitting elements. Therefore, in the present embodiment, a method for dynamically executing these processes will be described.

  FIG. 7 is a block diagram of a processing apparatus in charge of group classification processing according to the embodiment. These processing devices may be realized as a part of the light amount control device. The measurement unit 701 receives a signal (data) representing the amount of received light from the light receiving element 103 and measures the light emission characteristics of each light emitting element. The classification unit 702 classifies each light emitting element into a plurality of groups based on the light emission characteristics of each light emitting element measured by the measurement unit 701. For example, the classification unit 702 groups two or more light emitting elements having similar light emission characteristics (such as peak light amount and peak differential efficiency) of each light emitting element as one group. The classification unit 702 gives identification information (ID) to each group and outputs the element numbers of the light emitting elements belonging to the group to the information creation unit 705.

  The representative light emitting element determination unit 703 determines a representative light emitting element representing the group among a plurality of light emitting elements belonging to the same group. The representative light emitting element determining unit 703 determines, as the representative light emitting element, a light emitting element in which the peak light amount or peak differential efficiency of each light emitting element received from the measuring unit 701 or the classification unit 702 is equal to or greater than that of other light emitting elements. To do. The representative light emitting element determining unit 703 outputs the determined element number of the representative light emitting element to the information creating unit 705.

  The difference calculation unit 704 calculates a difference between the light emission characteristics of the representative light emitting element and the light emission characteristics of other light emitting elements belonging to the same group. The difference calculation unit 704 outputs the calculated difference data to the information creation unit 705. The information creation unit 705 creates element characteristic information 104 from group identification information, element numbers of light emitting elements belonging to the group, element numbers of representative light emitting elements, and difference data, and writes the element characteristic information 104 to the storage device 102.

  According to this embodiment, since grouping and determination of the representative light emitting elements are performed dynamically, the influence on other light emitting elements can be suppressed even if a problem occurs in the representative light emitting elements.

[Other Embodiments]
The light quantity control device and the light beam output device according to the present embodiment may be employed as an exposure device of an image forming apparatus or an optical scanning device of an image reading device.

  FIG. 8 is a schematic cross-sectional view of the image forming apparatus according to the embodiment. An exposure apparatus 801 that is an example of an optical scanning apparatus irradiates a surface of a uniformly charged image carrier (eg, photosensitive drum) 802 with a beam. As a result, a latent image corresponding to the print target image is formed on the surface of the image carrier 802. A developing device (eg, developing roller) 803 develops the latent image using a developer. A transfer device (for example, a transfer roller) 804 transfers the developer image from the image carrier 802 to the recording medium S. The fixing device 805 fixes the developer image on the recording medium. The image forming apparatus can be commercialized as a copying machine, a printer, a printing apparatus, a facsimile apparatus, or a multifunction machine.

  FIG. 9 is a view showing an example of an exposure apparatus according to the embodiment. The light beam output from the surface emitting laser 110 passes through the collimator lens 901, the condenser lens 902, and the beam shaping slit 903 and enters the rotating polygon mirror 904. The light beam reflected by the polygon mirror 904 passes through the fθ lens 905 and the condenser lens 906 and scans on the rotating image carrier 802. Then, an electrostatic latent image is formed on the image carrier 802 by repeating this series of operations.

  In particular, by applying the light amount control device of the present embodiment to the exposure apparatus, the light amount of each light emitting element provided in the surface emitting laser 110 can be suitably controlled, so that the quality of the formed image is maintained well. can do.

It is an exemplary block diagram which shows the surface emitting laser and APC circuit which concern on embodiment. FIG. 3 is an exemplary block diagram for an APC circuit. It is a figure which shows an example of element characteristic information. It is a figure which shows an example of an electric current-light quantity characteristic. It is a figure for demonstrating the difference of the light emission characteristic about a typical light emitting element, and each light emission characteristic about the other light emitting element. It is an exemplary flowchart which shows the light quantity control method which concerns on embodiment. It is a block diagram of a processing apparatus in charge of group classification processing and the like according to the embodiment. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. It is a figure which shows an example of the exposure apparatus which concerns on embodiment. It is a graph which shows an example of the electric current-light quantity characteristic in a surface emitting laser.

Claims (13)

A light amount control device that controls the amount of light beams output from a plurality of light emitting elements,
The plurality of light emitting elements are classified into a plurality of groups based on the similarity of the light emitting characteristics. In each group, the light emitting characteristics of a representative light emitting element representing the group and each light emitting element different from the representative light emitting element. Holding means for holding the difference between,
A light receiving means for causing the representative light emitting element to emit light in each group and receiving a light beam output from the representative light emitting element;
Control means for performing light quantity control on the remaining light emitting elements belonging to the group based on the received light quantity of the light beam from the representative light emitting element in each group and the difference in the light emission characteristics held in the holding means. The light quantity control apparatus characterized by the above-mentioned. The control means includes
Lighting control means for lighting only the representative light emitting element in each group,
A first light amount for executing light amount control for the representative light emitting element by acquiring, as the light emission characteristic, a change in received light amount for the representative light emitting element when the drive current passed to the representative light emitting element is changed. Control means;
Reading the difference in the light emission characteristics for each remaining light emitting element in the group to which the representative light emitting element belongs, and reflecting the read difference in the light emitting characteristics in the acquired light emitting characteristics of the representative light emitting elements, The light quantity control device according to claim 1, further comprising second light quantity control means for performing light quantity control of the light emitting element.   The light quantity control device according to claim 1, wherein the holding unit includes a storage unit that stores the difference in the light emission characteristics measured at the time of factory shipment. A measuring means for measuring the light emission characteristics of each light emitting element;
Classification means for classifying each light emitting element into a plurality of groups from the light emission characteristics of each light emitting element measured by the measuring means;
Determining means for determining the representative light emitting element from a plurality of light emitting elements belonging to the group;
The holding means is
The light quantity control device according to claim 1, further comprising a storage unit that stores a difference between the light emission characteristics obtained from the light emission characteristics measured by the measurement unit.   5. The light quantity control device according to claim 1, wherein the light emission characteristic is a relationship between a drive current for driving the light emitting element and a light quantity corresponding to the drive current. 6.   The light quantity control device according to claim 5, wherein the difference in the light emission characteristics is a difference in peak light quantity which is a maximum value of received light quantity.   The light amount control device according to claim 5, wherein the difference in the light emission characteristics is a peak differential efficiency expressed as a change amount of the light amount with respect to a change amount of the drive current.   The light quantity control device according to claim 1, wherein the plurality of light emitting elements are surface emitting lasers.   The light quantity control device according to claim 8, wherein the surface emitting laser is a red surface emitting laser.   The surface emitting laser is an edge emitting laser, and one scanning period of the light beam output from the edge emitting laser forms an image, and an image forming period in which the light beam is used and an image forming period. The light quantity control device according to claim 8, wherein the control unit executes the light quantity control in the non-image forming period. An exposure apparatus,
A light beam output device comprising a plurality of light emitting elements each outputting a light beam;
An exposure apparatus comprising: a light amount control device according to claim 1, which controls a light amount of each light emitting element provided in the light beam output device. An image forming apparatus,
An exposure apparatus according to claim 11,
An image carrier on which a latent image is formed by the exposure apparatus;
A developing device for developing the latent image formed on the image carrier into a developer image;
A transfer device for transferring the developer image to a recording medium;
An image forming apparatus comprising: a fixing device that fixes the transferred developer image on the recording medium. A light amount control method for controlling the amount of light beams respectively output from a plurality of light emitting elements,
When the plurality of light emitting elements are classified into a plurality of groups based on similarity of light emission characteristics, the representative light emitting elements representing the group in each group emit light, and the light beam output from the representative light emitting elements A light receiving process for receiving light;
When performing the light amount control of each of the remaining light emitting elements belonging to the same group as the representative light emitting element, the remaining light amount from the difference in light emission characteristics with respect to the representative light emitting element and the received light amount of the light beam output from the representative light emitting element And a control step of performing light amount control for each light emitting element.

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