JP2007203603A - Light emitting device, electronic equipment and image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively suppress a plurality of kinds of tone irregularities generated by separate causes. <P>SOLUTION: A buffer 321 stores a correction value Aa of each light emitting element E. A buffer 322 stores a correction value Ab of each light emitting element E. A control part 326 designates a first mode or a second mode for each line which constitutes an image. When each pixel of the line for which the first mode is designated is output, each light emitting element E is driven according to image data G and the correction value Aa. When each pixel of the line for which the second mode is designated is output, the light emitting element E is driven according to the image data G and the correction value Ab. The correction value Aa is selected for each light emitting element E to suppress a difference of quantities of light of the light emitting elements when a predetermined electric energy is supplied. The correction value Ab is selected for each light emitting element E to suppress a difference of forms of spot regions corresponding to the light emitting elements E when a predetermined electric energy is supplied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an organic light emitting diode (hereinafter referred to as “OLED (Organic Light Emitting Diode)”.
The present invention relates to a technique for controlling the light amount of a light emitting element such as an element.

A light-emitting device in which a plurality of light-emitting elements are arranged is used as a device that outputs an image, such as an exposure device (optical head) of an image forming apparatus or a display device of various electronic devices. In this type of light-emitting device, if the light amount of each light-emitting element varies, gradation unevenness occurs in an actually output image. In order to suppress this gradation unevenness, for example, in Patent Document 1, the amount of radiated light from each light emitting element is measured in advance, and the current value and pulse width of the current supplied to each light emitting element are measured. A technique for correcting according to the result is disclosed.
JP 2003-118163 A

By the way, in the image forming apparatus configured to form a latent image on the surface of the photosensitive drum by the exposure of the light emitting elements, the cause of uneven gradation is not only the variation in the luminous intensity (light emission intensity) of each light emitting element. For example, even when the size and shape of the spot area on the surface of the photosensitive drum (the area where the emitted light from each light emitting element reaches with a light intensity exceeding a predetermined value) is different for each light emitting element, the image has uneven gradation. appear. In this case, even if the light intensity of each light emitting element is corrected so as to suppress the gradation unevenness caused by the variation in luminous intensity of each light emitting element, the floor caused by the variation in the form (size or shape) of the spot area is not affected. It is not always possible to suppress the unevenness. Against this background, an object of the present invention is to solve the problem of effectively suppressing a plurality of types of gradation unevenness caused by different causes.

In order to solve the above-described problems, a light emitting device according to the present invention corresponds to a pixel constituting an image and supplies an object to be irradiated (for example, the photosensitive drum 110 in FIG. 6) by supplying electric energy (for example, a driving current). A first correction value selected for each light emitting element is stored so as to suppress a difference in light quantity (luminosity) between the plurality of light emitting elements that emit light and the plurality of light emitting elements when predetermined electric energy is supplied. The first storage means (for example, the ROM 26 and the buffer 321 in FIGS. 1 and 5) and the radiated light from each of the plurality of light emitting elements to which predetermined electric energy is supplied out of the surface of the irradiated object are given values (for example, The second correction value selected for each light emitting element is stored so as to suppress the difference in the form (size or shape) of the spot area (for example, the area As in FIG. 3) that reaches with an intensity exceeding the threshold value Pth in FIG. ROM2 in the second storage means (for example, FIG. 1 and FIG. 5 that
6 and the buffer 322), designation means for designating the first mode or the second mode for each of a plurality of areas into which the image is divided (for example, the control unit 326 in FIGS. 1 and 5), and the designation means selects the first mode. For each pixel in the designated area (for example, at the time of outputting each pixel), electric energy corresponding to the image data of each pixel and the first correction value of the light emitting element is supplied to each of the plurality of light emitting elements. Driving means for supplying electric energy corresponding to the image data of each pixel and the second correction value of the light emitting element to each of the plurality of light emitting elements for each pixel in the region in which the second mode is designated (for example, FIG. 1). And a correction unit 327 and a drive circuit 24) of FIG.
In this configuration, at the time of output of each pixel in the region in which the first mode is designated, the difference in the amount of light of each light emitting element is suppressed by correction according to the first correction value, and each pixel in the region in which the second mode is designated. At the time of output, the difference in the form of the spot area of each light emitting element is suppressed by the correction according to the second correction value. Therefore, the gradation unevenness (for example, the first gradation unevenness B1 in FIG. 4) due to the difference in the light amount of each light emitting element and the gradation unevenness (for example, the first unevenness in FIG. 4) due to the difference in the form of the spot area of each light emitting element. Compared with a configuration in which only one of the two gradation unevenness B2) is eliminated, a high-quality image with reduced gradation unevenness can be formed.

In addition to a configuration in which one of the first mode and the second mode is selected alternatively, a configuration in which any of three or more operation modes including the first mode and the second mode is selected (for example, in FIG. 5 Naturally, the configuration is also included in the scope of the present invention. The “plurality of light emitting elements” in the present invention may be all or part of the light emitting elements included in the light emitting device. The “irradiated body” is an object to which the radiated light from each light emitting element arrives. For example, a photosensitive body (for example, a photosensitive drum) on which a latent image is formed by exposure with the radiated light from each light emitting element. It is.

As described above, at the time of outputting a pixel in which the second mode is designated, the correction according to the first correction value is not executed for the light amount of each light emitting element. Therefore, each pixel belonging to the region in which the second mode is designated may be affected by variation in characteristics among the light emitting elements.
However, if the form (size or shape) of the region serving as the unit for specifying the operation mode is appropriately selected, the influence of variations in the characteristics of the light emitting elements may be made inconspicuous even in the region in which the second mode is specified. Is possible. As such a configuration, for example, a configuration is conceivable in which the second mode is specified for a plurality of regions set so that the positions of the images are dispersed, and the first mode is specified for other regions. A first direction corresponding to each light emitting element (
For example, in a light-emitting device that forms an image formed by arranging lines composed of a plurality of pixels arranged in the main scanning direction in the second direction (for example, the sub-scanning direction), the image is divided into a predetermined number of lines. A configuration in which the first mode or the second mode is designated in units of areas is employed.
In a further preferred aspect, the designating unit designates one of the first mode and the second mode for each odd-numbered line and designates the other of the first mode and the second mode for each even-numbered line.

In a specific aspect of the present invention, the driving unit drives the light emitting elements based on the correcting unit (for example, the correcting unit 327 in FIGS. 1 and 5) for correcting the image data of each pixel and the corrected image data. Driving circuit (for example, the driving circuit 24 in FIGS. 1 and 5). The correction means executes a predetermined calculation for the image data and the first correction value of each pixel for which the first mode is specified, and sets the predetermined value for the image data and the second correction value of each pixel for which the second mode is specified. Execute the operation. A typical example of the calculation of the image data and each correction value is addition (or subtraction), but the specific content of this calculation is arbitrarily changed. The drive circuit drives each light emitting element by outputting a drive signal having a level (current value or voltage value) or a pulse width corresponding to the image data calculated by the correcting means.
However, the light emitting device according to the present invention only needs to have a function of driving each light emitting element according to the image data of each pixel and the first correction value, and the image data and the first correction value (or the second correction value). It is not always necessary to provide means for calculating (value). For example, the driving means according to another aspect is
When the first mode is designated, each light emitting element is adjusted after the level or pulse width of a drive signal (level or pulse width drive signal corresponding to the image data) is adjusted according to the first correction value. Output to.

The light emitting device according to the present invention is used in various electronic devices. A typical example of this electronic apparatus is an image forming apparatus using the light emitting device of the present invention as an exposure device (exposure head). This image forming apparatus includes an image carrier (for example, the photosensitive drum 110 in FIG. 6) on which a latent image is formed on the image forming surface by exposure, the light emitting device of the present invention that exposes the image forming surface, and development of toner or the like. A developing unit (for example, the developing unit 114 in FIG. 6) that forms a visible image by attaching the agent to the latent image. However,
The use of the light emitting device according to the present invention is not limited to exposure. For example, the light-emitting device of the present invention can be used as a display device for various electronic devices. Examples of this type of electronic device include a personal computer and a mobile phone. The light emitting device of the present invention can also be used as various lighting devices such as a device (backlight) that is arranged on the back side of a liquid crystal device and illuminates the device, and a device that is mounted on an image reading device such as a scanner and irradiates light on a document. A device can be employed.

The present invention is also specified as an image processing device used in the light emitting device according to each of the above aspects. This image processing apparatus (for example, the controller 32 in FIGS. 1 and 5) is selected for each light emitting element so that the difference in the amount of light of each of the plurality of light emitting elements when a predetermined electric energy is supplied is suppressed. First storage means (for example, FIG. 1 or FIG. 5) that stores a first correction value (for example, correction value Aa).
And the difference in the form of the spot region where the radiated light from each of the plurality of light emitting elements supplied with the predetermined electrical energy reaches the intensity exceeding the predetermined value is suppressed. As described above, the second storage means (for example, the buffer 322 in FIGS. 1 and 5) for storing the second correction value (for example, the correction value Ab) selected for each light emitting element, and each of the plurality of regions into which the image is divided. Specification means (for example, the control unit 326 in FIGS. 1 and 5) for designating the first mode or the second mode, and image data of each pixel belonging to the area in which the designation means designates the first mode are stored in the first storage means. The second correction value stored in the second storage means is stored in the second storage means for the image data of each pixel belonging to the area for which the designation means designates the second mode. According to Correction means (for example, the correction unit 327 in FIGS. 1 and 5) that outputs the light to the light emitting device after correction. This image processing apparatus also has the same operations and effects as the light emitting device of the present invention.

In addition, about the image processing apparatus of this invention, the various aspects illustrated above about the light-emitting device are employ | adopted. The image processing apparatus of the present invention may be realized only by hardware such as a DSP (Digital Signal Processor) or a CPU (Central Processing Unit).
) Or the like, and may be realized by cooperation of software.

<A: Configuration of light emitting device>
The structure of the light emitting device according to the embodiment of the present invention will be described. This light emitting device is used as an exposure device for exposing a photosensitive drum in an image forming apparatus (printing apparatus) configured to form a latent image by exposure of the photosensitive drum. In the present embodiment, it is assumed that an image (latent image) in which pixels are arranged in vertical m rows × horizontal n columns is formed (each of m and n is a natural number of 2 or more).
A set of n pixels (one row) arranged in the main scanning direction (direction of the rotation axis of the photosensitive drum) in one image is hereinafter referred to as “line”.

FIG. 1 is a block diagram illustrating a configuration of a light emitting device according to the present embodiment. As shown in the figure, the light emitting device 10 includes a head module 20 and a control board 30. Head module 2
Reference numeral 0 denotes a means for emitting a light beam corresponding to a desired image to the outer peripheral surface (hereinafter referred to as “image forming surface”) of the photosensitive drum, and includes an optical head 22, a drive circuit 24, and a ROM 26. The optical head 22 is a portion in which n light emitting elements E corresponding to the number of pixels in one line in the image are arranged along the main scanning direction. Each light emitting element E emits light with a light amount corresponding to the electric energy supplied thereto. The light-emitting element E of the present embodiment is an OLED element in which a light-emitting layer formed of an organic EL (ElectroLuminescence) material is interposed in a gap between an anode and a cathode, and the current value during a period when a drive current is supplied to the light-emitting layer. It emits light with the light intensity according to.

The drive circuit 24 is means for driving each light emitting element E to a light amount (luminous intensity and time) corresponding to the image data G by supplying electric energy (drive current) corresponding to the image data G. The image data G is digital data that designates one of a plurality of gradation values for each light emitting element E. The drive circuit 24 of the present embodiment controls the light amount of each light emitting element E by controlling the pulse width of the drive current whose current value is set to a predetermined value in accordance with the image data G (level by the pulse width modulation method). Control). In this way, by moving the image forming surface of the photosensitive drum in the sub-scanning direction while controlling the light amount of each light emitting element E, a latent image for one page of m rows x n columns is formed on the image forming surface. Is done.

The ROM 26 is a means for storing the correction value Aa and the correction value Ab in a nonvolatile manner for each light emitting element E. The correction value Aa and the correction value Ab are numerical values for adjusting the light amount of each light emitting element E separately from the image data G. The correction value Aa and the correction value Ab set for one light emitting element E are different. The specific contents of the correction value Aa and the correction value Ab and a method for selecting each will be described later.

On the control board 30, a controller 32 and two buffers (341 and 342) are mounted. Image data G is supplied to the controller 32 from various host devices 50 (host computers) such as the CPU of the image forming apparatus in which the light emitting device 10 is mounted. The controller 32 is a means for controlling the head module 20, and includes two buffers (321 and 322), an input / output unit 325, a control unit 326, and a correction unit 327. In addition, each part (especially the control part 326 and the correction | amendment part 327) which comprises the controller 32 may be implement | achieved by hardware, such as DSP, and may be implement | achieved when computers, such as CPU, run a program.

When the power of the light emitting device 10 is turned on, the correction value Aa and the correction value Ab of each light emitting element E are transferred from the ROM 26 of the head module 20 to the controller 32 prior to driving each light emitting element E. The buffer 321 is means for storing n correction values Aa transferred from the ROM 26. Similarly, the buffer 322 is means for storing n correction values Ab transferred from the ROM 26.

The buffer 341 and the buffer 342 are means (line memory) for storing image data G of n pixels belonging to one line of the image. The input / output unit 325 alternately receives the image data G sequentially supplied from the host device 50 for each line, such as a buffer 341 and a buffer 342.
Write to Further, the input / output unit 325 alternately reads the image data G of each line from the buffer 341 and the buffer 342 and outputs the image data G to the control unit 326. That is, the input / output unit 325 writes the odd-numbered row of image data G to the buffer 341 and the buffer 34.
The reading of the even-numbered image data G from 2 and the reading of the odd-numbered row of image data G from the buffer 341 and the writing of the even-numbered row of image data G to the buffer 342 are synchronized with the horizontal synchronization signal ( That is, it is executed sequentially (every horizontal scanning period). Input / output unit 3
In the following, the line from which the image data G is read out by 25 is referred to as “target line”. Each of the m lines constituting the image is sequentially selected as a target line in the order of arrangement along the sub-scanning direction.

The control unit 326 is a means for controlling the correction mode to be executed for the light amount of each light emitting element E for each line, and generates a correction management signal S for designating either the first mode or the second mode for each line. The data is output to the correction unit 327. The first mode is an operation mode in which the light amount of the light emitting element E is controlled based on the image data G of the target line and the correction value Aa. On the other hand, the second mode is an operation mode in which the light amount of the light emitting element E is controlled based on the image data G of the target line and the correction value Ab.

FIG. 2 is a flowchart showing a specific operation of the control unit 326 in the present embodiment. The process shown in FIG. 6 is executed every time one page of image data G is supplied from the host device 50 to the controller 32 (that is, every vertical scanning period in synchronization with the vertical synchronizing signal). When the processing of FIG. 2 is started, the control unit 326 first acquires image data G for one line (target line) sequentially output by the input / output unit 325 (step S1). Next, the control unit 326 determines whether or not the target line from which the image data G has been acquired in step S1 is an odd-numbered line among m lines constituting the image (step S2). If the result of this determination is affirmative, the control unit 326 outputs the correction management signal S designating the first mode to the correction unit 327 together with the image data G of the target line (step S3). On the other hand, when the result of determination in step S2 is negative (that is, when the target line is an even-numbered line),
The control unit 326 outputs the correction management signal S designating the second mode to the correction unit 327 together with the image data G of the target line (step S4).

Subsequent to step S3 or step S4, the control unit 326 determines whether or not an operation mode has been designated for all lines of one page (step S5). When the result of this determination is negative, the control unit 326 outputs the image data G of the next line (target line) to the input / output unit 32.
5 (step S1), the process after step S2 is executed for this new target line. On the other hand, if the result of step S5 is affirmative, the process of FIG.

The correction unit 327 in FIG. 1 is a unit that executes processing according to the correction management signal S on the image data G of each line supplied from the input / output unit 325 via the control unit 326 and outputs the processed image data.
When the first mode is designated by the correction management signal S, the correction unit 327 performs a predetermined calculation on the image data G of the line and the n correction values Aa held in the buffer 321, and after this calculation Are output to the head module 20. On the other hand, the correction management signal S
When the second mode is specified by the correction unit 327, the correction unit 327 performs a predetermined calculation on the image data G of the line and the n correction values Ab held in the buffer 322, and the image data G after the calculation is performed. Is output to the head module 20. The correction unit 327 according to the present embodiment includes the image data G of the pixel in the j-th column (j is a natural number satisfying 1 ≦ j ≦ n) and the j-th pixel that outputs this pixel.
The correction value (Aa or Ab) of the light emitting element E in the column is added, and the added image data G is output to the drive circuit 24.

The drive circuit 24 supplies electric energy (drive current) corresponding to the image data G to each light emitting element E. Therefore, for a line in which the first mode is designated in one image, each light emitting element E emits light with a light amount corrected according to the correction value Aa, so that a latent image is formed on the image forming surface of the photosensitive drum. It is formed. On the other hand, for the line for which the second mode is designated, the correction value Ab
Each light emitting element E emits light with a light amount corrected according to the above, thereby forming a latent image on the image forming surface.

<B: Method of selecting correction value (Aa / Ab)>
Next, the meaning of the correction values Aa and Ab of each light emitting element E and a method for selecting each will be described.
There are various causes of gradation unevenness in an image output from the image forming apparatus. For example, not only when the light intensity (light emission intensity) of the light emitting element E is different, but also when the form (size or shape) of the spot area on the image forming surface of the photosensitive drum is different for each light emitting element E, the gradation unevenness. Occurs. Therefore, in the actually output image, gradation unevenness (hereinafter referred to as “first gradation unevenness”) due to variation in luminous intensity of each light emitting element E, and a spot area corresponding to each light emitting element E are included. In some cases, gradation unevenness (hereinafter referred to as “second gradation unevenness”) due to variations coexists. In such a case, even if the first gradation unevenness is suppressed by the correction of the amount of light according to the correction value Aa, the second gradation unevenness cannot always be eliminated. In view of the above circumstances, in the present embodiment, the correction value Aa is selected for each light emitting element E so that the first gradation unevenness is suppressed, and the correction is performed so that the second gradation unevenness is suppressed. The value Ab is selected for each light emitting element E.

The correction value Aa for each light emitting element E is selected for each light emitting element E so that the light amount of each light emitting element E when the same gradation is designated by the image data G is made uniform. For example, first, a drive current having the same current value and pulse width is supplied to each light emitting element E, and each light quantity is measured by a light receiving element such as a photodiode. Secondly, the average value of the light amounts of all the light emitting elements E is calculated based on the result of this measurement (the variation in the light amount during non-correction). Third, each correction value Aa is determined so that the light amount of each light emitting element E is adjusted to the average value of the light amount by correction (correction of the pulse width of the drive current). Therefore, for example, the correction value Aa of the light emitting element E (light emitting element E having low light emission efficiency) with a small amount of light at the time of non-correction becomes a larger numerical value.

Each correction value Ab is determined by the following procedure, for example. First, the area of the spot region (hereinafter referred to as “spot area”) is individually measured for each light emitting element E. For example, first, a plurality of light receiving elements such as CCD elements are arranged in a matrix at the position of the image forming surface of the photosensitive drum. Second, each of the n light emitting elements E is caused to emit light in turn by supplying a drive current having the same current value and pulse width. Third, based on the result of detection by each light receiving element at this time, the intensity (luminous intensity) of the light beam reaching the image forming surface of the photosensitive drum from one light emitting element E within the surface.
Measure the distribution of. FIG. 3 is a graph showing the intensity distribution in a plane parallel to the optical axis of the light emitting element E. As shown in the figure, the intensity of the light beam reaching the image forming surface is expressed by the optical axis L of the light emitting element E.
The distribution is such that the position decreases from 0. In this distribution, a spot area As is an area where a light beam having an intensity exceeding a predetermined threshold value Pth (for example, 1 / e ² ) has arrived. Then, the spot area is calculated according to the number of light receiving elements that have received a light beam exceeding the threshold value Pth. When the spot area of each light emitting element E is calculated by the above procedure, the average value of the spot areas of the n light emitting elements E is calculated. Then, the correction value Ab is set for each light emitting element E so that the spot area of each light emitting element E is adjusted to this average value by correcting the light amount.

FIG. 4 is a conceptual diagram showing an aspect of an image (image printed on paper) actually output from the image forming apparatus when the same gradation is designated for all the pixels P constituting the image IMG. . Part (a) of FIG. 4 shows an image IMG when the light amount of each light emitting element E is not corrected. If the luminous intensity of the light emitting element E in the X1 column among the n light emitting elements E is lower than the other light emitting elements E, each pixel P in the X1 column of the image IMG is more than the other pixels P. Low gradation. Further, if the spot area of the light emitting element E in the X2 column among n light emitting elements E is smaller than the other light emitting elements E, as shown in part (a) of FIG. Each pixel P in the X2th column has a lower gradation than the other pixels P. That is, the first gradation unevenness B caused by the variation in luminous intensity of each light emitting element E
1 and the second gradation unevenness B2 caused by the variation in the spot area of each light emitting element E coexist in the image IMG.

For the light emitting element E in which both the luminous intensity and the spot area are smaller than the expected values, the first gradation unevenness B1 and the second gradation unevenness B2 are simultaneously suppressed by the correction that increases the light amount. The same applies to the light emitting element E in which the luminous intensity and the spot area are larger than the expected values, and both the first gradation unevenness B1 and the second gradation unevenness B2 are suppressed by the correction for reducing the light amount.
However, for the light-emitting element E in which the luminous intensity is higher than the expected value and the spot area is smaller than the expected value, the spot area is further reduced when the light amount is decreased to suppress the first gradation unevenness B1. If the amount of light is increased in order to suppress the second gradation unevenness B2 away from the value (that is, the second gradation unevenness B2 becomes remarkable), the first gradation unevenness B1 becomes remarkable. Similarly, in the light-emitting element E in which the luminous intensity is lower than the expected value and the spot area is larger than the expected value, the suppression of the first gradation unevenness B1 and the suppression of the second gradation unevenness B2 are in contradiction. For these light emitting elements E, the first gradation unevenness B1 and the second gradation unevenness B2 cannot be suppressed simultaneously by only one correction value.

Therefore, even if the correction for suppressing the first gradation unevenness B1 is performed for all the lines of the image IMG, as shown in the part (b1) of FIG.
The second gradation unevenness B2 in the row is not suppressed (rather appears). Similarly, each light emitting element E
Even if the second gradation unevenness B2 is suppressed by the correction for equalizing the spot area of FIG.
As shown in part (b2), the first gradation unevenness B1 in the X1th column due to the variation in luminous intensity is not eliminated.

Part (c) of FIG. 4 is a conceptual diagram showing an aspect of an image IMG that is actually output under the configuration of the present embodiment. In the present embodiment, the light amount of each light emitting element E is corrected according to the correction value Aa when outputting a line in which the first mode is designated. Accordingly, in the pixel P in the X1th column belonging to each odd-numbered line, the first gradation unevenness B1 due to the variation in luminous intensity of each light emitting element E is eliminated. In addition, the light amount of each light emitting element E is corrected according to the correction value Ab when outputting the line in which the second mode is designated. Therefore, in the pixel P in the X2th column belonging to each line of the even-numbered row, the second gradation unevenness B2 due to the variation in the spot area of each light emitting element E.
Is suppressed.

By the way, as shown in part (c) of FIG. 4, the second gradation unevenness B2 remains in the pixel P in the X2th column belonging to each odd-numbered line. The two-tone unevenness B2 is hardly perceived by the human naked eye. For example, it is known that the resolving power from a clear visual distance (286 mm) in human vision is a limit value (upper limit value) of about “10 cycle / mm”. Therefore, if the image IMG is formed so that ten or more pixels P are arranged along the sub-scanning direction in the range of 1 mm in length on the surface of the paper, the second floor in each pixel P in the X2th column. The tone irregularity B2 can hardly be recognized with the naked eye. The same applies to the first gradation unevenness B1 remaining in the pixel P of the X1th column belonging to each line of the even row. As described above, in the present embodiment, the first gradation unevenness B1 due to the variation in luminous intensity of each light emitting element E and the second gradation unevenness B2 due to the variation in the form of the spot area of each light emitting element E are present. Since it is suppressed alternately for each line, the image quality perceived by the user is maintained at a high level compared to the configuration in which only one of them is eliminated (part (b1) or part (b2) in Fig. 4). There is an advantage that you can.

<C: Modification>
Various modifications can be made to the above embodiment. An example of a specific modification is as follows. In addition, you may combine each following aspect suitably. Hereinafter, the correction value Aa and the correction value Ab may be collectively referred to as “correction value A”.

(1) Modification 1
In the above embodiment, the configuration in which the ROM 26 that stores the correction value A (Aa or Ab) is mounted on the head module 20 is illustrated. However, the correction value A may be held in the controller 32 in advance. Since the correction value A is a numerical value corresponding to the characteristics of each light emitting element E, when mass-producing the light emitting device 10 in which the correction value A is held in the controller 32, the correspondence between the head module 20 and the controller 32 is determined. It is necessary to strictly manage each light emitting device 10.
On the other hand, in the above embodiment in which the correction value A is stored in the head module 20, even if the characteristics of the light emitting elements E are different for each light emitting device 10, the light emitting devices 10 are common to all the light emitting devices 10. A controller 32 can be employed. This eliminates the need for managing the correspondence between the head module 20 and the controller 32, and thus has the advantage that the manufacturing process of the light emitting device 10 is simplified.

(2) Modification 2
In the above embodiment, the configuration in which the operation mode is determined in units of one line is illustrated, but the range that is the target for determining the operation mode is arbitrarily changed. For example, a configuration in which an operation mode is designated in units of a plurality of lines is also employed. Furthermore, the range serving as a unit for determining the operation mode does not have to be an area along the main scanning direction. For example, the operation mode may be determined in units of a set of pixels (m) in each column continuous along the sub-scanning direction.

In the above embodiment, the configuration in which the line in which the first mode is designated and the line in which the second mode is designated is alternately arranged. However, the arrangement of the lines in which each mode is designated is arbitrary. is there. For example, one of the first mode and the second mode is designated for a plurality of lines selected to be dispersed as much as possible along the sub-scanning direction in the image, and the first mode and the other modes are designated for the other lines. A configuration in which the other of the second modes is designated is also adopted.

(3) Modification 3
In the above embodiment, a configuration in which a driving current having a pulse width corresponding to the image data G is supplied to each light emitting element E is illustrated. In this configuration, it can be said that the pulse width of the drive current is corrected according to the correction value A. However, the target controlled according to the image data G in the present invention is not limited to the pulse width. For example, the current value of the drive current supplied to each light emitting element E is controlled according to the image data G, and the voltage value of the voltage applied to each light emitting element E (hereinafter referred to as “drive voltage”) is an image. A configuration controlled according to the data G is also employed. In other words,
The current value of the drive current and the voltage value of the drive voltage may be corrected according to the correction value A.

(4) Modification 4
In the above embodiment, the light emitting device 10 used for exposure of the photosensitive drum has been exemplified. However, the light emitting device of the present invention can also be adopted as a device for displaying various images. In a light-emitting device used as a display device, a plurality of light-emitting elements E are arranged in a matrix in the row direction and the column direction, and a selection circuit (scanning line driving circuit) that sequentially selects the light-emitting elements E in each row. Be placed. Then, the drive circuit 2 is connected to each light emitting element E in the selected row by the selection circuit.
When the drive current is supplied from 4, each light emitting element E emits light with a light amount corresponding to the image data G.

(5) Modification 5
In the above embodiment, the configuration in which one of the first mode and the second mode is alternatively selected has been exemplified. However, an operation mode (in other words, an operation mode applied to the output of each line from among a large number of operation modes). The correction value A) used for correcting the light amount of each light emitting element E may be selected. For example, the light emitting device 10 illustrated in FIG. 5 has a configuration in which the light amount of one light emitting element E is corrected according to one of three types of correction values A (Aa, Ab, and Ac). N correction values Ac corresponding to the respective light emitting elements E are stored in the buffer 323. The correction value Ac is a numerical value selected by a procedure different from the correction value Aa and the correction value Ab. For example, the correction value Ac is a fixed value that does not depend on the characteristics of each light emitting element E.

The input / output unit 325 writes and reads the image data G of each line using three buffers (34
1 to 343). The buffer 341 stores the image data G of the (3N-2) th line, and the buffer 342 stores the image data G of the (3N-1) th line.
Is stored in the buffer 343, and the image data G of the third N-th line is stored (N is a natural number). The control unit 326 designates the first mode on the line of the (3N-2) th row, and sets the (3
N-1) The second mode is designated for the line of the third row, and the third mode is designated for the line of the third Nth row. Similarly to the above-described embodiment, the correction unit 327 performs an operation according to the correction value Aa and the correction value Ab on the image data G of each line for which the first mode and the second mode are specified, and outputs the result. Further, the correction unit 327 performs a predetermined calculation (for example, addition) on the image data G of the line for which the third mode is specified and the correction value Ac stored in the buffer 323, and outputs the result to the drive circuit 24.

According to the configuration of FIG. 5, since the light amount of the light emitting element E of each line can be corrected by various correction values A as compared with the above embodiment, it is possible to effectively reduce the gradation unevenness of the image. . Here, the case where there are three types of correction values A for one light emitting element E is illustrated, but a configuration in which a larger number of correction values A are prepared (any one of a larger number of operation modes is designated for each line). Are also adopted.

(6) Modification 6
In the above embodiment, the OLED element is exemplified as the light emitting element E, but the light emitting element employed in the light emitting device of the present invention is not limited to this. For example, instead of OLED elements, inorganic EL
Elements, light-emitting diode elements, field emission (FE) elements, surface-conduction electron emission (SE) elements, ballistic electron emission (BS)
The present invention is also applied to a light-emitting device using various light-emitting elements such as a stic electron surface emission) element as in the above embodiment. The light-emitting element in the present invention only needs to be an element that emits light by supplying electric energy, and it does not matter whether it is a current-driven type driven by supplying current or a voltage-driven type driven by applying voltage. .

<D: Electronic equipment>
Next, specific examples of the electronic device according to the present invention will be described.
FIG. 6 is a cross-sectional view showing a configuration of an image forming apparatus using the light emitting device according to the above embodiment. The image forming apparatus is a tandem type full-color image forming apparatus, and the four light emitting devices 10 (10K, 10C, 10M, and 10Y) according to the above-described form and the four photosensitive drums corresponding to the respective light emitting devices 10. 110 (110K, 110C, 110M, 110Y). One light emitting device 10 is disposed so as to face the image forming surface (outer peripheral surface) of the corresponding photosensitive drum 110. Note that the subscripts “K”, “C”, “M”, and “Y” of each symbol are used to form each visible image of black (K), cyan (C), magenta (M), and yellow (Y). Means.

As shown in FIG. 6, an endless intermediate transfer belt 120 is wound around the driving roller 121 and the driven roller 122. The four photosensitive drums 110 are arranged around the intermediate transfer belt at a predetermined interval from each other. Each photosensitive drum 110 rotates in synchronization with driving of the intermediate transfer belt 120.

Around each photosensitive drum 110, in addition to the light emitting device 10, a corona charger 111 (111
K, 111C, 111M, 111Y) and developing unit 114 (114K, 114C, 114M,
114Y). The corona charger 111 has a corresponding photosensitive drum 110.
The image forming surface is uniformly charged. Each of the light emitting devices 10 uses this charged image forming surface as image data G.
An electrostatic latent image is formed by performing exposure according to the above. Each developing device 114 applies a developer (
By attaching the toner, a visible image (visible image) is formed on the photosensitive drum 110.

As described above, the visible images of the respective colors (black, cyan, magenta, yellow) formed on the photosensitive drum 110 are sequentially transferred (primary transfer) to the surface of the intermediate transfer belt 120 to form a full-color visible image. Is done. Four primary transfer corotrons (transfer units) 112 (112K, 112C, 112M, 112Y) are arranged inside the intermediate transfer belt 120. Each primary transfer corotron 112 electrostatically attracts a visible image from the corresponding photosensitive drum 110 to thereby visualize the developed image on the intermediate transfer belt 120 that passes through the gap between the photosensitive drum 110 and the primary transfer corotron 112. Transcript.

The sheets (recording material) 102 are fed one by one from the sheet cassette 101 by the pickup roller 103 and conveyed to the nip between the intermediate transfer belt 120 and the secondary transfer roller 126. The full-color visible image formed on the surface of the intermediate transfer belt 120 is transferred (secondary transfer) to one side of the sheet 102 by the secondary transfer roller 126 and is fixed to the sheet 102 by passing through the fixing roller pair 127. . The paper discharge roller pair 128 discharges the sheet 102 on which the visible image is fixed through the above steps.

Since the image forming apparatus exemplified above uses an OLED element as a light source (exposure means), the apparatus is made smaller than a configuration using a laser scanning optical system. Note that the present invention can also be applied to image forming apparatuses having configurations other than those exemplified above. For example, a rotary development type image forming apparatus, an image forming apparatus that directly transfers a visible image from a photosensitive drum to a sheet without using an intermediate transfer belt, or an image forming that forms a monochrome image The light emitting device according to the present invention can also be used for the device.

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

The light emitting device of the present invention is also used as a display device for various electronic devices. Examples of electronic devices to which the light emitting device of the present invention is applied include portable personal computers, mobile phones, personal digital assistants (PDAs), digital still cameras,
TV, video camera, car navigation device, pager, electronic notebook, electronic paper,
Examples include a calculator, a word processor, a workstation, a videophone, a POS terminal, a printer, a scanner, a copying machine, a video player, and a device equipped with a touch panel.

It is a block diagram which shows the specific form of the light-emitting device which concerns on this invention. It is a flowchart which shows operation | movement of a control part. It is a graph for demonstrating a spot area | region. It is a conceptual diagram for demonstrating reduction of a gradation nonuniformity. It is a block diagram which shows the structure of the light-emitting device which concerns on a modification. It is sectional drawing which shows the specific form of the electronic device (image forming apparatus) which concerns on this invention.

Explanation of symbols

10: Light emitting device, 20: Head module, 22: Optical head, E: Light emitting element, 2
4 ... Drive circuit, 26 ... ROM, 30 ... Control board, 32 ... Controller, 321,
322, 323, 341, 342, 343 ... buffer, 325 ... input / output unit, 326 ...
Control unit, 327... Correction unit, Aa, Ab, Ac... Correction value, G... Image data, S.

Claims (5)

A plurality of light emitting elements corresponding to the pixels constituting the image and emitting light to the irradiated object by supplying electric energy;
First storage means for storing a first correction value selected for each of the light emitting elements so as to suppress a difference in light quantity of each of the plurality of light emitting elements when predetermined electric energy is supplied;
The light emission is performed so that the difference in the form of the spot region where the emitted light from each of the plurality of light emitting elements supplied with predetermined electrical energy of the surface of the irradiated object reaches with an intensity exceeding a predetermined value is suppressed. Second storage means for storing a second correction value selected for each element;
Designating means for designating the first mode or the second mode for each of the plurality of regions into which the image is divided;
For each pixel in the region in which the designation unit designates the first mode, electric energy corresponding to the image data of each pixel and the first correction value of the light emitting element is supplied to each of the plurality of light emitting elements, Drive for supplying electric energy corresponding to the image data of each pixel and the second correction value of each light emitting element to each of the plurality of light emitting elements for each pixel in the region in which the designation unit designates the second mode And a light emitting device. The image is formed by arranging lines composed of a plurality of pixels arranged in a first direction corresponding to the light emitting elements in a second direction intersecting the first direction,
The light-emitting device according to claim 1, wherein the designation unit designates a first mode or a second mode for each region obtained by dividing the image into a predetermined number of lines. The light-emitting device according to claim 2, wherein the designating unit designates one of the first mode and the second mode for each odd-numbered line and designates the other of the first mode and the second mode for each even-numbered line. .   The electronic device which comprises the light-emitting device in any one of Claims 1-3. Each of a plurality of light emitting elements corresponding to pixels constituting an image is an image processing device of a light emitting device driven by supplying electric energy according to image data,
First storage means for storing a first correction value selected for each of the light emitting elements so as to suppress a difference in light quantity of each of the plurality of light emitting elements when predetermined electric energy is supplied;
The light emission is performed so that the difference in the form of the spot region where the emitted light from each of the plurality of light emitting elements supplied with predetermined electrical energy of the surface of the irradiated object reaches with an intensity exceeding a predetermined value is suppressed. Second storage means for storing a second correction value selected for each element;
Designating means for designating the first mode or the second mode for each of the plurality of regions into which the image is divided;
The designating means corrects the image data of each pixel belonging to the area for which the first mode is designated according to the first correction value stored in the first storage means, and then outputs the corrected data to the light emitting device. A correction unit that corrects the image data of each pixel belonging to the region in which the second mode is designated according to the second correction value stored in the second storage unit, and then outputs the corrected image data to the light emitting device. Processing equipment.

Images