JP2008039796A - Electro-optical device, drive circuit, and electronic device - Google Patents

Abstract

The present invention suppresses unevenness in the amount of light of each electro-optic element over a long period of time.
An electro-optic element E is controlled in gradation according to a drive signal Xi. The unit circuit U includes a holding circuit 261, a selection circuit 263, and a drive unit DR. The holding circuit 261 holds correction values Ca [i] and Cb [i] for the electro-optic element E. The selection circuit 263 selects one of the correction values Ca [i] and Cb [i] held by the holding circuit 261. The drive unit DR generates a drive signal Xi based on the gradation value designated for the electro-optic element E and the correction value C [i] selected by the selection circuit 263.
[Selection] Figure 6

Description

  The present invention relates to a technique for correcting gradation of an electro-optical element such as a light emitting element.

In an electro-optical device in which a plurality of electro-optical elements are arranged, gradation unevenness due to an error in characteristics of each electro-optical element or an active element that drives the electro-optical element (difference from a design value or variation between elements). Is a problem. Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for suppressing unevenness in gradation of each electro-optic element based on correction data stored in a storage circuit such as a ROM.
Japanese Patent No. 3215748

  Incidentally, the optimum correction value applied to the gradation correction of each electro-optical element differs depending on the characteristics of the image output by the electro-optical device. For example, when outputting an image such as a diagram or a character, a correction value selected so that the resolution is preferentially maintained is preferable, but when outputting an image such as a natural image, a gradation is set. A correction value to be prioritized is preferable. However, in the technique of Patent Document 1, since the correction value created for each electro-optic element is fixedly applied regardless of the characteristics of the image, it is difficult to perform appropriate correction according to the characteristics of the image. There is.

  In order to solve the above problems, it is also possible to adopt a configuration in which correction values corresponding to image characteristics are sequentially transferred to the electro-optical device and applied to the correction of gradation of each electro-optical element. is there. However, in this configuration, since it is necessary to transfer the correction values of all the electro-optic elements to the electro-optic device for each image, the amount of data transfer is increased and the operation speed of the drive circuit is required to be increased. As a result, problems such as an increase in size of the drive circuit and an increase in manufacturing cost may occur. In view of the above circumstances, an object of the present invention is to solve the problem of appropriately correcting the gradation of each electro-optic element while suppressing the amount of data transferred to the electro-optic device.

  In order to solve the above problems, an electro-optical device according to the present invention includes a plurality of electro-optical elements whose gradation is controlled according to a drive signal, and a plurality of unit circuits corresponding to each electro-optical element. Each of the plurality of unit circuits includes a holding unit that holds a plurality of correction values, a selection unit that selects any one of the plurality of correction values held by the holding unit, and a gradation value specified for the electro-optical element. And a driving unit that generates a driving signal based on the correction value selected by the selection unit.

  According to the above configuration, any one of a plurality of correction values is individually selected for each electro-optical element and used for generating a drive signal. Therefore, a configuration in which one correction value is fixedly used or Compared with a configuration in which a combination of correction values for a plurality of electro-optical elements is fixed, the gradation of each electro-optical element can be corrected appropriately (for example, according to the characteristics of the image output from the electro-optical device). It is. Further, since the plurality of correction values are held in the holding unit, it is not necessary to transfer each correction value to the electro-optical device as needed. Accordingly, the amount of data transferred to the electro-optical device is reduced.

  The first aspect of the electro-optical device according to the present invention includes acquisition means (for example, the I / F circuit 28 in FIG. 1) that acquires gradation data and selection data for each electro-optical element. In the unit circuit corresponding to the selection circuit, the selection unit selects the correction value specified by the selection data acquired by the acquisition unit for the electro-optical element from the plurality of correction values held by the holding unit, and the drive unit is the acquisition unit. Generates a drive signal based on the gradation data acquired for the electro-optic element and the correction value selected by the selection means. According to the above aspect, there exists an advantage that the process and structure which generate | occur | produce gradation data and selection data are simplified. A specific example of this aspect will be described later as the first embodiment.

  A second aspect of the electro-optical device according to the present invention includes acquisition means (for example, the I / F circuit 28 in FIG. 1) that acquires image data of a plurality of bits for each of a plurality of electro-optical elements. In the unit circuit corresponding to the optical element, the selection unit is a numerical value to which the numerical value of the image data acquired by the acquisition unit for the electro-optical element from among a plurality of numerical values grouped by a plurality of numerical values represented by a plurality of bits. A correction value corresponding to the group is selected for the electro-optical element, and the drive unit generates a drive signal based on the image data acquired by the acquisition unit for the electro-optical element and the correction value selected by the selection unit. According to the above aspect, since the correction value is selected according to the numerical value group to which the numerical value of the image data belongs, it is not necessary to separately prepare data for specifying the correction value. Therefore, the amount of image data can be reduced.

  The electro-optical device according to the invention includes an electro-optical element whose gradation is controlled according to a drive signal, a holding unit that holds a plurality of correction values for the electro-optical element, and a plurality of corrections that the holding unit holds. Selection means for selecting one of the values, and drive means for generating a drive signal based on the gradation value designated for the electro-optic element and the correction value selected by the selection means.

  According to the above configuration, since any one of the plurality of correction values is selectively used for generating the drive signal, each electro-optic is compared with the conventional configuration in which one correction value is fixedly used. It is possible to correct the gradation of the element appropriately (for example, according to the characteristics of the image output from the electro-optical device). Further, since the plurality of correction values are held in the holding unit, it is not necessary to transfer each correction value to the electro-optical device as needed. Accordingly, the amount of data transferred to the electro-optical device is reduced.

  An electro-optical device according to a specific aspect of the invention includes an acquisition unit that acquires image data of a plurality of bits, and the selection unit is a plurality of numerical values grouped by dividing a plurality of numerical values represented by the plurality of bits. Among them, the correction value corresponding to the numerical value group to which the numerical value of the image data acquired by the acquisition unit belongs is selected, and the drive unit drives the drive signal based on the image data acquired by the acquisition unit and the correction value selected by the selection unit. Is generated. According to the above aspect, since the correction value is selected according to the numerical value group to which the numerical value of the image data belongs, it is not necessary to separately prepare data for specifying the correction value. Therefore, the data amount of image data can be reduced.

  By the way, the total number m of numerical values expressed by a plurality of bits, the number s of gradation values other than zero, and the number j of correction values held for the electro-optic element satisfy “m <j × s + 1”. In the case of satisfying, all combinations of gradation values including zero and correction values cannot be designated by image data. Therefore, the plurality of numerical value groups are divided into a first numerical value group and a second numerical value group, each including a separate numerical value, and the second numerical value group is a plurality of gradations specified by each numerical value of the first numerical value group. Of the values, an aspect composed of numerical values for designating each of some of the gradation values on the high gradation side is suitably employed. According to the above aspect, since the numerical value included in the first numerical value group and not included in the second numerical value group corresponds to the gradation value on the low gradation side, it has an influence on the correction of the gradation of the electro-optical element. It is possible to reduce the number of bits of image data while suppressing sufficiently.

  The configuration and method for generating the drive signal based on the gradation value and the correction value are arbitrary, but the current value corresponding to the correction value over the pulse width corresponding to the gradation value specified for the electro-optic element A configuration in which the drive signal generates the drive signal is particularly suitable. According to the above aspect, for example, the configuration of the driving unit is simplified as compared with a configuration in which only one of the pulse width and the current value of the drive signal is adjusted according to the gradation value and the correction value. Note that the drive signal may be a voltage signal.

  The electro-optical device according to the invention is used in various electronic apparatuses. A typical example of the electronic apparatus according to the present invention is an electrophotographic image forming apparatus in which the electro-optical device according to each of the above embodiments is used for exposure of an image carrier such as a photosensitive drum. This image forming apparatus is realized by adding an image carrier on which a latent image is formed by exposure, the electro-optical device of the present invention that exposes the image carrier, and a developer (for example, toner) to the latent image on the image carrier. And a developing unit for forming an image. However, the use of the electro-optical device according to the present invention is not limited to the exposure of the image carrier. For example, in an image reading apparatus such as a scanner, the electro-optical device according to the present invention can be used for illuminating a document. The image reading apparatus includes an electro-optical device according to each of the above aspects, and a light-receiving device (for example, a CCD (Charge Coupled Device) element that converts light emitted from the electro-optical device and reflected by a reading target (original) into an electric signal. Etc.). Furthermore, an electro-optical device in which electro-optical elements are arranged in a matrix is also used as a display device for various electronic devices such as a personal computer and a mobile phone.

  The present invention is also specified as a drive circuit used in the electro-optical device according to each of the above aspects. The drive circuit according to the present invention is a circuit that outputs a drive signal for controlling the gradation of the electro-optic element, the holding means for holding a plurality of correction values for the electro-optic element, and the plurality of corrections held by the holding means. Selection means for selecting one of the values, and drive means for generating a drive signal based on the gradation value designated for the electro-optic element and the correction value selected by the selection means. With the above configuration, the same operation and effect as the electro-optical device according to the present invention can be obtained.

<A: First Embodiment>
FIG. 1 is a block diagram showing the configuration of the electro-optical device according to the first embodiment of the invention. The electro-optical device H is employed in an electrophotographic image forming apparatus as an exposure device (line head) that exposes a photosensitive drum. As shown in FIG. 1, the electro-optical device H includes a head module 20 that emits a light beam according to a desired image toward a photosensitive drum, and a controller 30 that controls the operation of the head module 20. The head module 20 and the controller 30 are electrically connected through, for example, a flexible wiring board (not shown).

  The head module 20 includes a light emitting unit 22, a drive circuit 24, a storage unit 26, and an I / F (interface) circuit 28. In the light emitting unit 22, n (n is a natural number) electro-optic elements E are arranged in a single row or a plurality of rows along the main scanning direction. The electro-optical element E of the present embodiment is an organic light-emitting diode element in which a light-emitting layer of an organic EL (Electroluminescence) material is interposed between an anode and a cathode that face each other.

  The drive circuit 24 is means for driving each electro-optical element E, and includes n unit circuits U each corresponding to an individual electro-optical element E. The drive circuit 24 may be composed of one or a plurality of IC chips, and a number of active elements (for example, a semiconductor layer formed of low-temperature polysilicon) formed on the surface of the substrate together with the electro-optical elements E. Thin film transistor).

  The unit circuit U in the i-th stage (i is an integer satisfying 1 ≦ i ≦ n) generates the drive signal Xi and outputs it to the i-th electro-optical element E. FIG. 2 is a conceptual diagram illustrating the waveform of the drive signal Xi generated by the drive circuit 24 for each gradation value G designated by the electro-optic element E. As shown in the figure, the driving signal Xi maintains the current IDR over the pulse width corresponding to the gradation value G from the start point of one horizontal scanning period H, and the current value in the remaining period of the horizontal scanning period H. Is a current signal that becomes zero. The horizontal scanning period H is a period serving as a unit for exposing the photosensitive drum (that is, forming a latent image corresponding to the image in the row) in accordance with the gradation value G of each pixel constituting one row of the image. is there. As shown in FIG. 2, the horizontal scanning period H is divided into four sub-periods T (T1 to T4). Each of the sub periods T1 to T4 includes four unit periods u. The unit period u is a period that becomes a unit (step size) of change in the pulse width of the drive signal Xi. For example, when “10” is designated as the gradation value G, the current value of the drive signal Xi is the current IDR over the time length (10u) corresponding to ten unit periods u from the start point of the horizontal scanning period H. It is maintained and becomes zero in the remaining period (6u).

  The storage unit 26 in FIG. 1 stores the correction coefficients Aa [1] to Aa [n] and the correction coefficients Ab [1] to Ab [n] for the n electro-optical elements E constituting the light emitting unit 22. It is. A nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory) is suitably used as the storage unit 26. The correction coefficients Aa [1] to Aa [n] and the correction coefficients Ab [1] to Ab [n] are written in the storage unit 26 in the process of manufacturing the electro-optical device H. When the electro-optical device H is turned on, the correction coefficients Aa [1] to Aa [n] and the correction coefficients Ab [1] to Ab [n] are read from the storage unit 26 and supplied to the controller 30. The

  Each of the correction coefficients Aa [i] and Ab [i] is a numerical value for correcting the current IDR of the drive signal Xi. The current IDR of the drive signal Xi is set to either a correction value Ca [i] corresponding to the correction coefficient Aa [i] or a correction value Cb [i] corresponding to the correction coefficient Ab [i]. Correction coefficients Aa [i] and Ab [i] corresponding to one electro-optic element E are selected independently. For example, the correction coefficients Aa [1] to Aa [n] are set for each electro-optical element E while preferentially maintaining the resolution of the latent image formed on the photosensitive drum (and the visible image formed on the paper). It is selected so that uneven gradation is suppressed. On the other hand, the correction coefficients Ab [1] to Ab [n] are such that gradation unevenness of each electro-optic element E is suppressed while preferentially maintaining the gradation of the latent image formed on the photosensitive drum. Selected.

  As shown in FIG. 1, the controller 30 includes a RAM 31, a correction value setting unit 33, and a control unit 35. The correction coefficients Aa [1] to Aa [n] and the correction coefficients Ab [1] to Ab [n] read from the storage unit 26 when the power is turned on are stored in the RAM 31. The correction value setting unit 33 is a means for calculating a correction value Ca [i] corresponding to the correction coefficient Aa [i] and a correction value Cb [i] corresponding to the correction coefficient Ab [i]. For example, the correction value setting unit 33 calculates the multiplication value of the initial value I0 of the current value of the current IDR and the correction coefficient Aa [i] as the correction value Ca [i], and also calculates the initial value I0 and the correction coefficient Ab [i]. Is calculated as a correction value Cb [i]. The correction values Ca [i] and Cb [i] are set in the i-th unit circuit U as candidates for the current IDR of the drive signal Xi. Each of the correction values Ca [i] and Cb [i] is, for example, 6-bit digital data.

  The control unit 35 sequentially outputs image data D supplied for each electro-optical element E from various host devices such as a CPU of the image forming apparatus to the head module 20. Image data D corresponding to one electro-optic element E is sequentially supplied to the head module 20 with the sub-period T as a cycle.

  FIG. 3 is a chart for explaining the relationship between the numerical value of the image data D and the operation of the drive circuit 24. As shown in the figure, the image data D is composed of selection data DS and gradation data DG. The selection data DS included in the image data D of the i-th stage electro-optical element E is 1-bit data designating one of the correction values Ca [i] and Cb [i]. The gradation data DG is 3-bit data that specifies the gradation of each electro-optic element E.

  The gradation data DG included in the image data D of the i-th electro-optical element E designates the pulse width W of the drive signal Xi in one sub-period T (T1 to T4) as the number of unit periods u. In the gradation data DG in each of the sub-periods T1 to T4, the pulse width of the drive signal Xi in one horizontal scanning period H corresponds to the gradation value G from the start point of the horizontal scanning period H as shown in FIG. It is selected to be a continuous period until the length of time has elapsed. In FIG. 2, the numerical value (decimal notation) of the gradation data DG in each of the sub-periods T1 to T4 is written together for each gradation value G. As shown in FIGS. 2 and 3, for example, when the gradation value G designated for the i-th electro-optic element E is “10”, the gradation data DG in each of the sub-periods T1 and T2 is a unit. Four periods (4u) of the period u are set to a numerical value “100” that designates the pulse width W of the drive signal Xi, and the gradation data DG in the sub-period T3 is set as the pulse width W of the two unit periods u. The specified numerical value “010” is set. Further, the gradation data DG in the sub-period T4 is a numerical value “000” designating zero. As described above, in the present embodiment, the pulse width of the drive signal Xi in the horizontal scanning period H is specified in a distributed manner in each of the four sub-periods T1 to T4.

  Next, FIG. 4 is a flowchart showing an outline of processing executed by the controller 30. When the power of the image forming apparatus is turned on, the control unit 35 corrects the correction coefficients Aa [1] to Aa [n] and the correction coefficients Ab [1] to Ab [n] stored in the storage unit 26 of the head module 20. Are read into the RAM 31 (step S10). Next, the control unit 35 sets the correction values Ca [1] to Ca [n] in the drive circuit 24 based on the correction coefficients Aa [1] to Aa [n] (step S20), and the correction coefficient Ab [ A process of setting correction values Cb [1] to Cb [n] in the drive circuit 24 based on 1] to Ab [n] (step S30) is executed.

  FIG. 5 is a flowchart showing the specific contents of step S20. As shown in the figure, the control unit 35 initializes a variable k for identifying one electro-optical element E (or unit circuit U) to “1” (step S21). Next, the control unit 35 reads the correction coefficient Aa [k] read from the storage unit 26 in step S10 from the RAM 31 (step S22). The correction value setting unit 33 calculates the correction value Ca [k] by a predetermined calculation according to the correction coefficient Aa [k] read by the control unit 35 in step S22 (step S23). The control unit 35 outputs the correction value Ca [k] calculated by the correction value setting unit 33 to the head module 20 (step S24). The correction value Ca [k] is supplied to the kth unit circuit U via the I / F circuit 28.

  Next, the control unit 35 determines whether or not the variable k is equal to the total number n of the electro-optic elements E (that is, whether or not the correction values Ca [1] to Ca [n] are set) (step S25). . When the variable k is less than the total number n, the control unit 35 updates the variable k (step S26), and repeats the processing from step S22 to step S25 for the updated variable k. When the variable k reaches the total number n (step S25: YES), the control unit 35 shifts the processing to step S30 in FIG.

  The process of step S30 is the same as the process of FIG. 5 except that the correction coefficient Aa [k] and the correction value Ca [k] are changed to the correction coefficient Ab [k] and the correction value Cb [k]. Therefore, detailed description of the process of step S30 is omitted. When step S30 is completed, correction values Ca [1] to Ca [n] and correction values Cb [1] to Cb [n] are set in the drive circuit 24. When the above processing is completed, the control unit 35 starts transferring the image data D to the head module 20 (step S40 in FIG. 4).

  The I / F circuit 28 in FIG. 1 is means for sequentially acquiring image data D output from the control unit 35 for each electro-optical element E. The I / F circuit 28 of this embodiment separates the image data D into gradation data DG and selection data DS and outputs each to the drive circuit 24.

  Next, a specific configuration of each unit circuit U that constitutes the drive circuit 24 will be described with reference to FIG. Although only the i-th stage unit circuit U is shown in the figure, all the unit circuits U have the same configuration. As shown in FIG. 6, each of the n unit circuits U includes a holding circuit 261, a selection circuit 263, and a drive unit DR.

  The holding circuit 261 is means (for example, a register) that holds the correction values Ca [i] and Cb [i] calculated by the correction value setting unit 33. The selection circuit 263 selects and outputs one of the correction values Ca [i] and Cb [i] held by the holding circuit 261 according to the selection data DS output by the I / F circuit 28. As shown in FIG. 3, the selection circuit 263 selects the correction value Ca [i] if the selection data DS is “0”, and selects the correction value Cb [i] if the selection data DS is “1”. To do. The selection data DS corresponding to each electro-optical element E specifies a correction value Ca [i] when the pixel in charge of the electro-optical element E belongs to an image area such as a diagram or a character (DS = 0). When the pixel in charge of the electro-optical element E belongs to an image region such as a natural image or a photograph, the correction value Cb [i] is designated (DS = 1) and is generated by the host device.

  The drive unit DR in FIG. 6 generates a drive signal Xi corresponding to the gradation data DG and the correction value C [i] (Ca [i] or Cb [i]) selected by the selection circuit 263. The drive unit DR of the present embodiment is means for generating a drive signal Xi that becomes a current IDR according to the correction value C [i] over a pulse width corresponding to the gradation data DG. The current generation circuit 265 and the pulse control circuit 267. The current generation circuit 265 is means (for example, a current output type D / A converter) that generates a current IDR according to the correction value C [i]. The pulse control circuit 267 outputs the current IDR over the number of unit periods u specified by the gradation data DG in one sub-period T, and stops outputting the current IDR in the remaining period of the sub-period T. .

  As described above, in the present embodiment, any one of the two types of correction values Ca [i] and Cb [i] is selectively used for generating the drive signal Xi, and thus is fixedly set. Compared with the conventional configuration in which the current IDR is corrected based on the correction value, the gradation of each electro-optical element E can be appropriately corrected. For example, the current IDR is corrected so that the resolution is preferentially maintained for the pixels in the area where the diagram or character is arranged, and the number of gradations is preferentially maintained for images including natural images and photographs. The current IDR is corrected as described above.

  In the present embodiment, since the correction values Ca [i] and Cb [i] are transferred and held to the drive circuit 24 prior to the actual driving of each electro-optical element E, the electro-optical element E is being driven. In addition, it is not necessary to transfer the correction values Ca [i] and Cb [i] from the controller 30 to the head module 20. That is, the amount of data transferred to the head module 20 is reduced. Therefore, compared with the configuration in which the correction values Ca [i] and Cb [i] are transferred to the head module 20 during driving of the electro-optical element E, the operation speed required for the drive circuit 24 is reduced. Thus, there is an advantage that the drive circuit 24 can be downsized and the manufacturing cost can be reduced.

<B: Second Embodiment>
Next, a second embodiment of the present invention will be described. In the first embodiment, the configuration in which the bit different from the gradation data DG is the selection data DS is exemplified. On the other hand, the image data D of this embodiment does not include independent selection data DS. In the present embodiment, elements having the same functions and functions as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

  FIG. 7 is a chart for explaining the relationship between the numerical value of the image data D and the operation of the drive circuit 24. As shown in the figure, the image data D of the present embodiment is 3-bit data. The I / F circuit 28 generates gradation data DG and selection data DS based on the image data D sequentially supplied from the controller 30. As in the first embodiment, the gradation data DG is supplied to the pulse control circuit 267, and the selection data DS is supplied to the selection circuit 263.

  Numerical values represented by the image data D are divided into a plurality of groups (hereinafter referred to as “numerical value groups”) so as not to overlap each other. As shown in FIG. 7, the numerical value of the image data D in this embodiment includes a numerical value group G1 including five numerical values from “000” to “100” and three types from “101” to “111”. It is divided into a numerical group G2 including numerical values. The I / F circuit 28 generates selection data DS corresponding to the numerical value group to which the numerical value of the image data D belongs. That is, when the numerical value of the image data D belongs to the numerical value group G1, the I / F circuit 28 generates selection data DS (numerical value “0”) instructing selection of the correction value Ca [i], and the image data D If the numerical value belongs to the numerical value group G2, selection data DS (numerical value “1”) for instructing selection of the correction value Cb [i] is generated. According to the above configuration, the number of bits of the image data D can be reduced (4 bits → 3 bits) as compared with the first embodiment in which the gradation data DG and the selection data DS are individually set. Become.

By the way, if the number of steps (except for zero) of the pulse width W of the drive signal Xi in each sub-period T is “s” and the number of correction values prepared for one electro-optic element E is “j”, the drive The total number CB of combinations of the pulse width W of the signal Xi and the correction value is:
CB = j × s + 1
It is expressed. "1" on the right side means a case where the pulse width of the drive signal Xi is zero (if the pulse width is zero, the correction value is irrelevant). The pulse width W of the drive signal Xi in each sub-period T is set to any one of “1u” to “4u” or zero as in the first embodiment. Therefore, the number of steps s is “4”. Similarly to the first embodiment, since two types of correction values Ca [i] and Cb [i] are stored in the holding circuit 261 of the unit circuit U, the number j of correction values is “2”. Therefore, the total number CB is “9”.

  Now, for example, when the image data D is 4 bits, the total number m of the numerical values represented by the image data D is “16” (m> C), and therefore all of the pulse width and the correction value of the drive signal Xi. Can be uniquely specified by the image data D. On the other hand, since the total number m of numerical values represented by the 3-bit image data D is “8” as in this embodiment (m <C), all numerical values represented by the image data D are used. Even so, it is insufficient to specify all combinations of the pulse width W of the drive signal Xi and the correction value.

  Therefore, in the present embodiment, all the numerical values that the gradation data DG can take correspond to the numerical values of the numerical value group G1, while the numerical values of the numerical value group G2 include some numerical values that the gradation data DG can take. Only correspond. For example, when the five-step pulse width from “0” to “4u” is designated by the gradation data DG, each gradation data DG is represented by five numerical values (“000” to “100”) in the numerical value group G1. One-to-one correspondence. On the other hand, three numerical values (“101” to “111”) belonging to the numerical value group G2 are made to correspond to some numerical values on the high gradation side among all numerical values that the gradation data DG can take. For example, the maximum value “111” of the numerical group G2 is associated with gradation data DG (numerical value “100”) that specifies the pulse width “4u” of the maximum gradation, and the numerical value “110” of the numerical group G2 is associated with the numerical value “110”. The gradation data DG (numerical value “011”) designating the pulse width “3u” is associated, and the numerical value “101” of the numerical value group G2 is associated with the gradation data DG (numerical value “10”) specifying the pulse width of “2u”. 010 ").

  As described above, when the image data D and the gradation data DG are associated with each other, the pulse width such as “0” or “1u” is specified only by the numerical value of the numerical value group G1. Therefore, the correction value Ca [i] is selected in the unit circuit U whose pulse width specified by the gradation data DG is “1u”, and the correction value Cb [i] is not selected. However, since the gradation data DG that is not associated with the numerical value group G2 has a low gradation, the influence of the correction value Cb [i] not being selected is sufficiently suppressed. This effect will be described in detail as follows.

  For example, suppose a case in which correction (correction using the correction value Cb [i]) giving priority to the gradation is executed for the electro-optic element E in which “13” is specified as the gradation value G in FIG. In each of the periods T1 to T3, by setting the image data D to “111” of the numerical value group G2, selection data DS for specifying the correction value Cb [i] and gradation data for specifying the pulse width “4u” DG can be supplied to the unit circuit U. On the other hand, since the image data D is set to “001” of the numerical value group G1 in the period T4, the selection data DS is the correction value Ca [i] even though the desired pulse width “1u” can be set. It becomes the numerical value “0” for designating. However, the current IDR is set to the correction value Ca [i] of the total pulse width over “13u” is only “1u”, and the current IDR in the remaining “12u” is the desired correction value Cb. Since it is set to [i], the influence of the correction value Ca [i] is so small that it can be ignored.

  As described above, in this embodiment, the amount of data transferred to the head module 20 is reduced by reducing the number of bits of the image data D while sufficiently suppressing the influence on the gradation correction of each electro-optical element E. This can be reduced as compared with the first embodiment. However, according to the configuration in which the gradation data DG and the selection data DS are individually set as in the first embodiment, there is an advantage that the configuration and processing for generating the image data D are simplified.

<C: Modification>
Various modifications can be made to each of the above embodiments. An example of a specific modification is as follows. In addition, you may combine each following aspect suitably.

(1) Modification 1
In each of the above embodiments, the configuration in which the current IDR of the drive signal Xi is corrected to the correction value C [i] and the pulse width of the drive signal Xi is controlled according to the gradation value G (gradation data DG) is exemplified. However, the control target according to the gradation value G and the correction target according to the correction value C [i] are appropriately changed. For example, the current IDR of the drive signal Xi may be controlled according to the gradation value G, and the pulse width of the drive signal Xi may be controlled according to the correction value C [i] selected by the selection circuit 263. Furthermore, only one of the current IDR and the pulse width of the drive signal Xi may be controlled according to both the gradation value G and the correction value C [i].

  In the configuration using the voltage-driven electro-optic element E whose gradation changes with application of voltage, the drive signal Xi is a voltage signal. In this configuration, the voltage value of the drive signal Xi may be controlled according to the gradation value G and the correction value C [i]. As exemplified above, the electro-optical device H according to the preferred embodiment of the present invention is based on the gradation value G of the electro-optical element E and the correction value C [i] selected by the selection circuit 263, so that the drive signal Xi. A configuration in which is generated is sufficient.

(2) Modification 2
In each of the above embodiments, the configuration in which the correction value C [i] specifies the current value of the current IDR is exemplified, but the content of the correction value C [i] is not limited to this. For example, a configuration in which the correction value C [i] specifies the pulse width of the drive signal Xi as exemplified in the first modification is also employed. In the above description, the configuration in which the correction values Ca [i] and Cb [i] after correction according to the correction coefficients Aa [i] and Ab [i] are set in the drive circuit 24 is illustrated. However, the correction coefficient Aa [ A configuration may be adopted in which i] and Ab [i] are held in the holding circuit 261 as correction values Ca [i] and Cb [i]. The unit circuit U having this configuration includes means for calculating the current value of the current IDR based on the correction value C [i] (Aa [i] or Ab [i]) output from the selection circuit 263 (for example, a correction value setting unit). 33 is installed).

(3) Modification 3
The number of correction values C [i] prepared for one electro-optic element E is arbitrary. For example, the selection circuit 263 may select one of three or more types of correction values C [i] held in the holding circuit 261. Therefore, the number of numerical groups obtained by dividing the numerical values of the image data D in the second embodiment is also arbitrary. Furthermore, in the second embodiment, the method of dividing the numerical value of the image data D into a plurality of numerical value groups is appropriately changed. For example, among the plurality of numerical values expressed by the image data D, odd numbers may be classified into the numerical value group G1, and even numbers may be classified into the numerical value group G2. In the above embodiment, the drive signal Xi is controlled in units of sub-periods T obtained by dividing the horizontal scanning period H. However, the division of the horizontal scanning period H is not always necessary.

(4) Modification 4
In each of the above embodiments, the configuration in which the storage unit 26 is mounted on the head module 20 is illustrated, but a configuration in which the storage unit 26 is mounted on the controller 30 is also employed. Since the correction coefficients Aa [i] and Ab [i] are numerical values corresponding to the characteristics of each electro-optical element E, when mass-producing the electro-optical device H in which the storage unit 26 is mounted on the controller 30, It is necessary to strictly manage the correspondence between the head module 20 and the controller 30 for each electro-optical device H. On the other hand, in the configuration of FIG. 1, since the storage unit 26 is installed in the head module 20 together with the light emitting unit 22, even if the characteristics of each electro-optical element E are different for each electro-optical device H, It is possible to employ a common controller 30 for all the electro-optical devices H. That is, according to the configuration of FIG. 1, it is unnecessary to manage the correspondence between the head module 20 and the controller 30, so that there is an advantage that the manufacturing process of the electro-optical device H is simplified.

(5) Modification 5
The organic light emitting diode element is only an example of the electro-optical element E. The electro-optic element applied to the present invention is distinguished from a self-light-emitting type that emits light itself and a non-light-emitting type (for example, a liquid crystal element) that changes the transmittance of external light, or a current-driven type that is driven by supplying current And the voltage driven type driven by voltage application are unquestionable. For example, inorganic EL elements, field emission (FE) elements, surface-conduction electron (SE) elements, ballistic electron surface emitting (BS) elements, and light emitting diode (LED) elements Various electro-optical elements such as a liquid crystal element, an electrophoretic element, and an electrochromic element can be used in the present invention.

<D: Application example>
A specific form of an electronic apparatus (image forming apparatus) using the electro-optical device according to the invention will be described.
FIG. 8 is a cross-sectional view illustrating a configuration of an image forming apparatus employing the electro-optical device H according to each of the above embodiments. The image forming apparatus is a tandem type full-color image forming apparatus, and the four electro-optical devices H (HK, HC, HM, and HY) according to the above embodiment and four photosensitive devices corresponding to the electro-optical devices H are used. Body drum 70 (70K, 70C, 70M, 70Y). One electro-optical device H is disposed so as to face the image forming surface (outer peripheral surface) of the corresponding photosensitive drum 70. Note that the subscripts “K”, “C”, “M”, and “Y” of each symbol are used for forming each visible image of black (K), cyan (C), magenta (M), and yellow (Y). Means.

  As shown in FIG. 8, an endless intermediate transfer belt 72 is wound around the driving roller 711 and the driven roller 712. The four photosensitive drums 70 are arranged around the intermediate transfer belt 72 at a predetermined interval from each other. Each photosensitive drum 70 rotates in synchronization with driving of the intermediate transfer belt 72.

  In addition to the electro-optical device H, a corona charger 731 (731K, 731C, 731M, 731Y) and a developing unit 732 (732K, 732C, 732M, 732Y) are arranged around each photosensitive drum 70. The corona charger 731 uniformly charges the image forming surface of the photosensitive drum 70 corresponding thereto. Each electro-optical device H exposes this charged image forming surface to form an electrostatic latent image. Each developing device 732 forms a visible image (visible image) on the photosensitive drum 70 by attaching a developer (toner) to the electrostatic latent image.

  As described above, the visible images of the respective colors (black, cyan, magenta, yellow) formed on the photosensitive drum 70 are sequentially transferred (primary transfer) to the surface of the intermediate transfer belt 72 to form a full-color visible image. Is done. Four primary transfer corotrons (transfer devices) 74 (74K, 74C, 74M, and 74Y) are arranged inside the intermediate transfer belt 72. Each primary transfer corotron 74 electrostatically attracts a visible image from the corresponding photosensitive drum 70, thereby developing a visible image on the intermediate transfer belt 72 that passes through the gap between the photosensitive drum 70 and the primary transfer corotron 74. Transcript.

  The sheets (recording material) 75 are fed one by one from the paper feed cassette 762 by the pickup roller 761 and conveyed to the nip between the intermediate transfer belt 72 and the secondary transfer roller 77. The full-color visible image formed on the surface of the intermediate transfer belt 72 is transferred (secondary transfer) to one side of the sheet 75 by the secondary transfer roller 77 and is fixed to the sheet 75 by passing through the fixing roller pair 78. . The paper discharge roller pair 79 discharges the sheet 75 on which the visible image is fixed through the above steps.

  Since the image forming apparatus exemplified above uses an organic light emitting diode element as a light source (exposure means), the apparatus is made smaller than a configuration using a laser scanning optical system. Note that the electro-optical device H can be applied to an image forming apparatus having a configuration 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 electro-optical device H can also be used as the device.

  The use of the electro-optical device H is not limited to the exposure of the image carrier. For example, the electro-optical device H is employed in an image reading device as an illumination device that irradiates light to a reading target such as a document. 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).

  Further, the electro-optical device H in which the electro-optical elements E are arranged in a matrix is also used as a display device for various electronic devices. Examples of the electronic device to which the present invention is applied include a portable personal computer, a mobile phone, a personal digital assistant (PDA), a digital still camera, a television, a video camera, a car navigation device, a pager, and an electronic notebook. , Electronic paper, calculators, word processors, workstations, videophones, POS terminals, printers, scanners, copiers, video players, devices with touch panels, and the like.

1 is a block diagram illustrating a configuration of an electro-optical device according to a first embodiment. It is a conceptual diagram which shows the relationship between the gradation value designated to the electro-optic element, and the waveform of a drive signal. It is a chart which shows the relationship between the structure of image data, and operation | movement of a drive circuit. It is a flowchart for demonstrating the procedure of the process by a controller. It is a flowchart for demonstrating the procedure which sets a correction value to a drive circuit. It is a block diagram which shows the structure of a unit circuit. 10 is a chart showing a relationship between the structure of image data and the operation of a drive circuit in the second embodiment. It is sectional drawing which shows one form (image forming apparatus) of an electronic device.

Explanation of symbols

H: Electro-optical device, 20: Head module, 22: Light emitting unit, E: Electro-optical element, 24: Drive circuit, U: Unit circuit, 261: Holding circuit, 263 ... Selection circuit, DR …… Drive unit, 265 …… Current generation circuit, 267 …… Pulse control circuit, 26 …… Storage unit, 28 …… I / F circuit, 30 …… Controller, 31 …… RAM, 33 …… Correction value setting Part, 35... Control part.

Claims (9)

A plurality of electro-optic elements whose gradations are controlled in accordance with a drive signal;
A plurality of unit circuits corresponding to the electro-optical elements,
Each of the plurality of unit circuits is
Holding means for holding a plurality of correction values;
Selecting means for selecting any of a plurality of correction values held by the holding means;
An electro-optical device, comprising: a drive unit that generates the drive signal based on a gradation value designated for the electro-optical element and a correction value selected by the selection unit. Comprising acquisition means for acquiring gradation data and selection data for each electro-optic element;
In the unit circuit corresponding to each electro-optic element,
The selection unit selects a correction value specified by selection data acquired by the acquisition unit for the electro-optic element from among a plurality of correction values held by the holding unit,
The electro-optical device according to claim 1, wherein the driving unit generates a driving signal based on the gradation data acquired by the acquisition unit for the electro-optical element and the correction value selected by the selection unit. Comprising acquisition means for acquiring image data of a plurality of bits for each of a plurality of electro-optic elements;
In the unit circuit corresponding to each electro-optic element,
The selection means is a correction value corresponding to a numerical value group to which a numerical value of image data acquired by the acquisition means for the electro-optic element belongs among a plurality of numerical value groups obtained by dividing a plurality of numerical values expressed by the plurality of bits. For the electro-optic element,
The electro-optical device according to claim 1, wherein the driving unit generates a driving signal based on image data acquired by the acquiring unit for the electro-optical element and a correction value selected by the selecting unit. An electro-optic element whose gradation is controlled according to a drive signal;
Holding means for holding a plurality of correction values for the electro-optic element;
Selecting means for selecting any of a plurality of correction values held by the holding means;
An electro-optical device, comprising: a drive unit that generates the drive signal based on a gradation value designated for the electro-optical element and a correction value selected by the selection unit. Comprising an acquisition means for acquiring image data of a plurality of bits;
The selection means selects a correction value corresponding to a numerical value group to which the numerical value of the image data acquired by the acquisition means belongs among a plurality of numerical value groups obtained by dividing a plurality of numerical values represented by the plurality of bits,
The electro-optical device according to claim 4, wherein the driving unit generates the driving signal based on image data acquired by the acquiring unit and a correction value selected by the selecting unit. The total number m of numerical values represented by the plurality of bits, the number s of gradation values other than zero, and the number j of correction values held for the electro-optic element are:
m <j × s + 1
And the plurality of numerical groups includes a first numerical group and a second numerical group, each including a separate numerical value,
The said 2nd numerical value group consists of a numerical value which designates each one of some gradation values of the high gradation side among the several gradation values designated by each numerical value of the said 1st numerical value group. Electro-optic device. 7. The drive unit according to claim 1, wherein the drive unit generates a drive signal having a current value corresponding to the correction value over a pulse width corresponding to a gradation value designated for the electro-optical element. Electro-optic device.   An electronic apparatus comprising the electro-optical device according to claim 1. A circuit for outputting a drive signal for controlling the gradation of the electro-optic element,
Holding means for holding a plurality of correction values for the electro-optic element;
Selecting means for selecting any of a plurality of correction values held by the holding means;
A drive circuit for an electro-optical device, comprising: a drive unit that generates the drive signal based on a gradation value designated for the electro-optical element and a correction value selected by the selection unit.

Images