JP2008055817A - Electro-optic device, driving circuit, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the influence of defective elements not be conspicuous by brief method. <P>SOLUTION: An electro-optic device H comprises: two or more electro-optic elements E whose light amounts are adjustable; and a driving circuit 20 which controls light amounts of each electro-optic elements E. In the two or more electro-optic elements E, when the same tone value is designated to elements EA for compensation of a set number in the position close to a defective element EA and to a standard element E0 in the position estranged from the defective element EA as compared with each of elements EA for compensation, the driving circuit 20 actuates each of electro-optic elements E so that each of elements EA for compensation has a larger light amount than the standard element E0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for controlling 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, a specific electro-optical element (hereinafter referred to as “defective element”) is caused by a defect in each element such as the electro-optical element itself or an active element or wiring used for driving the electro-optical element. ) May be less than the specified value or may not emit light at all. Patent Document 1 discloses a technique for forming a single latent image on the surface of a photoconductor by performing multiple exposures while shifting the position of an image. According to this technique, since the influence of the defective element is dispersed by the image shift, it is possible to make the influence of the insufficient light quantity in the defective element inconspicuous in the actually output visible image.
Japanese Patent Laid-Open No. 9-61939

  However, the configuration of Patent Document 1 has a problem that complicated control such as multiple exposures and image shifts is required for one image. In addition, there is a problem that power consumption increases as compared to a case where a latent image is formed by one exposure for one image. In view of the above circumstances, an object of the present invention is to solve the problem of making the influence of defective elements inconspicuous by a simple method.

  In order to solve the above problems, an electro-optical device according to one aspect of the present invention includes a plurality of electro-optical elements having variable light amounts, and a drive circuit that controls the light amounts of the plurality of electro-optical elements. The drive circuit includes a predetermined number (one or a plurality) of first electro-optic elements located in the vicinity of the electro-optic element related to the defect (for example, the defect element ED in FIGS. 5 and 7) among the plurality of electro-optic elements. The optical element (for example, the compensating element EA in FIGS. 5 and 7) and a position farther from the electro-optical element related to the defect than the predetermined number of first electro-optical elements (that is, the distance from the electro-optical element related to the defect) Is the same level as the second electro-optic element (for example, the standard element E0 in FIGS. 5 and 7) located at a position larger than the distance between the predetermined number of first electro-optic elements and the electro-optic element related to the defect. A predetermined number of first electric lights when a tone value is specified Element so that the larger amount of light than the second electro-optical element, to drive the electro-optical elements.

  In the above configuration, the first electro-optic element located near the electro-optic element related to the defect is driven with a larger light amount than the second electro-optic element. Therefore, it is possible to make the defect of the electro-optical element inconspicuous while reducing power consumption without requiring complicated control such as multiple exposures and pixel shifts. The electro-optical element is an element that emits a light amount corresponding to the electric energy applied from the drive circuit. An electro-optical element related to a defect is a light amount when a specific gradation value is designated due to a defect of the electro-optical element itself or a defect of an element (for example, an active element or a wiring) used for driving the electro-optical element. Means an electro-optic element that is less than a predetermined value or does not emit light at all.

  In addition, the first electro-optical element is “close to” the electro-optical element related to the defect typically means that the first electro-optical element and the electro-optical element related to the defect are adjacent to each other (that is, the gap between the two). However, even if another electro-optical element is interposed in the gap between the first electro-optical element and the electro-optical element related to the defect, for example, the electro-optical device When the user visually recognizes an image to be output, if the influence of the shortage of the light amount of the electro-optical element related to the defect is reduced to a level not perceived by the user by the increase of the light amount of the first electro-optical element, It can be said that the first electro-optical element and the electro-optical element related to the defect are “close to each other”.

  An electro-optical device according to a preferred aspect of the present invention includes a storage circuit that stores a correction value of each electro-optical element, and the drive circuit includes a plurality of unit circuits corresponding to each electro-optical element, and includes a plurality of units. Each of the circuits is generated by a generation unit (for example, the transistor Q2 in FIG. 3) that generates a drive signal of a level (voltage value or current value) corresponding to the correction value of the electro-optic element corresponding to the unit circuit. Drive control means (for example, transistor Q3 in FIG. 3) for supplying the drive signal to each electro-optical element over a time length corresponding to the gradation value of the electro-optical element, and each correction value stored in the storage circuit is The drive signal supplied to the predetermined number of first electro-optical elements is set to be higher than the drive signal supplied to the second electro-optical elements. The drive signal in the above embodiment may be either a current signal (for example, the drive current IDR in FIG. 2) or a voltage signal. The drive signal level is a current value if the drive signal is a current signal, and a voltage value if the drive signal is a voltage signal. In addition, individual storage circuits may be installed for each unit circuit, or one storage circuit shared by a plurality of unit circuits may be installed.

  In a more specific aspect, the drive circuit corrects the light amount of the second electro-optical element so that the light amounts of the plurality of second electro-optical elements are uniformized when the same gradation value is designated for each. According to the above aspect, in addition to the influence of the defect of the electro-optical element, it is possible to suppress unevenness in the amount of light of each electro-optical element.

The positional relationship between the first electro-optical element and the electro-optical element related to the defect is arbitrary. For example, from the viewpoint of effectively compensating for the shortage of the light amount in the electro-optical element related to the defect without significantly affecting the content of the image, the predetermined number of first electro-optical elements includes the electro-optical element related to the defect. Including an electro-optic element adjacent to the electrode (regardless of whether or not the first electro-optic element is located on both sides of the electro-optic element related to the defect) and each electro-optic element located on both sides of the electro-optic element related to the defect (A matter of whether or not the first electro-optical element is adjacent to the electro-optical element related to the defect) is preferably employed. Further, for example, in a configuration in which a plurality of electro-optic elements are arranged in a plurality of rows (for example, two rows and staggered), the electro-optic devices are located on both sides of the electro-optic device in one row where the defect-related electro-optic devices are present. The element is a first electro-optical element.
In a more specific aspect, the predetermined number of first electro-optical elements includes a plurality of electro-optical elements adjacent to one side of the electro-optical element related to the defect and a plurality of electro-optical elements adjacent to the other side. . For example, the drive circuit according to this aspect is configured such that, among the predetermined number of first electro-optical elements, the first electro-optical element located near the electro-optical element related to the defect has a relatively large light amount. Drive the element. According to the above aspect, since the light quantity of each electro-optical element is controlled stepwise according to the distance from the defect, it is possible to make the defect of the electro-optical element less noticeable.
In a configuration in which the predetermined number of first electro-optical elements includes a plurality of electro-optical elements adjacent to the electro-optical element related to the defect, the electro-optical related to the defect among the predetermined number of first electro-optical elements. The electro-optical elements may be driven so that the first electro-optical element located closer to the element has a larger light quantity.

  It is not always necessary to constantly increase the light amount of the first electro-optic element. For example, when the same gradation value is specified for the first electro-optic element and the second electro-optic element, the drive circuit according to a preferred aspect of the present invention assigns a predetermined value to the electro-optic element related to the defect. When a gradation value greater than the specified value is specified, the predetermined number of first electro-optical elements has a larger light quantity than the second electro-optical element, and a gradation value lower than the predetermined value is specified for the electro-optical element related to the defect. In this case, each electro-optical element is driven so that a predetermined number of first electro-optical elements have the same amount of light as the second electro-optical element. According to the above aspect, it is possible to suppress the deterioration of the first electro-optical element as compared with the configuration in which the light amount of the first electro-optical element is constantly increased.

  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 includes an image carrier (for example, a photosensitive drum) 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, a latent image on the image carrier). And a developing device for forming a visible image by adding a toner. 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. In an electro-optical device in which a plurality of electro-optical elements are arranged in a planar shape across a first direction and a second direction intersecting with each other, the electro-optical element close to the defective electro-optical element along at least one of the first direction and the second direction The drive circuit drives each electro-optical element so that the light quantity of the first electro-optical element to be increased. For example, the amount of light of four first electro-optical elements adjacent to both sides in each of the first direction and the second direction increases with respect to one electro-optical element related to the defect.

  The present invention is also specified as a circuit for driving the electro-optical device according to each of the above aspects. A drive circuit according to one aspect of the present invention is a circuit that controls the amount of light of each of a plurality of electro-optical elements, and is a predetermined one located in the vicinity of the electro-optical element related to the defect among the plurality of electro-optical elements. When the same gradation value is designated for the number of first electro-optic elements and the second electro-optic elements located at a position away from the electro-optic elements related to the defects compared to the first electro-optic elements, Each electro-optic element is driven so that a predetermined number of first electro-optic elements have a larger light quantity than the second electro-optic elements. The drive circuit described above also provides the same operations and effects as the electro-optical device according to the present invention.

  The present invention is also specified as a method of driving the electro-optical device according to each of the above aspects. A driving method according to an aspect of the present invention is a method for controlling the amount of light of each of a plurality of electro-optical elements, and is a predetermined position at a position close to the electro-optical element related to the defect among the plurality of electro-optical elements. When the same gradation value is designated for the number of first electro-optic elements and the second electro-optic elements located at a position away from the electro-optic elements related to the defects compared to the first electro-optic elements, Each electro-optic element is driven so that a predetermined number of first electro-optic elements have a larger light quantity than the second electro-optic elements. Also by the above driving method, the same operation and effect as the electro-optical device according to the 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 a device used in an electrophotographic image forming apparatus as a line head (exposure device) for exposing a photosensitive drum, and includes an element unit 10 and a drive circuit 20 as shown in FIG. To do.

  The element unit 10 includes n electro-optical elements E arranged in a straight line along the X direction (main scanning direction) (n is a natural number of 2 or more). The electro-optic element E 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 facing each other. A desired latent image is formed on the surface of the photosensitive drum by irradiation with the light emitted from each electro-optical element E. A configuration in which a plurality of electro-optical elements E are arranged in a plurality of rows (for example, two rows and a staggered shape) is also employed.

  The drive circuit 20 controls the light amount of each electro-optical element E. The drive circuit 20 may be composed of one or a plurality of IC chips, and a large 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-optic elements E. Thin film transistor). As shown in FIG. 1, the drive circuit 20 includes n unit circuits U each corresponding to a separate electro-optic element E. The unit circuit U in the i-th stage (i is an integer satisfying 1 ≦ i ≦ n) outputs the drive signal S [i].

  FIG. 2 is a timing chart showing waveforms of the drive signals S [i] (S [1] to S [n]). As shown in FIG. 2, the drive signal S [i] is transmitted in a period TG corresponding to the gradation value designated for the i-th electro-optical element E in a predetermined period (eg, horizontal scanning period) T. This is a current signal that becomes the drive current IDR and whose current value becomes zero in the remaining period T. The electro-optical element E emits light when the drive current IDR is supplied, and turns off when the supply of the drive current IDR is stopped.

  FIG. 3 is a circuit diagram showing a configuration of each unit circuit U. In the figure, only one unit circuit U at the i-th stage is representatively shown. As shown in FIG. 3, the unit circuit U includes a correction circuit 22 and p-channel transistors Q1 to Q3. The correction circuit 22 is means for generating a control current ICT that is the basis of the drive current IDR.

  FIG. 4 is a circuit diagram showing a specific configuration of the correction circuit 22. As shown in the figure, the correction circuit 22 includes a reference current source 221, a storage circuit 223, and a D / A converter 225. The reference current source 221 is an n-channel transistor that generates a reference current IREF corresponding to the reference potential VREF1 applied to its gate.

  The storage circuit 223 stores the correction value A (four bits a1 to a4) set for each unit circuit U. The correction value A stored in the storage circuit 223 of the i-th stage unit circuit U corrects the degree of correction of the drive current IDR in the drive signal S [i] (that is, corrects the light quantity of the i-th stage electro-optical element E). It is a numerical value that specifies the degree to The storage circuit 223 of the present embodiment is a memory (for example, ROM (Read Only Memory)) that stores the correction value A stored at the time of manufacturing the electro-optical device H in a nonvolatile manner. However, a memory that stores the correction value A supplied from the outside each time the electro-optical device H is turned on may be adopted as the storage circuit 223. A method for setting the correction value A of each unit circuit U will be described later.

  The D / A converter 225 is means for generating a correction current Ix corresponding to the correction value A stored in the storage circuit 223, and includes four n-channel transistors TA (corresponding to the number of bits of the correction value A). TA1 to TA4) and four n-channel transistors TB (TB1 to TB4) each having a drain connected to the source of the transistor TA. The drain of each transistor TA is connected to the node N together with the drain of the reference current source 221, and the source of each transistor TB is grounded together with the source of the reference current source 221.

  The transistors TB1 to TB4 function as a current source that generates a current corresponding to the reference potential VREF2 applied to each gate. The electrical characteristics (for example, gain coefficient) of the transistors TB1 to TB4 are such that the relative ratio of the current values of the currents c1 to c4 flowing through the supply of the reference potential VREF2 to the gate is a power of 2 (c1: c2: c3: c4 = 1: 2: 4: 8).

  As shown in FIG. 4, each of the transistors TA1 to TA4 is selectively turned on according to each bit (a1 to a4) of the correction value A stored in the storage circuit 223. Therefore, a correction current Ix having a current value corresponding to the correction value A flows through a path connecting the node N and the D / A converter 225. With the above configuration, the control current ICT obtained by adding the reference current IREF and the correction current Ix flows to the node N.

  As shown in FIG. 3, the source of each of the transistors Q1 and Q2 is connected to a high-side power supply (VEL). The drain of the transistor Q1 is connected to the node N of the correction circuit 22 and its own gate. Transistors Q1 and Q2 form a current mirror circuit by connecting their gates to each other. Accordingly, when the control current ICT generated by the correction circuit 22 flows between the source and drain of the transistor Q1, a current value corresponding to the control current ICT (for example, the same current value as the control current ICT) is generated between the source and drain of the transistor Q2. ) Is generated. Since the current value of the control current ICT (correction current Ix) is controlled according to the correction value A, the correction circuit 22 and the transistor Q1 in FIG. 2 function as means for correcting the drive current IDR according to the correction value A. .

  The transistor Q3 is a switching element disposed on the path of the drive current IDR generated by the transistor Q2, and is selectively turned on in a period TG corresponding to the gradation value designated for the electro-optical element E. . When the transistor Q3 becomes conductive, the drive current IDR generated by the transistor Q2 is supplied to the electro-optical element E. When the transistor Q3 is turned off, the supply of the drive current IDR to the electro-optic element E is stopped. That is, the drive signal S [i] has a current value (IDR) corresponding to the correction value A over the pulse width (TG) corresponding to the gradation value of the i-th unit circuit U. Accordingly, each electro-optical element E emits light with a light amount corresponding to the gradation value and the correction value A.

  Next, FIG. 5 is a conceptual diagram illustrating each light quantity when the same gradation value is designated for each electro-optical element E. Each square shown in the figure represents one electro-optic element E, and the area of each square means the amount of light of the electro-optic element E. That is, the larger the square, the greater the amount of light of the electro-optic element E.

  Now, as illustrated in part (a) of FIG. 5, when it is assumed that no defect exists in any of the electro-optic elements E, the electro-optic elements E designated with the same gradation value are equivalent to each other. Assume that light is emitted with a light quantity of. On the other hand, part (b) of FIG. 5 illustrates the light amount of each electro-optical element E when the i-th electro-optical element E is a defective element ED in a configuration in which the light amount of each electro-optical element E is not corrected. ing. The defective element ED means that the amount of light is less than a prescribed value due to its own defects or defects of each part of the unit circuit U (for example, the transistors Q1 to Q3 and the wiring connecting them) (typically the part of FIG. 5). This is an electro-optical element E that does not emit light at all as in (b). When the photosensitive drum is exposed using each electro-optical element E in the state of part (b) in FIG. 5, the position corresponding to the defective element ED in the image actually formed by the image forming apparatus is not located at the sub-position. Streaky unevenness occurs in the scanning direction (the direction in which the photosensitive surface of the photosensitive drum advances).

  Part (c) of FIG. 5 is a conceptual diagram showing the light amount of each electro-optical element E after correction according to the present embodiment. As shown in the figure, in the present embodiment, another electro-optical element E adjacent to the defective element ED (hereinafter, sometimes referred to as “compensation element EA” in relation to the defective element ED). The correction value A of each unit circuit U is set so that the amount of light increases compared to the non-correction illustrated in the part (b) of FIG. As described above, by increasing the light amount of the compensating element EA, the shortage of light amount due to the defective element ED is compensated, so the streaky unevenness caused by the defective element ED is compared with the case of the part (b) in FIG. Reduced.

  In this embodiment, two (i-1) th and (i + 1) th electro-optic elements adjacent to both sides along the X direction with respect to the i-th defective element ED E is a compensation element EA. As shown in part (d) of FIG. 5, the correction value A of the compensation element EA is an electro-optic element E (hereinafter referred to as the compensation element EA and the defective element ED out of the n electro-optic elements E). Then, the numerical value A1 is set to be larger than the correction value A (A0) of “standard element E0” (A1> A0). By selecting the correction value A as described above, the drive current IDR supplied to the compensation element EA is set to a higher current value than the drive current IDR supplied to the standard element E0. Therefore, when the same gradation value is designated for the compensation element EA and the standard element E0, the compensation element EA emits light with a light quantity larger than that of the standard element E0 as shown in part (c) of FIG.

  From the viewpoint of reliably compensating for the shortage of the light amount in the defective element ED, for example, the sum of the increase in the light amount of each compensation element EA compared to the non-correction is the gradation specified for the defective element ED. It is desirable to determine the correction value A of each compensation element EA so as to substantially match the amount of light according to the value (that is, the amount of light when the defective element ED is assumed to be normal). That is, the total light amount after correction of the two compensation elements EA is from the (i-1) th stage to the (i + 1) th stage when the i-th electrooptic element E has no defect. The total amount of light of the three electro-optical elements E is substantially the same.

  As described above, in the present embodiment, the filling element EA adjacent to the defective element ED is driven to have a larger light quantity than the standard element E0 at a position farther from the defective element ED than the filling element EA. . Accordingly, the complicated control of Patent Document 1 such as multiple exposures and pixel shifts is unnecessary, and an increase in power consumption is suppressed, while unevenness in the amount of light in the element unit 10 (and streaks in an image formed by the image forming apparatus). Unevenness). In addition, even when a defective element ED is present in the element portion 10, the electro-optical device H can be effectively used by compensating for the amount of light, so that the substantial yield of the electro-optical device H can be improved.

  Next, a procedure for setting the correction value A of each electro-optical element E will be described with reference to FIG. Each process in FIG. 6 is automatically executed by an inspection apparatus (for example, an information processing apparatus) within a period from manufacture to shipment of the electro-optical device H, for example.

  As shown in the figure, first, the inspection apparatus searches for a defective element ED for the element unit 10 of the electro-optical device H (step S10). For example, the inspection apparatus controls the drive circuit 20 so that the drive current IDR is sequentially supplied to each of the n electro-optical elements E, and the light amount of each electro-optical element E at that time is received by a light receiving device (for example, An electro-optic element E having a light amount below a predetermined value is determined as a defective element ED after being sequentially measured by a signal from an imaging device using a CCD element. In step S10, the position of the defective element ED in the element unit 10 is also specified.

  Next, the inspection apparatus determines whether or not a defective element ED has been found in step S10 (step S11). When the defective element ED is not found, the inspection apparatus sets the correction value A of each of the n electro-optical elements E to a numerical value A0 (for example, zero) (step S12). On the other hand, when the defective element ED is found, the inspection apparatus sets the correction value A of each compensation element EA adjacent to the defective element ED to a numerical value A1 (A1> A0) and compensates for the defective element ED. The correction value A of the standard element E0 excluding the use element EA is set to a numerical value A0 (step S13). Then, the inspection apparatus writes the correction value A set in step S12 or step S13 in each storage circuit 223 of the electro-optical device H (step S14). The above is the procedure for setting the correction value A.

<B: Second Embodiment>
Next, a second embodiment of the present invention will be described. In the first embodiment, it is assumed that the characteristics (relationship between gradation value and light amount) of each electro-optical element E other than the defective element ED are equal. It can be different. Therefore, in the embodiment exemplified below, in addition to the shortage of the light amount due to the defective element ED, the light amount unevenness due to the difference in the characteristics of the electro-optical elements E is also reduced. In addition, about the element which an effect | action and function are common among 1st Embodiment among this embodiment, the same code | symbol as the above is attached | subjected, and each detailed description is abbreviate | omitted suitably.

  FIG. 7 is a conceptual diagram illustrating the amount of light when the same gradation value is designated for each electro-optical element E. FIG. In FIG. 5, each square represents one electro-optical element E as in FIG. 5, and the area of each square means the amount of light of the electro-optical element E.

  In the part (a) and the part (b) in FIG. 7, it is assumed that the light amount of each electro-optical element E is not corrected. The part (a) of FIG. 7 shows the light quantity of each electro-optical element E when the defective element ED does not exist in the element part 10, and the part (b) of FIG. 7 shows the i-th stage electro-optical element E. The amount of light of each electro-optical element E in the case of the defective element ED is shown. As shown in part (a) and part (b) of FIG. 7, variations in the characteristics of the electro-optical elements E and the elements of the unit circuits U (for example, the transistors Q1 to Q3) regardless of the presence or absence of the defective element ED. Due to the variation in characteristics, the amount of light of each electro-optic element E is different. In the present embodiment, not only the amount of light of the compensation element EA is increased, but also the amount of light of the respective compensation elements EA and the amount of light of the standard elements E0 are made uniform. The correction value A is determined individually according to each characteristic.

  Part (c) of FIG. 7 is a conceptual diagram showing the light amount of each electro-optical element E after correction according to the correction value A. As shown in the drawing, in the present embodiment, the standard light quantity of each standard element E0 when the same gradation value is designated for each approaches a predetermined value (ideally equalized). The correction value A of the element E0 is set according to each characteristic. For example, the correction value A of the electro-optic element E is set to a relatively large numerical value when the amount of light at the time of non-correction is small (however, the threshold value determined as the defective element ED is exceeded). Further, the correction value A of the two compensation elements EA located on both sides in the X direction with respect to the defective element ED is the light quantity of each compensation element EA when the same gradation value as that of the standard element E0 is designated. Then, it is set so as to approach a predetermined value larger than the light amount of the corrected standard element E0.

  The correction value A that satisfies the above conditions is set, for example, when the inspection apparatus executes each process illustrated in FIG. First, the inspection apparatus measures the amount of light for each of the n electro-optic elements E constituting the element unit 10 (step S20). For example, the inspection apparatus controls the drive circuit 20 so that the drive current IDR is sequentially supplied to each electro-optical element E, and the light amount of each electro-optical element E at that time is sequentially determined by a signal from the light receiving device. To measure. Next, the inspection apparatus sets the correction value A of each electro-optic element E so that the quantity of light is uniform for the n electro-optic elements E based on each quantity of light measured in step S20 (step S21). . The process of step S21 is for the electro-optical element E in which the light quantity measured in step S20 exceeds a predetermined value (that is, the compensation element EA and the standard element E0 excluding the defective element ED from the n electro-optical elements E). Run as.

  Next, the inspection apparatus searches for a defective element ED from the element unit 10 (step S22). In step S22, the electro-optical element E in which the light quantity measured in step S20 is less than a predetermined value may be determined as a defective element ED, and the same processing as in step S10 in FIG. 6 is performed separately from step S20. The defective element ED may be searched by executing. In step S22, the position of the defective element ED is also specified. Then, the inspection apparatus determines whether or not a defective element ED has been found in step S22 (step S23).

  When the defective element ED is found, the inspection apparatus corrects the correction value A set in step S21 for each compensation element EA adjacent to the defective element ED (step S24). For example, the inspection apparatus calculates the addition value of the correction value A set in step S21 and the predetermined value for the compensation element EA as a new correction value A. That is, the variation in the light quantity between the respective compensation elements EA is suppressed by setting the correction value A in step S21, and each compensation is performed so that the shortage in the light quantity of the defective element ED is compensated by correcting the correction value A in step S24. The amount of light of the element EA increases. The correction value A of the standard element E0 is maintained at the numerical value set in step S21 (that is, a numerical value that equalizes the amount of light between the standard elements E0).

  On the other hand, if no defective element ED is found in step S22, the inspection apparatus shifts the process to step S25 without executing step S24. Accordingly, the correction value A of all the electro-optical elements E is maintained at the numerical value set in step S21 (that is, a numerical value that can equalize the amount of light of all the electro-optical elements E). Then, the inspection apparatus writes the correction value A set in the above procedure (S21 / S24) in each storage circuit 223 of the electro-optical device H (step S25).

  As described above, in the present embodiment, since the compensation element EA adjacent to the defective element ED is driven with a light quantity larger than that of the standard element E0, the same effect as that of the first embodiment is achieved. Furthermore, according to this embodiment, since the correction value A of each electro-optical element E is set according to each characteristic, an error in the amount of light of the electro-optical elements E other than the defective element ED is suppressed. It is possible to more effectively suppress the unevenness of the amount of light at 10 (and the unevenness of the gradation of the image formed by the image forming apparatus) more effectively than the first embodiment.

  In addition, in the present embodiment, the compensation of the shortage of the light amount due to the defective element ED and the compensation of the variation in the light amount of each electro-optical element E are realized by setting the correction value A. Therefore, elements for realizing each are provided. There is no need to prepare them individually. For example, a circuit having the configuration illustrated in FIG. 3 or a circuit that corrects only the variation in the amount of light of the electro-optic element E according to the correction value A can be used as each unit circuit U of the present embodiment. That is, according to the present embodiment, it is possible to obtain an expected effect of suppressing unevenness in the amount of light without complicating the configuration of the electro-optical device H and enlarging the circuit.

<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 case where each electro-optic element E adjacent to both sides of the defective element ED is used as the compensation element EA is exemplified. However, the positional relationship between the defective element ED and the compensation element EA is appropriately determined. Changed to For example, only one electro-optic element E adjacent to the defective element ED on one side in the X direction may be used as the compensation element EA.

  Further, three or more electro-optic elements E belonging to a predetermined range including the defective element ED may be used as the compensation element EA. For example, FIG. 9 shows each electro-optical element E after correction when two electro-optical elements E (total of four) located on both sides in the X direction with respect to the defective element ED are used as the compensation elements EA. Is shown.

  In the configuration in which two or more electro-optic elements E adjacent to each side along the X direction with respect to the defective element ED are the compensating elements EA, as shown in FIG. 9, the position is close to the defective element ED. The correction value A of each electro-optical element E may be set so that the amount of light increases stepwise as the compensation element EA is. That is, in the example of FIG. 9, each of the (i-2) -th and (i + 2) -th compensating elements EA emits light with a light quantity larger than that of the standard element E0, and further to the defective element ED. The (i-1) -th and (i + 1) -th compensating elements EA at the close positions are the (i-2) -th and (i + 2) -th compensating elements. The correction value A is determined so as to emit light with a light quantity larger than EA. According to the configuration of FIG. 9, as in the first embodiment and the second embodiment, only two electro-optical elements E adjacent to the defective element ED are used as the compensation elements EA, or close to the defective element ED. Compared with the configuration in which the three or more compensating elements EA emit light with the same amount of light, it is possible to make the shortage of the light amount due to the defective element ED more inconspicuous.

(2) Modification 2
In each of the above embodiments, the configuration in which the pulse width of the drive signal S [i] is controlled according to the gradation value and the current value of the drive current IDR is controlled according to the correction value A is exemplified. The relationship between the tone value and the correction value A and the waveform of the drive signal S [i] is appropriately changed. For example, a configuration in which the pulse width of the drive signal S [i] is controlled according to the correction value A and the current value of the drive current IDR is controlled according to the gradation value, and both the correction value A and the gradation value are determined. A configuration is also employed in which one of the pulse width of the drive signal S [i] and the current value of the drive current IDR is controlled. In addition, for example, in the electro-optical device H that uses the voltage-driven electro-optical element E in which the amount of light changes due to the application of voltage, the drive signal S [i] is a voltage signal. The value may be corrected according to the correction value A. As can be understood from the above examples, the driving circuit 20 according to one aspect of the present invention is configured such that the compensation element EA is the standard element E0 when the same gradation is designated for the compensation element EA and the standard element E0. Any circuit that drives each electro-optical element E so as to obtain a larger light quantity is sufficient.

(3) Modification 3
It is not always necessary to constantly increase the light amount of the compensation element EA. For example, a configuration in which the light amount of the compensation element EA is increased only when the gradation value specified for the defective element ED satisfies a predetermined condition. For example, when a gradation value corresponding to non-light emission (extinguishment) is designated for the defective element ED, the shortage of light quantity caused by the defective element ED does not inherently cause a problem. Therefore, when the gradation value designated for the defective element ED falls below a predetermined value, the increase in the light amount of the compensation element EA may be stopped.

  In other words, when the same gradation value is designated for each of the compensation element EA and the standard element E0, the driving circuit 20 determines that a gradation value exceeding a predetermined value is designated as the defective element ED. Each compensation element EA has a larger light quantity than the standard element E0, and when a gradation value lower than a predetermined value is designated as the defective element ED, each compensation element EA has a light quantity equivalent to that of the standard element E0. Each electro-optical element E is driven. More specifically, when non-light emission is instructed to the defective element ED, the drive current IDR supplied to the compensation element EA is set to a current value equivalent to the drive current IDR supplied to the standard element E0. The For example, the correction value A of the compensation element EA is changed to a numerical value A0 equivalent to the standard element E0. According to the above configuration, it is possible to suppress deterioration of the compensation element EA as compared with a configuration in which the light amount of the compensation element EA is constantly increased.

(4) Modification 4
The organic light emitting diode element is merely an example of an electro-optical element. 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 H according to the present invention will be described.
FIG. 10 is a cross-sectional view illustrating a configuration of an image forming apparatus employing the electro-optical device H according to the above embodiment. 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. 10, 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.

  In addition, in the display device, since the user is less likely to perceive the amount of light due to the defective element ED, the electro-optical device H is determined to be a non-defective product if, for example, one defective element ED exists in the element unit 10. There is also a possibility that. However, in the image forming apparatus using the electro-optical device H as an exposure device as shown in FIG. 10, the influence of the defective element ED is manifested as streaky unevenness in the image. For example, the electro-optical device H as a whole may be determined to be defective even if only one defective element ED exists in the element unit 10. That is, the conditions of the electro-optical element E required for determining the electro-optical device H as a non-defective product are particularly strict in the image forming apparatus. Considering the above circumstances, it can be said that the electro-optical device H of each of the above forms in which the influence of the defective element ED is reduced is particularly suitable as an exposure device of the image forming apparatus.

1 is a block diagram illustrating a configuration of an electro-optical device H according to a first embodiment. It is a timing chart which illustrates the waveform of drive signal S [i]. It is a circuit diagram which shows the structure of a unit circuit. It is a circuit diagram which shows the structure of a correction circuit. It is a conceptual diagram for demonstrating correction | amendment of the light quantity of each electro-optical element. It is a flowchart which shows the procedure which sets a correction value. It is a conceptual diagram for demonstrating correction | amendment of the light quantity of each electro-optical element in 2nd Embodiment. It is a flowchart which shows the procedure which sets a correction value. It is a conceptual diagram for demonstrating correction | amendment of the light quantity of each electro-optical element in a modification. It is sectional drawing which shows one form (image forming apparatus) of an electronic device.

Explanation of symbols

H: Electro-optical device, 10: Element portion, E: Electro-optical element (EA: Compensation element, E0: Standard element, ED: Defect element), 20: Drive circuit, U: Unit Circuit, 22 ... correction circuit, Q1-Q3 ... transistor.

Claims (10)

A plurality of electro-optic elements with variable light amounts;
A drive circuit for controlling the amount of light of each of the plurality of electro-optic elements,
The drive circuit includes a predetermined number of first electro-optical elements located near the electro-optical element related to the defect among the plurality of electro-optical elements and the predetermined number of first electro-optical elements compared to the predetermined number. When the same gradation value is specified for the second electro-optical element located at a position away from the electro-optical element related to the defect, the predetermined number of first electro-optical elements is more than the second electro-optical element. An electro-optical device that drives each of the electro-optical elements so that the amount of light is large. A storage circuit for storing a correction value of each electro-optical element;
The drive circuit includes a plurality of unit circuits corresponding to the electro-optic elements,
Each of the plurality of unit circuits is
Generating means for generating a drive signal at a level corresponding to the correction value of the electro-optic element corresponding to the unit circuit;
Drive control means for supplying the drive signal generated by the generation means to each of the electro-optic elements in at least a part of the time length according to the gradation value of the electro-optic elements,
Each correction value stored in the storage circuit is set such that the drive signal supplied to the predetermined number of first electro-optical elements is higher than the drive signal supplied to the second electro-optical elements. The electro-optical device according to claim 1. The light quantity of the said 2nd electro-optical element is corrected so that the said drive circuit may equalize the light quantity of several 2nd electro-optical element when the same gradation value is designated for each. Electro-optic device. The electro-optical device according to any one of claims 1 to 3, wherein the predetermined number of first electro-optical elements includes an electro-optical element adjacent to the electro-optical element related to the defect. The electro-optical device according to any one of claims 1 to 3, wherein the predetermined number of first electro-optical elements include electro-optical elements located on both sides of the electro-optical element related to the defect. The predetermined number of first electro-optical elements include a plurality of electro-optical elements adjacent to one side of the electro-optical element related to the defect and a plurality of electro-optical elements adjacent to the other side. Item 4. The electro-optical device according to any one of items 3. The drive circuit drives the electro-optical elements so that the first electro-optical element located near the electro-optical element related to the defect has a larger light amount among the predetermined number of first electro-optical elements. The electro-optical device according to claim 6. The predetermined number of first electro-optical elements includes a plurality of electro-optical elements adjacent to the electro-optical element related to the defect,
The electro-optical elements are driven such that, of the predetermined number of first electro-optical elements, the first electro-optical element located closer to the electro-optical element related to the defect has a larger light amount. Item 4. The electro-optical device according to any one of items 3.   An electronic apparatus comprising the electro-optical device according to claim 1. A drive circuit that controls the amount of light of each of the plurality of electro-optic elements,
Among the plurality of electro-optical elements, a predetermined number of first electro-optical elements at positions close to the electro-optical element related to the defect and the electro-optics related to the defect compared to the predetermined number of first electro-optical elements When the same gradation value is specified for the second electro-optic element located at a position away from the element, the predetermined number of first electro-optic elements has a larger light quantity than the second electro-optic element. And a driving circuit of an electro-optical device for driving each of the electro-optical elements.

Images