JP2010023390A - Light emitting apparatus and electronic instrument - Google Patents

Abstract

The luminance of a light emitting element can be corrected with high accuracy while preventing the use efficiency of light emitted from the light emitting element from decreasing.
Light emitting elements E1 to En and light receiving elements PD1 to PDn are formed on the surface of the substrate. The light emitting elements E1 to En and the light receiving elements PD1 to PDn do not overlap each other when viewed from the direction perpendicular to the substrate. When acquiring the correction value of each light emitting element E, predetermined electrical energy (current or voltage) is supplied to cause the light emitting elements E1 to En to emit light one by one in order. For example, the light receiving elements PD1, PD2, and PD3 are used when measuring the emitted light from the light emitting element E2, and the light receiving elements PD2, PD3, and PD4 are used when measuring the emitted light from the light emitting element E3. For each light emitting element E, the measured value is compared with a reference value, and a correction value for each light emitting element E is obtained. The correction value of each light emitting element E is stored in the memory, and this is used to correct the electric energy supplied to each of the light emitting elements E1 to En.
[Selection] Figure 7

Description

  The present invention relates to a light emitting device using a light emitting element such as an organic EL (Electroluminescence) element and an electronic apparatus using the same.

Since the characteristics of the organic EL element change due to temperature change or deterioration with time, it is necessary to adjust the luminance by correcting the drive current. For example, in the optical head for an image forming apparatus described in Patent Document 1, a photodetecting element 120 that receives light from the electroluminescent element 110 is formed immediately below the electroluminescent element 110, and the electroluminescent element is formed. The magnitude of the drive current supplied to the cent element 110 is corrected according to the amount of light received by the light detection element 120. Moreover, in the organic light emitting display device 20 described in Patent Document 2, a plurality of photodiodes 230 connected in parallel are provided in the periphery of the pixel region A, and an electrical signal output from the photodiode 230 (parallel connection). Is used to adjust the luminance of the organic electroluminescent element (pixel).
JP 2007-290329 A JP 2007-173832 A

By the way, in the configuration in which the light detection element 120 is formed immediately below the electroluminescent element 110 as in Patent Document 1, when the light emitted from the electroluminescent element 110 passes through the light detection element 120, reflection or Decrease by absorption. That is, since the amount of light finally emitted to the outside decreases, the utilization efficiency of the emitted light from the electroluminescent element 110 is reduced. Further, when the drive current supplied to the electroluminescent element 110 is increased in order to compensate for such a decrease in the amount of light, the electroluminescent element 110 is deteriorated earlier and its life is shortened accordingly.
Further, in the configuration in which the photodiode 230 (parallel connection) is provided in the peripheral portion of the pixel region A as in Patent Document 2, the distance to the photodiode 230 is different for each organic electroluminescent element (pixel). The emitted light from the light emitting element cannot be measured accurately. Therefore, the brightness of each organic electroluminescent element cannot be accurately adjusted.

  The present invention has been made in view of the above-described problems, and a light-emitting device capable of correcting the luminance of a light-emitting element with high accuracy while preventing the use efficiency of light emitted from the light-emitting element from being lowered, and the same It is an object to provide a used electronic device.

In order to solve the above-described problems, a light-emitting device according to the present invention includes a plurality of light-emitting elements formed on a surface of a substrate and each emitting light with a luminance corresponding to supplied electric energy, and the surface of the substrate. A plurality of light receiving elements formed in regions excluding each region where each of the plurality of light emitting elements is formed, each outputting a detection signal at a level corresponding to the amount of incident light; and the plurality of light emitting elements. Selection means for sequentially selecting one by one; supply means for supplying predetermined electrical energy to the selected light emitting element each time the selecting means selects the light emitting element; and Each time it is selected, two or more light receiving elements corresponding to the selected light emitting element are selected from the plurality of light receiving elements, and based on detection signals of the selected two or more light receiving elements, The selection hand Measuring means for measuring the amount of light emitted from the light emitting element selected by the light emitting element, and for each of the light emitting elements, the measured light amount by the measuring means is compared with a predetermined reference value, and the light emission from the comparison result Determining means for determining a correction value of electric energy supplied to the element; storage means for storing a correction value for each of the light emitting elements determined by the determining means; and electric energy supplied to each of the plurality of light emitting elements. And correction means for correcting using the correction value for each light emitting element stored in the storage means.
The measuring means may be configured to change two or more light receiving elements used for measurement of emitted light for each light emitting element.

  According to the above configuration, since the plurality of light receiving elements are formed on the surface of the substrate so as not to overlap the plurality of light emitting elements, light from the light emitting elements can be emitted to the outside without passing through the light receiving elements. . Therefore, the use efficiency of the emitted light from each light emitting element can be increased as compared with the configuration of Patent Document 1. Moreover, since the emitted light (light quantity) of one light emitting element is measured using two or more light receiving elements, the emitted light of each light emitting element can be accurately measured as the light receiving area can be increased. Therefore, the brightness of each light emitting element can be corrected with high accuracy.

  Further, in order to correct the luminance of each light emitting element with high accuracy, it is necessary to measure the emitted light of each light emitting element as accurately as possible. For this reason, in the above-described light emitting device, the measurement unit is configured such that the relative positions of the light emitting element that is the measurement target of the emitted light and the two or more light receiving elements that are used for the measurement of the emitted light are the same. In addition, a configuration in which two or more of the light receiving elements used for measurement of emitted light are selected, a configuration in which each of the plurality of light receiving elements has the same input / output characteristics, or an arrangement pitch of the plurality of light emitting elements, It is desirable that the arrangement pitch of the plurality of light receiving elements is equal.

  Further, in the above-described electro-optical device, each of the plurality of light receiving elements outputs a detection current having a level corresponding to the amount of incident light as the detection signal, and the measurement unit includes two or more selected The current value obtained by adding the detected currents output from each of the light receiving elements may be the measurement value. In the electro-optical device described above, the light receiving elements may be arranged on both sides of the light emitting element on both sides of the light emitting element on the surface of the substrate.

  Each of the two light receiving elements disposed on both sides of the light emitting element includes a first region formed by one of a P-type semiconductor and an N-type semiconductor, and the P-type semiconductor and the N-type semiconductor. A second region formed on the other side, and in each of the two light receiving elements, the first region may be positioned closer to the light emitting element than the second region. In this configuration, when viewed from the direction perpendicular to the surface of the substrate, the arrangement of the first region and the second region of the two light receiving elements arranged on both sides of the light emitting element can be aligned with the light emitting element. Therefore, it is possible to eliminate the deviation of the detection signal due to the difference in sheet resistance between the first region and the second region, and to measure the emitted light of each light emitting element more accurately.

In addition, the light emitting device according to the present invention is used in various electronic devices. A typical example of the electronic apparatus according to the present invention is an electrophotographic image forming apparatus in which any of the light-emitting devices described above is used for exposure of an image carrier such as a photosensitive drum. The image forming apparatus includes an image carrier (for example, a photosensitive drum) on which a latent image is formed by exposure, a light emitting device of the present invention that exposes the image carrier, and a developer (for example, toner) for the latent image on the image carrier. And a developing device for forming a visible image by adding.
However, the use of the light emitting 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 light emitting device according to the present invention can be used for illuminating a document. An image reading apparatus includes any one of the light emitting devices described above and a light receiving device that converts light emitted from the light emitting device and reflected by a reading target (original) into an electrical signal (for example, a light receiving element such as a CCD: Charge Coupled Device). Is provided. Furthermore, a light-emitting device in which light-emitting elements are arranged in a matrix or zigzag pattern is also used as a display device for various electronic devices such as personal computers and mobile phones.

<A: First Embodiment>
FIG. 1 is a perspective view showing a partial structure of an electrophotographic image forming apparatus using the light emitting device according to the first embodiment of the present invention as an exposure device (optical head). As shown in the figure, the image forming apparatus includes a light emitting device 100, a photosensitive drum 70, and a converging lens array 80. The light emitting device 100 includes a long substrate 10 on which a large number of light emitting elements E and light receiving elements PD are formed along the X direction (main scanning direction). The photosensitive drum 70 is a cylindrical body supported by a rotation axis in the X direction, and rotates with the outer peripheral surface facing the substrate 10. The converging lens array 80 disposed between the light emitting device 100 and the photosensitive drum 70 images the light emitted from each light emitting element E on the outer peripheral surface of the photosensitive drum 70. By the above exposure, a latent image (electrostatic latent image) corresponding to a desired image is formed on the outer peripheral surface of the photosensitive drum 70.

  In addition to the normal mode in which a latent image corresponding to image data supplied from the outside is formed on the outer peripheral surface of the photosensitive drum 70 as an operation mode, the light emitting device 100 sets a luminance correction value for each light emitting element E. It has a correction value acquisition mode to acquire. For example, when the power of the image forming apparatus is turned on, when the preset date / time is reached, or when the operation time of the image forming apparatus exceeds a predetermined time, the operation mode acquires the correction value. Switch to mode.

  FIG. 2 is a block diagram illustrating an electrical configuration of the light emitting device 100. As shown in the figure, the light emitting device 100 includes a pixel driving circuit 11, a pixel unit 12, a photosensor unit 13, an A / D conversion circuit 14, and a control circuit 15. The control circuit 15 outputs image data Dout that specifies the gradation of each pixel of the image to be formed by the image forming apparatus to the pixel driving circuit 11 in the normal mode, and in the correction value acquisition mode, Reference data Dstd designating a predetermined reference current is output.

  The pixel drive circuit 11 generates the drive current Id to be supplied to each light emitting element E based on the image data Dout in the normal mode, and based on the reference data Dstd in the correction value acquisition mode. As a result, in the normal mode, the magnitude of the drive current Id supplied to each light emitting element E differs depending on the image data Dout, but in the correction value acquisition mode, it is the same for all the light emitting elements E. A drive current Id (reference current) having a magnitude is supplied.

Each light emitting element E provided in the pixel unit 12 emits light with a luminance corresponding to the drive current Id supplied from the pixel drive circuit 11. Each light emitting element E is an organic EL element in which a light emitting layer of an organic EL material is interposed between an anode and a cathode facing each other. Each light receiving element PD provided in the optical sensor unit 13 outputs a detection current _IPD having a magnitude corresponding to the amount of incident light. The A / D conversion circuit 14 converts the detection current _IPD output from the optical sensor unit 13 from an analog signal to a digital signal, and outputs it to the control circuit 15 as a measured value Iout.

  In the correction value acquisition mode, the control circuit 15 obtains a correction value for each light emitting element E using the measurement value Iout output from the A / D conversion circuit 14. The correction value of each light emitting element E is stored in a memory (not shown) provided in the control circuit 15. In the normal mode, the control circuit 15 corrects the image data Din supplied from the outside using the correction value of each light emitting element E stored in the memory, and this is used as the image data Dout for the pixel driving circuit 11. Output to. The correction value of each light emitting element E is set so that the luminance of each light emitting element E is made uniform when, for example, image data Din specifying the same gradation is supplied to all pixels. .

  FIG. 3 is a diagram illustrating a circuit configuration of the pixel driving circuit 11. As shown in the figure, the pixel drive circuit 11 includes a selection transistor T1 and a drive transistor T2 for each light emitting element E. The selection transistor T1 is an N-channel thin film transistor, and a selection signal SEL is supplied to the gate. When the select signal SEL becomes Hi level, the select transistor T1 is turned on, and the reference data Dstd or image data Dout for one pixel is supplied to the gate of the drive transistor T2. The drive transistor T2 is a P-channel thin film transistor, and controls the amount of drive current Id in accordance with the gate potential. The light emitting element E emits light with a light amount (luminance) corresponding to the amount of the drive current Id during the period in which the selection transistor T1 is on.

  FIG. 4 is a plan view showing the arrangement of the light emitting element E, the light receiving element PD, and the driving transistor T2. FIG. 5 is a cross-sectional view taken along line IV-IV in FIG. As shown in FIG. 4, when viewed from the direction perpendicular to the substrate 10, the light emitting element E, the light receiving element PD, and the driving transistor T2 are arranged in the Y direction, and the light receiving element PD is disposed between the light emitting element E and the driving transistor T2. Be placed. The drive transistor T2 includes a semiconductor layer 32 and a gate electrode 34. As shown in FIG. 4, the semiconductor layer 32 is covered with a light-transmitting insulating layer L0. The gate electrode 34 is formed on the surface of the insulating layer L 0 and faces the channel region of the semiconductor layer 32.

  The light receiving element PD includes a light receiving layer 40. The semiconductor layer 32 and the light receiving layer 40 are collectively formed in a common process (hereinafter simply referred to as “formed from the same layer”) by selectively removing a single film body. For example, the semiconductor layer 32 and the light receiving layer 40 are polysilicon film bodies obtained by crystallizing amorphous silicon by laser irradiation (laser annealing). The light receiving layer 40 is covered with the insulating layer L <b> 0 together with the semiconductor layer 32.

As shown in FIGS. 4 and 5, the light receiving layer 40 includes a first region 41, a second region 42, and an intrinsic region 44. The first region 41 and the second region 42 are regions formed of different conductivity type semiconductors. That is, the first region 41 is formed by one of a P-type semiconductor and an N-type semiconductor, and the second region 42 is formed by the other of the P-type semiconductor and the N-type semiconductor. The intrinsic region 44 is an intrinsic semiconductor region located between the first region 41 and the second region 42. The light receiving layer 40 having the above configuration functions as a PIN (P-Intrinsic-N) type diode that generates a current (detection current I _PD ) having a magnitude corresponding to the amount of light irradiated to the intrinsic region 44.

  As shown in FIG. 5, a light-transmitting insulating layer L1 is formed over the entire surface of the insulating layer L0 on which the gate electrode 34 is formed. As shown in FIG. 4, the source electrode 36 and the drain electrode 38 of the driving transistor T2 are formed of a light-reflective conductive material (for example, aluminum or silver) on the surface of the insulating layer L1. The source electrode 36 is electrically connected to the source region of the semiconductor layer 32 through a conduction hole H1a that penetrates the insulating layer L1 and the insulating layer L0. Similarly, the drain electrode 38 is electrically connected to the drain region of the semiconductor layer 32 through a conduction hole H1b penetrating the insulating layer L1 and the insulating layer L0.

As shown in FIG. 4, on the surface of the insulating layer L1, the first detection electrode 51 and the second detection electrode 52 are formed from the same layer as the source electrode 36 and the drain electrode 38 of the drive transistor T2. The first detection electrode 51 and the second detection electrode 52 are light reflective electrode for outputting the detected current I _PD from the light-receiving element PD (wiring). The first detection electrode 51 includes a portion p1 that overlaps the first region 41 of the light receiving layer 40. The portion p1 is electrically connected to the first region 41 of the light receiving layer 40 through a conduction hole H2a that penetrates the insulating layer L1 and the insulating layer L0. The second detection electrode 52 includes a portion p <b> 2 that overlaps the entire second region 42 of the light receiving layer 40. The portion p2 is electrically connected to the second region 42 of the light receiving layer 40 through a plurality of conduction holes H2b penetrating the insulating layer L1 and the insulating layer L0. In the above configuration, the current flowing through the first detection electrode 51 and the second detection electrode 52 via the light receiving layer 40 is output as the detection current _IPD .

  As shown in FIG. 5, a light-transmissive insulating layer L2 is formed on the entire surface of the insulating layer L1. The insulating layer L2 is, for example, a laminate (not shown) of an inorganic layer such as silicon oxide or silicon nitride and a planarization layer that reduces a step on the surface of the insulating layer L2 reflecting the driving transistor T2 or the light receiving element PD. Consists of.

  On the surface of the insulating layer L2, a first electrode 62 (the outer shape is shown by a broken line in FIG. 4 for convenience) that functions as an anode of the light emitting element E is formed. For the formation of the first electrode 62, a light transmissive conductive material such as ITO (Indium Tin Oxide) is used. As seen from the direction perpendicular to the substrate 10 as shown in FIG. 4, the first electrode 62 continues from the gap between the light receiving element PD and the driving transistor T2 to a region opposite to the driving transistor T2 as viewed from the light receiving element PD. Formed as follows. Therefore, the light receiving element PD and the first electrode 62 overlap. As shown in FIGS. 4 and 5, the first electrode 62 is electrically connected to the drain electrode 38 of the drive transistor T2 through the conduction hole H3 penetrating the insulating layer L2. The conduction hole H3 is located in the gap between the driving transistor T2 (semiconductor layer 32) and the light receiving element PD (light receiving layer 40) when viewed from the direction perpendicular to the substrate 10.

  As shown in FIG. 5, an element defining layer (bank layer) 64 is formed on the surface of the insulating layer L2 on which the first electrode 62 is formed. The element defining layer 64 is an insulating film body in which an opening 642 is formed in a shape (substantially circular) corresponding to the outer shape of the light emitting element E, as shown in FIGS. The first electrode 62 includes a portion located inside the opening 642 (that is, a portion exposed from the element defining layer 64 through the opening 642). The opening 642 is formed at a position and shape that does not overlap the light receiving layer 40 of the light receiving element PD.

  As shown in FIG. 5, the light emitting layer 66 is formed so as to cover the element defining layer 64 and the first electrode 62. The light emitting layer 66 is formed over the entire area of the substrate 10 so as to be continuous over the plurality of light emitting elements E. A film forming technique such as a spin coating method is preferably used for forming the light emitting layer 66. Further, as shown in FIG. 5, the second electrode 68 is formed on the surface of the light emitting layer 66. The second electrode 68 is formed continuously over the plurality of light emitting elements E and functions as the cathode of each light emitting element E. For the formation of the second electrode 68, a light-reflective conductive material (for example, aluminum or silver) is used.

  As shown in FIGS. 4 and 5, the portion inside the opening 642 of the element defining layer 64 in the stack of the first electrode 62, the light emitting layer 66, and the second electrode 68 functions as the light emitting element E. Since the opening 642 is formed in a region of the element defining layer 64 that does not overlap the light receiving layer 40, the light receiving element PD (light receiving layer 40) and the light emitting element are viewed from a direction perpendicular to the substrate 10 as shown in FIG. E do not overlap. That is, the light receiving element PD is formed in a region that does not overlap the light emitting element E on the surface of the substrate 10.

A part of the light emitted from the light emitting element E (light emitting layer 66) reaches the first electrode 62 after being reflected by the second electrode 68 or directly from the light emitting layer 66, and the first electrode 62 and the insulating layer (L2). , L 1, L 0) and the substrate 10, and are emitted to the outside (photosensitive drum 70 side). Further, another part of the light emitted from the light emitting element E travels to the light receiving element PD side after being reflected by the second electrode 68 or directly from the light emitting layer 66, as shown by arrows in FIG. The light is incident on the light receiving layer 40 and used to generate the detection current _IPD .

FIG. 6 is a plan view showing the arrangement of the light emitting elements E1 to En and the light receiving elements PD1 to PDn. As shown in the figure, on the surface of the substrate 10 (on the surface opposite to the photosensitive drum 70), n light emitting elements E1 to En are arranged at equal intervals in the X direction, and one light emitting element array is arranged. I am doing. Similarly, n light receiving elements PD1 to PDn are also arranged at equal intervals in the X direction to form one light receiving element array. Thus, when viewed from the direction perpendicular to the substrate 10, the light emitting elements E1 to En and the light receiving elements PD1 to PDn do not overlap. The arrangement pitch of the light emitting elements E1 to En and the arrangement pitch of the light receiving elements PD1 to PDn are equal. In addition, the input-output characteristic of the light receiving element PD1~PDn are the same, if the amount of light incident on the light receiving element PD is the same, the same magnitude of the detected current I _PD outputted from the light receiving element PD Become.

  By the way, in the correction value acquisition mode, the light emitting device 100 according to the present embodiment causes the light emitting elements E1 to En to emit light one by one at a brightness corresponding to the reference current (reference data Dstd). At this time, as shown in FIG. 7, for example, when the light emitting element E2 is emitting light, the light emitting device 100 uses three light receiving elements PD1, PD2, and PD3 to emit light from the light emitting element E2. When the light emitting element E3 is emitting light, the light quantity of the emitted light from the light emitting element E3 is measured using the three light receiving elements PD2, PD3, and PD4. Note that two light receiving elements PD1 and PD2 are used when measuring the amount of light emitted from the light emitting element E1, and two light receiving elements PDn-1 are used when measuring the amount of light emitted from the light emitting element En. , PDn is used. As described above, the light emitting device 100 measures the emitted light (light quantity) from each light emitting element E using two or three light receiving elements PD. Further, the two or three light receiving elements PD used when measuring the emitted light are different for each light emitting element E.

FIG. 8 is a circuit diagram showing a connection configuration of the light receiving elements PD1 to PDn and the A / D conversion circuit 14. As shown in the figure, the light receiving elements PD1 to PDn are connected to the A / D conversion circuit 14 via the switches SW1 to SWn. Each light receiving element PDi (i = 1 to n) outputs a detection current _IPDi having a magnitude corresponding to the amount of incident light. The switches SW1 to SWn are turned on and off by the control circuit 15. The A / D conversion circuit 14, only the detection current I _PDi from the light receiving elements PDi connected to the switch SWi which is on is input summed. For example, when only the switches SW2, SW3, and SW4 are turned on in FIG. 8, the detection current _IPD2 output from the light receiving element PD2, the detection current IPD3 output from the light receiving element _PD3, and the light receiving element PD4 The output detection current _IPD4 is added and input to the A / D conversion circuit 14.

  FIG. 9 is a timing chart showing the operation of the light emitting device 100 in the correction value acquisition mode. In the figure, the periods T1, T2, T3,... Tn-1, Tn all have the same time width. In the correction value acquisition mode, the control circuit 15 switches the signal levels of the select signals SEL1 to SELn as shown in FIG. That is, only the select signal SEL1 is set to Hi level in the period T1, only the select signal SEL2 is set to Hi level in the period T2, and only the select signal SEL3 is set to Hi level in the period T3. As described above, the control circuit 15 sets only the select signal SELi to the Hi level in the period Ti.

  As described with reference to FIG. 3, when the select signal SELi becomes Hi level, the select transistor T1 is turned on and the light emitting element Ei emits light. Accordingly, the light-emitting element E1 emits light during the period T1, the light-emitting element E2 emits light during the period T2, and the light-emitting element E3 emits light during the period T3. That is, in the correction value acquisition mode, the light emitting elements E1 to En emit light one by one in the order of E1, E2, E3,. Further, in the correction value acquisition mode, since the same drive current Id (reference current) is supplied to all the light emitting elements E1 to En, each light emitting element E emits light with a luminance corresponding to the reference current. It will be.

  In parallel with the light emission control described above, the control circuit 15 controls the on / off of the switches SW1 to SWn as shown in FIG. That is, only the two switches SW1 and SW2 are turned on in the period T1. Further, only the three switches SW1, SW2, and SW3 are turned on in the period T2, and only the three switches SW2, SW3, and SW4 are turned on in the period T3. In this way, during the period T2 to the period Tn-1, if the target period is Tj (j = 2 to n-1), only the three switches SWj-1, SWj, SWj + 1 are turned on. In the period Tn, only the two switches SWn−1 and SWn are turned on.

As described with reference to FIG. 8, only the detected current _{I PDi} from the light receiving elements PDi connected to the switch SWi which is on (i = 1 to n) is summed to the A / D conversion circuit 14 It is inputted and outputted to the control circuit 15 as a final measurement value Iout. Therefore, in the period T1, the light emitted from the light emitting element E1 is measured using the two light receiving elements PD1 and PD2. In the period T2, the light emitted from the light emitting element E2 is measured using the three light receiving elements PD1, PD2, and PD3. In the period T3, the light emitted from the light emitting element E3 is measured using the three light receiving elements PD2, PD3, and PD4. Will be measured. Thus, during the period T2 to the period Tn-1, when the target period is Tj (j = 2 to n-1), light emission is performed using the three light receiving elements PDj-1, PDj, and PDj + 1. The emitted light from the element Ej will be measured. In the period Tn, the light emitted from the light emitting element En is measured using the two light receiving elements PDn-1 and PDn.

  The control circuit 15 is supplied with a measured value Iout measured for each period Ti (i = 1 to n). For example, when the measurement value Iout measured in the period T1 is supplied, the control circuit 15 obtains the correction value of the light emitting element E1 using the measurement value Iout. Further, when the measurement value Iout measured in the period T2 is supplied, the control circuit 15 obtains the correction value of the light emitting element E2 using the measurement value Iout. A reference value Istd is stored in a memory (not shown) provided in the control circuit 15. The reference value Istd is a measurement value Iout obtained when measurement is performed on the light emitting element E that has not deteriorated with time. The control circuit 15 calculates a difference between the measured value Iout and the reference value Istd, and obtains a correction value for the light emitting element E based on the calculated difference value.

  When calculating the correction value from the difference value, for example, a calculation formula for calculating the correction value from the difference value may be prepared, and the difference value may be substituted into this calculation formula. Moreover, the structure which refers to the correction value table which divided the numerical range which can take the value of a difference into several, and defined the correction value for each division may be sufficient. Further, the correction value may be obtained from the ratio between the measurement value Iout and the reference value Istd instead of the difference between the measurement value Iout and the reference value Istd.

  When the control circuit 15 obtains the correction value for each light emitting element E in this way, the correction value for each light emitting element E is stored in a memory (not shown) provided in the control circuit 15. Thereafter, the control circuit 15 switches the operation mode from the correction value acquisition mode to the normal mode. In the normal mode, image data Din is supplied to the control circuit 15 from the outside. In the normal mode, the control circuit 15 reads the correction value of each light emitting element E stored in the memory, corrects the image data Din, and outputs this to the pixel drive circuit 11 as the image data Dout. That is, the control circuit 15 corrects the amount of drive current Id supplied to each light emitting element E by correcting the image data Din using the correction value of each light emitting element E. Thereby, the brightness | luminance of each light emitting element E is adjusted.

  Of the light emitting elements E1 to En, the light emitting element E1 and the light emitting element En measure the emitted light using the two light receiving elements PD, and thus the three light receiving elements PD are used to measure the emitted light. The measured value Iout differs from the case of the light emitting elements E2 to En-1 that perform the measurement even when the light is emitted with the same luminance. For this reason, it is necessary to prepare two types of reference values Istd used for comparison with the measured value Iout. That is, the reference value Istd for the light emitting elements E1 and En and the reference value Istd for the light emitting elements E2 to En-1.

  However, for example, as shown in FIG. 10, a light receiving element PD0 and a light receiving element PDn + 1 are further provided on the surface of the substrate 10, and for the light emitting element E1, the emitted light is measured using the light receiving elements PD0, PD1, and PD2, If the light emitting element En is configured to measure the emitted light using the light receiving elements PDn-1, PDn, PDn + 1, the light emitting element E1 and the light emitting element En also use the three light receiving elements PD to transmit the emitted light. Since measurement can be performed, it is not necessary to store two types of reference values Istd in the memory. In such a configuration, when measuring the emitted light of each light emitting element E, the relative positions of one light emitting element E to be measured and the three light receiving elements PD used in the measurement. Can always be made the same, so that the emitted light of each light emitting element E can be accurately measured.

  As described above, in the light emitting device 100 according to the present embodiment, the light receiving elements PD1 to PDn are formed on the surface of the substrate 10 so as not to overlap the light emitting elements E1 to En. Therefore, the light from the light emitting elements E1 to En is emitted to the outside (photosensitive drum 70 side) without passing through the light receiving elements PD1 to PDn. Therefore, the use efficiency of the emitted light from each light emitting element E can be increased as compared with the configuration of Patent Document 1. Further, by increasing the utilization efficiency of the emitted light, it is possible to reduce the drive current Id necessary for causing the light emitting element E to emit light with the desired luminance, and accordingly, the deterioration of the light emitting element E over time can be suppressed. Long life can be achieved.

  Further, in the light emitting device 100 according to the present embodiment, the light emitted from one light emitting element E is measured using two or three light receiving elements PD. The emitted light can be measured accurately. Therefore, the luminance of each light emitting element E can be corrected with high accuracy. In addition, the light receiving area of each light receiving element PD is not increased, but the light emitted from one light emitting element E is measured using a plurality of light receiving elements PD. Can be placed on the surface. That is, when the required correction accuracy is the same, the area of the substrate 10 is reduced compared with the case where the light receiving area of each light receiving element PD is increased and the light emitted from one light emitting element E is measured by one light receiving element PD. Therefore, the light emitting device 100 can be downsized.

  For example, as shown in FIG. 11, when the light emitting elements E1 to En and the light receiving elements PD1 to PDn + 1 are arranged on the substrate 10 and the light emitting element E1 is emitting light, two light receiving elements PD1 and PD2 are used. When the light emitted from the light emitting element E1 is measured and the light emitting element E2 is emitting light, the light emitted from the light emitting element E2 may be measured using the two light receiving elements PD2 and PD3. That is, when the light emitting element Ei (i = 1 to n) is emitting light, the light emitted from the light emitting element Ei may be measured using the two light receiving elements PDi and PDi + 1.

  As shown in FIG. 12, when a plurality of light emitting elements E and a plurality of light receiving elements PD are arranged in a staggered manner and the light emitting element E1 is emitting light, two light receiving elements PD1 and PD3 are used. When the light emitted from E1 is measured and the light emitting element E2 is emitting light, the light emitted from the light emitting element E2 may be measured using the two light receiving elements PD2 and PD4. That is, when the light emitting element Ei (i = 1 to n) is emitting light, the light emitted from the light emitting element Ei may be measured using the two light receiving elements PDi and PDi + 2. However, in this case, if n light emitting elements E and light receiving elements PD are provided, the emitted light can be measured by the above-described method from the light emitting element E1 to the light emitting element En-2. With respect to En-1 and the light emitting element En, since the light receiving elements PDn + 1 and PDn + 2 do not exist, the emitted light is measured by one light receiving element PD. In order to avoid this, for example, light receiving elements PDn + 1 and PDn + 2 may be further provided on the substrate 10. When measuring the light emitted from the light emitting element En-1, two light receiving elements PDn-3 and PDn-1 are used. When measuring the light emitted from the light emitting element En, two light receiving elements PDn are used. It is good also as a structure which uses -2 and PDn.

  Further, in the case where a plurality of light emitting elements E are arranged in a staggered manner, the light receiving element PD is arranged as shown in FIG. 13, and the case where the light emitted from the light emitting element E1 is measured and the case where the light emitted from the light emitting element E2 is measured. Alternatively, the light receiving elements PD1 and PD2 may be used, and the light receiving elements PD2 and PD3 may be used when measuring the light emitted from the light emitting element E3 and when measuring the light emitted from the light emitting element E4.

<B: Second Embodiment>
Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the element which is common in 1st Embodiment, and description is abbreviate | omitted suitably.
As shown in FIG. 14, on the surface of the substrate 10 of the light emitting device 100 according to the second embodiment, light receiving element arrays are arranged on both sides of a single light emitting element array. The light emitting element array is composed of n light emitting elements E1 to En arranged at equal intervals in the X direction. In addition, the light receiving element array includes a first light receiving element array including n light receiving elements PD _{11 to} PD _1n arranged at equal intervals in the X direction, and n light receiving elements arranged at equal intervals in the X direction. a second light-receiving element array consisting of PD ₂₁ ~PD _2n.

As in the first embodiment, when viewed in a direction perpendicular to the substrate 10, the light emitting element E1~En and the light-receiving element _{PD 11 ~PD 1n, PD 21 ~PD} 2n do not overlap. Further, the arrangement pitch of the light-emitting elements E1 to En, and the array pitch of the light receiving element _PD 11 _{-PD 1n,} the array pitch of the light-receiving element _PD 21 _{-PD 2n} are equal. Further, the distance from the light emitting element array to the first light receiving element array (Y direction) is equal to the distance from the light emitting element array to the second light receiving element array (Y direction). Further, the input / output characteristics of the light receiving elements PD _{11 to} PD _1n and PD _{21 to} PD _2n are the same, and if the amount of light incident on each light receiving element PD is the same, detection output from each light receiving element PD The magnitude of the current _IPD is also the same.

Further, as shown in FIG. 14, each of the light receiving elements PD _{11 to} PD _1n and PD _{21 to} PD _2n includes a light receiving layer 40 that functions as a PIN diode. The light receiving layer 40 is located between the first region 41 made of a P-type semiconductor, the second region 42 made of an N-type semiconductor, and the first region 41 and the second region 42, and is made of an intrinsic semiconductor. And an intrinsic region 44 formed. In addition, the light receiving elements PD _1i and PD _2i located on both sides of the light emitting element Ei have the three areas 41, 42, and 44 when viewed from the central light emitting element Ei, the first area 41 (P type), The intrinsic region 44 and the second region 42 (N-type) are arranged in this order. That is, when viewed from the direction perpendicular to the substrate 10, in each light receiving element PD, the first region 41 (P type) is located closer to the light emitting element E than the second region 42 (N type).

In each light receiving element PD, the sheet resistance of the first region 41 (P type) is different from the sheet resistance of the second region 42 (N type). Therefore, as described above, by arranging the three regions 41, 42, and 44 in the light receiving elements PD _1i and PD _2i to be aligned with the light emitting element Ei, the light receiving elements PD _1i and PD _2i due to the different sheet resistances. eliminating the deviation of the detected current I _PD of, it is possible to more accurately measure the output light of each light-emitting element E.

  Note that the conductivity types of the first region 41 and the second region 42 may be reversed. That is, each light receiving element PD (light receiving layer 40) includes a first region 41 formed of an N-type semiconductor, a second region 42 formed of a P-type semiconductor, a first region 41, and a second region 42. A configuration having an intrinsic region 44 formed between intrinsic semiconductors may be used.

Also in the light emitting device 100 according to the second embodiment, in the correction value acquisition mode, the light emitting elements E1 to En are caused to emit light one by one at a luminance corresponding to the reference current (reference data Dstd). At this time, for example, as shown in FIG. 15, the light emitting device 100 uses the six light receiving elements PD _{11 to} PD ₁₃ and PD _{21 to} PD ₂₃ when the light emitting element E2 is emitting light. amount was measured in the emitted light, the light-emitting element E3 is the case in the light emission, using six light receiving element _{PD 12 ~PD 14, PD 22 ~PD} 24 measures the amount of light emitted from the light emitting element E3. Note that four light receiving elements PD ₁₁ , PD ₁₂ , PD ₂₁ , and PD ₂₂ are used when measuring the amount of light emitted from the light emitting element E1, and 4 when measuring the amount of light emitted from the light emitting element En. Two light receiving elements PD _1n−1 , PD _1n , PD _2n−1 , PD _2n are used. As described above, the light emitting device 100 according to the present embodiment measures the emitted light (light quantity) of each light emitting element E using four or six light receiving elements PD. Further, the four or six light receiving elements PD used when measuring the emitted light are different for each light emitting element E.

According to the second embodiment described above, in addition to the same effects as those of the first embodiment, the light receiving element arrays are arranged on both sides of the light emitting element array, so that light reception is achieved as compared with the configuration of the first embodiment. The area can be doubled. Therefore, compared with the structure of 1st Embodiment, the emitted light of each light emitting element E can be measured more correctly, As a result, it becomes possible to correct | amend the brightness | luminance of each light emitting element E with a higher precision. In addition, by aligning the arrangement of the three regions 41, 42, and 44 in the light receiving elements PD _1i and PD _{2i with} respect to the light emitting element Ei, it becomes possible to measure the emitted light of each light emitting element E more accurately.

For example, as shown in FIG. 16, when a plurality of light emitting elements E and a plurality of light receiving elements PD are arranged in a staggered manner and the light emitting element E2 is emitting light, three light receiving elements PD ₂₁ , PD ₁₁ , PD ₂₂ , the light emitted from the light emitting element E2 is measured. When the light emitting element E3 is emitting light, the light emitted from the light emitting element E3 is measured using the three light receiving elements PD ₁₁ , PD ₂₂ , PD _12. It is good also as a structure.

<C: Application example>
Next, a specific example of an electronic apparatus (image forming apparatus) using the light emitting device 100 described above will be described.
FIG. 17 is a cross-sectional view illustrating a configuration of the image forming apparatus. The image forming apparatus shown in the figure is a tandem type full-color image forming apparatus, and includes four light emitting devices 100 (100K, 100C, 100M, and 100Y) and four photosensitive drums 70 corresponding to the respective light emitting devices 100. (70K, 70C, 70M, 70Y). As shown in FIG. 1, one light emitting device 100 is disposed so as to face the exposed surface 70 </ b> A (outer peripheral surface) of the corresponding photosensitive drum 70. Note that the subscripts “K”, “C”, “M”, and “Y” of each symbol are used to form each visible image of black (K), cyan (C), magenta (M), and yellow (Y). Means.

  As shown in FIG. 17, 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.

  Around each photosensitive drum 70, a corona charger 731 (731K, 731C, 731M, 731Y) and a developing device 732 (732K, 732C, 732M, 732Y) are arranged in addition to the light emitting device 100. The corona charger 731 uniformly charges the exposed surface 70A of the corresponding photosensitive drum 70. Each of the light emitting devices 100 exposes this charged exposed surface 70A, thereby forming an electrostatic latent image. Each developing unit 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 transfers the visible image to the intermediate transfer belt 72 that passes through the gap between the photosensitive drum 70 and the primary transfer corotron 74 by electrostatically attracting the visible image from the corresponding photosensitive drum 70. To do.

  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 described above uses an organic EL element as a light source (exposure means), the apparatus can be made smaller than a configuration using a laser scanning optical system. Note that a rotary developing type image forming apparatus, an image forming apparatus that directly transfers a visible image from the photosensitive drum 70 to a sheet without using an intermediate transfer belt, or an image that forms a monochrome image. The light emitting device 100 can also be used for a forming apparatus or the like.

  The use of the light emitting device 100 is not limited to the exposure of the image carrier (photosensitive drum 70). For example, the light emitting device 100 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). A light emitting device in which the light emitting elements E are arranged in a matrix or zigzag can also be 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, calculator, word processor, workstation, video phone, POS terminal, printer, scanner, copier, video player, and the like.

<D: Modification>
The light emitting element E may be an inorganic EL element or an LED (Light Emitting Diode) element. The light receiving element PD may be a PN type diode, photodiode, or phototransistor. The electrical energy supplied to the light emitting element E may be a voltage instead of a current. The light receiving element PD may output a voltage having a magnitude corresponding to the amount of incident light as a detection signal. A configuration in which a detection signal (current or voltage) from each light receiving element PD is individually A / D converted, and then only a detection value from two or more light receiving elements PD used for light quantity measurement is added and calculated to obtain a measured value It may be. The memory that stores the correction value of each light emitting element E may be provided in the image forming apparatus instead of the light emitting apparatus 100.

1 is a perspective view showing a partial structure of an image forming apparatus. It is a block diagram which shows the electrical structure of the light-emitting device which concerns on 1st Embodiment. It is a circuit diagram (part) of a pixel drive circuit. It is a top view which shows arrangement | positioning of a light emitting element, a light receiving element, and a drive transistor. It is sectional drawing of the IV-IV line in FIG. It is a top view which shows arrangement | positioning of n light emitting elements and n light receiving elements. It is a figure which shows three light receiving elements used when measuring the emitted light of the light emitting element E3, and three light receiving elements used when measuring the emitted light of the light emitting element E2. It is a circuit diagram which shows the connection structure of n light receiving elements and an A / D conversion circuit. It is a timing chart which shows operation | movement of the light-emitting device in correction value acquisition mode. It is a top view (modification) which shows arrangement | positioning of a light emitting element and a light receiving element. It is a top view (modification) which shows arrangement | positioning of a light emitting element and a light receiving element. It is a top view (modification) which shows arrangement | positioning of a light emitting element and a light receiving element. It is a top view (modification) which shows arrangement | positioning of a light emitting element and a light receiving element. It is a figure which shows arrangement | positioning of the light emitting element and light receiving element which concern on 2nd Embodiment. It is a figure which shows six light receiving elements used when measuring the emitted light of the light emitting element E2, and six light receiving elements used when measuring the emitted light of the light emitting element E2. It is a top view (modification) which shows arrangement | positioning of a light emitting element and a light receiving element. It is sectional drawing which shows the specific example (image forming apparatus) of an electronic device.

Explanation of symbols

100 ... light-emitting device, 70 ... photoconductor drum, 80 ... converging lens array, E, E1 to En ... light emitting _{element, PD, PD1~PDn, PD 11 ~PD} 1n, PD 21 ~PD 2n ... light receiving element, 11 ... Pixel drive circuit, 12... Pixel section, 13... Optical sensor section, 14... A / D conversion circuit, 15... Control circuit, Din... Image data (before correction), Dout ... image data (after correction), Dstd. , Id ... drive _{current, I PD, I PD1 ~I PDn} ... detection current, Iout ... measured value, T1 ... select transistor, T2 ... driving transistor, SEL, SEL1～SELn ... select signal, SWl to SWn ... switch, 40 ... Light-receiving layer, 41 ... first region, 42 ... second region, 44 ... intrinsic region, 62 ... first electrode 62 (anode), 64 ... element defining layer, 642 ... opening, 66 ... light-emitting layer, 68 ... second The pole (cathode).

Claims (9)

A plurality of light emitting elements that are formed on the surface of the substrate and each emit light with a luminance corresponding to the supplied electric energy;
A plurality of light-receiving elements that are formed in areas other than the areas where each of the plurality of light-emitting elements is formed on the surface of the substrate, and that output detection signals at levels according to the amount of incident light; ,
Selecting means for sequentially selecting the plurality of light emitting elements one by one;
Supply means for supplying predetermined electrical energy to the selected light emitting element each time the selection means selects the light emitting element;
Each time the selection means selects the light emitting element, two or more light receiving elements corresponding to the selected light emitting element are selected from the plurality of light receiving elements, and the selected two or more light receiving elements are selected. Measuring means for measuring the amount of light emitted from the light emitting element selected by the selection means based on the detection signal of the element;
A determining unit that determines a correction value of the electric energy supplied to the light emitting element from the comparison result by comparing a measured value of the light amount by the measuring unit with a predetermined reference value for each light emitting element;
Storage means for storing a correction value for each light emitting element determined by the determination means;
Correction means for correcting electric energy supplied to each of the plurality of light emitting elements using a correction value for each of the light emitting elements stored in the storage means;
A light emitting device comprising: The light-emitting device according to claim 1, wherein the measurement unit changes two or more of the light-receiving elements used for measurement of emitted light for each light-emitting element. The measuring means is used for measuring the emitted light so that the relative positions of the light emitting element to be measured for the emitted light and the two or more light receiving elements used for measuring the emitted light are the same. The light emitting device according to claim 1, wherein two or more light receiving elements are selected. 4. The light emitting device according to claim 1, wherein each of the plurality of light receiving elements has the same input / output characteristics. 5. The light emitting device according to claim 1, wherein an arrangement pitch of the plurality of light emitting elements is equal to an arrangement pitch of the plurality of light receiving elements. Each of the plurality of light receiving elements outputs a detection current of a level corresponding to the amount of incident light as the detection signal,
6. The measurement device according to claim 1, wherein the measurement unit uses a current value obtained by adding the detection currents output from each of the two or more selected light receiving elements as the measurement value. The light-emitting device of description. The light-emitting device according to claim 1, wherein the light-receiving element is disposed on both sides of the light-emitting element on both sides of the light-emitting element on the surface of the substrate. . Each of the two light receiving elements disposed on both sides of the light emitting element includes a first region formed by one of a P-type semiconductor and an N-type semiconductor, and the other of the P-type semiconductor and the N-type semiconductor. A second region formed,
8. The light emitting device according to claim 7, wherein in each of the two light receiving elements, the first region is located closer to the light emitting element than the second region. The electronic device provided with the light-emitting device of any one of Claims 1 thru | or 8.

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