JP2006130663A - Optical line head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical line head which corrects a luminous energy difference of every line due to a positioning error with respect to SLA and a difference in the wiring length of each line. <P>SOLUTION: The optical line head is provided with light emitting element lines 5 and 6 in which a plurality of light emitting elements are arranged in a main scanning direction are arranged in a subsidiary scanning direction and forms the image of a linear light source on an irradiated surface through the SLA. A control means is provided with a shift register 2, an anode driver 4, and cathode drivers 9 and 10. A detection means to detect an attachment positioning error for each light emitting element line with respect to the SLA, either the light emitting element line 5 or 6 is chosen from among light emitting element lines on the basis of the result of detection of the detection means and the luminous energy of light emitting elements of the light emitting element line chosen are controlled on a line basis. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical line head using a light emitting element such as an organic EL light emitting element.

  In a tandem or rotary image forming apparatus, a method of providing a scanning optical system as an exposure device and an optical line head method using a light emitting element array are known. For example, Patent Document 1 describes a method using an optical line head in an exposure apparatus. In this example, staggered LEDs are used as the light source, and a gradient index rod lens array (trade name Selfoc lens array, hereinafter abbreviated as SLA) is provided between the light source and the photoconductor. Yes.

  The reason why the light sources are arranged in a staggered manner will be described with reference to FIG. In FIG. 7, light emitting elements 23 a and 23 b of light sources connected to lead wires 21 and 22 are arranged in a staggered manner in the optical line head 20. D is the diameter of the light source, and P is the distance between each light source. In order to secure the optical power of each light emitting portion of the light sources arranged in a line shape, a certain area (namely, diameter D) of the light source is required.

  When the area of the light source is expanded, that is, when the diameter of the light emitting element is increased and the light sources are arranged in a line in the main scanning direction, the length of the optical line head 20 (the length in the main scanning direction). Becomes longer. Therefore, a space for installing the optical line head is required. Therefore, in order to shorten the length of the optical line head 20 in the main scanning direction, a plurality of light emitting element lines in which a plurality of light emitting elements are arranged in the main scanning direction are provided in the sub scanning direction, and the light emitting elements of each light emitting element line are provided. Are arranged in a staggered pattern.

Japanese Patent Laid-Open No. 2-147259

  A problem in the case of using an optical system in which a plurality of rows (two rows in this example) of light emitting element lines are formed in the sub-scanning direction as described in Patent Document 1 will be described with reference to FIG. . In FIG. 8, 24 is the fiber surface of the SLA, and A is the center line of one light emitting element line, and is formed near the center line position in the main scanning direction of the SLA. B is the center line of the other light emitting element line in the main scanning direction. Thus, when using SLA, when two rows of light sources are arranged in the sub-scanning direction, the line of the light source is located directly under the center of the SLA fiber (A), and in the horizontal direction (sub-scanning). (B), the efficiency with which the SLA can capture light differs.

  Compared to the light emitting element line at the position where the center line of the light source is B, as shown in FIG. It is relatively easy to ensure the parallelism between the circuit board on which the light source is mounted and the lens array. For example, a parallel surface is formed with high precision using a molded product of metal or resin, and the circuit board and the lens array are adhered to each other. Just do it.

  As described above, when the light emitting element lines are arranged in two rows in the sub-scanning direction, a light amount difference occurs for each line due to a difference in wiring length and the image quality deteriorates. In order to cope with such a situation, if all the light sources are individually controlled to correct the light amount, it is possible to correct the difference in light amount for each line including the variation in the light amount due to the manufacturing process. However, controlling all the light sources individually to correct the light amount has a problem that the circuit becomes complicated and the cost is increased.

  The present invention has been made in view of such problems in the prior art, and its purpose is to correct a light amount difference for each line due to a positioning error with respect to an SLA and a difference in wiring length of each line with a simple configuration. It is to provide an optical line head.

  In order to achieve the above object, the optical line head according to the first embodiment of the present invention is provided with a plurality of light emitting element lines in the sub-scanning direction in which a plurality of light emitting elements are arranged in the main scanning direction. An optical line head for forming an image of a line-shaped light source on an irradiated surface through a rod lens array (SLA), and a light amount from each light emitting element line based on an attachment position error of each light emitting element line with respect to the SLA It is characterized by comprising selection means for selecting a light emitting element line to be controlled, and control means for controlling the light quantity of the light emitting elements arranged in the light emitting element line selected by the selection means. As described above, in the first embodiment of the present invention, since the mounting position error of each light emitting element line with respect to the SLA is detected and the light amount of the light emitting element is controlled in units of lines, each line has a simple configuration. Can be corrected.

  An optical line head according to the second embodiment of the present invention is provided with a plurality of light emitting element lines arranged in the main scanning direction in which a plurality of light emitting elements are arranged in the sub scanning direction, and the line passes through a gradient index rod lens array (SLA). An optical line head that forms an image of a light source on an irradiated surface, and a selection unit that selects a light emitting element line that performs light amount control for correcting a light amount difference for each column of the plurality of light emitting element lines; And control means for controlling the light quantity of the light emitting elements arranged in the light emitting element line selected by the selecting means. As described above, in the second embodiment of the present invention, since the light amount difference is corrected for each column of the light emitting element lines arranged in a plurality of columns, the light amount difference due to the difference in wiring length or the like is corrected with a simple configuration. it can.

  In the optical line head of the present invention, the control means includes a common driver connected to the anode of each light emitting element and a plurality of drivers connected to the cathode of each light emitting element in line units of the light emitting element line. It is characterized by having. In this embodiment, since the common driver is connected to the anode of each light emitting element, the configuration of the control circuit becomes simpler than connecting the driver individually to the anode of each light emitting element.

  In the optical line head of the present invention, the control means connects a common driver to the cathode of each light emitting element, and connects a different driver to the anode of the light emitting element for each line of the light emitting element line. . In this embodiment, since the common driver is connected to the cathode of each light emitting element, the configuration of the control circuit becomes simpler than connecting the driver individually to the cathode of each light emitting element.

  The optical line head of the present invention is characterized in that the control means is provided with a plurality of serially connected shift registers, and the shift register latches on / off data of each light emitting element. In this embodiment, since the number of signal lines drawn out of the optical line head may be small, the wiring configuration is simplified.

  The optical line head of the present invention is characterized in that the light emitting elements are arranged in a matrix and the light amount is controlled by the control means by time division control. In this embodiment, since the number of drivers connected to each light emitting element can be reduced, the circuit configuration is simplified.

  The optical line head of the present invention divides the light emitting elements arranged in the light emitting element lines into a plurality of blocks in the main scanning direction, and the control means includes a plurality of anode drivers connected to the anodes of the light emitting elements. And a plurality of cathode drivers connected to the cathode of the light emitting element. In this embodiment, the light amount of the light emitting element line can be controlled in units of lines, and the light amount can be controlled in units of blocks, so that it can be applied to various applications.

  The optical line head of the present invention is characterized in that the light emitting elements are arranged in a staggered manner. In this embodiment, in the optical line head in which the light emitting elements are arranged in a staggered manner, the light amount of the light emitting elements can be controlled in line units.

  The optical line head of the present invention is characterized in that an organic EL element is used as the light emitting element. In this embodiment, in an optical line head using an organic EL element as a light emitting element, the light amount of the light emitting element can be controlled in line units.

  According to the optical line head of the present invention, it is possible to correct a positioning error with respect to the SELFOC lens array (SLA) and a light amount difference for each line due to a difference in wiring length of each line with a simple configuration.

  The present invention will be described below with reference to the drawings. FIG. 3 is an enlarged perspective view schematically showing the optical line head 50 according to the embodiment of the present invention. Four optical line heads 50 are installed for each color when used in a full-color image forming apparatus. In FIG. 3, the organic EL element array 61 is held in a long housing 60. The positioning pins 69 provided at both ends of the long housing 60 are fitted into the opposing positioning holes of the case (not shown), and the fixing screws are passed through the screw insertion holes 68 provided at both ends of the long housing 60. Each optical line head 50 is fixed at a predetermined position by being screwed into the screw holes.

  The optical line head 50 mounts, for example, a plurality of rows of light emitting portions 63 of the organic EL element array 61 on the glass substrate 62 in the sub-scanning direction, and is driven by TFTs 71 formed on the same glass substrate 62. The SLA 65 constitutes an imaging optical system, and has a gradient index rod lens (SLA) disposed in front of the light emitting unit 63. Reference numeral 60 denotes a housing, 66 denotes a cover, and 67 denotes a fixed leaf spring. In the present invention, the arrangement of the light emitting element lines is expressed as “column” in the sub-scanning direction and “line (row)” in the main scanning direction.

  The housing 60 covers the periphery of the glass substrate 62, and the side facing the image carrier is open. The light emitting unit 63 is driven, and light is emitted from the fiber surface 70 of the SLA toward the image carrier (not shown). A light-absorbing member (paint) for absorbing unnecessary light is provided on the surface of the housing 60 that faces the end surface of the glass substrate 62.

  FIG. 4 is a plan view showing a partially enlarged arrangement example of the light emitting unit and the rod lens array. In FIG. 4, 70a and 70b are SLA fiber surfaces, and 63a and 63b are light-emitting element lines arranged in a staggered manner in a plurality of rows in the sub-scanning direction. For example, organic EL elements are used as light sources. C. L is a center line of SLA, C and D are center lines of light emitting element lines 63a and 63b, respectively. L is formed so as to be shifted in the sub-scanning direction.

  The present invention provides an optical line head for forming light from light sources arranged in a plurality of rows in the sub-scanning direction on an image carrier, which is an irradiated surface, using an SLA. For each light emitting element line, the amount of light can be controlled in units of light emitting element lines. An example of the configuration of the present invention will be described with reference to the circuit diagram of FIG. In FIG. 1, the control unit 1 of the optical line head forms light emitting element lines 5 and 6 on an LED chip mounted on a substrate. On the substrate, anode drivers 4 are connected corresponding to individual light sources (light emitting elements). Reference numerals 2 and 3 denote serially connected shift registers for transferring data. Reference numerals 7 and 8 denote common cathode lines of the respective light emitting elements.

  The anode driver 4 that controls the light emission of each individual light emitting element is connected to the anode side of the light emitting element as a light source. Also, cathode drivers 9 and 10 are connected to the cathode side of the light emitting elements, and the current value or voltage is controlled independently for each of the light emitting element lines 5 and 6, that is, for each odd and even light emitting element line. In the configuration of FIG. 1, the cathode driver 9 is connected to the common cathode line 7 and controls the light amount of the light emitting elements of the light emitting element lines 5 (odd number). A cathode driver 10 is connected to the common cathode line 8 and controls the light amount of the light emitting elements of the light emitting element line 6 (even number).

  In FIG. 1, an individual driver is connected to the anode side of the light emitting element (anode driver 4), and a common driver common to a plurality of light emitting elements is connected to the cathode side (cathode drivers 9, 10). In a different embodiment of the present invention, instead of such a configuration, the individual driver may be connected to the cathode side of the light emitting element, and the common driver may be connected to the anode side.

  In an optical line head in which a plurality of light emitting elements are arranged in the main scanning direction of the light emitting element line and a driver is provided for each pixel (light emitting element), the control line is also required for each pixel. Wiring becomes complicated. Therefore, as shown in FIG. 1, when the on / off data of each pixel is transferred serially and the on / off data of each pixel is latched by the shift registers 2 and 3, the signal line drawn out of the optical line head is There is an advantage that less is required.

  In the example of FIG. 1, the shift registers 2 and 3 are serially connected in two stages. For example, data for turning on the light emitting elements of the light emitting element lines 5 (odd number lines) and data for turning off the light emitting elements of the light emitting element lines 6 (even number lines) are transferred to the shift register 2 in the preceding stage by the control unit (not shown). Is sent out. This data is latched by the shift register 2, and the same data is transferred to the subsequent shift register 3 and latched.

  Thereafter, by simultaneously outputting the data of the shift registers 2 and 3 to the anode driver 4, the light emitting elements of the light emitting element lines 5 (odd number lines) can be controlled with a predetermined light quantity. Similarly, the on / off data of the light emitting elements on the light emitting element line 6 (even number lines) is latched in the shift registers 2 and 3. Thus, in the example of FIG. 1, the shift registers are serially connected in two stages. For this reason, the amount of data for turning on / off the light emitting elements arranged in one line can be reduced to half.

  As shown in FIG. 1, when an anode driver or a cathode driver is connected to all the light emitting elements, there is a problem that the cost is high and the number of wirings is increased. Therefore, the number of drivers for driving the light emitting elements can be reduced by connecting the light emitting elements in a matrix and performing time division driving. FIG. 2 is a circuit diagram showing another embodiment of the present invention having such a configuration. In FIG. 2, the control unit 11 of the optical line head includes an anode driver 12 (AD1 to AD4), an anode control line 13, light emitting element lines 15 and 16, common cathode lines 17 and 18, and a cathode driver 19a (CD1, CD2). Cathode drivers 19b (CD3, CD4) are provided. The anode control line 13 is wired in four lines a to d.

  In the configuration shown in FIG. 2, for example, by controlling the voltages of the cathode drivers CD <b> 1 and CD <b> 3, the light amount of each light emitting element of the light emitting element line 15 can be changed. Further, by controlling the voltages of the cathode drivers CD2 and CD4, the light quantity of each light emitting element of the light emitting element line 16 can be changed. In this way, by controlling the voltages of the cathode drivers CD1 to CD4, the light quantity of the light emitting element lines arranged in two rows can be easily changed for each line.

  In the example of FIG. 2, the light emitting element lines 15 and 16 are divided into two blocks X and Y in the main scanning direction. The light emitting elements of the light emitting element line 15 of the block X are connected to the cathode driver CD1, and the light emitting elements of the light emitting element line 16 of the block X are connected to the cathode driver CD2. The light emitting elements of the light emitting element line 15 of the block Y are connected to the cathode driver CD3, and the light emitting elements of the light emitting element line 16 of the block Y are connected to the cathode driver CD4.

  The anode driver AD1 is connected to the anode control line a, and the anode driver AD2 is connected to the anode control line b. The anode driver AD3 is connected to the anode control line c, and the anode driver AD4 is connected to the anode control line d. The light emitting elements are arranged in a matrix and are time-division controlled by the anode drivers AD1 to AD4 and the cathode drivers CD1 to CD4.

  That is, when a signal is applied to the anode drivers AD1 to AD4 at a certain timing and the voltage of the cathode driver CD1 is controlled, the light amount of the light emitting element line 15 of the block X is controlled. At the same time, when the voltage of the cathode driver CD3 is controlled, the light amount of the light emitting element line 15 of the block Y is also controlled. Next, when the voltage of the cathode driver CD2 is controlled with a signal applied to the anode drivers AD1 to AD4 at a different timing, the light amount of the light emitting element line 16 of the block X is controlled. At the same time, when the voltage of the cathode driver CD4 is controlled, the light amount of the light emitting element line 16 of the block Y is also controlled.

  With such a configuration, by changing the voltage of either the cathode driver CD1 or CD2 in a state where a signal is applied to the anode drivers AD1 to AD4, the light emitting element lines 15 and 16 of the block X are changed. The light quantity of any one of the light emitting elements can be controlled. Further, by changing the voltage of either the cathode driver CD3 or CD4 in a state where a signal is applied to the anode drivers AD1 to AD4, the light emitting element lines 15 and 16 of the block Y can be changed. The amount of light can be controlled.

  That is, when the voltages of the cathode drivers CD1 to CD4 are changed in a state where signals are applied to the anode drivers AD1 to AD4, the light amount control of the light emitting elements of all the light emitting element lines 15 and 16 can be performed. . The light emitting elements of the blocks X and Y are changed by changing the voltages of the cathode drivers CD1 and CD2 or changing the voltages of the cathode drivers CD3 and CD4 in a state where signals are applied to the anode drivers AD1 to AD4. The light quantity control can be selected and performed. Therefore, according to the configuration of FIG. 2, it is possible to perform light amount control of all the light emitting elements of one line and light amount control of half of the light emitting elements of one line.

  In the example of FIGS. 1 and 2, an LED is used as the semiconductor light emitting element of the light source, but other than the light source, FL (fluorescent tube), EL light emitting element (organic or inorganic), etc. may be combined. For example, when a driver formed by a TFT process on a glass substrate and an organic EL light emitting element are combined, the driver and the light emitting portion can be integrally formed on the glass substrate.

FIG. 5 is a cross-sectional view showing a configuration example in the vicinity of the light emitting portion 63 of the organic EL light emitting element array 61 shown in FIG. The organic EL light emitting element array 61 includes, for example, two rows of TFTs (thin film transistors) 71 made of polysilicon having a thickness of 50 nm for controlling the light emission of each light emitting portion 63 on a glass substrate 62 having a thickness of 0.5 mm. Corresponding to each of the light emitting portions 63, the outer margin is provided. An insulating film 72 made of SiO ₂ having a thickness of about 100 nm is formed on the glass substrate 62 excluding the contact hole on the TFT 71, and is thick at the position of the light emitting portion 63 so as to be connected to the TFT 71 through the contact hole. An anode 73 made of ITO having a thickness of 150 nm is formed.

Next, another insulating film 74 made of SiO ₂ having a thickness of about 120 nm is formed in a portion corresponding to a position other than the light emitting portion 63, and a hole 76 corresponding to the light emitting portion 63 is formed thereon, and the thickness is 2 μm. A partition wall 75 made of polyimide is provided. A hole injection layer 77 having a thickness of 50 nm and a light emitting layer 78 having a thickness of 50 nm are formed in order from the anode 73 side in the hole 76 of the partition wall 75, and the upper surface of the light emitting layer 78, the inner surface of the hole 76, and the partition wall. A cathode first layer 79a made of Ca having a thickness of 100 nm and a cathode second layer 79b made of Al having a thickness of 200 nm are sequentially formed so as to cover the outer surface of 75.

  Then, the light emitting portion 63 of the organic EL light emitting element array 61 is configured by being covered with a cover glass 64 having a thickness of about 1 mm via an inert gas 80 such as nitrogen gas. Light emission from the light emitting unit 63 is performed on the glass substrate 62 side. Various known materials can be used as the material used for the light emitting layer 78 and the material used for the hole injection layer 77, and detailed description thereof is omitted. Such an organic EL light emitting element can be easily manufactured on a glass substrate, and thus the manufacturing cost can be reduced.

  When an organic EL light emitting element is used for the light emitting part of the optical line head, the light emitting pixel column is manufactured using a semiconductor process on a single substrate, and therefore, its linearity is much higher than that of a conventional LED. It is possible to configure with high accuracy. Furthermore, the light amount unevenness of the light emitting element itself is also smaller than the transmitted light amount unevenness of the lens array, and if the center line of the lens array and the light emitting element row can be positioned with high accuracy, the light amount can be made uniform without light amount correction, The spot diameter is also uniform. For this reason, a high-quality optical line head can be configured.

  FIG. 6 is a block diagram showing the overall configuration of the control unit of the optical line head. In FIG. 6, 101 is a control unit of the optical line head, 103 is a memory, 104 is a control circuit, and 105 is a drive circuit comprising TFTs. Reference numeral 106 denotes a light emitting element line in which light emitting elements are arranged in one line (main scanning direction), and only one line is described in the main scanning direction for simplicity. Reference numeral 100 denotes a main body controller. The main body controller 100 forms print data and transmits it to the control unit 101 of the optical line head.

  The optical line head is attached to a misalignment measuring instrument, and the misalignment amount between the center position of the SLA and the center line position of each light emitting element line is measured. The memory 103 stores the amount of positional deviation. The control circuit 104 reads out the detected value of the amount of misalignment detected by the misregistration measuring device from the memory 103 and calculates a correction light amount with respect to the reference light amount. Based on this calculation result, a signal is sent to the drive circuit 104, and the applied voltage or drive current of the light emitting element is controlled to correct the light amount of the light emitting element line on a line basis.

  Further, the light amount of the light beam emitted from the optical line head is measured for each light emitting element line, the measured value is stored in the memory 103, the light amount measured value is read from the memory 103 by the control circuit 104, and each light emitting element is read. It is also possible to correct the light amount difference for each line.

  As a modification of the present invention, the present invention can be applied to an optical line head in which three or more light emitting element lines are formed in the sub-scanning direction. Further, instead of arranging the light sources in a plurality of rows, a configuration in which a plurality of light shutters (light valves) are installed may be adopted.

  Although the optical line head of the present invention has been described based on some embodiments, the present invention is not limited to these embodiments and can be variously modified.

It is a circuit diagram of the optical line head of the present invention. It is a circuit diagram concerning other embodiments of the present invention. It is a perspective view of an optical line head. It is sectional drawing which shows a part of optical line head partially. It is sectional drawing which shows the example of an organic EL element array. It is a block diagram which shows embodiment of this invention. It is explanatory drawing which shows the example of the light emission part of an optical line head. It is explanatory drawing which shows the example of arrangement | positioning of SLA and a light emission part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,11 ... Control part of optical line head 2,3 ... Shift register 4,12 ... Anode driver 5,6,15,16 ... Light emitting element row | line | column, 7,8,17 , 18 ... common cathode line, 9, 10 ... cathode driver, 13 ... anode control line, 61 ... organic EL element array, 62 ... glass substrate, 63 ... light emitting part, 64 ... Cover glass, 65 ... Gradient index rod lens array (SLA), 70 ... Fiber

Claims (9)

An optical line head in which a plurality of light emitting element lines in which a plurality of light emitting elements are arranged in the main scanning direction is provided in a plurality of rows in the sub scanning direction, and an image of a linear light source is formed on an irradiated surface through a gradient index rod lens array (SLA) A light-emitting element line selected by the light-emitting element line selected from the light-emitting element lines based on an attachment position error of the light-emitting element lines with respect to the SLA; An optical line head comprising: control means for controlling the amount of light emitted from the light emitting elements arranged on the optical line head. An optical line head in which a plurality of light emitting element lines in which a plurality of light emitting elements are arranged in the main scanning direction is provided in a plurality of rows in the sub scanning direction, and an image of a linear light source is formed on an irradiated surface through a gradient index rod lens array (SLA) A selection unit that selects a light emitting element line that performs light amount control for correcting a light amount difference for each column of the plurality of light emitting element lines, and a light emission arrayed in the light emitting element line selected by the selection unit. An optical line head comprising control means for controlling the amount of light of the element. The control unit includes a common driver connected to an anode of each light emitting element, and a plurality of drivers connected to a cathode of each light emitting element in line units of the light emitting element line. Or the optical line head of Claim 2. The said control means connects a common driver to the cathode of each light emitting element, and connects a different driver to the anode of a light emitting element for every line unit of the said light emitting element line, The Claim 1 or Claim 2 characterized by the above-mentioned. Light line head. 5. The control unit according to claim 1, wherein the control unit includes a plurality of serially connected shift registers, and the shift register latches on / off data of each light emitting element. The optical line head described. 2. The optical line head according to claim 1, wherein the light emitting elements are arranged in a matrix and the light amount is controlled by the control means by time division control. 3. The light emitting elements arranged in the light emitting element lines are divided into a plurality of blocks in the main scanning direction, and the control means is connected to a plurality of anode drivers connected to the anode of the light emitting elements and a cathode of the light emitting elements. The optical line head according to claim 6, further comprising a plurality of cathode drivers. 8. The optical line head according to claim 1, wherein the light emitting elements are arranged in a zigzag pattern. The optical line head according to any one of claims 1 to 8, wherein an organic EL element is used as the light emitting element.

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