Light emitting device and optical write device and image forming system using the same

Abstract

A light emitting device, a light writing device, and an image forming system using the light emitting device, the light emitting device including: a light source unit in which a plurality of light emitting elements are arranged in a main scanning direction on a substrate; and a driving unit that drives the plurality of light emitting elements in a manner that changes a light emitting time width in accordance with an amount of light to be emitted and causes the plurality of light emitting elements to emit light at different timings within a predetermined period, the driving unit having a correction unit that corrects within a range of a correctable width in which the light emitting time width is correctable, and causes the correctable width of each of the light emitting elements to be different.

Description

Technical Field

[0001] This invention relates to a light-emitting device and a light-writing device and an image forming system using the light-emitting device. Background Technology

[0002] As existing light-emitting devices, for example, the light-emitting devices described in Patent Documents 1 to 3 are known.

[0003] Patent Document 1 discloses a light-emitting element head that includes a control unit, which illuminates the LEDs using a plurality of times less than the first time when the illumination time of each of the plurality of LEDs exceeds the first time.

[0004] Patent document 2 discloses a light-emitting device that corrects the light intensity of each group of light-emitting elements by increasing or decreasing the voltage in each group, thereby correcting the concentration unevenness in the main scanning direction.

[0005] Patent document 3 discloses an exposure apparatus comprising a time-changing unit. The time-changing unit changes the time based on a cycle time of switching signals of a plurality of light-emitting elements driven by a driving element, which are sequentially switched in accordance with the image forming speed. In a main scan, the time-changing unit changes the time based on a cycle time for a portion of the light-emitting elements, and maintains the time based on a cycle time for the remaining portion.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-030427 (Detailed Embodiments) Figure 11 , Figure 12 )

[0007] Patent Document 2: Japanese Patent Application Publication No. 2022-053039 (Detailed Embodiments) Figure 11 )

[0008] Patent Document 3: Japanese Patent Application Publication No. 2010-184448 (Detailed Embodiments) Figure 19 ) Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a light-emitting device that can ensure the required light amount adjustment width of each light-emitting element within a predetermined period of time, even when the transmission period of the driving signal given to each light-emitting element is shortened, and a light writing device and an image forming system using the light-emitting device.

[0010] The first technical feature of the present invention is a light-emitting device, characterized in that it comprises: a light source unit having a plurality of light-emitting elements arranged on a substrate along a main scanning direction; and a driving unit that drives the plurality of light-emitting elements to emit light by changing the light emission time width according to the amount of light to be emitted at different timings within a predetermined period of time, wherein the driving unit has a correction unit that performs correction within the correctable range of the light emission time width, i.e., within the range of the correctable width, and makes the correctable width of each of the light-emitting elements different.

[0011] The second technical feature of the present invention is a light-emitting device having the first technical feature, characterized in that the correction unit corrects the light-emitting elements in which the predicted light amount variation is large, such that the correctable width of the light-emitting elements is larger than the correctable width of the light-emitting elements in which the predicted light amount variation is small.

[0012] The third technical feature of the present invention is a light-emitting device having the second technical feature, characterized in that the correction unit corrects light-emitting elements in which the predicted change in light amount is greater than a predetermined reference change in amount, such that the correctable width is greater than a predetermined reference value; and corrects light-emitting elements in which the predicted change in light amount is less than the reference change in amount, such that the correctable width is less than the reference value.

[0013] The fourth technical feature of the present invention is a light-emitting device having any one of the first to third technical features, characterized in that it includes a power supply unit disposed on the side of the end of the light source unit in the main scanning direction in the substrate, which supplies power to each light-emitting element, and the correction unit makes the correctable width different according to the distance between the power supply unit and the light-emitting element or the wiring length.

[0014] The fifth technical feature of the present invention is a light-emitting device having the fourth technical feature, characterized in that the correction unit performs correction in such a way that the longer the distance or wiring length between the power supply unit and the light-emitting element, the longer the correctable width.

[0015] The sixth technical feature of the present invention is a light-emitting device having any one of the first to third technical features, characterized in that it includes a resistor unit disposed on the side of the end of the light source unit in the main scanning direction in the substrate, which limits the current supplied to the light-emitting element.

[0016] The correction unit adjusts the correctable width of the light-emitting element according to the distance between the resistor unit and the light-emitting element.

[0017] The seventh technical feature of the present invention is a light-emitting device having the sixth technical feature, characterized in that the correction unit corrects the light-emitting element in such a way that the shorter the distance between the resistor unit and the light-emitting element, the longer the correctable width of the light quantity.

[0018] The eighth technical feature of the present invention is a light-emitting device having any one of the first to third technical features, characterized in that it comprises: a power supply unit disposed on the side of the end of the light source unit in the main scanning direction in the substrate, for supplying power to each light-emitting element; and a resistor unit disposed on the side of the end of the light source unit in the main scanning direction in the substrate, for limiting the current supplied to the light-emitting element, wherein the power supply unit is disposed on the side opposite to the resistor unit across the light source unit, and the correction unit makes the correctable width different according to the distance between the power supply unit and the light-emitting element or the wiring length and the distance between the resistor unit and the light-emitting element.

[0019] The ninth technical feature of the present invention is a light-emitting device having the third technical feature, characterized in that, when the correction unit corrects the correctable width of each of the light-emitting elements, it includes a first correctable width group greater than the reference value and a second correctable width group less than the reference value, and corrects the correctable width in such a way that the total difference between the first correctable width group and the reference value and the total difference between the second correctable width group and the reference value are of the same degree.

[0020] The tenth technical feature of the present invention is a light-emitting device having any one of the technical features from the first to the ninth, characterized in that, in the light source unit, the plurality of light-emitting elements are arranged in a plurality of groups, and the correction unit makes the correctable width of each of the light-emitting elements in the group different in parallel.

[0021] The 11th technical feature of the present invention is a light-emitting device having the 10th technical feature, characterized in that the light source unit is composed of multiple systems that use a common driving signal for each identical group unit, and the correction unit performs in parallel the correction processing of the correctable width of the light-emitting element belonging to the group unit of any one system and the correction processing of the correctable width of the light-emitting element belonging to the group unit of other systems.

[0022] The 12th technical feature of the present invention is a light writing device, characterized in that it comprises: a light-emitting device having any one of the technical features 1 to 11, disposed opposite to an image holding unit capable of holding a light-based image; and an imaging unit that images light irradiated from each light-emitting element of the light-emitting device onto the image holding unit and writes a light-based image to the image holding unit.

[0023] The 13th technical feature of the present invention is an image forming system, characterized in that it comprises: an image holding unit capable of holding a light-based image; and a light writing device having the 12th technical feature, capable of visualizing and outputting the light-based image held by the image holding unit.

[0024] Invention Effects

[0025] According to the first technical feature of the present invention, even when the transmission period of the driving signal supplied to each light-emitting element is shortened, the required light intensity adjustment width of each light-emitting element can be ensured within a predetermined period.

[0026] According to the second technical feature of the present invention, compared with a light-emitting element with a small predicted change in light amount, a light-emitting element with a large predicted change in light amount can have a wider correctable width, thereby ensuring the required light amount adjustment width.

[0027] According to the third technical feature of the present invention, for light-emitting elements that are predicted to have a large amount of light quantity variation and light-emitting elements that are predicted to have a small amount of light quantity variation, the correctable width is expanded or reduced with a predetermined reference value as the boundary, thereby enabling the appropriate allocation of the required light quantity adjustment width.

[0028] According to the fourth technical feature of the present invention, the distance or wiring length between the power supply unit and the light-emitting element is considered as the factor for the variation of the light amount of the light-emitting element, thereby enabling the appropriate allocation of the required light amount adjustment width to each light-emitting element with different light amount variations.

[0029] According to the fifth technical feature of the present invention, when the distance or wiring length between the power supply unit and the light-emitting element is long, the adjustable width of the light-emitting element with a long distance or wiring length can be further extended compared with that of a light-emitting element with a short distance or wiring length, thereby ensuring the required light quantity adjustment width.

[0030] According to the sixth technical feature of the present invention, the distance between the resistive unit, which functions as a heat source, and the light-emitting element is considered as the factor affecting the variation of the light amount of the light-emitting element. This allows for the appropriate allocation of the required light amount adjustment width to each light-emitting element with different variations in light amount.

[0031] According to the seventh technical feature of the present invention, when the distance between the resistor unit and the light-emitting element is short, the adjustable width of the light-emitting element with a short distance can be extended more than that of the light-emitting element with a long distance, thereby ensuring the required light amount adjustment width.

[0032] According to the eighth technical feature of the present invention, even in a form that includes a power supply unit and a resistor unit that functions as a heat source, the maximum amount of light variation can be suppressed by designing the positional relationship between the power supply unit and the resistor unit, and by considering the distance between the power supply unit and the light-emitting element or the wiring length and the distance between the resistor unit and the light-emitting element. Furthermore, the required light amount adjustment width can be appropriately allocated to each light-emitting element with different amounts of light variation within a predetermined period.

[0033] According to the ninth technical feature of the present invention, for light-emitting elements that are predicted to have large variations in light intensity and light-emitting elements that are predicted to have small variations in light intensity, the total correction amount for expanding the correctable width and the total correction amount for reducing the correctable width are set to the same degree, based on a predetermined reference value. This allows for the appropriate allocation of the required light intensity adjustment width to each light-emitting element with different variations in light intensity within a predetermined period.

[0034] According to the tenth technical feature of the present invention, compared with the configuration in which multiple light-emitting elements are not arranged in groups, it is possible to share an adjustable width among multiple light-emitting elements in groups and to quickly perform the expansion and reduction of the adjustable width.

[0035] According to the 11th technical feature of the present invention, even for a light source unit of multiple systems in which multiple light-emitting elements are arranged in an interleaved manner according to each group unit and each uses a common driving signal, it is possible to quickly perform the expansion and reduction processing of the correctable width for multiple light-emitting elements in each system.

[0036] According to the 12th technical feature of the present invention, it is possible to construct an optical writing device including a light-emitting device, which can ensure the required light intensity adjustment width for each light-emitting element even when the transmission period of the driving signal supplied to each light-emitting element is shortened.

[0037] According to the 13th technical feature of the present invention, it is possible to construct an image forming system including a light-emitting device that can ensure the required light intensity adjustment width for each light-emitting element even when the transmission period of the driving signal supplied to each light-emitting element is shortened. Attached Figure Description

[0038] The embodiments of the present invention will be described in detail with reference to the following figures.

[0039] Figure 1 middle, Figure 1 (a) is an explanatory diagram showing a general outline of an embodiment of an image forming system in which the light-emitting device of the present invention is applied. Figure 1 (b) means Figure 1(a) is a schematic diagram illustrating the structure of an example of a light-emitting device. Figure 1 (c) is an explanatory diagram showing an example of the variation in the amount of light emitted as a result of the arrangement of the light-emitting elements in the accompanying light source unit. Figure 1 (d) indicates the accompanying Figure 1 (c) is an explanatory diagram illustrating the principle of light quantity correction for the variation in light emission of each light-emitting element.

[0040] Figure 2 This is an explanatory diagram showing a structural example of the image forming system according to Embodiment 1;

[0041] Figure 3 It means as Figure 2 An explanatory diagram of an example of an exposure unit used in the image forming system shown;

[0042] Figure 4 middle, Figure 4 (a) means Figure 3 The diagram illustrates an example of the structure of the light-emitting element chip array used in an LED printhead. Figure 4 (b) means Figure 4 (a) is an illustration of the configuration relationship of the light-emitting element chips in the light-emitting element chip array.

[0043] Figure 5 It is an explanatory diagram showing the various signals from the signal generation circuit that are input to the light-emitting element chip array;

[0044] Figure 6 This is a block diagram illustrating an example of the structure of a signal generation circuit;

[0045] Figure 7 middle, Figure 7 (a) means Figure 6 The diagram illustrates an example of the structure of the timing signal generation section of the signal generation circuit shown. Figure 7 (b) is an explanatory diagram showing an example of the transmission period setting data DT2 input to the timing signal generation unit;

[0046] Figure 8 middle, Figure 8 (a) is an explanatory diagram showing an example of the structure of a light-emitting element chip. Figure 8 (b) is an explanatory diagram showing the heat source surrounding the light-emitting element chip and the direction of power supply to the light-emitting element. Figure 8 (c) is an explanatory diagram showing the influence of the heat source and power supply direction on the light intensity variation of each light-emitting element in the light-emitting element chip. Figure 8 (d) is an explanatory diagram illustrating the principle of light quantity variation correction of the light-emitting element chip;

[0047] Figure 9 This is an explanatory diagram showing an example of the circuit structure of a light-emitting element chip;

[0048] Figure 10 middle, Figure 10 (a) means Figure 6 An illustrative diagram illustrating the light distribution of the light-emitting element chip before concentration non-uniformity correction. Figure 10 (b) means Figure 6 An illustrative diagram illustrating the light distribution of the light-emitting element chip after concentration non-uniformity correction. Figure 10 (c) is an illustration of the principle of concentration non-uniformity correction;

[0049] Figure 11 middle, Figure 11 (a) is an explanatory diagram showing the lighting / extinguishing behavior of the light-emitting element when the transmission period TS of the transmitted signal is TSa. Figure 11 (b) is an illustration of the lighting / extinguishing behavior of the light-emitting element when the transmission period TS of the transmitted signal is TSb (TSb < TSa).

[0050] Figure 12 middle, Figure 12 (a) is an explanatory diagram showing the relationship between the amount of light correction required for the change in light quantity of each light-emitting element of the light-emitting element chip due to the heat source and power supply direction, and the position of each light-emitting element. Figure 12 (b) means to ensure Figure 12 A diagram illustrating the methods for each correction amount shown in (a);

[0051] Figure 13 middle, Figure 13 (a) is an explanatory diagram showing the relationship between the transmission signal to each light-emitting element and the lighting signal to each light-emitting element in this embodiment. Figure 13 (b) is an explanatory diagram showing the relationship between the transmission signal to each light-emitting element and the lighting signal to each light-emitting element in the comparison method;

[0052] Figure 14 middle, Figure 14 (a) is an explanatory diagram showing an example of the structure of the light-emitting element chip for an exposure unit according to Embodiment 2. Figure 14 (b) is an explanatory diagram showing the heat source surrounding the light-emitting element chip and the direction of power supply to the light-emitting element. Figure 14 (c) is an explanatory diagram showing the influence of the heat source and power supply direction on the light quantity variation of each light-emitting element in the light-emitting element chip;

[0053] Figure 15 middle, Figure 15(a) is an explanatory diagram showing the relationship between the amount of light correction required for the change in light quantity of each light-emitting element of the light-emitting element chip due to the heat source and power supply direction, and the position of each light-emitting element. Figure 15 (b) means to ensure Figure 15 A diagram illustrating the methods for each correction amount shown in (a);

[0054] Figure 16 middle, Figure 16 (a) is an explanatory diagram showing an example of the structure of the light-emitting element chip for an exposer according to Embodiment 3. Figure 16 (b) is an explanatory diagram showing the heat source surrounding the light-emitting element chip and the direction of power supply to the light-emitting element. Figure 16 (c) is an explanatory diagram showing the influence of the heat source and power supply direction on the light quantity variation of each light-emitting element in the light-emitting element chip;

[0055] Figure 17 middle, Figure 17 (a) is an explanatory diagram showing an example of the structure of the light-emitting element chip for the illuminator according to Embodiment 4. Figure 17 (b) is an explanatory diagram showing the heat source surrounding the light-emitting element chip and the direction of power supply to the light-emitting element. Figure 17 (c) is an explanatory diagram showing the influence of the heat source and power supply direction on the light quantity variation of each light-emitting element in the light-emitting element chip;

[0056] Figure 18 middle, Figure 18 (a) is an explanatory diagram showing an example of the structure of the light-emitting element chip for an exposer according to Embodiment 5. Figure 18 (b) is an explanatory diagram showing the heat source surrounding the light-emitting element chip and the direction of power supply to the light-emitting element. Figure 18 (c) is an explanatory diagram showing the influence of the heat source and power supply direction on the light quantity variation of each light-emitting element in the light-emitting element chip;

[0057] Figure 19 middle, Figure 19 (a) is an explanatory diagram showing a structural example of the light-emitting element chip array for an exposer according to Embodiment 6. Figure 19 (b) is an explanatory diagram showing the heat sources surrounding the light-emitting element chips in even-numbered columns and the direction of power supply to the light-emitting elements. Figure 19 (c) is an explanatory diagram showing the effect of the heat source and power supply direction on the light quantity variation of each light-emitting element in the odd-numbered light-emitting element chip;

[0058] Figure 20 middle, Figure 20(a) is an explanatory diagram showing the relationship between the correction amount of light intensity required for light intensity changes in each light-emitting element of the even-numbered column of the light-emitting element chip in terms of heat source and power supply direction, and the position of each light-emitting element. Figure 20 (b) is an explanatory diagram showing an example of correction processing for changes in the light intensity of light-emitting element chips in even-numbered columns, indicating the direction of heat source and power supply. Figure 20 (c) is an explanatory diagram showing the relationship between the amount of light correction required for the change in light intensity of each light-emitting element in the odd-numbered column of the light-emitting element chip due to the heat source and power supply direction, and the position of each light-emitting element. Figure 20 (d) is an explanatory diagram illustrating an example of the correction process for the change in light intensity of the odd-numbered light-emitting element chips due to the direction of heat source and power supply.

[0059] Symbol Explanation

[0060] 1-Light emission device, 2-Light source unit, 3-Light emission element, 5-Driving unit, 6-Correction unit, 8-Substrate, 9-Imaging unit, 10-Image forming system, 11-Light writing device, 12-Image holding unit, 13-Power supply unit, 14-Resistor unit, U-Light emission element chip. Detailed Implementation

[0061] ◎Summary of Implementation Methods

[0062] Figure 1 (a) represents a summary of an embodiment of the image forming system to which the present invention is applied.

[0063] In this figure, the image forming system 10 includes a light writing device 11 and an image holding unit 12 disposed opposite to the light writing device 11 and holding a light-based image.

[0064] Here, the optical writing device 11 includes a light-emitting device 1 and an imaging unit 9 that images the light emitted from each light-emitting element chip U of the light-emitting device 1 onto the image holding unit 12.

[0065] The image holding unit 12 mentioned here is not limited to a photoreceptor, but also includes dielectrics, etc., and its shape can be appropriately selected as a roller, strip, etc. Furthermore, light-based images can be exemplified by electrostatic latent images formed by removing the charge from an image after it has been charged to a specified level and then by light corresponding to the image pattern, resulting in a potential difference.

[0066] Furthermore, regarding the imaging unit 9, any imaging unit that images the light emitted from each light-emitting element chip U of the light-emitting device 1 onto the image holding unit 12 can be appropriately selected. For example, a lens that refracts light on a surface (e.g., a cylindrical lens) or a lens that refracts light internally (e.g., a refractive index distribution lens) can be cited.

[0067] And, as Figure 1 As shown in (b), the light-emitting device 1 includes: a light source unit 2, on which a plurality of light-emitting elements 3 are arranged along the main scanning direction on a substrate 8; and a driving unit 5, which drives the plurality of light-emitting elements 3 to emit light by changing the emission time width according to the amount of light to be emitted at different timings within a predetermined period. Furthermore, the driving unit 5 has a correction unit 6, which performs correction within a correctable range (i.e., a correctable width) of the emission time width, and makes the correctable width different for each light-emitting element 3.

[0068] In addition, Figure 1 In (b), symbol 13 is a power supply unit that supplies drive signals from drive unit 5 to each light-emitting element 3 of light source unit 2, and symbol 14 is a resistor unit that limits the current supplied to each light-emitting element 3.

[0069] In this technique, the light source unit 2 can be an array of multiple light-emitting elements 3 arranged along the main scanning direction. Examples of light-emitting elements 3 include light-emitting thyristors and light-emitting diodes. Furthermore, the multiple light-emitting elements 3 can be arranged as multiple light-emitting element chips U, or the light-emitting element chips U can be arranged in an alternating pattern or in three or more columns. It also includes arrangements where multiple light-emitting elements 3 are arranged in an alternating pattern or in three or more columns within each light-emitting element chip U.

[0070] Furthermore, the driving unit 5 only needs to drive the multiple light-emitting elements 3 at different timings within a predetermined period. In this case, the driving method can be such that the multiple light-emitting elements 3 are driven by changing the emission time width according to the amount of light to be emitted, thus causing the multiple light-emitting elements 3 to emit light. Here, the amount of light to be emitted can be fixed in advance or variably selected.

[0071] Furthermore, in this example, the driving unit 5 only needs to have a correction unit 6 that can perform correction within the range of the correctable width of the light emission time width. Here, the correction unit 6 needs to make the correctable width Th different for each light-emitting element 3. Therefore, the correctable width Th is not a predetermined constant value, but an appropriate correctable width Th is selected for each light-emitting element 3.

[0072] The light-emitting device 1, which has the structural elements described above, functions as follows.

[0073] Typically, due to manufacturing deviations or variations in the transmittance of the imaging unit 9, the amount of light in the main scanning direction of a light source unit 2 with multiple light-emitting elements 3 will vary, resulting in uneven density (stripes of light in the image). Therefore, to ensure image quality, it is necessary to correct the uneven density for each light-emitting element 3.

[0074] In this example, the driving unit 5 uses a method that changes the emission time width according to the amount of light to be emitted and causes the light-emitting element to emit light. Therefore, in order to perform light quantity correction, it is basically only necessary to adjust the emission time width for each light-emitting element 3.

[0075] However, if the printing speed of the image forming system 10 increases, the writing speed of the light writing device 11 needs to be increased accordingly. In this case, as the light-emitting device 1, there is a concern that the light-emitting time assigned to each light-emitting element 3 becomes shorter, and the insufficient width Th can be corrected if the light-emitting time width is within a correctable range.

[0076] That is, the aforementioned calibrable width Th is determined based on the transmission period of the driving signal for each light-emitting element 3. However,

[0077] If the transmission period of the driving signal is determined to be a uniform reference transmission period as in the past, then in the light-emitting element 3, which is predicted to have a large amount of variation in light quantity, there is a concern about insufficient correctable width Th.

[0078] Therefore, the inventors studied the light quantity variation characteristics of the light source unit 2 in the light-emitting device 1 that has undergone light quantity correction processing for uneven concentration, and obtained the following results.

[0079] That is, in the light source unit 2 with multiple light-emitting elements 3 arranged in a row, the amount of light changes according to the arrangement position of the light-emitting elements 3.

[0080] exist Figure 1 In example (b), the characteristic of the slope of light intensity gradually decreasing from the first of the multiple light-emitting elements 3 toward the last j-th light-emitting element 3 was confirmed (see reference). Figure 1 (c)).

[0081] exist Figure 1 In (c), it is assumed that the light intensity of the final j-th light-emitting element 3 exhibits a characteristic of decreasing by a slope ΔP compared to the light intensity of the first light-emitting element 3. To correct for this light intensity variation, such as... Figure 1 As shown in (d), for example, it is preferable to allocate a sufficiently large amount of light correction to the j-th light-emitting element 3 compared to the amount of light correction to the first light-emitting element 3.

[0082] That is, in Figure 1 In the example shown in (d), in the light-emitting element 3 on the side predicted to have a larger amount of light correction, the correctable width Th is extended to Th. up On the other hand, in the light-emitting element 3, which is predicted to have a smaller amount of light correction, the correctable width Th is reduced to Th. dw .

[0083] In this case, if the correctable width Th is extended, for example, the transmission period TS of the drive signal can be extended. On the other hand, if the correctable width Th is reduced, for example, the transmission period TS of the drive signal can be reduced. In this case, the transmission period of the drive signal for each light-emitting element 3 can be adjusted so that the total transmission period of the drive signal in one line segment becomes a predetermined period.

[0084] Next, a representative or preferred form of the light-emitting device involved in this embodiment will be described.

[0085] First, as a representative form of the correction unit 6, the following form can be given: for the light-emitting element 3, which is predicted to have a large amount of light variation, correction is performed in such a way that its correctable width Th is greater than that of the light-emitting element 3, which is predicted to have a small amount of light variation.

[0086] In this example, the preferred correction unit 6 can be configured as follows: for light-emitting elements 3 in which the predicted change in light amount is greater than the predetermined reference change, correction is performed in such a way that the correctable width Th is longer than the predetermined reference value; for light-emitting elements 3 in which the predicted change in light amount is less than the reference change, correction is performed in such a way that the correctable width Th is shorter than the reference value.

[0087] In this type of correction unit 6, when correcting the correctable width Th of each light-emitting element 3, there are a first correctable width group that is greater than the reference value and a second correctable width group that is less than the reference value. For example, it is preferable to correct the correctable width Th in such a way that the sum of the differences between the first correctable width group and the reference value and the sum of the differences between the second correctable width group and the reference value are of the same degree.

[0088] And, as Figure 1 As shown in (b), in the configuration of a power supply unit 13 located on the side of the end of the light source unit 2 in the main scanning direction of the substrate 8 and supplying power to each light-emitting element 3, the correction unit 6 can simply adjust the correctable width Th according to the distance between the power supply unit 13 and the light-emitting element 3 or the wiring length. This is designed with the consideration that the power supply direction of the power supply unit 13 becomes a factor affecting the variation in the amount of light emitted by each light-emitting element 3.

[0089] In this example, the correction unit 6 preferably performs correction in such a way that the longer the distance between the power supply unit 13 and the light-emitting element 3 or the wiring length, the longer the correction width Th is.

[0090] Moreover, such as Figure 1As shown in (b), in the configuration where a resistor unit 14 is located to the side of the end of the light source unit 2 in the main scanning direction and restricts the current supplied to the light-emitting element 3, the correction unit 6 can simply adjust the correctable width Th of the light-emitting element 3 according to the distance between the resistor unit 14 and the light-emitting element 3. This is designed with the consideration that the resistor unit 14 becomes a heat source and thus a factor affecting the variation of the light amount of each light-emitting element 3.

[0091] In this example, the correction unit 6 preferably performs correction in such a way that the shorter the distance between the resistor unit 14 and the light-emitting element 3, the longer the correctable width Th of the light amount of the light-emitting element 3.

[0092] Furthermore, in a configuration where a power supply unit 13 is provided on the side of the end of the light source unit 2 in the main scanning direction of the substrate 8 and supplies power to each light-emitting element 3, and a resistor unit 14 is provided on the side of the end of the light source unit 2 in the main scanning direction of the substrate 8 and restricts the current supplied to the light-emitting element 3, and the power supply unit 13 is disposed on the side opposite to the resistor unit 14 across the light source unit 2, the correction unit 6 can simply make the correctable width Th different according to the distance between the power supply unit 13 and the light-emitting element 3 or the wiring length and the distance between the resistor unit 14 and the light-emitting element 3.

[0093] This example illustrates a relationship where the variation in light intensity caused by the distance or wiring length between the power supply unit 13 and the light-emitting element 3 cancels out the variation in light intensity caused by the distance between the resistor unit 14 and the light-emitting element 3. Therefore, regarding this example, [the relationship between the two is described]. Figure 1 Compared to the configuration shown in (b) (where the power supply unit 13 and the resistor unit 14 are arranged on the side of the end of the same side in the main scanning direction of the light source unit 2), it is superior in that it can suppress the maximum variation in light amount less.

[0094] Furthermore, in the configuration where multiple light-emitting elements 3 in the light source unit 2 are arranged in multiple groups, the correction unit 6 only needs to make the correctable width Th of each light-emitting element 3 in the group different in parallel.

[0095] In this example, in the configuration where the light source unit 2 is composed of multiple systems that use a common driving signal for each group unit, the correction unit 6 preferably performs, for example, parallel correction processing of the correctable width Th for the light-emitting element 3 belonging to the group unit of any one system and correction processing of the correctable width Th for the light-emitting element 3 belonging to the group unit of other systems.

[0096] The present invention will now be described in more detail with reference to the embodiments shown in the accompanying drawings.

[0097] ◎Implementation Method 1

[0098] -Overall structure of the image forming system-

[0099] Figure 2 This indicates the overall structure of the image forming system involved in Implementation 1.

[0100] In this figure, the image forming system 20 is typically referred to as a cascaded image forming system. This image forming system 20 includes an image forming processing unit 21, an image output control unit 40, and an image processing unit 50. Here, the image forming processing unit 21 is a functional unit that performs image forming corresponding to image data of each color. Furthermore, the image output control unit 40 is a functional unit that controls the image forming processing unit 21. Moreover, the image processing unit 50 is connected, for example, to a personal computer (PC) 51 and an image reading device 52, and performs predetermined image processing on the image data received from these devices.

[0101] The image forming processing unit 21 includes image forming units 22 arranged side-by-side at constant intervals. Each image forming unit 22 comprises four image generating engines 23 (23a-23d), which are examples of tonal image forming units. These tonal image forming units are functional units that form tonal images of four colors (yellow (Y), magenta (M), cyan (C), and black (K) in this example). Furthermore, each image generating engine 23 (23a-23d) includes an image holding unit that forms an electrostatic latent image to hold the tonal image. In this example, a roller-shaped photoreceptor 24 is used as an example of an image holding unit. A charge charger 25, an exposure unit 26 serving as a light writing device, and a developer 27 are arranged around the photoreceptor 24. Here, the charge charger 25 is a component that uniformly charges the surface of the photoreceptor 24 with a predetermined potential. The exposure unit 26 is a component that exposes the photoreceptor 24 charged by the charge charger 25 and forms an electrostatic latent image. The developer 27 is a component that develops the electrostatic latent image formed by the exposure unit 26.

[0102] In addition, the image generation engine 23 (23a-23d) generates tonal images of yellow (Y), magenta (M), cyan (C), and black (K), respectively.

[0103] Furthermore, the image forming processing unit 21 transfers the toner images of each color formed on the photoreceptors 24 of each image generating engine 23 (23a-23d) multiple times onto recording paper 29, which is an example of a recording medium, and then fixes them. In this example, the image forming processing unit 21 includes a paper conveyor belt 30, a transfer unit 31, and a fixer 32. Here, the paper conveyor belt 30 is a component that transports the recording paper 29. The transfer unit 31 is a component that transfers the toner images of the photoreceptors 24 onto the recording paper 29; in this example, a transfer roller is used. The fixer 32 is a component that fixes the toner images transferred onto the recording paper 29.

[0104] In this image forming system 20, the image forming processing unit 21 performs image forming operations based on various control signals supplied from the image output control unit 40. Furthermore, if image data is received from a personal computer (PC) 51 or an image reading device 52, it is processed as follows: The image data is processed by the image processing unit 50 under the control of the image output control unit 40 and then supplied to the image generation engine 23.

[0105] Furthermore, for example, in the black (K) image generation engine 23d, the photoreceptor 24 is energized to a preset potential by the charge carrier 25 while rotating in the direction of the arrow. Then, the photoreceptor 24 is exposed by the exposure unit 26, which emits light according to image data supplied from the image processing unit 50. Thus, an electrostatic latent image associated with the black (K) image is formed on the photoreceptor 24. Furthermore, the electrostatic latent image formed on the photoreceptor 24 is developed by the developer 27, forming a black (K) toner image on the photoreceptor 24. Similarly, in each of the image generation engines 23 (23a-23c), toner images of yellow (Y), magenta (M), and cyan (C) are formed respectively.

[0106] The toner images of each color generated by each image generation engine 23 (23a-23d) on the photoreceptor 24 are transferred multiple times onto the recording paper 29. In this example, the recording paper 29 is supplied as the paper conveyor 30 moves in the direction of the arrow. Furthermore, the toner images of each color are electrostatically transferred onto the recording paper 29 sequentially by a transfer electric field applied to the transferr (transfer roller) 31. Therefore, a composite toner image of each color overlaid is formed on the recording paper 29.

[0107] Subsequently, the recording paper 29, with the synthetic toner image electrostatically transferred, is conveyed to the fuser 32. Furthermore, the synthetic toner image on the recording paper 29 undergoes a heat- and pressure-based fixing process in the fuser 32 to be fixed onto the recording paper 29, and is then ejected from the image forming system 20.

[0108] Additionally, residues (residual colorant, paper dust, etc.) on the photoreceptor 24 or the paper conveyor belt 30 are properly cleaned by a cleaner not shown.

[0109] -Example of an exposure unit structure-

[0110] Figure 3 This illustrates a structural example of the exposure unit 26 used in this embodiment.

[0111] In this figure, the explorator 26 consists of an LED printhead (hereinafter referred to as "LPH") 60 that uses LEDs as light-emitting elements.

[0112] The LPH60 includes a bracket 61 as a holding component, a light-emitting element chip array 63 constituting the light-emitting part, and an imaging lens 64 as an example of an imaging unit.

[0113] In this example, the light-emitting element chip array 63 is, for example, composed of a self-scanning LED array. Furthermore, the light-emitting element chip array 63 is driven by a drive signal from the drive circuit (signal generation circuit) 100, which serves as a drive signal generation unit. In this example, the light-emitting element chip array 63 and the signal generation circuit 100 (see reference...) Figure 4 (a) and the like are mounted on the circuit board 62. Furthermore, the imaging lens 64 is an optical component that images light from the light-emitting element chip array 63 onto the surface of the photoreceptor 24, and is, for example, composed of a rod-shaped lens array.

[0114] In this example, the bracket 61 is formed of blocks or metal plates such as aluminum or SUS, and holds the circuit board 62 and the imaging lens 64. Furthermore, the bracket 61 houses the LEDs (see reference 65) of the light-emitting element 65, which are part of the light-emitting element chip array 63. Figure 4 The light-emitting point of (b) coincides with the focal plane of the imaging lens 64. Furthermore, each of the rod-shaped lenses serving as the imaging lens 64 is arranged along the axial direction of the photoreceptor 24 (corresponding to the main scanning direction).

[0115] The LPH60 thus configured is adjustable by adjusting screws (not shown) so that it can move along the optical axis of the imaging lens 64, and the imaging position (focal plane) of the imaging lens 64 is located on the surface of the photoreceptor 24.

[0116] -Example of a circuit board structure-

[0117] Figure 4 (a) is a top view of circuit board 62.

[0118] In this figure, the light-emitting element chip array 63 is an array structure in which multiple light-emitting element chips U (specifically, U1 to Un) are arranged on a circuit board 62. In this example, each light-emitting element chip U is arranged in a staggered pattern in two opposing columns along the axial direction of the photoreceptor 24 (corresponding to the main scanning direction). Furthermore, each light-emitting element chip U (U1 to Un) has a chip substrate 66, on which light-emitting elements 65 are arranged along the main scanning direction.

[0119] In this example, the light-emitting element chips U (U1~Un) are arranged in an alternating pattern for the following reason. Suppose that if multiple light-emitting element chips U are arranged in one direction, it is possible that the spacing between the light-emitting elements 65 at the ends of each chip U cannot be kept constant. To avoid this, as... Figure 4As shown in (b), the light-emitting element chips U are arranged in an alternating manner, and the ends of each light-emitting element chip U are partially overlapped. In this way, a structure is obtained in which the spacing of the light-emitting elements 65 between the ends of each light-emitting element chip U (Ui-1, Ui, Ui+1) is kept constant.

[0120] And, as Figure 4 As shown in (a), the circuit board 62 is provided with a signal generation circuit 100, a power supply voltage control unit 101 that outputs power supply voltage Vsub, an EEPROM 102 that stores light quantity correction value data in the light-emitting element chip array 63, and a wiring harness 103 that transmits and receives signals between the image output control unit 40 or the image processing unit 50 of the image forming system 20.

[0121] -Various driving signals to the light-emitting element chip array-

[0122] Figure 5 This refers to various drive signals from the input to the signal generation circuit 100 of the light-emitting element chip array 63.

[0123] In this figure, various control signals are input to the signal generation circuit 100 from the image output control unit 40 or the image processing unit 50, etc. Here, the control signals include the horizontal synchronization signal Lsync, the image data DTg, and other data DT1 to DT3, the clock signal CLK, and the reset signal RST. Furthermore, the signal generation circuit 100, based on the various control signals input from the outside, performs tasks such as rearranging the image data DTg or correcting the output value, and outputs lighting signals ΦI (ΦI1 to ΦIn) to each light-emitting element 65 of each light-emitting element chip U (U1 to Un).

[0124] Furthermore, the signal generation circuit 100 outputs a start transmission signal (corresponding to the horizontal synchronization signal Lsync) ΦS, a first transmission signal Φ1, and a second transmission signal Φ2 to each light-emitting element chip U (U1~Un) based on various control signals input from the outside.

[0125] Furthermore, the circuit board 62 is provided with a power supply line 121 for the power supply voltage Vsub connected to the power supply terminals of each light-emitting element chip U (U1 to Un), and a grounding power supply line 122 connected to the GND terminal. The circuit board 62 also includes start transmission signal lines 123, 124, and 125 for the start transmission signal ΦS, the first transmission signal Φ1, and the second transmission signal Φ2 of the signal generation circuit 100. Additionally, the circuit board 62 is provided with n lighting signal lines 126 (126-1 to 126-n) that output lighting signals ΦI (ΦI1 to ΦIn) from each light-emitting element chip U (U1 to Un) of the signal generation circuit 100. Furthermore, the circuit board 62 is provided with a current-limiting resistor RID to prevent excessive current from flowing through the n-system lighting signal lines 126.

[0126] -Structure example of a signal generation circuit-

[0127] Figure 6 This is a block diagram showing the structure of the signal generation circuit 100.

[0128] The signal generation circuit 100 consists of an image data unfolding unit 110, a density unevenness correction data unit 112, a timing signal generation unit 114, a reference clock generation unit 116, and a lighting time control / drive unit 118 (specifically 118-1 to 118-n) provided corresponding to each light-emitting element chip U (U1 to Un).

[0129] <Image Data Unfolding Section>

[0130] Image data is serially transmitted from the image processing unit (IPS) 50 to the image data unpacking unit 110. The image data unpacking unit 110 divides the transmitted image data into image data of points 1 to j (j: for example 128), points j+1 to 2×j, ..., points (n-1)×j+1 to n×j, and each light-emitting element chip U (U1 to Un). The image data unpacking unit 110 is connected to the illumination time control / drive unit 118 and outputs the divided image data to the corresponding illumination time control / drive units 118-1 to 118-n.

[0131] <Concentration Non-uniformity Correction Data Department>

[0132] The density unevenness correction data unit 112 stores density unevenness correction data for correcting image density unevenness during image formation caused by deviations in the light amount of each LED within each light-emitting element chip U. Furthermore, the density unevenness correction data is output to the illumination time control / drive unit 118 synchronously with the data readout signal from the density unevenness correction data unit 112. This density unevenness correction data is data set in each LED based on deviations in the light amount of each LED, and in this embodiment, it is, for example, formed as 8-bit data.

[0133] The EEPROM 102 stores the light intensity correction data DT1 for each LED. Furthermore, when the machine is powered on, the light intensity correction data DT1 for each LED is downloaded from the EEPROM 102 to the concentration unevenness correction data unit 112. Thus, the light intensity correction data DT1 is stored in the concentration unevenness correction data unit 112 as concentration unevenness correction data. In this example, the light intensity correction data DT1 is processed as concentration unevenness correction data, but concentration unevenness correction data can also be generated based on the light intensity correction data DT1 and other data.

[0134] Here, the light quantity correction data DT1 of each LED stored in EEPROM 102 is obtained as follows. The light quantity correction data DT1 of each LED is generated by measuring the light quantity of each LED using a light profile measuring device or the like.

[0135] First, the LPH60 is set in the light profile measurement device, and each LED is lit to measure the light distribution data of each LED. Then, based on the measured light distribution data, the integral value of each coordinate position in the LED arrangement direction (main scanning direction) along the direction orthogonal to the main scanning direction (sub-scanning direction) is calculated to obtain the light distribution (light profile) in the main scanning direction (reference). Figure 10 (a)

[0136] Next, the light intensity between valleys in the light profile is integrated, and the light intensity (exposure energy) density of the valley-to-valley region is calculated by dividing the integrated value by the distance between the valleys. The exposure energy density of each region thus calculated is set as the correction characteristic value for each LED. Then, to make the correction characteristic value consistent with a specified target value, the light intensity is increased or decreased according to the error from the target value, so that the correction characteristic value in all regions becomes flat. Figure 10 (b)). Then, the light intensity correction value of each region after such flattening is set as the light intensity correction value for each LED.

[0137] Additionally, in this example, when correcting for uneven light concentration, such as Figure 10As shown in (c), the emission time width t is extended (tL) or reduced (tS) by a predetermined light intensity Pc, thereby performing light quantity correction.

[0138] <Reference Clock Generation Unit>

[0139] The reference clock generation unit 116 generates the reference clock required in the signal generation circuit 100 and connects to the image output control unit 40, the timing signal generation unit 114, and the lighting time control / drive unit 118 (118-1 to 118-n).

[0140] Moreover, in this example, such as Figure 2 As shown, at a predetermined time interval, a tonal image, serving as a test marker (density example), is formed on the photoreceptor 24 of each image generation engine 23, and the density detector 28 detects the density of this tonal image. Figure 6 As shown, the toner concentration data detected by the concentration detector 28 is output to the image output control unit 40. The image output control unit 40 calculates the light amount in the LPH60 based on the input toner concentration data and generates light amount adjustment data DT3. Then, the generated light amount adjustment data DT3 is output to the reference clock generation unit 116.

[0141] In this example, the tonal concentration formed as a test indicator may vary. For example, variations in the sensitivity of the photoreceptor 24, variations in the latent image potential (dark area potential or bright area potential), and consequently variations in the developing dose within the developer 27 are the main causes. Therefore, in this example, the light intensity adjustment data DT3 is used to adjust the overall light intensity in the LPH60 (the overall light intensity of the LEDs within the LPH60) to maintain the aforementioned variations at a constant level. Therefore, the light intensity adjustment data DT3 is output as an indication value that indicates the pulse width of the lighting signal ΦI of each light-emitting element chip U driving the LPH60.

[0142] <Timing Signal Generation Unit>

[0143] The timing signal generation unit 114 is connected to the image output control unit 40 and the reference clock generation unit 116. The timing signal generation unit 114 uses the reference clock signal from the reference clock generation unit 116 as a reference and synchronizes with the horizontal synchronization signal Lsync from the image output control unit 40, thereby generating transmission signals CK1R, CK1C and transmission signals CK2R, CK2C. Here, Lsync is a timing signal that provides timing for the start of a main scan period. The transmission signals CK1R, CK1C and CK2R, CK2C are converted into first transmission signal Φ1 and second transmission signal Φ2 via the level conversion circuit 104 and sent to the light-emitting element chip array 63.

[0144] Furthermore, the timing signal generation unit 114 is connected to the density unevenness correction data unit 112 and the image data unrolling unit 110. The timing signal generation unit 114 uses a reference clock signal from the reference clock generation unit 116 as a reference and synchronizes with the horizontal synchronization signal Lsync from the image output control unit 40. This allows it to output a data readout signal to the image data unrolling unit 110 for reading image data DTg corresponding to each pixel from the image data unrolling unit 110, and to the density unevenness correction data unit 112 for reading density unevenness correction data corresponding to each image (each LED) from the density unevenness correction data unit 112. The timing signal generation unit 114 is also connected to the lighting time control / drive unit 118 (118-1 to 118-n). The timing signal generation unit 114 uses the reference clock signal from the reference clock generation unit 116 as a reference and outputs a trigger signal TRG to start lighting the light-emitting element chip array 63.

[0145] Moreover, such as Figure 7 As shown in (a), the timing signal generation unit 114 includes a transmission period generation unit 201 and a transmission signal generation unit 202. The transmission period generation unit 201 generates a transmission period signal based on the horizontal synchronization signal Lsync and the transmission period setting data DT2, and sends it to the transmission signal generation unit 202. The transmission period signal here is a signal that determines the timing of the rising or falling edge of the transmission signals CK1C and CK2C. The transmission signal generation unit 202 generates transmission signals CK1R, CK1C, CK2R, and CK2C based on the transmission period signal. Furthermore, the transmission signal generation unit 202 also generates a trigger signal TRG.

[0146] Here, we provide supplementary explanations regarding the transmission period setting data DT2.

[0147] The transmission cycle setting data DT2 is the data that sets the transmission cycle TS of the driving signal of the light-emitting element 65 of each light-emitting element chip U (U1~Un).

[0148] Typically, the transmission period setting data DT2 is set based on the processing speed of the image forming system 20, using the timing of transmitting the illumination signal ΦI as a uniform reference transmission period TSc.

[0149] However, in this embodiment, it is clarified that the light-emitting element chip U (U1 to Un) with multiple light-emitting elements 65 arranged thereon still has the characteristic that the light intensity varies according to the arrangement position of the light-emitting elements 65, even after the concentration unevenness correction process is performed.

[0150] Therefore, in this example, a method is proposed as follows: to correct for variations in light intensity associated with the arrangement of the aforementioned light-emitting elements 65, the transmission period of each light-emitting element 65 is made different. Furthermore, in this example, the transmission period setting data DT2 is set in a manner used to set different transmission periods for each light-emitting element 65. Details regarding this point will be described later.

[0151] <Light-up Time Control / Driver Unit>

[0152] The illumination time control / drive unit 118 (118-1 to 118-n) sets the illumination time of each pixel (each LED) based on the image data DTg from the image data unfolding unit 110. Then, the illumination time control / drive unit 118 (118-1 to 118-n) corrects the illumination time of each pixel (each LED) based on the density unevenness correction data from the density unevenness correction data unit 112, and generates illumination signals ΦI (ΦI1 to ΦIn) for illuminating each pixel of each light-emitting element chip U.

[0153] -Power Supply Voltage Control Section-

[0154] In this example, the power supply voltage control unit 101 controls the power supply voltage supplied to the LPH60. Specifically, as follows: Figure 6 As shown, the power supply voltage control unit 101 is configured to include a three-terminal voltage regulator 119.

[0155] Here, the three-terminal regulator 119 generates the power supply voltage Vsub for the light-emitting element chip array 63.

[0156] Furthermore, in this example, it is acceptable to pre-select the power supply voltage Vsub as the power supply voltage required in the assumed light-emitting element chip array 63. However, when controlling the light intensity of each light-emitting element 65, in addition to setting the light emission time width to be variable, the light intensity is also set to be variable. Of course, the power supply voltage Vsub can be set to be variable in the power supply voltage control unit 101.

[0157] -Example of the basic structure of a light-emitting element chip-

[0158] In this example, such as Figure 8As shown in (a), the light-emitting element chip U has a light-emitting element array 67 extending along the main scanning direction on the chip substrate 66. This light-emitting element array 67 is an array structure in which multiple light-emitting elements 65 are arranged along the main scanning direction. In this example, a power supply pad 68, serving as a power supply unit, is provided on one side of the light-emitting element array 67 on the chip substrate 66 along the main scanning direction. This power supply unit supplies various drive signals from the signal generation circuit 100. Furthermore, in this example, a current-limiting resistor 69, serving as a resistor unit, is provided on one side of the light-emitting element array 67 on the chip substrate 66 along the main scanning direction and on the same side as the power supply pad 68. This current-limiting resistor 69 is used to limit excessive current flowing through each light-emitting element 65.

[0159] Furthermore, in this example, a light-on / off circuit 70 is provided on the chip substrate 66, which takes various drive signals input to the power supply pad 68 to sequentially light up / off each light-emitting element 65.

[0160] -Example of circuit structure for a light-emitting element chip-

[0161] Figure 9 This illustrates an example of the circuit structure of the light-emitting element chip involved in Embodiment 1.

[0162] <Power supply pads>

[0163] In this example, such as Figure 9 As shown, the power supply pad 68 has terminals corresponding to the Φ1 terminal, Φ2 terminal, ΦW1 terminal, ΦW2 terminal, Vga terminal and ΦI terminal of the signal generation circuit 100.

[0164] <Array of Light-Emitting Elements>

[0165] exist Figure 9 In this configuration, the light-emitting element array 67 is an array structure in which light-emitting elements 65, composed of light-emitting thyristors L, are arranged along the main scanning direction. That is, the light-emitting element array 67 comprises a column of light-emitting thyristors L (L1, L2, L3…) arranged sequentially as light-emitting elements 65. In this example, the light-emitting thyristors L differ from LEDs; for example, both the light-emitting element array 67 and the lighting / extinguishing circuit 70 can be formed using thyristors, which is simple and preferable.

[0166] In this example, the light-emitting thyristor L is a semiconductor device having a first gate, a second gate, an anode, and a cathode. In this example, the cathodes of the odd-numbered light-emitting thyristors L1, L3, L5… are connected to the lighting signal line 90-1. Furthermore, the lighting signal line 90-1 is connected to the ΦI terminal via the current-limiting resistor 69. Additionally, in… Figure 9 In the diagram, the current limiting resistor 69 is marked as RI1.

[0167] On the other hand, the cathodes of the even-numbered light-emitting thyristors L2, L4, L6... are connected to the lighting signal line 90-2. In this example, lighting signal line 90-2 is connected in parallel with lighting signal line 90-1. Furthermore, lighting signal line 90-2 is connected to terminal ΦI via current limiting resistor 69. And, the lighting signal ΦI is transmitted to terminal ΦI. Additionally, in... Figure 9 In the diagram, the current limiting resistor 69 is marked as RI2.

[0168] <Light-on / Light-off Circuit>

[0169] In this example, such as Figure 9 As shown, the light-on / light-off circuit 70 includes a transmission thyristor array 98 and a write thyristor array 99.

[0170] Here, the transmission thyristor array 98 is composed of transmission thyristors T (T1, T2, T3...) arranged in a row, similar to the light-emitting thyristor array 67 which is a light-emitting element array.

[0171] In this example, the transmission thyristor array 98 pairs the transmission thyristors T1, T2, T3... in numerical order. Furthermore, each pair of transmission thyristors 98 is connected by a pnp bipolar transistor, i.e., coupling transistors Qt1, Qt2, Qt3...

[0172] On the other hand, the write thyristor array 99 is composed of write thyristors S (S1, S2, S3...) arranged in a column, similar to the light-emitting thyristor array 67. Furthermore, the write thyristor array 99 and the write thyristors S1, S2, S3... are respectively equipped with write transistors Qs1, Qs2, Qs3...

[0173] Furthermore, a first transmission signal line 91 for transmitting the first transmission signal Φ1 and a second transmission signal line 92 for transmitting the second transmission signal Φ2 are formed on the surface of the chip substrate 66. Current limiting resistors R1 and R2, respectively, are connected in series to the first transmission signal line 91 and the second transmission signal line 92 to prevent excessive current from flowing through.

[0174] Furthermore, a first lighting start signal line 93 for transmitting a first lighting start signal ΦW1 and a second lighting start signal line 94 for transmitting a second lighting start signal ΦW2 are formed on the surface of the chip substrate 66. Current limiting resistors RW1 and RW2, respectively, are connected in series to the first lighting start signal line 93 and the second lighting start signal line 94 to prevent excessive current flow.

[0175] Here, the transmission thyristor T and the write thyristor S, like the light-emitting thyristor L, are semiconductor devices having a first gate, a second gate, an anode, and a cathode. Furthermore, the coupling transistor Qt and the write transistor Qs are semiconductor devices having a collector, a base, and an emitter, but the odd-numbered coupling transistor Qt has two collectors (multiple collectors).

[0176] Furthermore, in Figure 9 In the transmission thyristor T, the gates are labeled as Gtf (first gate) and Gts (second gate), in the write thyristor S, the gates are labeled as Gsf (first gate) and Gss (second gate), and in the light-emitting thyristor L, the gate is labeled as Glf (first gate). Similarly, in the odd-numbered multi-collector coupled transistor Qt, the collectors are labeled as Cf (first collector) and Cs (second collector), and in the even-numbered coupled transistor Qt, the collector is labeled as C. Furthermore, in the write transistor Qs, the collector is labeled as C.

[0177] Next, the electrical connections of the transmission thyristor array 98 and the components written into the thyristor array 99 will be explained (see reference). Figure 9 ).

[0178] <Transmission Thyristor Array>

[0179] The anodes of the transmission thyristor T, the write thyristor S, and the light-emitting thyristor L are connected to the chip substrate 66. Furthermore, the emitters of the coupling transistor Qt and the write transistor Qs are also connected to the chip substrate 66.

[0180] Furthermore, these anodes and emitters are connected to a power line (not shown) via a Vsub terminal, i.e., a back electrode, disposed on the back side of the chip substrate 66. This power line is supplied with a power supply voltage Vsub from the power supply voltage control unit 101.

[0181] Along the transmission thyristor array 98, the cathodes of the odd-numbered transmission thyristors T1, T3, T5... are connected to the first transmission signal line 91. Furthermore, the first transmission signal line 91 is connected to the Φ1 terminal via a current-limiting resistor R1, and the first transmission signal Φ1 is sent to the first transmission signal line 91.

[0182] On the other hand, along the transmission thyristor array 98, the cathodes of the even-numbered transmission thyristors T2, T4, and T6 are connected to the second transmission signal line 92. Furthermore, the second transmission signal line 92 is connected to the Φ2 terminal via the current limiting resistor R2, and the second transmission signal Φ2 is sent to the second transmission signal line 92.

[0183] Furthermore, along the transmission thyristor array 98, the first gate Gtf of the odd-numbered transmission thyristors T is connected to the power supply line 95 via resistor Rt. The second gate Gts is connected to the base of the odd-numbered coupling transistor Qt. Additionally, the power supply line 95 is connected to the Vga terminal.

[0184] The first collector Cf of the odd-numbered coupling transistor Qt is connected to the power supply line 95 via resistor Rs. Furthermore, the first collector Cf is connected to the first gate Gsf of both the odd-numbered write thyristor S (with the same number) and the even-numbered write thyristor S (with a number one greater than the previous one). Additionally, the second collector Cs is connected to the first gate Gtf of the even-numbered (later segment) transmission thyristor T (with a number one greater than the previous one).

[0185] The first gate Gtf of the even-numbered transmission thyristor T is connected to the ground power supply line 95 via resistor Rt. The second gate Gts is connected to the base of the even-numbered coupling transistor Qt. The collector C of the even-numbered coupling transistor Qt is connected to the first gate Gtf of the odd-numbered transmission thyristor T (next segment), which is one number higher.

[0186] <Write to thyristor array>

[0187] Furthermore, along the write thyristor array 99, the cathodes of the odd-numbered write thyristors S are connected to the first illumination start signal line 93. Additionally, the first illumination start signal line 93 is connected to the ΦW1 terminal via the current limiting resistor RW1, and the first illumination start signal ΦW1 is sent to the first illumination start signal line 93.

[0188] On the other hand, along the write thyristor array 99, the cathodes of the even-numbered write thyristors S are connected to the second illumination start signal line 94. Furthermore, the second illumination start signal line 94 is connected to the ΦW2 terminal via the current limiting resistor RW2, and the second illumination start signal ΦW2 is sent to the second illumination start signal line 94.

[0189] Furthermore, the second gate Gss of the write thyristor S is connected to the base of the corresponding write transistor Qs. The collector C of the write transistor Qs is connected to the power supply line 95 via a resistor RL, and is also connected to the first gate Glf of the light-emitting thyristor L with the same number.

[0190] As described above, in the light-emitting element chip U according to this embodiment, write thyristors S with the same number and a number one greater than the odd-numbered transmission thyristor T are connected to each write thyristor S, and light-emitting thyristors L are connected to each write thyristor S. That is, the two light-emitting thyristors L are controlled by the odd-numbered transmission thyristor T.

[0191] In addition, the odd-numbered coupling transistor Qt is configured with multiple collectors, but it can also have only one collector, and the first gate Gsf of the writing thyristor S and the first gate Gtf of the transmission thyristor T are connected together.

[0192] -How the LED Chip Works-

[0193] In this example, each light-emitting element 65 of the light-emitting element array 67 is controlled to light up and light down via the light-on / light-off circuit 70. Therefore, in this example, each light-emitting element 65 of the light-emitting element array 67 repeats the light-on and light-off actions in parallel, sequentially, according to the odd-numbered groups and even-numbered groups.

[0194] Thus, in the configuration where the lighting and extinguishing actions of each light-emitting element 65 of the light-emitting element array 67 are performed in parallel in groups, the writing action based on the light-emitting element array 67 can be set to high speed compared to the configuration without grouping.

[0195] In this example, the light-emitting elements 65 of the light-emitting element array 67 are grouped and operate in parallel, repeatedly turning on and off, but this is not a limitation. Of course, it can also be configured to operate in a way that involves sequentially turning on and off without grouping.

[0196] Furthermore, in this example, the lighting / extinguishing circuit 70 uses a configuration with a transmission thyristor array 98 and a write thyristor array 99, but it is not limited to this. For example, it is acceptable to select any appropriate configuration as long as it can enable the lighting and extinguishing of each light-emitting element 65.

[0197] -Behavior of light-emitting element chips-

[0198] like Figure 8 (a) and Figure 9 As shown, in this embodiment, the light-emitting element chip U controls the lighting and extinguishing of each light-emitting element 65 sequentially from the power supply pad 68 via the lighting / extinguishing circuit 70.

[0199] Therefore, as Figure 8 As shown in (b), the power supply direction to the light-emitting element chip U is from the first light-emitting element 65 (first point) on the side of the power supply pad 68 toward the last light-emitting element 65 (final point).

[0200] Furthermore, in this example, the light-emitting element chip U has a current limiting resistor 69 (RI1, RI2) on one side of the power supply pad 68 in the main scanning direction of the light-emitting element array 67.

[0201] At this point, in this example, with the odd-numbered light-emitting elements 65 lit, the lighting signal line 90-1 and the first lighting start signal line 93 are energized. Therefore, current flows through the current-limiting resistor 69 (RI1) connected to the lighting signal line 90-1, resulting in heat generation.

[0202] Furthermore, when the even-numbered light-emitting elements 65 are lit, the lighting signal line 90-2 and the second lighting start signal line 94 are energized. Therefore, current flows through the current-limiting resistor 69 (RI2) connected to the lighting signal line 90-2, resulting in heat generation.

[0203] -Impact on the optical properties of light-emitting element chips-

[0204] In this example, such as Figure 10 As shown in (b), the light distribution of the light-emitting element chip U, which underwent light quantity correction processing for uneven concentration, was measured, and the results were obtained. Figure 8 The result shown in (c) is as follows.

[0205] According to the figure, it is confirmed that the amount of light emitted by the light-emitting element chip U varies depending on the arrangement of the light-emitting elements 65.

[0206] Specifically, it was observed that in the light-emitting element array 67 of the light-emitting element chip U, the amount of light gradually decreases from the first light-emitting element 65 (the first point) to the last light-emitting element 65 (the final point).

[0207] The following factors can be considered as factors affecting the variation in this amount of light.

[0208] (1) Due to the influence of power supply direction

[0209] In this example, in the light-emitting element array 67, the amount of light from each light-emitting element 65 gradually decreases towards the power supply direction.

[0210] It is speculated that this depends on the distance or wiring length between the power supply pad 68 and the light-emitting element 65. That is, it is speculated that the longer the distance or wiring length between the power supply pad 68 and the light-emitting element 65, the greater the loss of power supply current, and correspondingly, the greater the reduction in light intensity (see reference). Figure 8 (c) dashed line).

[0211] (2) Due to the influence of the current limiting resistor

[0212] In this example, the current-limiting resistors 69 (RI1, RI2) act as heat sources on the light-emitting element array 67. Specifically, in this example, the first light-emitting element 65 (point 1) in the array 67 is closest to the current-limiting resistors 69 (RI1, RI2) and is therefore most susceptible to the effects of the heat source. It is generally known that if the temperature of the light-emitting element 65 rises due to the heat source, its luminous efficiency decreases. Therefore, it is presumed that the decrease in light intensity in this example depends on the distance between the current-limiting resistors 69 (RI1, RI2) and the light-emitting element 65. That is, it is presumed that the shorter the distance between the current-limiting resistors 69 (RI1, RI2) and the light-emitting element 65, the more severe the temperature rise caused by the heat source, and correspondingly, the lower the luminous efficiency (see reference). Figure 8 (c) is a single solid line.

[0213] -Correction of light intensity variation in light-emitting element chip-

[0214] In order to correct such Figure 8 The light quantity variation shown in (c) is preferably such that the light quantity correction amount of the last light-emitting element 65 (final point) is allocated sufficiently more than the light quantity correction amount of the first light-emitting element 65 (first point).

[0215] That is, such as Figure 8 As shown in (d), in the light-emitting element 65 on the side predicted to have a large amount of light correction, it is only necessary to extend the correctable width Th of the light emission time width of the lighting signal ΦI. On the other hand, in the light-emitting element 65 on the side predicted to have a small amount of light correction, it is only necessary to reduce the correctable width Th of the light emission time width of the lighting signal ΦI.

[0216] -Regarding the transmission cycle of the driving signals for each light-emitting element-

[0217] Typically, the transmission period TS of the driving signal for each light-emitting element 65 is uniquely determined by the processing speed of the image forming system 20.

[0218] Currently, such as Figure 11 As shown in (a), it is assumed that the transmission period TS of the driving signal for each light-emitting element 65 is, for example, TSa.

[0219] At this time, the first transmission signal Φ1 or the second transmission signal Φ2 is given to the light-emitting element chip U, for example, according to each transmission cycle TSa (duty cycle 50%).

[0220] Furthermore, the lighting signal ΦI of the light-emitting element 65 is made using a lighting start signal ΦW (specifically, a first lighting start signal ΦW1 and a second lighting start signal ΦW2) and a lighting end signal ΦR.

[0221] In this case, the driving range of the lighting start signal ΦW and the lighting end signal ΦR is constrained by the ASIC function, as follows.

[0222] In this example, the start-up signal ΦW uses the first half of the transmission period TSa of either the first transmission signal Φ1 or the second transmission signal Φ2 as its driveable range. Conversely, the end-up signal ΦR uses the second half of the transmission period TSa as its driveable range. In this example, the driveable ranges of ΦW and ΦR are the same, and the driveable range of ΦW corresponds to the aforementioned correctable width Th.

[0223] Next, we will explain how to increase the writing speed of the light-emitting element chip U (equivalent to the processing speed of the image forming system).

[0224] In this case, such as Figure 11 As shown in (b), it is sufficient to select the transmission period TS of the driving signal for each light-emitting element 65 as TSb, which is shorter than TSa.

[0225] At this time, as the transmission period TSb shortens, the driveable range of the lighting start signal ΦW and the driveable range of the lighting end signal ΦR narrows. As a result, the correctable width Th decreases.

[0226] In particular, when increasing the writing speed of the light-emitting element chip U, it is not preferable to uniformly set the calibrable width Th for each light-emitting element 65.

[0227] Suppose that when the correctable width Th is uniformly set for each light-emitting element 65, the correctable width Th becomes smaller. In this case, there is a concern that the light-emitting element 65, which is predicted to have a large amount of light correction, may not have sufficient light correction.

[0228] Considering this situation, the following correction method is adopted in this example.

[0229] -Example of a correction method for light intensity variations in a light-emitting element chip-

[0230] Currently, such as Figure 8 As shown in (c), the light-emitting element chip U has the characteristic that the amount of light gradually decreases from the first light-emitting element 65 (first point) in the light-emitting element array 67 toward the last light-emitting element 65 (final point).

[0231] Therefore, in this example, in order to correct Figure 8 The light intensity variation shown in (c) is as follows: Figure 12As shown in (a), a correction amount is selected for expanding the correctable width Th for the light-emitting element 65 (the right half of the region bounded by the center of the light-emitting element array 67) that is predicted to have a higher light-intensity correction amount. Conversely, a correction amount is selected for reducing the correctable width Th for the light-emitting element 65 (the left half of the region bounded by the center of the light-emitting element array 67) that is predicted to have a lower light-intensity correction amount. The correction amount referred to here is the average correction amount per U unit of the light-emitting element chip.

[0232] Currently, the number j of light-emitting elements 65 in the light-emitting element array 67 is set to, for example, 512, and the correctable width Th during the reference transmission period is assumed to be T.

[0233] Since the correction amount of the first light-emitting element is the smallest, therefore, as Figure 12 As shown in (b), the correctable width Th is reduced to Ta.

[0234] Furthermore, the Nth light-emitting element, located in the left half of the region, has a smaller correction amount compared to the central position. Therefore, as... Figure 12 As shown in (b), the correctable width Th is reduced to Tb (a>b).

[0235] Furthermore, the 512-N light-emitting elements located in the right half of the region, compared to the central position, require more calibration. Therefore, as... Figure 12 As shown in (b), the correctable width Th is extended to T+c.

[0236] Furthermore, the 512th light-emitting element requires the most calibration, therefore, as Figure 12 As shown in (b), the correctable width Th is extended to T+d (d>c).

[0237] Furthermore, when considering the total correctable width Th of each light-emitting element, it is sufficient that it is equal to the correctable width T×j (j=512) of the reference transmission period.

[0238] Specifically, when correcting the correctable width Th for each light-emitting element 65, there is a first correctable width group that is greater than the reference value (reference transmission period TSc / 2) and a second correctable width group that is less than the reference value. The correctable width Th is corrected in such a way that the sum of the differences between the first correctable width group and the reference value and the sum of the differences between the second correctable width group and the reference value are of the same degree.

[0239] In this example, to extend the adjustable width Th of the illumination time width of the lighting signal ΦI, a method is used, for example, to extend the transmission period TS of the driving signal for each light-emitting element 65. On the other hand, when reducing the adjustable width Th, a method is used, for example, to reduce the transmission period TS of the driving signal for each light-emitting element 65.

[0240] In this example, according to Figure 12 The correction characteristics shown in (a) allow for the selection of appropriate transmission period setting data DT2 (reference) for each light-emitting element 65 of the light-emitting element array 67. Figure 7 (b)). These transmission cycle setting data DT2 are stored in EEPROM 102 in a readable manner (see reference). Figure 6 After the transmission cycle setting data DT2 is read from the EEPROM 102 to the image output control unit 40, it is sent to the timing signal generation unit 114 of the signal generation circuit 100. Then, the timing signal generation unit 114 outputs transmission signals CK1R, CK1C, CK2R, and CK2C that take into account the transmission cycle setting data DT2, and generates the first transmission signal Φ1 and the second transmission signal Φ2.

[0241] -The relationship between the transmission signal and the lighting signal of the light-emitting element array-

[0242] In this example, the light-emitting element chip U has a light-emitting element array 67 with j light-emitting elements 65 arranged in a row.

[0243] In this example, the transmission signals (first transmission signal Φ1, second transmission signal Φ2) are sent to the light-emitting element chip U (reference) according to the transmission period TS (TS1, TS2, TS3...TSj-1, TSj) corrected according to the transmission period setting data DT2. Figure 13 (a)

[0244] The lighting signal ΦI is output in accordance with the transmission period TS.

[0245] At this time, in the light-emitting element chip U, a decrease in light intensity may occur due to the power supply direction (wiring length) or a decrease in the luminous efficiency of the light-emitting element that uses the current limiting resistor 69 as a heat source. However, in this example, for the light-emitting element group predicted to have a large amount of light intensity correction, correction was performed to ensure sufficient correctable width Th, so the aforementioned light intensity correction was appropriately corrected.

[0246] Furthermore, the write operation of the light-emitting element chip U is performed within the total time of the transmission period TS of the transmission signals of each light-emitting element 65. At this time, the total time of the transmission period TS is TS1+TS2+……TSj-1+TSj=j×TSc (TSc: reference transmission period).

[0247] Therefore, in this example, the writing process of the light-emitting element chip U is carried out within a predetermined period, and the light quantity variation caused by the power supply direction or current limiting resistor 69 can be appropriately corrected.

[0248] ◎Comparison Method 1

[0249] The comparison method 1 involves a light-emitting element chip U' that uses the same reference transmission period TSc for the transmission signal Φ1' for all light-emitting elements.

[0250] In this example, the write operation of the light-emitting element chip U' is performed within the total time (j×TSc) of the reference transmission period TSc of the transmission signal of each light-emitting element 65.

[0251] However, in this example, when the write speed of the light-emitting element chip U' is increased, the following adverse conditions may occur. For example, even if a decrease in light intensity occurs due to the power supply direction (wiring length) or a decrease in the luminous efficiency of the light-emitting element that uses the current limiting resistor 69 as a heat source, it may be impossible to ensure a sufficient correctable width Th for the light-emitting element group that is predicted to have a large amount of light intensity correction, making it difficult to properly correct light intensity variations.

[0252] ◎Implementation Method 2

[0253] Figure 14 (a) represents a structural example of the light-emitting element chip involved in Embodiment 2.

[0254] In this figure, the light-emitting element chip U is the same as in Embodiment 1, and has a light-emitting element array 67, a power supply pad 68, a current limiting resistor 69 and a light-on / light-off circuit 70 on the chip substrate 66.

[0255] However, the light-emitting element chip U involved in this example differs from that in Embodiment 1 in that the power supply pad 68 is disposed on one side of the last light-emitting element 65 (final point) of the light-emitting element array 67. Furthermore, the current limiting resistor 69 is also disposed on one side of the last light-emitting element 65 (final point) of the light-emitting element array 67.

[0256] In this example, the power supply direction to the light-emitting element array 67 is opposite to that in Embodiment 1, and the lighting and extinguishing actions are performed sequentially from the last light-emitting element 65 (final point) toward the first light-emitting element 65 (first point).

[0257] Furthermore, in this example, the last light-emitting element 65 (the final point) in the light-emitting element array 67 is close to the current limiting resistors 69 (RI1, RI2), and is therefore most susceptible to the effects of heat sources.

[0258] according to Figure 14 (c) It can be confirmed that the amount of light from each light-emitting element 65 gradually decreases from the side of the last light-emitting element 65 (final point) toward the power supply direction. In this example, it is also presumed, similarly to Embodiment 1, that the decrease in light amount is caused by the distance between the power supply pad 68 and the light-emitting element 65 or the wiring length, and the decrease in luminous efficiency is caused by the distance between the current limiting resistor 69, which is a heat source, and each light-emitting element 65, affecting the aforementioned change in light amount.

[0259] Currently, such as Figure 14 As shown in (c), the light-emitting element chip U has the characteristic that the amount of light gradually decreases from the last light-emitting element 65 (final point) in the light-emitting element array 67 toward the first light-emitting element 65 (first point).

[0260] Therefore, in this example, in order to correct Figure 14 The light intensity variation shown in (c) is as follows: Figure 15 As shown in (a), a correction amount is selected to expand the correctable width Th for the light-emitting element 65 (the left half region with the center of the light-emitting element array 67 as the boundary) that is predicted to have a large amount of light correction. In contrast, the correctable width Th is reduced for the light-emitting element 65 (the right half region with the center of the light-emitting element array 67 as the boundary) that is predicted to have a small amount of light correction.

[0261] Currently, the number j of light-emitting elements 65 in the light-emitting element array 67 is set to, for example, 512, and the correctable width Th during the reference transmission period is assumed to be T.

[0262] Since the correction amount for the 512th light-emitting element is the smallest, therefore, as Figure 15 As shown in (b), the correctable width Th is reduced to Ta.

[0263] Furthermore, the correction amount for the 512-N light-emitting elements located in the right half of the region, compared to the central position, is also less. Therefore, as... Figure 15 As shown in (b), the correctable width Th is reduced to Tb (a>b).

[0264] Furthermore, the Nth light-emitting element located in the left half of the region requires more correction compared to the central position; therefore, as Figure 15 As shown in (b), the correctable width Th is extended to T+c.

[0265] Furthermore, the first light-emitting element requires the most calibration amount, therefore, as Figure 15 As shown in (b), the correctable width Th is extended to T+d (d>c).

[0266] Furthermore, when considering the total correctable width Th of each light-emitting element, it is sufficient that it is equal to the correctable width T×j (j=512) of the reference transmission period.

[0267] ◎Implementation Method 3

[0268] Figure 16 (a) represents a structural example of the light-emitting element chip involved in Embodiment 3.

[0269] In this figure, the light-emitting element chip U is the same as in embodiments 1 and 2, and has a light-emitting element array 67, a power supply pad 68, a current limiting resistor 69 and a light-on / light-off circuit 70 on the chip substrate 66.

[0270] However, the light-emitting element chip U involved in this example differs from that in embodiments 1 and 2 in that the power supply pad 68 is disposed on one side of the first light-emitting element 65 (first point) of the light-emitting element array 67. Furthermore, the current limiting resistor 69 is disposed on the side opposite to the power supply pad 68 and on the side of the last light-emitting element 65 (final point) of the light-emitting element array 67.

[0271] In this example, such as Figure 16 As shown in (b), the power supply direction to the light-emitting element array 67 is the same as in Embodiment 1, and the lighting and extinguishing actions are performed sequentially from the first light-emitting element 65 (first point) to the last light-emitting element 65 (final point).

[0272] Furthermore, in this example, the last light-emitting element 65 (the final point) in the light-emitting element array 67 is close to the current limiting resistors 69 (RI1, RI2), and is therefore most susceptible to the effects of heat sources.

[0273] according to Figure 16 (c) Similar to Embodiment 1, it can be confirmed that the amount of light from each light-emitting element 65 gradually decreases from the side of the first light-emitting element 65 (first point) toward the power supply direction. However, in this example, unlike Embodiment 1, the trends of light reduction caused by the distance between the power supply pad 68 and the light-emitting element 65 or the wiring length, and the trend of luminous efficiency reduction caused by the distance between the current limiting resistor 69 (which is a heat source) and each light-emitting element 65, both show an upward-sloping trend in the figure. Therefore, compared to Embodiment 1, the aforementioned change in light amount is more pronounced on the side of the last light-emitting element 65 (final point).

[0274] Therefore, in this example, when correcting this change in light intensity, it is sufficient to perform the same correction as in Embodiment 1, but the correction amount needs to be appropriately larger than that in Embodiment 1.

[0275] ◎Implementation Method 4

[0276] Figure 17 (a) represents a structural example of the light-emitting element chip involved in Embodiment 4.

[0277] In this figure, the light-emitting element chip U is the same as in embodiments 1 to 3, and has a light-emitting element array 67, a power supply pad 68, a current limiting resistor 69 and a light-on / light-off circuit 70 on the chip substrate 66.

[0278] However, the light-emitting element chip U involved in this example differs from those in embodiments 1 to 3 in that the power supply pad 68 is disposed on one side of the first light-emitting element 65 (first point) of the light-emitting element array 67. Furthermore, the light-emitting element chip U has a pair of current-limiting resistors 69 (69a, 69b) on both sides of the main scanning direction of the light-emitting element array 67.

[0279] In this example, such as Figure 17 As shown in (b), the power supply direction to the light-emitting element array 67 is the same as in Embodiment 1, and the lighting and extinguishing actions are performed sequentially from the first light-emitting element 65 (first point) to the last light-emitting element 65 (final point).

[0280] Furthermore, in this example, the first light-emitting element 65 (point 1) and the last light-emitting element 65 (final point) in the light-emitting element array 67 are close to the current limiting resistors 69 (69a, 69b), and are therefore most susceptible to the effects of heat sources.

[0281] according to Figure 17 (c) It can be confirmed that the amount of light from each light-emitting element 65 gradually decreases from the side of the first light-emitting element 65 (first point) toward the power supply direction. However, in this example, the decrease in light amount caused by the power supply direction (wiring length) shows a downward-rightward trend from the first light-emitting element 65 (first point) toward the last light-emitting element 65 (final point) (see reference). Figure 17 (c) dashed line). In contrast, since a pair of current-limiting resistors 69 are provided, the first light-emitting element 65 (first point) and the last light-emitting element 65 (final point) are most strongly affected by the heat source. On the other hand, the light-emitting elements 65 located near the center of the main scanning direction of the light-emitting element array 67 are less affected by the heat source. Therefore, the characteristic of the reduction in luminous efficiency caused by the heat source shows a mountain-shaped trend with fewer elements in the center of the light-emitting element array 67 (see reference). Figure 17 (c) is a single-dot dashed line.

[0282] Therefore, in this example, the reduction in light intensity of the light-emitting element array 67 exhibits a tendency to tilt downward to the right in a state with a bending point near the center of the main scanning direction of the light-emitting element array 67.

[0283] Therefore, in this example, when correcting for this variation in light intensity, the following should be considered: Figure 17 The light intensity variation characteristics of (c) can be determined by appropriately selecting the correction amount.

[0284] ◎Implementation Method 5

[0285] Figure 18 (a) represents a structural example of the light-emitting element chip involved in Embodiment 5.

[0286] In this figure, the light-emitting element chip U is the same as in embodiments 1 to 4, and has a light-emitting element array 67, a power supply pad 68, a current limiting resistor 69 and a light-on / light-off circuit 70 on the chip substrate 66.

[0287] However, the light-emitting element chip U involved in this example differs from those in embodiments 1 to 4 in that it has a pair of power supply pads 68 (68a, 68b) on both sides of the main scanning direction of the light-emitting element array 67. Furthermore, the light-on / off circuit 70 has a light-on / off circuit (1) 70a powered from the power supply pad 68a and a light-on / off circuit (2) 70b powered from the power supply pad 68b. In this example, the light-on / off circuit (1) 70a serves as the left half of the light-emitting element group in the light-emitting element array 67, with the center as the boundary. On the other hand, the light-on / off circuit (2) 70b serves as the right half of the light-emitting element group in the light-emitting element array 67, with the center as the boundary. Moreover, the light-emitting element chip U has a pair of current-limiting resistors 69 (69a, 69b) on both sides of the main scanning direction of the light-emitting element array 67.

[0288] In this example, such as Figure 18 As shown in (b), the power supply direction to the light-emitting element array 67 is from both ends of the light-emitting element array 67 toward the center of the main scanning direction, and the lighting and extinguishing actions are performed sequentially along the power supply direction.

[0289] Furthermore, in this example, the first light-emitting element 65 (point 1) and the last light-emitting element 65 (final point) in the light-emitting element array 67 are close to the current limiting resistors 69 (69a, 69b), and are therefore most susceptible to the effects of heat sources.

[0290] according to Figure 18 (c) It can be confirmed that along the power supply direction from the end of the light-emitting element array 67 toward the center of the main scanning direction, the amount of light from each light-emitting element 65 gradually decreases. Therefore, in this example, the central portion of the light-emitting element array 67 shows a trend of decreasing light amount compared to the ends.

[0291] Here, the decrease in light intensity caused by the power supply direction (wiring length) exhibits a V-shaped trend with a peak at the center of the main scanning direction of the light-emitting element array 67 (see reference). Figure 18(c) point line). Moreover, since a pair of current-limiting resistors 69 (69a, 69b) are provided, the first light-emitting element 65 (first point) and the last light-emitting element 65 (final point) are most strongly affected by the heat source. On the other hand, the light-emitting elements 65 located near the center of the main scanning direction of the light-emitting element array 67 are less affected by the heat source. Therefore, the characteristic of the reduction in luminous efficiency caused by the heat source shows a mountain-shaped trend with fewer elements in the center of the light-emitting element array 67 (see reference). Figure 18 (c) is a single-dot dashed line.

[0292] Therefore, in this example, the reduction in light intensity of the light-emitting element array 67 exhibits a V-shaped trend with a bending point near the center of the main scanning direction of the light-emitting element array 67.

[0293] Therefore, in this example, when correcting for this variation in light intensity, the following should be considered: Figure 18 The light intensity variation characteristics of (c) can be determined by appropriately selecting the correction amount.

[0294] ◎Implementation Method 6

[0295] Figure 19 (a) represents a structural example of the light-emitting element chip array 63 according to embodiment 6.

[0296] In this example, similar to Embodiment 1, the light-emitting element chip array 63 is on the circuit board 62 (reference). Figure 4 An array structure in which multiple light-emitting element chips U (U0~U2m+1) are arranged in an alternating pattern.

[0297] Furthermore, in this example, such as Figure 19 As shown in (b), the even-numbered light-emitting element chips U (specifically U0, U2...U2m) have a light-emitting element array 67, a power supply pad (not shown), a current limiting resistor 69, and a light-on / light-off circuit (not shown) on the chip substrate 66.

[0298] In this example, the power supply direction to the light-emitting element array 67 is from the first light-emitting element 65 (first point) towards the last light-emitting element 65 (final point). Furthermore, the current-limiting resistor 69 is disposed on one side of the first light-emitting element 65 (first point) in the main scanning direction of the light-emitting element array 67.

[0299] And, as Figure 19 As shown in (c), the odd-numbered light-emitting element chips U (specifically U1, U3...U2m+1) have a light-emitting element array 67, a power supply pad (not shown), a current limiting resistor 69, and a light-on / off circuit (not shown) on the chip substrate 66.

[0300] In this example, the power supply direction to the light-emitting element array 67 is from the last light-emitting element 65 (final point) toward the first light-emitting element 65 (first point). Furthermore, the current-limiting resistor 69 is disposed on the side of the last light-emitting element 65 (final point) in the main scanning direction of the light-emitting element array 67.

[0301] In this example, the even-numbered light-emitting element chips U (U0, U2...U2m) are grouped into units and controlled by the transmission signal Φa as a common signal.

[0302] Furthermore, the light-emitting element chips U (U1, U3...U2m+1) in odd-numbered columns are also grouped into units and controlled by the transmission signal Φb as a common signal.

[0303] Figure 20 Figure (a) shows the relationship between the correction amount for the light intensity variation of the even-numbered light-emitting element chips U (U0, U2...U2m) and the position of each light-emitting element. According to this figure, the correction amount is set most for the first light-emitting element 65 (point 1) of the light-emitting element array 67, and least for the last light-emitting element 65 (final point). The correction amount referred to here is the average correction amount for the even-numbered light-emitting element chips U (even-numbered chips).

[0304] Figure 20 (b) illustrates an example of correction processing for light quantity variations in even-numbered light-emitting element chips U (U0, U2, ..., U2m). According to this figure, transmission signals Φa are supplied sequentially from the first light-emitting element 65 (point 1) towards the last light-emitting element 65 (final point), and each light-emitting element chip U repeatedly lights up and turns off in parallel. At this time, the transmission signal Φa is supplied by expanding or shrinking the transmission period TS based on the transmission period setting data DT2 (including correction amounts).

[0305] Figure 20 (c) represents the relationship between the correction amount for the light intensity variation of the odd-numbered light-emitting element chips U (U1, U3...U2m+1) and the position of each light-emitting element. According to this figure, regarding the correction amount, the last light-emitting element 65 in the light-emitting element array 67 is set with the most, and the first light-emitting element 65 (point 1) is set with the least. The correction amount mentioned here refers to the average correction amount of the odd-numbered light-emitting element chips U (odd-numbered chips).

[0306] Figure 20(d) represents an example of correction processing for light quantity variations in odd-numbered light-emitting element chips U (U1, U3...U2m+1). According to this diagram, transmission signals Φb are supplied sequentially in the direction where the last light-emitting element 65 (final point) is set as the first and the first light-emitting element 65 (first point) is set as the last, causing each light-emitting element chip U to repeatedly light up and turn off in parallel. At this time, the transmission signal Φb is supplied by expanding or shrinking the transmission period TS based on the transmission period setting data DT2 (including correction amounts).

[0307] (Postscript) (1)

[0309] A light-emitting device, characterized in that it comprises:

[0310] The light source unit has multiple light-emitting elements arranged on the substrate along the main scanning direction; and

[0311] The driving unit drives the multiple light-emitting elements by varying the emission time width according to the amount of light to be emitted within a predetermined period of time, thereby causing the multiple light-emitting elements to emit light.

[0312] The driving unit has a correction unit that performs correction within the correctable range of the light emission time width, i.e., within the correctable width range, and makes the correctable width different for each of the light emission elements. (2)

[0314] According to the light-emitting device described in (1), the characteristic is that,

[0315] The correction unit corrects the light-emitting elements whose predicted light intensity variation is large by making their correctable width larger than that of the light-emitting elements whose predicted light intensity variation is small. (3)

[0317] According to the light-emitting device described in (2), it is characterized in that,

[0318] The correction unit corrects light-emitting elements in which the predicted change in light intensity is greater than a predetermined reference change by making their correctable width greater than a predetermined reference value; and corrects light-emitting elements in which the predicted change in light intensity is less than the reference change by making their correctable width less than the reference value. (4)

[0320] The light-emitting device according to any one of (1) to (3) is characterized in that,

[0321] The system includes a power supply unit, which is located to the side of the end of the light source unit in the main scanning direction on the substrate, and supplies power to each light-emitting element.

[0322] The correction unit adjusts the correctable width according to the distance or wiring length between the power supply unit and the light-emitting element. (5)

[0324] According to the light-emitting device described in (4), it is characterized in that,

[0325] The correction unit performs correction in such a way that the longer the distance between the power supply unit and the light-emitting element or the wiring length, the longer the correctable width. (6)

[0327] The light-emitting device according to any one of (1) to (3) is characterized in that,

[0328] The system includes a resistor unit disposed on the side of the end of the light source unit in the main scanning direction within the substrate, which limits the current supplied to the light-emitting element.

[0329] The correction unit adjusts the correctable width of the light-emitting element according to the distance between the resistor unit and the light-emitting element. (7)

[0331] According to the light-emitting device described in (6), it is characterized in that,

[0332] The correction unit corrects the light-emitting element in such a way that the shorter the distance between the resistor unit and the light-emitting element, the longer the correctable width of the light quantity. (8)

[0334] The light-emitting device according to any one of (1) to (3) is characterized by comprising:

[0335] A power supply unit is disposed on the side of the end of the light source unit in the main scanning direction in the substrate, and supplies power to each light-emitting element; and

[0336] A resistor unit is disposed on the side of the end of the light source unit in the main scanning direction in the substrate, and limits the current supplied to the light-emitting element.

[0337] The power supply unit is positioned on the opposite side of the resistor unit, separated from the light source unit.

[0338] The correction unit adjusts the correctable width according to the distance or wiring length between the power supply unit and the light-emitting element, and the distance between the resistor unit and the light-emitting element. (9)

[0340] According to the light-emitting device described in (3), it is characterized in that,

[0341] When the correction unit corrects the correctable width of each of the light-emitting elements, it includes a first correctable width group that is greater than the reference value and a second correctable width group that is less than the reference value, and corrects the correctable width in such a way that the sum of the differences between the first correctable width group and the reference value and the sum of the differences between the second correctable width group and the reference value are of the same degree. (10)

[0343] The light-emitting device according to any one of (1) to (9) is characterized in that,

[0344] In the light source unit, the plurality of light-emitting elements are arranged in multiple groups.

[0345] The correction unit makes the correctable width of each of the light-emitting elements, which are divided into groups, different in parallel. (11)

[0347] According to the light-emitting device described in (10), it is characterized in that,

[0348] The light source unit consists of multiple systems that use a common driving signal for each identical group of units.

[0349] The correction unit performs the correction processing of the correctable width of the light-emitting element belonging to a group unit of any system and the correction processing of the correctable width of the light-emitting element belonging to a group unit of other systems in parallel. (12)

[0351] An optical writing device, characterized in that it comprises:

[0352] The light-emitting device according to any one of (1) to (11) is disposed opposite to an image holding unit capable of holding a light-based image; and

[0353] The imaging unit images the light emitted from each light-emitting element of the light-emitting device onto the image holding unit.

[0354] An image based on the light is written to the image holding unit. (13)

[0356] An image forming system, characterized in that it comprises:

[0357] The image holding unit is capable of holding light-based images; and

[0358] (12) The optical writing device described above

[0359] The light-based image held by the image holding unit is visualized and output.

[0360] According to the light-emitting device involved in (1), even if the transmission period of the driving signal given to each light-emitting element is shortened, the required light intensity adjustment width of each light-emitting element can be ensured within a predetermined period.

[0361] According to the light-emitting device involved in (2), compared with the light-emitting element with a small predicted change in light amount, the correctable width can be further extended for the light-emitting element with a large predicted change in light amount, thereby ensuring the required light amount adjustment width.

[0362] According to the light-emitting device involved in (3), for light-emitting elements with a large predicted change in light intensity and light-emitting elements with a small predicted change in light intensity, the correctable width is expanded or reduced by a predetermined reference value, thereby enabling the appropriate allocation of the required light intensity adjustment width.

[0363] According to the light-emitting device involved in (4), the light quantity variation factor of the light-emitting element is considered from the distance or wiring length between the power supply unit and the light-emitting element, thereby enabling the appropriate allocation of the required light quantity adjustment width to each light-emitting element with different light quantity variation.

[0364] According to the light-emitting device involved in (5), when the distance or wiring length between the power supply unit and the light-emitting element is long, the correctable width of the light-emitting element with a long distance or wiring length can be extended more than that of the light-emitting element with a short distance or wiring length, thereby ensuring the required light amount adjustment width.

[0365] According to the light-emitting device involved in (6), the distance between the resistor unit, which functions as a heat source, and the light-emitting element is considered as the factor affecting the variation of the light amount of the light-emitting element. In this way, the required light amount adjustment width can be appropriately allocated to each light-emitting element with different light amount variations.

[0366] According to the light-emitting device involved in (7), when the distance between the resistor unit and the light-emitting element is short, the correctable width of the light-emitting element with a short distance can be extended more than that of the light-emitting element with a long distance, thereby ensuring the required light amount adjustment width.

[0367] According to the light-emitting device involved in (8), even if it has a power supply unit and a resistor unit that functions as a heat source, the maximum amount of light variation can be suppressed by designing the positional relationship between the power supply unit and the resistor unit, and by considering the distance between the power supply unit and the light-emitting element or the wiring length and the distance between the resistor unit and the light-emitting element. Furthermore, the required light amount adjustment width can be appropriately allocated to each light-emitting element with different light amount variations within a predetermined period.

[0368] According to the light-emitting device involved in (9), for light-emitting elements with large predicted light quantity fluctuations and light-emitting elements with small predicted light quantity fluctuations, the total correction amount of expanding the correctable width and the total correction amount of reducing the correctable width with a predetermined reference value as the boundary are set to the same degree, thereby enabling the appropriate allocation of the required light quantity adjustment width to each light-emitting element with different light quantity fluctuations within a predetermined period.

[0369] According to the light-emitting device involved in (10), compared with the form in which multiple light-emitting elements are not arranged in groups, it is possible to share a correctable width in groups of multiple light-emitting elements and quickly perform the expansion and reduction of the correctable width.

[0370] According to the light-emitting device involved in (11), even if multiple light-emitting elements are arranged in an interleaved manner in each group unit and each uses a common driving signal, the light source unit of multiple systems can share a correctable width for each system and quickly perform the expansion and reduction processing of the correctable width.

[0371] According to the optical writing device involved in (12), an optical writing device including a light-emitting device can be constructed, which can ensure the required light amount adjustment width of each light-emitting element even when the transmission period of the driving signal given to each light-emitting element is shortened.

[0372] According to the image forming system involved in (13), it is possible to construct an image forming system including a light-emitting device that can ensure the required light intensity adjustment width for each light-emitting element even when the transmission period of the driving signal given to each light-emitting element is shortened.

[0373] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

Claims

1. A light-emitting device, characterized in that, have: The light source unit has multiple light-emitting elements arranged on the substrate along the main scanning direction; and The driving unit drives the multiple light-emitting elements by varying the emission time width according to the amount of light to be emitted within a predetermined period of time, thereby causing the multiple light-emitting elements to emit light. The driving unit has a correction unit that performs correction within the correctable range of the light emission time width, i.e., within the correctable width range, and makes the correctable width different for each of the light emission elements.

2. The light-emitting device according to claim 1, characterized in that, The correction unit corrects the light-emitting elements whose predicted light intensity variation is large by making their correctable width larger than that of the light-emitting elements whose predicted light intensity variation is small.

3. The light-emitting device according to claim 2, characterized in that, The correction unit corrects light-emitting elements in which the predicted change in light intensity is greater than a predetermined reference change by making their correctable width greater than a predetermined reference value; and corrects light-emitting elements in which the predicted change in light intensity is less than the reference change by making their correctable width less than the reference value.

4. The light-emitting device according to any one of claims 1 to 3, characterized in that, The system includes a power supply unit, which is located to the side of the end of the light source unit in the main scanning direction on the substrate, and supplies power to each light-emitting element. The correction unit adjusts the correctable width according to the distance or wiring length between the power supply unit and the light-emitting element.

5. The light-emitting device according to claim 4, characterized in that, The correction unit performs correction in such a way that the longer the distance between the power supply unit and the light-emitting element or the wiring length, the longer the correctable width.

6. The light-emitting device according to any one of claims 1 to 3, characterized in that, The system includes a resistor unit disposed on the side of the end of the light source unit in the main scanning direction within the substrate, which limits the current supplied to the light-emitting element. The correction unit adjusts the correctable width of the light-emitting element according to the distance between the resistor unit and the light-emitting element.

7. The light-emitting device according to claim 6, characterized in that, The correction unit corrects the light-emitting element in such a way that the shorter the distance between the resistor unit and the light-emitting element, the longer the correctable width of the light quantity.

8. The light-emitting device according to any one of claims 1 to 3, characterized in that, have: A power supply unit is disposed on the side of the end of the light source unit in the main scanning direction in the substrate, and supplies power to each light-emitting element; and A resistor unit is disposed on the side of the end of the light source unit in the main scanning direction in the substrate, and limits the current supplied to the light-emitting element. The power supply unit is positioned on the opposite side of the resistor unit, separated from the light source unit. The correction unit adjusts the correctable width according to the distance or wiring length between the power supply unit and the light-emitting element, and the distance between the resistor unit and the light-emitting element.

9. The light-emitting device according to claim 3, characterized in that, When the correction unit corrects the correctable width of each of the light-emitting elements, it includes a first correctable width group that is greater than the reference value and a second correctable width group that is less than the reference value, and corrects the correctable width in such a way that the sum of the differences between the first correctable width group and the reference value and the sum of the differences between the second correctable width group and the reference value are of the same degree.

10. The light-emitting device according to any one of claims 1 to 9, characterized in that, In the light source unit, the plurality of light-emitting elements are arranged in multiple groups. The correction unit makes the correctable width of each of the light-emitting elements, which are divided into groups, different in parallel.

11. The light-emitting device according to claim 10, characterized in that, The light source unit consists of multiple systems that use a common driving signal for each identical group of units. The correction unit performs the correction processing of the correctable width of the light-emitting element belonging to a group unit of any system and the correction processing of the correctable width of the light-emitting element belonging to a group unit of other systems in parallel.

12. An optical writing device, characterized in that, have: The light-emitting device according to any one of claims 1 to 11 is disposed opposite to an image holding unit capable of holding a light-based image; and The imaging unit images the light emitted from each light-emitting element of the light-emitting device onto the image holding unit. An image based on the light is written to the image holding unit.

13. An image forming system, characterized in that, have: The image holding unit is capable of holding light-based images; and The optical writing device according to claim 12, The light-based image held by the image holding unit is visualized and output.

Images