JP4893424B2 - Image processing apparatus and image processing program - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing program.

  In recent years, many image forming apparatuses such as printers use a semiconductor laser as a means for emitting exposure light toward an image carrier such as a photoconductor.

  The semiconductor laser has a temperature characteristic called a droop characteristic. In a semiconductor laser, when the temperature of the semiconductor laser itself rises, the laser light emission efficiency decreases, and even if the drive current control is performed on the semiconductor laser so that the laser light emission amount is constant, the laser light emission amount is low. A phenomenon in which a desired laser light quantity cannot be obtained due to a decrease, that is, a droop phenomenon occurs. When this droop phenomenon occurs, the portion where the laser light amount is reduced appears as a decrease in density on the printed matter.

  Specifically, when the high-concentration region and the low-concentration region are adjacent to each other and the laser scanning direction is from the high-concentration region to the low-concentration region (when the low-concentration region is located after the high-concentration region continues) ), The temperature of the semiconductor laser itself rises due to the laser emission corresponding to the high concentration region.

  When the semiconductor laser whose temperature has risen in this manner emits laser light corresponding to the low concentration region adjacent to the high concentration region, the laser light from the semiconductor laser related to the boundary portion between the low concentration region and the high concentration region is emitted. The light emission amount is lower than a predetermined light emission amount (specified value) for the low density region. In other words, the boundary portion between the low density area and the high density area in the printed material has an image quality of “whiteout”.

As apparatuses for taking a countermeasure against the droop phenomenon and performing a printing process, those disclosed in Patent Document 1 and Patent Document 2 are known.
JP 2002-307751 A JP-A-9-314908

  The present invention provides an image processing apparatus and an image processing program capable of suppressing image quality defects due to a droop phenomenon related to a semiconductor laser based on pulse width information indicating a pulse width of a laser beam emitted from the semiconductor laser. For the purpose.

In order to solve the above-described problem, the image processing apparatus according to the first aspect of the present invention provides m (m is a positive integer) bit pixel data as n (n is a positive integer, n <m) bit pixel data. A conversion unit that converts the pixel into a pixel immediately before the pixel of interest, and a past pixel corresponding to a predetermined number of pixels related to pixel data that has been converted by the conversion unit. Storage means for storing pulse width information indicating a pulse width of a laser beam emitted from a semiconductor laser corresponding to the n-bit pixel data, and the m related to the target pixel based on the storage content of the storage means a generating means for generating a correction value for the bit of pixel data, and correction means for correcting the pixel data of the m bits relating to the target pixel based on the correction value generated by the generating means Have, the converting means converts the m-bit pixel data relating to the target pixel corrected by the correcting means to pixel data of the n bits, and wherein the.

According to a second aspect of the present invention, in the first aspect of the invention, the storage unit converts the pulse width information and the conversion unit with respect to past pixels corresponding to the predetermined number of pixels . The pulse position information indicating the position of the pulse irradiated to the irradiation area corresponding to the pixel related to the pulse emitted corresponding to the n-bit pixel data is stored in association with each other. .
According to a third aspect of the present invention, in the second aspect of the present invention, the generating means is based on the pulse width information and the pulse position information of each past pixel corresponding to the predetermined number of pixels. A counter that executes an operation to increase or decrease the counter value, and the counter emits the laser light corresponding to successive pixels based on the pulse width information and the pulse position information of each pixel. Are determined to be different from each other, and the value for increasing the counter value is varied according to the determined result. Further, the generation means includes all the past pixels corresponding to the predetermined number of pixels. Corresponding to the counter value obtained as a result of the calculation when the calculation by the counter is executed, the correction value for the m-bit pixel data related to the target pixel is generated. To, characterized in that.
The invention according to claim 4 is the invention according to claim 3, characterized in that the counter value as a result of the calculation and the correction value are in a proportional relationship.

Invention of Claim 5 is further provided with the detection means which detects the boundary part of the high concentration area | region and low concentration area | region in image data in the invention as described in any one of the said Claims 1-4 , The correction means corrects the m-bit pixel data related to the boundary portion detected by the detection means based on the correction value generated by the generation means.

In order to solve the above problem, the image processing program according to the present invention described in claim 6 converts m (m is a positive integer) bit pixel data into n (n is a positive integer, n <m) bit pixel data. a conversion step of converting, with respect past pixel corresponding to a predetermined number of pixels involved in the pixel data of the immediately preceding pixel in the reference is the target of conversion by the conversion process of the pixel of interest, by the conversion process A storage process for storing pulse width information indicating a pulse width of a laser beam emitted from a semiconductor laser corresponding to the converted n-bit pixel data, and a storage content stored in the storage process. wherein a generation process of generating a correction value for said m-bit pixel data relating to the target pixel, the pixel data of the m bits according to the pixel of interest in the generation process to A correction process for correcting based on the generated correction value Ri has the conversion process, the pixel data of the m bits according to the pixel of interest after being corrected by the correction processing step n The method includes a process of converting into bit pixel data, and causes the computer to execute the conversion process, the storage process, the generation process, and the correction process .

  According to the first aspect of the present invention, it is possible to correct gradation data based on pulse width information related to laser light emitted from a semiconductor laser, and to suppress image quality defects due to a droop phenomenon related to the semiconductor laser.

According to the second aspect of the present invention, gradation data is corrected based on pulse width information and pulse position information related to laser light emitted from a semiconductor laser, and image quality defects due to a droop phenomenon related to the semiconductor laser are suppressed. Can do.
According to the invention described in claim 3, based on the pulse width information and the pulse position information related to the laser beam emitted from the semiconductor laser, the temperature rise of the semiconductor laser in the multi-value halftone process is accurately predicted and the level is increased. It is possible to correct the tone data and suppress image quality defects due to the droop phenomenon related to the semiconductor laser.
According to the fourth aspect of the present invention, it is possible to accurately predict the temperature rise of the semiconductor laser in the multi-value halftone process, and to generate a correction value in consideration of the predicted result.

According to the invention described in claim 5, the pulse width information related to the laser beam emitted from the semiconductor laser, or the pulse width information and the pulse position information related to the laser beam, and It is possible to correct gradation data related to the boundary portion and suppress image quality defects due to the droop phenomenon related to the semiconductor laser.

According to the sixth aspect of the present invention, there is provided software for correcting gradation data based on pulse width information related to laser light emitted from a semiconductor laser and suppressing image quality defects due to a droop phenomenon related to the semiconductor laser. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  (Embodiment 1)

  FIG. 1 shows a functional configuration of an image processing apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the image processing apparatus 100 includes a gradation correction unit 110, a droop correction unit 120, a halftone processing unit 130, and a pulse width modulation unit 140.

  The gradation correction unit 110 performs γ correction or the like on the received gradation data GD1 according to the characteristics of the laser printer, and outputs the gradation data GD2 after the gradation correction to the droop correction unit 120. Here, each gradation data of the gradation data GD1 and the gradation data GD2 is composed of m-bit gradation data (m is a positive integer).

  In the present specification, gradation data means pixel data.

  The droop correction unit 120 includes a pulse information storage unit 121 and a gradation data correction unit 122.

  The pulse information storage unit 121 has a function of storage means, and is constituted by, for example, a FIFO (First In First Out) memory. The pulse information storage unit 121 converts the gradation data (halftone data) converted by the halftone processing unit 130 with respect to past pixels corresponding to a predetermined number of pixels set in advance with reference to the pixel immediately before the target pixel. ), Pulse width information indicating the pulse width of laser light emitted from a semiconductor laser (not shown) is stored.

  The gradation data correction unit 122 includes a counter 122a and a lookup table (hereinafter referred to as “LUT”) 122b.

  The counter 122a is for counting the temperature rise of the semiconductor laser, and according to whether or not the laser emission by the semiconductor laser is indicated (indicating ON) corresponding to the gradation data regarding the pixel to be processed. To increase or decrease the count value. The value of increase or decrease is “1”.

  The LUT 122b is for obtaining a correction value for the gradation data in accordance with the temperature characteristics of the semiconductor laser. Specifically, the LUT 122b is an LUT for converting the counter value by the counter 122a into a correction value for the gradation data. . The LUT 122b stores counter values and correction values in association with each other.

  Such a gradation data correction unit 122 has a function of a generation unit and a function of a correction unit. When functioning as a generation unit, the stored content (for example, a plurality of gradation data) of the pulse information storage unit 121 is used. When the correction value is generated based on the read stored contents using the counter 122a and the LUT 122b and functions as a correction unit, the gradation data GD2 after the gradation correction from the gradation correction unit 110 is stored in the above-described manner. Correction (droop correction) is performed based on the generated correction value.

  Further, the gradation data correction unit 122 outputs the gradation data after the above correction (after droop correction) to the harp tone processing unit 130 as gradation data GD3 after droop correction. Here, each gradation data of the gradation data GD3 is composed of m-bit (m is a positive integer) bit gradation data.

  That is, the droop correction unit 120 performs droop correction on the received gradation data GD2 after gradation correction, and outputs the gradation data GD3 after droop correction to the halftone processing unit 130.

  The halftone processing unit 130 has a function of a conversion unit, and converts m (m is a positive integer) bit gradation data (pixel data) to n (n is a positive integer, n <m) bits. Convert to key data (pixel data).

  In other words, the halftone processing unit 130 converts the received gradation data GD3 (m-bit gradation data) after droop correction into binary halftone data (n-bit gradation data) using a dither matrix or the like. The halftone data HTD after the halftone process is output to the pulse width modulation unit 140 and the droop correction unit 120 (the pulse information storage unit 121 thereof).

  In the first embodiment, n (positive integer, n <m) -bit gradation data is assumed to be 1-bit (binary) gradation data.

  A pulse width modulation unit (hereinafter referred to as “PWM (Pulse Width Modulation) unit”) 140 converts the received halftone data HTD into a laser drive signal, and the laser drive signal LDS after the conversion is not shown in the drawing. Output to the drive unit.

  In the first embodiment, the tone correction unit 110, the droop correction unit 120, and the halftone processing unit 130 are a program (software) for realizing the functions of these components and a processing procedure described later (FIG. 2). A predetermined program (image processing program) including a program (software) corresponding to the reference (reference) is stored in a memory such as a ROM (Read Only Memory), and a CPU (Central Processing Unit) Is realized by reading out and executing the image processing program from the memory. As the image processing program is executed by the CPU, gradation correction processing, droop correction processing, halftone processing, and the like are performed.

  Of course, the gradation correction unit 110, the droop correction unit 120, and the halftone processing unit 130 may be configured by hardware.

  In the droop correction unit 120, the pulse information storage unit 121 is realized by, for example, a FIFO (first-in first-out) memory, and the LUT 122b is realized by, for example, a ROM (read-only memory).

  Next, image processing of the image processing apparatus 100 will be described with reference to FIG.

  FIG. 2 is a flowchart showing the processing procedure of the image processing.

  When gradation data GD1 from a printer controller (not shown) is input to the gradation correction unit 110 of the image processing apparatus 100, the gradation correction unit 110 performs gradation correction processing such as γ correction on the acquired gradation data GD1. (Step S101), and outputs the gradation correction result, that is, gradation data GD2 after gradation correction, to the droop correction unit 120.

The gradation data GD2 is input to the gradation data correction unit 122 of the droop correction unit 120.

  In the droop correction unit 120, the pulse information storage unit 121 stores the halftone data HTD that has been halftone processed by the halftone processing unit 130. This halftone data HTD is binary halftone data and is pulse width information.

  The gradation data correction unit 122 reads the halftone data HTD from the pulse information storage unit 121 (step S102), calculates a correction value based on the read halftone data (step S103), and performs gradation correction. The calculated correction value is added to the gradation data GD2 from the unit 110 (step S104).

  Then, the gradation data correction unit 122 outputs the gradation data after the addition processing to the halftone processing unit 130 as gradation data GD3 after droop correction (step S105).

  Thus, the process of adding the correction value to the gradation data GD2 means that the droop correction process for the gradation data GD2 is performed. Details of the droop correction process will be described later.

  The halftone processing unit 130 performs halftone processing (converting the gradation data GD3 into halftone data binarized by a dither matrix or the like) on the gradation data GD3 (step S106), and after this halftone processing The halftone data HTD (binary gradation data) is output to the PWM unit 140 and the droop correction unit 120 (pulse information storage unit 121 thereof) (step S107).

  In the droop correction unit 120, the pulse information storage unit 121 stores the halftone data HTD as light emission history information (history information of pulse width information) (step S108).

  The PWM unit 140 converts the received halftone data HTD into a laser drive signal, and outputs the converted laser drive signal LDS to a laser drive unit (not shown) (step S109).

  The image processing as described above will be described with a specific example.

  As shown in FIG. 3, the image data to be printed is image data in which a density region (high density region) 101 having a density of 80% and a density region (low density region) 102 having a density of 20% are adjacent in the X direction. Suppose that

  Further, it is assumed that the laser scanning direction is the direction from the high concentration region 101 to the low concentration region 102 (the direction of the solid arrow in FIG. 3, that is, the X direction). To position).

  Furthermore, in the example shown in FIG. 3, the Nth line in the Y direction is scanned by the semiconductor laser.

  Under the above-described preconditions, the halftone processing unit 130 performs the halftone processing on the processing result obtained by performing the gradation correction processing and the droop correction processing on the image data (gradation data) illustrated in FIG. 3. As a result of the halftone processing, as shown in FIG. 4A, binary halftone data HTD101 is output corresponding to the high density area 101 and binary corresponding to the low density area 102. Halftone data HTD102.

  Here, the PWM unit 140 converts the halftone data HTD101 and 102 corresponding to the gradation data related to each pixel of the Nth line into a laser drive signal LDS, and this laser drive signal LDS is converted into a laser drive unit (not shown). 4), the laser light emitted from the semiconductor laser (not shown) driven by the laser driving unit has a laser emission pattern as shown in FIG.

  That is, when the halftone processing unit 130 outputs the halftone data shown in FIG. 5B toward the PWM 140 corresponding to the gradation data shown in FIG. 5A, the semiconductor laser (not shown) outputs the halftone data. Emits a laser beam corresponding to the laser emission pattern shown in FIG.

  5A shows gradation data relating to pixels on the Nth line, FIG. 5B shows laser width information (halftone data) relating to pixels on the Nth line, and FIG. FIG. 5C shows a laser emission pattern based on the laser width information (halftone data) shown in FIG.

  5A and 5B exemplify 24 pixels P1 to P24, and symbols such as P1, P5, P10, P15, P20, and P24 are given to some of the pixels. . It should be noted that the 24 pixels are given the codes “P1”, “P2”,..., “P23” and “P24” in order from the top pixel.

  Further, the gradation data and the laser width information are expressed by 8-bit data. In FIG. 5A, a value “204” and a value “51” each indicate a gradation value corresponding to the density, and (80) in the vicinity of the value “204” is {(205 gradations / 256 gradations) × Means a value of 100} (truncated after the decimal point), and (20) in the vicinity of the value “51” means {(52 gradations / 256 gradations) × 100} (truncates after the decimal point). In FIG. 5B, a value “255” and a value “0” each indicate a halftone value corresponding to the density, and (100) in the vicinity of the value “255” is {(256 gradations / 256 gradations) × 100}.

  Next, the droop correction process by the droop correction unit will be described.

  The gradation correction unit 110 performs gradation correction processing on the gradation data shown in FIG. 6A (the same as the gradation data shown in FIG. 5A) as the acquired gradation data GD1, The gradation data GD2 after the gradation correction is output to the droop correction unit 120.

  Further, it is assumed that the pulse information storage unit 121 can store gradation data (pixel data) of past pixels corresponding to the number of 16 pixels, that is, halftone data, based on the pixel immediately before the target pixel.

  In the first embodiment, the halftone data regarding a pixel means pulse width information indicating a pulse width of 0% or 100%.

  Here, when the gradation data correction unit 122 receives the gradation data GD2 related to the third pixel P3, the gradation data correction unit 122, as shown in FIG. 6B, the pixel P3 as the target pixel. A droop correction process is performed on the gradation data related to.

  When performing the droop correction process, the gradation data correction unit 122 resets the counter value of the counter 122a (counter value = 0), and then the halftone related to the past pixel immediately before the target pixel from the pulse information storage unit 121. Read data. In this case, the halftone data relating to the pixel existing farthest from the target pixel is read in order.

  The gradation data correction unit 122 increases the counter value of the counter 122a when the halftone data sequentially read out indicates “255” (means laser light emission), and “0” (means that the laser is turned off). The counter value of the counter 122a is decreased.

  In this example, the halftone data (data indicating “255”) related to the image P1 of the first pixel and the halftone data (data indicating “255”) related to the image P2 of the second pixel are read out. The counter value of “2” is “2”.

  The gradation data correction unit 122 calculates a corresponding correction value from the LUT 122b based on the counter value “2”, and adds the calculated correction value to the gradation data GD2 related to the pixel P3 as the target pixel. Thus, the droop correction is performed on the gradation data GD2.

  The gradation data GD2 subjected to the droop correction in this manner is output to the halftone processing unit 130 as the gradation data GD3 after the droop correction.

  In the halftone processing unit 130, the gradation data GD3 related to the pixel P3 is converted into halftone data (binary halftone data) indicating the value “255” by performing halftone processing. The halftone data is output toward the PWM unit 140 and the pulse information storage unit 121 of the droop correction unit 120.

  As a result, as shown in FIG. 6C, the halftone data relating to the pixels corresponding to the number of three pixels from the pixel P1 to the pixel P3 is stored in the pulse information storage unit 121.

  The droop correction process and the halftone process as described above are completed for each pixel from the first pixel P1 to the 17th pixel P17 as shown in FIG. 6D, and the target pixel is the 18th pixel. Suppose that it shifted to P18. In this case, the pulse information storage unit 121 stores halftone data corresponding to the number of 16 pixels from the pixel P2 to the pixel P17.

  The gradation data correction unit 122 that performs the droop correction process on the gradation data GD2 of the pixel P18 as the target pixel resets the counter value of the counter 122a (counter value = 0), and then receives the attention from the pulse information storage unit 121. Pixel P2, pixel P3,..., Pixel P16 and pixel P17 are sequentially read out as halftone data relating to the previous pixel immediately before the pixel, and the read binary halftone data (value “255” or value) The counter value of the counter 122a is increased or decreased according to (0 indicating data).

  In this example, as shown in FIG. 6D, there are 10 pixels corresponding to the halftone data indicating “255”, and 6 pixels corresponding to the halftone data indicating “0”. The counter value of the final counter 122a is “4”.

  The gradation data correction unit 122 obtains a corresponding correction value from the LUT 122b based on the counter value “4”, and adds the obtained correction value to the gradation data GD2 related to the pixel P18 as the target pixel, Droop correction is performed on the gradation data GD2.

  Here, the counter value and the correction value are in a proportional relationship, and for example, the relationship of “(correction value corresponding to counter value“ 4 ”)> (correction value corresponding to counter value“ 2 ”)” is established. .

  The gradation data GD2 subjected to the droop correction in this manner is output to the halftone processing unit 130 as the gradation data GD3 after the droop correction.

  Then, the halftone processing unit 130 converts the gradation data GD3 related to the pixel P18 into halftone data (binary halftone data) indicating, for example, a value “0” by performing halftone processing. The halftone data is output toward the PWM unit 140 and the pulse information storage unit 121 of the droop correction unit 120.

  As a result, the halftone data relating to the pixel P18 is stored in the pulse information storage unit 121 as shown in FIG. In this case, the pulse information storage unit 121 stores halftone data corresponding to the number of 16 pixels from the pixel P3 to the pixel P18.

  The droop correction process and the halftone process as described above are performed for all the pixels of the N line.

  Then, the PWM unit 140 converts the binary halftone data as a result of the halftone process on the gradation data GD3 after the droop correction by the halftone processing unit 130 into the laser drive signal LDS, and the laser drive after the conversion The signal LDS is output toward a laser driving unit (not shown).

  When the laser drive unit drives the semiconductor laser in accordance with the laser drive signal LDS, when the semiconductor laser emits laser light corresponding to the high concentration region 101, the light emission amount of the laser light is a predetermined light emission to the high concentration region 101. On the other hand, when laser light is emitted corresponding to the low concentration region 102, the light emission amount of the laser light becomes a predetermined light emission amount for the low concentration region 102. That is, fluctuations in the amount of laser light emitted from the semiconductor laser are suppressed.

  In the first embodiment, the correction value may be calculated by selecting an appropriate method according to the temperature characteristics of the semiconductor laser. For example, in order to cope with a case where the temperature rise of continuous light emission is non-linear, the value to increase the counter value is changed according to the number of continuous light emission (ON).

  (Embodiment 2)

  Next, an image processing apparatus according to the second embodiment will be described.

  The image processing apparatus according to the second embodiment has the same configuration as that of the image processing apparatus 100 according to the first embodiment shown in FIG.

  The halftone processing unit 130 converts the gradation data GD3 into halftone data of a ternary or higher level using a dither matrix or the like. That is, the halftone processing is multivalue processing (multivalue halftone processing) using pulse width modulation.

  In the second embodiment, in the case of 8-bit data representation, four types of halftone data of 0%, 25% (gradation value 64), 50% (gradation value 128), and 100% (gradation value 255) are used. Exists.

  In general, in multi-value halftone processing, in order to obtain a stable toner image, halftone data (halftone data) is used so as not to isolate laser light pulses (laser pulses) having an intermediate width of 25% and 50%. Column).

  The pulse information storage unit 121 relates to the pulse width information (pulse light amount information) corresponding to a predetermined pixel and the predetermined pulse related to the pulse of laser light emitted from the laser corresponding to the predetermined pixel (laser pulse). The pulse position information indicating the position of the pulse irradiated on the irradiation area corresponding to the pixel is stored in association with each other. This is because an accurate temperature rise can be predicted even in multi-value halftone processing.

  In other words, the temperature rise of the semiconductor laser in the case of continuous pulse emission is different from the temperature rise of the semiconductor laser in the case of isolated pulse emission. It is necessary to accurately obtain a correction value (correction amount) for correction. For this purpose, it is only necessary to know whether the pulse for the pixel of interest is in an isolated state with a pulse having an intermediate width or is continuous with the pulse for an adjacent pixel. In order to realize this, pulse width information and pulse position information are stored in a pulse information storage unit.

  In the second embodiment, the halftone data regarding a pixel means pulse width information indicating a pulse width of 0%, 25%, 50%, or 100%, and pulse position information regarding the pulse.

  When calculating the correction value, the gradation data correction unit 122 obtains the correction value in consideration of not only laser light emission (ON) or light extinction (OFF) but also the pulse width and pulse position.

  In the gradation data correction unit 122, the counter 122a sets the current counter value to a predetermined value according to the halftone data of any of the above-described four types of halftone data as the halftone data related to the pixel to be processed. Add the values.

  In the case of 0% level halftone data, for example, “−10” is added to the current counter value.

  For halftone data at a level of 100%, for example, “+10” is added to the current counter value.

  In the case of 25% level halftone data, if a pulse for the pixel exists in isolation, for example, “+2” is added to the current counter value, and the pulse for the pixel continues to a continuous pulse. In this case, a value larger than “+2”, for example, “+6” is added to the current counter value.

  In the case of 50% level halftone data, if a pulse for the pixel exists in isolation, for example, “+4” is added to the current counter value, and the pulse for the pixel continues to a continuous pulse. In this case, a value larger than “+4”, for example, “+5” is added to the current counter value.

  Note that the added values such as “−10”, “2”, and “4” described above are merely examples, and are not limited to these values.

  Next, image processing of the image processing apparatus 100 according to the second embodiment will be described with reference to FIG.

  FIG. 7 is a flowchart showing the processing procedure of the image processing.

  When gradation data GD1 from a printer controller (not shown) is input to the gradation correction unit 110 of the image processing apparatus 100, the gradation correction unit 100 performs gradation correction processing such as γ correction on the acquired gradation data GD1. (Step S201), and outputs the result of the gradation correction processing, that is, the gradation data GD2 after the gradation correction to the droop correction unit 120.

  The gradation data GD3 is input to the gradation data correction unit 122 of the droop correction unit 120.

  In the droop correction unit 120, the pulse information storage unit 121 stores the halftone data HTD that has been halftone processed by the halftone processing unit 130. This halftone data HTD is quaternary halftone data, and is pulse width information and pulse position information.

  The gradation data correction unit 122 reads the halftone data HTD from the pulse information storage unit 121 (step S202), calculates a correction value based on the read halftone data (step S203), and performs gradation correction. The calculated correction value is added to the gradation data GD2 from the unit 110 (step S204).

  Then, the gradation data correction unit 122 outputs the gradation data GD3 after the loop correction of the addition process to the halftone processing unit 130 (step S205).

  Thus, the process of adding the correction value to the gradation data GD2 means that the droop correction process for the gradation data GD2 is performed. Details of the droop correction process will be described later.

  The halftone processing unit 130 performs halftone processing on the gradation data GD3 (converting the gradation data GD3 into halftone data that has been multivalued (quaternarized) using a dither matrix or the like) (step S206). The halftone data HTD (four-valued pixel data) after the halftone process is output to the PWM unit 140 and the droop correction unit 120 (pulse information storage unit 121 thereof) (step S207).

  In the droop correction unit 120, the pulse information storage unit 121 stores the halftone data HTD as light emission history information (history information of pulse width information and pulse position information) (step S208).

  The PWM unit 140 converts the received halftone data HTD into a laser drive signal, and outputs the converted laser drive signal LDS toward a laser drive unit (not shown) (step S209).

  The image processing as described above will be described with a specific example.

  As in the case of the first embodiment, the image data to be printed includes the density area (high density area) 101 having a density of 80% and the density area (low density area) having a density of 20%, as shown in FIG. ) 102 is image data adjacent in the X direction. Further, the laser scanning direction and the scanning target line are also assumed to be the X direction and the Nth line, respectively, as in the first embodiment.

  Under the above-described preconditions, the halftone processing unit 130 performs the halftone processing on the processing result obtained by performing the gradation correction processing and the droop correction processing on the image data (pixel data) illustrated in FIG. 3. As a result of the halftone processing, as shown in FIG. 8A, four-value halftone data HTD201 is output corresponding to the high density region 101, and four values are corresponding to the low density region 202. Halftone data HTD202 is output.

  Here, the PWM unit 140 converts the halftone data HTD201 and 202 corresponding to the grayscale data related to the pixels of the Nth line into a laser drive signal LDS, and this laser drive signal LDS is converted into a laser drive unit (not shown). ), The laser light emitted from the semiconductor laser (not shown) driven by this laser drive unit is actually a laser emission pattern as shown in FIG. In consideration of the pulse position of the laser beam, a laser emission pattern as shown in FIG.

  In FIGS. 8B and 8C, symbol # 101 corresponds to halftone data HTD201N related to pixels on the Nth line of the high density region 101 in the halftone image shown in FIG. 8A. A light emission pattern is shown.

  Next, the light emission pattern # 101 and the halftone data HTD201N will be described with reference to FIGS.

  FIG. 9 is a rewrite of the contents (light emission pulse) shown in FIG. In the figure, pulse waveforms indicating light emission (ON) are denoted by A1, A2,..., A9, A10 in order of fast scanning start.

  FIG. 10A shows an example of halftone data HTD201N. In the figure, reference signs A1 to A10 correspond to the reference signs A1 to A10 shown in FIG. 9 and mean halftone data (pulse width information and pulse position information) corresponding to the corresponding pulse.

  FIG. 10B is a rewrite of the contents (light emission pulse) shown in FIG. In the figure, reference signs A1 to A10 correspond to reference signs A1 to A10 shown in FIG.

  This halftone data HTD201N is composed of halftone data corresponding to 16 pixels from the first pixel P1 to the 16th pixel P16. Halftone data corresponding to one pixel is data in which pulse width information and pulse position information are associated with each other.

  “Left” in the pulse position information indicates that the laser pulse emits light corresponding to a predetermined pulse width with the left of the corresponding pixel region as a base point. Further, “right” in the pulse position information indicates that the laser pulse emits light corresponding to a predetermined pulse width with the right of the corresponding pixel region as a base point.

  Halftone data corresponding to a predetermined number of pixels set in advance with reference to the pixel immediately before the target pixel is stored in the pulse information storage unit 121. When the predetermined number of pixels is “15” and the target pixel is the pixel P16, halftone data corresponding to 15 pixels from the pixel P1 to the pixel P15 is stored in the pulse information storage unit 121. become.

  Meanwhile, the pulse waveforms A1 to A10 shown in FIG. 9 are obtained based on the pulse width information in the halftone data HTD201N shown in FIG.

  That is, the PWM 140 converts the pulse width information in the halftone data HTD201N transmitted from the halftone processing unit 130 into the light emission pattern shown in FIG. This light emission pattern becomes a laser drive signal.

  For example, the pulse width information “50” related to the pixel P1 is converted into a pulse waveform A1, and the pulse width information “100” related to four pixels from the pixel P3 to the pixel P6 is converted into a pulse A3. Similarly, pulse width information relating to other pixels is also converted into corresponding pulses.

  In other words, it can be said that the light emission pattern shown in FIG. 9 is a light emission pattern obtained when only the pulse width information in the halftone data is considered and the pulse position information is not considered.

  However, in practice, the PWM 140 is based on the pulse width information and the pulse position information (see FIG. 10A) in the halftone data HTD201N transmitted from the halftone processing unit 130. It converts into the light emission pattern shown (same as the light emission pattern of FIG.8 (c)).

  Next, the droop correction process by the droop correction unit will be described.

  The gradation correction unit 110 acquires gradation data related to the Nth line pixel in the image data shown in FIG. 3 as gradation data GD1, and performs gradation correction processing on the gradation data GD1. The gradation data GD2 after the gradation correction is output to the droop correction unit 120.

  Further, it is assumed that the pulse information storage unit 121 can store gradation data of past pixels corresponding to the number of 15 pixels, that is, halftone data, with reference to the pixel immediately before the target pixel. Here, in the example shown in FIG. 10A, it is assumed that the pixel of interest is the pixel P16, and halftone data corresponding to the number of 15 pixels from the pixel P1 to the pixel P15 is stored in the pulse information storage unit 121.

  When performing the droop correction process, the gradation data correction unit 122 resets the counter value of the counter 122a (counter value = 0), and then the halftone related to the past pixel immediately before the target pixel from the pulse information storage unit 121. Read data. In this case, the halftone data relating to the pixel to be processed is read in order from the halftone data relating to the pixel existing at the position farthest from the target pixel. For example, when the target pixel is the pixel P16, each pixel from the first pixel P1 to the pixel P15 immediately before the target pixel becomes a pixel to be processed in order from the pixel P1.

  Next, the gradation data correction unit 122 adds a predetermined addition value to the current counter value of the counter 122a based on the read halftone data, and calculates a corresponding correction value from the LUT 122b based on the final counter value. At the same time, the obtained correction value is added to the gradation data GD2 related to the pixel P16 as the target pixel, and droop correction is performed on the gradation data GD2.

  Also in the second embodiment, as in the first embodiment, when the halftone data related to the pixel to be processed means laser emission (pulse width = 25%, 50%, 100%). The counter value is increased to any one of the above values, and when the laser is turned off (pulse width = 0%), the counter value is decreased.

  However, in the second embodiment, the following (1) and (2) are used to increase the counter value in order to accurately predict a temperature rise when laser light is emitted corresponding to the pixel to be processed. ) Is counted up.

  (1) The counter value is increased according to which value (pulse width) of the laser pulse emitted by laser light corresponding to the pixel to be processed is 25%, 50% or 100%. The value (added value) to be changed is changed. In this case, the pulse width of the laser pulse can be known by referring to the pulse width information of the halftone data acquired from the pulse information storage unit 211.

  (2) When the pulse width of the laser pulse emitted corresponding to the pixel to be processed is an intermediate width such as 25% or 50%, the immediately preceding or immediately following laser pulse (immediately or immediately following the laser pulse) The continuity with the laser pulse corresponding to the pixel is determined, and the value (added value) for increasing the counter value is changed according to the determined result. That is, the value for increasing the counter value is made different depending on whether or not the laser emission is continuous.

  In this case, the continuity of the laser pulse can be known by referring to the pulse width information and pulse position information of the halftone data acquired from the pulse information storage unit 211. Also, the pulse width information of the halftone data relating to the immediately preceding or immediately following pixel (adjacent pixel) means that the pulse width = 100% and the intermediate width such as pulse width = 25% or 50%. There is a case.

  Here, the count-up process of the counter 122a will be specifically described.

  (A) Processing when the pulse width of a laser pulse related to a pixel to be processed is 100% will be described.

  The gradation data correction unit 122 is a pulse width of the laser pulse emitted by the laser corresponding to the pixel to be processed, that is, halftone data (pulse width information and pulse position) related to the pixel acquired from the pulse information storage unit 121. If the (information) pulse width information means 100%, "+10" is added to the current counter value of the counter 122a.

  For example, when the pixel to be processed is the pixel P5 shown in FIG. 10A, since the pulse width information is 100%, “+10” is added to the current counter value of the counter 122a.

  (B) Processing when the pulse width of the laser pulse related to the pixel to be processed is an intermediate width and the pulse width of the laser pulse related to the adjacent pixel is 100% will be described.

  The gradation data correction unit 122 indicates that the pulse width information of the halftone data related to the processing target pixel acquired from the pulse information storage unit 121 means 25% or 50% (the pulse width means an intermediate width). The pulse position information corresponding to the pulse width information is acquired, and halftone data (pulse width information and pulse position information) related to the pixel adjacent to the pixel is obtained based on the pulse position information. Obtained from the pulse information storage unit 212.

  Then, when the pulse position information means “left”, the gradation data correction unit 122 determines the halftone data (pulse width information and pulse position) related to the pixel on the left side of the pixel (immediately preceding pixel). Information) from the lotus information storage unit 212, on the other hand, when “right” is meant, halftone data (pulse width information and pulse position information) related to the pixel on the right side of the pixel (immediate pixel) Is acquired from the lotus information storage unit 212.

  For example, when the pixel to be processed is the pixel P2 shown in FIG. 10A, since the pulse width information = 25% and the pulse position information = “right”, the halftone data related to the immediately following pixel P3 is To be acquired. When the pixel to be processed is the pixel P9 shown in FIG. 10A, the pulse width information = 50% and the pulse position information = “left”, so that the halftone data relating to the immediately preceding pixel P8 is To be acquired.

  As described above, when the pixel to be processed is, for example, the pixel P2 shown in FIG. 10A, the adjacent pixel is the pixel P3, and the pulse width information of the halftone data related to the pixel P3 is 100%. . In this way, when the pulse width information of the halftone data relating to the adjacent pixel is 100%, the pixel to be processed is always continuous with the adjacent pixel. As for the count-up process concerned, the addition value when 100% is continuous is added to the current counter value of the counter 122a.

  Specifically, since the pulse width information of the halftone data related to the pixel P2 to be processed is 25% and the pulse width information of the halftone data related to the adjacent pixel P3 is 100%, the count-up process related to the pixel P2 is performed. Is added to the current counter value of the counter 122a by the addition value “+6” when 100% continues.

  Similarly, when the pixel to be processed is the pixel P7, the pulse width information of the halftone data related to the pixel P7 is 25%, and the pulse width information of the halftone data related to the pixel P6 adjacent on the left side is 100%. With respect to the count-up process related to the pixel P7, the addition value “+6” when 100% is continuous is added to the current counter value of the counter 122a.

  Therefore, when the addition value corresponding to the pulse width relating to each pixel from the second pixel P2 to the seventh pixel P7 is counted up, the value is “52”. Incidentally, when the added value corresponding to the pulse width related to each pixel is simply counted up (assuming that the laser pulse related to the pixel to be processed is isolated), the value is “44”.

  (C) Processing when the pulse width of the laser pulse related to the pixel to be processed is an intermediate width and the pulse width of the laser pulse related to the adjacent pixel is also an intermediate width will be described.

  The gradation data correction unit 122 means that when the pulse width of the laser pulse related to the adjacent pixel is an intermediate width, that is, the pulse width information of the halftone data related to the adjacent pixel has an intermediate width of 25% or 50%, for example. If it is, the light emission emitted corresponding to the processing target pixel based on the relationship between the pulse position information of the halftone data related to the processing target pixel and the pulse position information of the halftone data related to the adjacent pixel. It is determined whether the pulse (intermediate width light emission pulse) is in an isolated state or is continuously emitting light adjacent to an adjacent pixel, and based on the determination result, the current counter value of the counter 122a In addition, a predetermined addition value is added.

  For example, when the pixel to be processed is the pixel P8 of the eighth pixel, the pulse width information related to the pixel P8 means 50% and the intermediate width, and the ninth pixel as the adjacent pixel based on the pulse position information = left The pulse width information related to P9 is 50%, which means an intermediate width.

  The pixel P8 emits 50% of light from the “right” base point, while the pixel P9 emits 50% of light from the “left” base point. It turns out that it is the same state as 100% light emission corresponding to one pixel.

  In this case, the addition value at the time of the count-up process for the pixel P8 and the pixel P9 is set to a total value “+10”. For example, the added value corresponding to the pulse width related to the pixel P8 is “+5”, the added value corresponding to the pulse width related to the pixel P9 is “+5”, and the sum of these added values is “+10”.

  By the way, as can be seen from FIG. 10A, for example, in the case where the pixel of interest is the seventh pixel P7, the left side of the pixel P7 is continuous, so that continuous light emission occurs at the current pulse position (the pulse of the pixel P7). A period (time) in which the light is temporarily turned off at the position) occurs. In the case where the pixel of interest is the 10th pixel P10, the light emission is once turned off at the current pulse position (the position of the pulse with respect to the pixel P10), and then the light is continuously emitted.

  (Embodiment 3)

  Next, an image processing apparatus according to Embodiment 3 will be described.

  FIG. 11 shows a functional configuration of the image processing apparatus according to the third embodiment. This layer processing apparatus 200 has a configuration in which an image analysis unit 210 is added to the functional configuration of the image processing apparatus 100 shown in FIG. In FIG. 11, the same function is attached to a portion that performs the same function as the functional configuration shown in FIG. 1.

  The image analysis unit 210 includes a boundary information storage unit 211, receives gradation data GD2 (image data) after gradation correction, and a boundary portion (edge) between the high density region and the low density region in the gradation data GD2. , And edge boundary information ED indicating the boundary portion as the detection result is stored in the boundary information storage unit 211.

  In the third embodiment, detection means for detecting a boundary portion between a high density region and a low density region in image data is realized by the image analysis unit 210, for example.

  In the third embodiment, the image analysis unit 210 stores a program (software) for realizing the functions of the constituent elements in a memory such as a ROM (read only memory), and a CPU (central processing unit). ) Is realized by reading and executing the program from the memory. The program is included (embedded) in the predetermined program (image processing program) described in the first embodiment, and when the image processing program is executed by the CPU, gradation correction processing, droop correction processing, and edge detection are performed. Processing, halftone processing, etc. are performed.

  The boundary information storage unit 211 is realized by a RAM (Random Access Memory).

  Next, a boundary part (edge) detection process and a droop correction process by the image analysis unit 210 will be described.

  As shown in FIG. 12, the image analysis unit 210 relates to the gradation data GD2 with respect to an area (a plurality of pixels related to one line) corresponding to one scanning line in the laser scanning direction (X direction in FIG. 11). A boundary portion (edge) is detected by discriminating an edge and examining gradation data (pixel density value) of pixels on both sides in the laser scanning direction of the discriminated edge. As a result of this detection, for example, edge boundary information ED indicating the boundary portion (edge), for example, position information X1 (position from the origin (0, 0)) is obtained.

  In addition, the image analysis unit 210 performs the edge detection process as described above on the region corresponding to the plurality of scanning lines in the Y direction of FIG. 12 of the gradation data GD2 in the laser scanning direction.

  In the third embodiment, the image analysis unit 210 uses the detected edge as a reference, and position information indicating a position separated by a plurality of preset pixels, for example, in a direction toward the low density region (X direction). X2 (position from the origin (0, 0)) is also obtained.

  When the edge detection processing for the gradation data GD2 is completed, the image analysis unit 210 uses the position information X1, the position information X2, and the length YD in the Y direction as edge boundary information ED indicating the boundary portion. The edge boundary information ED is output to the gradation data correction unit 122 while being stored in the boundary information storage unit 211.

  In the third embodiment, in addition to the edge boundary information ED indicating the boundary portion (edge), for example, the position information X1, the position information X2 indicating the positions separated by a plurality of preset pixels is also stored. As shown in FIG. 12, it is included in a region (in this example, a rectangular region) formed by a line segment having a length XD (= X2-X1) in the X direction and a line segment having a length YD in the Y direction. The purpose is to perform the droop correction only on the gradation data.

  The gradation data correction unit 122 performs only the gradation data corresponding to the region based on the edge boundary information ED from the image analysis unit 210 with respect to the gradation data GD2 from the gradation correction unit 110. As in the case of the form 2, droop correction is performed. The gradation data GD4 after the droop correction is output to the halftone processing unit 130.

  In addition, the gradation data correction unit 122 performs the droop correction on the gradation data corresponding to the area other than the area based on the edge boundary information ED in the gradation data GD2 without performing the droop correction. Is output to the halftone processing unit 130 as gradation data GD4.

  In the third embodiment, the gradation data correction unit 122 performs strong correction (droop correction) in the vicinity of the edge on the gradation data in the region based on the edge boundary information ED in the gradation data GD2. On the other hand, weak correction (droop correction) may be performed as the distance from the edge increases (in the direction of the low density region).

  Next, an image forming system including an image forming apparatus having the image processing apparatus according to the first embodiment, the second embodiment, or the third embodiment will be described.

  FIG. 13 shows a configuration of an image forming system including an image forming apparatus having the image processing apparatus 100 according to the first embodiment or the second embodiment.

  As shown in FIG. 13, in the image forming system 1, a client device 20 such as a computer and a printer 20 as an image forming device are connected via a communication line 30.

  The client device 10 functions as a processing device, and includes a CPU (central processing unit) 11, a storage device 12 such as a hard disk, a memory 13 such as a RAM (optional read / write memory), and a communication interface (hereinafter “communication I / I”). F ”) 14.

  The storage device 12 stores various data such as application software for issuing a document generation or print request, a printer driver, and image data (print data).

  The memory 13 stores programs and data read from the storage device 12.

  The communication I / F 14 is an interface that transmits and receives data to and from the printer 20 via the communication line 30.

  The CPU 11 controls the entire client device 10. For example, the CPU 11 reads a printer driver from the storage device 12 into the memory 13 and executes it. As a result, the printer driver transmits image data (print data) to the printer 20.

  The printer 20 that functions as an image forming apparatus includes an image processing apparatus 100 and an output apparatus 25, and the image processing apparatus 100 includes a CPU 21, a storage device 22 such as a hard disk, a memory 23, a communication I / F 24, and a PWM unit 140. ing.

  The storage device 22 stores various programs and data necessary for executing print processing, such as the above-described image processing program 50 that is software.

  The communication I / F 24 is an interface that transmits and receives data to and from the client apparatus 10 via the communication line 30. For example, image data (print data) transmitted from the client apparatus 10 (the printer driver) is received. Receive.

  The memory 23 includes an image processing program 50 read from the storage device 22, a RAM that stores print information received via the communication I / F 24, a FIFO memory that functions as a pulse information storage unit 121, and an LUT 122 b. ROM for storing.

  In addition, the memory 23 is a storage area (work area or the like) required when the gradation correction process by the gradation correction unit 110 is performed, and a storage area required when the droop correction process by the droop correction unit 120 is performed. (A work area necessary for the calculation of the correction amount and the process of adding the obtained correction amount to the gradation data), a storage area (work area required for the halftone processing by the halftone processing unit 130) RAM) to which a storage area is allocated.

  The CPU 21 controls the entire printer 20. For example, by reading and executing the image processing program 50 from the storage device 22 into the memory 23, gradation correction processing and droop correction processing for image data (gradation data) are performed. The halftone process is performed, and the result of the halftone process (halftone data) is output to the PWM unit 140.

  The PWM unit 140 converts the received halftone data into a laser drive signal, and outputs the converted laser drive signal to the output device 25.

  The output device 25 is an image formation processing unit that performs image formation processing, and executes print processing based on received image data.

  The output device 25 includes a laser driving unit 25a and a semiconductor laser 25b as an exposure device that is a component of the image forming processing unit. The laser driver 25a causes the semiconductor laser 25b to emit laser light based on the laser drive signal from the PWM unit 140.

As the communication line 30, a local area network (LAN: Local
(Area Network), a wired communication line such as a telephone line, a wireless communication line such as a wireless LAN, and a combination of these communication lines.

  In the present specification, a computer that executes an image processing program includes a CPU, a memory, and a storage device such as an image processing apparatus of a printer shown in FIG.

  In the specification of the present application, a function of realizing each function of the image processing apparatus and recording a predetermined program (image processing program 50) including a program showing the processing procedure of the image processing in a storage device 22 such as a hard disk as a recording medium. Although described as a form, the predetermined program (image processing program) can be provided as follows.

  That is, the predetermined program may be stored in the ROM, and the CPU may load the program from the ROM to the main storage device and execute it.

  The predetermined program may be stored and distributed in a computer-readable recording medium such as a DVD-ROM, CD-ROM, MO (magneto-optical disk), flexible disk, or the like. In this case, after the image processing apparatus installs the program recorded on the recording medium, the CPU executes the program. As installation destinations of this program, there are memories such as RAM and storage devices such as a hard disk. Then, the image processing apparatus loads the program stored in the storage device into the main storage device and executes it as necessary.

  Further, the image processing apparatus is connected to a computer such as a server apparatus or a host computer via a communication line (for example, the Internet), and after the image processing apparatus downloads the predetermined program from the server apparatus or the computer, This program may be executed. In this case, the download destination of the program includes a memory such as a RAM and a storage device (recording medium) such as a hard disk. Then, the image processing apparatus loads the program stored in the storage device into the main storage device and executes it as necessary.

  The present invention can be applied to an image processing apparatus that performs a droop correction process on at least one of a monochrome image including a halftone image and a color image including a halftone image.

2 is a block diagram illustrating a functional configuration of the image processing apparatus according to Embodiment 1. FIG. 3 is a flowchart illustrating a processing procedure of image processing of the image processing apparatus according to the first embodiment. 6 is a diagram for describing image processing by the image processing apparatus according to Embodiment 1. FIG. 6 is a diagram for describing image processing by the image processing apparatus according to Embodiment 1. FIG. It is a figure explaining the laser width information and gradation data which concern on Embodiment 1. FIG. 6 is a diagram for describing droop correction processing by a droop correction unit of the image processing apparatus according to Embodiment 1. FIG. 10 is a flowchart illustrating a processing procedure of image processing of the image processing apparatus according to the second embodiment. 6 is a diagram for describing image processing by an image processing apparatus according to Embodiment 2. FIG. It is a figure explaining the light emission pattern based on laser width information among the laser width information and laser position information which concern on Embodiment 2. FIG. It is a figure explaining the light emission pattern based on the laser width information and laser position information which concern on Embodiment 2. FIG. 6 is a block diagram illustrating a functional configuration of an image processing apparatus according to Embodiment 3. FIG. FIG. 10 is a diagram for explaining a boundary portion detection process of an image analysis unit of an image processing apparatus according to a third embodiment. 1 is a configuration diagram showing a configuration of an image forming system including an image forming apparatus having an image processing apparatus according to Embodiment 1 or Embodiment 2. FIG.

Explanation of symbols

1 Image forming system 10 Client device (processing device)
20 Image forming device (printer)
21 Central processing unit (CPU)
22 storage device 23 memory 25 output device 25a laser driving unit 25b semiconductor laser 30 communication line 50 image processing program 100, 200 image processing device 110 gradation correction unit 120 droop correction unit 121 pulse information storage unit 122 gradation data correction unit 122a counter 122b Look-up table (LUT)
130 halftone processing unit 140 pulse width modulation (PWM) unit 210 image analysis unit 211 boundary information storage unit

Claims (6)

conversion means for converting pixel data of m (m is a positive integer) bit into pixel data of n (n is a positive integer, n <m) bits;
With respect to past pixels corresponding to a predetermined number of pixels related to pixel data to be converted by the conversion means with reference to the pixel immediately before the target pixel, the n-bit pixel data converted by the conversion means Corresponding storage means for storing pulse width information indicating the pulse width of the laser light emitted from the semiconductor laser;
Generating means for generating a correction value for the m-bit pixel data relating to the pixel of interest based on the storage content of the storage means;
Correction means for correcting the m-bit pixel data relating to the target pixel based on the correction value generated by the generation means;
Have
The converting means includes
Converting the m-bit pixel data relating to the pixel of interest after being corrected by the correction means into the n-bit pixel data;
An image processing apparatus. The storage means
With respect to past pixels corresponding to the predetermined number of pixels, an irradiation region corresponding to the pixel related to the pulse width information and a pulse emitted corresponding to the n-bit pixel data converted by the conversion means In association with the pulse position information indicating the position of the pulse that has been irradiated to ,
The image processing apparatus according to claim 1. The generating means includes
A counter that performs an operation of increasing or decreasing a counter value based on the pulse width information and the pulse position information of each past pixel corresponding to the predetermined number of pixels,
The counter is
Based on the pulse width information and the pulse position information of each pixel, it is determined whether or not the laser light emission is continuous corresponding to the continuous pixel, and the counter value is determined according to the determined result. Try to make the value to increase different,
Further, the generating means includes
Corresponding to the counter value as a result of the calculation when the calculation by the counter is executed for all the past pixels corresponding to the predetermined number of pixels, the m-bit pixel data related to the pixel of interest Generate correction values,
The image processing apparatus according to claim 2. The counter value as a result of the calculation and the correction value are in a proportional relationship.
The image processing apparatus according to claim 3. Detecting means for detecting a boundary portion between the high density region and the low density region in the image data;
The correction means includes
Correcting the m-bit pixel data related to the boundary portion detected by the detecting means based on the correction value generated by the generating means;
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. a conversion process for converting pixel data of m (m is a positive integer) bits into pixel data of n (n is a positive integer, n <m) bits;
The n-bit pixel converted by the conversion process with respect to past pixels corresponding to a predetermined number of pixels related to the pixel data to be converted by the conversion process with reference to the pixel immediately before the target pixel A storage process for storing pulse width information indicating a pulse width of a laser beam emitted from the semiconductor laser corresponding to the data;
A generation process for generating a correction value for the m-bit pixel data related to the pixel of interest based on the storage content stored in the storage process;
A correction process for correcting the m-bit pixel data related to the target pixel based on the correction value generated by the generation process;
Have
The conversion process includes:
Including a process of converting the m-bit pixel data related to the target pixel after being corrected by the correction process into the n-bit pixel data,
The conversion process, the storage process, the generation process, the correction process,
An image processing program for causing a computer to execute.