JP2004025554A - Image formation device and image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a cost reduction for products and to offset differences in an optical path length of two or more lasers in an image formation device with two or more lasers arranged in a vertical scanning direction to expose. <P>SOLUTION: A modulation circuit 62 receives image data for every pixel and generates a pulse width signal relative to image data of each pixel. A modulation control section 70 determines an optical beam projection time duration per pixel in accordance with positions on a photo conductor surface where optical beams are to be projected. An output circuit 63 outputs a PWM signal formed by the modulation circuit 62 for every pixel over the optical beam projection time duration of matched pixels decided by the modulation control section 70. An optical beam relative to the PWM signal of each pixel outputted by the output circuit 63 is generated, and scanned and projected onto the photo conductor surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus and an image reading apparatus, and in particular, to an image forming apparatus that forms an image by scanning and projecting a light beam from a predetermined position to a linear projection target based on image data, and an optical system. The present invention relates to an image reading apparatus that reads a document image sent to an image sensor through the image sensor for each pixel and outputs image data for each pixel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image forming apparatus (electrophotographic apparatus) that performs image exposure using laser light irradiates a rotating polyhedron (polygon) with laser light and exposes the surface of a photoreceptor with reflected light. At this time, it is desirable that the distance from the laser light emission source to the surface of the photoreceptor be equal regardless of the rotation position of the polygon. Therefore, the shape of the photoconductor is desirably an arc shape centered on the polygon reflection position. However, the photoconductor of many image forming apparatuses adopts a cylindrical shape. The problem caused by the nonuniformity of the optical path length from the laser source to the surface of the photoreceptor due to the shape of the photoreceptor is that the size of the pixel is reduced by using a complex optical means called an f-θ lens. The problem has been solved by performing processing so as to be uniform at any position in the axial direction of the photoconductor.
[0003]
In recent years, with the speeding up of image formation, an image forming apparatus that exposes a plurality of lasers in the sub-scanning direction has been developed. Of course, even in the image forming apparatus using a plurality of lasers, as described above, it is necessary to equalize the optical path length from the laser source to the surface of the photosensitive member in the main scanning direction. At the same time, the optical path lengths between the laser light sources and the photoconductors arranged in the sub-scanning direction must be equal to each other. However, even if there is a slight difference in each optical path length between each laser light source and the photoconductor, the difference is a problem as long as the optical and mechanical accuracy in other parts of the image forming apparatus is low. Was not apparent.
[0004]
In addition to the image forming apparatus, in an image reading apparatus using a CCD (imaging device), optical and mechanical adjustment of the CCD unit is once performed in order to accurately adjust the optical path length between the document surface and the CCD device. Thereafter, readjustment was performed using a jig to determine the positional relationship between the lens and the CCD element.
[0005]
[Problems to be solved by the invention]
However, the image forming apparatus using the above-mentioned conventional f-θ lens requires a high degree of accuracy in manufacturing the f-θ lens, and thus has a problem that it cannot cope with the recent cost reduction of products.
[0006]
Further, in the above-described conventional image forming apparatus that exposes a plurality of lasers in the sub-scanning direction, the optical and mechanical accuracy of each part of the image forming apparatus is improved with the increase in resolution, and as a result, However, the difference between the optical path lengths of a plurality of lasers, which has been conventionally allowed, affects an output image, and the difference in the optical path lengths cannot be ignored.
[0007]
As a technique for solving these problems, there is a technique disclosed in JP-A-2000-238342. However, according to the technique disclosed in Japanese Patent Application Laid-Open No. 2000-238342, the image stream (flow of image data) is only locally increased or shortened, so that the maximum emission time of one pixel is fixed. In some cases, a space is generated or a pixel piece is missing, and depending on the image, an image not intended by the user (for example, a white line appears when a solid image is output, or a thin line disappears). turn into.
[0008]
In the conventional image reading apparatus using a CCD, the optical / mechanical adjustment of the CCD unit is performed in two stages of coarse adjustment and fine adjustment, and the adjustment cannot be simplified. There was a problem.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and it is possible to reduce the cost of a product, and furthermore, an optical path of a plurality of lasers in an image forming apparatus that exposes a plurality of lasers in the sub-scanning direction. A first object is to provide an image forming apparatus in which the difference in length is eliminated.
[0010]
It is a second object of the present invention to provide an image reading apparatus which simplifies adjustment in a manufacturing process.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an image forming apparatus that forms an image by scanning and projecting a light beam from a predetermined position to a linearly projected portion based on image data. Receiving means for receiving image data for each pixel, maximum light emitting time determining means for determining a maximum light emitting time per pixel according to the position of the projection target to which a light beam is to be projected, and the receiving means Pulse width modulation beam generation means for generating a light beam pulse having a predetermined light emission duty in accordance with the received image data of each pixel, and for each pixel, the light beam pulse generated by the pulse width modulation beam generation means An image forming apparatus comprising: a projection unit configured to scan and project onto the projection target portion.
[0012]
According to the sixth aspect of the present invention, in an image forming apparatus that forms an image by scanning and projecting a light beam from a predetermined position to a linearly projected portion based on the image data, the image data for each pixel is received. Receiving means, a cycle determining means for determining a cycle per pixel according to the position of the projection target to which the light beam is to be projected, a cycle determined by the cycle determining means, Modulation pulse generation means for generating a predetermined light emission duty according to the image data of each pixel, and output means for outputting a light beam according to a predetermined light emission duty generated by the modulation pulse generation means for each pixel, An image forming apparatus having projection means for scanning and projecting the light beam onto the projection target portion.
[0013]
According to the invention described in claim 8, based on the image data, a plurality of different lines are formed on a plurality of straight lines extending in the axial direction and separated from each other in the rotation direction on the surface of the rotating cylindrical body from the predetermined position. In an image forming apparatus that forms an image by simultaneously scanning and projecting a plurality of light beams related to pixels, a receiving unit that receives image data for each pixel, and the cylinder to which one of the plurality of light beams is to be projected Maximum light emission time determining means for determining the maximum light emission time of the light beam per pixel according to the position of the body; and image data of each pixel received by the receiving means and the maximum light emission time determined by the maximum light emission time determining means. First generating means for generating at least one light beam according to a light emitting time, and at least one generating means according to image data of each pixel received by the receiving means Image forming apparatus is provided, characterized in that it comprises a second generating means for generating a light beam.
[0014]
According to the twelfth aspect of the present invention, based on image data, a plurality of different pixels are provided on a plurality of straight lines extending in the axial direction and separated from each other in the rotational direction on the surface of the rotating cylindrical body from a predetermined position. In an image forming apparatus for forming an image by simultaneously scanning and projecting a plurality of light beams concerned, a receiving means for receiving image data for each pixel, and a cylindrical member to which one of the plurality of light beams is to be projected A period determining unit that determines a period per pixel according to the position; a period determined by the period determining unit; and a predetermined light emission duty is generated according to the image data of each pixel received by the receiving unit. First modulation pulse generation means, second modulation pulse generation means for generating a predetermined light emission duty according to image data of each pixel received by the reception means, Output means for outputting a light beam according to the light emission duty generated by the first and second modulation pulse generating means for each element; and projecting means for projecting the light beam output by the output means onto the cylindrical body. An image forming apparatus having:
[0015]
According to the fourteenth aspect of the present invention, in the image reading apparatus, the original image sent to the imaging device via the optical system is read by the imaging device for each pixel, and image data for each pixel is output. Cycle determining means for determining the cycle of each pixel by the element, and output means for reading the original image sent to the image sensor for each pixel at the cycle determined by the cycle determining means and outputting image data. An image reading device is provided.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
(First Embodiment)
FIG. 1 is a vertical sectional view showing the entire configuration of the first embodiment of the image forming apparatus according to the present invention.
[0018]
The basic operation of the image forming apparatus will be described with reference to FIG.
[0019]
Documents stacked on the document feeder 1 are sequentially conveyed one by one onto the platen glass 2 surface. When the document is conveyed, the lamp 3 in the scanner section is turned on, and the scanner unit 4 moves to irradiate the document. The reflected light of the original is input to the image sensor unit 9 via the mirrors 5, 6, 7 and the lens unit 8. As a result, the image signal output from the image sensor unit 9 is directly or temporarily stored in an image memory (not shown), read out again, and input to the exposure control unit 10.
[0020]
The exposure control unit 10 generates a laser beam based on an image signal, and a latent image is formed on the photoconductor 11 by the irradiation light. The latent image is developed by the developing device 13 as a toner image. The transfer member is conveyed from the transfer member stacking section 14 or the transfer member stacking section 15 in synchronization with the formation of the latent image, and the developed toner image is transferred in the transfer section 16. After the transferred toner image is fixed on the transfer member by the fixing unit 17, the toner image is discharged to the outside of the apparatus from the paper discharge unit 18. The cleaner 25 cleans the surface of the photoconductor 11 after the transfer. The surface of the photoconductor 11 cleaned by the cleaner 25 is neutralized by the auxiliary charger 26 so that the primary charger 28 can obtain good charge. Thereafter, the residual charge on the photoconductor 11 is erased by the pre-exposure lamp 27, and the primary charger 28 charges the surface of the photoconductor 11.
[0021]
These steps are repeated to form a plurality of images.
[0022]
FIG. 2 is a horizontal plan view showing the internal configuration of the exposure control unit 10.
[0023]
In FIG. 2, reference numeral 31 denotes a laser driving device, and reference numeral 43 denotes a semiconductor laser. A photodiode sensor (hereinafter, referred to as a “PD sensor”) for detecting a part of the laser light is provided inside the semiconductor laser 43. As described later, an APC (Auto) of the laser diode is used by using a detection signal of the PD sensor. Power Control is performed.
[0024]
The laser beam emitted from the semiconductor laser 43 becomes almost parallel light by the collimator lens 35 and the stop 32, and is incident on the rotating polygon mirror (polygon) 33 with a predetermined beam diameter. The rotating polygon mirror 33 rotates at a constant angular velocity in a direction indicated by an arrow in the figure. With this rotation, the incident light beam becomes a deflection beam that continuously changes its angle, is reflected from the rotating polygon mirror 33, and is sent to the surface of the photosensitive member 11. Reference numeral 36 denotes a beam detect sensor (hereinafter, referred to as a “BD sensor”) that detects reflected light from the rotating polygon mirror 33. The detection signal from the BD sensor 36 is used as a synchronization signal for synchronizing the rotation of the rotary polygon mirror 33 and the writing of data.
[0025]
The APC control performed by the laser driving device 31 will be specifically described with reference to FIG.
[0026]
FIG. 3 is a circuit diagram of a laser drive circuit in the laser drive device 31.
[0027]
The laser drive circuit uses a laser chip 43. The laser chip 43 includes one laser 43A and one PD sensor 43B. In this laser drive circuit, the light emission characteristics of the laser 43A are improved by applying two current sources, a bias current source 41 and a pulse current source 42, to the laser 43A. Further, the laser driving device 31 performs feedback control on the bias current source 41 using an output signal from the PD sensor 43B in order to stabilize the light emission of the laser 43A, and performs automatic control of the bias current amount.
[0028]
That is, when the sequence controller 47 outputs the full lighting signal to the OR logic element 40, the OR logic element 40 outputs an ON signal to the switch 49, whereby the sum of the currents from the bias current source 41 and the pulse current source 42 is obtained. Flows to the laser 43A. The light emission amount of the laser 43A at that time is detected by the PD sensor 43B, and the output signal from the PD sensor 43B is input to the current / voltage converter 44, then amplified by the amplifier 45, and controlled by the bias current source 41 via the APC circuit 46. Supplied as a signal. As a result, feedback control is performed so that the light emission amount of the laser 43A becomes constant. This circuit system is called an APC circuit system, and is currently common as a circuit system for driving a laser.
[0029]
That is, a laser generally has temperature characteristics, and the higher the temperature, the greater the amount of drive current to obtain the same amount of light. Further, since the laser self-heats, a constant amount of light cannot be obtained only by supplying a constant amount of current, and such a change in light amount has a significant effect on image formation. In order to solve this, the amount of drive current is controlled using the above-described APC circuit method so that the amount of laser emission is constant.
[0030]
Note that a digital image signal is input to the modulation unit 48, PWM (Pulse Width Modulation) modulation is performed, and the obtained PWM signal is sent to the switch 49 via the OR logic element 40. The switch 49 is closed only during the ON period of the PWM signal. As a result, the generation time of the laser beam controlled to the above-mentioned constant light amount is controlled, and as a result, an image is formed according to the image signal.
[0031]
FIG. 4 is a block diagram showing the internal configuration of the modulation unit 48.
[0032]
In FIG. 4, reference numeral 60 denotes a PLL circuit, which outputs an n-fold high frequency clock by inputting a basic clock. This high frequency clock is input to the frequency dividing circuit 61 and the output circuit 63, respectively. The frequency dividing circuit 61 is composed of a counter that outputs a clock once every time a high-frequency clock is input x times, and performs (1 / x) frequency dividing. The division ratio x may be any number as long as it is an integer, but here, for convenience of explanation, it is assumed that x = n. Therefore, the frequency dividing circuit 61 divides the frequency by (1 / n) and outputs a clock (main clock) having the same cycle as the basic clock input to the PLL circuit 60.
[0033]
FIG. 5 is a timing chart showing the relationship between the high frequency clock (A) input to the frequency dividing circuit 61 and the main clock (B) output from the frequency dividing circuit 61.
[0034]
Returning to FIG. 4, the main clock output from the frequency dividing circuit 61 is input to the counter circuit 64.
[0035]
The modulation circuit 62 performs digital PWM modulation based on the input digital image data (image signal) for each pixel, generates a PWM signal having a duty ratio corresponding to the density of each pixel, and outputs the PWM signal to the output circuit 63. I do. For example, if the input image data is composed of A bits, ^A Are set in advance, and 2 ^A From among the duty ratios, a duty ratio corresponding to the input image data is selected for each pixel, and a pulse signal having the selected duty ratio and having the same cycle as the high-frequency clock is generated for each pixel.
[0036]
FIG. 6 shows that the modulation circuit 62 synchronizes the image data (B) for each pixel input from the image processing circuit (not shown) in synchronization with the correction clock signal (A) and the correction clock signal (A). 6 is a timing chart showing a relationship with a PWM signal (C) output from a modulation circuit 62. The correction clock signal is a signal sent from the output circuit 63, which will be described later.
[0037]
Returning to FIG. 4, the output circuit 63 continues to output the PWM signal transmitted from the modulation circuit 62 to the OR logic circuit 40 (FIG. 3) for a predetermined period during which a predetermined number of high-frequency clocks are output from the PLL circuit 60. Further, the correction clock signal having the predetermined period as a cycle is output to the modulation circuit 62 and an image processing unit (not shown) which outputs input image data. Note that the predetermined number (predetermined period) is determined according to an output signal from the counter circuit 64. As will be described later in detail, this value changes according to the position in the axial direction of the photoconductor 11 where the laser beam is irradiated.
[0038]
FIG. 7 is a timing chart showing the PWM signal and the correction clock signal output from the output circuit 63.
[0039]
That is, the counter circuit 64 counts the main clock output from the frequency dividing circuit 61. At this time, when the count value (FIG. 7B) reaches a predetermined count number (for example, 1000), an output signal (FIG. 7C) is transmitted to the output circuit 63.
[0040]
When receiving the output signal from the counter circuit 64, the output circuit 63 performs an operation different from the normal operation. Normally, a PWM signal corresponding to each predetermined period is output only during the predetermined period (FIG. 7 (FIG. 7 (A)), where one period is a predetermined period (the period of the main clock (FIG. 7A)) in which n high-frequency clocks are input. D)), and outputs a correction clock signal (FIG. 7 (E)) having a period equal to the predetermined period. On the other hand, when the output signal is received from the counter circuit 64, the PWM signal (indicated by “10” in FIG. 7D) is output over a predetermined correction period different from the predetermined period, and A corrected clock signal (FIG. 7E) having a cycle of the same length is output.
[0041]
Next, a specific configuration of the output circuit 63 will be described. Prior to that, the function of the conventionally used f-θ lens will be described below.
[0042]
Conventionally, an f-θ lens is provided between a rotating polygonal mirror (polygon) and a photoconductor, and has a distortion aberration such as to guarantee the temporal linearity of scanning with respect to a deflection beam from the rotating polygonal mirror. Make corrections. As a result, the light beam scans the cylindrical photoconductor at a constant speed in the axial direction.
[0043]
FIG. 8 is a diagram illustrating the scanning speed of the laser beam on the surface of the photoconductor 11 when the f-θ lens does not exist. FIG. 9 is a diagram illustrating a scanning speed of laser light on the surface of the photoconductor 11 when the f-θ lens 34 is present.
[0044]
First, the case where the f-θ lens 34 does not exist will be described.
[0045]
Since the rotating polygon mirror (polygon) 33 rotates at a constant angular velocity, the scanning speed is constant on an arc of the same radius (R1 to R5) centered on the laser light reflection point on the surface of the polygon 33. θa, θb, θc, and θd are rotation angles per unit time (θa = θb = θc = θd).
[0046]
At this time, when the scanning distances within the respective rotation angles (θa, θb, θc, θd) of the laser beam moving in the axial direction on the cylindrical photoconductor 11 are Xa, Xb, Xc, and Xd,
Xa> Xb
Xd> Xc
It becomes the relationship. From this result, it can be seen that the scanning speed of the laser beam moving in the axial direction on the photoconductor 11 becomes “large” as it approaches the axial end of the photoconductor 11 and “small” as it approaches the center. . Therefore, the size of the pixel in the latent image created on the photoconductor 11 by the scanning of the laser beam differs between the axial end portion and the central portion of the photoconductor 11. In other words, the size of the pixel increases from the center to the end.
[0047]
Therefore, an f-θ lens 34 for correcting distortion is provided between the rotating polygon mirror (polygon) 33 and the photoconductor 11. by this,
Xa = Xb = Xc = Xd
Is realized, and the size of the pixel in the latent image created on the photoconductor 11 is uniform at any position in the axial direction of the photoconductor 11.
[0048]
In the first embodiment, the output circuit 63 changes the output time of the PWM signal for each pixel in accordance with the axial position of the photoconductor 11 without using the f-θ lens 34. That is, the output time is made longer at the central portion of the photoconductor 11 in the axial direction, and shorter at the end.
As a result, the pixel size is made uniform at any position in the axial direction of the photoconductor 11. This will be described below.
[0049]
FIG. 10 is a circuit block diagram showing the internal configuration of the output circuit 63 and the modulation circuit 62.
[0050]
Image data for one pixel is input from an image processing circuit (not shown) to the modulation circuit 62 in synchronization with the correction clock signal. The modulation circuit 62 has the same cycle as the high frequency clock. The modulation circuit 62 outputs a pulse having a duty ratio corresponding to the input image data as a PWM signal during one period of the correction clock signal to each of one input terminals of the two-input AND circuits 72-1 to 72-10 of the output circuit 63. Output to
[0051]
Reference numerals 71-1 to 71-10 denote D-type flip-flops, which output a signal input to the D terminal to the Q terminal when a high-frequency clock input to the C terminal from the PLL circuit 60 rises. The output signal of each Q terminal is input to the other input terminals of the two-input AND circuits 72-1 to 72-10. At the same time, output signals from the Q terminals of the flip-flops 71-1 to 71-7 are input to the D terminals of the flip-flops 71-2 to 71-8. The output signal from the Q terminal of the flip-flop 71-8 is input to the three-input selector circuit 73 and the two-input selector circuit 74. The output signal from the Q terminal of the flip-flop 71-9 is input to the three-input selector circuit 73 and the two-input selector circuit 75, respectively. The output signal from the Q terminal of the flip-flop 71-10 is input to the three-input selector circuit 73.
[0052]
Each output terminal of the 2-input AND circuits 72-1 to 72-10 is connected to a 10-input OR circuit 76.
[0053]
The three-input selector circuit 73 selects one of the flip-flops 71-8, 71-9, and 71-10 according to the output signal of the modulation control unit 70, and selects one input terminal of the two-input OR circuit 77. Output to
[0054]
The other input terminals of the two-input selector circuits 74 and 75 are grounded. In response to the output signal from the modulation control unit 70, the two-input selector circuit 74 controls whether or not to input the output signal from the flip-flop 71-8 to the D terminal of the flip-flop 71-9. The two-input selector circuit 75 controls whether to output an output signal from the flip-flop 71-9 to the D terminal of the flip-flop 71-10.
[0055]
The modulation control unit 70 determines which position in the axial direction of the photoconductor 11 is irradiated with the laser beam based on the output signal of the counter circuit 74, and based on the determination result, selects the selector circuit 73. To 75 each determine an input signal to be selected.
Specifically, as shown in FIG. 11, an effective area R0 where a latent image can be generated on the photoconductor 11 is formed along the axial direction of the photoconductor 11 by, for example, one central area R3 and two end areas R1. , R5, and two intermediate areas R2, R4 located between the center area and the end area. Then, the counter circuit 64 sets each main clock number corresponding to the boundary position of each area as the predetermined count number. Based on the output signal of the counter circuit 64 (FIG. 11C) and the output signal of the BD sensor 36 (FIG. 11B), the modulation control unit 70 It is determined whether or not a laser beam is applied, and the selector circuits 73 to 75 determine input signals to be selected, as described later.
[0056]
A non-periodic timing signal having the same width as the pulse width of the high-frequency clock output from the PLL circuit 60 is input to the other input terminal of the two-input OR circuit 77 at startup, and the output signal of the two-input OR circuit 77 is output. Is sent to the D terminal of the flip-flop 71-1.
[0057]
Next, the operation of the output circuit 63 will be described with reference to FIG.
[0058]
Since the flip-flops 71-1 to 71-10 form a ring-shaped shift register, the timing signal is input to the D terminal of the flip-flop 71-1. Each Q terminal of -1 to 71-10 sequentially becomes high level (signal "1"). Therefore, the output signal is always “1” at any one Q terminal of the flip-flops 71-1 to 71-10.
[0059]
The modulation control unit 70 receives the output signal from the counter circuit 64, determines the length of the annular shift register, and operates the selector circuits 73 to 75 accordingly. That is, when the end areas R1 and R5 of the five areas of the photoconductor 11 are irradiated with the laser beam, the selector circuit 73 is caused to select the output signal of the flip-flop 71-8 and the selector circuits 74 and 75 are selected. Causes GND (ground) to be selected. Therefore, the ring-shaped shift register is constituted by flip-flops 71-1 to 71-8, and becomes a shift register that makes a cycle by inputting a high-frequency clock eight times. Thus, every time the high-frequency clock is input, the signal “1” is sequentially sent to each input terminal of the two-input AND circuits 72-1 to 72-8. At the same time, the modulation control unit 70 generates a correction clock signal whose period is a predetermined period in which the high-frequency clock is input eight times, and sends it to the modulation circuit 62.
[0060]
When the laser beam is applied to the intermediate areas R2 and R4 of the five areas of the photoconductor 11, the selector circuit 73 selects the output signal of the flip-flop 71-9, and the selector circuit 74 selects the output signal of the flip-flop. The output signal of 71-8 is selected, and the selector circuit 75 selects GND. Therefore, the ring-shaped shift register is constituted by flip-flops 71-1 to 71-9, and becomes a shift register that makes one cycle by inputting a high-frequency clock nine times. As a result, every time a high-frequency clock is input, the signal “1” is sequentially sent to each input terminal of the two-input AND circuits 72-1 to 72-9. At the same time, the modulation control unit 70 generates a correction clock signal having a period of a predetermined period in which the high frequency clock is input nine times and sends the correction clock signal to the modulation circuit 62.
[0061]
Further, when the central area R3 of the five areas of the photosensitive member 11 is irradiated with the laser beam, the selector circuit 73 selects the output signal of the flip-flop 71-10, and the selector circuit 74 selects the output signal of the flip-flop 71-. 8 and the selector circuit 75 selects the output signal of the flip-flop 71-9. Therefore, the ring-shaped shift register is constituted by flip-flops 71-1 to 71-10, and becomes a shift register that makes a full cycle by inputting a high-frequency clock ten times. Thus, every time the high-frequency clock is input, the signal “1” is sequentially sent to the input terminals of the two-input AND circuits 72-1 to 72-10. At the same time, the modulation control unit 70 generates a correction clock signal having a period of a predetermined period in which the high-frequency clock is input ten times and sends it to the modulation circuit 62.
[0062]
The PWM signal is input to one input terminal of each of the two-input AND circuits 72-1 to 72-10, and the signal "1" is input to the other input terminal of each of the two-input AND circuits 72-1 to 72-10. Is sent, the PWM signal is output to the 10-input OR circuit 76. That is, when the laser beam is applied to the end areas R1 and R5 of the photoconductor 11, the PWM signal based on the image data of the same pixel is output to the 10-input OR circuit 76 while the high frequency clock is input eight times. After the high frequency clock is input eight times, the modulation circuit 62 that has received the correction clock signal sends a PWM signal based on image data of a new pixel to the output circuit 63.
[0063]
When the intermediate area R2, R4 of the photoconductor 11 is irradiated with the laser beam, the PWM signal based on the image data of the same pixel is output to the 10-input OR circuit 76 while the high frequency clock is input nine times. Similarly, after the high frequency clock is input nine times, the modulation circuit 62 that has received the correction clock signal sends a PWM signal based on image data of a new pixel to the output circuit 63.
[0064]
Further, when the central area R3 of the photoconductor 11 is irradiated with a laser beam, a PWM signal based on image data of the same pixel is output to the 10-input OR circuit 76 while the high frequency clock is input 10 times. Similarly, after the high frequency clock is input ten times, the modulation circuit 62 that has received the correction clock signal sends a PWM signal based on image data of a new pixel to the output circuit 63.
[0065]
As shown in FIG. 8, the image area for one pixel is wide in the end areas R1 and R5 of the photoconductor 11, and the image area for one pixel is narrow in the center area R3 of the photoconductor 11. . However, as described above, in the end areas R1 and R5 of the photoconductor 11, irradiation of laser light for one pixel is performed over a period in which a high-frequency clock is input eight times. In the intermediate areas R2 and R4 of the photoconductor 11, irradiation of laser light for one pixel is performed over a period in which a high-frequency clock is input nine times. In the central area R3 of the photoconductor 11, irradiation of laser light for one pixel is performed over a period in which a high-frequency clock is input ten times. In this manner, the image area of one pixel can be made substantially equal at any position in the axial direction of the photoconductor 11.
[0066]
Accordingly, an image area of one pixel having the same size can be realized at any position in the axial direction of the photoconductor 11 without using the f-θ lens.
[0067]
In the first embodiment, each boundary position of the five areas R1 to R5 is determined by the predetermined count set in the counter circuit 64, but is determined by another means such as a timer. You may do so.
[0068]
Further, the number of areas constituting the effective area R0 shown in FIG. 11 may be another number.
[0069]
Further, in the first embodiment, the irradiation of the laser light for one pixel is performed during a period in which the high frequency clock is input 8 to 10 times, but may be another number. In that case, the length of the annular shift register is set according to the number of times.
[0070]
(Second embodiment)
In the second embodiment, a case where the present invention is applied to an image forming apparatus provided with a plurality of lasers will be described. It is assumed that the image forming apparatus according to the second embodiment includes an f-θ lens.
[0071]
Prior to the description of the second embodiment, first, a conventional problem in an image forming apparatus having a plurality of lasers will be described with reference to FIGS.
[0072]
FIG. 12 is a side view showing the photoconductor 11A and the rotating polyhedron 33A in the image forming apparatus provided with two lasers. Although this image forming apparatus is provided with an f-θ lens, its illustration is omitted in FIG.
[0073]
Two lasers (not shown) are arranged slightly apart in the sub-scanning direction and output from the two lasers. The two laser beams L1 and L2 reflected by the rotating polyhedron 33A irradiate the photoconductor 11A slightly away in the sub-scanning direction (the rotation direction of the photoconductor 11A).
[0074]
FIG. 13 is a side view corresponding to FIG. 12 in which the interval between the two laser beams L1 and L2 is extremely large for easy understanding.
[0075]
When the optical path length of the laser beam L1 from the rotating polyhedron 33A to the surface of the photoconductor 11A is La, and when the optical path length of the laser beam L2 from the rotating polyhedron 33A to the surface of the photoconductor 11A is Lb, as can be seen from FIG. , There is a difference ΔL (= Lb−La) in the optical path lengths La and Lb.
[0076]
FIG. 14 is a plan view of the image forming apparatus shown in FIG. 13 as viewed from below. However, in FIG. 14, the f-θ lens 34A is illustrated.
[0077]
In the figure, Xa is a main scanning width of the laser beam L1 on the surface of the photoconductor 11A, and Xb is a main scanning width of the laser beam L2 on the surface of the photoconductor 11A. Since there is an optical path length difference ΔL, these main scanning widths have the following relationship.
[0078]
Xb> Xa
When the laser beams L1 and L2 form adjacent line images in the sub-scanning direction of a latent image generated on the surface of the photoconductor 11A, the image quality is degraded due to the above relationship.
[0079]
In the second embodiment, a decrease in image quality in an image forming apparatus having such a plurality of lasers is prevented. Basically, in the process of generating a latent image in the main scanning direction by the laser beam L1, the length of one pixel in the main scanning direction at a plurality of predetermined positions in the main scanning width is slightly increased. Thus, Xb = Xa is finally set.
[0080]
The configuration of the second embodiment is basically the same as the configuration of the first embodiment. In the description of the second embodiment, the configuration of the first embodiment will be used, and only different parts will be described.
[0081]
FIG. 15 is a circuit block diagram illustrating the internal configuration of the output circuit 63A and the modulation circuit 62 according to the second embodiment. The output circuit 63A and the modulation circuit 62 are for controlling a laser beam corresponding to the laser beam L1 shown in FIG. The output circuit and the modulation circuit for controlling the laser beam corresponding to the laser beam L2 may be of a conventional type.
[0082]
Image data for one pixel from an image processing circuit (not shown) is input to the modulation circuit 62 in synchronization with the correction clock signal. The modulation circuit 62 outputs a pulse having the same cycle as the high-frequency clock and having a duty ratio according to the input image data as a PWM signal during one cycle of the correction clock signal to the two-input AND circuits 82-1 to 82-1 of the output circuit 63A. It outputs to each one input terminal of 82-9.
[0083]
Reference numerals 81-1 to 81-9 denote D-type flip-flops, each of which outputs a signal input to the D terminal to the Q terminal when a high-frequency clock input to the C terminal from the PLL circuit 60 (FIG. 4) rises. . The output signal of each Q terminal is input to the other input terminal of the two-input AND circuits 82-1 to 82-9. At the same time, output signals from the Q terminals of the flip-flops 81-1 to 81-7 are input to the D terminals of the flip-flops 81-2 to 81-8, respectively. The output signal from the Q terminal of the flip-flop 81-8 is input to the two-input selector circuit 83 and the two-input selector circuit 84, respectively. The output signal from the Q terminal of the flip-flop 81-9 is input to the two-input selector circuit 83.
[0084]
Each output terminal of the two-input AND circuits 82-1 to 82-9 is connected to a nine-input OR circuit 86.
[0085]
The two-input selector circuit 83 selects one of the flip-flops 81-8 and 81-9 according to the output signal of the modulation control unit 80, and outputs it to one input terminal of the two-input OR circuit 87.
[0086]
The other input terminal of the two-input selector circuit 84 is grounded. The two-input selector circuit 84 controls whether the output signal from the flip-flop 81-8 is input to the D terminal of the flip-flop 81-9 according to the output signal from the modulation control unit 80.
[0087]
The modulation control unit 80 controls the operations of the selector circuits 83 and 84 based on the output signal from the counter circuit 64 (FIG. 4). Specifically, as shown in FIG. 16, an image effective area (FIG. 16A) in which a latent image can be generated on the photoconductor 11 is uniformly divided along the axial direction of the photoconductor 11, for example, into five areas. Divided into Then, the number of main clocks corresponding to the boundary position of each area is set as the predetermined count set in the counter circuit 64. The modulation control unit 80 causes the selector circuits 83 and 84 to make different selections depending on whether or not an output signal from the counter circuit 64 has been received. Details will be described later.
[0088]
A non-periodic timing signal having the same width as the pulse width of the high-frequency clock output from the PLL circuit 60 is input to the other input terminal of the two-input OR circuit 87 at the time of startup. The output signal of the two-input OR circuit 87 is sent to the D terminal of the flip-flop 81-1.
[0089]
Next, the operation of the output circuit 63A will be described with reference to FIG.
[0090]
The flip-flops 81-1 to 81-9 form a circular shift register. Therefore, the above-mentioned timing signal is input to the D terminal of the flip-flop 81-1 so that the Q terminal of each of the flip-flops 81-1 to 81-9 sequentially becomes high level (signal " 1 "). Therefore, the output signal is always “1” at any one Q terminal of the flip-flops 81-1 to 81-9.
[0091]
The modulation control unit 80 determines the length of the ring-shaped shift register according to whether or not the output signal from the counter circuit 64 is received, and operates the selector circuits 83 and 84 accordingly. That is, when the output signal is not received from the counter circuit 64, the selector circuit 83 is caused to select the output signal of the flip-flop 81-8. The selector circuit 84 selects GND (ground). Therefore, the ring-shaped shift register is constituted by flip-flops 81-1 to 81-8, and becomes a shift register that makes a cycle by inputting a high-frequency clock eight times. As a result, every time the high-frequency clock is input, the signal “1” is sequentially sent to the input terminals of the two-input AND circuits 82-1 to 82-8. At the same time, the modulation control unit 80 generates a correction clock signal having a period of a predetermined period in which the high-frequency clock is input eight times and sends it to the modulation circuit 62.
[0092]
When receiving the output signal from the counter circuit 64, the selector circuit 83 selects the output signal of the flip-flop 81-9. The selector circuit 84 selects the output signal of the flip-flop 81-8. Therefore, the ring-shaped shift register is constituted by flip-flops 81-1 to 81-9, and becomes a shift register that makes one cycle by inputting a high-frequency clock nine times. As a result, every time the high frequency clock is input, the signal “1” is sequentially sent to the input terminals of the two-input AND circuits 82-1 to 82-9. At the same time, the modulation control unit 80 generates a correction clock signal having a cycle of a predetermined period in which the high frequency clock is input nine times, and sends the correction clock signal to the modulation circuit 62.
[0093]
The PWM signal is input to one input terminal of each of the two-input AND circuits 82-1 to 82-9, and the signal "1" is input to the other input terminal of each of the two-input AND circuits 82-1 to 82-9. The PWM signal is sent to the 9-input OR circuit 86 to output the PWM signal. That is, when the output signal is not received from the counter circuit 64, the PWM signal based on the image data of the same pixel is output to the 9-input OR circuit 86 while the high frequency clock is input eight times. After the high frequency clock is input eight times, the modulation circuit 62 that has received the correction clock signal sends a PWM signal based on image data of a new pixel to the output circuit 63.
[0094]
When the output signal is received from the counter circuit 64, the PWM signal based on the image data of the same pixel is output to the nine-input OR circuit 86 while the high frequency clock is input nine times. Similarly, after the high frequency clock is input nine times, the modulation circuit 62 that has received the correction clock signal sends a PWM signal based on image data of a new pixel to the output circuit 63.
[0095]
As shown in FIG. 14, the main scanning width Xa of the laser beam L1 on the photoconductor 11A is slightly smaller than the main scanning width Xb of the laser beam L2 in the second embodiment. In the main scanning of the laser beam corresponding to the laser beam L1, the size of one pixel is slightly increased. The number of pixels whose size is increased and the amount of increase are set so that Xa = Xb. The positions of the pixels whose size is to be increased are set at equal intervals in the image effective area.
[0096]
Thereby, even if the two laser beams are arranged apart from each other in the sub-scanning direction, the difference in the main scanning width between them is eliminated.
[0097]
Even when two or more laser beams are arranged apart from each other in the sub-scanning direction, the main amount related to all the laser beams can be set by appropriately setting the amount of increase in the pixel size and the number of pixels to be increased. The scanning width can be the same.
[0098]
In the second embodiment, each boundary position of the five areas is determined by the predetermined count set in the counter circuit 64, but may be determined by another means, for example, a timer means. Is also good.
[0099]
Further, in the second embodiment, the irradiation of the laser light for one pixel is performed during a period in which the high frequency clock is input eight to nine times, but may be another number.
In that case, the length of the annular shift register is set according to the number of times.
[0100]
(Third embodiment)
In the third embodiment, the present invention is applied to an image reading device.
[0101]
FIG. 17 is a block diagram illustrating a configuration of an image reading device according to the third embodiment.
[0102]
In FIG. 17, reference numeral 90 denotes a PLL circuit, which outputs an n-fold high frequency clock based on the input basic clock. This high frequency clock is sent to the frequency dividing circuit 91 and the driving circuit 93. Reference numeral 91 denotes a frequency dividing circuit, which counts the input high frequency clock and outputs one clock pulse every x times to perform (1 / x) frequency dividing. Here, for convenience of explanation, it is assumed that x = n and a clock (main clock) having the same cycle as the basic clock input to the PLL circuit 90 is output. Note that x may be any integer as long as it is an integer.
[0103]
FIG. 18 is a timing chart showing the relationship between the high frequency clock (A) input to the frequency dividing circuit 91 and the main clock (B) output from the frequency dividing circuit 91.
[0104]
FIG. 19 is a timing chart showing the operation of the counter 92 and the drive circuit 93. Hereinafter, reference will be made appropriately.
[0105]
Referring back to FIG. 17, the main clock (FIG. 19A) output from the frequency dividing circuit 91 is input to the counter circuit 92.
[0106]
The drive circuit 93 outputs a drive signal and a video clock synchronized with the high-frequency clock input from the PLL circuit 90 by using the timing signal (FIG. 19B) as a trigger, and sends the drive signal to the CCD element 94 and the video clock. To the analog processor 95 and the A / D converter 96.
[0107]
The counter circuit 92 counts the main clock (FIG. 19A) from the frequency dividing circuit 91, and when the count value reaches a predetermined value (999 in the example of FIG. 19C), outputs an output signal ( FIG. 19D) is transmitted.
[0108]
When this output signal is not transmitted, the drive circuit 93 generates a drive pulse and a video clock whose one period is a first period (the same period as the main clock) in which n high-frequency clocks are input. However, when the output signal is transmitted from the counter circuit 92, a driving pulse and a video clock having one cycle as a second period (a cycle different from the main clock) in which a different number of high frequency clocks from n are input are generated. I do. FIG. 19E shows an image signal output from the CCD element 94 in response to the input of the driving pulse and the video clock. This second period is manually set for the drive circuit 93 in the manufacturing process.
[0109]
FIG. 20 is a diagram showing the configuration of the CCD element 94.
[0110]
The CCD element 94 includes a photosensitive section 94a, a transfer section 94b, and an output section 94c. The photosensitive section 94a is composed of a photodiode array in which a large number of photodiodes are linearly arranged, and converts light into electric charge for each pixel and accumulates the light. The transfer unit 94b includes a shift gate and a CCD analog shift register, and sequentially sends out charges from the photosensitive unit 94a for each pixel in synchronization with a drive signal sent from the drive circuit 93 (FIG. 17). The output unit 94c converts the electric charge sent from the transfer unit 94b into a voltage and outputs the voltage as a voltage signal. Therefore, the duration of the image signal for one pixel depends on the period of the drive signal.
[0111]
FIG. 21 is an equivalent circuit diagram illustrating a configuration of one pixel of the photosensitive unit 94a.
[0112]
The photosensitive section 94a includes one pixel including the photodiode PD, the MOS capacitor C, and the shift electrode T. The input light is photoelectrically converted by the photodiode PD to become a photocurrent, and is accumulated in the MOS capacitor C to become a signal charge. This signal charge is transferred to the transfer section 94b through the shift electrode T. The transfer unit 94b has a function (scanning function) of sequentially sending signal charges generated in the photosensitive unit 94a to the output unit 94c.
[0113]
The output unit 94c includes a floating capacitor and a source follower circuit of a MOS transistor, and has a function of converting signal charges sent from the transfer unit 94b into a voltage. That is, when the signal charge from the transfer unit 94b is injected into the floating capacitor, the potential of the floating capacitor changes, and this is output by the source follower circuit of the MOS transistor.
[0114]
Here, the problems in the conventional image reading apparatus will be described using the image forming apparatus shown in FIG. That is, the distance from the document surface to the lens unit 8 is related to the magnification at which the document forms an image on the image sensor unit 9. Specifically, when the distance is long, the size of the image for one pixel formed on the image sensor unit 9 is large, and when the distance is short, the size of the image is small. Therefore, it is necessary to accurately adjust this distance in the manufacturing process. On the other hand, the scanner unit 4 is moved in the sub-scanning direction. At this time, although not shown in FIG. 1, the moving body on which the mirrors 6 and 7 are mounted moves in the sub-scanning direction at half the speed of the scanner unit 4. Accordingly, the optical path length from the document surface to the image sensor unit 9 is kept constant regardless of the position of the scanner unit 4 in the sub-scanning direction. However, the moving body and the scanner unit 4 are mechanically moved using wires and pulleys. Such a mechanical structure includes many error factors and requires strict fine adjustment in the manufacturing process. As a result, there is a problem that the manufacturing cost increases.
[0115]
Therefore, in the third embodiment, the drive circuit 93 changes the cycle of the drive signal sent to the CCD element 94, whereby the size of the image of one pixel formed on the image sensor unit 9 is always constant. To be. This is equivalent to the optical path length being adjusted to a constant value.
[0116]
That is, an image reading of a certain pixel should be normally performed by a drive signal having a period of n high frequency clocks being input, but a short period of less than n high frequency clocks is input as a period. When the driving signal is applied, the duration of the image signal for one pixel output from the CCD element 94 becomes shorter than usual. This corresponds to a reduction in the size of the image for one pixel. When an image of a certain pixel is read by a drive signal having a cycle of a long period in which more than n high-frequency clocks are input, the duration of the image signal of one pixel output from the CCD element 94 is reduced. But longer than usual. This corresponds to an increase in the size of the image for one pixel. By performing such adjustment, it is possible to make the size of the image of each pixel constant.
[0117]
To change the period of the periodic signal in the drive circuit 93, the number of inputs of the high-frequency clock may be changed, but as a specific configuration, the output circuit in the first or second embodiment can be used.
[0118]
【The invention's effect】
As described in detail above, according to the first or sixth aspect of the present invention, image data for each pixel is received, and a light beam corresponding to the received image data of each pixel is generated. On the other hand, the light beam projection time per pixel is determined according to the position of the projection target where the light beam is to be projected. Then, for each pixel, the generated light beam is scanned and projected onto the projection target for the determined light beam projection time of the corresponding pixel.
[0119]
As a result, the pixel size can be uniformly maintained at any position in the main scanning direction on the photosensitive member without providing the conventional f-θ lens, and as a result, the product size is reduced. Cost reduction can be realized.
[0120]
According to the invention described in claim 8 or claim 12, based on the image data, a plurality of straight lines extending in the axial direction on the surface of the rotating cylindrical body and separated from each other in the rotating direction from the predetermined position. In an image forming apparatus that forms an image by simultaneously scanning and projecting a plurality of light beams related to a plurality of different pixels, image data of each pixel is received, and a plurality of image data corresponding to the received image data of each pixel is received. Generate a light beam. On the other hand, a light beam projection time per pixel is determined according to a position of the cylinder to which one of the plurality of light beams is to be projected. Then, for each pixel, the generated one light beam is projected onto the cylinder over the determined light beam projection time of the corresponding pixel.
[0121]
As a result, the difference in the optical path lengths of the plurality of light beams reaching the cylinder is eliminated, the main scanning width is kept constant at any position in the rotation direction of the surface of the cylinder, and an image formed on the cylinder is formed. Image quality is improved.
[0122]
According to the fourteenth aspect of the present invention, in the image reading apparatus, the original image sent to the imaging device via the optical system is read by the imaging device for each pixel, and image data for each pixel is output. The image reading time of each pixel by the element is determined, and the document image sent to the imaging element is read for each pixel over the determined image reading time of the corresponding pixel, and image data is output.
[0123]
This eliminates the need for conventional optical and mechanical adjustments, and simplifies the adjustment, thereby improving productivity.
[0124]
In contrast to the disadvantages (occurrence of space or missing pixel pieces) of the technique disclosed in Japanese Patent Application Laid-Open No. 2000-238342, in the present invention, an error in light emission duty with respect to input data and missing image information occur. However, in contrast to the technique disclosed in Japanese Patent Application Laid-Open No. 2000-238342, there is no generation of space or lack of pixel information in principle (a pulse width signal or a laser signal from one pixel cycle or the maximum emission cycle and image data). ), The effect on image degradation is minimized. Further, by increasing the multiplication factor, it is possible to minimize the error of the light emission duty with respect to the input image data.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing the entire configuration of a first embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a horizontal plan view showing an internal configuration of an exposure control unit.
FIG. 3 is a circuit diagram of a laser drive circuit in the laser drive device.
FIG. 4 is a block diagram illustrating an internal configuration of a modulation unit according to the present invention.
FIG. 5 is a timing chart showing a relationship between a high-frequency clock (A) input to the frequency dividing circuit and a main clock (B) output from the frequency dividing circuit.
FIG. 6 shows image data (B) for each pixel input from the image processing circuit in synchronization with the correction clock signal (A) and output from the modulation circuit in synchronization with the correction clock signal (A). 5 is a timing chart showing a relationship with a PWM signal (C).
FIG. 7 is a timing chart showing a PWM signal and a correction clock signal output from an output circuit.
FIG. 8 is a diagram illustrating a scanning speed of a laser beam on the surface of a photoconductor when an f-θ lens is not present.
FIG. 9 is a diagram illustrating a scanning speed of laser light on the surface of the photoconductor when an f-θ lens is present.
FIG. 10 is a circuit block diagram illustrating an internal configuration of an output circuit and a modulation circuit according to the first embodiment.
FIG. 11 is a diagram illustrating five areas provided in an image effective area on a photoconductor.
FIG. 12 is a side view showing a photoreceptor and a rotating polyhedron in an image forming apparatus provided with two lasers.
FIG. 13 is a side view corresponding to FIG. 12, in which the interval between two laser beams is extremely increased for easy understanding.
14 is a plan view of the image forming apparatus shown in FIG. 13 as viewed from below.
FIG. 15 is a circuit block diagram illustrating an internal configuration of an output circuit and a modulation circuit according to a second embodiment.
FIG. 16 is a diagram showing four predetermined positions provided at equal intervals in an image effective area on a photoconductor.
FIG. 17 is a block diagram illustrating a configuration of an image reading device according to a third embodiment.
FIG. 18 is a timing chart showing a relationship between a high-frequency clock (A) input to a frequency dividing circuit and a main clock (B) output from the frequency dividing circuit.
FIG. 19 is a timing chart showing operations of the counter and the drive circuit.
FIG. 20 is a diagram showing a configuration of a CCD element.
FIG. 21 is an equivalent circuit diagram illustrating a configuration of one pixel of a photosensitive unit.
[Explanation of symbols]
3 lamps
4 Scanner unit
5,6,7 mirror
8 Lens unit
9 Image sensor section
10 Exposure controller
11 Photoconductor
31 Laser drive
32 aperture
33 rotating polygon mirror (polygon)
35 Collimator lens
36 Beam Detect Sensor (BD Sensor)
40 OR logic element
41 bias current source
42 pulse current source
43 Semiconductor Laser (Laser Chip)
43A laser
43B PD sensor
46 APC circuit
47 Sequence controller
48 Modulation unit
49 switch
60 PLL circuit
61 divider circuit
62 Modulation circuit
63 output circuit
64 counter circuit

Claims (17)

In an image forming apparatus that forms an image by scanning and projecting a light beam from a predetermined position to a linearly projected portion based on image data,
Receiving means for receiving image data for each pixel,
Maximum light emission time determining means for determining a maximum light emission time per pixel according to the position of the projection target to which a light beam is to be projected,
Pulse width modulation beam generating means for generating a light beam pulse having a predetermined light emission duty according to the image data of each pixel received by the receiving means,
An image forming apparatus comprising: a projection unit that scans and projects a light beam pulse generated by the pulse width modulation beam generation unit onto the projection target for each pixel. First clock generating means for generating a first clock pulse having a predetermined first cycle;
A second clock generating means for generating a second clock pulse having a second cycle having a length obtained by multiplying the first cycle by a predetermined number;
The receiving means, the maximum light emission time determining means, the pulse width modulated beam generating means, and the projecting means operate in synchronization with the generation of the second clock pulse, and operate one of the second clock pulses. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is operated in association with a single pixel. 3. The image forming apparatus according to claim 2, wherein the maximum light emission time determination unit recognizes a position of the projection target to which a light beam is to be projected, according to the number of generations of the second clock pulse. . The apparatus according to claim 1, wherein the maximum light emission time determining means sets the maximum light emission time shorter as the position of the projection target to which the light beam is to be projected is closer to an end of the target projection. The image forming apparatus as described in the above. A rotating polyhedron that reflects the light beam;
Further comprising a cylindrical photoconductor irradiated with a light beam reflected from the rotating polyhedron,
The image forming apparatus according to claim 1, wherein the predetermined position is a light beam reflection position on the rotating polyhedron, and the projection target is a surface of the photoconductor. In an image forming apparatus that forms an image by scanning and projecting a light beam from a predetermined position to a linearly projected portion based on image data,
Receiving means for receiving image data for each pixel,
Cycle determining means for determining a cycle per pixel according to the position of the projection target where the light beam is to be projected,
A period determined by the period determination unit, and a modulation pulse generation unit that generates a predetermined light emission duty according to image data of each pixel received by the reception unit;
Output means for outputting a light beam according to a predetermined light emission duty generated by the modulation pulse generation means for each pixel;
An image forming apparatus comprising: a projection unit configured to scan and project the light beam onto the projection target unit. The cycle determining means includes a predetermined number of cascade-connected flip-flops, one output terminal connected to each output terminal of the flip-flop, and the output signal of the receiving means input to the other input terminal. And a selecting means for selecting the cascade connection number of the cascade connection circuit composed of the predetermined number of flip-flops according to the time of projecting the light beam onto the projection target. The image forming apparatus according to claim 6, wherein: Based on image data, simultaneously scan and project a plurality of light beams related to a plurality of pixels on a plurality of straight lines extending in an axial direction on a surface of a rotating cylindrical body and separated from each other in a rotating direction from a predetermined position. In the image forming apparatus that forms an image by performing
Receiving means for receiving image data for each pixel,
A maximum light emission time determining unit that determines a maximum light emission time of a light beam per pixel, according to a position of the cylinder to which one of the plurality of light beams is to be projected;
First generating means for generating at least one light beam according to the image data of each pixel received by the receiving means and the maximum light emitting time determined by the maximum light emitting time determining means,
An image forming apparatus comprising: a second generating unit configured to generate at least one light beam according to image data of each pixel received by the receiving unit. First clock generating means for generating a first clock pulse having a predetermined first cycle;
A second clock generating means for generating a second clock pulse having a second cycle having a length obtained by multiplying the first cycle by a predetermined number;
The receiving unit, the maximum light emission time determining unit, the first generating unit, and the second generating unit operate in synchronization with the generation of the second clock pulse, and generate the second clock pulse. 9. The image forming apparatus according to claim 8, wherein one of the image forming apparatuses operates in association with one pixel. 10. The image according to claim 9, wherein the maximum light emission time determining unit recognizes an axial position of the cylindrical body at which a light beam is to be projected according to the number of occurrences of the second clock pulse. Forming equipment. 9. The image according to claim 8, wherein the maximum light emission time determination unit sets the light beam projection time to be long at a plurality of predetermined positions in the axial direction of the cylindrical body where the light beam is to be projected. Forming equipment. Based on image data, simultaneously scan and project a plurality of light beams related to a plurality of pixels on a plurality of straight lines extending in an axial direction on a surface of a rotating cylindrical body and separated from each other in a rotating direction from a predetermined position. In the image forming apparatus that forms an image by performing
Receiving means for receiving image data for each pixel,
A period determining unit that determines a period per pixel according to a position of the cylinder to which one of the plurality of light beams is to be projected;
First modulation pulse generation means for generating a predetermined light emission duty according to the cycle determined by the cycle determination means and the image data of each pixel received by the reception means,
A second modulation pulse generation unit that generates a predetermined light emission duty according to the image data of each pixel received by the reception unit;
Output means for outputting, for each pixel, a light beam according to the light emission duty generated by the first and second modulation pulse generation means;
An image forming apparatus comprising: a projection unit configured to project the light beam output by the output unit onto the cylindrical body. The cycle determining means includes a predetermined number of cascade-connected flip-flops, one output terminal connected to each output terminal of the flip-flop, and the output signal of the receiving means input to the other input terminal. 13. The AND circuit according to claim 12, further comprising: selecting means for selecting a cascade connection number of the cascade connection circuit including the predetermined number of flip-flops according to a projection time of the light beam. Image forming apparatus. An image reading device that reads a document image sent to an image sensor through an optical system for each pixel by the image sensor and outputs image data for each pixel,
Cycle determination means for determining a cycle in each pixel by the image sensor,
An image reading apparatus comprising: an output unit that reads a document image sent to the image sensor for each pixel at a cycle determined by the cycle determining unit and outputs image data. 15. The image reading apparatus according to claim 14, wherein the period determination unit determines an image reading time according to information input from outside according to adjustment of the optical system. First clock generating means for generating a first clock pulse having a predetermined first cycle;
A second clock generating means for generating a second clock pulse having a second cycle having a length obtained by multiplying the first cycle by a predetermined number;
15. The image reading apparatus according to claim 14, wherein the output unit operates in synchronization with the generation of the second clock pulse, and operates by associating one of the second clock pulses with one pixel. 17. The image reading apparatus according to claim 16, wherein the output unit recognizes a pixel to be read by the image pickup device according to the number of occurrences of the second clock pulse.

Images