JP4308495B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device such as a laser printer or a digital copying machine, and an image forming apparatus including the optical scanning device, and more particularly to generation of a pixel clock and phase control thereof.
[0002]
[Prior art]
The prior art of the image forming apparatus will be described with reference to FIG. In FIG. 43, the laser emitted from the semiconductor laser unit 1001 is scanned in one direction as the polygon mirror 1002 rotates, and forms a light spot on the scanned medium (photoconductor) 1004 via the scanning lens 1003. Then, an electrostatic latent image is formed. At this time, the scanning light is detected by detection means 1005 and 1010 on the extension of the scanned medium, and the detection timings of both detection signals are input to the phase synchronization circuit 1009 via the time counter 1011 and the lookup table 1012. . The phase synchronization circuit 1009 receives the clock of the clock generation circuit 1008, generates an image clock (pixel clock) that is phase-synchronized for each line based on the output signal of the lookup table 1012, and the image processing unit 1006. And supplied to the laser driving circuit 1007. In this way, the semiconductor laser unit 1001 controls the emission time of the semiconductor laser according to the image data generated by the image processing unit 1006 and the image clock whose phase is set for each line by the phase synchronization circuit 1009. The electrostatic latent image on the scanned medium 1004 is controlled.
[0003]
Conventionally, Patent Document 1 discloses an example of correcting the writing position of the image forming position of each color in a color laser printer or the like within one clock error. In addition, as an example of adjusting the writing position in the main scanning direction and the writing end position with respect to the shift of the image forming position in the main scanning direction in the image forming apparatus, there is Patent Document 2. Furthermore, in the optical scanning device using the multipoint synchronization method, the dot position deviation is corrected as an example.
[0004]
[Patent Document 1]
JP 2000-238319 A
[Patent Document 2]
JP 2000-28925 A
[Patent Document 3]
JP-A-6-59552
[0005]
[Problems to be solved by the invention]
In the scanning optical system, the scanning speed unevenness causes image fluctuation and causes deterioration of image quality due to generation of a vertical stripe image. As a result, a main scanning dot position shift occurs, and this appears as a color shift particularly in a color image, resulting in deterioration of color reproducibility and resolution. When high quality image quality is required, it is necessary to correct the scanning speed unevenness.
[0006]
In a plurality of scanning optical systems corresponding to a multicolor image forming apparatus, it is a very important issue to reduce relative scanning line inclination, scanning line bending, full width magnification error, and partial magnification error. Here, the initial characteristics can be adjusted by measuring the obtainability before assembly, but changes over time such as temperature fluctuations need to be measured in the machine.
[0007]
At this time, the scanning line inclination and the full width magnification error can be measured on both sides outside the effective writing width, but the scanning line bend and the partial magnification error need to be measured within the effective writing width. However, at this time, it is necessary to separate the light beam guided to the effective writing width from the light beam for detection, but separation is very difficult, and a deflector such as a polygon mirror and a scanning optical element become large. In addition, since the light beam toward effective writing is separated from the light beam for synchronization detection, the synchronization detection accuracy is deteriorated.
[0008]
Currently, a method of scanning a surface to be scanned by arranging a plurality of scanning optical systems in the main scanning direction is widely known. However, since the scanning optical systems are arranged in parallel in the main scanning direction, It is difficult to separate the light beam for synchronization detection.
[0009]
In the optical scanning optical system, uneven scanning speed on the surface to be scanned (on the photosensitive member) occurs for the following reason.
1. When the fθ characteristic of the scanning lens is not sufficiently corrected
2. Deterioration of optical component accuracy of optical scanning optical system and mounting accuracy on housing
3. Deformation to optical components due to environmental fluctuations such as temperature and humidity inside the machine, and focal length changes due to refractive index fluctuations, and fθ characteristics deteriorate.
4). Variation in scanning speed of the light spot (scanning beam) that scans the surface to be scanned due to variations in the distance from the rotation axis of the deflecting and reflecting surface of a deflector such as a polygon scanner
In particular, the main scanning dot position shift due to the environmental change described in 3 above cannot be avoided even if optical adjustment or electrical correction is performed at the time of shipment. In order to meet the recent demand for higher image quality, it is necessary to solve this problem. Further, as described above, when high-quality image quality is required, it is necessary to correct the scanning speed unevenness.
[0010]
In particular, in the case of a multi-beam optical system, when there is a difference in the oscillation wavelength of each light source, in the case of an optical system in which the chromatic aberration of the scanning lens is not corrected, an exposure shift occurs, and a light spot corresponding to each light source. However, the scanning width when scanning the scanned medium causes a difference for each light source and causes deterioration in image quality. Therefore, it is necessary to correct the scanning width.
[0011]
However, when the above correction is performed, the occurrence of scanning unevenness by the optical system differs on the scanning line due to the characteristics of the optical system. In addition, correcting all image data to correct scanning unevenness increases the amount of correction data and increases the cost to the control system, the circuit scale, and the like.
[0012]
Neither Patent Document 1 nor Patent Document 2 can correct the influence of the main scanning dot position shift caused by the optical system or the deflector. Patent Document 3 is a method of changing the PLL frequency for dot position correction. Therefore, the clock signal fluctuates due to the influence of frequency fluctuation during the PLL lockup time, and the clock is corrected with high accuracy. Can not do it.
[0013]
An object of the present invention is to enable measurement for enabling dot position correction over time with a simple configuration at low cost, space saving, and based on information measured by a plurality of detection units, To provide an optical scanning device and an image forming apparatus capable of highly accurate dot position correction.
[0014]
In addition, an object of the present invention is to make it possible to perform measurement for enabling main scanning dot position correction over time with a simple configuration at a low cost and in a space-saving manner, and also with a plurality of reflecting or transmitting members. It is an object to provide an optical scanning apparatus and an image forming apparatus capable of highly accurate main-scanning dot position deviation correction based on information measured by two detection units.
[0015]
[Means for Solving the Problems]
The present invention includes a light source, a deflecting unit that deflects a light beam emitted from the light source, and a light guide unit that guides the light beam deflected by the deflecting unit to a surface to be scanned and a surface to be detected different from the surface to be scanned. A high frequency clock generating means for generating a high frequency clock, and a high frequency clock and a pixel clock output from the high frequency clock generating means. Phase data indicating the amount of phase shift and In an optical scanning device comprising pixel clock generation means for generating a pixel clock based on In the detected surface, A detection position in the reverse direction of scanning from the effective writing start position on the scanned surface. Above Including a first detection signal detected when the light beam scans, and an effective writing end position; The Scanning direction from effective write end position The detection position at Based on the second detection signal detected when the light beam scans, the phase data is Generation It is characterized by doing.
[0016]
The present invention also provides a light source, deflecting means for deflecting the light beam emitted from the light source, and guiding the light beam deflected by the deflecting means to a surface to be scanned and a surface to be detected different from the surface to be scanned. Optical means, high-frequency clock generating means for generating a high-frequency clock, high-frequency clock and pixel clock output from the high-frequency clock generating means Phase data indicating the amount of phase shift and In an optical scanning device comprising pixel clock generation means for generating a pixel clock based on In the detected surface, An effective writing end position, which includes a first detection signal detected when a light beam scans a detection position in the opposite direction of scanning from the effective writing start position on the surface to be scanned, and an effective writing end position; More scanning direction The detection position at A second detection signal detected when the light beam scans; Above Approximately the same position as the effective write start position The detection position at Based on the third detection signal detected when the light beam scans, the phase data is Generation It is characterized by doing.
[0017]
The present invention also provides a light source, deflecting means for deflecting the light beam emitted from the light source, and guiding the light beam deflected by the deflecting means to a surface to be scanned and a surface to be detected different from the surface to be scanned. Light means; In the detected surface Substantially the same position as the scanned surface Scan Multiple reflections of luminous flux Thru Detection means for detecting by one detection unit via a reflection / transmission member, high-frequency clock generation means for generating a high-frequency clock, high-frequency clock and pixel clock output from the high-frequency clock generation means Phase data indicating the amount of phase shift and And a pixel clock generating means for generating a pixel clock based on the plurality of reflections through the plurality of reflections. Reflection Based on the scanning time that the light beam traverses the transmissive member, the phase data is Generation It is characterized by doing.
[0018]
Furthermore, an embodiment of the optical scanning device of the present invention is characterized in that it has a region where light beams directed from a plurality of reflecting or reflecting / transmitting members to the detecting means overlap.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
First, a pixel clock generating device used in the optical scanning device and the image forming apparatus of the present invention will be described.
FIG. 36 shows a configuration diagram of an embodiment of the pixel clock generation apparatus. In FIG. 36, a data area setting signal generation circuit 11 Is configured by inputting a data area setting value that determines the number of pixel clocks in the data area, counting the pixel clock PCLK output from the pixel clock generation circuit 14, and including a plurality of continuous pixel clock signals, that is, PCLK. A data area setting signal that is a timing for determining the data area is generated. The phase data storage circuit 12 stores in advance external phase data indicating phase shift data such as one line, and the phase in the corresponding data area is determined by the timing of the data area setting signal output from the data area setting signal generation circuit 11. Read shift data. The phase data generation circuit 13 generates the pixel clock of the data area setting value in the corresponding data area according to the timing of the data area setting signal and the pixel clock PCLK. count In the meantime, phase data indicating that the phase is shifted in the positive or negative direction by the number of times based on the phase shift data read from the phase data storage circuit 12 is generated. The phase data is generated in units of one pixel clock. For example, “+” is used to shift 1/8 PCLK in the positive direction, “−1” is used to shift 1/8 PCLK in the negative direction, “ 0 ". As will be described later, the pixel clock generation circuit 14 generates, for example, a pixel clock PCLK corresponding to a quarter of the high-frequency clock VCLK, and shifts, for example, 0, +1/8 PCLK, −1/8 PCLK based on the phase data. Let
[0020]
FIG. 37 shows a specific configuration example of the clock generation circuit 14. In FIG. 37, the high-frequency clock generation circuit 100 generates a high-frequency clock VCLK serving as a reference for the pixel clock PCLK. Counter (1) 1403 is a counter that operates at the rising edge of the clock of VCKL. The comparison circuit (1) 1404 compares the value of the counter (1) 1403 with a preset value and the comparison value 1 output from the comparison value generation circuit 1402, and outputs a control signal 1 based on the result. The clock 1 generation circuit 1405 generates the clock 1 based on the control signal 1. On the other hand, the counter (2) 1406 is a counter that operates at the falling edge of the clock of VCKL. The comparison circuit (2) 1407 compares the value of the counter (2) 1406 with a preset value and the comparison value 2 output from the comparison value generation circuit 1402, and outputs a control signal 2 based on the result. The clock 2 generation circuit 1408 generates the clock 2 based on the control signal 2. The multiplexer 1409 selects clocks 1 and 2 based on the select signal, and outputs them as the pixel clock PCLK.
[0021]
The comparison value generation circuit 1402 outputs the comparison value 1 and the comparison value 2 based on the phase data output from the previous phase data generation circuit 13 and the status signal output from the status signal generation circuit 1401. When the bit 0 of the phase data is 1, the status signal generation circuit 1401 toggles the signal at the rising timing of PCLK and outputs it as a status signal. When the bit 0 of the phase data is 1, the select signal generation circuit 1410 toggles the signal at the falling timing of PCLK and outputs it as a select signal.
[0022]
The operation outline of FIG. 37 will be described with reference to the timing chart of FIG. This operation is described in detail in Japanese Patent Application No. 2001-290469 filed earlier by the present applicant.
[0023]
Here, a case will be described in which the pixel clock PCLK corresponding to the four-frequency division of the high-frequency clock VCLK is generated and shifted by +1/8 PCLK and -1/8 PCLK as the phase shift. FIG. 39 shows the correspondence between the phase shift amount and the phase data. FIG. 38 shows the phase shift amount and how the clock 1 and clock 2 are switched.
[0024]
First, the operation starts from the state where the clock 1 is selected by the multiplexer 1409. Assume that phase data “00” is given in synchronization with PCLK (A). Since the phase data bit0 is 0, the select signal remains 0 and the clock 1 is selected and output as PCLK (b). As a result, PCLK becomes a clock having a phase shift amount of zero.
[0025]
Next, it is assumed that “01” is given as the phase data (C). In this case, since the phase data bit0 is 1, the select signal is toggled at the falling edge of PCLK, and the clock 2 is selected as 1 and output as PCLK (d). As shown in FIG. 38, the clock 2 at this time is a clock whose period is increased by 1 VCLK (e). As a result, PCLK shifted by +1/8 PCLK is obtained. Next, when "01" is given again as the phase data (e), since the phase data bit0 is 1, the select signal is toggled at the falling edge of PCLK, and the clock 1 is selected as 0 and output as PCLK (he) ). As shown in FIG. 112, the clock 1 at this time is a clock whose period is increased by 1 VCLK (G). As a result, similarly, PCLK shifted in phase by +1/8 PCLK is obtained.
[0026]
Next, it is assumed that “11” is given as the phase data (g). Since the phase data bit0 is 1, the select signal is toggled at the falling edge of PCLK, and the clock 2 is selected as 1 and output as PCLK (H). At this time, the clock 1 is a clock whose period is shortened by 1 VCLK as shown in FIG. As a result, PCLK shifted by −1/8 PCLK is obtained.
[0027]
The pixel clock shifted in phase by 1/8 PCLK step by changing the period of clock 1 and clock 2 according to the phase data as described above, switching clock 1 and clock 2 and outputting them as PCLK. PCLK can be obtained.
[0028]
FIG. 40 shows the principle of phase shift correction by the pixel clock generator shown in FIGS. As described above, in the pixel clock generation circuit of FIG. 37, the phase of the pixel clock PCLK can be shifted by +1/8 PCLK and −1/8 PCLK by providing phase data in synchronization with the pixel clock PCLK. is there.
[0029]
The ideal state in FIG. 40 shows the dot position in the ideal state where no scanning speed unevenness or exposure deviation occurs, and is the result of scanning 6 consecutive dots at 1200 dpi (dot diameter of about 21.2 μm). Before the correction in FIG. 40, the dot position accuracy of the first dot is the same, but the dot position shift is caused by uneven scanning speed or exposure shift, and the sixth dot is 1200 dpi relative to the ideal state. A dot position deviation of 10.6 μm, which is equivalent to 1/2 dot, is generated. Since the time required for writing one dot in this state is equivalent to one pixel clock = 1PCLK, this means that when the phase shift resolution is 1/8 PCLK, that is, the dot position can be corrected with 1/8 dot accuracy. After the correction of FIG. 114, when the phase shift resolution is 1/8 dot, that is, 1/8 PCLK, the phase shift of -1/8 PCLK from the state before the correction, which has caused the ½ dot position shift from the ideal state, is within the data area. In theory, the dot position of the sixth dot can be shifted by 1/8 PCLK × 4 = −1 / 2 PCLK, and the dot position is corrected with an accuracy of 1/8 PCLK with respect to the ideal state. It shows that you can.
[0030]
FIG. 41 shows an operation example when the data area setting value = 30 and the external phase data = −3. Here, the phase data shifts 1 and 2 indicate the phase data, and the phase of the PCLK signal at the timing when the 2-bit phase data becomes 1 is corrected to −1/8 PCLK from FIG.
[0031]
In FIG. 41, the main scanning dot position deviation in the data area is corrected by performing a phase shift of −1/8 PCLK three times between the data areas 30PCLK. In addition, the PCLK signal is output at the timing of the phase synchronization signal and is input to each signal generation circuit. However, since the actual image area is after a certain number of PCLK clock oscillations from the timing of the phase synchronization signal, The input unit is provided with a counter for inputting a PCLK signal only after counting a certain number of PCLKs. Also, a certain number of PCLK signals can be defined as a data area by setting the data area set value to a value of a certain characteristic.
[0032]
FIG. 42 shows a configuration diagram of another embodiment of the pixel clock generator. In the present embodiment, the pixel clock generation device of FIG. 36 is provided with a data area setting value storage circuit 15 for calling the data area setting value at the timing of the data area setting value and the PCLK signal set from the outside. The characteristic data of the main scanning dot position deviation is acquired in advance, and the number of PCLKs in the data area at each image height is stored in the data area setting value storage circuit 15 based on the data, whereby FIG. ) When the number of PCLK is a constant number and the number of divisions is 22, and when the number of data in the data area is changed according to the image height and the number of divisions is 10 as shown in FIG. In spite of the difference in the number of divisions, the amount of deviation between the data areas, which is the maximum value of the main scanning dot position deviation amount, can take a value that is almost unchanged.
[0033]
In this way, it is possible to correct to the same main scanning dot position shift amount with a smaller number of data areas than in the case of a fixed number, and it is possible to reduce the number of data used for phase data and the memory required for data storage It becomes.
[0034]
Here, consider a case where the data area setting value is given based on the main scanning dot position deviation data measured in advance. As the main scanning dot position deviation data acquisition method, two PDs having a fixed distance are arranged in the image height direction, the time difference between two sensors when actually scanning light is measured, and the time difference is determined as the dot position. This is obtained by converting to a shift and performing this measurement on the total image height.
[0035]
In the main scanning dot position deviation data, the image height data X (n) is
X (-n), X (-n + 1), ... X (-1), X (1), X (2), ... X (n-1), X (n)
The main scanning dot position deviation data Y (n)
Y (-n), Y (-n + 1), ... Y (-1), Y (1), Y (2), ... Y (n-1), Y (n)
In this case, the absolute value | Y (a + b) −Y (a) | of the main scanning dot position deviation between the image heights X (a) and X (a + b) (a and b are integers) is less than a certain value. Thus, an arithmetic circuit for determining the interval between the image heights is provided, and data corresponding to the data area set value can be acquired by synchronizing the interval between the image heights with the PCLK signal. The above data area setting value is such that the data area is narrowed between image heights where the displacement of the main scanning dot position deviation is large, and the data area is widened between image heights where the displacement is small. Compared to the above, the configuration in which the number of data in the data area is changed according to the image height makes it possible to reduce the amount of main scanning dot position deviation.
[0036]
Further, it is possible to correct the amount of main scanning dot position deviation with the same number of data areas as compared with the case of a fixed number, and it is possible to reduce the number of data used for phase data and the memory required for storing the data.
[0037]
FIG. 1 shows an overall configuration diagram of an embodiment of an optical scanning device according to the present invention. Laser light from the semiconductor laser 201 passes through a collimator lens 202 and a cylinder lens 203, is scanned (scanned) by a polygon mirror 204, passes through a scanning lens (fθ lens) 205, and is a scanned medium via a transparent member 206. By entering the photoconductor 207, an image (electrostatic latent image) is formed on the photoconductor 207. In order to start writing the scanning laser beam at the effective writing start position, the detector 101 detects a signal before the light beam scans the effective writing start position, and includes the effective writing end position. A position in the scanning direction is detected from the insertion end position by the detector 102 and input to the dot position deviation detection / control unit 110. The dot position deviation detection / control unit 110 measures the time during which the laser beam is scanned between the detection units 101 and 102 and compares it with the scanning time when ideal scanning is performed. The amount is obtained, phase data for correcting the shift amount is generated, and output to the pixel clock generation unit 120 as external phase data. Note that the output signal of the detection unit 101 is also provided to the image processing unit 130 as a line synchronization signal.
[0038]
The pixel clock generation unit 120 has the configuration described above with reference to FIGS. 36, 37, 42, and the like. Here, when the pixel clock generation unit 120 does not include a phase data storage circuit, the dot position deviation detection / control unit 110 outputs external phase data to the pixel clock generation unit 120 for each line. In the case where a storage circuit is provided, the phase data is obtained in advance, for example, by obtaining the phase data in advance. In addition, the dot position deviation detection / control unit 110 rotates not only the phase data (first phase data) for always making the same correction for each line so as to correct the scanning unevenness caused by the characteristics of the scanning lens, but also the rotation of the polygon mirror. When phase data (second phase data) corresponding to correction such as unevenness that changes for each line is also generated and the pixel clock generation unit 120 includes a phase data synthesis circuit, the phase data is generated. Are also output to the pixel clock generator 120.
[0039]
The pixel clock generation unit 120 receives the high frequency clock VCLK of the high frequency clock generation unit 100, generates a pixel clock PCLK whose phase is controlled based on external phase data from the dot position deviation detection / control unit 110, and an image processing unit. 130 and the laser drive signal generation unit 140. The image processing unit 130 generates image data based on the pixel clock PCLK, and the laser drive signal generation unit 140 receives the image data and similarly generates a laser drive signal (modulation signal) based on the pixel clock. Then, the semiconductor laser 201 is driven via the laser driving unit 150. As a result, an image having no positional deviation can be formed on the photosensitive member 207.
[0040]
Here, the dot position shift of the optical scanning optical system will be described with reference to FIG. The horizontal axis in FIG. 2 represents the ideal image height (ideal dot position based on image data), and the vertical axis represents the real image height (actual dot position via the optical scanning optical system). Ideally, a linear characteristic with an inclination of 1 (optically fθ characteristic is corrected well) is desirable, but in general, it is not linear (constant speed scanning) for the following reason. Is curved (uneven scanning speed occurs).
[0041]
In other words, the actual main scanning dot position deviates from the ideal main scanning dot position. The following three factors can be considered as the cause.
1. The fθ characteristic of the scanning lens is not sufficiently corrected
2. Deterioration of optical component accuracy of optical scanning optical system and mounting accuracy on housing
3. Deformation of optical components due to environmental changes such as temperature and humidity inside the machine, and focal length changes due to refractive index fluctuations.
fθ characteristics deteriorated
In particular, the main scanning dot misalignment due to environmental fluctuations cannot be avoided even if optical adjustment or electrical correction is performed at the time of shipment. For example, even if the characteristics at the time of first printing are (a), continuous printing is performed. When output, the temperature inside the machine rises and may change to the characteristic value of (b). As a result, the hue of the first print and the hue after printing a plurality of sheets may change.
[0042]
Therefore, the present invention grasps in advance the characteristic value of the relationship between the actual image height and the ideal image height of the optical scanning optical system to be used in the present invention by preliminary experiments or simulations, and uses a lookup table or the like from the characteristic value. create. The dot position deviation detection / control unit 110 sequentially measures the optical scanning time when the print is actually driven, obtains the dot position correction amount from the lookup table based on the measured scanning time, and sets the dot position to the ideal position. The phase shift amount is determined so that As a result, it is possible to effectively correct the dot position deviation in the main scanning direction caused by environmental fluctuations in the apparatus.
[0043]
FIG. 3 and FIG. 4 show a first embodiment of a method for correcting the dot position in the optical scanning device of FIG. 1 to an arbitrary position. In FIG. 3, when generating a pixel clock after a certain period from the fall of the phase synchronization signal that sets the timing for starting writing, the semiconductor laser is modulated based on the pixel clock signal within an effective scanning period that becomes an actual image region, Light emitted from the semiconductor laser passes through an optical system to form an electrostatic latent image on the photoreceptor. At this time, even if the pixel clock has a fixed period, the electrostatic latent image on the photosensitive member is displaced in the main scanning direction by the deflector or the optical system, and the electrostatic latent image is displaced. Will eventually lead to dot misalignment (FIG. 4). At this time, the effective scanning period in the main scanning direction varies depending on the optical system. In this example, when the center of the image height is 0, the maximum and minimum values of the image height are relative to the image height ratios 1 and -1, respectively. Is defined.
[0044]
FIG. 4 shows a main scanning position deviation amount with the vertical axis representing the main scanning position deviation amount and the horizontal axis representing the image height ratio. The optical system characteristic of FIG. 4A has a characteristic that the change amount is large at a place where the image height is high, and the change amount is small when the image height is near zero. In addition, the pixel clock generation circuit (for example, 36) having a phase shift function capable of shifting the phase of the pixel clock for each clock by a fraction of a dot of the clock allows the main scanning position of each pixel to be a fraction of ±. Since the shift can be performed in dot units, in principle, in the case of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%. In the case of 1200 dpi writing, the main scanning position deviation within the effective writing width can be reduced to 2.6 μm (21.2 μm / 8).
[0045]
In this embodiment, the signal is detected at the scanning timing before the effective write start position, thereby synchronizing the asynchronous clock with the detection signal, improving the clock position accuracy at the effective write start position, and effective. By detecting a signal when the light beam scans in the same position as the writing end position or in the scanning direction, an effective writing area is obtained based on the detection signal before the writing start position and the detection signal after the writing end position. By detecting a fluctuation component such as a dot position deviation in the inside and providing it as phase data, the dot position deviation within the effective scanning period is corrected with high accuracy.
[0046]
FIG. 5 and FIG. 6 show an embodiment in which a signal is detected and a phase data is corrected when a light beam scans an effective writing end position. Here, FIG. 5 corresponds to FIG. 3 and FIG. 6 corresponds to FIG. 4, and the transition timing of the pixel clock is determined based on the detection signal when the light beam scans the substantially same position as the effective writing end position. By providing the phase data to be generated, it is possible to reduce the main scanning dot position shift with higher accuracy than the embodiments shown in FIGS.
[0047]
As shown in FIG. 7B, the detection means (detector) in the embodiment of FIG. 1 includes a triangular photodetector (PD) or a triangular slit disposed just before the PD, and FIG. It is comprised by the combination of square-shaped PD etc. which are shown to (a). At this time, the position in the sub-scanning direction can be measured by detecting the time (t1, t2 in the figure) when the PD detects the beam, and each detection means can be detected by detecting the rise of the beam entering the PD. It is possible to measure the time difference of beam detection by. The magnification error can be measured by the measured time difference (t3, t4).
[0048]
In each of the following embodiments, as shown in FIG. 5, the second detection signal is detected when the light beam scans the position in the scanning direction from the effective writing end position, including the effective writing end position. In this embodiment, signal detection is performed when the light beam scans a position substantially the same as the effective writing end position.
[0049]
FIG. 8 shows another embodiment of the optical scanning device of the present invention. In this embodiment, the reflected light on the first surface of the flat glass 206 is detected by the detectors 101, 102, and 103 arranged on the detection surface. In FIG. 8, the laser emitted from the semiconductor laser 201 is deflected and scanned by the rotation of the polygon mirror 204, forms a light beam spot on the scanned medium (on the photosensitive member) 207 via the scanning lens 205, and is static. An electrostatic latent image is formed.
[0050]
In this embodiment, as detection means, photodetectors 101, 102, 103 are provided at two positions on the writing start position side and end position side and one position in the writing area (substantially the same position as the effective writing start position). The scanning time when the beam deflected and scanned by the polygon mirror 204 of the deflector crosses each of the photodetectors 101, 102, and 103 is measured, and recorded in advance based on the variation of the measured scanning time. The correction amount of the main scanning dot position is set from a lookup table or the like. An image clock phase-shifted by the pixel clock generation unit 120 is generated based on the correction amount data, and the emission time of the semiconductor laser is controlled by the pixel clock according to the image data generated by the image processing unit 130. The dot position on the scanning medium can be controlled to an arbitrary position.
[0051]
In this embodiment, the light beam traveling toward the detection means is reflected by the first surface of the transparent member 206. For this reason, the following effects are acquired. The same applies to other embodiments.
1. The number of transmitting surfaces is reduced, the deterioration of the wavefront of the light beam for detection is reduced, and an accurate beam position can be detected.
2. Since the detection beam is not affected by absorption by the material and the number of transmitting surfaces is reduced, light loss is reduced, and accurate beam detection is possible.
3. By using a transparent material with a high reflectivity of the transparent member so that the detection beam is not easily affected by absorption by the material, the level of reflected light is reduced, resulting in less light loss and accurate beam detection. It becomes possible.
[0052]
An embodiment of a method for correcting the dot position to an arbitrary position in the optical scanning device of FIG. 8 is shown in FIGS. FIG. 9 corresponds to FIG. 3 and FIG. FIG. 10 shows a main scanning position deviation amount with the vertical axis representing the main scanning position deviation amount and the horizontal axis representing the image height ratio. The optical system characteristic of FIG. 10A has a characteristic that the change amount is large at a place where the image height is high, and the change amount is small when the image height is near zero.
[0053]
The pixel clock generation unit 120 having a phase shift function capable of shifting the phase of the pixel clock by a fraction of a dot of the clock for each clock can shift the main scanning position of each pixel in units of ± 1 / dot. Therefore, in principle, in the case of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%. In the case of 1200 dpi writing, the main scanning position deviation within the effective writing width can be reduced to 2.6 μm (21.2 μm / 8).
[0054]
FIG. 11 shows an embodiment of an optical system in the optical scanning device of FIG. In the embodiment of FIG. 11, the beam splitter 206 ′ separates and detects the light beam traveling toward the surface to be scanned and the light beam traveling toward the detecting means into light beams in different directions. The beam splitter 206 ′ is formed by joining two pairs of right-angled triangular prisms, and the joint surface is a half mirror surface. A part of the light incident on the beam splitter 206 ′ passes through the half mirror surface, and the transmitted light travels straight and scans the scanned medium 207. On the other hand, the light reflected by the half mirror surface is bent downward as shown in FIG. 11B to form reflected light. By separating the light beam scanned on the scanned medium 207 and the light beam detected by the detectors 101, 102, and 103 by the beam splitter 206 ', it is possible to detect light beams in different directions at the same time.
[0055]
With this configuration, the first scan of the laser beam on the scanned medium 207 by the rotation of the polygon mirror 204 and the reflected light from the half mirror surface of the beam splitter 206 ′ cause a different direction and position from the scanned medium surface. Since the second scanning is performed in FIG. 4, by arranging the detectors 101, 103, 102 on the second scanning line, a phase synchronization signal can be obtained along with the rotational speed of the polygon motor.
[0056]
The embodiments of FIGS. 8 and 11 are characterized in that a light beam scanned at substantially the same position as the surface to be scanned is detected by a detection means that detects a plurality of detectors 101, 102, and 103. According to this embodiment, since the luminous flux can be detected in real time at the start and end timing of the effective writing area, phase synchronization control and dot writing position correction can be performed in real time with high accuracy. It becomes.
[0057]
FIG. 12 shows a configuration in which three detectors 101, 102, and 103 are arranged on substantially the same support body 104 in the embodiment of FIGS. 8 and 11. By doing so, it becomes possible to reduce fluctuations in the position and orientation of the reflecting member and detection means due to temperature fluctuations and environmental fluctuations, and more accurate main scanning dot position detection and main scanning dot position deviation correction are possible. Become.
[0058]
FIG. 13 shows still another embodiment of the optical scanning device of the present invention. In the embodiment of FIG. 13, the reflected light on the first surface of the transparent member 206 such as flat glass is further reflected by the reflecting members 209, 210, and 211 arranged in the scanning direction and detected by one detector 105. is there. In FIG. 13, the laser emitted from the semiconductor laser 201 is deflected and scanned by rotating the polygon mirror 204, forms a light beam spot on the scanned medium (on the photosensitive member) via the scanning lens 205, and electrostatically A latent image is formed.
[0059]
In this embodiment, reflecting members 209, 210, and 211 are provided at two positions on the writing start position side and end position side and one position in the writing area with respect to one detector 105, the polygon mirror 204, A beam deflected and scanned by the scanning lens 205 traverses the reflecting members 209, 211, and 210, and a scanning time interval in which the reflected light is detected by one detector 105 is measured, and the variation in the measured scanning time is measured. Based on the amount, the correction amount of the dot position for main scanning is set from a pre-recorded lookup table or the like. Based on the correction amount data, an image clock phase-shifted by the pixel clock generation unit 120 is generated, and the emission time of the semiconductor laser 201 is controlled according to the image data generated by the image processing unit 130 using the pixel clock. Thus, the dot position on the scanned medium 207 can be controlled to an arbitrary position.
[0060]
FIG. 14 shows an embodiment of the optical system in the configuration of FIG. In this embodiment, a beam splitter 206 ′ separates and detects a light beam directed to the surface to be scanned and a light beam directed to the detection means into light beams in different directions.
[0061]
The beam splitter 206 ′ is formed by joining two pairs of right-angled triangular prisms, and the joint surface is a half mirror surface. A part of the light incident on the beam splitter 206 ′ passes through the half mirror surface, and the transmitted light travels straight and scans the scanned medium 207. On the other hand, the light reflected by the half mirror surface of the beam splitter 206 ′ is bent downward to form reflected light as shown in FIG. By separating the light beam scanned on the scanned medium 206 and the light beam detected by the detector 105 with a beam splitter, light beams in different directions can be detected simultaneously.
[0062]
With this configuration, in the direction and position different from the surface of the scanned medium due to the first scanning of the laser light on the scanned medium by the rotation of the polygon mirror 204 and the reflected light from the half mirror surface of the beam splitter 206 ′. Since the second scan is performed, reflection and reflection / transmission members 209, 210, and 211 are formed on the second scan line, and the reflected and transmitted light beams are detected by one detector 105, so that the polygon motor A synchronization detection signal can be obtained along with the rotation speed.
[0063]
FIG. 15 shows another embodiment of the detection scanning optical system. In this embodiment, the reflected light reflected by the reflection / transmission member 206 is further reflected and transmitted by a plurality of reflection members and reflection / transmission members 209, 210, 211, and then guided to one detector 105. It has been. The feature of this embodiment is that the light beam is reflected and transmitted through the plurality of reflection / reflection / transmission members 209, 210, 211, and then guided to the detection 105, and the reflection / transmission members 209, 210, 211, the detector 105 is disposed on the support 106, and with this configuration, the layout of the detection system including the reflection / transmission members 209, 210, 211 and the detector 105 can be configured in a compact manner. This leads to miniaturization of the optical scanning device.
[0064]
Next, referring to FIGS. 6 and 10, an embodiment will be described in which the main scanning position deviation is corrected by giving a phase to each data area composed of a plurality of units, with one period of the pixel clock as one unit.
[0065]
In FIG. 6, when generating a pixel clock after a certain period from the fall of the phase synchronization signal that sets the write start timing, the semiconductor laser is modulated based on the pixel clock signal within an effective scanning period that becomes an actual image region, When the light emitted from the semiconductor laser forms an electrostatic latent image on the photoconductor through the optical system, the electrostatic latent image on the photoconductor is displaced in the main scanning direction by a deflector or an optical system. At this time, the effective scanning period indicating the main scanning direction varies in length depending on the optical system. In this example, when the center of the image height is 0, the maximum and minimum values of the image height are defined as the image height ratio 1 and -1, respectively. is doing.
[0066]
6A to 6C, the main scanning position deviation amounts are shown on the vertical axis and the image height ratio on the horizontal axis. The optical system characteristic of FIG. 6A has a characteristic that the change amount is large at a place where the image height is high and the change amount is small when the image height is near zero. Since the pixel clock generation unit having a phase shift function capable of shifting the phase of the pixel clock in units of a fraction of the clock for each clock, the main scanning position of each pixel can be shifted in units of ± a few dots. In principle, in the case of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%. In the case of 1200 dpi writing, the main scanning position deviation within the effective writing width can be reduced to 2.6 μm (21.2 μm / 8).
[0067]
At this time, in order to provide phase shift data for performing phase shift, a plurality of continuous pixel clocks are used as a data area, data within an effective scanning period is divided into a plurality of areas, and phase shift data is set for each area. As a result, the amount of data can be reduced as compared with the case of correcting the main scanning position shift by providing phase shift data for each pixel.
[0068]
FIG. 10 is obtained by adding an effective write start position detection signal to FIG. 6. By synchronizing both before the effective write area start position and at the effective write start position, FIG. Compared with the first embodiment, the dot position can be corrected with high accuracy in the effective writing area.
[0069]
FIG. 41 shows a specific example of the data setting method for the data area in the present invention.
As described above, the example of FIG. 41 is an embodiment in which the pixel clock 30PCLK is defined as one data area, and shows an embodiment in the case where a phase shift of −3/8 PCLK is performed in this data area. It is. When the phase shift resolution of the pixel clock is ± 1/8 PCLK, by performing a phase shift of −1/8 PCLK with respect to the three pixel clocks in the data area, −3 with respect to the initial data area where no data is given. / 8PCLK main scanning dot position correction is possible. In the embodiment of correction 1 in FIG. 115, dot position correction of −1/8 PCLK is performed by phase shift data for measuring the timing of performing phase shift of −1/8 PCLK every 10 PCLK from the first dot in the data area. In the embodiment of correction 2, the dot of −1/8 PCLK is measured by the phase shift data that measures the timing of performing the phase shift of −1/8 PCLK every 10 PCLK from the fifth dot counting from the first dot of the data area as in the case of the corrected 1. Position correction is performed.
[0070]
As a method of generating phase shift data, there are a method of directly inputting as serial data from an external signal, and a method of providing a counter and performing phase shift at a constant interval. The former can generate a phase shift at a desired position in the data area, and it is easy to change the setting so that the phase shift pattern does not affect the image. In the latter case, by shifting the initial value of the counter as shown in correction 1 and correction 2 in FIG. 41, it is possible to prevent the phase-shifted portion from appearing as a vertical stripe image when writing continuous lines. It becomes.
[0071]
Further, for example, correcting the main scanning dot position shift for all image data increases the memory capacity, and increases the burden on the control system, such as cost and circuit scale. Also, the time spent for the correction process cannot be ignored. In the present invention, the above-mentioned problem can be solved by dividing the detection means into a plurality of data areas and setting the correction value of the phase data in each data area unit. As described above, the main scanning position deviation amounts shown in FIGS. 6A to 6C show the main scanning position deviation amount on the vertical axis and the image height ratio on the horizontal axis. For example, when the main scanning dot position deviation on the lookup table is represented in FIG. 6A based on the scanning time between two points measured during the printing operation, FIGS. ), The entire image data is divided into a plurality of areas, and the representative value (average value, etc.) of the main scanning dot position shift amount of each data area is used as a correction value, without increasing the memory capacity. It is possible to correct the dot position deviation satisfactorily. Here, for example, when the phase of the pixel clock is shifted in units of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%, and in the case of 1200 dpi writing, the main write within the effective writing width. The scanning position deviation can be reduced to 2.6 μm (21.2 μm / 8). The larger the number of divisions, the better the correction. However, it is desirable to determine the optimal number of divisions from the constraints of memory capacity and correction processing time.
[0072]
Further, the present invention is configured to set the phase data for each data area,
For example, the data amount can be reduced as compared with the case where phase data is phase-shifted for each pixel clock. This will be described with reference to the embodiment of FIG.
[0073]
In FIG. 6B, the effective scanning period is divided into 22 data areas, and the phase data is set so that the linearity at the median value of the divided data areas becomes zero. When the phase shift amount can be shifted by ± 1/8 PCLK and phase shift data is given for each pixel clock, three phase shift amount patterns (-1/8 clock, 0, +1/8 clock) are set. Requires 2 bits of data. If the effective scanning period is 300 mm at the time of 1200 dpi writing, one dot corresponds to about 21.2 μm, and the number of dots in the effective scanning period is 300 / 0.0212 = 14150 dots, and the number of dots in each data area is 14150 / 10 = 1415 dots.
[0074]
When correcting static characteristics such as scanning unevenness due to the characteristics of the scanning lens, it is necessary to provide data of 2 bits × 14150 dots = 28350 bits when phase data is set for each pixel clock.
[0075]
On the other hand, when phase data is set for each data area composed of 1415 dots, it is only necessary to know how many dots of 1415 dots should be phase-shifted, so the number of dots to be phase-shifted can be defined with 12 bits. At this time, since 2 bits are required to set three patterns of the phase shift amount, phase data in the data area can be set if 12 bits × 2 bits = 24 bits. Since there are 10 data areas, phase shift data for one line can be set with 24 bits × 10 = 240 bits, so the dot position is about 8% of the memory capacity compared to the case where phase data is set for each pixel clock. Deviation correction is possible.
[0076]
According to the present invention, when the pixel clock generation device is made into an IC or an IP, the phase data memory is greatly reduced, the chip size is reduced, and the cost is reduced.
[0077]
Next, referring to FIG. 5 and FIG. 9, the effective scanning start determination position for determining the effective scanning range start position and the effective scanning start determination position for the effective scanning area that is an effective data writing period on the scanned medium. A description will be given of an embodiment in which a portion between synchronization signal detection positions for detecting a synchronization signal for outputting a clock is set in one data region as an effective write start determination region.
[0078]
In FIG. 5, a case is considered in which a light beam output from a light source repeatedly scans as scanning light in a horizontal arrow direction. The scanning light is periodically scanned, and first passes through the detection means 1 on the left side of the scanned medium in the figure after the start of scanning. At this time, by using a light detection element such as a PD (detector 101 in FIG. 1) as the detection means, a PD detection signal can be obtained when the detection means passes through the scanning light. After the scanning light passes through the detection means 1, it scans the scanned medium, then passes through the detection means 2, and a PD detection signal is obtained by using the same light detection element (detector 102 in FIG. 1) as the detection means 1. Is obtained.
[0079]
In a normal image forming apparatus, a phase synchronization detection signal is used in which the PD detection signal is inverted and the signal falls immediately after the synchronization sensor is input. Here, the signal that becomes HI (high) in the falling period from the detection means 1 to the detection means 2 of the phase synchronization detection signal is set to WE1, and the area on the scanned medium as an effective scanning range is set as the effective scanning range. Is a write start position, and the detection means 2 side is a write end position, a signal that becomes HI between both positions is WE2. At this time, in order to accurately determine the writing start position, 2000 dots from the rising edge of the WE1 signal are set as a writing start position correction area, and phase data is given to correct dot position deviation due to the optical system and deflector. Thus, it is possible to set the writing start position with high accuracy. Similarly, in order to determine the writing end position with high accuracy, the writing end position correction area from the falling edge of the WE1 signal to 2000 dots before is set as the writing end position correction area, and the phase data is provided so that the writing end position is as accurate as It is possible to set the write end position. Further, by setting the data area and giving the phase shift data within the effective scanning period between the writing start position and the writing end position, the data amount and the memory can be reduced.
[0080]
The embodiment of FIG. 9 is an example in which detection means (detector 103 of FIG. 8, reflection member 211 of FIG. 13) is added to the effective writing start position in the embodiment of FIG. 6, and writing starts with higher accuracy. It is possible to set a position correction area and an effective writing range correction area, and it is possible to perform dot position correction with high accuracy.
[0081]
Next, referring to FIG. 6 and FIG. 10, an embodiment will be described in which phase data is set for each data area with the number of clocks in the data area being a substantially constant number to correct the main scanning position deviation. In this method, phase data is defined by defining a pixel clock that provides phase data as a fixed number of continuous data areas. By setting the number of pixel clocks constituting the data area to a fixed number, the maximum and minimum values of the phase shift amount in each data area become equal.
[0082]
As described above, FIG. 6B shows the data region divided into 22 equal parts in the effective scanning period in the optical system having the main scanning dot position shift characteristic shown in FIG. 6A. Assuming that the image height is ± 150 mm and 1200 dpi writing, the data area is 300 mm / 15 = 20 mm, and each data area is about 20 / 0.0212 = 943 dots from 21.2 μm per dot, and the phase shift resolution is ± When 1/8 PCLK is set, a phase shift of about ± 2.5 mm is possible in each data area when the phase shift is performed on all pixel clocks. Further, since the phase data defines the same number of pixel clocks in each data area, the size of the setting data is the same in each data area, so that the phase data can be generated with a simple memory and circuit configuration.
[0083]
Further, as shown in FIG. 10, when the detection means is provided at the effective writing start position, the dot position correction of the writing start position with higher accuracy can be performed with the same effect as described above.
[0084]
Next, similarly to FIGS. 6 and 10, an embodiment in which the data area is narrowed at an image height where the amount of change in the main scanning dot position deviation amount is large and the data area is widened at an image height where the amount of change is small will be described.
[0085]
FIG. 6C shows an example. As shown in FIG. 6C, a sensor or the like is provided on the scanned medium in the image forming apparatus in advance to measure the main scanning dot position deviation amount. In FIG. The pixel clock of the data area near the image height ratio 0 where the amount of change is small and the number of pixel clocks in the data area near the image height ratio ± 1 where the change amount of the dot displacement amount is large is small. By setting a large number, the number of data area divisions can be set so that the amount of deviation between the data areas can be reduced with the same or smaller number than in the case of equal division.
[0086]
In addition, as shown in FIG. 10C, when the detection means is provided at the effective writing start position, the dot position correction of the writing start position with higher accuracy can be performed with the same effect as described above. .
[0087]
Next, in the optical scanning device having a function of changing the length of the effective writing area into a plurality of patterns, the data is obtained when the effective writing start position is substantially the same position in common with the plurality of patterns regardless of the paper size. FIG. 16 shows an embodiment in which the data area is set so that the final data of the area is substantially the same position as the effective writing end position.
[0088]
Pattern 1 in FIG. 16 shows an example in which the effective writing area is one data area, and the data area start position is the effective writing start in each of the paper sizes B5, A4, B4, and A3. Although the position is substantially the same as the position and is common to each paper size, the data area end position is set to be substantially the same position as the position corresponding to each paper size.
[0089]
At this time, for example, even when the paper sizes are different, the division position by the data area and the position of the paper size are substantially the same position. Therefore, by correcting the dot position by giving phase data to each data area, High-precision correction according to the size is possible. As a result, the effective writing start position and the effective writing end position for each paper size can be set with high accuracy by correcting the dot position deviation by the optical system or the deflector.
[0090]
Further, pattern 2 in FIG. 16 shows an example in which the effective writing area is further divided into a plurality of areas. In this embodiment, as shown in the figure, the effective writing area is divided into nine areas, and the data area is switched at substantially the same position as the paper size. Thereby, the effective writing area is divided into a plurality of areas, and by matching the paper size, the effective writing start position and the effective writing end position in each paper size are reduced by the present invention with a small amount of data. It becomes possible to set with high accuracy by correcting the dot position deviation by an optical system or a deflector.
[0091]
Next, FIG. 17 shows an embodiment in which the end position of the data area to be used is changed based on the paper size information when the writing start position is substantially the same position as the effective writing start position regardless of the paper size. .
[0092]
In this embodiment, as shown in FIG. 17, the effective writing area is divided into a plurality of areas, and the data area is switched at substantially the same position as the paper size. Thereby, the effective writing area is divided into a plurality of areas, and by matching the paper size, the effective writing start position and the effective writing end position in each paper size are reduced by the present invention with a small amount of data. It becomes possible to set with high accuracy by correcting the dot position deviation by an optical system or a deflector.
[0093]
Next, when the center position of the effective writing area is substantially the same position as the midpoint of the effective writing area regardless of the paper size, the data area start position and end position are set according to the paper size. An example is shown in FIG.
[0094]
According to the present embodiment, when the middle point of the effective writing area is a fixed position common to a plurality of patterns, the initial data and the final data in the data area are abbreviated as the effective writing start position and the effective writing end position, respectively. By setting the data area so as to be the same position, it is possible to correct the effective writing start position, the effective writing end position, and the main scanning dot position deviation with high accuracy in accordance with the paper size.
[0095]
In FIG. 18, since the center position of the effective writing area is substantially the same regardless of the paper size, the distance from the detecting means 1 to the effective writing area varies depending on the paper size. For example, when the effective writing start position for the A3 paper size is set as the reference effective writing start position, the effective writing start position for each of the paper sizes B4, A4, and B5 is shifted in the scanning direction from the reference effective writing start position. It becomes the position. At this time, the data from the reference effective writing start position to the effective writing start position is set as one data area for each paper size, and dot position deviation correction is applied to the one data area, thereby reducing the effective writing start position depending on the paper size. The amount can be set with high accuracy.
[0096]
Further, by dividing the effective writing area for each paper size into a plurality of data areas, it is possible to perform highly accurate dot position deviation correction with a minimum amount of phase data for each paper size. In FIG. 18, the data area in the effective writing area is changed for each paper size (B5, A4, B4, A3), and dot position deviation correction can be performed with the minimum phase data according to the paper size. .
[0097]
Next, according to FIG. 18, when the center position of the effective writing area is substantially the same as the midpoint of the effective writing area regardless of the paper size, the data area is set to the effective writing start position and the maximum effective writing position. A description will be given of an embodiment in which a region before writing start and an effective writing region are divided.
[0098]
In this embodiment, when a light beam output from a light source is scanned on a scanned medium along a scanning direction by a deflector, an effective writing area which is an effective data writing period on the scanned medium, and an effective writing The write start position for determining the write area, the area for determining the write end position, the area from the write start side detection means 1 to the write start position, the write start position correction area, and the write end side detection means When the area from 2 to the write end position is defined as the write end position correction area, the area to which the phase data is given is further divided for each of the three types of areas.
[0099]
In FIG. 18, a case is considered in which a light beam output from a light source repeatedly scans as scanning light in a horizontal arrow direction.
Although the scanning light is periodically scanned, after the scanning is started, firstly, it passes through the detection means 1 on the left side of the scanned medium in the figure, and a PD detection signal is obtained from the detection means 1 when the scanning light passes. Thereafter, the scanning light scans the scanning medium, passes through the detection means 2, and similarly a PD detection signal is obtained. In an ordinary image forming apparatus, the PD detection signal is inverted and used as a phase synchronization detection signal in which the signal falls immediately after the signal input to the detection means. At this time, a signal that becomes HI in the falling period from the detection means 1 to the detection means 2 of the phase synchronization detection signal is written as WE1, and the area on the scanned medium as an effective writing area is written as the detection means 1 side. When the start position and the detection means 2 side are the write end position, a signal that becomes HI between both positions is WE2. At this time, in order to accurately determine the writing start position, for example, 2000 dots from the rising edge of the WE1 signal is set as a writing start position correction area, and phase data is provided to thereby prevent dot position deviation caused by the optical system or deflector. It is possible to correct and set the writing start position with high accuracy. Similarly, in order to accurately determine the writing end position, the writing end position correction area is set from the falling edge of the WE1 signal to 2000 dots before, and phase data is provided to provide the same as the writing start position. A highly accurate writing end position can be set.
[0100]
Further, in the effective writing area between the writing start position and the writing end position, a data area is set separately from the above two areas to give phase data, so that the entire apparatus has a writing start position correction area and a writing area. By reducing the number of data areas in the insertion end position correction area and reducing the number of data areas in the effective write area, a configuration in which the amount of data and memory are reduced can be achieved.
[0101]
Next, still another embodiment of the optical scanning device of the present invention is shown in FIG. In the present embodiment, similarly to FIG. 13, the reflected light on the first surface of the transparent member 206 such as flat glass is further reflected by the reflecting members 209, 210, and 211 arranged in the scanning direction, so that one detector is used. This is detected at 105. In FIG. 19, the laser emitted from the semiconductor laser 201 is deflected and scanned as the polygon mirror 204 rotates, forms a light beam spot on the scanned medium (photosensitive member) 207 via the scanning lens, and electrostatically A latent image is formed.
[0102]
In FIG. 19, as detection means, reflecting members 209, 210, and 211 are provided at two places on the writing start position side and the ending position side, and at one place substantially in the center of the writing area, and these reflecting members 209, It is composed of one detector 105 that receives the beams reflected by 210 and 211, and measures the scanning time that the beam deflected and scanned by the deflector of the polygon mirror 204 crosses the light detection means, thereby detecting the dot position deviation. In the control unit 110, based on the measured variation amount of the scanning time, the correction amount of the main scanning dot position is set from a pre-recorded lookup table or the like. An image clock phase-shifted by the pixel clock generation unit 120 is generated based on the correction amount data, and an LD drive signal generation unit 140, an LD drive unit are generated based on the image data generated by the image processing unit 130 based on the pixel clock. By controlling the light emission time of the semiconductor laser 201 via 150, the dot position on the scanned medium can be controlled to an arbitrary position.
[0103]
As described above, by configuring the pixel clock generation unit that changes the cycle of the pixel clock based on the phase data that indicates the transition timing of the pixel clock, the cycle of the specific pixel clock is changed by the phase data. Therefore, the main scanning dot position shift can be corrected with high accuracy.
[0104]
An embodiment of a method for correcting the main scanning dot position in the optical scanning device of FIG. 19 to an arbitrary position is shown in FIGS.
20 and 21, in a pixel clock generation device having a function of generating a pixel clock after a certain period from the fall of the phase synchronization signal that sets the write start timing, the pixels within the effective scanning period serving as the actual image region When the semiconductor laser is modulated based on the clock signal and the emitted light of the semiconductor laser forms an electrostatic latent image on the photoconductor through the optical system, the pixel clock on the photoconductor is the main scan by the deflector or the optical system. Directional dot position deviation occurs. At this time, the effective scanning period indicating the main scanning direction varies in length depending on the optical system. In this example, when the center of the image height is 0, the maximum and minimum values of the image height are defined as the image height ratio 1 and -1, respectively. is doing.
[0105]
FIGS. 20A to 20C are diagrams of the main scanning position deviation amount with the vertical axis representing the main scanning position deviation amount and the horizontal axis representing the image height ratio. The optical system characteristic of FIG. 3A has a characteristic that the change amount is large at a place where the image height is high, and the change amount is small when the image height is near zero. Since the pixel clock generation circuit having a phase shift function capable of shifting the phase of the pixel clock in units of a fraction of the clock for each clock, the main scanning position of each pixel can be shifted in units of ± 1 / dot. In principle, in the case of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%. In the case of 1200 dpi writing, the main scanning position deviation within the effective writing width can be reduced to 2.6 μm (21.2 μm / 8).
[0106]
The detector in FIG. 19 and other examples includes, for example, a triangular PD as shown in FIG. 22B, or a triangular slit arranged just before the PD, and a square shown in FIG. 22A. It is composed of a combination of PDs. At this time, the position in the sub-scanning direction can be measured by detecting the time (t1 and t2 in the figure) during which the PD detects the beam, and each reflection member can be detected by detecting the rising due to the beam entering the PD. It is possible to measure the time difference of beam detection by.
[0107]
For example, in the embodiment of FIG. 19, the detection time difference in the detection means (detector 105) by reflected light through the reflecting member 1-reflecting member 3 is t3, and the detecting means by reflected light through the reflecting member 3-reflecting member 2 When the detection time difference in t is t4, the synchronization detection time is highly accurate by comparing the measured time difference (t3, t4) with the output count number of the counting means that counts the high frequency clock from each detection start time. The magnification error in the main scanning direction can be corrected based on the synchronization detection time.
[0108]
Note that the accuracy of synchronization detection increases as the number of reflection or reflection / transmission members arranged in the main scanning direction increases, so that the dot position at the detection means can be corrected with higher accuracy. It is desirable to set the optimal number because the data may increase or the processing becomes heavy.
[0109]
FIG. 23 shows an example thereof. FIG. 23 shows an embodiment in which the number of the three reflecting members 209, 210, 211 in FIG. 19 is increased to 6, and the reflected light from each of the reflecting members 1 to 6 shown in 221 to 226 is detected. As the light beam collected by (detector 105) and deflected and scanned by the deflector is scanned, the reflected light from each reflecting member is detected by the detecting means. In this embodiment, the plurality of reflecting members 221 to 226 and one detector 105 are arranged on substantially the same support body 230, so that the positions of the reflecting member and the detecting means due to temperature fluctuations and environmental fluctuations. Thus, it is possible to reduce the variation of the orientation, and it is possible to detect the main scanning dot position and correct the main scanning dot position deviation with higher accuracy.
[0110]
Further, as the reflecting member having a function of reflecting the light beam in FIG. 19 and other examples, there is a mirror or the like which has a reflecting material on one surface of a transparent member such as glass or plastic, which reflects and transmits the light beam. Examples of the reflection / transmission member having both functions include transparent members such as glass and plastic. As the shape of these members, the reflection and transmission direction of the light beam can be easily controlled by adopting a parallel plate shape. In the case of using only a reflecting member, it is preferable to use a member having high reflectivity, and in the case of using a reflecting / transmitting member, it is desirable to use a member having high reflectivity and high transmittance.
[0111]
Another embodiment of the optical scanning device of the present invention is shown in FIG. The present embodiment is an optical scanning device characterized in that a plurality of reflecting members or reflected or transmitted light beams from the reflecting / transmitting members have overlapping regions.
[0112]
As shown in FIG. 24, the reflected light reflected by the reflection / transmission member 206 is further reflected and transmitted by a plurality of reflection members and reflection / transmission members 209, 210, 211, and then to one detector 105. Led. A feature of the present embodiment is that the light beam is guided to the detection 105 after being reflected and transmitted through the plurality of reflection / reflection / transmission members 209, 210, and 211. With this configuration, the reflection / reflection / transmission member 209 is configured. , 210, 211 and the detector 105 can be compactly configured, which leads to downsizing of the optical scanning device.
[0113]
In the configuration of FIG. 24, the number of times the luminous flux is transmitted through the reflection / transmission member by the transmitted luminous flux differs depending on the configuration having the region where the transmitted luminous flux overlaps, and as a result, the detection signal at the detector based on the transmittance of the reflection / transmission member. Will have different amplitude values. Therefore, taking into consideration the transmittance of the reflecting / transmitting member, the detection signal obtained from the reflected light from the reflecting / transmitting member having a large number of times of transmission is corrected for each image by greatly correcting the signal amplitude by the amount of attenuation of the light amount due to the transmission. This is to detect the synchronization detection signal at high accuracy.
[0114]
Next, with reference to FIG. 25, it will be described that it is necessary to correct the amplitude of the detection signal for each light beam when there are regions where the light beams traveling from the plurality of reflection / transmission members to the detector overlap. The configuration of FIG. 25 is to detect the scanning light beam at three positions where it is reflected by the reflecting member 1, the reflecting / transmitting members 2, 3 as in the case of FIG. Here, let 209, 210, 211 and the optical path length of the light beam incident on the detector 105 through each member be optical path lengths L1, L2, L3, respectively. At this time, the light beam having the optical path length L2 is reflected by the reflection / transmission member 2 of 210 directly into the detector 105, but the light beam having the optical path length L3 is reflected by the reflection / transmission member 3 of 211, After passing through the reflection / transmission member 2 210, the light enters the detector 105. Similarly, the light beam having the optical path length L1 is reflected by the reflection member 1 209, then passes through the reflection / transmission members 3 and 2 211 and 210, and then enters the detection means. Therefore, when the transmittance of the reflecting / transmitting members 2 and 3 is T2 and T3 (T2 and T3 <1), respectively, the light flux having the optical path length L3 is T2 times, and the light flux having the optical path length L1 is T2 × T3 times the light quantity. Thus, when the signal is detected by the detecting means, the amplitude value of the signal that is originally detected is supposed to be constant, but the transmittance is reduced.
[0115]
For this reason, it is considered that the rise of the synchronization detection signal, the fall of the fall characteristic, the synchronization detection time shift, and the like are caused by the decrease in amplitude. In the present invention, in order to improve the above-mentioned problem, a highly accurate synchronization detection is performed by correcting a decrease in the amplitude of the signal caused by transmission through the reflection / transmission member, and a highly accurate main scanning dot position is determined based on the synchronization detection signal. Deviation correction is performed.
[0116]
In the embodiment of FIG. 19, the reflecting members 209, 210, 211 and the detection are made so that the optical path lengths of the light beams until they enter the detector 105 through the reflecting members 209, 210, 211 are substantially the same. With the arrangement in which the device 105 is arranged, it is possible to correct the main scanning dot position deviation with high accuracy without causing an error such as a time difference when passing through each reflecting member.
[0117]
Further, in the configuration of FIG. 19 or FIG. 24, the scanning light scans each reflection member or reflection / transmission member at the detection timing of the detection signal obtained by the light beam traveling from the plurality of reflection members or reflection / transmission members to the detector. Correction can be performed for each detection signal obtained at this time. For example, in the case of the configuration of FIG. 19, when the optical path length of the light beam guided to the detector 105 through the reflecting members 1, 2, and 3 of 209 to 211 is L1, L2, and L3, only the difference in optical path length is By shifting the timing of the synchronization detection signal detected by the detector 105, a highly accurate synchronization detection signal can be obtained. In the case of the configuration of FIG. 24, when the optical path length is L1>L2> L3 in FIG. 25, the timing of L1 and L2 is corrected by the optical path difference from L3 using L3 as a reference signal, thereby achieving high accuracy. Main-scanning dot position deviation correction can be performed.
[0118]
Next, a method for correcting the detection timing based on the detection timing at the image height having the longest optical path length in the optical scanning device of FIGS. 19 and 24 will be described with reference to FIGS.
[0119]
In FIG. 25, when L1, L2, and L3 are set in order from the longest optical path length, the relationship of L1>L2> L3 is established. In addition, detection signals obtained by the detection means when the reflection and reflection / transmission members 1, 2, and 3 are scanned with light are referred to as detection signals 1, 2, and 3, respectively. At this time, as shown in FIG. 26, when the detection signal in L1 is used as a reference signal, the detection signals of the light beams in L2 and L3 are advanced by td2 and td3, respectively, by the difference in optical path length. Therefore, it is possible to obtain the synchronization detection signal with reduced accuracy by delaying the detection signals by L2 and L3 with respect to the detection signal by L1, thereby reducing the influence of the time difference due to the optical path length. As a result, the main scanning dot position shift amount can be corrected with high accuracy based on the highly accurate synchronization detection signal.
[0120]
FIG. 28 shows an example of the scanning optical system in the optical scanning device of FIG. In this embodiment, the beam splitter 206 'separates and detects the light beam directed to the scanned surface 209 and the light beam directed to the detecting means into light beams in different directions. In the present embodiment, a reflection or reflection / transmission member 208, 212 is added.
[0121]
The beam splitter 206 ′ is formed by joining two pairs of right-angled triangular prisms, and the joint surface is a half mirror surface. A part of the light incident on the beam splitter is transmitted through the half mirror surface, and the transmitted light travels straight and scans the scanned medium. On the other hand, the light reflected by the half mirror surface is bent downward as shown in FIG. 24B to form reflected light. By separating the light beam scanned on the scanned medium 207 and the light beam detected by the detector 105 by the beam splitter 206 ′, light beams in different directions can be detected simultaneously.
[0122]
With this configuration, the first scan of the laser beam on the scanned medium 207 by the rotation of the polygon mirror 204 and the reflected light from the half mirror surface of the beam splitter 206 ′ cause a different direction and position from the scanned medium surface. Since the second scanning is performed, the reflection and reflection / transmission means 1, 2, 3, 4, 5 of 208 to 212 are formed on the second scan line, and the reflected and transmitted light fluxes are detected by the detector 105. By detecting, a synchronization detection signal can be obtained with the rotational speed of the polygon motor.
[0123]
Next, FIG. 28 shows an embodiment of a scanning optical system in the optical scanning device of FIG. In this embodiment, as shown in FIG. 28, the light beam scanned at substantially the same position as the surface to be scanned is reflected by a plurality of reflection or reflection / transmission members 209, 210, 211 and detected by the detector 105. When a plurality of reflection or reflection / transmission members 209, 210, 211 are arranged in the main scanning direction, the distance between the reflection, reflection / transmission members at the extreme ends of 209, 210 is determined as the effective surface to be scanned. It is characterized in that it is configured to be substantially the same as the signal detection interval when scanning to the writing start position and end position.
[0124]
According to the present embodiment, as shown in FIG. 29, it is possible to detect the light beam in real time at the start and end timing of the effective writing area, and there is no effective writing area between the detection signal 1 and the detection signal 2. In addition, phase synchronization detection and main scanning dot position correction can be performed with high accuracy in real time.
[0125]
Also, the major difference from the other embodiments is that a time difference from the synchronization detection to the effective writing area occurs due to the configuration in which the effective writing area is accurately detected by the synchronization detection, and the main scanning dot position generated during that time difference occurs. High-precision main scanning dot position deviation correction can be performed without being affected by deviation or the like.
[0126]
Next, in the optical scanning device of FIGS. 19 and 24, a method of correcting the main scanning dot position by giving phase data to each data area composed of a plurality of units, with one period of the pixel clock as one unit. 21 will be described in detail.
[0127]
As described above, in FIG. 21, in the pixel clock generation device having a function of generating a pixel clock after a certain period from the fall of the phase synchronization signal that sets the write start timing, effective scanning that becomes an actual image region When the semiconductor laser is modulated based on the pixel clock signal within the period and the emitted light of the semiconductor laser forms an electrostatic latent image on the photosensitive member through the optical system, the electrostatic latent image on the photosensitive member is deflected by a deflector. And the dot position shift in the main scanning direction due to the optical system occurs. At this time, the effective scanning period indicating the main scanning direction varies in length depending on the optical system. In this example, when the center of the image height is 0, the maximum and minimum values of the image height are defined as the image height ratio 1 and -1, respectively. is doing.
[0128]
In the main scanning position deviation amounts shown in FIGS. 21A to 21C, the vertical axis represents the main scanning position deviation amount, and the horizontal axis represents the image height ratio. The optical system characteristic of FIG. 21A has a characteristic that the change amount is large at a place where the image height is high and the change amount is small when the image height is near zero. In addition, the pixel clock generation circuit with a phase shift function that can shift the phase of the pixel clock in units of a fraction of the clock for each clock shifts the main scanning position of each pixel by a fraction of a dot. Therefore, in principle, in the case of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%. In the case of 1200 dpi writing, the main scanning position deviation within the effective writing width can be reduced to 2.6 μm (21.2 μm / 8).
[0129]
At this time, in order to provide phase shift data for performing phase shift, a plurality of continuous pixel clocks are used as a data area, data within an effective scanning period is divided into a plurality of areas, and phase shift data is set for each area. As a result, the amount of data can be reduced as compared with the case of correcting the main scanning position deviation by giving phase shift data to each pixel.
[0130]
FIG. 41 shows a specific example of the data setting method for the data area in this embodiment, but the description thereof is omitted here.
[0131]
For example, when the main scanning dot position shift on the lookup table is represented in FIG. 21A based on the scanning time between two points measured during the printing operation, FIGS. As shown in Fig. 4, the entire image data is divided into a plurality of areas, and the representative value (average value, etc.) of the main scanning dot position deviation amount in each data area is used as a correction value, thereby increasing the dot without increasing the memory capacity. It is possible to correct the misalignment satisfactorily.
[0132]
Here, for example, when the phase of the pixel clock is shifted in units of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%, and in the case of 1200 dpi writing, main scanning within the effective writing width. The displacement can be reduced to 2.6 μm (21.2 μm / 8).
[0133]
Next, with reference to FIGS. 21 and 28, an embodiment will be described in which the data area is set in conjunction with detection timings of a plurality of reflection / transmission members and detectors.
As described above, FIG. 28 shows the reflected light from the transparent member 206 reflected by the reflection members 209, 210, 211 or the reflection / transmission members 1, 2, 3 in the optical scanning device of FIG. It is comprised with the detector 105 which detects this. The timing at which the reflection means 209, 210 or the reflected light from the reflection / transmission members 1, 2 is detected by the detection means is substantially the same as the timing at which the writing start and end positions of the effective writing area on the photosensitive band are scanned. A reflection or reflection / transmission member is arranged at the timing.
[0134]
The timing at which the reflected light from the reflection or reflection / transmission members 1 and 3 is detected by the detector is the write start position side correction area, and the timing at which the reflection light from the reflection or reflection / transmission members 3 and 2 is detected by the detector. Let us consider a case where each area is composed of 8000 dots as the write end position side correction area. At this time, the dot positions at the scanning start positions of the respective regions are synchronized with high accuracy by the detection signals from the detectors, but the clocks fluctuate between the detection signals due to variations in the optical system, deflector, and the like. Therefore, by giving phase shift data for each region, in this embodiment, for example, by giving phase shift data for performing phase shift by −1/16 dots for any 10 dots out of 8000 dots, It is possible to perform dot position correction with high accuracy for each region between detection means.
[0135]
In this embodiment, there are three reflection or reflection / transmission means for guiding the light beam to the detector. However, as the number of reflection, reflection / transmission members is increased, the dots at the member positions can be written with high accuracy. It becomes possible.
[0136]
For example, in FIG. 21, FIG. 21 (B) shows an example in which the detection means 1, 3 and 3, 3 are divided into 15 parts, respectively, and FIG. 21 (C) shows 9 between the detection means 1, 3 and 3, 2, respectively. This is an example of division. Increasing the number of divisions of the data area as shown in FIG. 21B reduces the amount of deviation between the data areas, and enables highly accurate dot position deviation correction. Similarly, when the number of areas is reduced by changing the division width of the data area as shown in FIG.
[0137]
Next, an embodiment in which phase data is corrected based on a scanning time during which a light beam traverses a plurality of detectors and reflection / transmission members will be described with reference to FIG.
In FIG. 21, in a pixel clock generation device having a function of generating a pixel clock after a certain period from the fall of the phase synchronization signal that sets the timing for starting writing, the pixel clock signal is converted into the pixel clock signal within an effective scanning period that becomes an actual image region. When the semiconductor laser is modulated on the basis of which the emitted light of the semiconductor laser forms an electrostatic latent image on the photoreceptor through the optical system, the electrostatic latent image on the photoreceptor is in the main scanning direction by a deflector or the optical system. Dot position deviation occurs. At this time, the effective scanning period indicating the main scanning direction varies in length depending on the optical system. In this example, when the center of the image height is 0, the maximum and minimum values of the image height are defined as the image height ratio 1 and -1, respectively. is doing.
[0138]
In the main scanning position deviation amounts shown in FIGS. 21A to 21C, the vertical axis represents the main scanning position deviation amount, and the horizontal axis represents the image height ratio. The optical system characteristic of FIG. 21A has a characteristic that the change amount is large at a place where the image height is high and the change amount is small when the image height is near zero. Since the pixel clock generation circuit having a phase shift function capable of shifting the phase of the pixel clock in units of a fraction of the clock for each clock, the main scanning position of each pixel can be shifted in units of ± 1 / dot. In principle, in the case of ± 1/8 dot shift, the linearity correction amount can be adjusted from 0% to 12.5%. In the case of 1200 dpi writing, the main scanning position deviation within the effective writing width can be reduced to 2.6 μm (21.2 μm / 8).
[0139]
FIG. 30 shows a configuration diagram of still another embodiment of the optical scanning device of the present invention. The present embodiment shows a configuration example of a multi-beam scanning device using a multi-beam light source configured by optically combining a plurality of semiconductor lasers or a monolithic semiconductor laser array as a light source of the optical scanning device of FIG. .
[0140]
In FIG. 30, n = 2 semiconductor lasers are used and arranged in the sub-scanning direction with the optical axis C of the collimating lens being symmetric. The semiconductor lasers 301 and 302 are laid out so that the optical axes of the collimating lenses 303 and 304 coincide with each other and have an emission angle symmetrical to the main scanning direction, and the emission axes intersect at the reflection point of the polygon mirror 307. A plurality of beams emitted from the respective semiconductor lasers 301 and 302 are collectively scanned by a polygon mirror 307 through a cylinder lens 308 and imaged on a photosensitive member by an fθ lens 310 and a toroidal lens 311. Print data for one line is stored in the buffer memory of the image processing unit 130 for each light source, read out for each surface of the polygon mirror, and recorded on two lines simultaneously.
[0141]
FIG. 31 shows a configuration diagram of an embodiment of a multi-beam light source unit. The semiconductor lasers 403 and 404 are individually cylindrical in mating holes 405-1 and 405-2 (not shown) formed on the back side of the base member 405 slightly inclined by a predetermined angle in the main scanning direction, in the embodiment, about 1.5 °. The heat sink portions 403-1 and 404-1 are mated, and the protrusions 406-1 and 407-1 of the holding members 406 and 407 are aligned with the notches of the heat sink portion so that the arrangement direction of the light emitting sources is aligned, and from the back side It is fixed with screws 412. Further, the collimating lenses 408 and 409 are adjusted in the optical axis direction so that the outer circumference thereof is aligned with the semicircular mounting guide surfaces 405-4 and 405-5 of the base member 405. It is positioned and glued so that it becomes a parallel light beam. In the embodiment, since the light beams from the respective semiconductor lasers are set to intersect within the main scanning plane as described above, the mating holes 405-1 and 405-2 and the semicircular mounting guides are formed along the light beams. The surfaces 405-4 and 405-5 are formed to be inclined. The base member 405 is engaged with the holder member 410 by the cylindrical engagement portion 405-3, and the screw 413 is screwed into the screw holes 405-6 and 405-7 through the through holes 410-2 and fixed. Configure.
[0142]
In the light source unit described above, the cylindrical portion 410-1 of the holder member is engaged with the reference hole 411-1 provided in the mounting wall 411 of the optical housing, the spring 611 is inserted from the front side, and the stopper member 612 is inserted into the cylindrical portion protrusion 410. The holder member 410 is held in close contact with the back side of the mounting wall 411 by engaging with -3. At this time, one end of the spring is hooked on the protrusion 411-2 to generate a rotational force with the center of the cylindrical portion as the rotational axis, and an adjustment screw 613 provided to lock the rotational force causes the rotation around the optical axis to be θ. Rotate the entire unit to adjust the pitch. The aperture 415 is provided with a slit for each semiconductor laser, and is attached to the optical housing to define the emission diameter of the light beam.
[0143]
FIG. 32 shows a second embodiment of the multi-beam light source unit, and shows an example in which the light beams from the semiconductor laser array 801 having four light emitting sources are combined using the beam combining means. Basic components are the same as those in FIG. 31, and a description thereof is omitted here.
[0144]
FIG. 33 shows a configuration diagram of still another embodiment of the optical scanning device of the present invention. In this embodiment, as the light source of the optical scanning device of FIG. 19, a configuration example of a multi-beam scanning device using a multi-beam light source composed of a plurality of semiconductor lasers optically synthesized or a monolithic semiconductor laser array. Show. The configuration of FIG. 33 is the same as that of FIG. 30, and the description is omitted until the multi-beam light source unit is the same as that of FIGS.
[0145]
Here, with the multi-beam scanning device of FIG. 33, one light beam emitted from two light sources is used as scanning light, and the other light beam is used as a reference, and the light beam polarized by the same polarizer is scanned into the scanned surface. Next, an embodiment will be described in which the reference light is guided to a detection surface different from the scanned light, and the phase is corrected using the reference light.
[0146]
In FIG. 33, a light beam emitted from a scanning light source semiconductor laser 302 serving as a light source for writing is deflected by a polygon mirror 307 via a collimator lens 304, a cylinder lens 306, etc., and passes through an fθ lens 308. Then, the light is incident on the photoreceptor 310 via the reflecting member 309. Here, separately from the light source 302 for writing, a light source for a reference light source 301 for detecting phase synchronization of a scanning signal is provided.
[0147]
This reference light source LD 301 emits a light beam in the same direction as the scanning light source LD in the main scanning direction, and is incident at an interval in the vertical direction (sub-scanning direction) on the same reflecting surface of the polygon mirror 307. Are arranged to be. Therefore, the light beam from the reference light source LD 301 is also deflected and scanned by the polygon mirror 307, passes through the fθ lens 308, and then is placed on the detected surface that is equivalent to the photosensitive member 310 via the transparent member 309. The light reflected by the 313 reflecting members 1, 2 and 3 scans the detector 314. A detection signal and a synchronization detection signal are obtained from the light beam scanned by the detector 314, and the main scanning dot position deviation amount can be corrected with high accuracy based on the time width of the synchronization detection signal.
[0148]
The light path length from the light source to the scanned medium in the emitted light from the writing light source 301 is L1, L2, L3, and the detector 314 from the light source in the emitted light from the reference light source 302 via the reflecting members 1, 2 and 3 When the optical path lengths up to are set to L1 ′, L2 ′, and L3 ′, the optical path lengths of both are arranged so as to be substantially the same optical path length, and therefore, a variation in scanning time error due to the optical path difference is received. In addition, based on the phase synchronization signal obtained from the reference light source and the detection means, dot position correction can be performed with high accuracy. In addition, by configuring a scanning light source that emits scanning light and a reference light source that emits reference light to have a light source of substantially the same wavelength, the error and fluctuation components of the scanning position caused by the wavelength difference of the light source are reduced, and high precision dots Position correction is possible.
[0149]
As a scanning light source that emits scanning light and a reference light source that emits reference light, for example, when a semiconductor laser is used as the light source, the light source is composed of the same lot so that the scanning position caused by the wavelength difference of the light source Error and fluctuation components are reduced, and dot position correction can be performed with high accuracy.
[0150]
In addition, by configuring the components in the same lot in the same lot in the above configuration, it becomes possible to configure a light source with a smaller wavelength difference, and reduce scanning position errors and fluctuation components caused by the wavelength difference of the light source. In addition, highly accurate dot position correction is possible.
[0151]
FIG. 34 shows an embodiment in which a semiconductor laser array having a scanning light source that emits scanning light and a light source having substantially the same wavelength as a reference light source that emits reference light is configured. In this embodiment, when the scanning light sources are LD1, LD2, LD3, and LD4 and the reference light source is LD5, the light flux separation of the reference light source is increased by increasing the distance between the scanning light source and the reference light source. It makes the structure which makes it easy. With this configuration, it is possible to reduce scanning position errors and fluctuation components caused by the wavelength difference of the light source, and to perform highly accurate dot position correction.
[0152]
FIG. 35 shows an embodiment in which the optical scanning apparatus and the image forming apparatus described so far are applied to a tandem color machine which is a multicolor image forming apparatus having a plurality of photoconductors. However, FIG. 35 shows only a configuration example of a sub-scanning section related to the present invention. In FIG. 35, 501 is a polygon mirror, 502 is a scanning lens 1, 503 and 504 are folding mirrors, 505 is a scanning lens 2, 506 is a folding lens, 507 is a translucent member, 508 is a photoreceptor, and 509 is a detector. . The same applies to other optical systems. Reference numeral 510 denotes an intermediate transfer belt.
[0153]
In FIG. 35, each of the scanning optical systems corresponding to the four scanned surfaces is provided by arranging the polygon mirror 501 in two stages and arranging the scanning optical system vertically, and further arranging the scanning optical system centering on the deflection means. An optical system is installed. At this time, the beam is guided to each detector by mirrors arranged on both sides outside the effective angle of view. Further, a pattern image for measurement is formed on the intermediate transfer level 510, and a dot position for each color is measured using a plurality of sensors provided for each scanning optical system. At this time, the dot position correction corresponding to the change with time can be performed with high accuracy by performing the correction as described above.
[0154]
The tandem color machine requires separate photoconductors corresponding to cyan, magenta, yellow, and black colors, and the optical scanning optical system forms a latent image through different optical paths corresponding to the photoconductors. Therefore, the main scanning dot position shift generated on each photoconductor often has different characteristics. Therefore, by deploying the optical scanning device described so far to a tandem color machine, it is possible to obtain a high-quality image in which the main scanning dot position deviation is well corrected. In particular, in terms of image quality, an image with good color reproducibility can be obtained in which color misregistration between stations is effectively reduced.
[0155]
For example, in a tandem color machine, when color misregistration between stations occurs on the order of several tens of μm, the main scanning position deviation is corrected by applying a phase shift in a pixel clock whose main scanning position deviation exceeds 1/8 dot. In the case of 1200 dpi, the amount of dot position deviation can be reduced to about 2.6 μm (21.2 μm / 8) corresponding to 1/8 dot.
[0156]
In the present invention, if the shift amount is given to the pixel data for each dot, the number of bits of the pixel data increases and the data transfer becomes heavy. High-precision dot position correction can be performed without giving complicated data.
[0157]
【The invention's effect】
As is apparent from the above description, according to the present invention, it is possible to perform measurement for enabling dot position correction over time with a low cost, space saving, and simple configuration, and highly accurate dot position correction is possible. It is possible to provide a possible optical scanning device and image forming apparatus.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of an optical scanning device of the present invention.
FIG. 2 is a diagram for explaining dot position deviation of an optical scanning optical system.
FIG. 3 shows an embodiment of a timing diagram according to the present invention.
FIG. 4 is a diagram illustrating main scanning dot position deviation according to the present invention.
FIG. 5 shows another embodiment of a timing diagram according to the present invention.
FIG. 6 is a diagram illustrating main scanning dot position deviation according to the present invention.
FIG. 7 is a diagram illustrating a configuration example of a photodetector.
FIG. 8 is an overall configuration diagram showing another embodiment of the optical scanning device of the present invention.
FIG. 9 illustrates another embodiment of a timing diagram according to the present invention.
FIG. 10 is a diagram illustrating main scanning dot position deviation according to the present invention.
FIG. 11 is a diagram showing an embodiment of an optical scanning optical system according to the present invention.
FIG. 12 is a diagram illustrating a configuration example of an array of detectors.
FIG. 13 is an overall configuration diagram of another embodiment of the optical scanning device of the present invention.
FIG. 14 is a diagram showing another embodiment of the optical scanning optical system according to the present invention.
FIG. 15 is a diagram illustrating a configuration example of an arrangement of a reflection / transmission member and a detector.
FIG. 16 shows another embodiment of a timing diagram according to the present invention.
FIG. 17 is a diagram showing an example of data area division according to the present invention.
FIG. 18 is a diagram showing another embodiment of data area division according to the present invention.
FIG. 19 is an overall configuration diagram of another embodiment of the optical scanning device of the present invention.
FIG. 20 illustrates another embodiment of a timing diagram according to the present invention.
FIG. 21 is a diagram illustrating main scanning dot position deviation correction according to the present invention.
FIG. 22 is a diagram illustrating a configuration example of a detector.
FIG. 23 is a diagram illustrating a configuration example of an arrangement of a plurality of reflecting members and detectors.
FIG. 24 is an overall configuration diagram showing another embodiment of the optical scanning device of the present invention.
FIG. 25 is a diagram showing another configuration example of the arrangement of a plurality of reflection / transmission members and detectors.
FIG. 26 illustrates another embodiment of a timing diagram according to the present invention.
FIG. 27 is a diagram showing another embodiment of the optical scanning optical system according to the present invention.
FIG. 28 is a view showing still another embodiment of the optical scanning optical system according to the present invention.
FIG. 29 is a diagram for explaining main-scanning dot position deviation correction according to the present invention.
FIG. 30 is an overall configuration diagram showing another embodiment of the optical scanning device according to the present invention.
FIG. 31 is a diagram showing an example of a multi-beam light source unit.
FIG. 32 is a diagram showing another example of the multi-beam light source unit.
FIG. 33 is an overall configuration diagram of another embodiment of the optical scanning device according to the present invention.
FIG. 34 is a diagram illustrating a configuration example of a multi-laser head.
FIG. 35 is a diagram showing a configuration example of a main part of a tandem color machine to which the optical scanning device of the present invention is applied.
FIG. 36 is a block diagram of an embodiment of a pixel clock generator used in the present invention.
37 is a detailed block diagram of an embodiment of the pixel clock generation circuit in FIG. 36. FIG.
38 is an operation timing chart of FIG. 37. FIG.
FIG. 39 is a diagram showing a correspondence table between phase shift amounts and phase data.
FIG. 40 is a diagram illustrating a phase shift correction method in the pixel clock generation device.
FIG. 41 is a diagram illustrating an operation example of the pixel clock generation device.
FIG. 42 is a block diagram of another embodiment of a pixel clock generation device used in the present invention.
FIG. 43 is a diagram illustrating a configuration example of a conventional optical inspection device and image forming apparatus.
[Explanation of symbols]
100 High frequency clock generator
101,102 detector
110 Dot displacement detection / control unit
120 pixel clock generator
130 Image processing unit
140 LD drive signal generator
150 LD drive unit
200 Optical scanning optical system
201 Semiconductor laser
202 Collimator lens
203 cylinder lens
204 Polygon mirror
205 Scanning lens
206 Transmission member
207 photoconductor

Claims (29)

A light source, a deflecting unit for deflecting the light beam emitted from the light source, a light guide unit for guiding the light beam deflected by the deflecting unit to a surface to be scanned and a surface to be detected different from the surface to be scanned, and a high-frequency clock An optical scanning device comprising: a high-frequency clock generation unit that generates a pixel clock; and a pixel clock generation unit that generates a pixel clock based on a high-frequency clock output from the high-frequency clock generation unit and phase data indicating a phase shift amount of the pixel clock In
In the sensed surface, the a first detection signal the light beam detected position in the direction opposite to the scanning than effective writing start position on the scanned surface is detected upon scanning, the effective writing end position wherein, said detection position that is more in the scanning direction effective writing end position based on the second detection signal the light beam is detected when scanning, optical scanner and generates the phase data. A light source, a deflecting unit for deflecting a light beam emitted from the light source, a light guide unit for guiding the light beam deflected by the deflecting unit to a surface to be scanned and a surface to be detected different from the surface to be scanned, and a high-frequency clock An optical scanning device comprising: a high-frequency clock generation unit that generates a pixel clock; and a pixel clock generation unit that generates a pixel clock based on a high-frequency clock output from the high-frequency clock generation unit and phase data indicating a phase shift amount of the pixel clock In
In the sensed surface, the a first detection signal the light beam detected position in the direction opposite to the scanning than effective writing start position on the scanned surface is detected upon scanning, the effective writing end position wherein, the second detection signal and said light beam detection position in the effective writing starting position and substantially the same position where the light beam a detection position that is more in the scanning direction the effective writing end position is detected when scanning An optical scanning device that generates the phase data based on a third detection signal detected when scanning is performed. The optical scanning device according to claim 1 or 2,
Wherein the light beam scanning the scan surface substantially the same position, the optical scanning device, characterized in that it comprises a detecting means for obtaining the detection signal by detecting a plurality of detecting portions arranged on the detected surface. The optical scanning device according to claim 1 or 2,
A light beam to scan the substantially same position as the surface to be scanned, wherein it has a detecting means for obtaining the detection signal is detected by one detector unit through a plurality of reflection or reflection and transmission member arranged in the detected surface An optical scanning device characterized by the above. The optical scanning device according to any one of claims 1 to 4 ,
An optical scanning device characterized in that phase data is given to each data area composed of a plurality of units, with one period of a pixel clock as one unit. The optical scanning device according to claim 2 .
In the sensed surface, wherein a time of the light beam position detection in from the opposite direction of the scanning effective writing start position on the scanned surface is scanned, the light beam position detection in the effective writing starting position and substantially the same position An optical scanning device characterized in that a data area is defined as an effective writing start position determination area between the detection positions when scanning is performed. The optical scanning device according to claim 2 .
An optical scanning device characterized in that phase data is set for each data region composed of an arbitrary number of continuous pixel clock signals. The optical scanning device according to claim 5.
An optical scanning device characterized in that when the change amount of the main scanning dot position deviation is large, the division width of the data area is narrowed, and when the change amount is small, the division width of the data area is widened. The optical scanning device according to claim 5.
When the length of the effective write area can be changed to multiple patterns and the effective write start position is a fixed position common to the multiple patterns, the end of the data area is approximately the same position as the effective write end position. An optical scanning device characterized in that a data area is set in The optical scanning device according to claim 9.
An optical scanning device characterized in that, based on paper size information, the data area is set so that the end of the data area is substantially at the same position as the effective writing end position. The optical scanning device according to claim 5.
When the length of the effective write area can be changed to multiple patterns, and the midpoint of the effective write area is a fixed position common to the multiple patterns, the start and end of the data area are the effective write start position and the effective position, respectively. An optical scanning device characterized in that a data area is set to be substantially the same position as a writing end position. The optical scanning device according to claim 11.
When the light beam output from the light source is scanned on the scanned medium along the scanning direction by the deflector, a detection means for detecting the light beam on the writing start side and the writing end side is provided, and effective from each detection means. An optical scanning device characterized in that an area up to a writing area is an effective writing start position correction area and an effective writing end position correction area, respectively, and each area is configured as one data area. The optical scanning device according to claim 3 or 4,
An optical scanning device characterized in that a plurality of detection units or a plurality of reflection or reflection / transmission members and detection units are held on substantially the same support. A light source, a deflecting means for deflecting the light beam emitted from the light source, and the light guide means for guiding each of the different detected surface and the surface to be scanned and the scanned surface the deflected light beam by said deflection means, the object Detection means for detecting a light beam scanning substantially the same position on the detection surface as the surface to be scanned by a single detection unit via a plurality of reflection or reflection / transmission members; a high frequency clock generation means for generating a high frequency clock; In an optical scanning device comprising: a pixel clock generation unit that generates a pixel clock based on a high-frequency clock output from the high-frequency clock generation unit and phase data indicating a phase shift amount of the pixel clock;
An optical scanning device characterized in that the phase data is generated based on a scanning time during which a light beam crosses the plurality of reflecting or reflecting / transmitting members. The optical scanning device according to claim 14.
An optical scanning device having a region in which light beams traveling from a plurality of reflecting or reflecting / transmitting members to a detecting unit overlap. The optical scanning device according to claim 14 or 15,
An optical scanning device having a region where light beams traveling from a plurality of reflection or reflection / transmission members to a detection unit overlap, and performing amplitude correction of a detection signal for each light beam. The optical scanning device according to claim 14.
An optical scanning device characterized in that the optical path lengths of light beams traveling from a plurality of reflection or reflection / transmission members to a detection unit are substantially the same. The optical scanning device according to claim 14.
The detection timing of the detection signal obtained by the light beam traveling from the plurality of reflection / reflection / transmission members to the detection unit is corrected for each detection signal obtained when the scanning light scans each reflection / reflection / transmission member. An optical scanning device. The optical scanning device according to claim 18, wherein
An optical scanning device characterized in that a signal detection timing for detecting a light beam having the longest optical path length through a reflection or reflection / transmission member is set as a reference signal for detection timing. The optical scanning device according to any one of claims 14 to 19,
The light guide means is constituted by light beam splitting means for dividing the light beam deflected by the deflector to guide the surface to be scanned and a detected surface different from the scanned surface, respectively. apparatus. The optical scanning device according to any one of claims 14 to 19,
The light source comprises two types of light sources that respectively emit scanning light and reference light.
The deflecting unit deflects a light beam composed of scanning light and reference light emitted from the light source,
The light guide means guides the scanning light to the scanned surface and the reference light to the detected surface different from the scanned surface, among the light beams deflected by the deflecting means,
The detection means makes the reference light that scans substantially the same position on the detection surface as the surface to be scanned enter a single detection unit via a plurality of reflection or reflection / transmission members,
The optical scanning device characterized in that the phase data is generated based on a scanning time that the reference light crosses the detection unit . The optical scanning device according to any one of claims 14 to 21,
The interval between the members at the end in the scanning direction of the detection means is configured to be substantially the same as the signal detection interval when scanning to the effective writing start position and end position of the surface to be scanned. Optical scanning device. The optical scanning device according to any one of claims 14 to 21,
An optical scanning device characterized in that phase data is given to each data area composed of a plurality of units, with one period of a pixel clock as one unit. The optical scanning device according to claim 22 or 23.
An optical scanning device characterized in that a data area is set in conjunction with a plurality of detection timings. The optical scanning device according to claim 14.
An optical scanning device characterized in that a plurality of reflection or reflection / transmission members and a detection unit are held on substantially the same support. A light source; deflecting means for deflecting the light beam emitted from the light source; light guide means for guiding the light beam deflected by the deflecting means to a surface to be scanned and a surface to be detected different from the surface to be scanned; and the detection Detecting means for detecting a light beam that scans substantially the same position as the scanned surface on a surface with a single detection unit via a plurality of reflection or reflection / transmission members, high-frequency clock generation means for generating a high-frequency clock, and Based on the result of the comparison means, the counting means for counting the high-frequency clock output from the high-frequency clock generation means, the comparison means for comparing the count value of the counting means and the phase data indicating the phase shift amount of the pixel clock In an optical scanning device comprising pixel clock control means for performing pixel clock transition,
An optical scanning device, wherein the phase data is corrected based on a scanning time during which a light beam traverses the plurality of reflection or reflection / transmission members. 27. The apparatus according to claim 1, further comprising: a plurality of light sources; a deflecting unit that deflects light beams emitted from the plurality of light sources; and a light guide unit that guides the light beams deflected by the deflecting unit to a scanned medium. The optical scanning device according to any one of the above. An image forming apparatus comprising the optical scanning device according to any one of claims 1 to 27 and forming an image on a scanned object. An image forming apparatus comprising the optical scanning device according to any one of claims 1 to 27 and corresponding to a tandem color machine having a plurality of scanned media.

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