KR100322586B1 - Optical scanning system of printing machine - Google Patents

Abstract

An optical scanning system of a printing press is disclosed. The optical scanning system includes a optical scanning unit for scanning light to a circulating photosensitive medium, a first photodetector for detecting a part of light emitted from the optical scanning unit to detect a power of light emitted from the optical scanning unit, and a optical scanning unit. A second photodetector provided to detect light emitted from the photoreceptor unit to a position outside the image recording area set on the photosensitive medium to synchronize the start of image scanning of the photosensitive media; Comprising a light power of the unit, and according to the calculated optical power value is provided with a light scanning control unit for correcting the light output synchronization timing for the electrical signal output in response to the light received from the second photodetector to drive the light scanning unit . According to the optical scanning system of such a printing machine, an image writing error can be reduced by correcting a scanning start time corresponding to image information in response to fluctuations in power of light emitted from the optical scanning unit.

Description

Optical scanning system of the printing press

The present invention relates to a optical scanning system of a printing press, and more particularly, to detect a part of the light emitted from the optical scanning unit and synchronize the start time of scanning into the image writing area set on the photosensitive medium. It relates to the optical scanning system of the printing press which can correct the timing of the optical scanning in accordance with the change.

Referring to FIG. 1, which shows a light scanning system employed in a conventional printing press, the light scanning system includes a light detector 16, a light scanning unit 20, and a light scanning control unit 30.

The optical scanning unit 20 having a light source 21, a rotating mirror 22, and a lens unit 23 has a photosensitive belt circulating by rollers 11, 12 and 13 at a fixed position. The light is scanned in the width direction of 14).

The photodetector 16 is arranged to receive the light emitted from the photoreceptor unit 20 between the edges of the photosensitive belt 14 at a position outside the photosensitive belt 14.

The optical scanning controller 30 controls the driving of the optical scanning unit 20 by using a pulse output from the photodetector 16 in response to light reception.

This conventional optical scanning system has been operated as follows in order to allow image information to be written from the tip of the image writing area D set in the central portion of the photosensitive belt 14.

First, while driving the motor 24 to rotate the rotating mirror mirror 22 at a constant speed, the light source 21 is driven so that light is continuously emitted from the light source 21. In this process, an electrical signal corresponding to the light reception from the photodetector 16 is input to the optical scanning controller 30. The optical scanning controller 30 compares the electrical signal with a set threshold using a comparator (not shown) provided therein. At this time, the comparator outputs a pulse signal corresponding to the electric signal section of the set threshold or more. The optical scanning control unit 30 determines the end point of the pulse signal as the time point at which the light emitted from the optical fiber unit 20 arrives at the edge of the photosensitive belt 14, and the center of the photosensitive belt 14 from the end point of the pulse. The driving of the light source 21 is stopped for a set waiting time corresponding to the time when light output from the optical scanning unit 20 should be started to reach the light at the tip of the image information writing area D set in the portion. . Then, after the waiting time has elapsed, the driving of the light source 21 is started so that an optical signal corresponding to the video data is emitted.

In this driving method, one waiting time measured and obtained for the circulating motion of the photosensitive belt 14 is set, and the optical scanning controller 30 sets the signal output from the photodetector 16. After stopping the driving of the light source 21 temporarily from the end of the pulse signal obtained in comparison with the threshold value, the driving of the light source 21 corresponding to the video data is started after the set waiting time. In general, the light output power of the light source 21 is varied according to the ambient temperature, the use time. When the power of the light emitted from the light source 21 is changed in this way, as shown in FIG. 2, the received signal level output from the photodetector 16 also varies according to the power of the incident light. Accordingly, when the light reception signals are compared with only a predetermined threshold value, the widths P1, P2, and P3 of the pulses also vary according to the powers I1, I2, and I3 of the incident light. As a result, according to the conventional optical scanning control method, when the power of the light emitted from the light source 21 is out of the set value, the dash set for the time delay from the end of the pulse to the start of image scanning corresponding to the video data is set. The light emitted from the light source 21 after the time reaches the position beyond the tip of the image writing area of the photosensitive belt 14.

Therefore, according to the image scanning start method corresponding to the video data of the optical scanning unit 20 under the control of the optical scanning control unit 30, the photosensitive belt 14 according to the power fluctuation of the light emitted from the light source 21. There arises a problem that the image writing leading position on the image is changed.

SUMMARY OF THE INVENTION The present invention was devised to solve the above problems, and a printer for correcting image scanning timing so that image information can be written from the front end of an image writing area set on a photosensitive belt even if the power of light emitted from the light source is changed. Its purpose is to provide the optical scanning system.

1 is a perspective view showing a light scanning system of a general printing press,

2 is a graph showing the output voltage characteristics of the photodetector according to the power of the light emitted from the optical fiber unit.

3 is a perspective view showing a light scanning system of the printing press of an embodiment according to the present invention;

4 is a block diagram illustrating an example of a configuration of a light scanning controller of FIG. 3;

5 is a block diagram illustrating another example of the configuration of the optical scanning controller of FIG. 3;

6 is a perspective view showing a light scanning system of the printing press of the second embodiment according to the present invention;

7 is a perspective view showing the optical scanning system of the printing press of the third embodiment according to the present invention.

<Explanation of symbols for main parts of the drawings>

11, 12, 13, 41, 42, 43: roller 14, 44: photosensitive belt

16: photodetector 20, 50: Gwangju company unit

21, 51: light source 22, 56: rotating face mirror

23, 57: lens unit 24, 54, 58: motor

30, 60: optical scanning controller 45: the first photodetector

46: second photodetector 61, 71: comparator

62, 72: injection start determining unit 63, 73: lookup table

64, 74: Gwangju unit drive unit 81: beam splitter

In order to achieve the above object, the optical scanning system of the printing machine according to the present invention includes a optical scanning unit for scanning light to a circulating photosensitive medium; A first photodetector for detecting a part of the light emitted from the optical scanning unit to detect a power of the light emitted from the optical scanning unit; A second photodetector provided to detect light emitted from the photorejuvenation unit to a position outside the image writing area set in the photosensitive medium in order to synchronize the start of image scanning of the photorejuvenation unit; The optical power of the optical scanning unit is calculated from the light receiving signal output from the first photodetector, and the timing of light output synchronization with respect to the electrical signal output from the second photodetector corresponding to the light reception is calculated according to the calculated optical power value. And a light scanning control unit for correcting and driving the light scanning unit.

Hereinafter, the optical scanning system of the printing press according to a preferred embodiment of the present invention with reference to the accompanying drawings in more detail.

Figure 3 is a perspective view showing a light scanning system of the printing machine of one embodiment according to the present invention.

Referring to the drawings, the optical scanning system includes a optical scanning unit 50 for scanning light to the photosensitive belt 44 circulated by a plurality of rollers (41, 42, 43), and the optical scanning unit (50) And a light scanning control unit 60 for controlling the driving of the first photodetector 45, the second photodetector 46, and the optical scanning unit 50 to receive the emitted light.

The optical fiber unit 50 includes a light source 51, a scan disk 52, and a motor 54.

The scan disk 52 is formed in each of the divided regions with a diffraction pattern for deflecting the incident light beam at a predetermined angle by rotation. The scan disc 52 is rotated by a motor 54 which is a driving means.

A lens unit (not shown) may be interposed between the scan disk 52 and the photosensitive belt 44 to correct the deflection direction of light.

When the optical scanning unit 50 emits light from the light source 51 while rotating the scan disk 52 at a constant speed, the diffracted light passing through the scan disk 52 is deflected while sequentially changing the traveling path. Whenever the light beam emitted from the light source 51 tracks a partition region in which the same diffraction pattern is formed on the scan disc 52, the diffracted light is repeatedly deflected at the same position. Therefore, the light emitted from the light source 51 is scanned along the direction intersecting the traveling direction of the photosensitive belt 44, which is the photosensitive medium, by a predetermined angle, by the scanning disk 52 which is continuously rotated.

The optical scanning unit 50 exits from the light source 51 and comes along with the zero-order diffracted light 55 which is not deflected, in addition to the diffracted light sequentially deflected in a desired direction among the light incident on the scan disc 52.

The first photodetector 45 for detecting the power of the light output from the light source 51 is arranged to receive the zeroth order diffracted light 55.

The second photodetector 46 is arranged to receive light that is deflected and exited from the photoreceptor unit 50 between the edges of the photosensitive belt 44 at a position away from the photosensitive belt 44.

The optical scanning controller 60 calculates the optical power of the optical scanning unit 50 from the light receiving signal output from the first photodetector 45 and receives the light from the second photodetector 46 according to the calculated optical power value. The optical scanning unit 50 is driven by correcting the light emission synchronization timing with respect to the electrical signal output corresponding thereto.

An example of the configuration of the optical scanning controller 60 is shown in FIG. 4. Referring to the drawing, the optical scanning controller 60 includes a comparator 61, a scanning start determining unit 62, a lookup table (LUT) 63, and a optical scanning unit driver 64.

The comparator 61 outputs a result of comparing the received light signal output from the second photodetector 46 to the set comparison reference voltage Vref to the scan start determining unit 62.

In the lookup table 63, scanning synchronous correction time data corresponding to the fluctuation of the power of light output from the light source 51 is recorded. Referring to the process of obtaining the scan synchronous correction time data, first, output characteristics of a signal output from the second photodetector 46 while varying the power of the light source 51 are obtained. When the output characteristic of the signal output from the second photodetector 46 while varying the power of the light source 51 is obtained as shown in FIG. 2, the comparator (based on the output characteristic curve corresponding to the reference value of the optical power) A correction value corresponding to the set comparison reference value Vref of 61) is obtained. That is, when the output characteristic curve of the second photodetector 46 corresponding to the reference optical power is I ₂ and the comparison reference value is Vref, the correction value is + T1 for the optical power corresponding to the I ₁ curve, and I _In the case of the optical power corresponding to the _three curves, the correction value is -T3. At this time, the optical power values of the curves I ₁ , I ₂ , and I ₃ apply the power power value of the light output from the first photodetector 45. In this way, a correction value corresponding to each optical power value is obtained, and then a value obtained by adding the set time equal to the calculated correction value is recorded in the look-up table as the scanning synchronization correction time. When the second photodetector 46 is set at a position spaced a predetermined distance from the image writing area D as shown in FIG. The scan time correction time is applied to the time plus the time required for deflection.

The scanning start determining unit 62 calculates the optical power of the optical scanning unit 50 from the light receiving signal output from the first photodetector 45, and looks up from the light receiving end point of the pulse signal output from the comparator 61. The scanning start signal is output after the scanning synchronization correction time obtained from the table 63 corresponding to the optical power. The light output from the light source 51 is temporarily stopped from the comparator 61 after the input of the pulse signal until the generation of the scan start signal.

The optical scanning unit driver 64 drives the optical scanning unit 50 to start emission of light corresponding to the image information according to the scanning start signal.

When comparing the received signal output from the second photodetector 46 with the comparison voltage Vref set as described above, the scanned light is changed as the level of the received signal of the second photodetector 46 varies with the power of the received light. Although the end point of the light receiving pulse of the comparator 61, which is determined to arrive at the edge of the photosensitive belt 44, varies, the image writing set on the photosensitive belt 44 is corrected by correcting the time until the generation of the scan start signal. Image information can be written from the front end of the area D. Therefore, the image writing position error due to the optical powder variation is reduced, and in the case of a color printer employing a plurality of optical scanning units 50, it is possible to write an image for each color at a desired pixel position regardless of the optical powder variation. do.

Alternatively, the configured optical scanning controller is shown in FIG.

Referring to the drawings, the optical scanning controller 60 includes a comparator 71, a scanning start determining unit 72, a lookup table 73, and a optical scanning unit driver 74.

The comparator 71 compares the electrical level of the light reception signal output from the second photodetector 46 with the level of the set reference signal Vref. The comparison reference voltage Vref of the comparator 71 can be variably adjusted by the scanning start determining unit 72.

In the lookup table 73, the level adjustment value of the reference signal Vref of the comparator 71 to be applied corresponding to the optical power of the optical scanning unit 50 is recorded. When the reference signal level adjustment value of the comparator 71 corresponding to the optical power is described with reference to FIG. 2, the output characteristic curve of the second photodetector 46 corresponding to the reference optical power is I2 and compared. When the reference value is Vref, the reference signal level correction value is Vref1 for the optical power corresponding to the I1 curve, and the correction value is Vref3 for the optical power corresponding to the I3 curve. In this way, the reference signal level correction value corresponding to each optical power value is obtained, and the calculated correction value is recorded in the lookup table 73.

The scanning start determining unit 72 calculates the optical power of the optical scanning unit 50 from the light receiving signal output from the first photodetector 45, and compares the reference voltage Vref of the comparator 71 with the lookup table 73. ) Is adjusted to the reference signal level correction value corresponding to the optical power, and then the scan start signal is output after a set time from the light reception end point of the pulse signal output from the comparator 71.

The optical scanning unit driver 74 drives the optical scanning unit 50 to start emitting light corresponding to the image information according to the scan start signal.

6 shows an optical scanning system of the printing press of the second embodiment according to the present invention. Elements having the same function as in the above-described drawings are denoted by the same reference numerals.

In the illustrated optical scanning system, the configuration for detecting the power of the light source 51 is different from FIG. 3. Referring to the drawings, a beam splitter 81 for splitting light between the light source 51 and the scan disk 52 is provided.

The beam splitter 81 emits a part of the incident light to the scan disc 52, and a part of the beam to the first photodetector 45. Therefore, the optical scanning control unit 60 calculates the power of the light emitted from the light source 51 from the signal branched from the beam splitter 81 and output from the first photodetector 45, and corresponds to the optical power. Scanning synchronization correction is performed on the received signal of the two-photodetector 46. The optical scanning control unit 60 may take any one selected from FIGS. 4 and 5.

On the other hand, an example of another optical scanning system is shown in FIG. Elements having the same function as in the above-described drawings are denoted by the same reference numerals.

Referring to the drawings, the optical scanning unit 50 includes a light source 51, a rotating mirror 56, a lens unit 57, and a motor 58.

When the optical fiber unit 50 emits light from the light source 51 to the rotating mirror mirror 56 while rotating the rotating mirror mirror 56 at a constant speed, the rotating mirror mirror 56 rotates by the rotating mirror mirror 56. Light is scanned sequentially changing its deflection direction. The beam splitter 81 provided in the light source 51 and the rotating polygon mirror 56 emits a part of the light emitted from the light source 51 to the rotating polygon mirror 56, and the remaining part of the beam splitter 81 is the first photodetector 45. Exit to Therefore, the optical scanning controller 60 calculates the power of the light emitted from the light source from the signal branched from the beam splitter 81 and output from the first photodetector 45, and the second photodetector corresponding to the optical power. Scanning synchronization correction for the received signal at 46 is performed. The optical scanning control unit 60 may take any one selected from FIGS. 4 and 5.

In the examples shown, the photosensitive belt 44 circulated by the rollers 41, 42, 43 has been applied as an example of the photosensitive medium. Accordingly, the photosensitive belt 44 allows the second photodetector 46 to determine the arrival time of the edge of the photosensitive belt 44 of the scanned light in consideration of the weaving in which the photosensitive belt 44 moves to the left and right with respect to the traveling direction. (44) It is arranged across the edge. Then, the end points of the light receiving pulses of the comparators 61 and 71 corresponding to the time when the scanned light reaches the edge of the photosensitive belt 44 are corrected so that the image can be written from the tip of the image writing area D. After the set time, the scan start signal was generated. Although not shown differently, when a photosensitive drum is applied in which the trajectory of the photosensitive medium can be kept constant, the second photodetector 46 may detect the light scanned at a position outside the image writing area at a fixed position. In addition to the method of applying the scanning synchronous correction time by correcting by the same method as the basis of the end of the light receiving end, and applying the scanning synchronous correction time by correcting by the same method as the basis of the light receiving start point. You may also do it.

As described so far, the image writing error can be reduced by correcting the scanning start time corresponding to the image information in response to the fluctuation of the power of the light emitted from the optical scanning unit.

Claims (8)

A photowangsa unit for scanning light to the circulating photosensitive medium; A first photodetector for detecting a part of the light emitted from the optical scanning unit to detect a power of the light emitted from the optical scanning unit; A second photodetector provided to detect light emitted from the photorejuvenation unit to a position outside the image writing area set in the photosensitive medium in order to synchronize the start of image scanning of the photorejuvenation unit; The optical power of the optical scanning unit is calculated from the light receiving signal output from the first photodetector, and the timing of light output synchronization with respect to the electrical signal output from the second photodetector corresponding to the light reception is calculated according to the calculated optical power value. And a light scanning control unit for correcting and driving the light scanning unit. According to claim 1, wherein the optical scanning control unit A comparator configured to compare an electrical level of the light receiving signal output from the second photodetector with a set value and output the comparator; A lookup table in which scan synchronization correction time data corresponding to the optical power of the optical unit is recorded; The optical synchronization of the optical scanning unit is calculated from the light receiving signal output from the first photodetector, and the scan synchronous correction is obtained corresponding to the optical power calculated in the lookup table from the end of light reception of the pulse signal output from the comparator. A scan start determiner for outputting a scan start signal after time; And a light scanning unit unit for driving the light scanning unit so that emission of light corresponding to the image information is started in response to the scanning start signal. According to claim 1, wherein the optical scanning control unit A comparator configured to compare an electrical level of the light receiving signal output from the second photodetector with a set value and output the comparator; A lookup table in which scan synchronization correction time data corresponding to the optical power of the optical unit is recorded; The optical synchronization of the optical scanning unit is calculated from the light receiving signal output from the first photodetector, and the scanning synchronous correction obtained from the light receiving start point of the pulse signal output from the comparator corresponds to the optical power calculated from the lookup table. A scan start determiner for outputting a scan start signal after time; And a light scanning unit unit for driving the light scanning unit so that emission of light corresponding to the image information is started in response to the scanning start signal. According to claim 1, wherein the optical scanning control unit A comparator for comparing the electrical level of the received signal output from the second photodetector with a level of the set reference signal and outputting the comparable level; A look-up table in which a level adjustment value of the reference signal corresponding to the optical power of the optical unit is recorded; The optical power of the optical scanning unit is calculated from the received light signal output from the first photodetector, and adjusted so that the reference signal level of the comparator is a reference signal level value obtained corresponding to the optical power calculated in the lookup table. A scan start determiner for outputting a scan start signal after a set time from the light reception end point of the pulse signal output from the comparator; And a light scanning unit unit for driving the light scanning unit so that emission of light corresponding to the image information is started in response to the scanning start signal. According to claim 1, wherein the optical scanning control unit A comparator for comparing the electrical level of the received signal output from the second photodetector with a level of the set reference signal and outputting the comparable level; A look-up table in which a level adjustment value of the reference signal corresponding to the optical power of the optical unit is recorded; The optical power of the optical scanning unit is calculated from the received light signal output from the first photodetector, and adjusted so that the reference signal level of the comparator is a reference signal level value obtained corresponding to the optical power calculated in the lookup table. A scan start determiner for outputting a scan start signal after a set time from the light reception start time of the pulse signal output from the comparator; And a light scanning unit unit for driving the light scanning unit so that emission of light corresponding to the image information is started in response to the scanning start signal. The method of claim 1, The Gwangju company unit A light source; A scan disc having a hologram pattern capable of deflecting incident light by rotation; Drive means for rotating the scan disc; And the first photodetector is installed to detect a zero-order beam that exits from the light source and enters the scan disc and then proceeds without deflection. The method of claim 1, The Gwangju company unit A light source; A scan disc having a hologram pattern capable of deflecting incident light by rotation; Drive means for rotating the scan disc; A beam splitter for splitting incident light is further provided between the light source and the scan disc. And the first photodetector is installed to detect light directed from the beam splitter in a direction away from the scan disc. The method of claim 1, The Gwangju company unit A light source; A rotating polyhedron capable of deflecting incident light by rotation; And a driving means for rotating the rotating polygon mirror, A beam splitter for splitting incident light is further provided between the light source and the rotatable mirror, And the first photodetector is installed to detect light directed from the beam splitter in a direction away from the scan disc.