JP2006142506A - Method for adjusting laser beam scanning of color printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain an exposure timing quickly and surely with no regulation on the arrangement of light sources and without performing complicated control such as quantity of light control for the light source. <P>SOLUTION: In the method for adjusting laser beam scanning of a color printer, laser light sources 104G, B and R are lighted in this order at period T0 with predetermined time differences t1 and t2, and three color laser beams are modulated by an image signal before scanning and exposing the surface of a photosensitive material. Each laser beam is received by a single photosensor arranged on the outside of the exposure region and exposure operation by each laser beam is started by utilizing each light receiving timing. All laser light sources are lighted temporarily prior to print operation and when a single photosensor detects the laser beam from any light source, the light source of a leading laser beam is lighted in next scanning upon elapsing a predetermined time after first detection during current period. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, laser beams of three colors emitted from individual light sources and modulated by image signals of the respective colors are periodically transmitted with a predetermined time difference in a predetermined order through a scanning system. A color image is printed on the surface of the photosensitive material by scanning the surface of the photosensitive material, and each laser beam at a predetermined level is received by a single optical sensor arranged on the downstream side of the scanning system and outside the exposure area. The present invention relates to a laser beam scanning adjustment technique of a color printing apparatus that starts an exposure operation using each laser beam by using each light reception timing.

Conventionally, RGB light of three colors is emitted from each light source, modulated by an image signal of the corresponding color, and then main-scanned on the surface of the photosensitive material conveyed in the sub-scanning direction via a polygon mirror. An apparatus for printing is known. In the exposure operation, if the exposure start position by the laser beam on the photosensitive material surface and the modulation operation start timing of the image signal do not match for each color, a color shift occurs. It is known that a single photosensor is arranged and the start timing of the exposure operation for each color is determined using the timing at which the photosensor detects the laser beam of each color. By the way, it is known that the color development sensitivities of the respective colors of the photosensitive material do not necessarily match, and the output range of the laser light is set corresponding to each color development sensitivity and is not uniform. Therefore, in Patent Document 1, in view of the fact that a conventional single optical sensor cannot always detect all laser beams, a light source of a color that emits a maximum output is used as a laser beam from the light source. Has been proposed so that the exposure timing of each color is obtained by paying attention to this laser beam. Further, Patent Document 1 proposes, as another aspect, one that receives laser light from a predetermined light source after the output light amount of all light sources reaches a specified light amount.
JP-A-5-199372

  In Patent Document 1, in order to reliably obtain the exposure timing, the arrangement of the light sources is restricted, and the degree of freedom of arrangement is restricted. Further, it is necessary to separately control each light source to perform a lighting operation different from that during the normal exposure operation, and there is a problem that the control becomes complicated accordingly.

  The present invention has been made in view of the above, and the exposure timing can be obtained quickly and reliably without any restrictions on the arrangement of the light source and without performing complicated control such as light amount control on the light source. It is an object of the present invention to provide a laser beam scanning adjustment method for a color printing apparatus.

  According to the first aspect of the present invention, laser beams of three colors emitted from individual light sources and modulated by image signals of the respective colors have a predetermined time difference in a predetermined order through a scanning system. Each of the lasers that are at a predetermined level by a single optical sensor disposed on the downstream side of the scanning system and outside the exposure area is printed on the photosensitive material surface by periodically scanning the photosensitive material surface. In a laser beam scanning adjustment method of a color printing apparatus that receives light and starts an exposure operation with each laser beam using each light reception timing, the image is printed at the predetermined level before the image is printed on the photosensitive material. All of the laser light is once guided to a scanning system, and the single light sensor first detects the laser light from any of the light sources, and then the next scanning, and a predetermined time has elapsed since the first detection. Later, the light reception It is characterized in that the laser light scanned from the top to obtain a timing was guided to the scanning system. However, the predetermined time from the first detection is T2 <t3 <(T0−T2), where T0 is a scanning cycle and T2 is a scanning time difference between the laser beam scanned at the head and the third laser beam. It is t3 which satisfy | fills.

  According to the above configuration, the three color light sources are arranged according to given design conditions. Further, when the emission direction of the laser light from each light source is determined, each light source is turned on periodically in a predetermined order and with a predetermined time difference from the relationship with a preset scanning speed. To be controlled.

  In the present invention, two modes can be considered as on / off control of laser light received by a single photosensor. That is, a mode in which the light source is directly turned on (on) and extinguished (off), and a mode in which the light source is turned on and off by a modulation operation in the light modulation unit.

  In the former mode, during normal operation (image exposure operation), the three colors of laser light emitted from the individual light sources have a predetermined time difference in a predetermined order from the head light source at a predetermined cycle. And is modulated by an image signal and scanned on the photosensitive material through a scanning system. Accordingly, the photosensitive material surface is scanned and exposed with the laser beams of three colors and modulated, and an image is printed on the photosensitive material surface. Further, during the exposure operation, each laser beam is received immediately before exposure by a single optical sensor arranged outside the exposure area, and by using each light reception timing, the exposure operation ( That is, the modulation operation by the image signal of each color with respect to the laser beam is started.

  In such a configuration, when there is a print instruction or the like, all of the light sources are once turned on (on) before the image is printed on the photosensitive material. The output of the laser beam by lighting is a predetermined level, which may all be the same level or may be a level set individually. At the time of lighting, since the scanning position is unknown, it is unknown which laser light is first detected by a single optical sensor. In other words, the optical sensor is in a state where it cannot be specified what color laser beam is received. The optical sensor first detects a laser beam from any of the light sources immediately after this full lighting. With this detection, in the next scan, after a predetermined time has elapsed since the first detection, the light source of the laser beam scanned at the head to obtain the light reception timing is turned on. At this time, when the predetermined time from the first detection is T0 and the scanning time difference between the laser beam scanned at the head and the third laser beam is T2, T2 <t3 <(T0−T2 Therefore, in the next scanning, the laser beam from the head light source is surely detected, and the subsequent second and third laser beams are also detected. Therefore, after this, it is possible to start the image exposure operation on the photosensitive material by using the light reception timing of the optical sensor.

  That is, if scanning of laser light is performed in the order of G (green), B (blue), and R (red), the first color G laser light is emitted in the first scanning. If detected by the sensor, the time t3 until the next lighting exceeds at least the time T2, and therefore the G color in the next period is turned on beyond the detection timing of the last R color laser light in the same period. Thus, the G laser beam is reliably detected in the next cycle. On the contrary, in the first scan, if the R color laser beam, which is the last color, is detected by the optical sensor, the time t3 until the next lighting is at least earlier than (T0-T2), so that G in the next cycle. The G color is turned on without missing the color detection timing (at a time earlier than the G color detection timing), and the G laser light is reliably detected in the next cycle.

  In the latter mode, a light modulation unit for each color that modulates output laser light with an image signal is disposed on the optical path between each light source and the scanning system. Then, instead of turning on and off the light source, after the light source is turned on, the modulated output signal to the light modulation unit in a state in which the light source is maintained is substantially a signal with a modulation output at a predetermined high level, In other words, a low level signal with no modulation output may be used.

  According to a second aspect of the present invention, in the laser beam scanning adjustment method of the color printing apparatus according to the first aspect, the scanning system is a polygon mirror. According to the configuration of the second aspect, it is possible to guide the laser beams of the respective colors to the optical sensor and the photosensitive material surface with the same conditions at regular intervals with a simple configuration.

  According to a third aspect of the present invention, in the laser beam scanning adjustment method of the color printing apparatus according to the first or second aspect, after the single photosensor first detects a laser beam from one of the light sources. The next scanning is a first exposure operation to the photosensitive material. According to this configuration, since the exposure operation is started from the second period of scanning, the time from the print instruction to the start of exposure is shortened.

  According to the first aspect of the present invention, the laser beam from the head light source can be reliably detected in the next scanning of the on operation for obtaining the light receiving timing, and therefore the exposure operation to the photosensitive material is started from this scanning timing. can do.

  According to the second aspect of the present invention, the laser light of each color can be guided to the optical sensor and the photosensitive material surface under the same conditions every fixed period with a simple configuration.

  According to the third aspect of the present invention, since the exposure operation can be started from the next scanning in the second cycle, it is possible to speed up from the print instruction to the start of exposure.

  FIG. 1 is an external perspective view showing an embodiment of a color printing apparatus according to the present invention. The color printing apparatus 1 uses image data read from a film (negative, positive) by a line CCD scanner, image data taken by a digital camera, image data created by a personal computer, etc. on a photosensitive material (printing paper). A laser beam scanning device 100 to be exposed, a photosensitive material storage unit 200 that houses a magazine 201 for storing a photographic paper, which is a photosensitive material wound in a roll shape, and a print exposed by the laser beam scanning device 100. The image forming apparatus includes a developing unit 300 for developing, bleach-fixing and stabilizing paper, a drying unit 400 for drying the developed photographic paper, an unloading unit 500, and the like. Further, an unillustrated transport mechanism for transporting photographic paper from the photosensitive material container 200 to the carry-out section 500 is provided.

  As will be described later with reference to FIG. 2, the laser beam scanning device 100 includes a housing 102, in which a laser beam generation unit 104 and a laser intensity that modulates the intensity of the laser generated by the laser beam generation unit 104. The modulation member 108, the support 115 that supports these components, and the components and the support 115 are stored in a light-shielded state.

  The developing unit 300 develops, bleach-fixes and stabilizes the photographic paper after exposure, and the drying unit 400 dries the photographic paper after development using hot air or the like. A carry-out unit 500 is disposed on the upper surface of the apparatus. The carry-out unit 500 is formed at the top of the drying unit 400, and discharges the photographic paper one by one toward the upper surface of the apparatus. The photographic paper from the discharge port 501 is stacked and discharged in units of one order. In addition, the first conveying belt 502 that moves around each time the next order is generated and transfers the loaded object to the downstream side is provided on the downstream side of the first conveying belt 502, and the stacked state on the second conveying belt And a second conveyor belt 503 that is forwardly transferred by a predetermined pitch in a direction orthogonal to the circumferential direction of the first conveyor belt 502 to enable order sorting.

  With the above configuration, when an instruction for a printing operation is generated, the photographic paper fed out from the magazine 201 is cut into a predetermined size by a cutter (not shown), and then passes through a transport mechanism (not shown) to be a laser beam scanning apparatus that is an exposure unit. The image is exposed at 100, developed by the developing unit 300, and then output to the carry-out unit 500 via the drying unit 400.

  FIG. 2 is a perspective view for explaining the structure of the laser beam scanning apparatus 100. In FIG. 2, the upper portion of the housing 102 is omitted, but the housing 102 is configured in a sealed and dark room in order to prevent dust and the like from being mixed and to ensure a light shielding state. The laser beam scanning apparatus 100 includes light sources 104R, 104B, and 104G that emit three laser beams at appropriate positions on the housing 102.

  The laser light source 104R is configured by a semiconductor laser 104XR that emits red laser light. The laser light source 104B includes a semiconductor laser 104XB that emits laser light having a predetermined wavelength, and a wavelength conversion element 104YB that obtains blue laser light that is the second harmonic. The laser light source 104G includes a semiconductor laser 104XG that emits laser light having a predetermined wavelength, and a wavelength conversion element 104YG that obtains green laser light that is the second harmonic.

  On the laser emission side of the laser light sources 104R, 104B, and 104G, a collimator lens 106, an acousto-optic modulator (Acousto-Optic Modulator: hereinafter referred to as AOM) 108 that functions as a laser intensity modulation member, a laser shaping aperture 107, and a mirror 110 are provided. On the laser reflection side of the mirror 110, a spherical lens 112, a cylindrical lens 114, and a polygon mirror 118 that rotates at a constant speed and performs main scanning of the laser light are sequentially arranged.

  On the laser emission side of the polygon mirror 118, an fθ lens 120, a cylindrical lens 122, a mirror 124, and a mirror 126 are arranged in this order. Then, the G, B, and R laser beams reflected by the mirror 126 are irradiated in this order on the two surfaces of the photographic paper conveyed from the direction of the arrow C (sub-scanning direction) to expose the image.

  The optical sensor 130 adjusts the start timing of the exposure operation by main scanning, and is on the reflection side of the mirror 124 and at the end of the main scanning start side by the polygon mirror 118 (outside the exposure area and on the main scanning start side). At the position where the laser beam is incident. The arrangement position of the optical sensor 130 corresponds to the optical path length from the polygon mirror 118 to the two surfaces of the photographic paper, and is preferably set to a substantially equal optical path length. Note that, in the aspect in which the optical path length to the two surfaces of the photographic paper and the optical path length to the optical sensor 130 are set to be different due to reasons such as the arrangement space of the optical sensor 130, the optical path difference depends on the optical path difference ratio. The time information related to various time widths to be set may be converted and used.

  The AOM 108 is an example of a light intensity modulation element, and three AOMs 108 are arranged at required positions of the housing 102 so that laser light incident from the laser light sources 104G, 104B, and 104R passes through the internal acoustooptic medium. In addition, each AOM 108 is connected to an AOM driver 111 (not shown).

  When a signal corresponding to the image density of each corresponding G, B, and R color is input from the AOM driver 111 to each AOM 108, an ultrasonic optical effect corresponding to the output of the AOM driver 111 acts on the acoustic optical medium of the AOM 108. As a result, the laser beam incident on the AOM 108 is modulated to an intensity corresponding to the image density, and is emitted from the AOM 108 as diffracted light (modulated light).

  Next, the operation of the laser beam scanning apparatus having the above configuration will be described. Laser light emitted from the laser light source 104 enters the AOM 108 through the collimator lens 106. The laser light incident on the AOM 108 is modulated by a signal corresponding to each of the G, B, and R image densities input from the AOM driver 111 and is emitted as diffracted light (modulated light). The modulated laser light emitted from the AOM 108 is reflected by the polygon mirror 118 that rotates at a constant speed in the direction of the arrow, thereby scanning in the main scanning direction, and the fθ lens 120, the cylindrical lens 122, and the mirror 124. The photographic paper 2 is irradiated through the mirror 126. On the other hand, the photographic paper 2 is conveyed at a constant speed by a conveyance mechanism (not shown) in the direction of an arrow C that is substantially orthogonal to the main scanning direction. As a result, a two-dimensional image is formed (printed) on the photographic paper 2. The

  FIG. 3 is a configuration diagram of the control unit 150 that controls the AOM driver 111. The control unit 150 is a FIFO (First-in / First-out) memory that sequentially stores color image data (image density data) for the three colors of GBR stored in the image memory 140 for each main scan. And the like, a D / A converter 170G, 170B, 170R for converting image data for one main scan into an analog signal for each color, and reading of image data from the image memory 140 to the buffer 160 (temporary) A clock pulse for reading out image data from the buffer 160 to the D / A converters 170G, 170B, and 170R, and D / A converters 170G, 170B, and 170R. A timing controller 180 for outputting a clock pulse for D / A conversion at And a clock generator 190 for generating a reference clock pulse as a reference for timing control. The cycle of the clock pulse from the timing controller 180 to the buffer 160 and the clock pulse to each D / A converter 170G, 170B, 170R define one dot of the image formed on the photographic paper.

  FIG. 4 is an example of a configuration diagram of the timing control unit. The timing control unit 180 adjusts and controls the rising of the detection operation of the laser beam by the optical sensor 130, and the color image corresponding to the D / A converters 170G, 170B, and 170R from the buffer 160 after the rising processing. It includes a synchronization control unit 182 for setting each timing for outputting a signal and a power source control unit 183 for controlling turning on and off of the laser light sources 104G, 104B, and 104R, and related to various timings necessary for the start-up process and the exposure operation. A timing information storage unit 184 that stores conditions to be stored.

  The various timing information includes the period T0 of the main scanning by the polygon mirror 118, the position of the optical sensor of the laser beam of the first color (G color here) and the second (B color here) laser beam (or the main on the photographic paper surface). The scanning time difference T1 on the scanning line (and the time associated with T1, which is shorter than T1 by a minute time (lighting time t1 of the laser light source 104B immediately before T1)), the third color G laser light (here In this case, the scanning time difference T2 at the optical sensor position (or on the main scanning line of the photographic paper 2) with the laser beam of R color (and the time related to T2, which is shorter than T2 by a minute time (immediately before T2). The laser light source 104R lighting time t2), a predetermined time t3 satisfying T2 <t3 <(T0-T2), and an exposure operation after the photosensor 130 detects G color, that is, the buffer 160 outputs a D / A converter. Time τG until output of the G-color image signal via the data 170G starts, exposure operation after the optical sensor 130 detects B-color, that is, the B-color image from the buffer 160 via the D / A converter 170B. The time τB until the start of signal output, the time from when the optical sensor 130 detects the R color until the exposure operation, that is, the output of the R color image signal from the buffer 160 via the D / A converter 170R. At least τR is included. Note that these times can be set by checking the time conditions in advance for each device, and can be updated by the secular change of individual beam emission directions such as the laser light source 104.

  The rise control unit 181 includes a timer or the like, and immediately after the power is turned on or before the exposure operation for the photographic paper 2 is started, the optical sensor 130 individually outputs the laser beams of the respective colors from the laser light sources 104G, 104B, and 104R. The adjustment is set so as to be detected at a later time, and the method will be described later. The synchronization control unit 182 includes three timers and the like corresponding to each color, and detects a laser beam of each color from the optical sensor 130 during the exposure operation on the photographic paper 2 (the τG, τB, τR). ) A synchronization process for outputting image data of each color of the D / A converters 170G, 170B, and 170R from the buffer 160 later is performed. The power supply control unit 183 performs lighting control for the laser power supplies 104G, 104B, and 104R during the control in the rise control unit 181 and the synchronization control unit 182.

  Here, timing control during exposure will be described with reference to a time chart shown in FIG. In FIG. 5, signals SG, SB, and SR indicate signals for turning on and off the laser light sources 104G, 104B, and 104R output from the power supply control unit 183. A signal S indicates a detection signal from the optical sensor 130. Signals CKG, CKB, and CKR are clock pulses that output image signals of respective colors.

  During the exposure operation, the power supply control unit 183 turns on the laser light source 104G for a predetermined time before the optical sensor 130 detects the G laser light in the scanning period T0, and the optical sensor 130 detects the G laser light. Then, the laser light source 104G is temporarily turned off and turned on again within a predetermined time until the time τG elapses. Thereafter, when the time τG elapses, the synchronization controller 182 causes the G color image data to be turned on. The exposure operation is started by the clock pulse CKG that outputs, whereby printing for one main scan is started from the predetermined position of the photographic paper 2 with the G color image signal.

  Further, the power source control unit 183 turns on the laser light source 104B when the time t1 has elapsed after the optical sensor 130 detects the G-color laser light. The B-color optical laser is detected by the optical sensor 130 when a time T1 elapses after detection of the G-color laser light. By this detection, the power supply control unit 183 turns off the laser light source 104B and turns it on again within a predetermined time until the time τB elapses. Thereafter, when the time τB elapses, the synchronization control unit 182 An exposure operation is started by a clock pulse CKB that outputs B-color image data, whereby printing for one main scan with a B-color image signal is started from a predetermined position on the photographic paper 2.

  Further, the power supply control unit 183 turns on the laser light source 104R when t2 time has elapsed after the optical sensor 130 detects the G-color laser light. This R-color optical laser is detected by the optical sensor 130 when the time T2 has elapsed after detection of the G-color laser light. By this detection, the power supply control unit 183 turns off the laser light source 104R and relights it within a predetermined time until the time τR elapses. Thereafter, when the time τR elapses, the synchronization control unit 182 The exposure operation is started by the clock pulse CKR that outputs the R color image data, whereby the printing for one main scanning with the R color image signal is started from a predetermined position of the photographic paper 2. As a result, the image signal of each color of GBR is printed in the main scanning direction from the same position of the photographic paper. The power supply control unit 183 temporarily turns off each of the laser light sources 104G, 104B, and 104R every time a predetermined exposure time of an image for one main scan ends.

  Then, the exposure operation for one main scanning of each color is completed, and the time t0 (timing at which the G color can be detected in the next cycle after the time T0, that is, a time slightly shorter than T0, from the detection time of the immediately preceding G laser beam ), Each time the laser light sources 104G, 104B, and 104R are turned on and off for the next period (next main scan), the process is repeated as described above. As a result, a two-dimensional image is printed on the two photographic papers.

  Next, FIGS. 6 and 7 are time charts for explaining the rise control, FIG. 6 is an explanatory diagram for defining the lower limit time (condition), and FIG. 7 is an explanatory diagram for defining the upper limit time (condition). It is. In the figure, PG indicates a scanning position where the optical laser 113 detects the G laser beam during scanning, and PB indicates a scanning position where the optical laser 113 detects the B laser beam during scanning. , PR indicates the scanning position where the optical sensor 113 detects the R laser beam during scanning.

  In FIG. 6, the laser light sources 104G, 104B, and 104R are simultaneously turned on by the power supply control unit 183, and the scanning position of the G laser light at the time of the lighting is the G laser light by the optical sensor 113. It is assumed that it is in front of the detected scanning position PG. Therefore, in the illustrated example, the G color laser light is first detected by the optical sensor 130. As described above, it is impossible to identify which color of the laser light is detected by the optical sensor 130, but the power supply control unit 183 indicates that the G-color laser light is detected by the optical sensor 113 (detection signal S1). In view of this, the B and R laser beams are turned off, and after t1 hours and t2 hours (same as t1 and t2 in FIG. 5), the B and R laser beams are sequentially turned on. The optical sensor 113 sequentially detects the B color laser light when the B color laser light reaches the scanning position PB, and the R color laser light when the R color laser light reaches the scanning position PR (detection). Signals S2, S3).

  Considering the G-color laser light, assuming that an elapse time of time T2 or less from the detection is set as the lighting signal SG ′ as the timing for turning on the laser light source 104G in the next cycle, this time T2 Is also the timing for detecting the R color laser light in the current cycle, so if the G color laser light is turned on during this period, the current R color laser light and the G color laser light as the next cycle The rise control unit 181 erroneously determines the detection signal S3 on the basis of the cycle, that is, the cycle T0 ′ shown in the drawing. For this reason, at the timing when the G laser beam is turned on at the next period T0 ′, the scanning position of the G laser beam has already passed the detection position PG, and the first G color will pass through forever. The laser beam cannot be detected. Therefore, when the G laser beam is detected at the beginning of the rising process, in the next period, the G laser beam needs to be at a point in time exceeding the time T2.

  If the first detected laser beam is B or R, the optical sensor 113 can detect the G color even if the G laser beam of the next period is turned on if there is time T2. Since laser light can be reliably detected, from the viewpoint of defining the lower limit condition (in order to reliably detect laser light of the leading color in the next period for any laser light of GBR) There is no need to consider B and R colors. Then, when the power source control unit 183 turns on the laser light of the first color (G color) in the next cycle, if the light lasers of other colors are turned on, that is, in the start-up process, the B and R lasers In a mode in which light is first detected, a process of turning off these is performed.

  From the above, in order for the optical sensor 113 to reliably detect the laser light of the first color (G color in this case) of the next period, the laser light source 104G is turned on in the time exceeding the time T2 from the first detection in the rising control. It is a necessary condition to light up. At this time, if the time from when the laser beam is first detected in the current period until the G laser beam is turned on in the next period is t3, T2 <t3.

  On the other hand, in FIG. 7, the laser light sources 104G, 104B, and 104R are turned on simultaneously by the power supply control unit 183, and the G laser beam scanning position PGS at the time of turning on is a B color laser beam. It is assumed that the scanning position PB detected at 113 and the R color laser beam are between the scanning position PR detected by the optical sensor 113. Therefore, in the illustrated example, actually, the R color laser light is first detected by the optical sensor 130. Since the optical sensor 130 cannot identify which color of the laser beam is detected as described above, the power supply control unit 183 regards that the G color laser beam is detected by the optical sensor 113 (detection signal S4). The B-color and R-color laser beams are turned off, and the B-color and R-color laser beams are sequentially turned on after t1 hours and t2 hours. At this time, the B-color laser light has passed the scanning position PB, and the R-color laser light has passed the scanning position PR, so that both remain lit.

  Therefore, the power supply control unit 183 determines the next cycle as T0 ″ as the lighting timing of the G-color laser beam, and has a relationship delayed from the original cycle T0. For this reason, when the G laser beam is turned on after the time T0 ″, the G laser beam has passed the scanning position PG detected by the optical sensor 113. The color laser beam cannot be detected.

  Therefore, if a time shorter than the time (T0-T2) from the detection is set as the timing for turning on the laser light source 104G in the next cycle, the G mirror in the next cycle is set by the polygon mirror 118 at this time (T0-T2). Therefore, it is possible to detect the laser beam of G color in the next period.

  Note that when the G color laser light is turned on in the next cycle, the power supply control unit 183 performs a process of turning off the other color laser light if turned on.

  Therefore, in order for the optical sensor 113 to reliably detect the G-color laser beam in the next period, it is necessary to turn on the laser light source 104G in a time less than the time (T0-T2) from the first detection in the rising control. It is a condition. If the time from when the laser beam is first detected in the current cycle to when the G laser beam is turned on in the next cycle is t3, then t3 <(T0−T2). As a result, the time t3 for turning on the laser light source 104G to be scanned at the head necessary for reliably detecting the G-color laser light in the next period from the time when the laser light is first detected in the current period is T2 < It is expressed as t3 <(T0−T2). When the start-up process is completed, in the subsequent exposure operation, the optical sensor 113 sequentially detects the laser beams of the respective colors and uses these light reception timings to start the exposure operation of the corresponding images of the respective colors on the photographic paper. That is, a normal exposure operation (for each main scanning) is started.

In the above, for example, the polygon mirror 118 has six reflecting mirrors, the scanning time for one surface at this time is 725 μs (microseconds), T1 is 725/24 μs, T2 is 725/12 μs, and t3 is 550 μs. Then, the above condition is
725/12 μs <550 μs <(725 μs−725 / 24 μs)
As shown, I am satisfied.

  By controlling the rise detection of the laser beam from the laser light source 104, the exposure operation can be performed from the next period. Further, in the aspect in which the rise detection control is performed at the time of turning on the power, it is possible to shift from the scanning immediately after the subsequent print instruction to the exposure operation.

  The present invention can employ the following modified modes.

  (1) In this embodiment, the scanning order of the laser light is set to G, B, and R. However, the scanning order is not limited to this, and it is possible to design in a predetermined color order. The information stored in the timing information storage unit 184 includes the above-described t1 and t2 in addition to T1 and T2.

  (2) Instead of turning on (ON) and turning off (OFF) the light sources 104R, 104B, and 104G, the light sources 104R, 104B, and 104G are turned on and modulated as modulated signals to the AOM 108 (light modulation unit). A signal whose output is a predetermined high level and a signal whose level is substantially free of modulation output may be used. These modulated signals are stored in the memory 141 as signals for rise control and synchronization control separately from the image memory 104, for example, and the timing control unit 180 turns on and off at the AOM 108 for each laser beam. According to the control, it may be configured to output to D / A converters 170G, 170B, 170R (or AOM driver 111 may be used). In this case, the power supply control unit 183 simply performs the first light source ON operation, and the subsequent control is performed by the rise control unit 181 and the synchronization control unit 182. According to this, since it is not necessary to repeatedly turn on and off the light sources 104R, 104B, and 104G, the light amount stability is excellent and the life of the light source can be extended.

  (3) In the present embodiment, the light sources 104R, 104B, and 104G are turned on and off while adopting the AOM 108. Instead, the configuration for light modulation in the AOM 108 and the AOM 108 is not adopted. Alternatively, the light sources 104R, 104B, and 104G may be modulated and driven directly with image signals. According to this, the configuration is simplified.

1 is an external perspective view showing an embodiment of a color printing apparatus to which the present invention is applied. It is a perspective view explaining the structure of a laser beam scanning apparatus. It is a block diagram of the timing control part which controls an AOM driver. It is a block diagram of a timing control part. It is a time chart for demonstrating the timing control during exposure. It is a time chart explaining control at the time of start-up, and is an explanatory diagram for defining a lower limit time (condition). It is a time chart explaining control at the time of start-up, and is an explanatory diagram for defining an upper limit time (condition).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color printing apparatus 100 Laser beam scanning apparatus 104 Laser light source 118 Polygon mirror 130 Optical sensor 150 Control part 160 Buffer 170 D / A converter 180 Timing control part 181 Rise control part 182 Synchronization control part 183 Power supply control part 184 Timing information storage part 190 Clock generator

Claims (3)

Laser beams of three colors emitted from individual light sources and modulated by image signals of the respective colors are periodically applied to the photosensitive material surface with a predetermined time difference through a scanning system. A color image is printed on the surface of the photosensitive material by scanning, and each laser beam at a predetermined level is received by a single optical sensor arranged on the downstream side of the scanning system and outside the exposure area. In the laser beam scanning adjustment method of the color printing apparatus that starts the exposure operation by each laser beam using the timing,
Prior to the image printing operation on the photosensitive material, the laser light is once all guided to the scanning system at the predetermined level, and after the single light sensor first detects the laser light from any of the light sources, A laser for a color printing apparatus, characterized in that the laser beam scanned at the head is guided to a scanning system to obtain the light reception timing after a predetermined time has elapsed since the first detection. Optical scanning adjustment method.
However, the predetermined time from the first detection is T2 <t3 <(T0−T2), where T0 is a scanning cycle and T2 is a scanning time difference between the laser beam scanned at the head and the third laser beam. It is t3 which satisfy | fills. 2. The laser beam scanning adjustment method for a color printing apparatus according to claim 1, wherein the scanning system is a polygon mirror. 3. The next scanning operation after the single optical sensor first detects a laser beam from any one of the light sources is a first exposure operation on the photosensitive material. Laser beam scanning adjustment method for color printing apparatus.

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