JP3715572B2 - Image exposure device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image exposure apparatus, and more particularly to an image exposure apparatus that includes a GaN-based semiconductor laser and that scans and exposes a recording material such as a photosensitive material with a light beam modulated according to an image.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, a light source device using a semiconductor laser or an edge-emitting LED (such as a superluminescent light emitting diode (SLD)) made of GaAs substrate-like AlGaInP, AlGaAs, or InGaAsP is used to optically scan the recording material to form an image. An image exposure apparatus has been proposed.
[0003]
In the light source device using the material as described above, GaAs serving as a substrate with respect to the emission wavelength is an absorbing material, and a light absorbing material such as InGaAs is also used for the counter electrode. For this reason, light is normally confined in a light emitting region having a width of several microns, and stray light outside the stripe region is relatively small due to the effect of the absorbing material described above.
[0004]
On the other hand, a semiconductor laser or an edge emitting LED using a GaN (gallium nitride) material system that is approaching practical use recently uses a transparent substrate such as sapphire or SiC for the emission wavelength. For this reason, the stray light that reaches the end of the chip is returned to the vicinity of the active region by reflection, or is transmitted through the substrate by a plurality of reflections, so that various patterns of stray light are generated.
[0005]
FIG. 9 shows a schematic diagram when such a GaN-based semiconductor laser is used as a light source of a silver salt exposure apparatus that performs spot scanning on a silver salt photosensitive material using a polygon mirror or the like. As shown in FIG. 9, the laser light emitted from the GaN-based semiconductor laser 190 is condensed into a spot 194 having a predetermined size by a condenser lens 192. However, the stray light 198 whose light emitting position and direction are random cannot be condensed on the spot 194 and forms a blurred pattern 200.
[0006]
FIG. 10 shows the relationship between the light output of the spot 194 and the drive current, and the relationship between the light output of the blurred pattern 200 and the drive current. As shown in FIG. 10, it can be seen that considerable power exists in the blurred pattern 200, particularly in the low exposure intensity of about 0.05 mW region which is important in the silver salt exposure method.
[0007]
Compared with the electrophotographic system using a photosensitive material such as a photosensitive drum, in the high-grade silver salt exposure system, which is very sensitive, the photosensitive material reacts with the blurred pattern 200, that is, stray light, It becomes a fatal defect. For example, when a pattern (for example, a striped pattern as shown in FIG. 11A) having the same line width as that of the spot 194 is formed by a GaN-based semiconductor laser, the pattern shown in FIG. As shown in the figure, an image is formed in a stripe shape. However, the above-described blurred image 200 is colored between the stripes, which is different from the expected image shown in FIG. The image will be remarkably deteriorated.
[0008]
The amount of light in the blurred pattern due to stray light is small, so this is not a problem for area gradation as in electrophotography, but it is weak in continuous tone photosensitive materials such as silver halide photography where the level of non-sensitivity is very low. The background causes blurring of characters and images, resulting in a significant deterioration in quality.
[0009]
As described above, particularly in the silver salt type exposure characterized by high-quality images, it is necessary to reduce stray light peculiar to a GaN-based semiconductor laser that adversely affects the image and has a serious and fatal effect.
[0010]
Further, in the conventional semiconductor lasers other than GaN, as shown in FIG. 12A, when the LED emission is relatively weak and intensity binary modulation such as pulse width modulation is performed, the laser drive current is a predetermined threshold value. A predetermined extinction ratio (a ratio between a photosensitive level at which the photosensitive material is exposed at a predetermined level and a non-photosensitive level at which the photosensitive material is not exposed) can be obtained by setting the OFF level in advance so as to be equal to or lower than Ith. It is possible to prevent exposure at the level.
[0011]
On the other hand, as shown in FIG. 12B, a GaN-based semiconductor laser cannot obtain a sufficient extinction ratio because there is a region where LED emission is relatively strong even below the conventional threshold value Ith. Further, the LED emission leaks from the waveguide, and the entire crystal end face emits light. This attenuates while passing through the optical system, but a non-negligible amount of light exists on the photosensitive material as the stray light described above around the predetermined spot of the light beam. This results in multiple exposures and may cause unexpected color development.
[0012]
Here, if the laser driving current at the non-photosensitive level is simply set to 0 mA, a sufficient extinction ratio can be obtained even with a GaN-based semiconductor laser, and excessive color development can be suppressed. And the non-photosensitive level may become too large, and high-speed modulation may not be possible, and the load on the modulation circuit may increase.
[0013]
In addition, since the photosensitive characteristics vary depending on the type of photosensitive material, if the photosensitive level and the non-photosensitive level are set based on a specific photosensitive material, an image may not be recorded properly.
[0014]
The present invention has been made in consideration of the above-described facts, and provides an image exposure apparatus capable of appropriately setting a photosensitive level and a non-photosensitive level according to the type of photosensitive material and suppressing deterioration in image quality due to stray light. For the purpose.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 includes a GaN-based semiconductor laser that emits a laser beam and a light beam including emission light other than the laser beam, and an optical that forms an image of the light beam on a photosensitive material. A system, a scanning exposure unit that scans and exposes the photosensitive material with a light beam modulated according to image data to be recorded, an input unit that inputs the type of the photosensitive material, and the type of the photosensitive material, A setting means for setting a photosensitive level at which the photosensitive material is sensitized and a non-photosensitive level at which the photographic material is not sensitized. Drive means for driving the GaN-based semiconductor laser so as to be below the photosensitive level.
[0016]
The light beam emitted from the GaN-based semiconductor laser includes laser light and emitted light other than the laser light. The emitted light is light that has been transmitted to the outside through the substrate of the GaN-based semiconductor laser, and this becomes stray light that degrades image quality.
[0017]
The light beam emitted from the GaN-based semiconductor laser is imaged on the photosensitive material by an optical system including a predetermined lens and the like.
[0018]
The scanning exposure means scans and exposes the photosensitive material with a light beam modulated according to the image data. This scanning exposure means includes a polygon mirror or the like.
[0019]
The setting unit sets a photosensitive level at which the photosensitive material is exposed and a non-photosensitive level at which the photosensitive material is not exposed in accordance with the type of the photosensitive material input by the input unit. As the type of the photosensitive material, one previously stored in the memory may be input, or may be input by an operator's operation.
[0020]
As described above, since not only the photosensitive level but also the non-photosensitive level is appropriately set according to the type of the photosensitive material, it is possible to prevent the image quality from changing depending on the type of the photosensitive material.
[0021]
The driving means drives the GaN-based semiconductor laser so that the light amount of the light beam applied to the photosensitive material is equal to or higher than the photosensitive level or equal to or lower than the non-photosensitive level according to image data. At this time, for example, the driving is preferably performed so that the ratio between the photosensitive level and the non-photosensitive level is constant, and the driving is preferably performed so that the difference between the photosensitive level and the non-photosensitive level is small. Thereby, switching between the photosensitive level and the non-photosensitive level can be performed at high speed, and the load on the driving means can be reduced.
[0022]
As set forth in claim 2, the setting means includes a predetermined first reference photosensitive level for exposing at a predetermined level, and a predetermined second reference photosensitive level for preventing the photosensitive material from being exposed. The ratio is determined based on the ratio storage means stored according to the type of the photosensitive material and the color measurement result of the test pattern recorded on the photosensitive material so as to be exposed at the predetermined level. A photosensitive level input means for inputting a photosensitive level, and sets the measured photosensitive level as the photosensitive level, and calculates and sets the non-photosensitive level from the ratio corresponding to the type of the photosensitive material and the photosensitive level. can do.
[0023]
The ratio storage means has a ratio of a predetermined first reference photosensitive level for exposing at a predetermined level and a predetermined second reference photosensitive level for not exposing the photosensitive material, that is, an extinction ratio. Stored for each type of material.
[0024]
The setting means sets the measured photosensitive level input by the input means as the photosensitive level.
[0025]
The measured photosensitive level is determined so as to be exposed at a predetermined level based on the color measurement result of the test pattern recorded on the photosensitive material. For example, the test pattern is colorimetrically measured by the colorimetric means, and the photosensitive level at which the density becomes a predetermined level is determined as the measured photosensitive level. Note that the measured photosensitive level may be set by visual observation without using the colorimetric means.
[0026]
Then, the setting means reads the ratio corresponding to the type of photosensitive material from the ratio storage means, and calculates and sets the non-photosensitive level from the read ratio and the set photosensitive level, that is, the measured photosensitive level.
[0027]
In this way, by setting the photosensitive level to the measured photosensitive level, it is possible to set the optimum photosensitive level and non-photosensitive level regardless of variations in photosensitive material and aging degradation of the apparatus.
[0028]
According to a third aspect of the present invention, the optical system further comprises a monitor optical system for monitoring the light beam, and a light receiving means for receiving the light beam transmitted through the monitor optical system, the monitor optical system comprising: The component ratio between the laser light and the emitted light of the light beam received by the light receiving means is configured to be substantially the same as the component ratio on the photosensitive material, and the driving means is the light receiving means. The GaN-based semiconductor laser may be driven so that the amount of the received light beam becomes the photosensitive level or the non-photosensitive level.
[0029]
The monitor optical system branches the light beam emitted from the GaN semiconductor laser toward the light receiving means. The monitor optical system is configured such that the component ratio between the laser beam and the emitted light of the light beam received by the light receiving means is substantially the same as the component ratio on the photosensitive material. The light quantity of the beam can be received.
[0030]
The driving unit drives the GaN-based semiconductor laser so that the light amount of the light beam received by the light receiving unit becomes a photosensitive level or a non-photosensitive level.
[0031]
As described above, the light receiving means can detect a light beam substantially equivalent to the light beam on the photosensitive material, so that the GaN-based semiconductor laser can be driven more accurately and the deterioration of the image quality can be prevented. .
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to a digital laboratory system.
[0033]
(Overview of the entire system)
FIG. 1 shows a schematic configuration of a digital lab system 10 according to an embodiment of the present invention, and FIG. 2 shows an external appearance of the digital lab system 10. As shown in FIG. 1, the laboratory system 10 includes a line CCD scanner 14, an image processing unit 16, a laser printer unit 18 as an image exposure device, and a processor unit 20. The image processing unit 16 is integrated as an input unit 26 shown in FIG. 2, and the laser printer unit 18 and the processor unit 20 are integrated as an output unit 28 shown in FIG.
[0034]
The line CCD scanner 14 is a film image recorded on a photographic light-sensitive material (hereinafter simply referred to as “photographic film”) such as a photographic film (for example, a negative film or a reversal film). A negative image or a positive image visualized in the above, for example, a 135 size photographic film, a 110 size photographic film, and a photographic film formed with a transparent magnetic layer (240 size photographic film: so-called APS film), 120 size and 220 size (Broni size) photographic film film images can be read. The line CCD scanner 14 reads the film image to be read with a three-line color CCD, and outputs R, G, and B image data.
[0035]
As shown in FIG. 2, the line CCD scanner 14 is attached to the work table 30. The image processing unit 16 is stored in a storage unit 32 formed below the work table 30, and an opening / closing door 34 is attached to an opening of the storage unit 32. The storage unit 32 is normally in a state of being concealed by the opening / closing door 34, and when the opening / closing door 34 is rotated, the inside is exposed and the image processing unit 16 can be taken out.
[0036]
The work table 30 has a display 164 attached to the back side and two types of keyboards 166A and 166B. One keyboard 166 </ b> A is embedded in the work table 30. The other keyboard 166B is housed in the drawer 36 of the work table 30 when not in use, and is removed from the drawer 36 and placed on the keyboard 166A when in use. When the keyboard 166B is used, a connector (not shown) attached to the end of a cord (signal line) extending from the keyboard 166B is connected to a jack 37 provided on the work table 30, whereby the keyboard 166B connects the jack 37. Via the image processing unit 16.
[0037]
A mouse 40 is disposed on the work surface 30U of the work table 30. In the mouse 40, a code (signal line) is extended into the storage unit 32 through a hole 42 provided in the work table 30, and is connected to the image processing unit 16. The mouse 40 is housed in the mouse holder 40A when not in use, and is removed from the mouse holder 40A and placed on the work surface 30U when in use.
[0038]
The image processing unit 16 receives image data (scanned image data) output from the line CCD scanner 14, image data obtained by photographing with a digital camera, and a document other than a film image (for example, a reflective document). The image data obtained by reading the image with a scanner, the image data generated by a computer, etc. (hereinafter collectively referred to as file image data) are input from the outside (for example, via a storage medium such as a memory card). Or can be input from another information processing device via a communication line).
[0039]
The image processing unit 16 performs various image processing such as various corrections on the input image data, and inputs the image data to the laser printer unit 18 as recording image data. Further, the image processing unit 16 outputs the image data subjected to the image processing to the outside as an image file (for example, outputs it to an information storage medium such as a memory card, or transmits it to another information processing device via a communication line). Etc.) is also possible.
[0040]
The laser printer unit 18 includes R, G, and B laser light sources, irradiates the photographic paper with laser light modulated according to the recording image data input from the image processing unit 16, and performs photographic paper by scanning exposure. An image (latent image) is recorded on. The processor unit 20 performs color development, bleach-fixing, water washing, and drying on the photographic paper on which an image is recorded by scanning exposure in the laser printer unit 18. As a result, an image is formed on the photographic paper.
[0041]
(Detailed configuration of the laser printer)
Next, the configuration of the laser printer unit 18 will be described in detail. FIG. 3 shows the configuration of the optical system of the laser printer unit 18.
[0042]
The laser printer unit 18 includes three laser light sources, laser light sources 211R, 210G, and 211B. The laser light source 211R is configured by a semiconductor laser (LD) that emits laser light (hereinafter referred to as R laser light) having an R wavelength (for example, 685 nm). The laser light source 210G includes an LD 210L as laser light emitting means and a wavelength conversion element (SHG) 210S as wavelength converting means for converting the laser light emitted from the LD 210L into laser light having a half wavelength. Therefore, the oscillation wavelength of the LD 210L is determined so that laser light having a G wavelength (for example, 532 nm) (hereinafter referred to as G laser light) is emitted from the SHG 210S. The laser light source 211B is configured by an LD that emits laser light having a wavelength of B (for example, 440 nm) (hereinafter referred to as B laser light).
[0043]
A collimator lens 212 and an acoustooptic device (AOM) 214G as an external modulation unit are sequentially arranged on the laser light emission side of the laser light source 210G. The AOM 214G is arranged so that the incident laser light passes through the acoustooptic medium, and is connected to an AOM driver (not shown). When a high frequency signal is input from the AOM driver, the AOM 214G The ultrasonic wave according to the high frequency signal propagates, the acoustooptic effect acts on the laser light transmitted through the acoustooptic medium, and diffraction occurs, and the laser light having the intensity according to the amplitude of the high frequency signal is emitted from the AOM 214G as diffracted light. Is done.
[0044]
A plane mirror 215 is arranged on the diffracted light emission side of the AOM 214G, and a spherical lens 216, a cylindrical lens 217, and a polygon mirror 218 are arranged in order on the laser light emission side of the plane mirror 215, from the AOM 214G. The G laser light emitted as the diffracted light is reflected by the plane mirror 215, reflected by the spherical mirror 216 and the cylindrical lens 217 to a predetermined position on the reflecting surface of the polygon mirror 218, and reflected by the polygon mirror 218. The
[0045]
On the other hand, a collimator lens 213 and a cylindrical lens 217 are sequentially arranged on the laser light emission side of the laser light sources 211R and 210B, and the laser light emitted from the laser light sources 211R and 211B is converted into parallel light by the collimator lens 213. The light is irradiated through the cylindrical lens 217 to a position substantially the same as the predetermined position on the reflection surface of the polygon mirror 218 and reflected by the polygon mirror 218.
[0046]
The three R, G, and B laser beams reflected by the polygon mirror 218 are sequentially transmitted through the fθ lens 220 and the cylindrical lens 221, reflected by the cylindrical mirror 222, and then reflected substantially vertically downward by the folding mirror 223. Then, the photographic paper 224 is irradiated through the opening 226. Alternatively, the folding mirror 223 may be omitted, and the photographic paper 224 may be irradiated by being directly reflected substantially vertically downward by the cylindrical mirror 222.
[0047]
On the other hand, a scanning start detection sensor (hereinafter referred to as an SOS detection sensor) 228 for detecting the R laser beam that has reached through the aperture 226 is disposed near the side of the scanning exposure start position on the photographic paper 224. Yes. The reason why the laser beam detected by the SOS detection sensor 228 is the R laser beam is that the photographic paper has the lowest R sensitivity, and therefore the light quantity of the R laser beam is maximized, so that it can be reliably detected. This is because the R laser beam reaches the SOS detection sensor 228 earliest in scanning by the rotation of the mirror 218. In the present embodiment, a signal output from the SOS detection sensor 228 (hereinafter referred to as a sensor output signal) is normally at a low level, and is set to a high level only when an R laser beam is detected. It is configured.
[0048]
Although not shown in FIG. 3, the laser printer unit 18 monitors the pinhole 102 and the B laser light for removing stray light (emitted light), which is an LED emission component, at a position where the B laser light converges. A monitor optical system 104 (details will be described later).
[0049]
Next, a detailed configuration of the laser light source 211B according to the present embodiment will be described. FIG. 4 shows a schematic sectional view of a laser light source 211B according to the embodiment of the present invention. In FIG. 4, W1 = 1.7 μm, W2 = 300 μm, H1 = about 0.9 μm, H2 = about 3.5 μm, and H3 = 100 μm.
[0050]
The laser light source 211B is made of an InGaN semiconductor laser and has a sapphire c-plane substrate (S. Nagahama et.al., jpn.Appl.Phys.Vol.39, No.7A, p. A low-defect GaN substrate layer is formed (by the method described in L347 (2000)).
[0051]
Next, using an atmospheric pressure MOCVD method, an n-GaN buffer layer (Si-doped, 5 μm) 70, n-In _0.1 Ga _0.9 N buffer layer (Si-doped, 0.1 μm) 66, n-Al _0.1 Ga _0.9 N clad layer (Si doped, 0.45 μm) 64, n-GaN light guide layer (Si doped, 0.04 to 0.08 μm) 62, undoped active layer 60, p-GaN light guide layer (Mg doped,. 04-0.08 μm) 58, p-Al _0.1 Ga _0.9 An N clad layer (Mg doped, 0.45 μm) 56 and a p-GaN cap layer (Mg doped, 0.25 μm) 54 are grown.
[0052]
The active layer 60 is made of undoped In _0.05 Ga _0.95 N (10 nm), undoped In _0.23 Ga _0.77 N quantum well layer (3 nm), undoped In _0.05 Ga0.95N (5nm), undoped In _0.23 Ga _0.77 N quantum well layer (3 nm), undoped In _0.05 Ga _0.9 N (10 nm), undoped Al _0.1 Ga _0.9 An N (10 nm) double quantum well structure is adopted.
[0053]
Next, a ridge stripe with a width of about 1.7 μm is formed by p-Al by photolithography and etching. _0.1 Ga _0.9 In the N clad layer 56, it is formed by edging by RIBE (reactive ion beam etching) using chlorine ions from the p-GaN light guide layer 58 to a distance of 0.1 μm.
[0054]
Next, after forming the SiN film 52 on the entire surface by plasma CVD, unnecessary portions on the ridge are removed by photolithography and etching. Thereafter, the p-type impurities are activated by heat treatment in a nitrogen gas atmosphere. Thereafter, the epitaxial layer other than the portion including the light emitting region is etched away by RIBE using chlorine ions until the n-GaN buffer layer 70 is exposed. Thereafter, Ti / Al / Ti / Au as the n electrode 68 and Ni / Au as the p electrode 50 are vacuum-deposited and annealed in nitrogen to form an ohmic electrode. Resonator end faces are formed by cleavage.
[0055]
In the present embodiment, the oscillation wavelength is 440 nm, and the beam radiation angle full width at half maximum in the direction perpendicular to the junction is 34 degrees. It is also possible to use an insulating sapphire substrate. It is also possible to produce a similar structure on a conductive substrate such as SiC. Furthermore, dislocations in the oscillation stripe region can be reduced by using ELOG (epitaxially lateral over growth) (the above-mentioned reference: Matsushita, Optronics, (2000) No. 1, p. 62).
[0056]
Next, the optical system of the laser light source (GaN semiconductor laser) 211B according to the present embodiment will be described in detail. FIG. 5 shows a schematic diagram of an optical system of the laser light source 211B.
[0057]
As shown in FIG. 5, between the cylindrical lens 217 and the polygon mirror 218, a pinhole 102 in which a predetermined plate-like member is provided with a hole is provided. Thereby, the light of the LED light emitting component, that is, the stray light 198 is removed, and an image with high sharpness can be obtained.
[0058]
A half mirror 106 is provided between the collimator lens 213 and the cylindrical lens 217, and a monitor optical system 104 is provided on the light reflection side of the half mirror 106. The half mirror 106 and the monitor optical system 104 correspond to the monitor optical system of the present invention.
[0059]
The light amount of the light beam that has passed through the monitor optical system 104 is detected by the light receiving element 108. The B LD driving circuit 100 drives the laser light source 211B so that the light amount detected by the light receiving element 108 becomes a predetermined light amount. The monitor optical system 104 is configured to be a light beam substantially equivalent to the light beam that reaches the photographic paper 224, and includes a cylindrical lens 110 and a pinhole 112. Thereby, in the light receiving element 108, the light from which the stray light 198 is removed by the pinhole 112 can be detected, and the detection error can be suppressed. The pinhole 102 is not limited to the above position, and may be a position where the light beam converges.
[0060]
Further, as shown in FIG. 6, a half mirror 106 is provided between the pinhole 102 provided after the condensing optical system 114 including the collimator lens 213 and the cylindrical lens 217 and the polygon mirror 218, and is reflected by the half mirror 106. The received light may be detected by the light receiving element 108.
[0061]
(Configuration of control unit)
Next, the control unit of the laser printer unit 18 including a drive circuit that drives the laser light source 211B made of a GaN-based semiconductor laser will be described in detail.
[0062]
As shown in FIG. 7, the control unit according to the present embodiment includes a control circuit 80 including a microcomputer. The control circuit 80 is connected to a bus 88, and image data memories 74, 76, and 78 are connected to the bus 88. That is, image data memories 74, 76, and 78 are provided as memories for storing image data for recording an image on the photographic paper 224. The image data memory 74 is a memory for storing R color image data. Similarly, the image data memory 76 is a memory for storing G color image data, and the image data memory 78 is for storing B color image data. Memory.
[0063]
Also, an R LD drive circuit 96, a G LD drive circuit 98, and a B LD drive circuit 100 are connected to the bus 88. The R LD drive circuit 96 and the B LD drive circuit 100 are modulation circuits. 90 and 92 are connected to each other. That is, the semiconductor lasers 211R and 211B are intensity-binary modulated by generating a modulation signal (for example, a pulse width modulation signal) based on image data by the modulation circuits 90 and 92 and superimposing the modulation signal on the LD drive circuit. It has become so.
[0064]
Further, an AOM drive circuit 94 is connected to the bus 88, and the drive of the AOM 94 is controlled. That is, the laser light source 210G is indirectly modulated by the AOM 214G.
[0065]
Further, the bus 88 has a polygon motor driving circuit 82 for driving a polygon motor 83 for rotating the polygon mirror 218 and a photographic paper moving motor drive for driving a photographic paper moving motor 86 for moving the photographic paper 224. A circuit 84 is connected, and each is controlled by the control circuit 80.
[0066]
Next, the B LD driving circuit 100 will be described. As shown in FIG. 8, the B LD drive circuit 100 includes an output voltage setting unit 116, and the output voltage setting unit 116 includes a recording level setting unit 118, a non-recording level setting unit 120, and a current-voltage conversion circuit. 122 and the switch 124 are connected.
[0067]
The recording level setting unit 118 is connected to a recording level light amount memory 126 and a laser characteristic memory 128. A calibration unit 127 is connected to the recording level light amount memory 126, and an optimum light amount level (measured photosensitive level) set by calibration performed in advance by the calibration unit 127, that is, photographic paper 224 is predetermined. A light amount level for exposure at a level is stored in advance.
[0068]
The calibration unit 127 includes, for example, a colorimeter and the like. For example, a predetermined test pattern is recorded on the photographic paper 224, and the color is measured by the colorimeter, and an optimal light amount is obtained so as to be exposed at a predetermined level. Set the level. By performing this at any given interval, a good image can be obtained regardless of variations in the photographic paper 224 and changes with time of the apparatus.
[0069]
The laser characteristic memory 128 stores in advance the laser characteristics of the laser light source 211B, that is, the correspondence between the laser drive voltage (or drive current) and the optical output. Note that laser characteristics may be acquired by measuring the optical output while changing the drive voltage and stored in the laser characteristics memory 128. By performing this at any given interval, errors due to deterioration of the device over time can be suppressed.
[0070]
The recording level setting unit 118 obtains a drive voltage corresponding to the light amount level stored in the recording level light amount memory 126 from the laser characteristic stored in the laser characteristic memory 128, sets this as the recording level (voltage) VH, and outputs it. Output to the voltage setting unit 116.
[0071]
On the other hand, an extinction ratio memory 130 and a photosensitive material information memory 132 are connected to the non-recording level setting unit 120.
[0072]
The extinction ratio memory 130 has an extinction ratio, that is, a photosensitive level A (first reference photosensitive level) for exposing the photosensitive material (photographic paper) at a predetermined level and a non-photosensitive level B (first photosensitive level) for not exposing the photosensitive material. The ratio α (= B / A) to (2 reference photosensitive level) is stored in advance. The extinction ratio α can be obtained by experiment or the like, and is set so that the difference between the photosensitive level and the non-photosensitive level is minimized. Further, since the extinction ratio α differs depending on the type of photosensitive material, it is stored for each type of photosensitive material.
[0073]
The photosensitive material information memory 132 stores information for specifying the type of photosensitive material, that is, the photographic paper 224.
[0074]
The non-recording level setting unit 120 reads the extinction ratio corresponding to the type of photosensitive material stored in the photosensitive material information memory 132 from the extinction ratio memory 130, and the recorded extinction ratio and the recording recorded by the recording level setting unit 118. The non-recording level VL is calculated from the level VH and output to the output voltage setting unit 116. The non-recording level VL can be obtained by calculating α × VH.
[0075]
The output voltage setting unit 116 is connected to a current-voltage conversion circuit 122 connected to the light receiving element 108. The light receiving element 108 outputs a photocurrent corresponding to the detected light amount of the light beam to the current-voltage conversion circuit 122. In the current-voltage conversion circuit 122, the photocurrent from the light receiving element 108 is converted into a voltage and output to the output voltage setting unit 116. The output voltage setting unit 116 sets the output voltage VH ′ or the output voltage VL ′ so that the detected voltage becomes the recording level VH or the non-recording level VL set by the recording level setting unit 118, and outputs it to the switch 124. .
[0076]
In the switch 124, the output voltage VH ′ or the output voltage VL ′ is output to the drive circuit 134 for driving the laser light source 211B according to the image modulation signal (for example, pulse width modulation signal) output from the modulation circuit 92. Switching to As a result, the detection voltage is controlled to be VH or VL.
[0077]
As described above, since the non-recording level is set from the optimum recording level determined by calibration and the extinction ratio determined for each type of photosensitive material, the recording level and non-recording are determined regardless of the type of photosensitive material. The level is set optimally. Further, since the extinction ratio α is set so that the difference between the photosensitive level and the non-photosensitive level is minimized, the drive circuit 134 can switch between the recording level and the non-recording level at high speed.
[0078]
Next, the operation of the laser printer unit 18 according to the present embodiment will be described.
[0079]
When recording an image on the photographic paper 224, the control unit of the laser printer unit 18 records the image represented by the recording image data input from the image processing unit 16 on the photographic paper 224 by scanning exposure. Based on the image recording parameters input from the image processing unit 16, various corrections are performed on the recording image data to generate scanning exposure image data, which are stored in the image data memories 74, 76, and 78.
[0080]
Then, the polygon mirror 218 of the laser printer unit 18 is rotated in the direction of arrow A in FIG. 3, and a laser beam is emitted by flowing current to the semiconductor lasers of the laser light sources 211R, 210G, and 211B, and the generated scanning exposure is performed. A modulation signal is generated based on the image data, and the amplitude of the ultrasonic signal (high frequency signal) supplied to the AOM 214G is changed according to the level of the modulation signal to modulate the laser beam emitted from the AOM 214G as diffracted light. Therefore, a laser beam whose intensity is modulated in accordance with the density of the image to be recorded on the photographic paper 224 is emitted from the AOM 214G. This laser beam is applied to the photographic paper 224 through the plane mirror 215, the spherical lens 216, the cylindrical lens 217, the polygon mirror 218, the fθ lens 220, the cylindrical lens 221, the cylindrical mirror 222, and the folding mirror 223.
[0081]
For the laser light sources 211R and 211B, the laser beam is modulated by intensity binary modulation such as pulse width modulation. Accordingly, the laser light sources 211R and 211B emit laser beams modulated according to the density of the image to be recorded on the photographic paper 224. This laser beam is applied to the photographic paper 224 through the collimator lens 213, the cylindrical lens 217, the polygon mirror 218, the fθ lens 220, the cylindrical lens 221, the cylindrical mirror 222, and the folding mirror 223, respectively.
[0082]
Then, as the polygon mirror 218 rotates in the direction of arrow A in FIG. 3, the irradiation positions of the R, G, and B laser beams are scanned along the direction of arrow B in FIG. 3 is conveyed at a constant speed along the direction of arrow C in FIG. 3, each laser beam is sub-scanned, and an image (latent image) is recorded on the photographic paper 224 by scanning exposure.
[0083]
As described above, the recording level for binary modulation of the intensity of the laser beam from the laser light source 211B is set to the optimum recording level determined by calibration or the like, and the non-recording level is set to the set recording level. It is set from the level and the extinction ratio determined for each type of photosensitive material. Accordingly, the recording level and the non-recording level are optimally set regardless of the type of photosensitive material. Further, since the extinction ratio α is set so that the difference between the photosensitive level and the non-photosensitive level is minimized, the drive circuit 134 can switch between the recording level and the non-recording level at high speed. Can reduce the load.
[0084]
Note that the timing for modulating each laser beam in the scanning exposure and the conveyance timing of the photographic paper 224 in the direction of arrow C in FIG. 3 are determined based on the sensor output signal output from the SOS detection sensor 228.
[0085]
The photographic paper 224 on which an image is recorded by scanning exposure is sent to the processor unit 20 and subjected to color development, bleach-fixing, washing with water, and drying. As a result, an image is formed on the printing paper 224.
[0086]
Although the case where the present invention is applied to the laser light source 211B has been described above, the present invention is not limited thereto, and the present invention may be applied to the laser light sources 211R and 211G.
[0087]
【The invention's effect】
As described above, according to the present invention, there is an effect that it is possible to appropriately set the photosensitive level and the non-photosensitive level according to the type of the photosensitive material, and to suppress deterioration in image quality due to stray light.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a digital laboratory system according to an embodiment of the present invention.
FIG. 2 is a perspective view showing an appearance of a digital laboratory system according to the embodiment of the present invention.
FIG. 3 is a perspective view illustrating a schematic configuration of a laser printer unit.
FIG. 4 is a schematic cross-sectional view showing a detailed configuration of a GaN-based semiconductor laser.
FIG. 5 is a diagram showing a schematic configuration of an optical system of a laser light source.
FIG. 6 is a diagram showing a schematic configuration of an optical system of a laser light source.
FIG. 7 is a block diagram illustrating a control unit of the laser printer unit.
FIG. 8 is a diagram showing a schematic configuration of an LD drive circuit.
FIG. 9 is a view showing a schematic diagram when a GaN-based semiconductor laser is used as a light source of a silver salt exposure apparatus that performs spot scanning with a polygon or the like.
FIG. 10 is a graph showing the relationship between the light output of a spot and the drive current, and the relationship between the light output of a blurred pattern and the drive current.
11A is a diagram showing a striped pattern, and FIG. 11B is a diagram showing an example in which a blurred pattern is colored in the striped pattern.
12A is a diagram showing the laser characteristics of a conventional laser light source, and FIG. 12B is a diagram showing the laser characteristics of a GaN-based laser light source.
[Explanation of symbols]
10 Digital Lab System
14 Scanner
16 Image processing unit
18 Laser printer
20 Processor section
100 B LD drive circuit (drive means)
104 Monitor optical system
106 half mirror
108 Light receiving element (light receiving means)
118 Recording level setting section (setting means, photosensitive level input means)
120 Non-recording level setting section (setting means)
126 Recording level light quantity memory
128 Laser characteristic memory
130 Extinction ratio memory (ratio storage means)
132 Photosensitive material information memory
211BB B laser light source (GaN-based semiconductor laser)

Claims (3)

A GaN-based semiconductor laser that emits a light beam including laser light and emitted light other than laser light;
An optical system for imaging the light beam on a photosensitive material;
Scanning exposure means for scanning and exposing the photosensitive material with a light beam modulated according to image data to be recorded;
Input means for inputting the type of the photosensitive material;
In accordance with the type of the photosensitive material, setting means for setting a photosensitive level at which the photosensitive material is photosensitive and a non-photosensitive level at which the photosensitive material is not photosensitive;
Driving means for driving the GaN-based semiconductor laser so that the amount of the light beam applied to the photosensitive material is equal to or higher than the photosensitive level or equal to or lower than the non-photosensitive level according to the image data;
An image exposure apparatus comprising: The setting means includes
A ratio between a predetermined first reference photosensitive level for exposure at a predetermined level and a predetermined second reference photosensitive level for the photosensitive material not to be exposed is stored according to the type of the photosensitive material. Ratio storage means,
A photosensitive level input means for inputting a measured photosensitive level determined to be exposed at the predetermined level based on a colorimetric result of a test pattern recorded on the photosensitive material,
2. The image exposure according to claim 1, wherein the measured photosensitive level is set as the photosensitive level, and the non-photosensitive level is calculated from a ratio corresponding to the type of the photosensitive material and the photosensitive level. apparatus. A monitor optical system for monitoring the light beam; and a light receiving means for receiving the light beam transmitted through the monitor optical system,
The monitor optical system is configured such that a component ratio between the laser beam and the emitted light of a light beam received by the light receiving unit is substantially the same as the component ratio on the photosensitive material, and the driving unit includes: 3. The image exposure apparatus according to claim 1, wherein the GaN-based semiconductor laser is driven so that the light amount of the light beam received by the light receiving means becomes the photosensitive level or the non-photosensitive level.

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