JP2007200952A - Image exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the responsibility of a semiconductor laser element while enabling to use a spontaneous emission region of the semiconductor laser element in an image exposure apparatus which uses the semiconductor laser element as a light source. <P>SOLUTION: The image exposure apparatus comprises the semiconductor laser element, a driving circuit 45 which directly modulates the semiconductor laser element by an analog signal whose signal level changes based on image data for which prints are to be fabricated, and a scanning means 13 which scans the light emitted from the semiconductor laser element on a photosensitive material PS. The driving circuit 45 sets up the light output of the semiconductor laser element, so that the average intensity of the light emitted from the semiconductor laser element for one pixel formed on the photosensitive material PS may be in the spontaneous emission region and in the lasing region of the semiconductor laser element, and that the peak intensity of the light emitted from the semiconductor laser element within an exposure range for one pixel may reach within the lasing region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor laser element, a drive circuit that directly modulates the semiconductor laser element with an analog signal whose signal level changes based on image data to be produced as a photographic print, and light emitted from the semiconductor laser element as a photographic photosensitive material The present invention relates to an image exposure apparatus provided with scanning means for scanning above.

Such an image exposure apparatus is an apparatus for exposing and forming an image by scanning a light beam generated by light emitted from a semiconductor laser element on a photographic photosensitive material.
The semiconductor laser element serving as the light source has a light output-drive current characteristic as shown in FIG. 9, and starts laser oscillation when the threshold current shown as Ith in FIG. In a smaller region, laser oscillation does not occur, and the operation state is the same as that of the LED.
An operation region in which the drive current is smaller than Ith and the optical output of the semiconductor laser element is smaller than Pth, which is the optical output corresponding to Ith, is called a spontaneous emission region (or spontaneous emission light region). The operating region where the optical output of the semiconductor laser element is larger than Pth is called a laser oscillation region.
In an image exposure apparatus that uses a semiconductor laser element having such characteristics as a light source, when the semiconductor laser element is driven only in the laser oscillation region, the ratio of the highest light output to the lowest light output is not sufficiently large, Since gradation expression becomes difficult, it is considered that a proper gradation expression can be realized by driving a semiconductor laser element to emit light even in a spontaneous emission region as described in Patent Document 1 below. Yes.
Japanese Patent Publication No. 7-71176

However, when the semiconductor laser device is driven in the spontaneous emission region as in the conventional configuration, the response speed of the semiconductor laser device is reduced. For example, in a so-called APC circuit, an optical output setting signal as shown in FIG. Is added, the output light intensity of the actual semiconductor laser element becomes an output waveform as shown in FIG. 10B, and an appropriate exposure amount for each pixel is set in the image formed on the photographic photosensitive material. It becomes difficult.
The present invention has been made in view of such circumstances, and an object thereof is to improve the responsiveness of the semiconductor laser element while making it possible to use the spontaneous emission region of the semiconductor laser element.

  According to a first aspect of the present application, there is provided a semiconductor laser device, a drive circuit that directly modulates the semiconductor laser device with an analog signal whose signal level changes based on image data of a photographic print production target, and an output of the semiconductor laser device. In the image exposure apparatus having scanning means for scanning the photographic photosensitive material, the drive circuit has an average intensity of the emitted light of the semiconductor laser element in one pixel formed on the photographic photosensitive material. The light output of the semiconductor laser element is set so as to extend over both the spontaneous emission area and the laser oscillation area of the semiconductor laser element, and the entire pixel area of the spontaneous emission area and the laser oscillation area corresponds to the one pixel. Is set so that the peak intensity of the emitted light from the semiconductor laser element within the exposure range reaches the laser oscillation region.

  That is, as a characteristic when driving a semiconductor laser element, “when the emission light intensity of the semiconductor laser element is lowered, the drive current of the drive circuit changes (falls) regardless of the spontaneous emission region or the laser oscillation region. "Responds at high speed", "The response speed when raising the emitted light intensity of the semiconductor laser element from the spontaneous emission region to the spontaneous emission region is slow, but the drive circuit is driven to reach the laser oscillation region even a little from the spontaneous emission region Focusing on the fact that it responds at a fast response speed when the current is changed, the average intensity of the emitted light of the semiconductor laser element for one pixel formed on the photographic photosensitive material is in the spontaneous emission region. Even if the light intensity corresponds to the light intensity of 1 pixel, the average intensity within the exposure range for one pixel is the same as the exposure range for one pixel while maintaining the light intensity in the spontaneous emission region. By at a portion to set the optical output of the semiconductor laser device so as to reach the laser oscillation region, thereby speeding the actual response of the emission intensity of the semiconductor laser element for the setting.

According to a second invention of the present application, in addition to the configuration of the first invention, the drive circuit has a triangular wave shape as an optical output setting signal of the semiconductor laser element within the exposure range for one pixel, It is configured to include a sawtooth or sinusoidal signal.
In other words, by including a triangular, sawtooth or sinusoidal signal in the light output setting signal for setting the emitted light intensity of the semiconductor laser element, laser oscillation occurs in a part of the exposure range for one pixel. The signal level can be set high so as to reach the region.
As a result, the semiconductor laser element can reach the laser oscillation region in a part of the exposure range for one pixel while maintaining the light intensity in the spontaneous emission region as the average intensity within the exposure range for one pixel. Can be set.

  According to a third invention of the present application, in addition to the configuration of the first invention, the drive circuit is provided with a high-frequency superposition circuit for reducing noise of the semiconductor laser element, and the drive circuit includes the natural circuit. The peak intensity of the emitted light of the semiconductor laser element within the exposure range for one pixel in the state where the output of the high-frequency superimposing circuit is applied to the semiconductor laser element in the entire light emitting region and the laser oscillation region The output amplitude of the high frequency superimposing circuit is set so as to reach the laser oscillation region.

When a semiconductor laser element is used as a light source, a high-frequency superposition circuit is often provided in order to reduce mode hop noise of the semiconductor laser element.
The amplitude of the signal output from this high-frequency superimposing circuit is usually set in consideration of the rating of the semiconductor laser element and the noise reduction effect. In addition, in addition to these, the spontaneous emission region and the laser oscillation region The high frequency superposition circuit is arranged so that the peak value of the emitted light of the semiconductor laser element within the range of the one pixel reaches the laser oscillation area in the entire region with the output of the high frequency superposition circuit applied to the semiconductor laser element. The output amplitude is set.
That is, the output amplitude is set so that the high-frequency superimposing circuit for reducing the mode hop noise also contributes to the improvement of the response when the semiconductor laser element is directly modulated using the spontaneous emission region. .

  According to a fourth invention of the present application, in addition to the configuration of the first invention, the drive circuit is provided with a high-frequency superimposing circuit for reducing noise of the semiconductor laser element, and the drive circuit includes a setting light. In a low light output area below the output, the light output setting signal of the semiconductor laser element within the exposure range for one pixel is configured to include a triangular wave-shaped, sawtooth wave-shaped or sine wave-shaped signal, In a high light output region exceeding the set light output, with the output of the high frequency superimposing circuit applied to the semiconductor laser element, the peak intensity of the emitted light of the semiconductor laser element within the exposure range for the one pixel is The output amplitude of the high-frequency superposition circuit is set so as to reach the laser oscillation region.

In other words, when the high-frequency superimposing circuit for reducing the mode hop noise of the semiconductor laser device is also used for improving the response when driving the semiconductor laser device using the spontaneous emission region, the peak intensity of the high-frequency signal is set to the laser In view of reaching the oscillation region, there may be a case where the average light intensity within the exposure range for the one pixel is not sufficiently low.
Therefore, in the low light output region, the responsiveness is not improved by the high-frequency superimposing circuit, but the triangular laser, sawtooth wave, or sine wave signal that partially reaches the laser oscillation region is included. By improving the responsiveness, the average light intensity within the exposure range for the one pixel can be set lower.

According to the first aspect of the invention, the average intensity within the exposure range for one pixel reaches the laser oscillation region in a part of the exposure range for one pixel while maintaining the light intensity in the spontaneous emission region. By setting the light output of the semiconductor laser element so as to speed up the actual response of the emitted light intensity of the semiconductor laser element to the setting, so that the spontaneous emission region of the semiconductor laser element can be used, The response of the semiconductor laser element can be improved.
In addition, according to the second aspect of the present invention, an average signal within the exposure range for one pixel can be obtained by including a triangular, sawtooth or sinusoidal signal in the signal for setting the optical output of the semiconductor laser element. As the intensity, the light output of the semiconductor laser element can be set so as to reach the laser oscillation area in a part of the exposure range for one pixel while maintaining the light intensity in the spontaneous emission area.

According to the third aspect of the invention, the high-frequency superimposing circuit for reducing the mode hop noise also contributes to the improvement of the response when the semiconductor laser device is directly modulated using the spontaneous emission region. Thus, the device configuration can be simplified.
According to the fourth aspect of the invention, in the low light output region, the responsiveness is not improved by the high frequency superimposing circuit, but a triangular wave shape, a sawtooth wave shape or a sine wave shape partially reaching the laser oscillation region. By improving the responsiveness of the semiconductor laser element including the above signal, the average light intensity within the exposure range for the one pixel can be set lower, and the output adjustment range of the light beam applied to the photographic photosensitive material can be increased. Widely secured.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which an image exposure apparatus of the present invention is provided in a photographic print system will be described based on the drawings.
<First Embodiment>
The photo print system DP exemplified in the first embodiment is known as a so-called digital minilab machine, and as shown in the block diagram of FIG. 2, a photo print is prepared with various image data input devices. An image input device IR that captures image data for image processing, and an exposure / development device EP that performs exposure processing on photographic paper 2 that is an example of a photographic photosensitive material PS based on the image data input by the image input device IR; It is composed of

[Schematic configuration of image input device IR]
As schematically shown in FIG. 2, the image input device IR includes a film scanner 3 that reads a frame image of a photographic film and outputs it as digital image data, a memory card reader, a magneto-optical disk drive, a CD-R drive, and the like. An external input / output device 4 provided with the image data input device, and a main control device 5 which is constituted by a personal computer and controls the film scanner 3 and the external input / output device 4 and manages the entire photo print system DP. In addition, the main control device 5 includes a monitor 5a for displaying a simulated image simulating a finished print image and various control information, manual setting of exposure conditions, etc., and input operation of control information. Is connected to an operation console 5b.

[Overall configuration of exposure / development apparatus EP]
The exposure / development apparatus EP includes an image exposure apparatus EX that exposes and forms an image on the emulsion surface of the photographic paper 2 inside the housing, and a development processing apparatus PP that develops the photographic paper 2 exposed by the image exposure apparatus EX. And a photographic paper transport system PT for transporting the photographic paper 2 drawn out from the photographic paper magazine 6 to the development processing apparatus PP by a number of transport rollers 9 or the like.
Although not shown, a sorter is provided outside the housing of the exposure / development apparatus EP to classify the photographic paper 2 that has been developed and dried by the development processor PP into orders. A conveyor 10 for conveying the photographic paper 2 discharged from the PP photographic paper discharge port to the sorter is provided on the upper surface of the casing.
Further, in the middle of the conveyance path of the photographic paper conveyance system PT, a cutter 11 for cutting the long photographic paper 2 drawn from the photographic paper magazine 6 into a set print size, and a plurality of conveyance rows of the photographic paper 2 are conveyed. A sorting device 12 for sorting into rows is provided.

[Configuration of image exposure apparatus EX]
The image exposure apparatus EX is composed mainly of an exposure unit 13 that exposes and forms an image on the photographic paper 2 and an exposure control apparatus 14 that controls the exposure unit 13.
[Configuration of Exposure Unit 13]
The exposure unit 13 employs a so-called laser beam scanning exposure method in which an intensity-modulated light beam is scanned on the photographic paper 2 and an image is exposed and formed on the photographic paper 2, and the schematic configuration thereof is shown in FIG. Shown in block diagram.
The exposure unit 13 includes a red light source device 21, a green light source device 22, a blue light source device 23, and an acoustic for intensity-modulating the light beams emitted from the green light source device 22 and the blue light source device 23. The optical modulation element 24 (hereinafter abbreviated as “AOM element 24”), a mirror 25 that bends the optical path of the light beam, a spherical lens 26, a cylindrical lens 27, and a motor (not shown) are rotationally driven. A polygon mirror 28 and a lens group 29 having an f-θ characteristic and a surface tilt correction function are provided.

[Configuration of Light Source Device 21 for Red]
As schematically shown in FIG. 3, the red light source device 21 includes a semiconductor laser element 31 that emits red laser light as a light source, a condensing lens 32 that condenses the emitted light from the semiconductor laser element 31, and a semiconductor laser. A beam splitter 33 for branching a part of the emitted light from the element 31 for detecting the amount of emitted light, and a photodiode 34 for detecting the light intensity of the red laser light branched by the beam splitter 33 are provided. .
Therefore, the exposure unit 13 functions as a scanning unit that scans the light emitted from the semiconductor laser element 31 on the photographic paper 2.

[Configuration of Green Light Source Device 22 and Blue Light Source Device 23]
Although the green light source device 22 and the blue light source device 23 have the same basic configuration and are not illustrated, a near infrared semiconductor laser element that emits near infrared laser light and a near infrared semiconductor laser element The second harmonic generation device for generating the second harmonic of the emitted laser beam and other optical components are included.
The green light source device 22 and the blue light source device 23 differ only in the emission wavelength of the near-infrared semiconductor laser element, and the other configurations are common, and both of them emit light emitted from the near-infrared semiconductor laser element. A light beam having a half wavelength is emitted.

[Configuration of Exposure Control Device 14]
As schematically shown in FIG. 1, the exposure control device 14 exposes red, green and blue exposure image data input from the image input device IR in order to control the exposure unit 13 having the above configuration. A look-up table 41 for correcting image data in consideration of the exposure characteristics of the unit 13, an image data memory 42 for storing the image data corrected by the look-up table 41 for each of red, green and blue colors, red, A D / A converter 43 which is provided for each color of green and blue and D / A converts the output data of the image data memory 42, and AOM modulated in accordance with an input signal from the D / A converter 43 for green and blue An AOM control circuit 44 that generates a drive signal for the element 24, and red light according to an image signal input from the D / A converter 43 for red A drive circuit 45 for modulating the driving current of the semiconductor laser element 31 of the device 21 is provided.

  As schematically shown in FIG. 3, the drive circuit 45 includes a high-frequency superimposing circuit 51 for reducing the mode hop noise of the semiconductor laser element 31 and a current / voltage for converting the output current of the photodiode 34 into a voltage signal. A conversion circuit 52, a light output setting waveform generation circuit 54 that generates a setting signal for the output intensity of the semiconductor laser element 31 based on the image signal input from the D / A converter 43, and an output light intensity of the semiconductor laser element 31. Is provided with an operational amplifier 53 for controlling the drive current of the semiconductor laser element 31 so that the output current of the optical output setting waveform generation circuit 54 changes following the output signal. A transistor or the like for adjusting the energization current of the element 31 is provided, and the photodiode 34 and the drive circuit of the red light source device 21 are provided. Constitute a so-called APC circuit by 5 of the current / voltage conversion circuit 52 a detection signal of the emitted light intensity of the semiconductor laser device 31 to form a feedback loop for feeding back to the input side of the operational amplifier 53.

As described above, the operational amplifier 53 performs the APC operation so that the input signal from the current / voltage conversion circuit 52 matches the output signal of the optical output setting waveform generation circuit 54. When APC is applied based on the output, the light output of the semiconductor laser element 31 does not accurately respond to the image signal output from the D / A converter 43 in the spontaneous emission region. APC is applied by converting into a signal waveform for improving the response of the actual optical output of the semiconductor laser element 31 to the optical output setting signal input to the operational amplifier 53.
Specifically, the optical output setting waveform generation circuit 54 generates a triangular waveform signal waveform TR as shown in FIG. 4A based on the image signal input from the D / A converter 43, and the operational amplifier 53. It is included in the optical output setting signal to be output to.

FIG. 4A shows an exposure range for one pixel extracted from the scanning of the light beam onto the photographic paper 2 by the exposure unit 13, and starts from time “ts” and ends at time “te”. Within the exposure range for one pixel, a triangular waveform signal waveform TR is generated with a width from time “t0” to time “t1”.
4B shows a signal P _TR (by the high frequency superposition circuit 51) that detects the actual emitted light intensity of the semiconductor laser element 31 when the optical output setting signal having the waveform of FIG. FIG. 4B shows a schematic shape corresponding to the lowest light output set by the image signal input from the D / A converter 43. Is. This minimum light output corresponds to a weak light output near the boundary of whether or not the photographic paper 2 can be exposed to color.

The optical output setting waveform generation circuit 54 is the optical output intensity at the threshold current (Ith in FIG. 9) of the semiconductor laser element 31 in the vicinity of the peak intensity of the triangular wave detection signal even at the minimum optical output. The height of the signal waveform TR of the triangular wave in FIG. 4A so that the peak intensity of the emitted light of the semiconductor laser element 31 within the range of one pixel reaches the laser oscillation region so as to exceed “Pth”. Is set.
Thus, even if reached lasing region peak intensity of the light emitted from the semiconductor laser element 31, the light intensity indicated average light intensity within the exposure range of one pixel in the broken line P _AV in Fig 4 (b) Thus, the average light intensity is the light intensity in the spontaneous emission region below “Pth”.
In a region where the image signal is larger than the minimum light output, the light output setting waveform generation circuit 54 sets the signal level of the peak of the triangular wave in FIG. 4A to be high according to the signal level. This is the same even when entering the laser oscillation region where the average light intensity exceeds “Pth”. Information indicating the relationship between the signal level of the image signal and the height of the triangular wave is set in advance and held by the light output setting waveform generation circuit 54.

  Accordingly, the drive circuit 45 directly modulates the semiconductor laser element 31 with an analog signal whose signal level changes based on the image data to be produced as a photographic print, and the semiconductor for one pixel formed on the photographic paper 2. The light output of the semiconductor laser element is set so that the average intensity of the emitted light from the laser element 31 extends over both the spontaneous emission area and the laser oscillation area of the semiconductor laser element 31, and all of the spontaneous emission area and the laser oscillation area are set. In the region, the peak intensity of the emitted light of the semiconductor laser element 31 within the exposure range for one pixel is set to reach the laser oscillation region.

Since the output of the high-frequency superimposing circuit 51 is also added to the output current of the operational amplifier 53, the peak intensity of the emitted light from the semiconductor laser element 31 within the exposure range for one pixel is increased accordingly, and strictly. FIG. 4B shows a state in which the peak intensity of the emitted light from the semiconductor laser element 31 within the exposure range for one pixel reaches the laser oscillation region even if the peak light intensity in FIG. 4B is slightly lower than “Pth”. It becomes.
Further, since the output signal of the high frequency superimposing circuit 51 has a frequency sufficiently higher than the response frequency band of the feedback loop composed of the photodiode 34 and the current / voltage conversion circuit 52, the high frequency superimposing circuit 51 is a semiconductor using the operational amplifier 53. The output control of the laser element 31 is not affected.

[Summary of photo print production operation]
When the operator inputs image data to be printed from the film scanner 3 or the external input / output device 4, image processing or the like is appropriately performed, and the image data for exposure after image processing is transmitted to the lookup table 41.
Based on the red, green and blue exposure image data input from the image input device IR, the red, green and blue light beams whose intensity is modulated by the AOM element 24 and the drive circuit 45 pass through each optical component. Then, the light beam irradiated on the reflection surface of the polygon mirror 28 and reflected by the reflection surface of the polygon mirror 28 that is driven to rotate is condensed on the photographic paper 2 by the lens group 29. The scanning direction (main scanning direction) of the light beam is orthogonal to the conveyance direction (sub-scanning direction) of the photographic paper 2, and a photographic image to be printed on the photographic paper 2 by the scanning of the light beam and the conveyance movement of the photographic paper 2 Is exposed and formed as a latent image. This is developed in the development processing apparatus PP and finished as a photographic print.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings.
The second embodiment differs from the first embodiment only in the signal waveform of the light output setting signal generated by the light output setting waveform generation circuit 54, and all other components are the same as those in the first embodiment. is there.
In the second embodiment, the light output setting waveform generation circuit 54 outputs a signal waveform SN having a sine wave shape shown in FIG.
5 (a) and 5 (b) correspond to FIGS. 4 (a) and 4 (b), respectively, and FIG. 5 (a) is an exposure unit similar to FIG. 4 (a). 13, the exposure range for one pixel is extracted from the scanning of the light beam on the photographic paper 2, and the exposure range for one pixel starting from time “ts” and ending at time “te”. The signal waveform SN having a sine wave shape (only on the plus side) is generated with a width from time “t0” to time “t1”.
FIG. 5B shows a signal P _SN (by the high frequency superposition circuit 51) that detects the actual emitted light intensity of the semiconductor laser element 31 when the optical output setting signal having the waveform of FIG. FIG. 5B shows a schematic shape corresponding to the minimum light output set by the image signal input from the D / A converter 43. Is. This minimum light output corresponds to a weak light output near the boundary of whether or not the photographic paper 2 can be exposed to color.

The optical output setting waveform generation circuit 54 is the optical output intensity at the threshold current (Ith in FIG. 9) of the semiconductor laser element 31 in the vicinity of the peak intensity of the sinusoidal detection signal even at the minimum optical output. The sine wave signal waveform SN of FIG. 5A is set so as to exceed “Pth”, that is, so that the peak intensity of the emitted light of the semiconductor laser element 31 within the range of one pixel reaches the laser oscillation region. The height is set.
Thus, even though the peak intensity of the light emitted from the semiconductor laser element 31 reaches the lasing region, the light intensity indicated average light intensity within the exposure range of one pixel in the broken line P _AV in FIG 5 (b) Thus, the average light intensity is the light intensity in the spontaneous emission region below “Pth”.
In a region where the image signal is larger than the minimum light output, the light output setting waveform generation circuit 54 sets so that the signal level of the peak of the sine wave in FIG. This is the same even when entering the laser oscillation region where the average light intensity exceeds “Pth”. Information indicating the relationship between the signal level of the image signal and the height of the sine wave is set in advance and held by the light output setting waveform generation circuit 54.

  Accordingly, the drive circuit 45 directly modulates the semiconductor laser element 31 with an analog signal whose signal level changes based on the image data to be produced as a photographic print, and the semiconductor for one pixel formed on the photographic paper 2. The light output of the semiconductor laser element is set so that the average intensity of the emitted light from the laser element 31 extends over both the spontaneous emission area and the laser oscillation area of the semiconductor laser element 31, and all of the spontaneous emission area and the laser oscillation area are set. In the region, the peak intensity of the emitted light of the semiconductor laser element 31 within the exposure range for one pixel is set to reach the laser oscillation region.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to the drawings.
The third embodiment also differs from the first embodiment only in the signal waveform of the optical output setting signal generated by the optical output setting waveform generation circuit 54, and all other components are common to the first embodiment. is there.
In the third embodiment, the light output setting waveform generation circuit 54 outputs a signal waveform SW having a sawtooth waveform shown in FIG.
6 (a) and 6 (b) correspond to FIGS. 4 (a) and 4 (b), respectively, and FIG. 6 (a) is an exposure unit similar to FIG. 4 (a). 13, the exposure range for one pixel is extracted from the scanning of the light beam on the photographic paper 2, and the exposure range for one pixel starting from time “ts” and ending at time “te”. A signal waveform SW having a sawtooth waveform with a width from time “t0” to time “t1” is generated.
6B shows a signal P _SW (detected by the high-frequency superposition circuit 51) in which the actual output light intensity of the semiconductor laser element 31 is detected when the optical output setting signal having the waveform shown in FIG. FIG. 6B shows a schematic shape corresponding to the minimum light output set by the image signal input from the D / A converter 43. Is. This minimum light output corresponds to a weak light output near the boundary of whether or not the photographic paper 2 can be exposed to color.

The optical output setting waveform generation circuit 54 uses the optical output intensity at the threshold current of the semiconductor laser element 31 (Ith in FIG. 9) near the peak intensity of the sawtooth waveform detection signal even at the minimum optical output. The signal waveform of the sawtooth wave of FIG. 6A so as to exceed a certain “Pth”, that is, so that the peak intensity of the emitted light of the semiconductor laser element 31 within the range of one pixel reaches the laser oscillation region. SW height is set.
Thus, even though the peak intensity of the light emitted from the semiconductor laser element 31 reaches the lasing region, the light intensity indicated average light intensity within the exposure range of one pixel in the broken line P _AV in FIG 6 (b) Thus, the average light intensity is the light intensity in the spontaneous emission region below “Pth”.
In a region where the image signal is larger than the minimum light output, the light output setting waveform generation circuit 54 sets the signal level of the peak of the sawtooth wave in FIG. 6A to be high according to the signal level. . This is the same even when entering the laser oscillation region where the average light intensity exceeds “Pth”. Information indicating the relationship between the signal level of the image signal and the height of the sawtooth wave is preset and held by the light output setting waveform generation circuit 54.

  Accordingly, the drive circuit 45 directly modulates the semiconductor laser element 31 with an analog signal whose signal level changes based on the image data to be produced as a photographic print, and the semiconductor for one pixel formed on the photographic paper 2. The light output of the semiconductor laser element is set so that the average intensity of the emitted light from the laser element 31 extends over both the spontaneous emission area and the laser oscillation area of the semiconductor laser element 31, and all of the spontaneous emission area and the laser oscillation area are set. In the region, the peak intensity of the emitted light of the semiconductor laser element 31 within the exposure range for one pixel is set to reach the laser oscillation region.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described with reference to the drawings.
In the fourth embodiment, the optical output setting waveform generation circuit 54 of the first to third embodiments is not provided, and the image signal output from the D / A converter 43 is input to the operational amplifier 53 as it is, and the optical output setting waveform is output. The function performed by the generation circuit 54 is configured to be imposed on the high-frequency superposition circuit 51.
Therefore, the high frequency superimposing circuit 51 has a function of improving the response characteristics of the semiconductor laser element 31 in addition to the function as a circuit for reducing the mode hop noise of the semiconductor laser element 31 which is the original function.
Except for the point that the optical output setting waveform generation circuit 54 is not provided and the configuration of the high-frequency superposition circuit 51 is different, the fourth embodiment is completely the same as the first to third embodiments.

In the high frequency superimposing circuit 51 of the fourth embodiment, as shown in FIG. 7 showing the driving circuit 45 of the fourth embodiment corresponding to FIG. 3, the amplitude of the high frequency signal superimposed by the control signal from the outside is set. An amplitude adjustment circuit 51a to be changed is provided.
FIG. 8A shows an exposure range for one pixel extracted from the scanning of the light beam onto the photographic paper 2 by the exposure unit 13, and starts from time “ts” and ends at time “te”. The waveform HF of the drive current supplied to the semiconductor laser element 31 in the exposure range for one pixel is shown. That is, the signal waveform HF including the current component supplied from the operational amplifier 53 and the high frequency fluctuation component supplied from the high frequency superimposing circuit 51 is shown.
Note that the high-frequency signal component from the high-frequency superimposing circuit 51 shown in FIG. 8A is shown with a frequency that is a fraction of the actual frequency in order to make the drawing easier to see.

FIG. 8B shows a schematic shape of the signal P _HF in which the actual emitted light intensity of the semiconductor laser element 31 is detected when the semiconductor laser element 31 is driven with the drive current having the waveform of FIG. Yes. Depending on the high frequency characteristics of the semiconductor laser element 31, the peak to peak of the high frequency component in FIG. 8B may be smaller than that shown in the figure.
8A and 8B correspond to the minimum light output set by the image signal input from the D / A converter 43, and this minimum light output is the print. This corresponds to a weak light output near the boundary of whether or not the paper 2 can be exposed to color.
Even at this minimum light output, the peak intensity of the high-frequency component in FIG. 8B exceeds “Pth” that is the light output intensity at the threshold current of the semiconductor laser element 31 (Ith in FIG. 9). That is, the peak of the high-frequency component is also the threshold current in the drive current of FIG. 8A so that the peak intensity of the emitted light from the semiconductor laser element 31 within the range of one pixel reaches the laser oscillation region. The height exceeds (Ith in FIG. 9).

Thus, even if peak intensity laser oscillation region of the light emitted from the semiconductor laser element 31, the light intensity indicated average light intensity within the exposure range of one pixel in the broken line P _AV in FIG 8 (b) Thus, the average light intensity is the light intensity in the spontaneous emission region below “Pth”. In other words, with respect to the signal level of the image signal indicated by the broken line P _AV, the amplitude adjustment circuit 51a sets the amplitude of the high frequency components shown in FIG. 8 (a), the in relationship.
The amplitude adjustment circuit 51a of the high-frequency superimposing circuit 51 is in a state where the peak intensity of the emitted light from the semiconductor laser element 31 within the range of one pixel reaches the laser oscillation region as the image signal increases from the minimum light output. While maintaining the above, the amplitude of the high frequency component applied to the drive current of the semiconductor laser element 31 is reduced. However, the amplitude of the high-frequency component is maintained at a level at which the mode-hop noise suppression effect can be maintained at the minimum.

In order for the amplitude adjustment circuit 51a to set the amplitude of the high-frequency signal as described above, information indicating the correspondence between the signal level of the image signal and the amplitude to be set is obtained in advance and held as a data table or the like.
Of course, if the optical output rating of the semiconductor laser element 31 has a margin, the image signal may increase from the minimum optical output, or the amplitude of the high frequency component shown in FIG.
When the drive circuit 45 performs the above-described operation, the drive circuit 45 directly modulates the semiconductor laser element 31 with an analog signal whose signal level changes based on the image data to be produced as a photographic print. The light output of the semiconductor laser element is set so that the average intensity of the emitted light of the semiconductor laser element 31 in one pixel formed extends over both the spontaneous emission region and the laser oscillation region of the semiconductor laser element 31, and In all areas of the spontaneous emission region and the laser oscillation region, the peak intensity of the emitted light of the semiconductor laser element 31 within the exposure range for one pixel is obtained with the output of the high-frequency superimposing circuit 51 applied to the semiconductor laser element 31. It is set to reach the laser oscillation region.

<Other embodiments>
Hereinafter, other embodiments of the present invention will be listed.
(1) In the fourth embodiment, the high frequency superposition circuit is arranged so that the peak intensity of the emitted light from the semiconductor laser element 31 exceeds “Pth” and reaches the laser oscillation region in the entire range of the spontaneous emission region and the laser oscillation region. 51, the amplitude of the high frequency component added to the drive current of the semiconductor laser element 31 is set. The drive circuit 45 is a semiconductor laser within the exposure range for one pixel in a low light output region below the set light output. The optical output setting signal of the element 31 is configured to include a triangular waveform as shown in FIG. 4A, a sawtooth waveform as shown in FIG. 6A, or a sine waveform as shown in FIG. In the high light output region exceeding the set light output, the peak intensity of the emitted light of the semiconductor laser element 31 within the range of the one pixel in the state where the output of the high frequency superimposing circuit 51 is applied to the semiconductor laser element 31. Is It may be configured to set the output amplitude of the high-frequency superimposing circuit 51 so as to reach a The oscillation region.

To be more specific, the example, in the fourth embodiment, if you want to set the minimum light output to further lower output than the average light intensity indicated by the dashed line P _AV of FIG. 8 (b), in FIG. 7, D The optical output setting waveform generation circuit 54 in the first to third embodiments is placed between the branch point where the image signal input from the / A converter 43 branches toward the high frequency superimposing circuit 51 and the input of the operational amplifier 53. arrangement and, as the set light output average optical intensity shown by the dashed line P _AV of FIG. 8 (b), the signal level of the image signal input from the D / a converter 43 is, in the setting light output following the light output region Operates the light output setting waveform generation circuit 54 as described in the first to third embodiments, and in the high light output region exceeding the setting light output, the light output setting waveform generation circuit 54 The dynamic is stopped as it passes the image signal input from the D / A converter 43 to perform the operations described in the high-frequency superposing circuit 51 in the fourth embodiment.
Of course, the setting light output for switching operation as described above, may be greater than the average light intensity indicated by the dashed line P _AV of FIG 8 (b).

(2) In the first to third embodiments described above, the triangular wave shape as shown in FIG. 4A, the sine wave shape as shown in FIG. Although it has been described that the signal having the sawtooth waveform as shown in (a) is generated by the optical output setting waveform generation circuit 54, the signal level of the image signal input from the D / A converter 43 is the semiconductor laser. When the average intensity of the emitted light from the element 31 is at a level entering the laser oscillation region, the light output setting waveform generation circuit 54 is configured not to generate a waveform such as a triangular wave but to pass the input image signal as it is. You may do it.

(3) In the first to third embodiments, the case where the height of the signal waveform such as the triangular wave shape of FIG. 4A is set by the image signal input from the D / A converter 43 is illustrated. Alternatively, the digital image data output from the image data memory 42 may be used as it is to set the height of the signal waveform such as the triangular wave shape of FIG.
(4) In the first to fourth embodiments, the case where the present invention is applied to drive the semiconductor laser element 31 of the red light source device 21 is exemplified. However, the green light source device 22 and the blue light source are used. The apparatus 23 may also include a green semiconductor laser element and a blue semiconductor laser element as light sources, respectively, and the present invention may be applied to drive these semiconductor laser elements.

1 is a schematic configuration diagram of an image exposure apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a photo print system according to an embodiment of the present invention. 1 is a schematic configuration diagram of a drive circuit and a light source device according to first to third embodiments of the present invention. Signal explanatory diagram according to the first embodiment of the present invention Signal explanatory diagram according to the second embodiment of the present invention Signal explanatory diagram according to the third embodiment of the present invention The schematic block diagram of the drive circuit and light source device concerning 4th Embodiment of this invention. Signal explanatory diagram according to the fourth embodiment of the present invention The figure which shows the optical output-drive current characteristic of a semiconductor laser element Signal explanatory diagram for explaining the operation in the spontaneous emission region

Explanation of symbols

13 Scanning means 31 Semiconductor laser element 45 Drive circuit 51 High frequency superposition circuit PS Photosensitive material

Claims (4)

A semiconductor laser element, a driving circuit that directly modulates the semiconductor laser element with an analog signal whose signal level changes based on image data to be produced as a photographic print, and scanning light emitted from the semiconductor laser element on a photographic photosensitive material An image exposure apparatus provided with a scanning means,
The driving circuit is configured so that an average intensity of emitted light of the semiconductor laser element for one pixel formed on a photographic photosensitive material extends over both a spontaneous emission region and a laser oscillation region of the semiconductor laser element. The light output of the semiconductor laser element is set within the laser oscillation region within the exposure range for the one pixel in the entire light emission region and the laser oscillation region. An image exposure device that is set to reach the inside.   2. The drive circuit is configured to include a signal having a triangular wave shape, a sawtooth wave shape, or a sine wave shape as an optical output setting signal of the semiconductor laser element within the exposure range for one pixel. Image exposure equipment. The drive circuit is provided with a high-frequency superposition circuit for noise reduction of the semiconductor laser element,
The drive circuit includes the semiconductor laser within an exposure range of the one pixel in a state where the output of the high-frequency superimposing circuit is applied to the semiconductor laser element in all areas of the spontaneous emission region and the laser oscillation region. 2. The image exposure apparatus according to claim 1, wherein an output amplitude of the high frequency superimposing circuit is set so that a peak intensity of light emitted from the element reaches the laser oscillation region. The drive circuit is provided with a high-frequency superposition circuit for noise reduction of the semiconductor laser element,
The driving circuit outputs a signal having a triangular wave shape, a sawtooth wave shape, or a sine wave shape as a light output setting signal of the semiconductor laser element within the exposure range for one pixel in a low light output region equal to or lower than a set light output. In the high light output region that is configured to include and exceed the set light output, the output of the high-frequency superimposing circuit is applied to the semiconductor laser element, and the semiconductor laser element within the exposure range for the one pixel is included. 2. The image exposure apparatus according to claim 1, wherein the output amplitude of the high-frequency superposition circuit is set so that the peak intensity of the emitted light reaches the laser oscillation region.

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