JP2005001244A - Image exposing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve quality of an image which is formed by exposure by simplifying a structure of a circuit as much as possible in an image exposing device. <P>SOLUTION: This image exposing device comprises a semiconductor laser device 40 for emitting a laser light for exposing to form an image on a photosensitive material and a driving circuit 42 for driving the semiconductor laser device 40. The driving circuit 42 modulates the intensity of the quantity of the light to be emitted of the semiconductor laser device 40 according to an image signal of an image to be formed by exposure and superposes a high frequency signal of a setting frequency having a varied amplitude to the driving current of the semiconductor laser device 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image exposure apparatus provided with a semiconductor laser element that emits a laser beam for exposing and forming an image on a photographic photosensitive material, and a drive circuit that drives the semiconductor laser element.
[0002]
[Prior art]
Such an image exposure apparatus is an apparatus for exposing and forming an image on a photographic photosensitive material using a laser beam emitted from a semiconductor laser element as a light source.
The image formed on the photographic photosensitive material expresses the gradation of the image by changing the exposure amount by the laser beam. The method for changing the exposure amount is described in Patent Document 1 below. As described above, the pulse width modulation is based on the image data of the image to be exposed and the intensity of the emitted light from the semiconductor laser element is modulated based on the image signal of the image to be exposed as described in Patent Document 2 below. There is a form to do.
The present invention particularly relates to a type in which the drive current of the latter semiconductor laser element is directly modulated to modulate the intensity of the emitted laser beam.
[0003]
A semiconductor laser element is well known for its so-called mode hop in which the oscillation wavelength of emitted laser light shifts between oscillation longitudinal modes when its optical output is continuously changed.
Mode hop noise is generated by this mode hop, and the density gradation of the image is not properly expressed, and when a color image is formed by exposure, the color of the image formed by exposure may slightly fluctuate. In other words, the quality of the image formed by exposure is lowered.
[0004]
In order to avoid such inconvenience, a technique for superposing a high-frequency signal on the drive current of the semiconductor laser element has been considered as described in Patent Document 2 below. A technique is described in which a high-frequency signal applied to a driving current of a semiconductor laser element is not a single-frequency high-frequency signal, but noise is superimposed.
[0005]
[Patent Document 1]
JP-A-6-106774
[Patent Document 2]
JP-A-9-246640
[0006]
[Problems to be solved by the invention]
However, the conventional configuration has a disadvantage that the circuit configuration becomes complicated, for example, a circuit for removing a frequency band component affecting the image signal from the noise signal generated from the noise generator is required.
The present invention has been made in view of such circumstances, and an object thereof is to improve the quality of an image formed by exposure while simplifying the circuit configuration as much as possible.
[0007]
[Means for Solving the Problems]
An image exposure apparatus provided with a semiconductor laser element that emits a laser beam for exposing and forming an image on a photographic photosensitive material, and a drive circuit that drives the semiconductor laser element by providing the configuration according to claim 1 The drive circuit modulates the intensity of the emitted light quantity of the semiconductor laser element in accordance with the image signal of the image to be exposed and superimposes a high frequency signal having a set frequency whose amplitude varies on the drive current of the semiconductor laser element. Is configured to do.
[0008]
That is, by modulating the amplitude of the high-frequency signal of the set frequency with a desired input signal and superimposing it on the drive current of the semiconductor laser element, a signal close to noise is superimposed on the drive current of the semiconductor laser element. It is possible to easily suppress the frequency component included in the high-frequency signal from interfering with the frequency band of the image signal.
Accordingly, the complexity of the circuit due to the addition of a filter circuit or the like is suppressed as much as possible, and the quality of the image formed by exposure can be improved while simplifying the circuit configuration as much as possible.
Moreover, the technology itself that superimposes the high-frequency signal of the set frequency has been established as a technology used for so-called optical pickups that read the signal of the optical disk, and by using this technology, the reliability of the drive circuit of the semiconductor laser element can be improved. Can be higher.
[0009]
In addition, by providing the configuration according to claim 2, in the drive circuit, the signal level of the image signal becomes a level at which the peak wavelength in the oscillation wavelength of the semiconductor laser element shifts to another longitudinal mode wavelength. Sometimes, the degree of fluctuation of the amplitude of the high-frequency signal is increased.
That is, the degree of fluctuation of the amplitude of the high-frequency signal at the set frequency, in other words, the magnitude of the signal component acting as the noise can be kept constant regardless of the signal level of the image signal. When the signal level of the image signal becomes a level at which the peak wavelength at the oscillation wavelength of the semiconductor laser element shifts to another longitudinal mode wavelength, in other words, a level at which a so-called mode hop occurs, the amplitude of the high frequency signal By increasing the degree of fluctuation (the magnitude of the signal component that acts as noise), it is possible to more reliably prevent the deterioration of the image quality of the exposure image due to the mode hop of the semiconductor laser element.
Therefore, it is possible to accurately give a signal component that acts as noise at a required signal level, and avoid the possibility that the signal component that acts as noise deteriorates the image quality in other portions.
[0010]
In addition, by providing the configuration according to the third aspect, the drive circuit includes a high-frequency superposition integrated circuit that outputs a high-frequency signal having an amplitude corresponding to a signal input to the amplitude setting terminal. .
That is, a circuit that superimposes a high-frequency signal having a set frequency on the drive current of the semiconductor laser element has been put to practical use as an optical pickup IC, and such an IC sets an amplitude for setting the amplitude of the output high-frequency signal. It is often equipped with terminals.
Therefore, the cost of the entire image exposure apparatus can be reduced by using such an optical pickup IC supplied at low cost as it is and generating a high-frequency signal including a signal component that acts as noise. Can do.
[0011]
Further, by providing the configuration according to claim 4, the drive circuit is configured to apply a sine wave to the amplitude setting terminal of the high-frequency superposition integrated circuit, and by changing the amplitude of the sine wave. The amplitude of the high-frequency signal is varied.
Therefore, by simply inputting a sine wave as the signal component acting as the noise to the amplitude setting terminal of the high frequency superposition integrated circuit, it is possible to further reduce the cost while suppressing the deterioration of the image quality of the exposure image. Can do.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
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 photographic print system DP exemplified in the first embodiment is known as a so-called digital minilab machine, and as shown in FIG. 4, developed photographic film, memory card, MO or CD- An image input device IR for inputting image data for producing a photographic print from R and the like, and an exposure / development device EP for exposing the image data input by the image input device IR to photographic paper 2 as a photographic photosensitive material PS It consists of and.
[0013]
[Schematic configuration of image input device IR]
As schematically shown in FIG. 3, the image input device IR includes a film scanner 3 for reading a frame image of a photographic film, an external input / output device 4 including a memory reader, an MO drive, a CD-R drive, and the like. The main control device 5 is configured by a general-purpose small computer system and controls the film scanner 3 and the external input / output device 4 and performs management of the entire photo print system DP. A monitor 5a for displaying a simulated image simulating a finished print image and various control information is connected to a console 5b for manually setting exposure conditions and inputting control information.
[0014]
[Overall configuration of exposure / development apparatus EP]
The exposure / development apparatus EP includes an image exposure apparatus EX, a development processing apparatus PP for developing the photographic paper 2 exposed by the image exposure apparatus EX, and a photographic paper magazine 6 disposed in the casing. There is provided a photographic paper transport system PT for transporting the photographic paper 2 drawn out from the paper to the developing device PP by a number of transport rollers 9 and the like.
As shown in FIG. 4, a sorter 7 for classifying the photographic paper 2 developed and dried by the development processing device PP for each order and a development processing device are provided outside the housing of the exposure / development device EP. A conveyor 10 for conveying the photographic paper 2 discharged from the PP discharge port 8 to the sorter 7 is provided.
Further, in the middle of the conveyance path of the photographic paper conveyance system PT, a cutter 11 that cuts the long photographic paper 2 drawn out from the photographic paper magazine 6 into a set print size, and the photographic paper 2 is distributed to a plurality of conveyance rows. For this purpose, a sorting device 12 is provided.
[0015]
[Configuration of image exposure apparatus EX]
The image exposure apparatus EX includes an image exposure unit 13 that forms an exposure image on the photographic paper 2 by scanning the photographic paper 2 with a laser beam, and an exposure control device 14 that controls the image exposure unit 13. It is configured as.
[0016]
[Configuration of Image Exposure Unit 13]
The image exposure unit 13 employs a so-called laser exposure method in which an image is exposed on the photographic paper 2 using a laser as a light source, and the schematic configuration is shown in the block configuration diagram of FIG.
In the image exposure unit 13, the red laser light source 20r, the green laser light source 20g, and the blue laser light source 20b that respectively emit red, green, and blue laser light, and the intensity of the emitted light from the green laser light source 20g and the blue laser light source 20b are modulated. An acoustooptic modulator 21 (hereinafter abbreviated as “AOM element 21”), and a beam expander 22 for adjusting the beam diameter of the laser beam LB emitted from each of the laser light sources 20r, 20g, and 20b. A cylindrical lens 23, a prism 24 for combining the optical axes of the three laser beams LB of red, green and blue into one optical axis, a polygon mirror 25 for scanning the laser beam LB, and an f-θ characteristic. And an imaging lens group 26 having a surface tilt correction function, and a mirror for bending the optical path of the laser beam LB Aperture 28 for restricting the light incident to 7 or a prism 24 are arranged.
[0017]
[Configuration of Red Laser Light Source 20r]
Of the laser beams LB of the respective colors, the green and blue laser beams LB have a form in which the laser beam LB emitted from the green laser light source 20g or the blue laser light source 20b is externally modulated by the AOM element 21. The AOM element 21 is not provided for the laser light source 20r, and the emitted light itself of the red laser light source 20r is directly modulated.
The configuration of the red laser light source 20r will be further described. As shown in FIG. 1, the red laser light source 20r includes a semiconductor laser element 40 that emits red laser light for exposing and forming an image on the photographic paper 2. A lens 41 and a drive circuit 42 for supplying a drive current to the semiconductor laser element 40 are provided.
[0018]
[Configuration of Drive Circuit 42]
In the drive circuit 42, the semiconductor laser element 40 outputs a drive current corresponding to the red image signal input from the exposure control device 14 to the semiconductor laser element 40, and directly modulates the amount of light emitted from the semiconductor laser element 40. A current output circuit 51 and a high frequency superposition integrated circuit 52 for superposing a high frequency signal of a set frequency on the drive current of the semiconductor laser element 40 are provided. That is, by directly modulating the semiconductor laser element 40, the emitted light itself of the red laser light source 20r is intensity-modulated according to the image signal.
[0019]
The current output circuit 51 incorporates a circuit that adds a current corresponding to the oscillation threshold current of the semiconductor laser element 40 to a current proportional to the input image signal.
The high-frequency superposition integrated circuit 52 uses an optical pickup high-frequency superposition integrated circuit provided with an amplitude setting terminal 52a and a frequency setting terminal 52b as it is, and the resistance value or application of a resistor connected to the amplitude setting terminal 52a. The amplitude of the high frequency signal output from the output terminal 52c is set by the voltage to be applied, and the frequency of the high frequency signal output from the output terminal 52c is set by the resistance value of the resistor connected to the frequency setting terminal 52b or the applied voltage. The
[0020]
In the first embodiment, an oscillation circuit 53 that outputs a sine wave is connected to the amplitude setting terminal 52 a of the high-frequency superposition integrated circuit 52 via a resistor 54, and a high-frequency signal output from the high-frequency superposition integrated circuit 52. The amplitude of fluctuates sinusoidally. The oscillation frequency and amplitude of the oscillation circuit 53 are determined experimentally so that a good quality image can be obtained by producing a test print.
The frequency setting terminal 52 b of the high frequency superposition integrated circuit 52 is connected to the ground via a resistor 55. The oscillation frequency of the high-frequency superposition integrated circuit 52 determined by the resistor 55 is set to a frequency (about several hundred MHz) sufficiently higher than the frequency of the image signal input from the exposure control device 14.
[0021]
[Configuration of Exposure Control Device 14]
As schematically shown in FIG. 2, the exposure control device 14 takes the image data input from the image input device IR into consideration for the exposure characteristics of the image exposure unit 13 in order to control the image exposure unit 13 having the above configuration. An image processing circuit 30 that corrects and calculates the image data, an image data memory 31 that stores the image data obtained by the image processing circuit 30 for each color of red, green, and blue, and each color of red, green, and blue A D / A converter 32 for D / A converting the output data of the image data memory 31 and a control signal having an amplitude corresponding to an input signal from the D / A converter 32 for green and blue are AOM elements. 21 and an AOM control circuit 33 that outputs to 21 and a timing control circuit 34 that controls the transmission timing of the image signal sent from each D / A converter 32. To have. As described above, the red laser light source 20r has a form in which the semiconductor laser element 40 is directly modulated. Therefore, the output of the D / A converter 32 that outputs an image signal in the range of 0 to 1V is the output of the red laser light source 20r. It is sent to the current output circuit 51.
[0022]
[Exposure operation of image exposure apparatus EX]
Next, operations of the image exposure unit 13 and the exposure control device 14 having the above-described configuration will be described.
The exposure image data input from the image input device IR is corrected and calculated by the image processing circuit 30 and converted into image data that provides a good print image when exposed by the image exposure unit 13, and the image data memory 31 are sequentially written.
Data once stored in the image data memory 31 is sent to the D / A converter 32 in units of pixels in synchronization with the clock signal input from the timing control circuit 34 for each pixel data.
The output of the D / A converter 32 for the red image signal is sent to the drive circuit 42 of the red laser light source 20r of the image exposure unit 13, and the output of the D / A converter 32 for the green and blue image signals is AOM. It is sent to the control circuit 33.
[0023]
The AOM control circuit 33 outputs a control signal having an amplitude corresponding to the input signal to the AOM element 21, and the AOM element 21 is incident from the green laser light source 20g and the blue laser light source 20b with a diffraction rate corresponding to the amplitude of the input control signal. Modulate the laser beam.
On the other hand, the current output circuit 51 of the drive circuit 42 that has received the image signal from the red D / A converter 32 outputs the drive current of the semiconductor laser element 40 in accordance with the input image signal. A high-frequency signal output from the high-frequency superposition integrated circuit 52 is superimposed on the drive current of the semiconductor laser element 40. The amplitude of the high-frequency signal output from the high-frequency superposition integrated circuit 52 varies as described above.
Each laser beam LB modulated as described above enters the prism 24 after passing through the beam expander 22 and the like, and the three light beams LB of red, green and blue are combined into one laser beam LB. Then, the reflection surface of the polygon mirror 25 is irradiated.
[0024]
The laser beam LB reflected by the reflection surface of the polygon mirror 25 that is rotationally driven by the drive motor 25a is scanned in a plane orthogonal to the rotation axis of the polygon mirror 25, and is conveyed and moved onto the photographic paper 2. The light is condensed by the imaging lens group 26. The scanning direction of the laser beam LB intersects (more specifically, orthogonal) with the conveyance direction of the photographic paper 2, the scanning direction of the laser beam LB is the main scanning direction, and the conveyance direction of the photographic paper 2 is the sub-scanning direction. Become. An image to be printed on the photographic paper 2 is formed as a latent image by scanning the laser beam LB and transporting the photographic paper 2.
[0025]
[Photo print production operation]
Next, a photographic print production operation by the photographic print system DP having the above configuration will be schematically described.
When the operator inputs an instruction to make a photographic print for a photographic film frame image, the main controller 5 instructs the film scanner 3 to read the photographic film, and the image data of the photographic film is sent from the film scanner 3. Are sequentially received and recorded in a built-in memory.
On the other hand, when the operator inputs an instruction to create a photographic print for image data recorded on a recording medium such as a memory card, MO, or CD-R, the main controller 5 selects the corresponding drive of the external input / output device 4. The image data is instructed to be read, and the image data is sequentially received from the drive and recorded in the memory.
[0026]
Based on the image data input as described above, the main control unit 5 calculates a simulated image that would be obtained when a print was produced using the image data by an image processing circuit (not shown). And display it on the monitor 5a.
The operator observes the simulated image on the monitor 5a, and if an appropriate image is not obtained, the operator performs an exposure condition correction input operation from the console 5b.
The image processing circuit of the main controller 5 generates exposure image data for each of red, green, and blue under predetermined calculation conditions in accordance with the input image data and its correction input.
[0027]
The exposure image data is sent to the exposure control device 14 of the exposure / development apparatus EP, and when it is detected that the front end of the photographic paper 2 has been conveyed to a predetermined exposure start position, the image exposure is performed as described above. The unit 13 forms a latent image of the print image on the photographic paper 2.
The photographic paper 2 subjected to the exposure processing by the image exposure unit 13 is transported to the development processing device PP by the photographic paper transport system PT, and is developed by sequentially passing through the development processing tanks. 2 is further dried and then discharged from the discharge port 8 onto the conveyor 10 and collected by the sorter 7 for each order.
[0028]
Second Embodiment
Next, a second embodiment of the present invention will be described.
The second embodiment is different from the first embodiment only in the internal configuration of the drive circuit 42 provided in the red laser light source 20r, and the other parts are common to the first embodiment.
[Configuration of Drive Circuit 42]
As shown in FIG. 5, the semiconductor laser element 40 outputs the drive current of the semiconductor laser element 40 corresponding to the red image signal input from the exposure control device 14 to the drive circuit 42 of the second embodiment. In addition, a current output circuit 51 that directly modulates the semiconductor laser element 40 and a high frequency superposition integrated circuit 52 for superimposing a high frequency signal having a set frequency on the drive current of the semiconductor laser element 40 are provided. The configuration is the same as that of the first embodiment.
[0029]
In the second embodiment, the frequency setting terminal 52b of the high frequency superposition integrated circuit 52 is connected to the ground via the resistor 55, and the oscillation frequency of the high frequency superposition integrated circuit 52 determined by the resistor 55 is the exposure control device. The frequency setting terminal of the high frequency superposition integrated circuit 52 is similar to the first embodiment in that it is set to a frequency sufficiently higher than the frequency of the image signal input from 14 (about several hundred MHz). The input signal for 52a is different from that of the first embodiment.
[0030]
That is, an oscillation circuit 53 that outputs a sine wave is connected to the amplitude setting terminal 52 a of the high-frequency superposition integrated circuit 52 via the resistor 54 and the amplifier 61.
In this amplifier 61, the amplification gain can be set and changed in two stages, and a drive circuit 42 is provided with a gain control circuit 62 for switching and controlling the amplification gain.
The same image signal as the image signal input to the current output circuit 51 is input to the gain control circuit 62. Based on the input image signal, the gain control circuit 62 determines that the signal level of the image signal is a semiconductor laser. When the peak wavelength of the oscillation wavelength of the element 40 is at a level at which it shifts to another longitudinal mode wavelength (for convenience, this signal level is referred to as “mode hop signal level” below), the gain of the amplifier 61 is increased. And the degree of fluctuation of the amplitude of the high-frequency signal output from the high-frequency superposition integrated circuit 52 is increased.
[0031]
In order to perform such operations, the gain control circuit 62 includes a plurality of window comparators 62a and an OR circuit 62b.
The window comparator 62a is provided corresponding to each of the mode hop signal levels within the range of the image signal, and is provided with at least the number of the mode hop signal levels.
The detection window range of each window comparator 62a is set to a narrow range sandwiching the corresponding mode hop signal level, and the signal level of the input image signal is sufficiently close to any of the plurality of mode hop signal levels. When a detection signal is output from the window comparator 62a corresponding to the mode hop signal level, the gain of the amplifier 61 is set to a value on the high gain side while the detection signal is output.
[0032]
As a result, the amplitude of the sine wave input to the amplitude setting terminal 52a of the high-frequency superposition integrated circuit 52 becomes large, and the degree of fluctuation (sinusoidal fluctuation) of the high-frequency signal output from the high-frequency superposition integrated circuit 52 Will become big. The oscillation frequency of the oscillation circuit 53 and the gain of the amplifier 61 are experimentally determined so that a good quality image can be obtained by producing a test print.
The “exposure operation of the image exposure apparatus EX” for the photographic paper 2 and the “photo print production operation” for the photographic paper 2 by the configuration and operation of the drive circuit 42 as described above are the same as those in the first embodiment, and the description thereof is omitted. To do.
[0033]
<Other embodiments>
Hereinafter, other embodiments of the present invention will be listed.
(1) In the first and second embodiments, the amplitude of the high-frequency signal superimposed on the drive current of the semiconductor laser element is varied according to the sine wave signal output from the oscillation circuit 53. There are various specific configurations such as applying a pulse signal having a fixed period or indefinite period to the amplitude setting terminal 52a of the high frequency superposition integrated circuit 52, or applying a signal generated by amplifying noise generated in a circuit element. It can be changed.
[0034]
(2) In the first embodiment and the second embodiment, the photographic paper 2 is exemplified as the photographic photosensitive material PS. However, in addition to various photosensitive films, images on various photographic photosensitive materials PS such as a photosensitive drum. The present invention can be applied to the exposure formation.
(3) In the first and second embodiments, the case where the high-frequency superposition integrated circuit 52 for optical pickup is used to superimpose a high-frequency signal on the drive current of the semiconductor laser element 40 is exemplified. The circuit function of the high-frequency superposition integrated circuit 52 may be constituted by individual elements.
(4) In the first and second embodiments, the case where the present invention is applied to the red laser light source 20r is illustrated, but the present invention is applied to laser light sources of other exposure colors such as a blue laser light source 20b. May be applied.
[0035]
【The invention's effect】
According to the configuration of the first aspect, the amplitude of the high frequency signal of the set frequency is amplitude-modulated with a desired input signal and superimposed on the drive current of the semiconductor laser element, thereby superimposing a signal close to noise, It is possible to easily suppress the frequency component included in the high-frequency signal superimposed on the driving current of the semiconductor laser element from interfering with the frequency band of the image signal.
Accordingly, the complexity of the circuit due to the addition of a filter circuit or the like is suppressed as much as possible, and the quality of the image formed by exposure can be improved while simplifying the circuit configuration as much as possible.
[0036]
According to the second aspect of the present invention, the degree of fluctuation of the amplitude of the high-frequency signal at the set frequency, in other words, the magnitude of the signal component acting as the noise is made constant regardless of the signal level of the image signal. Although the signal level of the image signal is a level at which the peak wavelength in the oscillation wavelength of the semiconductor laser element shifts to another longitudinal mode wavelength, in other words, a level at which a so-called mode hop occurs. When this happens, the degree of fluctuation in the amplitude of the high-frequency signal (the magnitude of the signal component that acts as noise) is increased to more reliably prevent deterioration in the image quality of the exposed image due to the mode hop of the semiconductor laser element.
Therefore, it is possible to accurately give a signal component that acts as noise at a required signal level, and avoid the possibility that the signal component that acts as noise deteriorates the image quality in other portions.
[0037]
According to the configuration of the third aspect, the circuit for superimposing the high-frequency signal of the set frequency on the drive current of the semiconductor laser element has been put to practical use as an IC for an optical pickup, and such an IC outputs it. In many cases, an amplitude setting terminal for setting the amplitude of the high-frequency signal is provided.
Therefore, the cost of the entire image exposure apparatus can be reduced by using such an optical pickup IC supplied at low cost as it is and generating a high-frequency signal including a signal component that acts as noise. Can do.
[0038]
According to the fourth aspect of the present invention, image quality deterioration of the exposure image can be suppressed by simply inputting a sine wave to the amplitude setting terminal of the high-frequency superposition integrated circuit as the signal component acting as the noise. However, the cost can be further reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a drive circuit for a semiconductor laser device according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an image exposure apparatus according to an embodiment of the present invention.
FIG. 3 is a block diagram of a photo print system according to an embodiment of the present invention.
FIG. 4 is an external perspective view of a photographic print system according to an embodiment of the present invention.
FIG. 5 is a configuration diagram of a drive circuit for a semiconductor laser device according to a second embodiment of the present invention;
[Explanation of symbols]
PS Photosensitive material
40 Semiconductor laser device
42 Drive circuit
52 Integrated circuit for high frequency superposition
52a Amplitude setting terminal

Claims (4)

An image exposure apparatus comprising a semiconductor laser element that emits a laser beam for exposing and forming an image on a photographic photosensitive material, and a drive circuit that drives the semiconductor laser element,
The drive circuit modulates the intensity of light emitted from the semiconductor laser element according to an image signal of an image to be exposed and superimposes a high frequency signal having a set frequency whose amplitude varies on the drive current of the semiconductor laser element. An image exposure apparatus configured as described above. The drive circuit increases the degree of fluctuation in the amplitude of the high-frequency signal when the signal level of the image signal reaches a level at which the peak wavelength of the oscillation wavelength of the semiconductor laser element shifts to another longitudinal mode wavelength. The image exposure apparatus according to claim 1, wherein the image exposure apparatus is configured to do so. 3. The image exposure apparatus according to claim 1, wherein the drive circuit includes a high frequency superposition integrated circuit that outputs a high frequency signal having an amplitude corresponding to a signal input to an amplitude setting terminal. The drive circuit is configured to apply a sine wave to an amplitude setting terminal of the high-frequency superposition integrated circuit, and changes the amplitude of the high-frequency signal by changing the amplitude of the sine wave. 4. The image exposure apparatus according to claim 3, wherein the image exposure apparatus is configured as follows.

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