JPS63102547A - Laser recording device - Google Patents

Abstract

PURPOSE:To record a high gradation continuous image at a high speed and accurately by correcting the non-linearity of a light emitting level command signal pair scanning beam strength characteristic due to the fact that the incident light strength pair light transmittance characteristic of an optical element is non-linear, with a correcting table provided separately from a semiconductor laser light output stabilizing circuit. CONSTITUTION:A light output stabilizing circuit (APC) circuit 8 is composed of an adding point 2, a voltage-current converting amplifier 3, a semiconductor laser 1, a photodiode 6 and a currentvoltage converting amplifier 7, and a strength (light output of semiconductor laser 1) Pf of an optical beam 4 is in proportion to a light emitting level command signal Vref. A correcting table 40 is composed of a gradation correcting table 12, a reverse log converting table 13 and a V-P characteristic correcting table 14 to correct linearly the light emitting level command signal pair light output characteristic of the semiconductor laser 1, and an image signal S1 inputted through a multiplexer 11 is inputted through a gradation correcting table 12 and a reverse log converting table 13 to a V-P characteristic correcting table 14, and corrected so that the relation of a voltage value Vin and a scanning beam strength Ps corresponding to a light emitting level command signal S1'' can be linear.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a laser recording device that records a continuous tone image by scanning a photosensitive material with a laser beam modulated based on an image signal. This article relates to a laser recording device that can record high-gradation images by modulating the light intensity of a laser beam in an analog manner.

(Prior Art) Conventionally, optical scanning recording apparatuses have been widely put into practical use, which deflect a light beam using an optical deflector, scan a photosensitive material, and record an image on the exposure +A beam.

A semiconductor laser has conventionally been used as one of the means for generating a light beam in such an optical scanning recording device. This semiconductor laser has many advantages, such as being smaller, cheaper, and consumes less power than gas lasers, and can be directly modulated by changing the drive current.

However, on the other hand, as shown in Figure 2, the optical output characteristics of this semiconductor laser with respect to the drive current vary drastically between the LED area (natural light emitting area) and the laser excavation area, so it is not suitable for continuous tone image recording. The problem is that it is difficult. In other words, if intensity and intensity modulation is performed using only the above-mentioned laser emission region where the drive current vs. optical output characteristic is linear, the dynamic range of the optical output will be only about two orders of magnitude. As is well known, it is impossible to obtain a high quality continuous tone image with such a dynamic range.

For example, JP-A-56-115077 and JP-A-56-1
As shown in No. 52372, etc., the optical output of the semiconductor laser is kept constant, and the semiconductor laser is continuously switched to zero.
Attempts have also been made to record a continuous tone image by turning off the scanning beam to make the scanning beam pulsed light, and controlling the number or width of the pulses for each pixel to change the amount of scanning light.

However, when performing pulse number modulation or pulse width modulation as described above, for example, when the pixel clock frequency is 1M
At H2, in order to ensure a resolution of 10 bits (approximately 3 digits) on the density scale, that is, the amount of scanning light, the pulse frequency must be set extremely high, at least 1 GH2. The semiconductor laser itself is 0 at this frequency.
Although it is possible to turn the pixel clock N-OFF, the pulse count circuit for pulse number control or pulse width control cannot operate in response to such a high frequency, and in the end the pixel clock frequency is lower than the above value. must also be significantly lowered. Therefore, the recording speed of the device has to be significantly reduced.

Roughly speaking, in the above method, the light heat ω of the semiconductor laser chip changes depending on the number or width of pulses output during the recording period of each pixel, and therefore the drive current of the semiconductor laser The output characteristics may change and the exposure per pulse may vary. If this happens, the gradation of the recorded image will shift, making it impossible to obtain a high-quality continuous tone image.

On the other hand, as shown in Japanese Patent Laid-Open No. 56-71374, for example, a method of recording high-gradation images by combining the above pulse number modulation or pulse width modulation with the light intensity modulation described above has also been proposed. ing. However, in this case as well, the problem arises that the amount of heat generated by the semiconductor laser chip changes depending on the number or width of pulses as described above, and as a result, the amount of exposure per pulse changes.

Considering the above, for example, the concentration scale 1Qbit
In other words, to record a high gradation image of about 1024 gradations,
It is desirable to perform optical intensity modulation across the LED region and the laser emitting region shown in FIG. 2 described above to ensure a dynamic range of optical output of about three orders of magnitude. However, in the above two regions, the driving current vs. front output characteristic of the semiconductor laser is naturally not linear, so in order to easily and accurately record high-gradation images, it is necessary to change the image signal at equal density intervals in response to a constant amount of change in the image signal. In order to be able to control the image density and power, it is necessary to compensate for the above characteristics in some way to linearly change the relationship between the light emission level command signal of the semiconductor laser and the optical output.

Conventionally, as a circuit that linearizes the relationship between the light emission level command signal of the semiconductor laser and the optical output, it detects the light intensity of the laser beam and sends a feedback signal corresponding to the detected light intensity to the semiconductor laser light emission level command. An optical output stabilization circuit (hereinafter referred to as an APC circuit) that feeds back a signal is known. FIG. 3 shows an example of this APC circuit, and the APC circuit will be explained below with reference to FIG. The light emission level command signal y rer, which commands the light emission intensity of the semiconductor laser 1, is input to the voltage-current conversion amplifier 3 through the addition point 2, and the amplifier 3 supplies a drive current proportional to this command signal vref to the semiconductor laser 1.
supply to. A light beam 4 emitted forward from the semiconductor laser 1 is used to scan a photosensitive material through a scanning optical system (not shown).

On the other hand, the intensity of the light beam 5 emitted to the rear side of the semiconductor laser 1 is detected by, for example, a bin photodiode 6 for monitoring the amount of light installed inside the case of the semiconductor laser. The intensity of the light beam 5 thus detected is proportional to the intensity of the light beam 4 actually used for image recording. The intensity of the light beam 5, that is, the output current of the photodiode 6 indicating the intensity of the light beam 4 is converted into a feedback signal @ (voltage signal) Vc+dl by a current-voltage conversion amplifier 7.
: converted, and the feedback signal p0 is input to the above-mentioned point 2. From this addition point 2, a difference signal Ve (q) indicating the deviation between the light emission level command signal yrer and the feedback signal Vpd is output, and the deviation signal ve is converted into a current by the voltage-current conversion amplifier 3, and the semiconductor Drive laser 1.

In the above APC circuit, if ideal linear compensation is performed, the intensity of the light beam 5 will be equal to the light emission level command signal V re
It is proportional to f. In other words, the light beam 4 used for image recording
The intensity (light output of the semiconductor laser 1) Pf corresponds to the light emission level command signal Vref.

(Problem to be solved by the invention) However, even if the relationship between the light emission level command signal y ref and the semiconductor laser light output can be linearly corrected using the APC circuit as described above, it is difficult to correct the relationship between the light emission level command signal y ref and the semiconductor laser light output by using the APC circuit as described above. Depending on the characteristics of the optical element, the relationship between the light emission level command signal y ref and the intensity of the beam that actually scans the photosensitive material inevitably becomes nonlinear. This will be explained in detail below.

When using a semiconductor laser by modulating the intensity of the laser light from its LED region to the daytime region, a problem arises in that the convergence of the scanning beam is impaired.In other words, the spontaneous light emitted from the semiconductor laser is , compared to laser oscillation light, there are various angular components mixed, and for example, in the case of a longitudinal multi-mode semiconductor laser, the spectral component of laser light is in the range of about 2 nm, whereas it is about 4Q.
Since the laser oscillation light has a spectral component extending over nm, it is difficult to focus the laser oscillation light into a small spot diameter when it is focused by a focusing lens. For this reason, when using light in the high-power region where laser oscillation light is dominant, as well as light in the low-power region that is naturally emitted or is dominant (of course 100% in the LED region), the scanning spatial This will result in loss of resolution.

'In order to improve the convergence of this scanning beam, for example, a polarizing filter as shown in Japanese Patent Application No. 61-075077 filed by the present applicant or an interference filter as shown in Japanese Patent Application No. 6]-150227 is used. , and even 61-1
It is conceivable to use an aperture limiting plate or the like as shown in Japanese Patent No. 96352.

In other words, among the light emitted from the semiconductor laser, the laser oscillation light is linearly polarized in a direction parallel to the bonding surface of the laser diode chip, whereas the spontaneously emitted light is randomly polarized, so the laser oscillation light is When the emitted light beam is passed through a polarizing filter that transmits only the light polarized in the direction parallel to the junction surface of the laser diode chip, almost all of the laser oscillation light is transmitted, whereas the naturally emitted light is approximately 1 Only about /2 is transmitted. I wanted to,
Near the threshold of semiconductor laser, that is, laser emission and LE
If the light beam emitted from the semiconductor laser is passed through the above polarizing filter in a region that includes both properties of D, the ratio of laser emitted waste in the scanning beam will be much higher, so the focusing property of the scanning beam will be improved. .

In addition, if the light beam emitted from the semiconductor laser is passed through an interference filter that transmits only light with a wavelength near the wavelength range of the laser beam, it is possible to pass the scanning beam to the laser beam without cutting the laser beam. It can be made to consist of extremely narrow spectral components similar to the emitted light.In that case, even if the lenses such as the focusing lens arranged in the beam-type distortion system are not particularly highly corrected for chromatic aberration, Improves the focusing of the scanning beam.

Furthermore, if an aperture limiting plate with a small aperture that allows only a part of the light beam to pass through is placed between the semiconductor laser and the collimator lens, or between the collimator lens and the focusing lens, the focusing ability of the scanning beam can be improved. I know what to do.

According to the polarizing filter, interference filter, or aperture limiting plate as described above, it is possible to narrow down the scanning beam to a smaller spot and record an image with high sharpness.

However, the polarizing filter, interference filter, and aperture limiting plate described above have a problem 8 in that the light transmittance changes nonlinearly with respect to the intensity of incident light.

This will be explained using the case of a polarizing filter as an example with reference to FIG. In FIG. 4, a curve PO indicates the intensity of the light beam emitted from the semiconductor laser. When this light beam is passed through the polarizing filter, the intensity of the output beam changes as shown by curve P in the figure. That is, in the LED area, only natural light is emitted, and as mentioned above, about 1. /2 is transmitted through the polarizing filter (that is, the light transmittance is approximately 50%).On the other hand, in the laser oscillation region, approximately 1/2 of the naturally emitted light is transmitted through the polarizing filter as described above, or Laser light, which occupies a much larger proportion of the emitted light in this region than naturally emitted light, passes through a polarizing filter. The polarizing filter transmittance of is significantly higher than the above-mentioned 50%.

Moreover, this light transmittance increases as the intensity of the light beam increases and the ratio of laser emitted waste rice to the intensity increases. The above-mentioned problem also occurs when a small interference filter is used.

On the other hand, as is well known, the divergence angle of a radiation beam emitted from a semiconductor laser varies as its optical output changes.

Therefore, when the aperture limiting plate described above is used as L9, the ratio of the amount of light blocked by this aperture limiting plate, in other words, the light transmittance, is the optical output of the semiconductor laser, that is, the amount of light blocked by the aperture limiting plate. ) varies depending on the intensity of the light being emitted. Figure 5 shows
When the light beam emitted from the semiconductor laser is passed through the aperture limiting plate as described above and the prism-type polarizing beam splitter used as a polarizing filter, the intensity of the light beam that has passed through these elements, and the intensity of the light beam that has passed through the semiconductor laser built-in An example of the relationship between the output current of the bin photodiode and the value converted into a voltage value is shown. Since the output current is proportional to the optical output of the semiconductor laser, that is, the intensity of the light beam before entering the element, the relationship between the intensity of the light beam and the light transmittance of the element is nonlinear.

Further, the incident beam emitted from the semiconductor laser is usually passed through a collimator lens to become a parallel beam, or in this case, depending on the lens diameter, if the incident beam spread angle becomes large, the beam may deviate from the collimator lens. The amount of light that leaves this lens (that is, the amount of light that enters the lens) changes as the semiconductor laser light output changes and the spread beam angle changes, so in this case as well, the light transmittance of the collimator lens varies depending on the intensity of light ti'j entering the lens. Figure 6 shows an example of the relationship between the light output detected by the bin photodiode with a built-in semiconductor laser and the light intensity of the collimator lens output j, and as shown in the figure, the relationship between the two is nonlinear. ing.

As mentioned above, if the incident light intensity lamp light transmittance characteristic of an optical element such as a polarizing filter is nonlinear, even if the relationship between the light emission level command signal and the semiconductor laser light output is linear as described above. In practice, the relationship between the intensity of the light beam scanning the photosensitive material and the light emission level command signal is not linear, making it impossible to easily and accurately record a high-gradation image.

Therefore, even if optical elements such as the above-mentioned polarizing filter, interference filter, aperture 11J limiting plate, or collimator lens are arranged in the beam scanning system, the difference between the emission level command signal of the semiconductor laser and the strong holding of the scanning beam. The purpose of this is to provide a laser recording device that can linearly extend from the LED area to the laser oscillation area, and thus can record high-gradation images at high speed by light intensity modulation. .

(Means for Solving the Problems) T. The laser recording device of the invention includes a semiconductor laser and an optical element having a non-linear relationship between incident light intensity and light transmission black, such as the polarizing filter, and the semiconductor laser a beam scanning system that scans a light beam emitted from the photosensitive material onto the photosensitive material;
A laser alignment device comprising: a laser operation control circuit that generates a light emission level command signal corresponding to an image signal, controls the drive current of the semiconductor laser based on the signal, and modulates the light intensity of the laser beam; The laser operation control circuit includes the APC circuit described above, and corrects the light emission level command signal so as to compensate for the nonlinearity of the incident light intensity lamp light transmittance characteristic of the optical element, and based on the corrected signal. The present invention is characterized by comprising a correction table that linearizes the relationship between the intensity of the scanning beam and the light emission level command signal before correction.

(Function) If the APC circuit as described above is provided, the nonlinearity of the light emission level command signal versus the scanning beam intensity due to the nonlinearity of the drive current versus optical output characteristic of the semiconductor laser will be reduced by the APC circuit.
Can be compensated by circuit. In addition, the polarizing filter mentioned above,
Even if the incident light intensity lamp light transmittance characteristics of optical elements such as interference filters, aperture limiting plates, and collimator lenses are nonlinear,
Since this is compensated for by the above correction table, it becomes possible to control the image density at equal density intervals in response to a fixed amount of change in the light emission level command signal.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows a laser recording apparatus according to an embodiment of the present invention. Image signal generator 10 generates an image signal @S1 carrying a continuous tone image. This image signal S1 is, for example, a digital signal representing a continuous tone image with a density scale of 1Qbit. The image signal generator 10 switches signals for one main scanning line based on a line clock S2, which will be described later, and outputs an image signal S1 for each pixel based on a pixel clock S3. In this example, the pixel clock frequency is 1MH7, in other words, the recording time for one pixel is 1 μsec.
(seconds).

The above image signal @S1 passes through the multiplexer 11 and is sent to the RA
After being subjected to a correction described later in a correction table 40 consisting of M, the signal is converted into, for example, a 15-bit light emission level command signal S5. This light emission level command signal S5 is input to the D/A converter 16, where it is converted into a light emission level command signal ref consisting of an analog voltage signal. This light emission level command signal Vref is transmitted to a signal changeover switch 1 which will be described later.
5 to the addition point 2 of the APC circuit 8. △P
The q addition point 2, voltage 1 voltage-current conversion amplifier 3, semiconductor laser 1, photodiode 6, and current-voltage conversion amplifier 7 of the C circuit 8 are the same as those in the circuit shown in FIG. 3 described above. Therefore, the semiconductor laser 1 outputs an image signal S1 corresponding to the light emission level command signal @Vref.
A light beam 4 is emitted with an intensity corresponding to . This light beam 4 is passed through a collimator lens 17 to be made into a parallel beam, and is formed by an aperture limiting plate 50 and a polarizing filter 5 as described above.
1 to form a light beam 4'. This light beam 4'
The light passes through a half mirror 52, and then enters an optical deflector 18, such as a polygon mirror, where it is reflected and deflected.

The light beam 4' thus deflected is passed through a focusing lens 19, which is usually an fθ lens, focused on a minute spot on the photosensitive material 20, and scans the photosensitive material 20 in the X direction (main scan). The photosensitive material 20 is transported by a transport mechanism (not shown) in the Y direction substantially perpendicular to the main scanning direction X, thereby causing the light beam 4' to perform sub-scanning.

In this way, the photosensitive material 20 is two-dimensionally scanned by the 4° light beam and exposed. As mentioned above, the light beam 4 (7
Since the light beam 4') is intensity-modulated by the image signal 8.1, it is recorded on the photosensitive material 20 as a continuous tone image or a photographic latent image carried by the image signal S1. . Note that when the light beam 4' scans the photosensitive material 20 as described above, the photodetector detects that the light beam 4' has passed through the starting point of the main scan. 1 and the photodetector 2
The start point detection signal S6 outputted by the clock generator 1 is input to the clock generator 36. The clock generator 36 outputs the aforementioned line clock S2 and pixel clock S in synchronization with the input timing of this start point detection signal S6.

The photosensitive material 20 is then passed through a developer 22 where it is processed. As a result, the continuous tone image is recorded on the photosensitive material 20 as a visible image.

Note that the polarizing filter 51 allows only light polarized in a direction parallel to the bonding surface of the laser diode chip of the semiconductor laser 1 to pass therethrough. By passing the light beam 4 through the polarizing filter 51 and the aperture limiting plate 50, the light beam (scanning beam) 4' that has passed through these can be focused on an extremely small spot as described above. The light-sensitive material 20 is scanned by the scanning beam 4' thus focused.
By scanning, it becomes possible to record images with high sharpness.

Here, the image signal S1 in the above-mentioned correction table 40 is
The correction will be explained below. The correction table 40 includes a gradation correction table 12, an inverse log conversion table 13, and a correction table (hereinafter referred to as ■-P characteristic correction table) 14 for linearly correcting the emission level command signal versus prior output characteristic of the semiconductor laser 1. Consisting of

The gradation correction table 12 is a known one for correcting the gradation characteristics of the photosensitive material 20 and its development processing system. This gradation correction table 12 may have fixed correction characteristics, but in non-embodiments,
The gradation characteristics may change from lot to lot, or the current
Current t in 2! ! Taking into account that the I liquid characteristics change over time, the correction characteristics can be modified as appropriate in accordance with the actual gradation characteristics.

That is, the test pattern generation circuit 26 outputs a test pattern signal S4 carrying several levels (for example, 16 levels) of image density on the photosensitive material 20.
S4 is input to multiplexer 11. At this time, the multiplexer 11 is switched from the image recording state in which the image signal S1 is input to the correction table 40 as described above, and the test pattern signal 84 is input to the correction table 40.
The state is said to require manual labor. The semiconductor laser 1 is driven as described above based on this test pattern signal S4,
The light beam 4' is therefore intensity modulated. As a result, the density changes stepwise on the photosensitive material 20, for example, 1
61 step wedge (test pattern) or recorded as a photographic latent image. This photosensitive material 20 is sent to a developing machine 22, and the step wedge is developed. After development, the photosensitive material 20 is set in a densitometer 23, and the optical 7 degrees of each of the step wedges is measured. The optical density thus measured is input to the IA value input means 24 in association with each step wedge, and the density value input means 24 outputs a density signal S7 indicating the optical density of each step wedge. This density signal S7 is input to the table creation means 37, and the table creation means 37 uses the density signal S7 and the test pattern signal S4 to determine the level at which a predetermined image density can be obtained with the value of the predetermined image signal 81. Create a key correction table. As described above, this gradation correction table is made up of approximately 16 levels of image signal values, each of which corresponds to a predetermined image density value. Data S8 indicating this gradation correction table is input to the data interpolation means 38, where it is interpolated and processed in 1024 steps (
1q of gradation correction tables that can correspond to the image signal @S1 (=19 bits) are created. The aforementioned gradation correction table 12 is formed based on the data 89 indicating this gradation correction table.

When recording an image based on the image signal S1, the image signal @S1 input to the tone correction table 12 via the multiplexer 11 is converted into the signal S1 by the tone correction table 12.
The signal is then converted into a light emission level command signal 81 by the inverse log conversion table 13.

Next, cA will explain the V-P characteristic correction table 14.
Even if it is possible to linearly correct the relationship between the light emission level command signal and the intensity of the light beam 4 by feeding back the feedback signal @vpd to the addition point 2 in the PC circuit 8, the aperture limiting plate 5
0, the incident light intensity of the polarizing filter 51, and in some cases the collimator lens 17, the light transmittance characteristics are non-linear as mentioned above, so the relationship between the light emission level command signal and the light intensity of the scanning beam 4' is linear. Not. Above V-
The P characteristic correction table 14 is provided to make the relationship between the scanning beam intensity and the light emission level command signal linear. That is, if the ideal relationship between the light emission level command signal Vref and the light intensity PS of the scanning beam 4' is a straight line shown as a in FIG. 7, and the actual relationship is a curve shown as b in FIG. -P characteristic correction table 14 assumes that Vin is the voltage value obtained when the light emission level command signal 81'' is D/Δ-converted as it is, then this voltage value Vin is
It is configured to convert to a value of That is, if the value of the light emission level command signal V ref is Vin, only the light intensity of P' can be obtained, but if the above conversion is performed, the light intensity of PO can be obtained for the voltage value Vin. That is, the relationship between the voltage value vin corresponding to the light emission level command signal 81° and the scanning beam intensity Ps is linear.

With this configuration, the density in the photosensitive material 20 can be controlled at equal intervals by changing the image signal S1 by a predetermined amount. Furthermore, the characteristic curve shown in FIG. 7 is obtained when the semiconductor laser 1 is driven across its LED area and laser emitting area as described above. Since the output dynamic range is secured, a high gradation image of about 1024 levels can be recorded easily and with high precision as described above.

Next, the creation of the VP characteristic correction table 14 will be explained. The apparatus shown in FIG. 1 is provided with a table creation means 70, and a test signal @31 issued from the table creation means 70 is provided.
0 or is input to the addition point 2 via the signal changeover switch 15. Further, a light beam 4'' reflected by a half mirror 52 that branches part of the light beam 4' is received by a photodetector 53 such as a photodiode.

A scanning beam intensity signal @VSI outputted by a current-voltage conversion amplifier 54 that converts the output of this photodetector 53 into a voltage signal
The information is input to the translation table creation means 70. When creating the correction table, the signal changeover switch 15 is switched from the state during image recording in which the light emission level command signal ref is sent to the addition point 2 as described above, to the state in which the test signal 310 is sent to the addition point 2. Ru.

The level of the test signal 310 increases in stages as time passes. That is, PROM7
2 stores equidistant number sequences on the logarithmic axis, and these number sequences are sequentially accessed by the clock CLK. Thereby, the digital value read from PROM 72 is converted into analog in D/A converter 73,
When amplified by the amplifier 74, a test signal @S10 is obtained in which the number of the clocks CLK, that is, the voltage value V increases stepwise as time passes, as shown in FIG. This test signal 310 is passed through the signal changeover switch 15.
It is input to addition point 2 as a substitute for the light emission level command signal Vref. Note that the FROM 72 has the above-mentioned concentration scale (that is, the emission level resolution of the semiconductor laser 1).
For example, a stored number sequence of 14 bits, which is sufficiently higher than the 10 bits of , is used.

When the test signal @S10 as described above is input to the addition point 2, the semiconductor laser 1 emits the light beam 4, and a signal ys indicating the intensity of the scanning beam 4' at that time is input to the comparator 77. This comparator 77 has CP
A reference signal V9 generated from the U 78 and converted into an analog signal by the D/A converter 76 is input, and the scanning beam intensity signal VS is compared with the reference signal Vg. At this time, CPIJ 7B first
The comparator 77 outputs a matching signal 81 when this reference signal @V(+(1) and the scanning beam intensity signal VS match).
Outputs 1. This minus number multiple 311 is input to the latch 75. The latch 75 receives the output from the PROM 72, and the latch 75 receives the output from the PROM 72.
72 output is latched. This latched signal 312
If explained with reference to Fig. 7, indicates the value of the reference signal W or the value of V when it occurs in the V group (hereinafter, the voltage value ■ corresponding to the reference signal Vo(n) is expressed as V(n>). ) eCPU7B is
A table for converting the reference signal Vg (1) into a signal of voltage value (1) is formed in the RAM 79.

The minus number multiple number 811 is also input to CPU 7B, and C
When p IJ 78 receives this coincidence signal 311, reference signal V! ] (1) is switched to VG (2>, that is, the one corresponding to the second emission level from the bottom of the semiconductor laser 1, and the comparator 77 is reset at the same time. In this case as well, the CPU 7B switches the reference signal V !]
A table for converting (2> into a signal of voltage value V(2)) is formed in the RAM 79.

The above operations are performed sequentially up to the reference signal @Vg (1024), that is, the il signal corresponding to the maximum emission level of the semiconductor laser 1, and as a result, 102
A table is created that converts each of the four signal values Vin(n> to V(n>). This table is transferred to the RAM constituting the correction table 40 via the data line
and is set as the V-P characteristic correction table 14. As mentioned above, this correction table 14G is formed to convert the voltage value Vin in FIG. The relationship is linear.

As explained above, in addition to finding the relationship between the voltage values V and V corresponding to all image densities, the voltage value V
The relationship between group and V is determined only in some major cases, and the data is interpolated to create the V-P characteristic correction table 14.
You may also create one. i again! l! i-key correction table 12, inverse log conversion table 13, and the above V
The -P characteristic correction table 14 may be formed as a single correction table including all of the respective conversion characteristics, or may be formed into separate forms.

Further, in the above embodiment, the test signal 310 whose level increases stepwise as time elapses is used, but in contrast, the test signal 310 whose level increases stepwise or continuously as time elapses. A falling test signal can also be used.

Further, in the embodiment described above, the aperture limiting plate 50 and the polarizing filter 51 are provided in order to improve the convergence of the scanning beam 4', but only one of these may be used. Alternatively, the above-mentioned interference filter may be used in place of these optical elements, or two or all of these three optical elements may be used in appropriate combination.

Alternatively, the table creation means 70 as described above may not be provided, and the V-P characteristic correction table 14 may be created using a sieve or the like. However, if a means for creating a correction table is provided as in the above embodiment, the correction table can be re-created at any time, so even if the performance of a semiconductor laser changes over time, for example, such changes can be avoided. The correction table can always be kept appropriate through compensation, and a state in which accurate recording can be performed can be maintained for a long period of time.

(Effects of the Invention) As explained in detail above, in the laser recording device of the present invention, the driving current versus optical output characteristic of the semiconductor laser is nonlinear, and the polarizing filter etc. provided to improve the focusing property of the scanning beam, etc. A semiconductor laser light output stabilization circuit and a separate circuit are provided to prevent the nonlinearity of the light emission level command signal versus scanning beam intensity characteristic caused by the nonlinearity of the incident light intensity lamp light transmittance characteristic of the optical element. Since the correction is made using the correction table, the relationship between the light emission level command signal and the scanning beam intensity can be made linear over the LED area and laser emission area.

Therefore, according to the apparatus of the present invention, the image density can be controlled at equal density intervals by changing the image signal by a predetermined amount, and the optical output dynamic range of the semiconductor laser, that is, the exposure amount of the photosensitive material can be controlled over a wide range of about 3 orders of magnitude. Since this can be ensured, it becomes possible to record extremely high-gradation continuous-tone images with a density resolution of about 10 bits, for example, at high speed and with precision.

In addition, in the laser recording apparatus of the present invention, there is no problem in controlling the image density 1111 as described above (because optical elements such as the q-optical filter, the interference filter, and the aperture limiting plate can be arranged in the beam constant strain system), The optical element focuses the scanning beam into a tiny spot, making it possible to record highly sharp images.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a laser recording device according to an embodiment of the present invention, Fig. 2 is a graph showing the driving current versus optical output characteristics of a semiconductor laser, and Fig. 3 is an example of a semiconductor laser optical output stabilizing circuit. FIG. 4 is a graph illustrating the action of the polarizing filter according to the present invention; FIG. 5 is a graph illustrating an example of incident light intensity versus output light intensity characteristics in a combination of a polarizing filter and an aperture limiting plate; The figure is a graph showing an example of the incident light intensity vs. output light intensity characteristic of the collimator lens, and FIG. 7 is a graph of V-P'? FIG. 8 is a graph illustrating the operation of the V-characteristic correction table. FIG. 8 is a graph showing the waveform of the test signal emitted by the table creation means of the apparatus of the above embodiment. 1... Semiconductor laser 2... Addition point 3...
Voltage-current conversion amplifier 4.4', 5... Light beam 6... Photodiode 7.54... Current-voltage conversion amplifier 8... APC circuit 10... Image signal generator 14... -P characteristic correction table 16.73.76...D/A converter 17-...Collimator lens 18...Light deflector 1
9... Focusing lens 20... Photosensitive material 40
... Correction table 50 ... Aperture restriction plate 51
...Polarizing filter 52...Half mirror 5
3... Photodetector 70... Table creation means 72... PROM 75... Latch 77... Comparator 78... CPU7
9...RA! Vl 31...Image signal 81''...Emission level command signal ref before correction...
Light emission level command signal VDd... Feedback signal Ve... Deviation signal V
S...Shiki beam intensity signal No. 5r? 1 Fike'Ioh μ゛Featured Island Katsushima Figure 7 Figure 8 Confrontation of Darkness 1 Shot〉Procedural Amendment 1. Indication of the case Japanese Patent Application No. 61-248877 2, Name of the invention Laser recording device 3, Person making the amendment Relationship to the case Patent applicant Location 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name Name
Fuji Photo Film Co., Ltd. 4, Agent Address: 5-2-1 Roppongi, Minato-ku, Tokyo 160 6. Number of inventions increased by amendment None 7. Subject of amendment Drawing 8. Contents of amendment Inking of hand-drawn drawing will be corrected.

Claims (1)

[Claims] (1) A semiconductor laser that emits a light beam, a beam scanning system that includes an optical element with a nonlinear relationship between incident light intensity and light transmittance and scans the light beam onto a photosensitive material, and a light emission level command that corresponds to an image signal. A laser recording device comprising: a laser operation control circuit that generates a signal and modulates the intensity of the light beam by controlling a driving current of the semiconductor laser based on the signal, the laser operation control circuit controlling the intensity of the light beam. a light output stabilization circuit that detects the intensity of the light and feeds back a feedback signal corresponding to the detected light intensity to the light emission level command signal; A laser recording device comprising: a correction table that corrects the light emission level command signal so as to linearize the relationship between the intensity of the scanning beam based on the corrected signal and the light emission level command signal before correction. Device.