JPH09244058A - Driving method for space light modulator and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the driving method of a space light modulator capable of quickly obtaining the secondary image having high quality and an image forming device using the space light modulator. SOLUTION: After an R filter is set in an optical path (150, 152), a pre- exposure is performed in order to improve optical responsiveness (153) and after the responsiveness is improved by the pre-exposure, a correction reflection image with respect to an R image is displayed on a write CRT and then an image is formed in space light modulation elements (154), the transmitted image of a print objective frame and the image formed in the space modulation elements are synthesized by releasing a shutter for a prescribed time to be printed on a color paper (156-162). These processings arc performed similarily with respect to a G filter and a B filter (164) and a print is formed by writing images in the space light modulation element and also by exposing written images with correcting lights.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a spatial light modulator and an image forming apparatus, and more particularly, to a method of driving a spatial light modulator that stores a secondary image based on an input image, and a spatial light modulator. The present invention relates to an image creating apparatus using.

[0002]

2. Description of the Related Art A digital secondary image is obtained from a negative image or a positive image (hereinafter referred to as an original image) recorded on a photographic film such as a negative film or a reversal film,
Image creating apparatuses such as a photographic printer that creates a print using this secondary image and a video projector that projects a secondary image are known.

In this image forming apparatus, it is necessary to correct the density and the color according to the image size based on the print size and the projection ratio and the tint of the original image.
In order to obtain the next image from the original image, a device capable of digitally converting the original image is required. As such a device, there is known a spatial light modulator having a memory function of using an original image such as a transmission image of a photographic film as an input image and storing the input image as a secondary image inside the element (Japanese Patent Laid-Open No. 6-58242). -88896, Japanese Patent Laid-Open No. 3-69924
Reference).

This spatial light modulator is mainly constituted by including a liquid crystal element, and by irradiating an original image,
The original image is stored as a secondary image in the spatial light modulator. The stored secondary image is read by the reading light.

[0005]

However, in the conventional image forming apparatus, since it takes time from the irradiation of the writing light to the spatial light modulator to the manifestation of the image, that is, the optical Since the response characteristic is slow (the response speed is slow), the time for activating the spatial light modulator is required in addition to the time for exposing and writing the actual original image. Therefore, if the original image is exposed in an unstable state before the spatial light modulator is activated, the image quality is deteriorated, so that the exposure time for irradiating the writing light cannot be shortened and the exposure time is lengthened. I needed it. Therefore, the spatial light modulator cannot obtain a secondary image in a short time. In particular, it takes a long time to store an image in a low modulation range, that is, a low gradation range.

As a method of increasing the response speed, it is conceivable to reduce the cell gap (thickness of the liquid crystal layer) of the liquid crystal element provided in the spatial light modulator. It becomes difficult to secure the sex. Therefore, the quality of the obtained secondary image is deteriorated. Also, it is possible to lower the viscosity of the liquid crystal element itself, but lowering the viscosity of the liquid crystal element has reached its limit,
We have to develop something new. Further, when a ferroelectric liquid crystal element or an antiferroelectric liquid crystal element having a high response speed is used, it becomes impossible to express a halftone of an image.

In consideration of the above facts, the present invention can provide a method of driving a spatial light modulator and an image forming apparatus using the spatial light modulator, which can quickly obtain a high quality secondary image. Is the purpose.

[0008]

In order to achieve the above object, a method of driving a spatial light modulator according to a first aspect of the present invention comprises:
Before writing the optical pattern into the spatial light modulator, the optical pattern is written by optically inputting the optical pattern from one side, and the written optical pattern is read by irradiating light from the other side. Then, a predetermined exposure amount of light is irradiated.

A second aspect of the present invention is the method of driving the spatial light modulator according to the first aspect, wherein the exposure amount of the light pattern is written before the light pattern is written in the spatial light modulator. It is characterized by uniformly irradiating light with a larger exposure amount.

According to a third aspect of the present invention, there is provided a method of driving the spatial light modulator according to the first aspect, wherein when the light pattern is an image having gradation, a light pattern having a predetermined gradation is formed. It is characterized in that the region is irradiated with light having an exposure amount larger than the exposure amount corresponding to the predetermined gradation.

An image forming apparatus according to a fourth aspect of the invention is
A spatial light modulator in which the light pattern is written by optically inputting a light pattern from one side, and the written light pattern is read out by irradiating light from the other side, and the spatial light modulator Optical pattern input means for inputting the optical pattern for writing, and irradiating the spatial light modulator with the transmitted light or the reflected light of the original image as the light, and the optical pattern read from the spatial light modulator. An irradiation unit for irradiating the photosensitive material and an exposure unit for exposing the spatial light modulator with a predetermined exposure amount before inputting the light pattern are provided.

In the spatial light modulator, the light pattern is written by optically inputting the light pattern from one side,
The light pattern written by the irradiation of light from the other is read. In such a spatial light modulator, when a light pattern is written, an image is gradually formed by optical input, that is, irradiation of the light pattern until the density and the reflection intensity correspond to the light amount of the light pattern. The time until this image is formed is responsive, and the time required for writing is determined according to the light amount of the light pattern to be irradiated.

According to the invention of claim 1, the spatial light modulator includes:
Before writing the light pattern, a predetermined amount of light is emitted. In this way, before writing the light pattern,
By irradiating the light with a predetermined exposure amount, the spatial light modulator is activated with a predetermined exposure amount before writing the image, regardless of the light amount of the light pattern irradiated for writing, and is faster. The light pattern can be written responsively, that is, in a short time.

As described in claim 2, if the light having the predetermined exposure amount is uniformly irradiated with the light having the exposure amount larger than the exposure amount of the light pattern, the spatial light modulator can be located at any part. Even if there is, it can be activated uniformly and the light pattern can be written evenly. When the light pattern is an image having gradation, as described in claim 3, a region of the light pattern having a predetermined gradation, for example, a spatial light modulator having a density or a reflection intensity with which the response is not good. By irradiating the region of (1) with an exposure amount larger than the exposure amount corresponding to the predetermined gradation, it is possible to promptly activate the necessary portion that does not have good responsiveness, and to further reduce the light in a short time. You can write patterns.

An image forming apparatus according to a fourth aspect of the present invention comprises a spatial light modulator, and an optical pattern for writing is input to the spatial light modulator by the optical pattern input means. In the spatial light modulator, a light pattern is optically input from one side to write the light pattern, and light is emitted from the other side to read the written light pattern. When writing this light pattern, the exposure means exposes the spatial light modulator with a predetermined exposure amount. Therefore, the spatial light modulator is activated with a predetermined exposure amount before writing the light pattern, and can write the light pattern with faster response, that is, in a shorter time. The light from the other side when reading the light pattern is emitted by the irradiation means as transmitted light or reflected light of the original image. At the same time, the irradiation means irradiates the light-sensitive material with the light pattern read from the spatial light modulator. Therefore, an image can be quickly created from the light pattern read in a short time.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In this embodiment, the present invention is applied to a photographic printer that creates a print using a secondary image formed from a photographic film.

As shown in FIG. 1, the photographic printer 10 includes a lamp 12, which is mounted in a reflector 14. Above the reflector 14, an infrared / ultraviolet cut filter 16 for blocking wavelengths unnecessary for exposure is arranged. Above the infrared / ultraviolet cut filter 16, a disc-shaped filter unit 18 in which three color filters of red (R), green (G), and blue (B) and an ND filter are fixedly arranged is arranged. , R,
The G, B or ND filter is rotationally driven by the filter driving unit 58 so as to stop at a position on the optical path.

Above the filter unit 18, a diffusion plate 20 for diffusing the light passing through the filter is arranged. A film carrier 24 for sandwiching the negative film 22 and conveying the frame to be printed on the optical path is arranged above the diffusion plate 20. Film carrier 24
Are driven by the carrier drive unit 48. An objective lens 26 is arranged above the film carrier 24. Above the objective lens 26, a polarization beam splitter 28 that is inclined at 45 ° with respect to the optical path and that splits the transmitted light that has passed through the frame to be printed into two directions is arranged. Above the polarization beam splitter 28, an image area sensor 30 is arranged which can be switched between an image pickup mode for picking up an image of a frame to be printed and a three-color separation photometric mode for measuring the transmitted light of the frame to be printed for each of three RGB colors. .

A spatial light modulator 32 (described in detail later) is arranged on the side of the polarization beam splitter 28, and a predetermined voltage of a predetermined frequency is applied to the spatial light modulator 32 from the modulator control unit 46 at the time of writing. To be done. A writing CR coated with a high-luminance phosphor on the side of the spatial light modulator 32.
T40 is arranged. The writing CRT 40 is for writing an image on the spatial light modulator 32 by light. The writing CRT 40 is controlled by the CRT control unit 52 to write an image. Although details will be described later, at the time of writing an image, the CRT control unit 52 controls the writing CRT 40 so that the spatial light modulator 32 is uniformly exposed (pre-exposure) with a predetermined exposure amount.

An exposure magnifying lens 34 for printing an image on a color paper 38 as a photosensitive material is arranged on the side of the polarization beam splitter 28 and on the side opposite to the spatial light modulator 32. Exposure magnifying lens 34 and color paper 3
A shutter 36 is disposed between the shutters 8 and 8. The shutter 36 is opened and closed by the shutter drive unit 64. In addition,
The color paper 38 is moved to a predetermined exposure position by the power of the roller driving unit 60 that drives the pulling roller 62.

The image area sensor 30 is connected to a monitor image processing section 42, and the monitor image processing section 42 is connected to a monitor CRT 44. The image area sensor 30, the monitor image processing unit 42, the modulation element control unit 46,
The carrier drive unit 48, the CRT control unit 52, the filter drive unit 58, the roller drive unit 60, and the shutter drive unit 64 are
It is connected to the controller 50. A keyboard 54 for operating the controller 50 and a display 56 for displaying the operation status of the controller 50 are connected to the controller 50.

As shown in FIG. 2, the controller 50 is
It is equipped with a bus 50A. The bus 50A has a CPU 50
B, ROM 50C, RAM 50D and I / O interface 50E are connected.

As shown in FIG. 3, the spatial light modulator 32.
The glass substrate layer 32A, the transparent electrode layer 32B, the photoconductor layer 32C, the light shielding layer 32D, the dielectric reflection layer 32E, the light modulation layer 32F, the transparent electrode layer 32G, and the glass substrate layer 32H are sequentially laminated. The predetermined voltage is applied between the transparent electrode layers 32B and 32G. In the light modulation layer 32F, nematic liquid crystal having negative dielectric anisotropy is homeotropically aligned, and alignment layers 32J and 32K for homeotropically aligning the liquid crystal are provided on both sides of the light modulation layer 32F. As for the resistance value of the photoconductor layer 32C, the resistance value R _OFF per unit when light is not incident from the glass substrate layer 32A side and the resistance value R _ON per unit when light is incident are optically modulated. The resistance value R _LC per unit of the layer 32F is selected so as to satisfy the following expression (1).

R _OFF ≫R _LC ≫R _ON・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1)

Therefore, when light is not incident from the glass substrate layer 32A side, most of the applied voltage is the photoconductor layer 32.
The voltage applied to C does not apply a sufficient voltage to the light modulation layer 32F connected in series to the photoconductor layer 32C, so that the light modulation layer 3
At 2F, the electro-optical effect due to the liquid crystal does not occur. When light enters from the glass substrate layer 32A side, the photoconductor layer 32C
Resistance decreases and a voltage is applied to the light modulation layer 32F, and an electro-optical effect is generated. When the light emitted from the glass substrate layer 32A side is image information having an intensity distribution (when an image is written by the writing CRT 40), a voltage distribution corresponding to the intensity distribution is applied to the light modulation layer 32F. An image corresponding to the applied image is formed on the light modulation layer 32F by the electro-optic effect. The dielectric reflection layer 32E is ZnS / M
It is composed of a dielectric multilayer film such as gF ₂ . For this reason,
When light enters from the glass substrate layer 32H side, the image formed by the electro-optical effect described above is displayed on the dielectric reflection layer 32E.
And is emitted to the glass substrate layer 32H side. The light-shielding layer 32D absorbs the light that has passed through the dielectric reflection layer 32E out of the light that has entered from the glass substrate layer 32H side and prevents it from entering the photoconductor layer 32C.

Next, the operation of this embodiment will be described with reference to the drawings. FIG. 4 shows a processing flow of the photo printer according to the present embodiment. Step 10 in FIG.
In 0, the light source unevenness caused by dust and dust is measured, and in the next step 102, the image for which the finished print is expected is CR.
The image is displayed at T44, and in the next step 104, the image to be exposed is corrected in accordance with the sensitivity of the color paper 38, and in the next step 106, the RGB three colors are subjected to exposure processing to create a print.

In step 100, the ND filter is set on the optical path, and the film carrier 24 is moved to the optical path in the state where the negative film is not loaded. As a result, the light from the lamp 12 is transmitted through the infrared / ultraviolet cut filter 16, ND.
The light passes through the filter, the diffusion plate 20, the film carrier 24, the objective lens 26, and the polarization beam splitter 28 in order and reaches the image area sensor 30. After that, the image area sensor 30 captures an image to measure the unevenness of the light source, and the measured data is stored in the RAM 50D.

In step 102, the image area sensor 30 is first set to the image pickup mode, and the spectral sensitivity data of the color paper 38 and the spectral sensitivity data of the image area sensor 30 are output to the monitor image processing section 42.
After the print target frame of the negative film 22 loaded in the film carrier 24 is set on the optical path, the print target frame is imaged. The captured video signal of the print target frame is output to the monitor image processing unit 42.
The monitor image processing unit 42 corrects the A / D conversion, the negative / positive conversion, and the difference between the spectral sensitivity of the color paper and the spectral sensitivity of the image area sensor, and outputs the corrected video signal to the monitor CRT 44. This allows the monitor C
An image for which a finished print is expected is displayed on RT44.

In step 102, the tint and the density of the displayed image may be corrected by the correction data input from the keyboard 54. The correction data includes density data and color correction data, and it is preferable that the correction CRT 40 can be input for each pixel.
This correction data is input by the keyboard 54, displayed on the display 56, and stored in the RAM 50D. The monitor image processing unit 42 generates a video signal into which the above correction data is folded, and the monitor CRT 44 displays the final predicted finished print image.

In step 104, the image area sensor 30 is set to the photometric mode, the R filter, the G filter, and the B filter are sequentially set on the optical path, and the frame to be printed is measured by the image area sensor 30 for each three colors. To do. Next, the LATD value (accumulated transmission density value) for each color
Or the density of the transparent original image for each minute area (area corresponding to the pixel in the spatial light modulator) is calculated, and the color paper 3
The density for each color formed on the color paper 38 is calculated from the sensitivity data of No. 8 and the calculated density of the transparent original image for each minute area. Next, the exposure amount for each micro area is calculated for each of the three RGB colors, the shutter opening time is determined for each of the three colors, and the write data for each of the three colors to be output to the CRT control unit 52 is determined and stored. . When there is light source unevenness measured in step 100, the write data is determined and stored as a value in which the unevenness is corrected.

When determining the write data, the negative
Consider the characteristics of the film and the characteristics of the color paper.
preferable. Fig. 5 shows the characteristics of the negative film and the color pattern.
Characteristics, the horizontal axis represents subject brightness and the vertical axis represents film density.
With the negative film characteristic curve 90 in the coordinate system with the
The horizontal axis shows the print density and the vertical axis shows the printing exposure amount.
In the coordinate system shown, the color paper characteristic curve 92 is shown.
Was. Color paper density change width D_TwoEquivalent to
Area B of the linear printing exposure amount of the super characteristic curve 92 ₁Other than
Area B_Two, B_ThreeCan be reproduced in detail on color paper.
I can't. This is generally the case for exposing negative film to light-sensitive material.
When exposed to light, the sensitivity of the photosensitive material is higher than that of the negative film
This is because the area is smaller. Therefore, calculate the above concentration
And the density of the transparent original image for each micro area
Performs gradation correction based on the density difference formed on color paper
Is preferred. Note that the writing light to the spatial light modulator 32 is
The relationship between the intensity and the exposure is R as a gradation control curve.
It is stored in the OM50C.

When step 106 in FIG. 4 is executed, the exposure processing in FIG. 6 is executed, the color paper 38 is conveyed in step 150, and in the next step 152, one of the R, G, and B filters is filtered. It is set on the optical path. In the present embodiment, the R, G, and B filters will be processed in this order.

In step 152, the R filter is set on the optical path, and in the next step 153, pre-exposure for improving the optical response is performed. Next Step 154
Then, the correction reflection image for the R image is displayed on the writing CRT 40. As a result, the pre-exposed spatial light modulator 3
An image is formed on the second light modulation layer 32F. In this way, at the time of writing, pre-exposure is performed, and after the response is improved, the writing processing of the corrected reflection image for the R image is quickly performed. In the present embodiment, the pre-exposure displays the brightest uniform bright display on the writing CRT 40 for a predetermined time (17 milliseconds in the present embodiment). In this pre-exposure, as shown in FIG. 12, the writing CRT 40 is not used for pre-exposure, a dedicated light source 74 for pre-exposure is provided independently, and spatial light modulation is performed by uniform exposure by turning on the dedicated light source 74. The device may be pre-exposed.

Next, the timer is set to the determined time and the shutter is opened (steps 156 and 158).
As a result, a part of the transmitted light transmitted through the frame to be printed on the negative film 22 is branched by the polarization beam splitter 28 and reaches the spatial light modulator 32. The transmitted light and the image formed on the light modulation layer 32F are reflected by the dielectric reflection layer 32E. Therefore, the transmission image of the frame to be printed and the image formed on the light modulation layer 32F are combined, and the exposure magnifying lens 34 forms an image on the color paper 38 for printing. When the opening time of the shutter in the R filter reaches the time determined above, the shutter is closed (step 1
60, 162).

Next, the processing of the R filter is similarly performed for the G filter and the B filter, and when the above processing is completed for all the filters, this routine is ended (step 164).

As described above, an image is written in the spatial light modulation element 32, and the written image is exposed to light for correcting the image to produce a print.

Here, writing of an image in the spatial light modulator 32 provided in the photographic printer of the present embodiment will be described in detail.

FIG. 7A shows a conventional spatial light modulator 32.
The applied waveform of the voltage applied to is shown. Normally, in order to improve the response for reflecting light, the bias voltage V _B is applied to the spatial light modulator 32 even when it is not written. When writing an image to the spatial light modulator 32, the bias voltage V _B is applied. A built-in voltage V _W is applied and light is emitted. That is, the light of the written image is incident from the glass substrate layer 32A side (FIG. 3), the voltage distribution corresponding to the intensity distribution of the light is applied to the light modulation layer 32F, and the image corresponding to the written image is generated. The light modulation layer 32F is formed by the electro-optic effect. Therefore, when light is incident from the glass substrate layer 32H side, the light is reflected by the dielectric reflection layer 32E by the image formed by the electro-optical effect. This reflected light reaches the color paper 38.

When writing an image in this way, the response of the spatial light modulator 32, that is, the response for reflecting light from the start thereof, gradually changes. As described above, since the spatial light modulator 32 has the response characteristic, the write voltage V _{W is}
When the application of the light and the irradiation of the original image are started from time ts, the amount of reflected light in the spatial light modulator 32 gradually increases after a predetermined time from the start time ts, and a constant reflection occurs, as shown in FIG. 7 (2). The amount of light becomes I.

When the writing of the image is finished, the irradiation of the original image is finished, the application of the writing voltage V _W is finished, and the bias voltage is switched to the bias voltage V _B. At the end of this image writing, similarly to the above, since the spatial light modulator 32 has the response characteristic, the spatial light modulator 32 gradually decreases after a predetermined time after the end time te, and the reflected light amount becomes the minimum.

As described above, since the spatial light modulation element 32 has an optical response characteristic, in order to write an image in the spatial light modulation element 32, a time period in which the reflected light quantity is substantially stabilized is taken into consideration. It will cost. Therefore, the time required for writing cannot be shortened, and the secondary image cannot be obtained in a short time.

The inventor of the present invention measures the responsivity which changes with the application of an electrical signal to the spatial light modulator 32.
Bias amplitude dependence and write voltage dependence experiments were conducted, and the results shown in FIGS. 8 and 9 were obtained. FIG. 8 shows the relationship between the amplitude of the bias voltage and the time T _ON from the start time ts until the reflected light amount reaches 90% of the constant reflected light amount I for each of the different write voltages. The result. The image to be irradiated (the image to be written) is obtained by uniformly exposing and measuring the image having the brightness that gives the maximum amount of reflected light. Further, FIG. 9 shows that the amplitude of the bias voltage for each write voltage and 10% of the constant reflected light amount I from the end time te.
It is the result of measuring the time T _OFF until the amount of reflected light reaches. In the figure, the solid line is 4.8V, the dashed line is 4.7V, 2
The dotted chain line is 5.2V, the dotted chain line is 5.5V, and the dotted line is 6.5V.
The write voltage of V is shown.

As can be seen from FIG. 8, the response time (time T _ON until 90% of the reflected light amount I reaches) shows a substantially flat characteristic even when the amplitude of the bias voltage is changed, and the write voltage is Shows that the response time (time T _ON ) becomes shorter with increasing. Further, as understood from FIG. 9, the response time (time T _OFF until the reflected light amount I reaches 10%) does not change substantially even if the write voltage is changed.

Therefore, the response time (time T _ON ) can be shortened by increasing the write voltage. However, in order to further shorten the response time (time T _ON ), the write voltage is changed. It has to be increased further.

FIG. 13 shows the relationship between the write voltage and the light intensity. FIG. 13 shows the measurement results in a coordinate system in which the horizontal axis is the writing voltage and the vertical axis is the intensity ratio of the reflected light to the incident light. The intensity is measured by an epi-polarization microscope with a liquid crystal cell placed on an aluminum vapor deposition mirror. As can be seen from the figure,
The light intensity ratio changes remarkably between the write voltage of about 4.5 V and about 6.5 V, but when it exceeds about 6.5 V, the intensity ratio becomes substantially constant. Therefore, the responsiveness cannot be improved even if the write voltage is increased.

As a result of various other experiments, the present inventor has shown that the spatial light is written immediately before the writing is started or at the writing time between the start of writing and the formation of an image on the spatial light modulator 32. It was found that the spatial light modulator 32 is activated and the response is improved by uniformly exposing the modulator 32 with a predetermined exposure amount.

Therefore, in this embodiment, at the beginning of the writing time, the spatial light modulator 3 is exposed with an exposure amount larger than the exposure amount.
2 is pre-exposed. Thus, at the beginning of the writing time, the spatial light modulation element 32 is uniformly exposed with a predetermined exposure amount, that is, pre-exposed, so that the spatial light modulation element 32 is irrespective of the level of the writing voltage applied at the writing time. Can be quickly activated, and the time required for writing can be shortened.

Here, the present inventor conducted an experiment on the effectiveness of pre-exposure, and obtained the results shown in FIG. FIG. 10 shows the relationship between the gray level (gradation) of the image and the response time (T _ON ). The state of pre-exposure in a coordinate system with the horizontal axis representing the gray level and the vertical axis representing the response time. It is the result of measuring the characteristics when V is changed and when there is no pre-exposure. In addition, the cell gap was 4.0 μm in this measurement.
6. Using the liquid crystal of No. 6, voltage (amplitude) at a frequency of 1 kHz.
A 2V signal is applied to the spatial light modulator 32. In the figure, the solid line 72A indicates the brightest uniform bright display by the writing CRT for a predetermined time (17 milliseconds in this embodiment).
11 shows the measurement result when the gray pattern 70 (FIG. 11) is displayed on the writing CRT after pre-exposure.
B shows the measurement result when the gray pattern 70 is displayed on the writing CRT after pre-exposure for a predetermined time (7 milliseconds in this embodiment) by the light source provided separately from the writing CRT. On the other hand, the dotted line 72C indicates the measurement result when the gray pattern 70 is displayed on the writing CRT without the pre-exposure as in the conventional case.

The gray level here is a value standardized with 100 when the reflected light intensity of the liquid crystal cell is maximum. That is, as shown in FIG. 11, a reflection intensity region corresponding to the grayscale of the gray pattern 70 having the grayscale of 0, 20, 40, 60, 80, and 100% of brightness is formed in the spatial light modulator. That means. For the response time, display the gray pattern 70 on the writing CRT,
The time until the image (area of the reflection intensity corresponding to the gradation of the gray pattern 70) corresponding to the display image (gray pattern 70) of the writing CRT is formed on the spatial light modulator is measured from the start of display. is there.

As can be seen from FIG. 10, the response time when the image is written after the pre-exposure is shortened as compared with the case where the conventional bias voltage is applied. Therefore, the time required to write an image in the spatial light modulation element can be shortened, and the time required to read the image formed in the spatial light modulation element and make a print can be shortened.

As described above, in the present embodiment, it is not necessary to apply a bias voltage to the spatial light modulator 32 as in the prior art, and the spatial light modulator 32 is exposed with a constant exposure amount at the beginning of writing. Only the spatial light modulator 32
Can be activated, the time required for writing can be shortened, and the time for creating a print can be shortened.

In the above embodiment, the case where the present invention is applied to the photographic printer has been described, but the present invention is not limited to the photographic printer, and can be used in a printing plate making machine or an electrophotographic apparatus. The present invention can be applied to an apparatus that creates a secondary image from an image using a spatial light modulator and creates a final image (for example, a copy image) from the created secondary image. Further, it can be applied to a projection device that projects the created secondary image onto a screen or the like.

In the above embodiment, the case where the pre-exposure is performed by the writing CRT or the dedicated light source has been described.
In order to obtain the exposure amount during the pre-exposure, either or both of the brightness and the exposure time can be changed, and the exposure amount of the light finally radiated to the spatial light modulator activates the spatial light modulator. It is sufficient that the exposure amount is sufficient to realize the change.

Further, in the above embodiment, the case where the spatial light modulator is uniformly pre-exposed has been described, but the present invention is not limited to this, and a part of the spatial light modulator is pre-exposed. You may do it. For example, in an image to be written, when an area that requires time to write can be set in advance by photometry or the like, only that area may be pre-exposed, and the exposure amount of that area is larger than that of other areas. You may make it expose in quantity. By doing so, a stable response time can be obtained within the range of the gray level dynamic range.
Furthermore, the exposure amount of the pre-exposure may be controlled for each minute area (pixel) of the spatial light modulator. By doing so, a stable response time can be obtained for each minute region of the spatial light modulator.

[0055]

As described above, according to the method for driving a spatial light modulator of the present invention, before writing an optical pattern, the spatial light modulator is irradiated with light having a predetermined exposure amount. The spatial light modulator is activated by light having a predetermined exposure amount, and has an effect that a light pattern can be written in a short time.

According to the image forming apparatus of the present invention, the spatial light modulator is activated by the exposure amount exposed by the exposing means,
The light pattern is written in a short time, and the written light pattern is read by irradiating the transmitted light or the reflected light of the original image by the irradiation unit, and the read light pattern is irradiated to the photosensitive material. There is an effect that an image can be created from the light pattern read out in a short time.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of a photographic printer.

FIG. 2 is a block diagram illustrating a configuration of a controller.

FIG. 3 is a diagram showing a configuration of a spatial light modulator.

FIG. 4 is a flowchart showing a flow of processing for creating a print.

FIG. 5 is a diagram showing the characteristics of a negative film and the characteristics of color paper.

FIG. 6 is a flow chart showing details of step 106 and showing an exposure procedure of RGB three colors.

FIG. 7 shows characteristics of the spatial light modulator at the time of writing, (1) shows a signal including a bias voltage applied to a conventional spatial light modulator, and (2) shows an optical property of the spatial light modulator. It shows responsiveness.

8 is a diagram illustrating a bias amplitude and a response time (T
It is a characteristic diagram showing the relationship of ( _ON ).

9 is a diagram showing the bias amplitude and response time (T
It is a characteristic view showing the relationship of ( _OFF ).

FIG. 10 is a characteristic diagram showing a relationship between a gray level and a response time of a spatial light modulation element by pre-exposure at the time of writing.

FIG. 11 is an image diagram showing a gray pattern.

FIG. 12 is a conceptual diagram showing a configuration for performing pre-exposure with a dedicated light source.

FIG. 13 is a characteristic diagram showing a relationship between an applied voltage and a light intensity ratio in the spatial light modulator.

[Explanation of symbols]

 12 lamps 32 spatial light modulator 38 color paper 40 writing CRT 46 modulator controller 50 controller

Claims (4)

[Claims] 1. A spatial light modulator in which a light pattern is written by optically inputting the light pattern from one side, and the written light pattern is read by irradiating light from the other side, A method for driving a spatial light modulator in which a predetermined amount of light is emitted before writing a light pattern. 2. The space according to claim 1, wherein before the writing of the light pattern, the spatial light modulator is uniformly irradiated with light having an exposure amount larger than that of the light pattern. Driving method of optical modulator. 3. When the light pattern is an image having gradation, light having an exposure amount larger than an exposure amount corresponding to the predetermined gradation is applied to an area of the light pattern having the predetermined gradation. The method for driving the spatial light modulator according to claim 1. 4. A spatial light modulator in which the light pattern is written by optically inputting the light pattern from one side, and the written light pattern is read by irradiating light from the other side, Light pattern input means for inputting the light pattern for writing in the spatial light modulator, and irradiating the spatial light modulator with transmitted light or reflected light of the original image as the light and reading from the spatial light modulator. An image forming apparatus comprising: an irradiation unit that irradiates the photosensitive material with the formed light pattern; and an exposure unit that exposes the spatial light modulator with a predetermined exposure amount before inputting the light pattern.