JPH09261473A - Image processing method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an output image of a satisfactory quality by detecting uneven grey level by the image density in an unexposed area so as to correct the uneven grey level in an image generated depending on an image recording condition. SOLUTION: Image data read by an image reader 200 is fetched in an image processor 100. The image processor 100 consisting of a personal computer, etc., corrects the gradation characteristic of read image data by referring to gradation irregularity correcting data 101 previously measured and stored in a memory or obtained at the time of reading the image. Correcting data 101 consists of gradation irregularity data obtained by reading the image density of the unexposed area, transmissivity distribution data at the time of applying voltage without exposing the whole surface, light quantity distribution data, etc., of a three-color separation prism. The image processor 100 corrects gradation irregularity based on these data and outputs corrected data to an output device 300 such as CRT, a printer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus for processing digital image data obtained by reading an image recorded on a liquid crystal recording medium having a polymer-liquid crystal composite layer.

[0002]

2. Description of the Related Art Conventionally, an information recording medium having a liquid crystal-polymer composite layer formed on an electrode and an optical sensor having a photoconductive layer formed on the electrode layer are arranged to face each other, and image recording is performed by voltage application exposure. What can be done is disclosed in JP-A-6-130347 and JP-A-5-130347.
No. 165005 is known. Further, an information recording medium in which a liquid crystal-polymer composite is formed on an electrode and an optical sensor in which a photoconductive layer is formed on an electrode layer are opposed to each other and image recording is performed by voltage application exposure is disclosed in JP-A 4-362
No. 916. FIG. 1 is a diagram showing the configuration of an information recording apparatus using such an information recording medium. In the figure, reference numeral 10 denotes an optical sensor, and reference numeral 20 denotes an information recording medium. In the optical sensor 10, a transparent electrode 12 and a photoconductive layer 13 are sequentially laminated on a transparent support 11, and an information recording medium 20 is provided.
A transparent electrode 22 and a liquid crystal-polymer composite layer 23 are sequentially laminated on a transparent support 21, and a skin layer 24 is formed on the liquid crystal layer surface.
Are formed.

A type in which an optical sensor and an information recording medium as shown in FIG. 1 are opposed to each other with a space of about 10 μm using a spacer such as polyethylene or polyimide, and exposed by voltage application, and FIG. A structure in which an optical sensor and an information recording medium are laminated as shown in FIGS. 2A and 2B has also been proposed. In a laminated recording medium, information is recorded on the optical sensor as shown in FIG. 2A. As shown in FIG. 2B, the recording phase is directly laminated and the transparent dielectric intermediate phase 2 is used.
There are some which intervene 5. Such an optical sensor 10
When the information recording medium 20 and the information recording medium 20 are opposed to each other and a voltage is applied between the electrodes 12 and 22 by a power source 30 as shown in FIG. 3 and visible light is irradiated as writing light, the photoconductive layer 13 of the photoconductive layer 13 is irradiated in accordance with the exposure intensity. The conductivity changes, the electric field applied to the liquid crystal layer 23 changes, the alignment state of the liquid crystal changes, and the applied voltage is turned off.
Then, the state is maintained even after the electric field is removed, and the exposure information is recorded.

To reproduce the recorded exposure information, for example, as shown in FIG. 4, reproduction light is emitted from the light source 40 to the information recording medium 20, and the transmitted light is read by the photoelectric conversion device 60 and converted into an electric signal. It is done by As the light source 40, a white light source such as a xenon lamp or a halogen lamp or a laser beam is used, and it is desirable that the reading light with which the liquid crystal recording medium is irradiated be selected to have an appropriate wavelength light and be irradiated. The incident light is modulated according to the alignment state of the liquid crystal of the information recording medium, the transmitted light is converted into a digital signal by the photoelectric conversion device 60 including a photodiode or the like, and the converted signal is output to a printer or a CRT as necessary. Is output.

[0005]

When an image is recorded by such a method, and the recorded image is read to obtain a color image, when recording is performed through uneven thickness of each layer of the recording medium or through an air gap. The unevenness in the gap may cause unevenness in the image. Further, when a color image is recorded using a three-color separation prism, uneven adjustment of the prism also causes unevenness in the image density.

The present invention has been made in view of the above points, and an object of the present invention is to provide an image embedding apparatus capable of correcting unevenness in image density caused by image recording conditions and obtaining an output image of good quality. I am trying.

[0007]

As a method for solving the above problems, the present invention uses a photosensor having a photoconductive layer on an electrode, and a liquid crystal recording medium having a liquid crystal-polymer composite layer on the electrode. When an image is recorded on the image, the recorded image is optically read and converted into a digital signal, and the converted image data is subjected to image processing, the uneven density is detected by the image density of the unexposed area, and the detected uneven density is detected. It is characterized in that the shading unevenness of the image is corrected based on. Further, the present invention is characterized in that an unexposed region is provided in the whole or a part of the periphery of the image recording portion of the liquid crystal recording medium, and unevenness in image density is corrected based on a change in transmittance of the unexposed region. And Further, the present invention is characterized in that the gradation characteristic is estimated based on the image density of the unexposed area, and the shading unevenness of the image is corrected based on the estimated gradation characteristic. Further, according to the present invention, when the liquid crystal is aligned by applying a voltage to the repeatedly usable integrated information recording medium in which the optical sensor and the liquid crystal recording medium are laminated directly or via the dielectric intermediate layer without irradiating light. Is measured, and the unevenness of light and shade is corrected based on the measured transmittance distribution. Further, the present invention is characterized by correcting the adjustment failure of the three-color separation prism used when capturing a color image.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Image processing according to the present invention will be described below with reference to the drawings. First, the unevenness of image density will be described. FIG. 5 shows the result of simulating the voltage applied to the liquid crystal recording layer when the optical sensor and the liquid crystal recording medium are arranged opposite to each other with the air gap layer in between, and a voltage is applied to both electrodes. The simulation was calculated assuming that the optical sensor and the liquid crystal recording medium are parallel circuits of a resistor and a capacitor, respectively, as shown in FIG. As shown in FIG. 5, the voltage distributed to the liquid crystal recording medium is low immediately after the voltage is applied, and thereafter, the voltage applied to the liquid crystal recording medium increases with time due to the current from the resistance component of the photosensor.

Further, in the light portion where the light sensor is irradiated with light, the current of the light sensor flows more than that in the dark portion. Therefore, the voltage of the light portion applied to the liquid crystal recording medium (marked with ◯) is the voltage of the dark portion ( It is higher than the mark ● in the figure. When the liquid crystal recording medium reaches the threshold voltage, the liquid crystal aligns and the transmittance increases, so that the voltage in the dark part becomes equal to or higher than the threshold voltage, and when the liquid crystal starts the alignment, the applied voltage is stopped, and the dark part becomes dark. An image can be recorded by the difference in the transmittance between the light and the bright part.

Assuming that the resistance of the photosensor is proportional to the film thickness of the photosensor and the capacitance of the photosensor is inversely proportional to the film thickness, the liquid crystal recording medium is obtained for the cases where the photosensor film thickness is 9, 10 and 11 μm, respectively. FIG. 7 shows the result of calculation of the voltage applied to the dark part of. In FIG. 7, ● indicates a voltage of 11 μm, ∘ indicates a film thickness of 10 μm, and □ indicates a voltage of 9 μm. As can be seen from FIG. 7, the voltage distributed to the liquid crystal recording medium immediately after the voltage application is determined by the ratio of the capacities of the optical sensor and the liquid crystal recording medium. Therefore, the thicker the optical sensor, the lower the voltage. Further, with respect to the subsequent voltage change, the larger the film thickness of the photosensor, the smaller the current value of the photosensor. Therefore, the voltage applied to the liquid crystal recording medium becomes lower than that when the film thickness is thin.

Further, as shown in FIG. 7, when the film thickness of the optical sensor is 9 μm, the threshold voltage is reached 42 msec after the voltage starts, whereas when the film thickness is 11 μm, the threshold voltage is 6 μm.
The threshold voltage is reached in 2 msec. If 9μm to 11
If image recording is performed using an optical sensor having a film thickness unevenness in the range of μm, if voltage is applied until the voltage of the liquid crystal recording medium in the thickest part of the optical sensor reaches the threshold voltage. The voltage of the liquid crystal medium in the thinnest portion is about 20 V higher than the threshold voltage, and it is considered that the liquid crystal is already aligned and the transmittance is considerably increased.

As described above, due to the film thickness unevenness of the optical sensor,
The voltage applied to the liquid crystal recording medium changes, which causes unevenness in image density. Similarly, in the case of the thickness unevenness of the liquid crystal recording medium, the air gap unevenness, and the monolithic medium in which the optical sensor and the liquid crystal recording layer are laminated with the dielectric intermediate layer interposed, the thickness of the dielectric intermediate layer may be uneven. Causes unevenness in the image density.

Next, a method of correcting unevenness in image density due to such unevenness of the film thickness of the medium and unevenness of the air gap will be described. FIG. 8 shows the results of image recording by projecting and exposing a gray scale in the system of the present invention and changing the voltage application conditions (the applied voltage is the same and the voltage application time is changed). The horizontal axis of the graph is the grayscale reflection density of the subject,
The vertical axis represents the result of reading the image recorded on the liquid crystal recording medium with a dedicated image reading device (scanner) and outputting it as 8-pit data. Applied voltage is 700 V, ○ is voltage application time 55 msec, ● is voltage application time 45 msec
It is.

When the voltage application time is changed under the condition that the applied voltages are equal, the longer the voltage application time is, the higher the voltage applied to the liquid crystal recording medium is, and the higher the transmittance of the dark area is.
Images with different gradation characteristics are similarly recorded when the voltage application time is the same and the applied voltage is changed, or when both are changed.

Such gradation characteristics depend on the transmittance of the dark portion of the liquid crystal recording medium. To explain this, the change in transmittance with respect to the exposure amount (= gradation characteristic) shows a curve as shown in FIG. 9A, the rising in the low exposure region is gentle, and the rising in the middle exposure region is linear. , Saturation in the high exposure range. In this way, the gradation characteristic becomes an S-shaped curve, and if the saturated transmittance and the transmittance of the dark part are determined, the gradation characteristic is almost determined. Since one liquid crystal recording medium can be considered to have almost the same saturated transmittance, the gradation characteristics depend on the transmittance of the dark portion. For example, the transmittance of the dark portion is larger than the solid line in FIG. 9A by T. Then, the characteristic becomes as shown by the broken line. FIG. 9B shows the relationship between the liquid crystal capacitance change and the transmittance change. Since the capacitance change corresponds to the current change and the current change changes linearly with the exposure amount,
The horizontal axis of FIG. 9B is equivalent to the change in exposure amount. During image recording, the voltage application is stopped when the liquid crystal in the dark portion is aligned to some extent. For example, in FIG. 9B, when the voltage application is stopped when the transmittance is T ₁ , and when the transmittance is T _2. When the voltage application is stopped at that time, the magnitude of the capacitance change with respect to the exposure amount change (the slope of the tangent to the curve) is different, and therefore the gradation characteristics are changed. As described above, the gradation characteristic of the liquid crystal recording medium can be almost estimated by measuring the transmittance of the dark portion.

As described above, such a change in the gradation characteristic also occurs due to the uneven film thickness of the recording medium and the unevenness of the air gap. If there is such a portion having different gradation characteristics in the same recording medium, the output from the scanner will be different even in the portion having the same reflectance of the subject, which causes image unevenness. In such a case, if the gradation characteristics at each position of the image are known, it is possible to correct the shading unevenness by correcting the data as shown by the arrow in FIG.

By the way, in practice, it is not possible to measure the transmittance of the dark part for the entire image, so it is necessary to measure the part of the recording medium and estimate the remaining part. The method will be described. FIG. 10 shows a method for measuring the thickness unevenness of the recording medium. The figure shows an example of the shape of an image recording medium for recording a color image. As shown in the figure, RGB images decomposed using three-color separation prisms are recorded on the same plane. The shaded portions at the upper and lower ends of each of the R, G, and B images are spaces for measuring the transmittance of the dark portion of the liquid crystal medium, and this portion is provided by using a mask or the like for shielding light during image recording. This is a region where no light is incident on. The film thickness unevenness of elements such as optical sensors is
In most cases, it happens at a constant rate in the same direction, so
As shown in the figure, by measuring the transmittance of the liquid crystal medium at both ends of the image, the state between them can be estimated.

For example, in FIG. 10, A and B of the R image
FIG. 11 shows a method of measuring the transmittances D _A and D _B at two points and estimating the transmittance of the dark portion between them. As shown, by approximating the point A (position X _A), B point (position X _B) between two points with a straight line, the transmittance D ₁ of the arbitrary position X ₁ is, D ₁ = D _A + ( D _B −D _A ) ・ (X ₁ −X _A ) / (X _B
-X _A ) can be estimated. In this way, when the transmittance of the dark portion at each position is obtained, the gradation characteristic at each position can be estimated, so that the gradation characteristic can be corrected as indicated by the arrow in FIG.

When the recording layer is erasable and can be repeatedly used in an integrated medium in which the optical sensor and the liquid crystal recording layer as described in FIG. 2 are laminated directly or via a dielectric intermediate layer, By applying a voltage to the liquid crystal recording medium in advance without image exposure and measuring the transmittance at each position, the unevenness of the medium can be corrected more accurately than the above method.

Next, a method of correcting unevenness in image density due to a defective optical system such as a prism will be described. In the system of the present invention, when capturing a color image, by using a three-color separation prism 1 in which a prism and a dichroic mirror are combined as shown in FIG. , B are exposed. In FIG. 12, surfaces a and b are dichroic mirrors, so that the B light is reflected on the a surface and the R light is reflected on the b surface. It is difficult to adjust such a three-color separation prism, and poor adjustment may cause unevenness in light and shade due to differences in exposure amount within the same image.

Therefore, as shown in FIG.
FIG. 14 shows the results obtained by recording gray scales on the left and right ends of the G channel image using a color separation prism and reading them with a scanner. Since the prism adjustment is not perfect, the one recorded at the left end (marked with ● in the figure) is darker than the one recorded at the right end (marked with ○ in the figure).

FIG. 15 is a diagram for explaining a method for correcting such a defective adjustment of the prism, in which light from the reflecting plate 2 having a uniform whole is passed through the three-color separation prism 1 to the CCD sensor 3.
To measure the light intensity distribution. 3 according to this measurement result
Since the light and shade data from the color separation prism 1 can be obtained,
Based on this measurement result, the difference in gradation characteristics at each position is corrected as indicated by the arrow in FIG. By doing so, it is possible to correct the shading unevenness. Note that, as shown in the figure, the value to be corrected differs depending on the alignment state of the liquid crystal medium (corresponding to the grayscale reflection density).

FIG. 16 is a conceptual diagram of the configuration of the image processing apparatus of the present invention for correcting unevenness in density. Image reading device 20
The digital image data read by 0 is the image processing apparatus 1
It is taken in by 00. The image processing apparatus 100 is composed of a personal computer or the like, and is measured in advance and stored in a memory.
Alternatively, the shading correction data 1 obtained when the image was read
01, the gradation characteristic of the read image data is corrected. As described above, the correction data includes the uneven density data obtained by reading the image density of the unexposed area, the transmittance distribution data when voltage is applied without exposing the entire image, and the light amount distribution data of the three-color separation prism. , Image processing apparatus 1
00 corrects the shading unevenness based on these data, and outputs the corrected data to the output device 300 such as a CRT or a printer.

[0024]

As described above, according to the present invention, in the processing of the image recorded on the liquid crystal recording medium by using the optical sensor,
Since it has a function of correcting unevenness in image density due to uneven thickness of the recording medium, it is possible to obtain high-quality image data having no unevenness in density.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an information recording device.

FIG. 2 is a diagram showing a configuration of a laminated recording medium.

FIG. 3 is a diagram illustrating recording of exposure information.

FIG. 4 is a diagram illustrating reproduction of exposure information.

FIG. 5 is a simulation of the voltage applied to the liquid crystal recording layer when recording is performed by providing an air gap between the optical sensor and the liquid crystal recording layer.
It is a figure which shows the option result.

FIG. 6 is an equivalent circuit diagram.

FIG. 7 is a diagram showing a relationship between a film thickness of an optical sensor and a voltage applied to a liquid crystal recording medium.

FIG. 8 is a diagram illustrating a change in gradation characteristic when the applied voltage is the same and the exposure time is changed.

FIG. 9 is a diagram showing transmittance characteristics of a liquid crystal recording medium.

FIG. 10 is a diagram illustrating a method of obtaining uneven density data.

FIG. 11 is a diagram illustrating a method of obtaining uneven density data.

FIG. 12 is a diagram illustrating a recording method using a three-color separation prism.

FIG. 13 is a diagram illustrating a method for measuring unevenness in density generated by a three-color separation prism.

FIG. 14 is a diagram showing gradation characteristics when a gray scale is recorded through a three-color separation prism.

FIG. 15 is a diagram showing a light amount distribution measuring method of a three-color separation prism.

FIG. 16 is a diagram showing a configuration of an image processing apparatus of the present invention.

[Explanation of symbols]

100 ... Image processing device, 101 ... Correction data, 200 ...
Image reading device, 300 ... Output device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H04N 1/60 H04N 1/40 DC5 1/46 1/46 ZC5

Claims (10)

[Claims] 1. An optical sensor having a photoconductive layer on an electrode is used to record an image on a liquid crystal recording medium having a liquid crystal-polymer composite layer on the electrode, and the recorded image is optically read to obtain a digital image. In the method of converting the signal into a signal and processing the converted image data, an image characterized by detecting density unevenness by the output image density of the unexposed area and correcting the density unevenness of the image based on the detected density unevenness information Processing method. 2. The image processing method according to claim 1, wherein the unexposed area for detecting unevenness in light and shade is provided in the whole or part of the periphery of the image recording portion of the liquid crystal recording medium. 3. The image processing according to claim 1, wherein the gradation characteristic is estimated based on the output image density of the unexposed area, and the shading unevenness of the image is corrected based on the estimated gradation characteristic. Method. 4. An optical sensor having a transparent electrode and an organic photoconductive layer formed on a support, and a liquid crystal recording medium having a liquid crystal-polymer composite layer formed on the electrode, either directly or via a dielectric intermediate layer. By using a laminated and repeatedly usable integrated type information recording medium, a voltage is applied to align the liquid crystal without image exposure, and the transmittance at this time is measured, so that unevenness in density due to unevenness in thickness of the information recording medium is caused. An image processing method, which comprises measuring and correcting uneven density of a recorded image based on the measured value. 5. An optical sensor having a photoconductive layer on an electrode is used, and an image is recorded on a liquid crystal recording medium having a liquid crystal-polymer composite layer on the electrode through a three-color separation prism, and the recorded image is optically recorded. In the method of reading and converting to digital signals and processing the converted image data, the reflection plate with a uniform surface is photographed, the light amount distribution obtained through the three-color separation prism is measured for each color, and the adjustment of the three-color separation prism is incorrect. An image processing method characterized by correcting the unevenness of lightness and darkness of an image. 6. An image reading means for reading an image recorded on a liquid crystal recording medium having a liquid crystal-polymer composite layer on an electrode and converting it into a digital signal, and an image processing means for correcting the gradation of the read image. The image processing device, wherein the image reading unit corrects unevenness in the density of the image with reference to the correction data. 7. The image processing apparatus according to claim 6, wherein the correction data is density unevenness data obtained by detecting an image density of an unexposed area. 8. The apparatus according to claim 6, wherein the image processing means estimates the gradation characteristic from the output image density of the unexposed area, and corrects the uneven density of the output image based on the estimated gradation characteristic. An image processing device characterized by the above. 9. The apparatus according to claim 6, wherein the correction data is transmittance measurement data when a liquid crystal is aligned by applying a voltage to a reusable integrated information recording medium without image exposure. An image processing device characterized by being present. 10. The image processing apparatus according to claim 6, wherein the correction data is light amount distribution data obtained by measuring the light from the reflecting plate that is uniform over the entire surface through the three-color separation prism.