JP3907746B2 - Pixel defect correction method in image recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention corrects image defects caused by pixel defects of a spatial light modulator in an image recording apparatus that exposes a photosensitive material with recording light modulated by a spatial light modulator and records a gradation image on the photosensitive material. It is about the method.
[0002]
[Prior art]
Conventionally, recording light is spatially modulated based on an image signal by a spatial light modulation element having a plurality of pixels arranged one-dimensionally or two-dimensionally, and the photosensitive material is exposed to the recording material by the recording light. An image recording apparatus that records a gradation image is known.
[0003]
[Problems to be solved by the invention]
In a spatial light modulation element such as a liquid crystal display panel used in this image recording apparatus, defective pixels that cause the recording density to be fixed near the minimum value or near the maximum value occur regardless of the value of the input image signal. There is. In other words, for example, in a transmissive liquid crystal display panel, when a liquid crystal cell that constitutes a pixel has a defect that remains normally closed, the pixels of an image recorded in the liquid crystal cell are fixed to a minimum density, On the other hand, if a defect that remains normally open is caused, the pixels of the image recorded by the liquid crystal cell are fixed at almost the maximum density.
[0004]
Various methods for correcting image defects due to pixel defects of such spatial light modulators have been proposed in the past, but these methods all require some additional optical or mechanical mechanism. The cost of the image recording apparatus is increased. These methods also have a problem that the time required for image recording can be prolonged because additional exposure is required for pixel defect correction.
[0005]
The present invention has been made in view of the above circumstances, and does not require an additional optical or mechanical mechanism and does not prolong the time required for image recording. It is an object of the present invention to provide a method capable of correcting the pixel defect.
[0006]
[Means for Solving the Problems]
The pixel defect correction method in the first image recording apparatus according to the present invention is as described in claim 1.
In an image recording apparatus that spatially modulates recording light based on an image signal by a spatial light modulation element having a plurality of pixels, exposes a photosensitive material with the recording light, and records a gradation image on the photosensitive material.
When the spatial light modulator has a defective pixel that fixes the recording density near the minimum value, the image signal input to the adjacent pixel of the defective pixel is corrected so that the recording density is increased by a predetermined value. It is what.
[0007]
Further, the pixel defect correction method in the second image recording apparatus according to the present invention is the same as the above, in the image recording apparatus similar to the above,
When the spatial light modulator has a defective pixel that fixes the recording density near the maximum value, the image signal input to the adjacent pixel of the defective pixel is corrected so that the recording density is lowered by a predetermined value. It is what.
[0008]
On the other hand, the pixel defect correction method in the third image recording apparatus according to the present invention is the pixel defect correction method according to the first or second aspect, wherein the correction is performed in a region having a higher spatial frequency of the image. It is characterized by raising the degree.
[0009]
According to a fourth aspect of the present invention, there is provided a pixel defect correcting method according to the fourth aspect of the present invention, wherein only the adjacent pixels of the pixel column having the higher pixel density among the vertical and horizontal pixel columns of the spatial light modulator are provided. The above-described correction is performed on the above.
[0010]
【The invention's effect】
(1) to (5) in FIG. 6 schematically show how pixel defects are corrected by the first method of the present invention. (1) in the figure shows a defective pixel. In the figure, P ₀ is a defective pixel, P ₁ , P ₂ , P _3, and P ₄ are four adjacent pixels above, below, left, and right of the defective pixel P _0. Show. The defective pixel P ₀ fixes the recording density in the vicinity of the minimum value regardless of the value of the image signal. Therefore, the lateral intensity distribution of the recording light passing through the pixels in the vicinity is not corrected. As shown in FIG.
[0011]
On the other hand, when the image signal input to the adjacent pixels P ₁ , P ₂ , P ₃ and P ₄ is corrected so that the recording density is increased by a predetermined value, the lateral intensity distribution of the recording light is shown in FIG. As shown in 3). The density distribution of the photosensitive material exposed with the recording light having such an intensity distribution is as shown in FIG.
[0012]
Then, the density distribution that humans feel when observing the photosensitive material recorded in this way is as shown in FIG. That is, the average density in the vicinity of the defective pixel P ₀ is almost the same as when there is no defect, and the density between the defective pixel P ₀ and the adjacent pixels P ₁ , P ₂ , P ₃ and P _4. Since the difference is not felt so much, it is difficult to visually recognize that there is a defect in the image.
[0013]
On the other hand, (1) to (5) in FIG. 7 schematically show how pixel defects are corrected by the second method of the present invention. Contrary to the above, the defective pixel P _{0 in} this case fixes the recording density near the maximum value regardless of the value of the image signal. Therefore, the lateral intensity distribution of the recording light passing through the pixels in the vicinity is If no correction is made, the result is as shown in FIG.
[0014]
On the other hand, when the image signal input to the adjacent pixels P ₁ , P ₂ , P ₃ and P ₄ is corrected so that the recording density is lowered by a predetermined value, the lateral intensity distribution of the recording light is shown in the same figure ( As shown in 3). The density distribution of the photosensitive material exposed with the recording light having such an intensity distribution is as shown in FIG.
[0015]
The density distribution that humans feel when observing the photosensitive material thus exposed is as shown in FIG. 5 (5). In this case as well, it is difficult to visually recognize that the image has a defect.
[0016]
Note that if the density of the adjacent pixel is increased or decreased as described above in a region where the spatial frequency of the image is relatively low, the density change of the adjacent pixel itself due to this correction becomes conspicuous. Conversely, the density change of the adjacent pixels due to the correction is less noticeable in the region where the spatial frequency of the image is higher.
[0017]
Therefore, as in the third pixel defect correction method of the present invention, if the degree of correction is increased in the region where the spatial frequency of the image is higher, the effect of the correction can be obtained remarkably. Can be prevented from standing out.
[0018]
Further, as in the fourth pixel defect correcting method of the present invention, the above correction is performed only on the adjacent pixels of the pixel column having the higher pixel density among the vertical and horizontal pixel columns of the spatial light modulator. Similarly, the effect of the correction can be obtained remarkably, and on the other hand, it is possible to prevent the density change of the adjacent pixels from being noticed by the correction.
[0019]
As described above, the pixel defect correction method of the present invention does not require an optical or mechanical additional mechanism, and can correct pixel defects only by processing an image signal, resulting in a significant increase in cost of the image recording apparatus. There is no. In addition, since the pixel defect correction method of the present invention does not require additional exposure for pixel defect correction, the time required for image recording is not prolonged.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of an image recording apparatus for correcting pixel defects by the method of the present invention. As shown in the figure, this image recording apparatus includes a light source 11 such as a halogen lamp that emits white recording light L for exposing the color photosensitive material 10, and a light source 11 disposed near the focal position. A condensing lens 12 that collimates the recording light L emitted from 11, a mirror array device 13 disposed at a position where the collimated recording light L is incident, and a recording reflected by the mirror array device 13 It has an imaging lens 14 disposed at a position where the light L is incident, and a color filter 15 and a black shutter 16 inserted in the optical path of the recording light L in front of the mirror array device 13. A light absorbing member 18 is disposed at a position outside the optical path of the recording light L between the mirror array device 13 and the imaging lens 14.
[0021]
The mirror array device 13 has a plurality of micromirrors 20 arranged in a two-dimensional array on a silicon substrate 21 as shown in an enlarged view in FIG. Each micromirror 20 is formed in a quadrangular shape from an aluminum alloy or the like, and is arranged with an arrangement pitch a in one mirror arrangement direction X of 17 μm, for example, and an arrangement pitch b in a mirror arrangement direction Y orthogonal thereto is, for example, 17 μm. The size a ′ in the mirror arrangement direction X and the size b ′ in the mirror arrangement direction Y of each micromirror 20 are set to lengths close to the mirror arrangement pitches a and b, respectively.
[0022]
In FIG. 2, one micromirror 20 at the center is omitted, and as shown in the figure, a driving unit for driving each micromirror 20 is provided. The drive unit includes a yoke 22 that supports the micromirror 20 via a mirror support post (not shown), a pair of torsion hinges 23 and 23 that hold the yoke 22, a pair of address electrodes 24 and 24, and elements thereof. A bias bus (not shown) arranged on the lower side of the device is configured to change the direction of the torsion hinge 23 by electrostatic force according to the voltage application state by the bias bus and the address electrodes 24 and 24. ing. Each micromirror 20 is formed with a light non-reflective mask 25 for limiting the effective aperture.
[0023]
Voltage application to the address electrodes 24, 24 for each micromirror 20 is controlled by a driving device 30 (see FIG. 1) that receives an image signal S indicating a gradation image. That is, while no voltage is applied via the address electrodes 24, 24, the torsion hinge 23 (that is, the micromirror 20) is in parallel with the substrate 21, but a voltage having a predetermined polarity is applied to one address electrode 24. Is applied and a complementary voltage of opposite polarity is applied to the other address electrode 24, the micromirror 20 is inclined at an angle -θ with respect to the substrate surface as shown in FIG. When the applied state is reversed, the micromirror 20 is inclined at an angle θ with respect to the substrate surface as shown in FIG.
[0024]
Therefore, in the case of FIG. 3, the recording light L reflected by the micromirror 20 deviates from the opening of the imaging lens 14, and in the case of FIG. 4, the recording light L reflected by the micromirror 20 passes through the imaging lens 14, The photosensitive material 10 is reached. In this way, the incidence of the recording light L on the photosensitive material 10 can be controlled by each micromirror 20 unit. Then, the ON time of each micromirror 20 within the frame time is, for example, pulse width modulated based on the image signal S for each pixel, so that the amount of incident light on the photosensitive material 10 is controlled for each micromirror 20. A gradation image is exposed on the photosensitive material 10.
[0025]
In FIGS. 3 and 4, the imaging lens 14 is shown only to indicate the aperture angle range, and its size and position are different from actual ones. Hereinafter, the state of the micromirror 20 as shown in FIGS. 3 and 4 will be referred to as an OFF state and an ON state, respectively.
[0026]
The color filter 15 shown in FIG. 1 includes an R (red) filter, a G (green) filter, and a B (blue) filter. These color filters are sequentially inserted into the optical path of the recording light L, and the mirror array device 13 is driven based on the color image signals corresponding to the colors during the period in which the color filters are inserted. Note that during the switching period of each color filter, all the micromirrors 20 are turned off. In this way, the color photosensitive material 10 is sequentially exposed to the modulated red, green, and blue light, and a color photographic latent image is recorded thereon. The recording light L reflected by the micro mirror 20 in the OFF state is absorbed by the light absorbing member 18 shown in FIG.
[0027]
Next, correction of pixel defects will be described. In the mirror array device 13, the drive unit of each micromirror 20 may fail, so that it does not move while remaining in the state shown in FIG. If the former pixel defect occurs, the pixel on the photosensitive material 10 corresponding to the defective image element is fixed to regardless lowest concentration value of the image signal S, if the latter pixel defect occurs, the defect pixel on the photosensitive material 10 corresponding to the picture element would be secured to the highest concentration regardless of the value of the image signal S.
[0028]
The drive device 30 of the mirror array device 13 has a configuration for correcting this pixel defect. That is, as shown in FIG. 5, the driving device 30 performs correction processing on the image memory 31 that temporarily stores the image signal S for one image and the image signal S that is supplied from the image memory 31 at a predetermined timing. An image processing unit 32 to be added, a pixel defect information memory 33, and a mirror array device driver 34 are provided. The mirror array device 13 is appropriately inspected as to whether or not each of the micromirrors 20 constituting one pixel has any of the two types of defects as described above. Information about the position of the pixel causing the defect and the defect type are input to the driving device 30, and the information is stored in the pixel defect information memory 33.
[0029]
At the time of image recording, the image processing unit 32 receives information from the pixel defect information memory 33, and there is a micro mirror 20 (which fixes the pixels on the photosensitive material 10 to the minimum density) that remains in the state shown in FIG. In this case, the image signal S input to the four micromirrors 20 adjacent to the micromirror 20 in the vertical and horizontal directions is corrected so that the recording density is increased by a predetermined value. By doing so, in the gradation image recorded on the photosensitive material 10, the image defect due to the defect of the micromirror 20 becomes inconspicuous. The reason is as described in detail with reference to FIG.
[0030]
In addition, the image processing unit 32 receives information from the pixel defect information memory 33, and there is a micromirror 20 (which fixes the pixels on the photosensitive material 10 to the highest density) that has stopped moving in the state of FIG. In this case, the image signal S input to the four minute mirrors 20 adjacent to the minute mirror 20 in the vertical and horizontal directions is corrected so that the recording density is lowered by a predetermined value. By doing so, in the gradation image recorded on the photosensitive material 10, the image defect due to the defect of the micromirror 20 becomes inconspicuous. The reason is as described in detail with reference to FIG.
[0031]
In the above example, the image signals S input to the four adjacent micromirrors 20 are corrected, but only the two micromirrors 20 above and below the defective micromirror 20 or the two micromirrors on the left and right sides are corrected. You may make it correct | amend the image signal S input with respect to only the mirror 20 or the eight minute mirrors 20 slanting up and down.
[0032]
In the mirror array device 13 shown in FIG. 2, the pixel density in the vertical direction is higher than the pixel density in the horizontal direction. Therefore, when correcting each image signal S input to the two micromirrors 20, It is more preferable to correct the image signal S input to the two upper and lower micromirrors 20 than to the left and right. The reason is as described in detail above.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of an image recording apparatus for carrying out the method of the present invention. FIG. 2 is a partially broken front view of a mirror array device used in the image recording apparatus of FIG. FIG. 4 is a side view showing another state of the micromirror of the device. FIG. 5 is a block diagram showing a driving device of the mirror array device. FIG. 7 is an explanatory diagram for explaining how pixel defects are corrected by the method of FIG. 7. FIG. 7 is an explanatory diagram for explaining how pixel defects are corrected by the second method of the present invention.
10 Color photosensitive material
11 Light source
12 Condensing lens
13 Mirror array device
14 Imaging lens
15 Color filter
16 Black shutter
18 Light absorbing member
20 micro mirror
22 York
23 Torsion hinge
24 address electrodes
25 Micromirror mask
30 Mirror array device drive unit
31 Image memory
32 Image processing section
33 Pixel defect information memory
34 Mirror array device driver L Recording light

Claims (4)

In an image recording apparatus that spatially modulates recording light based on an image signal by a spatial light modulation element having a plurality of pixels, exposes a photosensitive material with the recording light, and records a gradation image on the photosensitive material.
When the spatial light modulator has a defective pixel that fixes the recording density near the minimum value, the image signal input to the adjacent pixel of the defective pixel is corrected so as to increase the recording density by a predetermined value. A pixel defect correction method in an image recording apparatus. In an image recording apparatus that spatially modulates recording light based on an image signal by a spatial light modulation element having a plurality of pixels, exposes a photosensitive material with the recording light, and records a gradation image on the photosensitive material.
When the spatial light modulator has a defective pixel that fixes the recording density near the maximum value, the image signal input to the adjacent pixel of the defective pixel is corrected so that the recording density is lowered by a predetermined value. A pixel defect correction method in an image recording apparatus. 3. The pixel defect correction method for an image recording apparatus according to claim 1, wherein the degree of correction is increased in a region having a higher spatial frequency of the image. 4. The image recording apparatus according to claim 1, wherein the correction is performed only on an adjacent pixel of a pixel column having a higher pixel density among vertical and horizontal pixel columns of the spatial light modulator. 5. The pixel defect correction method in FIG.

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