JPH08271850A - Liquid crystal optical device - Google Patents

Abstract

PURPOSE: To prevent the quality of a formed image from being deteriorated by correcting the uneveness of the brightness of the formed image. CONSTITUTION: When an image signal is inputted, a synchronizing separation circuit 5 detects a horizontal synchronizing signal, and a lamp signal generation circuit 6 outputs a lamp signal (correction signal) synchronous with the horizontal synchronizing signal. A signal correction circuit 7 corrects the image signal in accordance with the lamp signal, and a liquid crystal panel driving part 8 drives a liquid crystal panel 1 based on the corrected image signal. When a printing switch is operated, a light source 2 emits light and a displayed picture on the panel 1 is formed and exposed on a photoreceptor 4 by a lens 3, At such a time, since the image signal inputted in the panel 1 is corrected so that the scanning starting side of one scanning line may be brighter than the scanning finishing side thereof, the image having no unevenness is recorded on the photoreceptor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal optical device.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal optical device, for example, a liquid crystal projector that images an image displayed on a liquid crystal panel on a screen or the like by an image forming optical system such as a lens and displays the image displayed on the liquid crystal panel by a lens or the like. 2. Description of the Related Art Image recording devices and the like are generally known in which an image is formed by exposing an image on a photosensitive member by the image forming optical system of FIG.

[0003]

However, since the above-described image forms a display image of the liquid crystal panel at a desired position by an image forming optical system such as a lens, the viewing angle characteristics of the liquid crystal panel and the angle of view of the lens are different. Due to the above relationship, there is a problem in that the amount of light of the formed image becomes uneven and the image quality deteriorates.

The uneven light quantity of the formed image will be described below.

Generally, in a liquid crystal panel, the brightness and the contrast change depending on the angle and the direction viewed by the user, so that the viewing angle characteristics in the direction which is considered to be the most frequently used are usually optimized. The conditions are set.
However, if an inexpensive lens with a small aperture or a lens with a short focal length is used as the image forming optical system, the apparent viewing angle from the lens is significantly different between the central part and the peripheral part of the liquid crystal panel. As a result, a large change in the amount of light occurs in the formed image, and uneven brightness occurs as shown in FIG. 11, so the image quality of the formed image deteriorates. Figure 11
FIG. 11A shows a state in which the image becomes brighter from left to right in the horizontal direction of the drawing, and FIG. 11B shows a state of gradually becoming brighter from the upper left direction to the lower right direction in the drawing. The state in which the amount of light differs in the formed image changes depending on conditions such as the orientation of the liquid crystal panel and the angle of view of the lens.

The object of the invention relating to the liquid crystal optical device of the present application is to:
An object of the present invention is to provide a liquid crystal optical device that prevents deterioration of the quality of a formed image.

[0007]

SUMMARY OF THE INVENTION An invention relating to a liquid crystal optical device of the present application is a liquid crystal panel in which a plurality of pixels which receive an image signal and are selectively in a light transmitting state or a light blocking state are arranged in a matrix. A light source for irradiating the liquid crystal panel, an optical means for forming a projected image transmitted through the liquid crystal panel by the light source at a desired position, and a correction signal for correcting unevenness in brightness of the formed image. The above-mentioned object is achieved by providing a correction signal output means for outputting and a correction means for correcting the image signal according to the correction signal and outputting the corrected image signal to the liquid crystal panel.

It is desirable that the correction signal is a signal whose voltage changes every horizontal period and / or vertical period of the image signal.

The correction signal may be a ramp signal.

The correction signal may be an exponential waveform signal.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention relating to the liquid crystal optical device of the present application will be specifically described below with reference to the embodiments shown in the drawings. This example is an example in which the present invention is applied to a recording device.

In FIG. 1, reference numeral 1 denotes a liquid crystal panel, which is a light transmissive liquid crystal panel in this example for displaying an image signal of a television or the like. The transmittance is normally white when a voltage is applied. It will decrease. In the case of a relatively inexpensive liquid crystal panel used as a projector or a viewfinder, it has a size of about 1 inch and has about 230 pixels in the vertical direction and about 400 to 800 pixels in the horizontal direction. An image corresponding to one field of can be displayed.
Reference numeral 2 is a light source, and in this example, a halogen lamp used for high-intensity lighting or the like is used. Reference numeral 2a is a reflection mirror having a parabolic cross section, for example, for efficiently illuminating the liquid crystal panel 1. Reference numeral 3 denotes an image forming optical system which constitutes an optical means. In this example, a lens optical system for forming an image on the liquid crystal panel 1 on the photoconductor 4 at a predetermined magnification is used. If a system is used, or if an output image of the same size as that of the liquid crystal panel is sufficient, a unit size optical system can be used. As the photoconductor 4, in this example, a color or monochrome one such as a normal camera negative film or instant film is used. Reference numeral 5 denotes a sync separation circuit, which extracts a horizontal sync signal from an input image signal. In this example, it is assumed that a composite video signal used in television broadcasting or the like is handled as an image signal, but especially when a synchronization signal is independently input such as a component video signal, the synchronization separation is performed. There is no need to provide a circuit. Reference numeral 6 denotes a ramp signal generation circuit which constitutes a correction signal output means, and outputs a desired ramp signal (correction signal) in synchronization with the horizontal sync signal input from the sync separation circuit 5 by using an integration circuit. The lamp signal (correction signal) is appropriately set based on the image having uneven brightness formed by the lens 3 when the image signal is not corrected, and the image formed Corrects the uneven brightness. 7 is a signal correction circuit,
As shown in FIG. 2, it is composed of an operational amplifier 71 and resistors 72 and 73, and corrects the image signal according to the correction signal. Returning to FIG. 1, a liquid crystal panel drive unit 8 drives the liquid crystal panel 1 according to the image signal corrected by the signal correction circuit 7. The signal correction circuit 7 and the liquid crystal panel drive unit 8 constitute a correction means. A timing circuit 9 outputs a light emission timing signal by operating a print switch (not shown). A light source drive circuit 10 drives the light source 2.

Next, the operation will be described with reference to FIG. In this example, when an image displayed by the liquid crystal panel 1 is formed on the photoconductor 4 by a normal image signal, that is, when the image is not corrected, as shown in FIG. It is assumed to be in the same direction as the scanning direction of panel 1.) It is supposed to be in a bright state. In this case, the ramp waveform (correction signal) output by the ramp signal generation circuit 6 is shown in FIG.
As shown in (c), a scanning line whose end point is darker than its start point is used.

When the image signal as shown in FIG. 3 (a) is input, the sync separation circuit 5 separates the horizontal sync signal as shown in FIG. 3 (b). With the separated horizontal synchronizing signal, the ramp signal generating circuit 6 outputs a ramp signal (correction signal) as shown in FIG. 3C synchronized with the horizontal synchronizing signal.

The signal correction circuit 7 performs correction by adding the ramp signal and the image signal as shown in FIG.
The polarity is inverted every horizontal cycle. The liquid crystal panel drive unit 8 drives the liquid crystal panel 1 based on the corrected image signal.
When a print switch (not shown) is operated here, the light source 2 emits light, and the image displayed on the liquid crystal panel 1 is imaged and exposed on the photoconductor 4 by the lens 3. At this time, since the image signal input to the liquid crystal panel 1 is corrected so that the scanning start side becomes brighter than the scanning end side in one scanning line, an even image is recorded on the photoconductor 4.

In this case, by correcting the image signal, the image can be displayed only at a lower contrast than the liquid crystal panel 1 originally has, but the contrast is emphasized in the photoconductor normally used for such an application. Since it has the characteristics, when compared with the application in which the user directly observes the image, sufficient contrast can be obtained even by performing such correction.

As described above, it is possible to correct the unevenness of the brightness of the image plane due to the viewing angle characteristic of the liquid crystal panel with a simple structure using an inexpensive lens having a small aperture. Further, even when a lens having a short focal length is used, it is possible to correct an image formed, so that the apparatus can be downsized.

If the liquid crystal panel 1 has a viewing angle characteristic such that the liquid crystal panel 1 has a light amount distribution in the vertical direction when an image is formed on the photoconductor, the vertical sync signal is separated by a sync signal separation circuit.
If the ramp signal generating circuit generates a ramp waveform synchronized with the vertical synchronizing signal, the same effect as described above can be obtained. Similarly, when the viewing angle characteristic of the liquid crystal panel 1 has a light amount distribution in an oblique direction when an image is formed on the photoconductor, two sets of ramp waveforms are synchronized with each of the horizontal synchronizing signal and the vertical synchronizing signal. If the signals are used and mixed as shown in FIG. 5 to correct the image signal, the same effect as described above can be obtained.

Further, when the unevenness of the brightness of the image forming surface changes exponentially instead of a constant change amount, the voltage may be corrected with an exponentially changing signal. This can be easily achieved by utilizing the charging characteristics of the capacitor.

Further, when the unevenness of the brightness is almost equal between the bright screen and the dark screen on the image plane (see FIG. 6), the ramp waveform or the like is corrected in the image signal as in the example shown above. Signals may be added, but if the ratio of uneven brightness is significantly different between a bright screen and a dark screen on the image plane, for example, there is almost no uneven brightness on a bright screen, but there is uneven brightness on a dark screen. In the case of a large value (see FIG. 7) or the like, if the signal correction circuit 7 shown in FIG. 8 is used, it is possible to correct uneven brightness on both a bright screen and a dark screen. In FIG. 6, 6a is a characteristic diagram showing the output characteristic of the image plane on the left end side of the liquid crystal panel 1, that is, the pixel at the horizontal scanning start position, and 6b is the right end side of the liquid crystal panel 1, that is, the horizontal scanning end position. FIG. 6 is a characteristic diagram showing the output characteristics of the image plane by the pixels of FIG. In this case, since the inclinations of 6a and 6b are almost equal, the uneven brightness (difference between 6b and 6a) on the dark screen (x1) and the uneven brightness (difference between 6a and 6b) on the bright screen (y1) are almost equal. Equal ratio. On the other hand, in the case of FIG. 7, it is a characteristic diagram showing the output characteristic of the image plane by the pixel at the horizontal scanning start position of the liquid crystal panel 1.
a and 7b, which is a characteristic diagram showing the output characteristic of the image forming surface by the pixels at the horizontal scanning end position of the liquid crystal panel 1, have different inclinations, and the uneven brightness (7
The difference between a and 7b) and the uneven brightness (difference between 7a and 7b) on the bright screen (y2) are very different. In other words, there is almost no unevenness in brightness on a bright screen,
On a dark screen, brightness unevenness is large.

Hereinafter, FIG. 8 will be specifically described. In the present case, a correction example will be described in the case where there is almost no brightness unevenness on a bright screen as shown in FIG. 7 and a large brightness unevenness on a dark screen. In the image signal as shown in FIG. 3A, in the present example, the upper portion A of the drawing is the voltage level corresponding to the brightest screen, and the lower portion B of the drawing is the voltage level corresponding to the darkest screen.

In the figure, 74 is a variable gain amplifier, 7
Reference numerals 5 and 76 are buffer amplifiers. In this case, if the correction is performed only by the lamp signal (correction signal) that corrects the uneven brightness of the dark screen as in the previous example, the uneven brightness disappears on the dark screen, but the uneven brightness is small before the correction. Inconveniently, the brightness unevenness increases on a bright screen. Therefore, in order to correct the voltage level of the image signal corrected by the ramp signal on the bright screen, that is, in the brightest screen in this example, the level of the image signal becomes equal to the A level in FIG. The variable gain amplifier 74 controls the amplitude of the image signal according to the ramp signal (correction signal), adds the ramp signal to this, and corrects the image signal as shown in FIG. Can be recorded.
It should be noted that FIG. 9 is an example in the case where the brightest image signal is corrected. In this case, the darkest image signal is corrected as shown in FIG. 10A, and the slightly brighter image signal is as shown in FIG. 10B. In this example, the correction method in the case of having the display characteristic as shown in FIG. 7 is shown. However, when performing the correction in the case of having the display characteristic other than this, the setting of the variable gain amplifier is set according to the display characteristic. The same effect as described above can be obtained by making appropriate changes.

In the example shown above, filters of colors corresponding to the three primary colors (red, green, blue) of light are arranged in the optical path from the exposure light source to the photosensitive member in a switchable state, and further images are displayed. A color signal selection circuit that separates the signals into color signals corresponding to the three primary colors of light (red, green, and blue) is provided, and a filter and a color signal of each color are appropriately selected, so that red, green, and blue of the photoconductor are selected. Even in a recording apparatus that performs color recording by separately exposing light and superposing the same, the same effect as described above can be obtained.

Further, although the example in which the present invention is applied to the image recording apparatus has been shown above, the same effect can be obtained by applying the present invention to a liquid crystal projector or the like.

[0025]

According to the invention relating to the liquid crystal optical device of the present application, the unevenness of the brightness of the image formed is corrected, so that the deterioration of the image quality due to the uneven brightness can be prevented.

When the brightness unevenness changes periodically in the horizontal direction or periodically in the vertical direction,
If the correction signal is a signal whose voltage changes every horizontal period and / or vertical period of the image signal, the correction can be performed every horizontal period and / or every one vertical period of the image signal.

When the unevenness of the brightness of the image formed changes according to the ramp signal waveform or the exponential function signal waveform, good correction can be performed by using the correction signal as the ramp signal or the exponential function signal.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part of FIG.

FIG. 3 is a waveform diagram for explaining the operation of FIG.

FIG. 4 is an explanatory diagram showing a recording example when an image displayed by the liquid crystal panel 1 is formed on a photoconductor 4 by a normal image signal.

FIG. 5 is a waveform diagram for explaining the operation of another embodiment of the present invention.

FIG. 6 is an explanatory diagram for explaining the operation of the present invention.

FIG. 7 is an explanatory diagram for explaining the operation of the present invention.

FIG. 8 is a block diagram showing a part of another embodiment of the present invention.

9 is a waveform diagram for explaining the operation of the embodiment according to FIG.

10 is a waveform chart for explaining the operation of the embodiment according to FIG.

FIG. 11 is an explanatory diagram showing an image formation screen of a conventional liquid crystal optical device.

[Explanation of symbols]

 1 liquid crystal panel 2 light source 3 optical means 6 correction signal output means 7, 8 correction means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadahiko Yamaoka 4-1-1 Taihei, Sumida-ku, Tokyo Inside Seikosha Co., Ltd.

Claims (4)

[Claims] 1. A liquid crystal panel in which a plurality of pixels selectively receiving or transmitting light in response to an image signal are arranged in a matrix, a light source for illuminating the liquid crystal panel, and an illumination by the light source. Optical means for forming an image of the projection image transmitted through the liquid crystal panel at a desired position, correction signal output means for outputting a correction signal for correcting the unevenness of the brightness of the formed image, and a correction signal output means for responding to the correction signal. And a correcting means for correcting the image signal and outputting the corrected image signal to the liquid crystal panel. 2. The liquid crystal optical device according to claim 1, wherein the correction signal is a signal whose voltage changes every horizontal period and / or vertical period of the image signal. 3. The liquid crystal optical device according to claim 1, wherein the correction signal is a ramp signal. 4. The liquid crystal optical device according to claim 1, wherein the correction signal is an exponential function waveform signal.