JPH0419740B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] In an image input device, by controlling three color liquid crystal panels consisting of red, green, and blue colors provided in front of a lens, the image input device has both a shading correction function and a filter function. .

[Industrial application field]

The present invention relates to an image input device useful for image readers, facsimile machines, copying machines, etc., which reads characters or figures on a document in color.

[Conventional technology]

In facsimiles and copying machines, images are input by emitting light from a light source onto the surface of a document, condensing the reflected light with a lens, and forming an image on an image sensor to obtain a video signal.

Fluorescent lamps are generally used as light sources, but fluorescent lamps have a shading characteristic in which the amount of light is lower at both ends than at the center. The lens also exhibits a shedding characteristic in which the amount of peripheral light decreases. This causes a difference in the intensity of light received by the image sensor from the center and both ends, resulting in non-uniform image density. Therefore, in order to solve this problem, shading correction is generally performed.

FIG. 4 shows an example of a conventional shading correction mechanism (see Japanese Patent Application Laid-open No. 77570/1983).

In FIG. 4, 41 is an image sensor (CCD);
2 is a lens, and 43 is a liquid crystal panel.

In this example, when reading the white level,
A shading correction pattern 44 is displayed on the liquid crystal panel 43 based on the video signal output from the CCD 41.
is generated and displayed, and this shading correction pattern 44 is automatically adjusted so that the level of the video signal is constant, thereby uniformizing the intensity of light received by the CCD 41.

On the other hand, in color copying machines and the like, when reading a document, the colors are separated into red, green, and blue using filters.

Figure 5 shows a conventional example in this case (Japanese Patent Laid-Open No.
23966)), 51 is CCD,
52 is a lens, 53 is a red liquid crystal panel, 54 is a green liquid crystal panel, and 55 is a blue liquid crystal panel.

In this example, three color liquid crystal panels 53, 5
By repeating the operation three times for each color LCD panel, displaying the selected image in full color among the 4 and 55 images, and scanning one line while leaving the remaining two images transparent. A video signal separated into red, green, and blue colors is obtained from the CCD 51.

By the way, in order to provide both the above-mentioned shading correction mechanism and filter mechanism, conventionally, it was necessary to provide both mechanisms separately.

[Problem that the invention seeks to solve]

As mentioned above, in order to provide an image input device with a filter mechanism in addition to a shading correction mechanism, it is necessary to provide both mechanisms separately, which poses the problem of increasing the size and cost of the device. .

[Means to solve the problem]

According to the present invention, three color liquid crystal panels provided in front of a lens have both a shading correction function and a filter function.

FIG. 1 shows the basic configuration of the present invention.

In FIG. 1, 1 is an imaging device (CCD), 2 is a lens, 3 is a red liquid crystal panel, 4 is a green liquid crystal panel, and 5 is a blue liquid crystal panel.

Light emitted from a light source (not shown) and reflected by the document surface passes through three red, green, and blue liquid crystal panels 3, 4, and 5, and is focused by the lens 2, and is focused on the CCD 1. image and is converted into a video output signal.

The color liquid crystal panels 3, 4, and 5 have a matrix-like structure of dots or tiles.
If a predetermined shading pattern is displayed on each sheet, it will function only as a shading correction plate, and 3
If one of the sheets is displayed in full color and the remaining two are displayed in the same predetermined shading pattern, it functions not only as a shading correction plate but also as a color filter.

[Effect]

According to the present invention, it is possible to have both a shading correction function and a filter function by simply using three color liquid crystal panels.

The operation of the present invention will be specifically explained with reference to FIG.

In FIG. 2, a, b, and c show cases in which both a shading correction function and a filter function are provided, and d shows a case in which only a shading correction function is provided.

First, as in case a, if the red liquid crystal panel is displayed in full color, and the green and blue liquid crystal panels are displayed only on the shading correction pattern, a composite display consisting of the black shading correction pattern and the rest of the red color can be obtained. It will be done. This has a function as a red filter in addition to a shading correction function.

Following the same procedure, case b has a function as a green filter in addition to the shading correction function, and case c has a function as a blue filter in addition to the shading correction function.

Next, when only the shading correction patterns of the red, green, and blue color liquid crystal panels are displayed as in case d, a composite display consisting of the black shading correction pattern and the transparent remainder is obtained. It has only a shading correction function.

〔Example〕

FIG. 3 shows the configuration of one embodiment of the present invention.

In Figure 3, 11 is a CCD, 12 is a lens,
13 is a red liquid crystal panel, 14 is a green liquid crystal panel,
15 is a blue liquid crystal panel, 16 to 18 are liquid crystal drive circuits, 19 to 21 are selectors, 22 is a filter signal generation circuit, and 23 is a shading correction pattern.
Memory 24 is a shading correction control section.

First, the shading correction function will be explained. First, the liquid crystal drive circuits 16, 17, and 18 control the red color.
By driving the green and blue liquid crystal panels 13, 14, 15, the three liquid crystal panels 13, 1
A pattern previously stored in the shading correction pattern memory is displayed on 4 and 15. Then, three liquid crystal panels 13, 14, 1
The composite display of the pattern displayed above 5 is the second one.
As shown in FIG. d, since the color is black, light is blocked, and shading correction can be performed in accordance with the shape of the pattern.

Next, a white document serving as a reference is read and scanned, and the shading correction control section 24 performs the following steps.
The video signal output from the CCD 11 is compared with a preset white level reference to correct the shading correction pattern and store it in the shading correction pattern memory 23. Then, based on the shading correction pattern newly stored in the shading correction pattern memory 23, the shading correction pattern is displayed on the liquid crystal panels 13, 14, 15, and correction is made in the shading correction control section 24. By repeating such operations several times, an optimal shading correction pattern can be obtained.

Next, the filter function will be explained. The filter signal generation circuit 22 generates a 2-bit filter signal. For example, “00” is the red filter, “01”
is the green filter, “10” is the blue filter, “11” is the
Set to correspond to OFF.

In addition, the selectors 19, 20, and 21 respond to "00", "01", and "10", respectively, and cause the corresponding liquid crystal activation circuits 16, 17, and 18 to switch the entire surface of the liquid crystal panel.
A filter control signal is sent to turn ON (color display), and in other cases, the pattern data read from the shading correction pattern memory 23 is sent to the corresponding liquid crystal drive circuit to display the shading correction pattern in color.

As an example, when a 2-bit filter signal "00" is generated from the filter signal generation circuit 22, only the selector 19 among the three selectors 19, 20, and 21 sends a filter control signal to the liquid crystal drive circuit 16. Then, the red liquid crystal panel 13 displays the entire red color. At this time, the remaining selectors 20, 2
1 selects the output of the shading correction pattern memory 23 and causes the corresponding two liquid crystal panels to display the shading correction pattern. This example corresponds to FIG. 2a and shows the case where it functions as a red filter.

Similarly, when the filter signal is "01", it functions as a green filter corresponding to FIG. 2b,
When the filter signal is "10", it corresponds to FIG. 2c and functions as a blue filter. These “00”,
By generating filter signals of "01" and "10" at regular intervals, a video signal separated into three colors can be obtained. Incidentally, when the filter signal is "11", it corresponds to FIG. 2d, but it does not function as a filter, but is used as a shading correction function when reading a monochrome image.

〔Effect of the invention〕

According to the present invention, since the two functions of shading correction and color filter can be performed with only three color liquid crystal panels, it is possible to reduce the size and weight of the device and the cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a diagram explaining the operation of the present invention, FIG. 3 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 4 is a diagram of a conventional shading correction mechanism.
FIG. 5 is a diagram of a conventional filter mechanism. In Figure 1, 1: CCD, 2: lens, 3: red liquid crystal panel, 4: green liquid crystal panel, 5: blue liquid crystal panel.

Claims (1)

[Claims] 1. In an image input device that collects light emitted from a light source and reflected by the surface of a document using a lens, and forms an image on an image sensor to obtain a video signal, in front of the lens there is provided a red color, 3 consisting of green and blue
When three color liquid crystal panels are provided and the three color liquid crystal panels are used only for shading correction, the same shading correction pattern is displayed on the three color liquid crystal panels, and the three color liquid crystal panels are When used as a filter, one color liquid crystal panel displays color on its entire surface, the remaining two display a shading correction pattern, and the three color liquid crystal panels have a shading correction function and a filter function. An image input device characterized by the following features: