JPS614359A - Picture reader - Google Patents

Abstract

PURPOSE:To maximize the light use rate in case of read of color pictures to maximize the S/N of an image sensor and to read respective color signals of red, green, and blue approximately faithfully by matching the spectral characteristic of an illuminating light source, that of the image sensor, and that of color separating filters for separation of red, green, and blue to one another when color pictures are read in a high speed. CONSTITUTION:An optical system is constituted as shown in the figure, and the spectral sensitivity characteristic of an image sensor 4 is set as indicated in a figure A, and color separating filters 41 which are mosaicked and arranged to obtain color separation signals in sequence of red, green, and blue points and have the spectral characteristic indicated in a figure B are arranged on the aperture surface of the image sensor 4. A blue white fluorescent tube 7 is used as the light source. If the color picture is read by this optical system, approximately balanced components are obtained when outputs of a white screen corresponding to individual red, green, and blue picture elements of color separating filters on the image sensor 4 are seen.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image reading device that can efficiently separate color signals during color imaging.

Conventional configurations and their problems Image reading devices have changed with the development of solid-state image sensors.
Efforts are being made to increase speed, resolution, functionality, and economy. Recently, efforts have been made to improve the performance of color systems for solid-state imaging devices and single-chip color imaging devices, including the development of color imaging devices for televisions. The first fundamental problem to be solved in improving these performances is the need to improve the efficiency of use of imaging light. In conventional color imaging devices, the basic method is to read the color of each pixel on a solid-state image sensor point-by-point using a color separation filter of red (uniform, green ((, 1), blue (B)). In order to increase the luminance signal component by improving the utilization efficiency of the red pass filter or the blue pass filter, a method has been proposed in which a complementary color filter is used as at least one of the red pass filter and the blue pass filter (for example, Japanese Patent Laid-Open No. 57-26978 On the other hand, as a method for reading color calligraphy using a single linear image sensor, for example, OG D (Charg
eCoupledDevice) A configuration is possible in which point-sequential color coding is applied to a linear image sensor in the form of a mosaic of red, green, and blue color separation filters on-chip. FIG. 1 is a diagram schematically showing a conventional example of a cyan stain optical system for reading an original using such a method. The optical system according to this figure uses a white light source (
It has a configuration in which it is illuminated by a fluorescent tube 2 and read by a linear image sensor 4 through an imaging lens 3, and is used in facsimiles. Note that the reference numeral 30 in the figure is a slit. In such an optical system, if the color separation filter 41 formed on the image sensor 4 by an on-chip method is a three primary color filter of red, green, and blue, as shown in FIG. Correction processing becomes easier. However, as shown in FIG. 2, the spectral sensitivity of solid-state image sensors generally decreases in the order of red, green, and blue wavelengths, making it difficult to maintain white balance. If the spectral transmittance of the color filter is controlled, the amount of light used will be extremely reduced (about 11D) compared to when reading white. This is because, in addition to the spectral sensitivity of the image sensor 4 as described above, the spectral intensity distribution of the white fluorescent tube is high in red and green and low in blue, as shown in Figure 3. This is because you will have to suppress the color and green. In view of this situation, a measure is taken to improve the light utilization efficiency by using complementary color filters as described above, but Fig. 4 shows a design example when cyan (Cy) is used as the complementary color filter. be.

However, according to such a composition, red.

Signal processing to separate the green and blue color components is required, which complicates the circuit system, and also makes it difficult to finely adjust the color tone, resulting in color mixing. and,
These problems arise from the fact that conventional imaging devices are designed primarily for objects illuminated by natural light, or so-called "daylight" light sources.
It also originates from the idea of configuring an optical system based on the spectral sensitivity characteristics of the sensor.

Purpose of the Invention The present invention has been made in view of these conventional problems, and its purpose is to enable high-speed and clear separation of color signals without complicating the circuit system for signal processing. It is an object of the present invention to provide a color image reading device.

Structure of the Invention In order to achieve the above object, the present invention provides a color imaging device with a solid-state image sensor having a spectral sensitivity that is lower in the order of red, green, and blue wavelength ranges, and a solid-state image sensor that has spectral sensitivities that are lower in the order of wavelength ranges of red, green, and blue; By combining these solid-state image sensors, the blue-white fluorescent tube, and a filter that can separate the three colors of red, green, and blue, , the gist is to balance the output of each cell when reading a white original. The present invention has achieved this aspect by incorporating a conventional color camera that aims to take pictures of scenes under natural light, and a built-in component that serves as a light source like a facsimile machine to read the original. It is based on the idea that completely different ideas can be established depending on the situation.

Description of examples An embodiment of the present invention will be described below.

5 and 6 show the spectral transmittance characteristics (hereinafter simply referred to as spectral characteristics) of a color separation filter used in a color image reading device according to an embodiment of the present invention, and the spectral characteristics of a blue-white fluorescent tube serving as a light source. FIG. 3 is a graph diagram showing intensity characteristics (hereinafter simply referred to as spectral characteristics). That is, in the present invention,
An optical system having the same basic configuration as shown in FIG. 1 is made, and the spectral sensitivity characteristics (hereinafter simply referred to as spectral characteristics) of the image sensor 4 of this optical system are set as shown in FIG. Red and green on the aperture surface of sensor 4.

Color separation filters 41 are arranged in a mosaic pattern so as to obtain sequential blue-black color separation signals, and have the spectral characteristics shown in FIG.

At this time, instead of the white fluorescent tube 2, a blue-white fluorescent tube 7 (see FIG. 9) having spectral characteristics as shown in FIG. 6 is used as a light source.

When a color image is read using such an optical system, the white screen corresponding to red, green, blue, and each pixel of the color separation filter 41 on the image sensor 4 as shown in FIG. Looking at the output, as shown in the figure, a nearly balanced and balanced component is obtained. In this example, (1) the spectral sensitivity of the image sensor 4 is set as shown in FIG. 2, and (2) the spectral sensitivity is set as shown in FIG. In addition, a color separation filter 41 having spectral (transmittance) characteristics as shown in FIG. 6 which takes into account the white balance is used. The object of the invention is achieved by using the fluorescent lamp 7, but in addition to this embodiment, an infrared cut filter having spectral characteristics as shown in FIG. 8 is used as the color separation filter. When used in combination with 41, the white balance can be further corrected.

In the color separation filter 41 shown in FIG. 7a, the pixel aperture rows 411, 412, 413 . - Photoelectric conversion output 5(j) (cor 1.2, 3°...) corresponding to...
・) indicates the maximum value relative to the reference white screen. In this embodiment, as shown in FIG. )
The amount of light is designed so that the signal component ratio (that is, the S/N ratio) is maximized with respect to the noise component of the image sensor 41.
1. In the above embodiment, the first
As shown in the figure, a lens reduction type optical system is configured to read a color image, but the present invention is not limited to this, and other types of optical systems may be used. FIG. 9 is a diagram showing a second embodiment of the present invention in which a 1-magnification imaging type optical system is created using a large-sized image sensor.

In this embodiment, reference numeral 5 is a lens array that forms an erect, equal-magnification image. For this lens array 5, a distributed refractive index type Ronde lens array, a flat microlens array, or a spherical microlens array can all be used as appropriate. The rest of the configuration is the same as that of the first embodiment. Illumination light is emitted onto the original 1 from a light source consisting of a blue-white fluorescent tube 7, and the reflected light is focused by a lens array 5 and then passed through a slit. 30, and the image sensor 4 performs photoelectric conversion. The image sensor 4 has aperture rows 411, 412, . . . with a color filter arrangement as shown in FIG.
····have. 3 in this opening row 411 etc.
The mosaic pattern of the color separation filter 41 is not limited to the repeating pattern of red, green, and blue as shown in FIG. The density of the rod (in Figure 9, P
2-2P1). Furthermore, instead of arranging the three-color separation filters in a mosaic pattern as shown in FIGS. 7a and 9, it is also possible to use other arrangement configurations. FIG. 10 is a diagram showing a third embodiment of the present invention in which the structure of the filter has been changed. In this embodiment, the filter 6 comprises a shaft portion 64 and a disk portion 66 extending radially outward from the shaft portion 64, the disk portion 65 matching the optical path of the image reading device, and The filter 6 is arranged to rotate around the rotation center axis 0. A dielectric multilayer film 6o is formed on the back surface of the disc portion 66 of the filter 6.
o As shown in the figure, fan-shaped color separation filter regions 61, 62, and 63 having predetermined spectral characteristics are formed as necessary. Among these color separation filter areas, the area 61 is divided into red, the area 62 is green, and the area 63 is blue. 3 color separation filter area 61,
62 and 63 are sequentially inserted into the path of the optical system, and are read out sequentially.

In this third embodiment, the optical system for image reading includes a rotating cylindrical body 1° on which the original 1 is provided, a blue-white fluorescent tube 7 that irradiates light onto the surface of the original 1, and a light that passes through a filter 6. The image sensor 4 includes an imaging lens 3 and an image sensor 4, which condense reflected light from the original document 1. The first side of the document is illuminated by a blue-white fluorescent tube 7, which is a light source, and the optical system constitutes a scanner to read the image information, which is almost the same as the conventional monochrome image reading optical system. 3
In this embodiment, since the optical system is for reading color image information, the movement of the rotary cylinder 10 that holds and fixes the color original 1 is controlled to control the three-color field filter area 61 of red, green, and blue. 62 and 63 to sequentially read image signals.

Effect of the invention 1 The sea urchin described above and the present invention
``1ba・f'' - In high-speed image reading, the spectral characteristics of the illumination light source and the spectral characteristics of the image sensor, as well as red, green,
By matching the spectral characteristics of each color separation filter for blue, it is possible to maximize the light utilization efficiency when reading color images, and to make the S/N ratio in the image sensor extremely thick. Since each blue color signal can be read almost faithfully, there is no need to use a complicated color signal processing circuit, and clear color image information can be obtained with a simple configuration.

[Brief explanation of drawings]

Fig. 1 shows a schematic configuration of a general color image information reading device using a white light source and an image sensor with a three-color separation filter on-chip, and Fig. 1a shows the configuration of an optical system. The figure shows the configuration of the color separation filter.
The figure shows the spectral characteristics of an image sensor used in an image reading device according to an embodiment of the present invention, FIG. 3 shows the spectral characteristics of a white light source used in a conventional image information reading device, and FIG. 4 shows the spectral characteristics of a white light source used in a conventional image information reading device. A diagram showing the spectral characteristics of a complementary color filter used to improve light usage efficiency in an image information reading device,
Figure 6 is a diagram showing the spectral characteristics of the color separation filter, Figure 6 is a diagram showing the spectral characteristics of a blue-white envelope source, and Figures 7a and b are diagrams each showing the configuration of the color separation filter and its color separation filter. A diagram showing the light amount conversion output corresponding to the pixel aperture row,
FIG. 8 is a diagram showing the spectral characteristics of an infrared cut filter that can be used in combination with a color separation filter, and FIGS. 9a and 9b are a schematic configuration diagram and color separation diagram of an image reading device according to a second embodiment of the present invention, respectively. FIGS. 10a and 10b are diagrams illustrating the configuration of a filter, and FIGS. 10a and 10b are respectively a schematic configuration diagram of an image reading apparatus and a configuration of a color separation filter according to a third embodiment of the present invention. 1... Manuscript, 2... White fluorescent tube, 3.
...Imaging lens, 4...Image sensor, 5
... Lens row, 6 ... Filter, 7.
... Blue-white fluorescent tube, 41 ... Color separation filter, 60 ... Dielectric multilayer film, 61°62.63
...Color separation filter area. Name of agent: Patent attorney Toshi Nakao, male and 1 other person
Zusui Momo Teisezu Momo distorted pseudo-scream a) Taste 4th picture 7k,
(nrnn Figure 5 1%) Uno Shushi &, <
nrnr Ward Sakai ν Elementary School Figure 7f 2345678 1

Claims (3)

[Claims] (1) A light source that illuminates the document surface, an imaging lens that collects light reflected from the document surface, a three-color separation filter that separates light from the document into red, green, and blue, and an image sensor. The image sensor is a solid-state image sensor whose spectral sensitivity decreases in the order of red, green, and blue wavelength regions, and the light source includes a blue-white light emitting device whose spectral intensity decreases in the order of blue, green, and red wavelength regions. An image reading device characterized by using a human body. (2) The image reading device according to claim 1, wherein the three-color separation filter has color elements arranged in a mosaic pattern corresponding to each pixel of the solid-state image sensor. (3) As a three-color separation filter, a filter is used in which a disk-shaped body rotatably mounted around a central axis of rotation is provided with color filter areas divided at predetermined angular intervals in the rotation direction, and the color filter Claim 1, wherein portions of the regions are arranged to cross the optical path, and by rotating the three-color separation filter, the color filter regions can be successively inserted into the optical path. The image reading device described.