JPH04196965A - Color image reader - Google Patents

Abstract

PURPOSE:To adjust the output signals from a photodetecting means having plural photodetectors by varying the lens aperture diameters of plural lens systems constituting an imaging means according to respective color light rays at the time of reading color images from each other, thereby constituting the above color image reader. CONSTITUTION:This image reader is so constituted that the aperture diameters of the plural lens systems 4a, 4b, 4c constituting the imaging means 4 vary from each other at the time of reading the color images 1. The lens systems 4a, 4b, 4c correspond successively to the lens systems for reading the color images based on the blue light (B), green light (G) and red light (R). The reader is so constituted that the lens aperture diameter of the lens system 4a imaging the color images based on the color light (blue light) on the short wavelength side of a low relative spectral sensitivity is larger than the lens aperture diameters of the lens system 4b and lens system 4c imaging the color images based on the color light (red light) on the long wavelength side of a relatively high spectral sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a color image reading device, and in particular, when reading a color image based on a plurality of colored lights, a plurality of lens systems with different lens apertures depending on each color light are used. The present invention relates to a color image reading device suitable for, for example, a color scanner, a color facsimile, etc., which reads color image information on a document surface with high precision by using an imaging means consisting of the following.

(Conventional Technique #) Conventionally, in many color image reading devices, a color image placed on the document surface is transferred to the surface of a line sensor (receiving means) such as a CCD via an imaging optical system (imaging means). An image is formed for each color of light. Then, using the output signal from the line sensor at this time, the color image is digitally read based on each color light.

FIG. 4 is a schematic diagram of the main parts of the optical system of this type of conventional color image reading device.

In the figure, reference numeral 43 denotes illumination means, which is comprised of a light source such as a halogen lamp or a full-light lamp.

Reference numeral 42 denotes a document glass plate, and 41 a color image, which is placed on the document glass plate 42 . 44 is an imaging means;
For example, it is made of a single focus lens array (trade name: SELFOC lens array), and forms a color image 41 at the same magnification on the surface of a light receiving means 45, which will be described later.

Reference numeral 45 denotes a light receiving means, which is composed of, for example, a line sensor or the like, and converts image information from the color image 41 into an electrical signal. For example, as shown in FIG. 5, the line sensor 45 includes one line of light-receiving elements set to detect light with spectral sensitivities corresponding to the three primary colors of R (red), G (green), and B (blue). It is constructed by arranging multiple pieces upside down. In the figure, color filters of R2O and H are deposited on the surfaces of the light receiving elements, respectively, so that images are read using three colored lights of R, G, and B.

In the color image reading device shown in FIG. 4, a color image 41 placed on a document glass 42 is illuminated by an illumination means 43, and the color image 41 is displayed at the same magnification on a line sensor 45 surface by a single focus lens array 44. The color image is read by forming an image.

(Problems to be Solved by the Invention) When a halogen lamp is used as illumination means in the color image reading device shown in FIG. 4, the spectral energy key distribution (spectral ratio) of the halogen lamp is as shown in FIG. It's full. The spectral characteristics of the color filters R1G and B deposited on the line sensor surface are approximately as shown in FIG.

Therefore, the relative spectral sensitivity (spectral distribution) for color image reading is determined by the spectral energy distribution of the light source 43, the spectral characteristics of the color filter, and the spectral characteristics of the single focus lens array and line sensor themselves. The relative spectral characteristics at this time are as shown in FIG. 8, for example.

As can be seen from the figure, the relative spectral distribution of colored light in the short wavelength region is small, that is, the reading sensitivity is low.

For this reason, there is a problem in that when a color image is read using the three color lights of R, G, and B, the output signals based on the respective color lights from the line sensor 45 vary due to the above-mentioned causes. For example, even when reading a white image, there is a problem in that the output signals based on the three color lights of R, G, and H are not uniform.

Therefore, in conventional color image reading devices, variations in the output signal from the line sensor are electrically amplified and adjusted by using an amplifier so that the pressure signal from the line sensor becomes uniform.

However, when the output signal from the line sensor is electrically amplified using an amplifier, noise is also amplified at the same time, making it difficult to read with high precision. Furthermore, there is also an operational problem in that the stability of the operation of the amplifier must be maintained well.

When reading a color image, the present invention utilizes an imaging means consisting of a plurality of lens systems whose lens apertures are set to differ according to the spectral characteristics of each color light. An object of the present invention is to provide a color image reading device which can read color images with high precision by reducing variations in color images.

(Means for Solving the Problems) A color image reading device of the present invention illuminates a color image placed on a surface of a document with an illumination means, and uses an imaging means to illuminate a color image placed on a surface of a document, and a light receiving means having a plurality of light receiving elements. In a color image reading device that forms an image on a surface and reads it based on a plurality of colored lights, the imaging means has a plurality of lens systems with different lens apertures depending on the colored light when reading the color image. It is characterized by

In particular, the present invention is characterized in that the lens apertures of the plurality of lens systems have a value that is inversely proportional to the output ratio from the corresponding light receiving element of the light receiving means when the luminous flux from the illuminating means is incident. It is said that

(Embodiment) FIG. 1(A) is a schematic diagram of a main part of an optical system of a first embodiment of a color image reading device of the present invention.

In the figure, reference numeral 3 denotes illumination means, which is comprised of a light source such as a halogen lamp or a fluorescent lamp.

Note that in this embodiment, a halogen lamp is used.

Reference numeral 2 denotes an original platen glass, and 1 denotes a color image (reflection type original), which is placed on the original platen glass 2. 4 is an imaging means, which is a three single focus lens array (product name: SELFOC lens array) in which a plurality of three single focus lenses 4al, 4bl, and 4cl are arranged one-dimensionally in the direction perpendicular to the plane of the paper (
(hereinafter referred to as "lens system") 4a, 4b, and 4c. Three single focus lens arrays 4a, 4b.

One single focus lens 4a1°4b1.
One pixel of a color image is read using 4cl.

The image forming means 4 forms a color image 1 at the same magnification on the surface of a light receiving means 5, which will be described later.

In this embodiment, the lens apertures of the plurality of lens systems 4a, 4b, and 4c constituting the image forming means 4 are set to be different depending on the color light when reading the color image 1, as shown in FIG. 1(B). It is composed of

In FIG. 1B, lens systems 4a, 4b, and 4c correspond to lens systems for reading color images based on blue light (B), green light (G), and red light (R) in this order.

In this embodiment, the lens aperture of the lens system 4a that forms a color image based on short wavelength colored light (blue light) with low relative spectral sensitivity or long wavelength colored light (red light) with high relative spectral sensitivity The lens aperture is larger than the lens aperture of the lens system 4b and lens system 4C that form a color image based on .

Reference numeral 5 denotes a light receiving means, which consists of a plurality of line sensors 5a, 5b, and 5c such as CCDs, and lens systems 4a, 4b, and 5c, respectively.
Compatible with 4c. Moreover, the line sensors 5a, 5b,
On the 5c surface, B (blue), G (green), and R (red) having spectral characteristics similar to those shown in FIG. 7 are used as color separation means for reading a color image based on predetermined color light. A color filter (not shown) is provided by vapor deposition or the like. The illumination means 3, the imaging means 4, and the light receiving means 5 are connected to the reading means 101.
It consists of

In this embodiment, a color image 1 placed on a document platen glass 2 is illuminated by an illumination means 3, and a line sensor 5a, 5b provided with a predetermined color filter is used to illuminate the color image 1 through lenses i4a, 4b, 4c. , the image is formed at the same magnification on the Sc plane. And the line sensors 5a, 5b, 5
The color image 1 is digitally read out based on predetermined color light by c. Then, the document glass 2 is line-scanned in a direction parallel to the paper surface, or the reading means 101 is scanned in a line parallel to the paper surface, so that the color image 1 on the surface of the document glass 2 is scanned.
I'm reading the whole thing.

Generally, the amount of light incident on the line sensor (equivalent to the amount of light during reading, ie, the output signal from the line sensor) is influenced by the size of the lens aperture of the lens system that constitutes the reading optical system. For example, the amount of light incident on the line sensor I
, when the lens aperture of the lens system is d, and the angle of view is θ with respect to the lens aperture d, the amount of incident light I can be determined from the following equation.

■=02 ・d From this, when the imaging magnification of a color image based on each color light is set to be the same for each color light, by changing the value of the lens aperture d, the amount of light I incident on the line sensor, i.e. The output signal from the line sensor can be controlled arbitrarily.

In this embodiment, when the luminous flux from the illumination means 3 is directly incident on the surfaces of the plurality of line sensors 5a, 5b, 5C, or when a white image is targeted as a color image, the output from the line sensors 5a, 5b, 5c The value (output signal) is output differently for each color light because the spectral characteristics (spectral sensitivity) of the entire system differ depending on each color light, as described above.

Therefore, in this embodiment, the aperture ratio of the plurality of lens systems 4a, 4b, and 4c constituting the imaging means 4 is set to a value that is inversely proportional to the output ratio from the line sensors 5a, 5b, and 5c at this time. ing. Specifically, colored light on the short wavelength side (
The lens aperture of the lens system 4a that forms an image of blue (B) colored light) is dI, the lens aperture of the lens system 4b that forms an image of medium wavelength colored light (green (G) colored light) is d2, and the long wavelength colored light ( Let d3 be the lens aperture of the lens system 4c that forms an image of red (R) color light. Then, when the luminous flux from the illumination means 3 is directly incident on the line sensors 5a, 5b, 5c, or when a white image is targeted as a color image, the outputs SB, SG, SR from the line sensors 5a, 5b, 5c are output. For example, when the ratio of SB:SG:5R=0.7:1:2, the apertures d, d of each lens system 4a, 4b, 4c
2°d3 is set to be inversely proportional to these outputs SB, SG, and SR, that is, so that the relationship d::d2·d3=2:1:0.7 approximately holds true.

(Actually, the balance should be within ±30%.) In other words, the aperture ratio of the lens systems 4a, 4b, 4c is set to be inversely proportional to the output ratio of the line sensors 5a, 5b, 5c. are doing.

Accordingly, in this embodiment, when a white image is targeted as a color image, the line sensor 5a.

Ratio of outputs SB, SG, and SR from 5b and 5c, SB:S
G:5R=1:1:1.

In this way, in this embodiment, when reading a color image using predetermined colored light, the lens apertures of the lens systems 4a, 4b, and 4c constituting the imaging means 4 are adjusted as described above according to the spectral sensitivity of the entire system of the colored light. By appropriately varying the ratio, the output ratio from the line sensors 5a, 5b, and 5c can be easily controlled.

This allows highly accurate reading of color images based on multiple colored lights with little noise.

FIG. 2 is a schematic diagram of the main parts of the optical system of a second embodiment of the color image reading apparatus of the present invention. In this figure, the same elements as those shown in FIG. 1 are given the same reference numerals. In the figure, 7 is a folding mirror. Reference numeral 8 denotes a color separation prism as a color separation means, which is provided in the optical path between the document surface of the color image 1 and the light receiving means 5, and separates the light flux from the color image 1 into R (red) and G (green). , B (blue), and the separated light is guided to the imaging means 4.

In this embodiment, a color image 1 placed on a document platen glass 2 is illuminated by an illumination means 3, and a light beam from the color image 1 is reflected through a mirror 7 to a color separation prism 8.
After color separation into three color lights of red (R), green (G), and blue (B), lens systems 4a and 4b as image forming means 4 having different lens apertures depending on the read color light are used. ,
It is input to 4c.

The image forming means 4 forms a color image 1 based on each color light onto the line sensors 5a, 5b, 5c as a light receiving means 5, and the light receiving means 5 reads a color image 1 based on each color light. ing. Then, the color image 1 is scanned in a direction parallel to the paper surface together with the document table crow 2, that is, the color image is scanned by each line, and the entire color image 1 is read with high precision.

In this embodiment, a plurality of lens systems 4a constitute the imaging means 4 as in the first embodiment described above.

A plurality of line sensors 5a constituting the light receiving means 5 by appropriately setting the aperture ratio of 4b and 4c as described above,
The output signals from 5b and 5c are easily adjusted, thereby increasing the accuracy of reading a color image based on a plurality of colored lights.

FIG. 3 is a schematic diagram of the main parts of the optical system of a third embodiment of the color image reading apparatus of the present invention. In this figure, the same elements as those shown in FIG. 2 are given the same reference numerals.

This embodiment differs from the second embodiment shown in FIG. 2 above in that a phase grating 9 is used instead of the color separation prism 8 as the color separation means, and other aspects are the same.

That is, in this embodiment, the color image 1 placed on the surface of the glass platen 2 is illuminated by the illumination means 3, and the light beam from the color image 1 is returned via the mirror 7 to the phase grating 9.
It is input to. Then, by the phase grating 9, R, G, B
After color separation into three color lights, a lens system 4a as an imaging means 4 with different lens apertures depending on the read color light is used.
.

4b and 4c. The image forming means 4 forms a color image 1 based on each color light onto the surfaces of line sensors 5a, 5b, and 5c as the light receiving means 5. The color image 1 is read by the light receiving means 5 based on each color light.

In each of the above embodiments, color filters, color separation prisms, phase gratings, etc. are used as color separation means to perform R.
Although the color image was read by separating the light into multiple color lights such as (red), G (green), and B (blue), the color separation method is not limited to these. The present invention can be applied in the same manner as in the above-described embodiments even if other means are used as long as the members can be used.

Furthermore, in each of the embodiments, the color image reading device is constructed using a reflective original as the irradiated source H4 (color image), or the present invention is equally applicable even if the color image reading device is constructed using a transmissive original. can.

(Effects of the Invention) According to the present invention, as described above, by configuring a plurality of lens systems constituting the imaging means with different lens apertures according to each color light when reading a color image, a plurality of lens systems are configured to have different lens diameters. It is possible to easily adjust the output signal from a light receiving means having several light receiving elements. For example, in the case of a white image, the output signals from multiple light receiving elements can be roughly averaged. It is possible to achieve a color image reading device that can read images with high accuracy.

[Brief explanation of the drawing]

1(A), FIG. 2, and FIG. 3 respectively show the first color image reading apparatus of the present invention. Second. FIG. 1(B) is an explanatory diagram showing lens apertures of a plurality of lens systems constituting the imaging means shown in FIG. 1(A); The figure is a schematic diagram of the main parts of the optical system of a conventional color image reading device, Figure 5 is an explanatory diagram of the line sensor shown in Figure 4, Figure 6 is an explanatory diagram of the energy key distribution of the light source, and Figure 7 is a color FIG. 8 is an explanatory diagram of the spectral characteristics of the filter, and FIG. 8 is an explanatory diagram of the spectral characteristics of color image reading. In the figure, 1 is a color image, 2 is a document table glass, 3 is an illumination means, 4 is an imaging means, 4a, 4b, and 4c are lens systems (single focus lens array), and 4al. 4bl, 4cl are single focus lenses, 5 is a light receiving means, 5a,
sb, 5c are light receiving elements (line sensors), 7 is a folding mirror, 8 is a color separation prism, 9 is a phase grating, 101
is the reading means. Patent applicant: Canon Corporation Figure 1 (B) Figure 4 Figure 5 Figure 6 Wavelength (nm)

Claims (5)

[Claims] (1) A color image placed on the document surface is illuminated by an illumination means, and the color image is imaged by an imaging means on a light receiving means surface having a plurality of light receiving elements and read based on a plurality of colored lights. 1. A color image reading device, wherein the image forming means has a plurality of lens systems having different lens apertures depending on the color light used when reading a color image. (2) The color image reading device according to claim 1, wherein each of the plurality of lens systems comprises a single focus lens array. (3) Lens apertures of the plurality of lens systems have a value that is inversely proportional to the output ratio from the corresponding light-receiving element of the light-receiving means when the luminous flux from the illumination means is incident thereon. A color image reading device according to claim 1. (4) The color image reading device according to claim 1, further comprising color separation means for separating the light flux from the document surface into a plurality of colored lights between the document surface and the light receiving means. (5) The color image reading device according to claim 4, wherein the color separation means comprises a color filter, a color separation prism, or a phase grating.