JP2002016760A - Original reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an original reader that can reduce a read error resulting from reading a light of a band deviated from a wavelength to be read so as to enhance the color reproducibility. SOLUTION: In the original reader that reads an image of an original by receiving a light reflected in the original at red light receiving, green light receiving and blue light receiving elements 15R, 15G and 15B, spectral members 16, 13 having a prism function are placed on an incident optical path of the light receiving elements 15, the wavelengths of the light transmitted through the spectral members 16, 13 are separated and the light receiving elements 15R, 15G and 15B are placed at respectively corresponding wavelength receiving areas. Thus, in the case of reading a color original, since the light transmitted through the spectral members 16, 13 is separated into each wavelength by being refracted by a different angle from each wavelength and the light with the corresponding wavelength among the separated lights is made incident on the light receiving elements 15R, 15G and 15B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus that irradiates a document with light and receives reflected light from the document to read an image on the document.

[0002]

2. Description of the Related Art A document reading apparatus has a light source and a light receiving element, irradiates a document with light emitted from the light source, guides light reflected from the document to a light receiving section, and forms an image based on an output signal of the light receiving section. It is configured to read. Examples of such a document reading device include a reading unit of a digital copying machine and a scanner as an image input device of a personal computer. In these devices, for example, a fluorescent lamp is used as a light source, and a line sensor such as a CCD is used as a light receiving unit.

A document reading apparatus capable of reading a color image includes a red light, a green light,
Reading blue light respectively. As an example of a technique conventionally used for reading each color, there is a method of limiting a wavelength of light reaching the light receiving element to a desired range by covering the light receiving element with a filter. The filter used in such a method is capable of transmitting only light having a wavelength within a certain range,
The range of the wavelength of light that can be transmitted is adjusted by the thickness of the filter.

Here, when an image read by a document reading apparatus is printed out or output to a display, the color of the document and the color of the obtained image often differ slightly. The degree to which the formed color approximates the color of the original document is called color reproducibility. If the color reproducibility deteriorates, it becomes a serious defect in image quality.

There are at least two possible causes for the deterioration of color reproducibility. First, at the time of input, that is, when reading each of red light, green light, and blue light, light in a band shifted from the wavelength to be read is read.

For example, if there is an error in the film thickness of the filter, the wavelength of light passing through the filter and reaching the light receiving element will be different. In this case, the read color is different from the intended color, but when reproducing the image based on the obtained data, it is assumed that the intended color has been read. Therefore, the read color is replaced with another color and reproduced. As a result, the reproduced image is different from the original.

The second cause of the deterioration of color reproducibility is that at the time of output,
In other words, when printing out or outputting to a display,
That is, there is an instrumental difference in the output characteristics of how the given image data is reproduced.

Conventionally, color correction by digital data calculation, such as the technique described in Japanese Patent Application Laid-Open No. Hei 5-36995, has been performed for the error caused by the first cause. This conventional color correction method will be described with reference to FIGS.

FIG. 4 is a graph showing wavelength-relative sensitivity curves of red light R, green light G, and blue light B of the original reading apparatus. The spectral sensitivities of R, G, and B of the original reading device are slightly different from the theoretical values that should be originally output. For example, as shown in FIG. And the sensitivity distribution includes an extra area indicated by oblique lines with respect to the theoretical sensitivity distribution. The actual B sensitivity distribution is corrected by calculation using the other two G and R read values.

For example, assuming that a region corresponding to 10% of G and 5% of R is extra, B 'obtained by correcting B is B' =-0.05R-0.1G + 1.15B. Similarly, R ′ and G ′ are as follows: R ′ = 1.15R−0.1G−0.05B G ′ = − 0.05R + 1.1G−0.05B Therefore,

(Equation 1) Is derived. Thus, for example, conversion of image data obtained by reading various patches is as follows.

[0011]

[Table 1] Here, assuming an 8-bit resolution, the full scale is 2
55.

Here, achromatic colors include:

(Equation 2) Is used so that the value does not change.

Further, in order to increase the saturation of the copy image as compared with the original, the contents of the matrix may be changed.

[0014]

In the above-described conventional color correction based on digital data calculation, one type of matrix is generally used over the entire wavelength range.
Since the matrix is determined so that the peak values of B, G, and R become appropriate values, the matrix is not optimal for wavelengths apart from the peak values of B, G, and R, but the matrix is not optimal. Since the data is simply calculated and converted, the improper correction is performed depending on the wavelength.

An object of the present invention is to reduce a reading error caused by reading light in a band shifted from a wavelength to be read and improve color reproducibility.

An object of the present invention is to provide a scanning
This is to irradiate light of a desired wavelength to the light receiving element of each color.

[0017]

According to a first aspect of the present invention, there is provided an original reading apparatus which receives reflected light from an original with light receiving elements for receiving red light, receiving green light, and receiving blue light. In the document reading apparatus for reading an image of the document, a spectral member having a prism function is arranged on an incident optical path of the light receiving element, and a wavelength of light transmitted through the spectral member is decomposed to receive the red light and the green light. The light receiving elements for receiving light and for receiving the blue light were arranged in corresponding wavelength light receiving regions.

Here, the prism function is a function of refracting incident light at different angles for each wavelength, splitting the light, and emitting the light. Therefore, when reading a color original,
Light transmitted through the light splitting member is refracted at different angles depending on each wavelength, and is separated and emitted for each wavelength. Light of a corresponding wavelength among the separated light enters each light receiving element.

According to a second aspect of the present invention, an image of a document is read by receiving reflected light from the document with light receiving elements for receiving red light, green light, and blue light. In the document reading apparatus, two glass plates are arranged in a non-parallel state on the incident optical path of the light receiving element, and the wavelength of light transmitted through the glass plates is resolved by changing the width of a gap between the glass plates. The light receiving elements for receiving the red light, for receiving the green light, and for receiving the blue light are arranged in the corresponding wavelength light receiving regions.

Therefore, when reading a color original, the light transmitted through the two glass plates is refracted at different angles depending on the wavelength, and is separated and emitted for each wavelength. Of the light, the light of the corresponding wavelength is incident.

According to a third aspect of the present invention, there is provided the document reading apparatus according to the second aspect, further comprising an adjusting mechanism for adjusting a width of a gap between the two glass plates.

Therefore, the refraction angle of the light of each wavelength can be adjusted. Since the refraction angle of the light of each wavelength can be adjusted, it is easy to align the position of each light receiving element with the position of the light of the corresponding wavelength.

According to a fourth aspect of the present invention, in the document reading apparatus according to the third aspect, the adjusting mechanism is screwed to one of the two glass plates and is connected to the other glass plate. Equipped with a screw with a tip contact.

Therefore, the width of the gap between the two glass plates can be adjusted by turning the screw and changing the length of the tip of the screw projecting from the glass plate to which the screw is screwed. With this simple mechanism, the adjusting mechanism of claim 3 can be realized.

According to a fifth aspect of the present invention, in the original reading apparatus according to the third aspect, the adjusting mechanism includes a piezoelectric element sandwiched between the two glass plates and the two glass plates. And a biasing member for biasing in the direction of approach.

Therefore, by changing the voltage applied to the piezoelectric element, the thickness of the piezoelectric element changes and the width of the gap between the two glass plates changes. Thereby, Claim 3
Can be realized as an automatic mechanism without manual operation.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 is a vertical sectional front view schematically showing the configuration of the document reading apparatus 1. As shown in FIG.

The document reading apparatus 1 includes a contact glass 2 on which a document (not shown) is placed, a pressing plate 3 for pressing the document placed on the contact glass 2 and bringing the document into close contact with the contact glass 2, a contact glass for the document. A first scanning unit 4 which is provided so as to be able to scan in the sub-scanning direction in parallel with the lower surface of the contact glass 2 and to move the first scanning unit 4 in the same direction as the first scanning unit 4 1 / speed
The second scanning unit 5 is provided so as to be able to scan at a speed of 2, a CCD 6 as a light receiving unit, and lenses 7 and 8 provided in front of the CCD 6 on an optical path from a document to the CCD 6. An operation panel (not shown) for receiving various operations is provided on an upper surface of the housing 1a of the document reading apparatus 1.

The first scanning section 4 has a light source 9 for irradiating the original with light, and a first mirror 10 for reflecting light reflected from the original toward the second scanning section 5. The second scanning unit 5
A second mirror 11 and a third mirror 12 are provided. These mirrors 11 and 12 reflect the light guided by the first mirror 10 so as to be turned back, and form lenses 7, 8 and C
Guide in the direction of CD6.

The lenses 7 and 8 include first to third mirrors 10 to 10
The reflected light from the document guided by 12 is imaged on the CCD 6. Then, an image signal is obtained by photoelectric conversion by the CCD 6.

FIG. 2 is a vertical sectional front view schematically showing the CCD 6 and members disposed in the vicinity thereof. CCD 6
Three light receiving elements 15 are housed in a box-shaped case 14 whose one surface is covered with a glass plate 13. Each light receiving element 15 is, in order from the top in FIG. 2, a light receiving element 15R for receiving red light, a light receiving element 15G for receiving green light, and a light receiving element 15B for receiving blue light.

In this embodiment, the glass plate 1 of the CCD 6
Immediately before 3, another glass plate 16 is provided.
Worm screws 17 are screwed into the four corners of the glass plate 16. The worm screw 17 penetrates through the glass plate 16 and has a tip in contact with the glass plate 13. This forms a gap 18 between the glass plate 13 and the glass plate 16, the width d of which can be adjusted by turning the worm screw 17. Here, the adjusting mechanism 19 is configured by screwing the worm screw 17 to the glass plate 16.

Further, in this embodiment, the width d of the gap 18 between the glass plate 13 and the glass plate 16 is adjusted to be narrow at the upper end in FIG. 2 and wide at the lower end. By doing so, the width d of the gap 18 has a certain inclination from the upper end to the lower end, and the combination of the glass plate 16 and the glass plate 13 functions as a prism as a spectral member. Therefore, when the white light emitted from the light source used in the color document reading apparatus passes through the glass plate 16 and the glass plate 13, the light of each color constituting the white light is refracted and emitted at different angles depending on the respective wavelengths, and is emitted. A continuous spectrum of colors appears as horizontal stripes.

The gradient of the width d of the gap 18 is set such that the red spectrum of the continuous spectrum irradiates the light receiving element 15R, the green spectrum irradiates the light receiving element 15G, and the blue spectrum irradiates the light receiving element 15B. If you adjust,
It is theoretically possible to perform color separation. However, since it is difficult to actually perform complete color separation only by this method, each light receiving element 15 is provided with a filter (not shown) that transmits light in a predetermined range of wavelength.

The adjusting mechanism 19 for adjusting the inclination of the width d of the gap 18 is not limited to the one using the worm screw 17 described above. FIG. 3 shows an example of the adjusting mechanism 19 which is an alternative to this.

A spring (not shown) is provided as an urging member for urging the glass plate 13 and the glass plate 16 in a direction approaching each other, and four corners between the glass plate 16 and the glass plate 13 are provided with piezoelectric members. The element 20 is sandwiched. Then, by applying a voltage from a power supply 21 to each electrode of these piezoelectric elements 20, the thickness of the piezoelectric elements 20 is changed and the gap 18 is changed.
Adjust the width d.

In such a configuration, to read an image of a document, the document is placed on the contact glass 2 and
It is pressed down by the pressing plate 3 and is brought into close contact with the contact glass 2. In this state, the first and second scanning units 4 and 5 are scanned. A light source 9 mounted on the first scanning unit 4 irradiates the document with light via the contact glass 2.

The light emitted from the light source 9 and reflected by the original is guided by the first to third mirrors 10 to 12 and forms an image on the CCD 6 by the lenses 7 and 8.

FIG. 4 is a graph showing the relationship between the wavelength of light received by the CCD 6 and the relative sensitivity. Without the effect of the glass plate 16 and the glass plate 13 functioning as a prism, the relationship shown in FIG. 4 is obtained only by the function of the filter provided in each light receiving element 15.

FIG. 5 shows the theoretical wavelength-relative sensitivity curve of blue light B and the wavelength-relative sensitivity curve of blue light B shown in FIG. Between the theoretical value and the value obtained based on the output of the light-receiving element 15 with a filter, there is an error only in the shaded region in the graph of FIG. This error is mitigated by the function of the prism performed by combining the glass plate 16 with the glass plate 13.

FIG. 6 shows a wavelength-relative transmittance curve of the CCD 6 and a wavelength-relative transmittance curve of color separation by the glass plates 16 and 13 together. The product of these two curves over the entire wavelength is the glass plate 1 shown in FIG.
6 is a wavelength-relative transmittance curve of the CCD 6 provided with 6. As described above, according to the present embodiment, a result close to the theoretical wavelength-relative sensitivity can be obtained, and the peak of B spectrum is shifted to the shorter wavelength side, and the G and R regions are further removed. Will be possible. Therefore, if the spectral transmittance can be freely adjusted, color correction can be freely and continuously performed at an arbitrary wavelength.

In this embodiment, the blue light B has been described for convenience, but the same applies to the green light G and the red light R.

In the present embodiment, the gap 18 is formed by using the glass plate 13 provided in the CCD 6, but in practice, another glass plate different from the glass plate 13 is provided. Then, the gap 18 may be formed between the glass plate and the glass plate 16.

Further, in this embodiment, the dispersing member having the prism function is constituted by two glass plates. However, in practice, a prism may be used as the dispersing member.

In this embodiment, RGB (R:
Although the conversion from red, G: green, B: blue) to RGB has been described, the present invention can be applied to the conversion from RGB to CYMYBk (C: cyan, Y: yellow, M: magenta, Bk: black).

[0046]

According to the first aspect of the present invention, when reading a color original, the reflected light from the original is decomposed for each wavelength by transmitting through the spectral member, and each of the light-receiving elements receives the reflected light. Since light of the corresponding wavelength is incident, data of a predetermined color can be obtained.
Color reproducibility can be improved.

According to the second aspect of the present invention, when reading a color original, the reflected light from the original is separated for each wavelength by transmitting through two glass plates, and each light receiving element has a light receiving element. Since light of the corresponding wavelengths is incident, data of a predetermined color can be obtained, and thereby color reproducibility can be improved.

According to a third aspect of the present invention, in the second aspect of the present invention, the refraction angle of the light of each wavelength can be adjusted, whereby the position of each light receiving element and the position of the light of the corresponding wavelength are adjusted. Because alignment can be performed easily,
The color reproducibility can be easily improved.

According to the fourth aspect of the present invention, the width of the gap between the two glass plates can be adjusted by turning the screw. With this simple mechanism,
The adjustment mechanism according to the third aspect of the invention can be easily realized.

According to a fifth aspect of the present invention, in the third aspect, the thickness of the piezoelectric element is changed by changing the voltage applied to the piezoelectric element, and the width of the gap between the two glass plates is changed. Can be. Thus, the adjusting mechanism according to the third aspect of the present invention can be realized as an automatic mechanism that does not require manual operation.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view schematically showing a configuration of a document reading apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional front view schematically showing an example of an adjusting mechanism.

FIG. 3 is a longitudinal sectional front view schematically showing another example of the adjusting mechanism.

FIG. 4 shows a red light R, a green light G, and a blue light B of a document reading apparatus.
4 is a graph showing a wavelength-relative sensitivity curve of FIG.

5 is a graph showing the theoretical wavelength-relative sensitivity curve of blue light B and the wavelength-relative sensitivity curve of blue light B shown in FIG. 4 together;

FIG. 6 is a graph showing a combination of a wavelength-relative transmittance curve of a CCD and a wavelength-relative transmittance curve of color separation between glass plates.

FIG. 7 is a graph showing a wavelength-relative transmittance curve of a CCD provided with a glass plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Document reading apparatus 13, 16 Dispersion member 13 Glass plate 15 Light receiving element 16 Glass plate 17 Screw 18 Gap 19 Adjustment mechanism 20 Piezoelectric element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) H04N 1/028 H04N 1/04 DF term (reference) 2H108 AA01 BB01 CA01 CB01 JA00 5B047 AA01 AB04 BB02 BC04 CA17 CB05 5C051 AA01 BA03 DA03 DB01 DB22 DB24 DE19 EA01 5C072 AA01 BA19 DA10 DA21 EA05 QA03 UA18

Claims (5)

[Claims] 1. An original reading apparatus for reading an image of an original by receiving reflected light from the original with respective light receiving elements for receiving red light, receiving green light, and receiving blue light. Arranging a spectral member having a prism function on the optical path and decomposing the wavelength of light transmitted through the spectral member,
An original reading apparatus, wherein the light receiving elements for receiving the red light, the green light, and the blue light are arranged in corresponding wavelength light receiving areas. 2. A document reading apparatus for reading an image of a document by receiving reflected light from the document with respective light receiving elements for receiving red light, receiving green light, and receiving blue light, wherein the light receiving element receives By disposing the two glass plates on the optical path in a non-parallel state and changing the width of the gap between the glass plates, the wavelength of light transmitted through the glass plates is decomposed,
An original reading apparatus, wherein the light receiving elements for receiving the red light, the green light, and the blue light are arranged in corresponding wavelength light receiving areas. 3. The document reading apparatus according to claim 2, further comprising an adjusting mechanism for adjusting a width of a gap between the two glass plates. 4. The original according to claim 3, wherein the adjusting mechanism includes a screw screwed into one of the two glass plates and having a tip contacting the other glass plate. Reader. 5. The adjusting mechanism includes a piezoelectric element sandwiched between the two glass plates, and a biasing member for biasing the two glass plates in a direction to approach each other. The document reading device according to claim 3.