JPS6130865A - Color document reading device - Google Patents

Abstract

PURPOSE:To attain always white balance automatically by providing a white balance reference reflecting member at the outside of the effective read range of an original within a lighting range of an original platen and using the reflected light from the reflecting member to adjust an output level of each spectrum color. CONSTITUTION:The white balance reference reflecting plate 10 is provided at a place other than the original effective reading range 1a on the original platen 1. In scanning the original, the reference reflecting plate 10 is scanned. The scanned reflected light is separated into plural colors by a spectrum means 8. The separated light is converted into an electric signal by CCD9a, 9b, 9c. In scanning the reference reflected plate 10, the output of each color is compared with a reference input voltage Vr and kept to a prescribed level. Thus, the white balance is taken automatically at each scanning. Further, the white balance is taken accurately even for the original with a few white levels.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a color document reading device for an image processing device such as a copying machine, a printer, or a facsimile machine 11.

Conventional technology A COD that spectrally illuminates illumination light for a manuscript into at least two colors, for example, three colors of red, green, and converts each spectral information into an electrical signal.
A color document reading device having a reading means such as the above is well known.

The quality of color reproducibility of a color original is determined by the reproducibility of a white background. Therefore, the color reproducibility is improved by photoelectrically converting the light separated into three colors by a COD, which is a reading means, for each spectral color, and making the output of each COD equal in the standard white color. In this case, manual adjustment is required.

However, since the spectral distribution at the time when the white balance is achieved with the adjustment 'kL' is not always fixed, there is a problem in that the white balance is disrupted every time the spectral distribution of the light source changes.

OBJECTS It is an object of the present invention to solve the above-mentioned problems and provide a color document reading device that can always automatically maintain white balance.

Configuration In order to achieve the above object, the present invention provides a reference reflecting member for white balance at a location within the illumination range but outside the effective reading range of the document, and always performs color separation after color separation by light reflected from the reference reflecting member for white balance. The present invention is characterized in that the output level of the electric circuit for each spectral color is corrected based on the electric output of each spectral information.

The present invention will be specifically explained below based on embodiments.

In FIG. 1, a document 2 on a document table 1 is illuminated by a light source 3, for example a fluorescent light. The reflected light from the original enters the lens 7 via the mirror 4.5.6, and the imaged light emitted from the lens 7 is color separated by a spectroscopic means 8, for example, a guichroic prism, and is divided into, for example, staff and blue spectra. As the reading unit 9, for example, OCD R9a of the reading means for red, C0D() 9b of the reading means for line, OC of the reading means for blue.
The images are formed on D B 9C, respectively.

The spectroscopic means 8 and the reading section 9 constitute a reading means.

As shown in FIG. 2, the document table l is provided with a white balance reference reflector lO within the exposure range of the light source 3 and outside the effective reading range 1a of the document. The reference reflector 10 has a white reference color.

The original and the reference reflector 10 are scanned and exposed by scanning and exposing the light source 3 and the mirror 4 at a speed V and the mirrors 5 and 6 at a speed -, and the respective optical information is read by the reading means 9.

Instead of the example shown in the figure, a structure may be adopted in which the light source 3 exposes the entire surface of the original and the reference reflector 10, and the reading means 9 and the spectroscopic means 8 move in scanning.

In FIG. 3, the photoelectrically converted electrical signal from the COD R9a is amplified by the AMPR and input to the variable circuit R. The photoelectrically converted electrical signal from the ClCD G 9b is amplified by the AMPG and input to the variable circuit G. O
The photoelectrically converted electrical signal from the OD B 9c is amplified by the -■B and input to the variable circuit B.

The output electrical signals of each reading means 9a, 9b, 9c are as shown in FIG. 4, for example. COD R9α, 0O
Both the DG 9b and the OOD B 9c read the reflected light from the reference reflector 10 when reading each line of the original, and then read the image of the original. (7) Therefore, regardless of whether there is a line without a white background or a line with a white background, the reference white area is always read as the reflected light from the reference reflector 10. Therefore, this reference reflector 10
White balance can be maintained if the level of each spectral color information is kept constant when the white light is reflected light.

For this purpose, the S/H timing shown by the pulse signal in FIG. 4 is set within the time when the light from the reference reflector IO is being read.1. , hold the output of variable circuit R1 variable circuit 01 variable circuit B when indicated by all S/H timing pulses] 7. The difference from the reference input voltage Vr is calculated for each error M! , that is, in error AMPR, error AMPG, error AMPB, calculations are made for each spectral color (7. Variable circuit R1 variable circuit G1 variable circuit B corrects the output of each spectral color to a constant level. Therefore, the output of each spectral color is The quantized output from the A/D converter, ie, A, /DR, A/D (1, A/DB) becomes image information with white balance maintained.

When the next line comes at the S/H timing, the output of each spectral color is corrected L by the next pulse, and the white balance is automatically adjusted for each line based on the reflected light from the reference reflector.

The reference human power Vr is a common voltage for each spectral color, and the signal level of the white portion is equal.

FIG. 5 is a circuit diagram showing another embodiment of the present invention. Fifth
In the figure, the errors N8 and S/4 (peak values for each line of the reading scan without using timing, that is, the peak values of the output of the circuit for each spectral color based on the information of the white light from the reference reflector) are shown. Circuit R, peak circuit G1 is held in peak circuit B, and is inputted to the reference input voltage Vr width converter at its peak value.In other words, when the peak value of peak circuit R is reached, Vr R cancer width Φ Then, when the peak value of the peak circuit G is reached, Vr G becomes A7.
When 'DG is the peak value of the peak circuit B, VrB is input to VDB.

As a result, if the reference reflector is arranged, white balance can always be achieved based on information from the reference reflector.

Effects According to the present invention, the output of each spectral color can be normalized based on the reflected light of the reference reflector, and the white balance can always be automatically maintained even if the original has few white parts, such as a strong color photograph. It became possible to take.

Since a normal white balance can always be obtained, image signals with good color reproducibility can now be obtained even if the light intensity of the light source changes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an optical system of a reading device according to the present invention,
Figure 2 is a bottom view of the document table, Figure 3 is a circuit diagram of the electrical system, Figure 4 is a schematic diagram of changes in image signals during scanning, and Figure 5 is a circuit diagram of the electrical system of a modified example. be.

Claims (4)

[Claims] (1) Image formation by an imaging optical system that includes a document placement table on which a document is placed, a light source that illuminates the document on the document placement table, and a lens that forms an image of light reflected from the document. In a color document reading device, a white balance reference is provided at a location within the illumination range of the document mounting table and outside the effective reading range of the document. A reflecting member is provided, and the output level of the electric circuit for each spectral color is corrected based on the output from the spectral information reading means from the reflected light from the reference reflecting member for white balance. Color original reading device. (2) A variable amplifier is connected to each spectral color circuit as a variable circuit for correcting the output from the reading means based on the reflected light from the white balance reference reflecting member to a reference level. A color document reading device according to scope 1. (3) An A/D converter with a variable reference voltage is connected to each spectral color circuit as a variable circuit that corrects the output from the reading means based on the light reflected from the white balance reference reflecting member to a reference level. A color document reading device according to claim 1, characterized in that: (4) A ladder network type attenuator is connected to each spectral color circuit as a variable circuit for correcting the output from the reading means based on the light reflected from the white balance reference reflecting member to a reference level. A color document reading device according to claim 1.