JPH0777412B2 - Color original reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color original reading device, and more particularly, to a color original capable of optimizing white balance between respective color pixel signals of three originals read from a color original. The present invention relates to a reading device.

[Prior Art] R, G, B pixel signals of the three primary colors R, G, B are serially output, that is, serially output in a color original reading device using a color image sensor in which the same arrangement is repeated. It has been proposed to obtain a desired color pixel signal by sample-holding each color pixel signal of G, B, or by distributing each color by a multiplexer and amplifying each of these signals.

An example of such a color original reading device is shown in FIG.

Here, 10 is a document, 11 is a document table, 12 is a white lamp, 13 is a lens, 14 is a color image sensor, 15 is an amplifier, 16R,
16G, 16B sample hold, 17R, 17G, 17B amplifier, 18
R, 18G and 18B are A / D converters, and 19 is a timing control unit.

The operation of the color original reading device will be described with reference to the timing chart of FIG. 4. The optical image of the original 10 illuminated by the white lamp 12 is formed on the color image sensor 14 via the lens 13, It is converted into pixel signals for each of the three primary colors of R, G, and B.

The pixel signal output from the color image sensor 14 is synchronized with the signal φ11 from the timing control unit, and the amplifier 15
Via sample hold 16R, 16G, 16B
Color separation of the three primary colors is performed on R, G, and B.

The color-separated signals are controlled by the amplifiers 17R, 17 provided for each color so that the signals have proper input levels to the A / D converters 18R, 18G, 18B.
Amplified by G, 17B.

The sample hold and A / D conversion are performed by the signals φ _12R , φ _12G , φ _12B and φ _13R , φ _13G , φ _13B from the timing section 19.

By the way, in the conventional color original reading apparatus as described above, the correction of the decrease in the light amount due to the temporal change of the white lamp is not taken into consideration, and the dynamic range is decreased.

In addition, the method of controlling the driving voltage of the lamp against the decrease of the light amount of the white lamp due to the change with time has a problem that the color temperature of the lamp changes depending on the driving voltage and thus cannot be used easily. It was

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to read a color original document which can obtain good digital color pixel signals of a plurality of colors from which the level deviation between the color pixel signals is removed with a simple configuration. To provide a device.

[Means for Solving Problems] In order to achieve such an object, the present invention provides a color image sensor that serially outputs analog color pixel signals of a plurality of colors, and a serial output from the color image sensor. Multiplying D / that amplifies analog color pixel signals of multiple colors
An A converter, an A / D converter that converts analog color pixel signals of a plurality of colors that are serially output from the multiplication D / A converter into a plurality of digital color pixel signals, and the white image of the white reference plate in the color image sensor. Setting to set a digital correction signal for each color for level deviation correction between color pixel signals based on digital color pixel signals of a plurality of colors that are serially output from the A / D converter when an image is formed Means for changing the amplification factor of each of the analog color pixel signals of a plurality of colors by the multiplying D / A converter according to the digital correction signal for each color set by the setting means. [Operation] In the present invention, analog color pixel signals of a plurality of colors that are serially output from the color image sensor are amplified by the multiplication D / A converter, and the multiplication D / A is generated. The analog color pixel signals of multiple colors output serially from the converter are converted to digital color pixel signals of multiple colors by the A / D converter, and when the optical image of the white reference plate is formed on the color image sensor, A digital correction signal for level deviation correction between color pixel signals is set for each color by the setting means based on digital color pixel signals of a plurality of colors that are serially output from the A / D converter. The amplification means changes the respective amplification factors of the analog color pixel signals of a plurality of colors by the multiplying D / A converter according to the correction signal.

EXAMPLES The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation.

In FIG. 1, 20 is a white reference plate, 21 is a document table, 22 is a white lamp for illuminating the white reference plate 20 or the document table 21. It leads to the color image sensor 24 via.

25 is a multiplication type D / A converter, which is supplied with the output V ₂₁ of the color image sensor 24. Reference numeral 26 is an A / D converter that converts the output V ₂₂ of the D / A converter 25 into a digital signal.

27R, 28G, 27 _B is a latch, 28 comparator 29 is a timing controller, compares the set value predetermined output of the A / D converter 26 by the comparator 28, the timing controller of the comparison result 29 Timing signal φ _23R , φ _23G , φ
Latch 27R by _23B, latching to 28G, 27 _B. These 27R,
The output of 27G, 27B is taken out by the timing signals φ _24R , φ _24G , φ _24B from the timing control unit 29 and the D / A converter
25, and the amplification factor is set appropriately for each of R, G, and B.

Next, the operation of the circuit shown in FIG. 1 will be described with reference to FIG.

The optical image of the white reference plate 20 illuminated by the white lamp 22 is formed on the color image sensor 24 via the lens 23.

At the timing of the drive signal φ ₂₁ output from the timing controller 29, the color image sensor 24 sequentially outputs the color pixel signal V ₂₁ for each of the three primary colors R, G, B. The color pixel signals V _21, the latch 27R, at 28G, 27 amplification factor in accordance with the value set in the _B, the amplified analog output V ₂₂ is obtained by the multiplication type D / A converter 25.

Here, first, the reference values are set in the latches 27R, 27G, and 27B so that the amplification factor of the multiplication D / A converter 25 becomes 1, and the signal V ₂₂ read from the white reference plate is A / D conversion timing. In synchronization with φ ₂₂ , the A / D converter 26 converts the digital value.

The digitally converted value is compared with the desired set value and the comparator 28.
And the digital data is sent to the latches 27R, 27G, 27B so that the output of the A / D converter 26 matches the set value.

This data is the latch timing signal _φ23R , _φ23G , _φ23B
Thus, the pixel signal data for R color is held in the latch 27R, the pixel signal data for G color is held in the latch 27G, and the pixel signal data for B color is held in the latch 27B.

Next, when reading a color original, drive signal φ ₂₁
When the signal V ₂₁ output from the color image sensor 24 is an R color pixel signal in synchronization with the
_24R becomes “1”, and the data held in the latch 27R is input to the multiplication D / A converter 25.

Therefore, the multiplication D / A converter 25 amplifies the signal V ₂₁ according to the value of the latch 27R. This amplified signal V ₂₂ is A / D converted by the A / D converter 26 in the next stage, and becomes a desired digital amount.

Even when the signal V ₂₁ is a G color pixel signal or a B color pixel signal, the amplification factor of the multiplication D / A converter 25 is changed by the respective data of the latches 27G and 27B in the same manner as above.
Make sure the value after / D conversion matches the setting value.

As described above, when the amplification factor for each color of each color pixel signal is determined using the white reference plate, when reading a color original, the color image sensor 24 uses, for example, the white lamp 22.
It is possible to easily correct the level deviation between the color pixel signals due to the variation in the sensitivity for each color due to the change of the light amount with time.

EFFECTS OF THE INVENTION As described above, according to the present invention, the levels of digital color pixel signals of a plurality of colors after A / D conversion are controlled according to the digital correction signal for level deviation correction between color pixel signals. Instead, since the levels of analog color pixel signals of a plurality of colors before A / D conversion are controlled, it is possible to obtain digital color pixel signals of a plurality of colors having a good dynamic range.

Further, according to the present invention, since the level control of the analog color pixel signals of the plurality of colors is performed using the multiplication type D / A converter, the digital correction signal for level deviation correction between the color pixel signals is converted into an analog format. There is an effect that the level control of the analog color pixel signals of a plurality of colors can be executed by the digital correction signal in the digital format without conversion.

[Brief description of drawings]

1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation of FIG. 1, FIG. 3 is a block diagram showing the configuration of a conventional reader, FIG. FIG. 4 is a time chart for explaining the operation of FIG. 10 …… Original, 11 …… Original plate, 12 …… White lamp, 13 …… Lens, 14 …… Color image sensor, 15 …… Amplifier, 16R, 16G, 16B …… Sample hold, 17R, 17G, 17B… … Amplifier, 18R, 18G, 18B …… A / D converter, 19 …… Timing control unit, 20 …… White reference plate, 21 …… Document table, 22 …… White lamp, 23 …… Lens, 24 …… Color Image sensor, 25 …… Multiplying D / A converter, 26 …… A / D converter, 27R, 27G, 27B …… Latch, 28 …… Comparator 29 …… Timing controller.

Claims (1)

[Claims] 1. A color image sensor that serially outputs analog color pixel signals of a plurality of colors, and a multiplication D / A converter that amplifies the analog color pixel signals of a plurality of colors that are serially output from the color image sensor. An A / D converter that converts analog color pixel signals of a plurality of colors serially output from the multiplying D / A converter into digital color pixel signals of a plurality of colors; and an optical image of a white reference plate on the color image sensor. When imaged, a setting means for setting, for each color, a digital correction signal for level deviation correction between color pixel signals based on digital color pixel signals of a plurality of colors that are serially output from the A / D converter, According to the digital correction signal for each color set by the setting means, the amplification factors of the analog color pixel signals of a plurality of colors by the multiplying D / A converter are changed. And a changing means for converting the color original into a color original reading apparatus.