JPH0440161A - Picture input device - Google Patents

Abstract

PURPOSE:To enlarge the dynamic range of an analog signal by reading a black reference data in a main scanning direction before inputting a picture, and calculating difference between the picture analog signal to be obtained from a line sensor and the prepared black reference analog signal when inputting the picture. CONSTITUTION:A black reference data storage part 5 is a general random access memory or the like and stores the black reference data before the operation of inputting the picture. In the case of the picture input operation, a black reference data h2 is read out from the black reference data storage part 5 synchronously with the sampling of an S/H circuit 2, converted from a digital signal to an analog signal by a D/A converter 6 and transmitted as a black reference analog signal h4 through a buffer amplifier 7 to a differential amplifier 3. Then, by subtracting a dark output in the main scanning direction, a picture analog signal a3 becomes a pure picture signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image input device used in image scanners, facsimiles, and the like.

[Conventional technology]

Conventional image input devices include a line sensor consisting of a CCD line sensor or a phototransistor array, a light source that illuminates the original, an optical lens that focuses an image of the original on the line sensor, and a relative movement between the original and the line sensor. It consists of a sub-scanning mechanism, and the image analog signal obtained from the line sensor is passed through a sample and hold circuit (hereinafter referred to as S/
The signal passes through an amplifier circuit (referred to as H circuit) and an amplifier circuit, and is further converted into a digital signal by an A/D converter to obtain digital image data.

The analog signal processing section that A/D converts this image analog signal is configured as shown in FIG. 2, for example. The line sensor 10 outputs an image analog signal 11 when the line signal j and the clock are input manually. S/H circuit 1
1 consists of an analog switch, a capacitor, an operational amplifier, etc., and turns the analog switch on/off]
? 11 signal k samples the image analog signal i1 from the line sensor and sends the image analog signal 12 to the amplifier 12. The amplifier 12 consists of a transistor, an operational amplifier, etc., and can set an arbitrary gain amount.
The image analog signal i3 amplified by the amplifier 12 is A/
The D converter 13 converts the analog signal into a digital signal. The pulse generator 14 is connected to the line sensor 10
, S/H circuit 11, and A/D converter 13.

Although not shown in the figure for boat fishing, in order to correct uneven illumination of the light source and variations in sensitivity of the line sensor, a white reference plate is read in advance and digital calculation processing, so-called shading correction, is performed.

[Problem to be solved by the invention]

With the conventional technology described above, even if shading correction is performed, it is not possible to correct analog signals such as variations in the dark output of the line sensor, analog signal drift due to temperature dependence, and offsets in the analog signal processing section. It is necessary to set the offset adjustment and the gain amount of the amplifier while considering the variation of the analog signal due to many factors with respect to the input range of the A/D converter, which is very time-consuming and reduces the dynamic range. It had become noticeably smaller. In particular, light sources such as fluorescent lights are placed near the line sensor, so
The ambient temperature of the line sensor fluctuates widely, and the analog signal fluctuates widely. Therefore, conventional technology has the problem of reducing the dynamic range, significantly deteriorating gradation, and reducing image quality. Ta.

[Means to solve the problem]

In order to solve the above problems, in the present invention, A/
In order to make the most effective use of the dynamic range of the D converter, a black reference data storage means for reading and storing black reference data in the main scanning direction prior to image input is provided, and the black reference data in the black reference data storage means is stored in the D converter. A black reference analog signal creation means is provided for creating an analog signal by A/A conversion, and furthermore, when inputting an image, the image analog signal obtained from the line sensor and the black reference analog signal created by the black reference analog signal creation means are provided. and differential amplification means for amplifying the difference between the two.

[Effect]

According to the above configuration, variations in the dark output of the line sensor, drift of analog signals due to temperature fluctuations, etc.
The black reference data can be measured and corrected for each image input for various analog signal fluctuations, and it is possible to correct variations in line sensor characteristics and temperature dependence of analog signals for the input range of the A/D converter. Offcent adjustment and amplifier gain amount can be automatically set without consideration, and the dynamic range of analog signals can be widened.

〔Example〕

The present invention will be explained below based on drawings of embodiments.

FIG. 1 is a configuration block diagram showing one embodiment of an analog processing circuit of an image input device of the present invention.

In FIG. 1, the line sensor 1 is a known sensor consisting of a CCD line sensor, a phototransistor array, an amorphous silicon sensor, etc., and when a line signal or clock is input, an image analog signal a1 is output. The S/H circuit 2 is a known one consisting of an analog switch, a capacitor, an operational amplifier, etc., and is sampled and held by a control signal C that turns on/off the analog switch, and the image analog signal a2 is sent to the differential amplifier 3.
is input. Further, the other input of the differential amplifier 3 is given from the buffer amplifier 7 as a black reference analog signal h4. The differential amplifier 3 serving as the differential amplification means may be a known one consisting of a transistor, an operational amplifier, etc., can set an arbitrary gain amount, and sends an image analog signal a3 to the A/D converter 4. The A/D converter 4 converts an analog signal into a digital signal, and may be of any known type.

The black reference data storage section 5 is a general random access memory or the like, and stores black reference data prior to an image input operation. To obtain the black reference data, a black reference board (not shown) is read, the light source is turned off, and the image data h1, which is the output of the A/D converter 4, is stored in the black reference data storage section 5.
The black reference data storage unit 5 that obtains and stores this black reference data serves as a black reference data storage means.

During the image input operation, the black reference data h2 is read out from the black reference data storage section 5 in synchronization with the sampling of the S/H circuit 2, and the digital signal is converted into an analog signal by the D/A converter 6 and sent via the banfa amplifier 7. is sent to the differential amplifier 3 as a black reference analog signal h4, and by subtracting the dark output in the main scanning direction, the image analog signal a
3 is a pure image signal. The D/A converter 6 and the buffer amplifier 7 constitute a black reference analog signal generating means. Banfa amplifier 7 can be a general amplifier, D
/A converter 6 can be omitted if it has good drivability.

Further, when storing the black reference data, the output of the bumper amplifier 7 is controlled by the control signal e so as to have a zero potential.

The pulse generator 8 is a line sensor l.

S/H circuit 2. , the A/D converter 4, the black reference data storage section 5, the D/A converter 6, and the banfa amplifier 7. It can be composed of

In addition, instead of inputting the black reference analog signal h4 to the differential amplifier 3, it is also possible to input it as a negative reference of the A/D converter 4, but in order to operate at high speed, the time constant relationship and stability must be considered. So it's not desirable.

〔Effect of the invention〕

As described above, according to the present invention, variations in analog signals due to line sensor characteristics, temperature dependence, offsets in the analog signal processing section, etc.
It is possible to memorize the black reference data prior to the image input operation to compensate for various analog signal fluctuations, and correct it in an analog manner during the image input operation, maximizing the dynamic range according to the input range of the A/D converter. Because it can be set, it is possible to collect image data with excellent gradation, especially for color image data collection.
Furthermore, there is no need to make offset adjustments in anticipation of changes in dark output due to temperature, etc., which reduces man-hours.
It has many effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an analog processing circuit of an image input device according to the present invention, and FIG. 2 is a block diagram showing an example of a conventional analog processing circuit. 1... Line sensor 2... S/H circuit 3... Differential amplifier 4... A/D converter 5... Black reference data storage section 6... D/A converter 7. ...Banpha Amplifier 8...Pulse Generator and above Applicant Seiko Electronic Industries Co., Ltd. Agent Patent Attorney Keinosuke Hayashi

Claims (1)

[Claims] In an image input device having a line sensor, a black reference data storage means is provided for reading and storing black reference data in the main scanning direction prior to image input, and the black reference data in the black reference data storage means is D/A converted. A black reference analog signal creating means for creating an analog signal is provided, and furthermore, when inputting an image, a differential between the image analog signal obtained from the line sensor and the black reference analog signal created by the black reference analog signal creating means is provided. An image input device characterized by being provided with differential amplification means for amplifying the image.