JPH0479476A - Picture input device - Google Patents

Abstract

PURPOSE:To improve the S/N of a feeble picture analog signal and to fully utilize the input range of an A/D converter by setting the amount of gain (amplification) suitable for respective picture analog signals obtained from a line sensor to be switched and amplified. CONSTITUTION:An analog signal comparison means 4 comparing the signal (voltage) level of the picture analog signal and outputting a decision signal, and an amplification amount switching means 5 switching and amplifying the amount of gain (amplification) by this decision signal are provided. A delay means 3 is provided to delay the picture analog signal during the comparison is performed by the analog signal comparison means 4 and during the amount of gain (amplification) of the amplifier 5 is switched, and a digital signal arithmetic (multiplication) means 8 is provided to turn the amount of amplification switched by the analog signal processing part to be constant amount of gain (amplification). Thus, the S/N of the picture analog signal processing part can be improved, and the dynamic range of the A/D converter 6 can be fully utilized.

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 unit that A/D converts this image analog signal is configured as shown in FIG. 2, for example. Line sensor 10 outputs image analog signal 11 when line signal j and black 7 are input manually. The S/H circuit 11 consists of an analog switch, a capacitor, an operational amplifier, etc., and samples the image analog signal i1 from the line sensor according to the control signal k that turns the analog switch on/off, and sends the image analog signal 12 to the amplifier 12.
send to The amplifier 12 consists of a transistor, an operational amplifier, etc., and can set an arbitrary gain amount, and the image analog signal i3 amplified by the amplifier 12 is converted from an analog signal to a digital signal by an A/D converter 13. .

The pulse generator 14 is connected to the line sensor 10, S/
A signal for controlling the H circuit 11 and A/D converter 13 is generated and output.

(Problems to be Solved by the Invention) In the conventional technology as described above, the analog signal processing section that processes the image analog signal obtained from the line sensor does not perform processing regardless of the signal (voltage) level of the input image analog signal. First, since it is amplified with a fixed gain (amplification) amount, when processing weak analog signals, the influence of noise on the image analog signal is large, and the A/D converter cannot be used effectively. Therefore, there was a problem in that the gradation was significantly deteriorated and the image quality was lowered.

[Means to solve the problem]

In order to solve the above-mentioned problems, in the present invention, in order to improve the S/N of the image analog signal processing section and to use the small range of the A/D converter as effectively as possible, the analog signal processing section , the image analog signal signal (
An analog signal comparing means for comparing voltage) levels and outputting a determination signal is provided, and an amplification amount switching means is provided for switching the gain (amplification) amount and amplifying based on the compared determination signal. Furthermore, a delay means is provided to delay the image analog signal while comparing it with the analog signal comparison means and switching the gain (amplification) amount of the amplifier.
After conversion, a digital signal calculation (multiplying) means is provided to make the amplification amount switched by the analog signal processing section a constant gain (amplification) amount, and the judgment signal is held during A/D conversion and digital signal calculation. A data latch means is provided for this purpose.

[Effect]

According to the above configuration, it is possible to automatically set the gain (amplification) amount suitable for the signal (voltage) level of the image analog signal obtained from the line sensor, and it is possible to automatically set the amount of gain (amplification) that is suitable for the signal (voltage) level of the image analog signal obtained from the line sensor. can process the signal,
Also, when processing weak analog image signals, gain (
Since the amount of amplification (amplification) can be increased, the wide range of the A/D converter can be used effectively.

〔Example〕

The present invention will be explained below based on drawings of embodiments.
FIG. 1 is a configuration block diagram showing an embodiment of an analog signal processing section of an image input device of the present invention, and FIG. 3 is a timing chart thereof.

In FIG. 1, a line sensor 1 is a known sensor such as a CCD line sensor, a phototransistor array, an amorphous silicon sensor, etc., and when a line signal and a clock a are input, an image analog signal g is output.

In S/H circuit 2, analog switch, capacitor,
It is a well-known device consisting of an operational amplifier, etc., and is sampled and bolded by a control signal for turning on/off an analog switch, and the image analog signal is input to a delay circuit 3 and an analog signal comparator 4.

The analog signal comparator 4 is composed of a known comparator (voltage comparator) having a strobe function, and compares the voltage level of the image analog signal at an arbitrary level using the control signal d, and calculates the result as a magnitude result. A determination signal f is output.

The details of the programmable gain amplifier 5 include an operational amplifier 20, resistors R1, R2a,
Gain (amplification) in a known non-inverting amplifier circuit consisting of R2b
The gain (amplification) amount is changed by switching the resistors R2a and R2b for determining the amount using the analog switch 21. The signal for switching the analog switch at this time is determined by the determination signal f obtained by the analog signal comparator 4, and the amount of gain (amplification) is determined and sent to the A/D converter 6 as an image analog signal j.

The delay circuit 3 compares the signal (voltage) level of the image analog signal with the analog signal comparator 4, and uses the determination signal f to determine the gain (amplification) with the programmable gain amplifier 5.
While setting the amount, a delay circuit for delaying the image analog signal may be a known one similar to the S/H circuit sampled by the control signal C and shown in bold.

The A/D converter 6 is also of a known type, and converts the analog signal into a digital signal in accordance with the control signal e, and sends it to the arithmetic processing unit 8 as an image signal.

The launch circuit 9 sends the image analog signal j to the A/D converter 6.
While the judgment signal f is being converted into an image signal k, it is held and sent to the arithmetic processing section 8, and a general data latch may be used.

The arithmetic processing unit 8 uses the determination signal m to perform a programmable
In order to keep the gain (amplification) amount set in the gain amplifier 5 constant, it is multiplied and divided according to the gain (amplification) H.
A known multiplier may be used, or if the set gain (amplification) amount is a multiple of 2, a general shift register or a data selector for bit shifting may be used.

The pulse generator 8 generates and outputs signals that control the line sensor 1, the S/H circuit 2, the delay circuit 3, the analog signal comparator 4, the A/D converter 6, and the latch circuit 9. It can be configured with a general counter or the like to generate a control signal.

In the embodiment of the programmable gain amplifier shown in FIG. 4, FIG. 1 has been explained by switching the gain (amplification) M to two stages. It is also possible to do so.

〔Effect of the invention〕

As described above, according to the present invention, the amount of gain (amplification) suitable for each image analog signal obtained from the line sensor is set, and the amount of gain (amplification) is switched and amplified. The S/N of the image analog signal can be improved, and the input range of the A/D converter can be used as effectively as possible, making it possible to collect image data with excellent gradation, especially in color. It has many advantages such as excellent gradation for image data collection, easy improvement of S/H without using a high-performance operational amplifier such as an amplifier, and low cost.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing an example of an analog processing section of an image input device of the present invention, FIG. 2 is a configuration block diagram showing an example of a conventional analog processing section, and FIG. 3 is the configuration of FIG. 1. FIG. 4 is a circuit diagram of one embodiment of a programmable gain amplifier. Line sensor S/H (sample/bold) circuit Delay circuit Analog signal comparator Programmable gain amplifier A/D converter Pulse generator Processing section

Claims (1)

[Claims] In an image input device having a line sensor, an analog signal comparator that compares the image analog signals obtained from the line sensor in terms of magnitude at an arbitrary preset level and outputs a judgment signal; A programmable gain amplifier that switches and amplifies the amount of gain (amplification) based on a judgment signal, and a gain (amplification) that is switched by the programmable gain amplifier.
An image input device comprising an arithmetic processing unit that performs multiplication and division according to a gain (amplification) amount via an A/D converter in order to make the amount constant.