JPS5845874B2 - Video signal quantization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for optically reading characters, symbols, marks, etc. written on, for example, a form and quantizing a generated video signal.

Conventionally, in a device that optically reads characters, symbols, marks, etc. written on a form, for example, as a means for identifying information such as characters, a sample and hold circuit 1 is used to give weight to the information, as shown in FIG. A so-called analog-to-digital conversion method, in which an analog-to-digital conversion circuit 2 is connected to the Ilo, and a method for simply detecting Ilo information as shown in FIG. 2 have been put into practical use as well-known techniques.

In particular, in FIG. 2, the white peak value of the video signal is detected by a white peak detection circuit 1 consisting of a white peak value detection diode 3, a white peak value holding capacitor 4, and a discharge resistor 5, and a comparator 7 This is a quantization method that compares the white peak value with the signal before detection.

However, with the simple circuit configuration described above, it is difficult to obtain complete information due to the darkness of the information.

Therefore, a method has been considered in which the shading of information is directly weighted and detected using an analog-to-digital conversion method as shown in FIG.

However, there is a drawback that no matter how much weight is given to light information in detection, it cannot be identified in the same way as dark information.

The present invention was made in view of the above circumstances, and its purpose is to provide information as a preliminary means for converting information into an analog digital signal in an optical information recognition device that optically reads information such as characters, symbols, marks, etc. Quantization of video signals that detects and quantizes the presence or absence of information in advance regardless of its density, and changes the amplification level only for the information determined to be "present", making it possible to recognize even fainter information than before. It is intended to provide a circuit system.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

In the figure, 6 is a white peak detection circuit consisting of a white peak value detection diode 3, a white peak value holding capacitor 4, and a discharge resistor 5, and the gray-light mixed video signal a1 shown in FIG. 4 is input to the input terminal e1. When the voltage is applied, a white peak signal a2 is detected at the output terminal e2.

That is, the DC component is detected by the white peak value detection diode 3.
It is designed to drop by the forward voltage Vf of .

Further, 7 is a comparator that compares the input signal □ and the output signal a2, and the output signal of this comparator 7 and the control circuit signal ax from the outside are outputted to the analog switch described later through the gate 8. It is composed of

Next, 15 is an inverting operational amplifier, and the input signal a1 is inputted to the zero input terminal of this amplifier 15 via a resistor 9 with a resistance value R1, and the input signal a1 is inputted between the zero input terminal and the output terminal. A control circuit 10 is formed by connecting a feedback resistor 11 with a resistance value R2 and a feedback resistor 12 with a resistance value R3 in parallel.
One zero input terminal is configured to be grounded via a resistor 13.

Reference numeral 14 denotes an analog switch connected in series with the resistor 11, which is turned on and off by the output signal of the gate 8 to control the degree of amplification of the video signal a1.

Note that 16 is a sample hold circuit which takes the output of the inverting operational amplifier 15 as an input signal, and 17 is an analog-to-digital conversion circuit.

Next, the operation of the present invention based on the above configuration will be explained.

In FIG. 3, when a video signal a1 for mixing shading is applied to the input terminal e1, a white peak signal a2 whose DC component is dropped by the forward voltage Vf by the white peak value detection diode 3 is applied to the output terminal e2. is detected.

(See Figure 4) Therefore, the video signal a1 and the white peak signal a2 are applied to one input terminal of the comparator 7, and the output signal of the comparator 7 and the external control circuit signal a are applied.
When x is input to the gate 8, it is compared and a pulse a3 is obtained at the output terminal of the gate 8 as shown in FIG.

On the other hand, when the video signal a1 is input to the inverting operational amplifier 15 and the analog switch 14 is in an OFF state, that is, open, the output terminal e4 of the amplifier 15 is
The signal amplitude at
It is expressed as 2.R3/R2+R3/R1.al.

Therefore, by short-circuiting the analog switch 14 in advance and automatically opening the analog switch 14 only when a black signal is detected during optical scanning of information, the output terminal e4 of the operational amplifier 15 is can obtain signal a4.

Note that the signal a5 represents the polarity of the signal at the output terminal e4, and represents an inverted signal of the signal a4.

Therefore, by extracting the signal a4 through the sample and hold circuit 16 and the analog-to-digital conversion circuit 17, the dark parts of the information can be captured more deeply and the lighter parts can be captured more deeply, thereby improving the recognition rate in the identification section. It becomes possible.

Although one embodiment of the present invention describes a circuit configuration in which one set of analog switches is provided, it is not necessarily limited to one set. A circuit configuration using an analog switch may also be used.

Of course, various modifications can be made without changing the gist of the present invention.

As explained above, the present invention provides a reading device that optically scans and reads an object to be read. It is characterized by controlling the degree of amplification of only

Therefore, it is possible to improve the reading rate of even light information whose shading is difficult to distinguish, and to achieve a practical effect at a low cost.

[Brief explanation of drawings]

1 and 2 are block diagrams showing conventional circuit systems, FIG. 3 is a circuit diagram of a quantization circuit system showing an embodiment of the present invention, and FIG. 4 is a waveform at key points in FIG. 3. It is a diagram. 6...White peak detection circuit (first quantization means)
, 10... control circuit (control means), 16, 17
...Sample and hold circuit, analog-to-digital conversion circuit (second quantization means).

Claims (1)

[Claims] 1. A first quantization means for obtaining a video signal by optically scanning an object to be read, which quantizes in advance a video signal valve such as a character or a symbol written in the object to be read; A control means for controlling the video signal to increase the amplification degree by the output signal of the first quantization means, an amplification means for amplifying the video signal with the amplification degree controlled by the control means, and the amplification means. and second quantization means for quantizing the video signal amplified by the video signal.