JPS6022874A - Scanner - Google Patents

Abstract

PURPOSE:To eliminate as high as possible a quantized error generated in a scanner adopting the dynamic slice system by bringing a signal level of an image signal before one scanning to a quantization reference signal level in quantizing a video signal. CONSTITUTION:The video signal photoelectric-converted by a scanner element 3 is applied to a quantization reference signal circuit 8 comprising a low pass filter, a sample holding circuit 7 and a quantization circuit 9 via an amplifier 5. The sample holding circuit 7 keeps a constant level of the video signal based on the control signal from a controller 10 and applies the level to the quantization reference signal circuit 8 at a period just before generation of the video signal by the next scanning. An output of the quantization reference signal circuit 8 is brought into a quantization reference level of the next line at the quantization circuit 9 and the quantization without quantization error is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a scanner device that scans a two-dimensional image and quantizes the video signal into a binary or multivalued digital signal.

[Description of prior art]

Generally, in a system constituting a scanner device, the video signal of the system includes a blanking signal between one image signal scan and the next scan.

Conventionally, when quantizing such a video signal, the video signal is compared with a signal of an appropriate level for quantizing the video signal (in the following description, this method is referred to as a "fixed slice method"). Alternatively, a signal obtained by extracting only the low-frequency components of the video signal (in the following description, this signal is referred to as a "quantized reference signal") is compared with the video signal (in the following description, this method is called dynamic slicing). The quantized signal was obtained by the following method.

However, the fixed slice method has one drawback in that even though the images have the same shape, the same quantized signal cannot be obtained when the brightness of the images changes. In addition, in the conventional dynamic slicing method, since the low-frequency component signal follows changes in image brightness to some extent, the fixed slicing method does not produce any quantization distortion, but the image signal starts from the end time of the blanking signal. There is a drawback that an error occurs in the quantization G near the time of transition.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for eliminating as much as possible quantization errors that occur in a scanner device that employs a dynamic slicing method.

[Features of the invention]

In a scanner that scans two-dimensional images, one scan is always adjacent to the next, and the video signal at the start of the next scan has a signal level extremely close to the video signal of the previous scan. The aim is to use this signal level as the quantization reference signal level.

That is, the present invention includes a first circuit that amplifies a video signal;
A second circuit that samples and bolds the video signal immediately after the blanking signal has finished, and a third circuit that removes the high frequency components of the video signal and generates a quantized reference signal that follows the low frequency components of the video signal. a fourth circuit that generates a control signal to supply the output signal of the second circuit to the third circuit immediately before the end of the next blanking signal; and a fifth circuit that quantizes the video signal into binary values by comparing the output signal of the circuit with the output signal of the circuit. By supplying the quantization reference signal to the quantization reference signal circuit immediately before the end of the process, it is possible to reduce quantization errors caused by the dynamic slice method.

[Explanation based on examples]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A device according to an embodiment of the present invention will be described below with reference to the drawings.

First, FIG. 1 will be explained. The diagram shows a diagram of a device according to an embodiment of the present invention.
17 is a configuration diagram. In the figure, an optical signal of an image 1 passes through a scanner element 3 driven by a lens 2 and a drive circuit 4, and is input to an image signal amplifier 5. A video signal is obtained from the video signal amplifier 5, and the output side of the video signal amplifier 5 receives a quantization reference signal including a Templebold circuit 7 and a CR type low-pass filter circuit for creating a quantization reference signal for the video signal. Circuit 8 is connected. Also, the quantization circuit 9
The video signal from the amplifier 5 and the quantization reference signal from the quantization reference signal circuit 8 are introduced to the video signal input circuit 5, and the video signal is quantized using the dynamic slice method.

Further, the control signal generation circuit 10 generates a timing signal and supplies the signal to the temple bold circuit 7 and the child reference signal circuit 8.

Next, explaining FIG. 2, the waveform 20 is a video signal,
The signal to the other range is a video signal, and the signal to range 13 is a blanking signal. Further, the quantized reference signal indicated by the broken line 21 can be generated by using a CR filter circuit and appropriately setting a CR constant. The waveform in (a) is schematically shown in (b). Here, the waveform 22 is the waveform of a video signal obtained when the video has uniform brightness. At this time, the CR type low-pass filter circuit has waveform 2.
A quantized reference signal such as 3 is output. When the waveform 22 and the waveform 23 are compared and a difference operation is performed, a quantized signal of a waveform 24 shown in (c) is obtained. However, the waveform of the embodiment device is a waveform corresponding to a binary signal. Next, assume that the waveform of the calculation signal is waveform 5. This waveform represents a waveform when there is a change in the brightness of the image. Here, waveform 26 is a quantized reference signal. It can be seen that in this case, a quantized signal of waveform 28 is obtained. However, at this time, although no error occurs in section C, a quantization error occurs in the section. ``This is due to the charging/discharging characteristics of the CR filter circuit, and the correct waveform of the quantized signal must be waveform 29. For this purpose, the discharge characteristic of the CR filter circuit may be made as shown by the broken line 27, but in this case, the drawbacks associated with the fixed slice method described above will occur. (1.) is a video signal 30 and a quantized reference signal 32 when the dynamic slicing method according to the present invention is introduced.

li: For the doubled reference signal 32, in the section F, the reference signal level 31 of the section E is used as is. That is, this sample bolded level 31 in section E, released the bold signal to the smoothing reference circuit in section F, and corrected the waveform 26 in Figure 2 (d) to become waveform 32. It is something. As a result, the waveform of the quantized signal becomes waveform 29
This eliminates the drawbacks of the conventional dynamic slicing method.

Next, the operation of this device will be explained with reference to the configuration diagram in FIG. 1 and each waveform in FIG. 2. The timing generation circuit 10 supplies a timing signal to the sample bold circuit 7 so as to sample and bold the level of the signal 30 in the interval E in (g) of FIG.

This bold signal is supplied to the quantization reference signal circuit in a period F immediately before the generation of the video signal generated by the next scan.

In other words, it is possible to accurately follow the level of the video signal that occurs at the moment of the section F'7'i child-reference-doubled reference signal. In a strict sense, the bold signal is the bold version of the video signal from the previous scan, so it is different from the video signal level at that point, but when scanning a two-dimensional image, the video signal at the start of scanning is the same as the video signal from the previous scan. In many cases, the signal level is very close to that of the video signal, so it cannot be a practical problem.

〔Effect of the invention〕

The present invention outputs an image signal with little quantization distortion for images of the same shape even if the brightness of the image changes, and removes quantization errors as much as possible at the time of generation of the video signal. This has the effect of outputting high-quality image signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of signal waveforms related to the device according to the embodiment of the present invention. 1... Image (elephant), 2... Lens, 3... Scanner element, 4... Drive circuit, 5... Video signal amplifier, 7
...Sample bold circuit, 8...Quantization reference signal circuit, 9...Quantization circuit, 10...Control signal generation time 1! ) 3 Patent Applicant NEC Corporation Representative Patent Attorney Naotaka Ide A1 [

Claims (1)

[Claims] (1) In a scanner device comprising means for scanning a two-dimensional image and configured to generate a video signal including a blanking signal during each scanning period, a first circuit for amplifying the video signal; A second circuit that zumbles the video signal immediately after the blanking signal is completed, and a quantum circuit that removes the high frequency component of the video signal and follows the low frequency component of the video signal. a third circuit that generates a blanking reference signal; and a fourth circuit that generates a control signal so as to supply the output signal of the second circuit to the third circuit immediately before the end of the next blanking signal. , and the output signal of the first circuit above.
2. Compare the output signal of the third circuit and convert the above video signal to 2.
A scanner device characterized by comprising a fifth circuit that quantizes into values.