JPS59111466A - Binary-coding device of analog signal - Google Patents

Abstract

PURPOSE:To attain suitable binary-coding by providing a means transmitting a reference signal in response to the illumination amount of light from an illumination means and a means compensating the fluctuation of a sampling signal by the reference signal. CONSTITUTION:An analog picture signal obtained from a photoelectric converting element 1 is led to a sample hold circuit 3 via an amplifier 2. An output signal VS of the sample hold circuit 3 is applied to a + input terminal of a differential amplifier 5 and a delay element 4. A delay signal VS-1 delayed by the sampling period at the delay element 4 is applied to a - input terminal of the differential amplifier 5 via a changeover switch 13 controlled and switched by a counter 16. A differential output signal VD of the differential amplifier 5 is applied to a + input terminal of a comparator and a - input terminal of a comparator 7, and comparison voltages +delta and -delta fluctuated in response to the illumination amount of light are applied to other terminal of the comparators 6, 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an analog signal binarization device that binarizes an analog signal such as an image signal.

Prior Art Conventionally, in order to binarize an analog signal such as an image signal obtained by an image pickup tube or a solid-state image pickup plate using a CCD (charge-coupled device), there are many binarization methods such as those that use a fixed threshold. The device is known. Among such conventional binarization devices, so-called time-difference binarization devices sequentially sample analog signals such as image signals and sequentially binarize the analog signals according to the results of detecting differences between adjacent sample values. The converting device is known from, for example, Japanese Patent Laid-Open No. 58-119526. In this time difference binarization device, Fig. 1(A)
As shown, the film F irradiated by the lamp LP
The image on M is irradiated via a lens LN to a photoelectric conversion element using a CCD, thereby converting it into an analog signal, and then binarizing it by a binarizing circuit BC. However, the image of the film FM is not a positive image consisting of a white portion W and a dotted portion B as shown in FIG. 1(C), but rather a white image as shown in FIG. In the case of a negative image consisting of a portion W' and a point portion B', the image output analog image signal is binarized and printed using a laser printer or the like as shown in Fig. 1 CC).
When reversing and recording in the form of a positive image, the following problem occurred.

That is, the image signal obtained from the solid-state image sensor CCD, for example, when using Toshiba Corporation's TCD102G-1 type,
As shown in FIGS. 2(A) to (C), a dummy output for 32 pixels is provided at the beginning of the l-line output period, and after the subsequent effective image signal for 2048 pixels, a dummy output for 4 pixels is provided again. A dummy output is provided. Therefore, Fig. 1(A)
When converting a negative image of film FM into a binary signal using the imaging system shown in Figure 2, the black part at the periphery of the negative image of film FM as shown in Figure 1 (B) is converted into a binary signal. The image is captured across both the dummy pixel shown and the effective pixel.

Therefore, as shown in FIGS. 3(A) to (C), FIG.
The black and white binary positive image shown in C) is now represented by a ternary level image signal. In other words, Fig. 3 (
As shown in C), the level difference generated between the dummy output level up to pixel number 32 and the white level during effective output is added to form a three-level image signal.

Therefore, when simply time-difference binarization is performed on such a three-level analog image signal as in the past,
Since there is a level change between the 32nd and 33rd pixels, as a result, the 33rd and subsequent pixels are not determined to be accurately at the white level. That is, Fig. 3(C)
In the analog image signal shown in , the first level changes detected by time-difference binarization processing are the 36th and 37th.
It should be between the 32nd and 33rd pixels, but it should be between the 32nd and 33rd pixels.
There is a drawback that a level change is detected between the 33rd and subsequent pixels, and as a result, all pixels from the 33rd onwards are determined to be black.

Further, when microfilm is used, a halogen lamp is used as a light source for illumination because the original (the image portion of the microfilm) is much smaller than the document used in facsimile or the like. In order to correctly binarize the analog signal, this halogen lamp is turned on using a stabilized direct Btiw source, so that the amount of light is controlled to be always stable.

However, lighting a 24 V, 150 W lamp using a stabilized DC power supply, for example, has the disadvantage of not only significantly increasing the cost of the lamp but also increasing the amount of space it occupies.

Purpose In view of the above-mentioned points, an object of the present invention is to provide an analog signal binarization device that is equipped with means for compensating for changes in the amount of illumination light and also has various advantages of time-difference binarization processing. There is a particular thing.

In order to achieve such an object, the present invention sequentially samples the image analog No. 1 obtained by irradiating the image with illumination light from the illumination means, compares the sampled signal with the immediately preceding sampled signal, and An apparatus for binarizing an image analog signal includes means for transmitting a reference signal according to the amount of illumination light from the illumination means, and means for compensating for fluctuations in the sampled signal using the reference signal.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 4 shows an embodiment of an analog signal binarization device to which the present invention is applied. In the configuration shown.

An analog image signal obtained from a photoelectric conversion element 1'6) such as a CCD is introduced into a sample/hold circuit 3 via an amplifier 2. Then, in synchronization with the clock signal CLKI from the oscillator 15, until the next sample value is obtained,
Hold that sampling signal. The output signal Vs of the sample/hold circuit 3 is supplied to the (+) input terminal of the differential amplifier 5 and the delay element 4. The delayed signal Vs-1 delayed by the sampling period in the delay element 4 is supplied to the (-) input terminal of the operational amplifier 5 via the changeover switch 13 controlled by the counter circuit 18. Therefore,! iA
The differential between two adjacent sample values, such as the signal level difference between two adjacent pixels, is also sent to the operational amplifier 5. operational amplifier 5
The difference output signal Vo of , are supplied to the (-) input terminal of comparator 6 and the (+) input terminal of comparator 7, respectively. As a result, when the difference output signal vl) is larger than the comparison voltage Q, a high logic level comparison output signal is obtained from the comparator 6, and when the difference output signal Vo is smaller than the comparison voltage -δ, the comparison output signal from the comparator 7 is obtained. A high logic level comparison output signal is obtained from the comparators 6 and 7, and when the difference output signal Vo is between the comparison voltages +6 and -δ, low logic level comparison output signals are obtained from both comparators 6 and 7. .

The comparison output signals of comparators 88 and 7 are supplied to the set terminal and reset terminal of flip-flop 10 via AND gates 8 and 8, which are opened in response to clock signal CLK2 from oscillator 15, respectively. Therefore,
As the difference output signal VO exceeds the comparison voltage δ and becomes lower than the comparison voltage −δ, a binarized output signal is sent out from the flip-flop IO. In addition, comparator 8 and ? Zener diodes 17 and 18 connected to the output terminals of are limiters provided to match the TTL levels of AND gates 8 and 8.

Therefore, the counter circuit 18 controls the changeover switch 13 as follows.

For example, when counting the clock signal of pixel period sent from the oscillator 15 and binarizing the image signal shown in FIG. Until it corresponds to the 34th pixel,
The switch 13 is switched to the comparison voltage Vref side (see FIG. 5). As a result, the 33rd pixel is determined to be white (see FIG. 3(C)). Next, for the 34th and subsequent pixels, the digital switching switch 13 is connected to the delay element 4 side, and the above-described time difference binarization process is performed.

FIG. 5(A) shows a circuit for compensating for voltage fluctuations of a commercial power supply. Here, 20 is a voltage drop transformer connected to a commercial power supply, 22 is an AC lighting lamp connected to the secondary winding of the transformer 2o, 24 is a photo sensor that detects the amount of light emitted from the lamp 22, and 2B 28 is an inverting amplifier for obtaining the comparison voltage -δ; and 30 is an amplifier for obtaining the comparison voltage Vref.

FIG. 5(B) shows a change over time in the output voltage Vp obtained from the photosensor 24. As is clear from this figure,
The amount of light from the lamp 22 changes over time at a frequency twice the commercial frequency. This means that the light layer irradiated to the photoelectric conversion element 1 (see FIG. 4) changes at a frequency twice as high as the trademark frequency. Therefore, the comparison voltages +[delta] and -[delta] applied to the comparators 8 and 7 shown in FIG. 4 and the comparison voltage Vref applied to the differential amplifier 5 also vary in accordance with the above-mentioned variation in the amount of light. Therefore, it is possible to ignore variations in the amount of light that would be detrimental during the binarization process of analog signals.

As shown in FIG. 1(C), the positive image reproduced from the negative film has a white background at the periphery.

For example, the 33rd pixel shown in FIG. 3(C) corresponds to the peripheral portion of the positive image. Therefore, it is preferable that the comparison voltage Vref mentioned above is set to a level comparable to the sampled output voltage Vs corresponding to the black level after binarization. In addition, image reading other than film, such as J
It can also be applied to devices that read images based on the reflection of an Ic document.

Effects As explained above, according to the present invention, even if there is an unnecessary level change in the No. 16 level of the analog signal when binarizing the analog image signal, such unnecessary level change can be ignored. Accurate binarization processing can be performed.

Further, according to the present invention, since there is no need to turn on the illumination lamp with direct current, it is possible to obtain a binarization device that reduces cost and occupies space.

Furthermore, according to the present invention, time-difference binarization processing can be performed, which eliminates the need for output change correction due to shading of the optical system, spatial variation correction, and Gamma correction of the film.
A value converter can be obtained.

[Brief explanation of the drawing]

FIG. 1(A) is a block diagram showing an analog signal binarization device N according to the prior art, FIG. 1(El) is a timing diagram explaining a negative, and FIGS. 4 and 5(A) are A block diagram showing one embodiment, FIG. 5(B) is similar to FIG. 5(A).
FIG. 3 is a diagram showing changes in the output voltage of the photosensor 24 shown in FIG. 1...Photoelectric conversion element, 2...Amplifier, 3...Sample/hold circuit. 4... Delay element, 5... Differential amplifier, 6.7... Comparator, 8.9... AND gate, +j... Flip-flop, 13... Changeover switch, 15... - Oscillator, 17, 113... Limiter, 20... Transformer, 22... Illumination lamp. 24... sensor, 213.28.30... amplifier. Figure 5 (A) (B)

Claims (1)

[Claims] The illumination light from the illumination means is irradiated onto the image, and the image analog signals are sequentially sampled, and the sampled signals are compared with the immediately preceding sampled signal, so that two of the image analog signals are
An apparatus for converting values into values, characterized by comprising means for transmitting a reference (No. J) according to the amount of illumination light from the illumination means, and means for compensating for fluctuations in the sampling signal using the reference signal. Analog signal binarization device.