JPS61244182A - Method and device for binarizing video signal - Google Patents

Abstract

PURPOSE:To read out accurately optical recording information by setting the thresholds of plural levels and allowing an output video signal to correspond to one of them more accurately even if the output video signal is dulled to a mountain shape. CONSTITUTION:Comparators 31a, 31b, and 31c are set to the threshold (a) of a level higher than 50% mark rate, the threshold (9b) of the level corresponding approximately to 505 mark rate, and the threshold (c) of a level lower than 50% mark rate by adjusting variable resistances VR. The video signal is compared with these thresholds by comparators 31a, 31b, and 31c. If waveforms of the video signal and thresholds have relations indicated by broken lines A and C, the binary-coded output is about 50% for the threshold (a) in the former case and is about 50% for the threshold (c) in the latter case, this output is used as read data not to generate error in FM decoding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides optical recording information that is binary-encoded by an FM encoding method and recorded as an optical pattern on an optical recording medium, and is photoelectrically recorded by a reading means. The present invention relates to a video signal binarization method and apparatus for converting the output video signal from the reading means into binary high or low values based on a threshold value and binarizing the output video signal.

[Prior Art] In an optical recording medium, data is recorded in a data recording area as a pattern of changes in optical properties. This recording is performed by, for example, making holes, etc., to provide portions exhibiting high reflectance and portions exhibiting low reflectance, and arranging these in a predetermined code pattern.

In an optical record information reading device that reads this type of optical record,
An optical sensor reads the reflected light whose level fluctuates in response to the high and low reflectance caused by the code pattern on the medium, and converts it into a digital signal depending on whether the level of the video signal is above or below a predetermined threshold. Signal.

At present, there are optical sensors used for reading, such as compact disc pickups, which individually read one point on a code pattern on a medium. This type of reading method is suitable for reading data by following a spiral track.

However, for optical recording media that record information two-dimensionally at high density, linear or planar sensors such as CCD linear sensors are preferable to sensors that read each point individually. Therefore, it is desirable to read a certain area at once in terms of reading speed and the like.

By the way, when a group of patterns as a data string is scanned and read at a constant speed by a CCD linear sensor, the level fluctuation of reflected light due to the code pattern of the optical recording medium is output as a series of video signals. In this reproduction, as a matter of course, the result determined from the amount of light is a 1-bit logical value indicating high or low reflectance. This logical value is then read out by binarizing the video signal from the optical sensor.

By the way, in conventional technology, in order to binarize a video signal, one of a series of video signals is
This is done by distinguishing between parts that are higher than this threshold and parts that are lower. However, this conventional technology has the following problems, and its practical application has been delayed.

[Problems to be Solved by the Invention] Conventionally, an output video signal from a CCD linear sensor exhibits a sharp response when capturing a portion where the reflectance of the medium changes (a boundary portion of a code pattern where the reflectance changes in height or low). No, this is because there are problems with the responsiveness of the optical sensor itself, as well as the effects of resolution, aberrations, etc. of the optical system that magnifies the reflected light from the medium.

Incidentally, the video signal should originally be a rectangular wave corresponding to the code pattern. However, in reality, due to the above-mentioned influence, the output is distorted in a mountainous manner. When the output waveform forms a mountain, the width is different at the top and bottom of the mountain, so there is a risk that the output waveform will be binarized in any way depending on the threshold setting level. Therefore, a problem arises in that the optically recorded information cannot be read out accurately.

In addition, with conventional technology, the average level of the video signal from the sensor fluctuates up and down due to deviations in the positional relationship between the optical recording medium and the sensor due to the accuracy limit of the reading device mechanism, distortion of the optical recording medium itself, etc. If such an unstable state occurs, the deviation between the threshold value and the average level of the video signal will fluctuate when the video signal is binarized, causing the problems described above. will occur.

Therefore, as a countermeasure to this problem, it is possible to reduce the distortion of the video signal. However, although it is possible to improve the resolution and aberration of the optical system to some extent, the apparatus becomes expensive and impractical. On the other hand, the responsiveness of the sensor can be improved by sacrificing the reading speed, but this is difficult when a large amount of data needs to be handled at high speed, such as with optical recording media.

The present invention was made to solve the above-mentioned problems, and the threshold value can be set at multiple levels, and even if the output video signal is distorted like a mountain, it can be dealt with more accurately by using one of the threshold values, and the optical recording Information can be read accurately, and
Even if there is instability in the overall video signal from the sensor due to fluctuations in the positional relationship between the optical recording medium and the sensor due to the accuracy limits of the reading device mechanism, etc., or distortion of the optical recording medium itself, it can be handled accurately. It is an object of the present invention to provide a video signal binarization method and apparatus that can perform the following steps.

[Means for Solving the Problems] The first invention of the present application is to photoelectrically read optical recording information recorded on an optical recording medium as an optical pattern by binary encoding using an FM encoding method using a reading means. ,
In the video signal binarization method of converting the output video signal from the reading means into binary values of high or low using a threshold value as a reference and binarizing the video signal, the video signal is distributed to a plurality of systems, and each system is At,
Each signal is binarized using different threshold values as a reference, and in synchronization with a certain sampling signal, either the high or low state is sampled from the binarized signal in each of the above systems, and the state is calculated. and compare the count value of each system in unit time with a preset mark rate (ratio occupied by either the high state or low state of the binary code in the FM encoding method (the same applies hereinafter)). The present invention is characterized in that the binarized signal of the system whose count value is closest to the set mark rate is set as the regular output signal.

In addition, the second invention of the present application is to photoelectrically read optical recording information that has been binary encoded by an FM encoding method and recorded as an optical pattern on an optical recording medium by a reading means, and output video from the reading means. In a video signal binarization device that converts and binarizes a signal into high or low binary values based on a threshold value, the video signal is converted into binary values based on different threshold values, as shown in Figure 1. a plurality of systems of binarization means for converting the signals into a plurality of systems; a plurality of systems of temporary storage means for temporarily storing the signals binarized by the binarization means of each of the above systems, respectively; and binarization of each of the above systems. The proportion of either the high or low state in the unit time of the binarized signal in the means is compared with a preset mark rate, and the proportion of the high or low state in the unit time is determined. The present invention is characterized by comprising system selection means that instructs the temporary storage means of the system whose value is closest to the set mark rate to output the stored binary signal.

[Function] As described above, when the threshold value is set constant, it is difficult to accurately binarize a video signal that fluctuates depending on various conditions such as mechanical shake during movement of the optical recording medium. , when information is encoded using the FM encoding method, the mark rate is approximately a constant value (for example, 50%)
The above problem was solved by focusing on the property that .

That is, the present invention can solve a video signal that is distorted like a mountain.
A plurality of thresholds with different levels are set, and binarization is performed for each threshold, and among them, the state of either high or low in a unit time of the signal binarized by the binarization means of each system mentioned above. The proportion occupied by the high or low state in a unit time is compared with a preset mark rate, and the one in which the proportion occupied by either the high or low state in a unit time is closest to the set mark rate is adopted as correct data.

First, the FM non-coding method, which is a premise for application of the present invention, will be explained.

The FM encoding method on which the present invention is based is based on the second
As shown in Figure (a), a pulse that has both high and low parts during a unit length represents "IN", and a pulse that has either a high or low part during a unit length represents "0". ”. This is shown in the same figure (
As is clear from the comparison with the NRZ (non-return-to-zero) method shown in b), the FM encoding method is
The mark rate is about 50%.

Now, when reading FM-encoded data from an optical recording medium using a CCD linear sensor, if the data has a pattern as shown in Figure WII3 (a), the resulting video signal is as follows: The waveform becomes distorted as shown in FIG. 2(b).

In the present invention, a video signal having such a waveform is binarized in parallel by a plurality of systems of binarization means. and,
The number of pulses of the binary output signal from each system is counted, and the number of high or low states per unit time is determined for each system. The binarized output of the digitizing means is adopted as correct read data.

When a video signal is distributed to multiple channels and binarized, the threshold value is set to a different level for each channel.For example, when the video signal is output at a normal level, Thresholds at different levels are set, such as a threshold C corresponding to a nearby level and a threshold corresponding to a half-width level of the same waveform, and a threshold a corresponding to the bottom portion of the same waveform. That is, these threshold values a, b, and c are set in a relationship such that their levels are shown in the following equation.

Threshold a - Threshold C - Threshold C In each system, this video signal is compared with the respective set threshold values and binarized.

In this way, for a video signal whose average level fluctuates, data that is binarized based on a mark rate close to a constant value (for example, 50%) among multiple set threshold values is determined as correct data. Therefore, various problems such as those mentioned above can be easily solved.

[Example] This embodiment, which will be described with reference to FIGS. 4 and 5, is an example in which an optical memory card is used as an optical recording medium. Note that FIG. 4 is a block diagram showing the configuration of an embodiment of the video signal binarization method and apparatus of the present invention, and FIG. 5 is an explanatory diagram showing the relationship between the video signal waveform and the threshold value.

<Configuration of Embodiment> The video signal binarization device of the embodiment shown in FIG. 4 is configured with the following components. Note that the device of this example has the following characteristics:
This is an embodiment of the binarization device of the second invention of the present application, and is also an example of a device for carrying out the binarization method of the first invention of the present application.

This embodiment first uses comparators 31a, 31b, and 31c as binarization means for binarizing a video signal input via an amplifier 20 from a CCDC linear sensor that faces an optical memory card C and reads data. ,and,
It has sampling circuits 32a, 32b, and 32c.

Second, a buffer 33a serves as temporary storage means for a plurality of systems that temporarily stores the signals binarized by the respective systems of binarization means, respectively.

33b and 33c.

Thirdly, temporarily save the system in which the proportion of either high or low state in the unit time of the signal binarized by the binarization means of each system is the value closest to the set mark rate. A counting circuit 41 serves as a system selection means for instructing the means to output the stored binary signal.
a, 41b.

41c and a determination circuit 42.

As the first components, the comparators 31a, 31b, and 31c are composed of, for example, operational amplifiers, and a video signal is input to a non-inverting terminal, and a threshold value serving as a reference for comparison is input to an inverting terminal. This threshold value is formed by dividing the power supply voltage Vcc using a variable resistor VR.

Each of the comparators 31a, 31b, and 31c has a variable resistor VR adjusted so that each has a different threshold value. As shown in FIG. 5, in this embodiment, this threshold value is defined as either the high or low state of the binarized signal in a unit time, based on the case where the average level of the video signal is a normal value. The threshold value a is the level at which the proportion of the mark ratio is larger than 50%, that is, the level corresponding to the tail portion of the waveform, and the level that corresponds approximately to the mark ratio of 50%, that is,
The level threshold corresponding to the half-width part of the waveform is:
The threshold value C is set to a level at which the mark rate is less than 50%, that is, a level corresponding to the top of the waveform.

The sampling circuits 32a, 32b, 32c are composed of logic circuits such as AND gate circuits, and use the sampling clock as a gate signal to operate the comparators 31a, 31.
b.

The high level signal or low level signal (high level signal in this embodiment) of the binary signal output from 31c is sampled.

Buffers 33a and 33b are second components.

33c consists of a register or random access memory. These buffers 33B, 33b, 33
c is equipped with a gate circuit (not shown) for controlling output, and when an output permission signal is input, it outputs the stored data to a data bus 50 for sending to a data processing device or the like.

Further, a counting circuit 41a is a third component.

41b and 41c are composed of counters, for example, and count the number of pulses of the output signals of the sampling circuits 32a, 32b, and 32c.

Similarly, the third component, the determination circuit 42, includes, for example, a register or memory that holds the counts from each of the counting circuits 41a, 41b, and 41c, and an arithmetic circuit. A standard mark rate is set in advance in the calculation circuit, and this mark rate is compared and calculated with each count value, and the system outputs a binary value that is the closest count value to the standard mark rate. A buffer 34a belonging to
(7) Output an output permission signal to either 34b or 34c.

<Operation of the embodiment> Next, the operation of the embodiment will be explained with reference to the above-mentioned figures.

In the above configuration, the CCD linear sensor IO is configured to detect the optical memory card C by linearly arranged photodetectors.
Detects the reflected light from the storage medium and outputs it as serial data according to a certain clock pulse. This output becomes a video signal with a waveform as shown in FIG. 3(b). This video signal is amplified by the amplifier 20 and input to each of the comparators 31a, 31b, and 31c of the binarization means.

Here, each of the comparators 31a, 31b, and 31c has a threshold value set in advance to the above-mentioned value by adjusting the variable resistor VR.
a, 31b, and 31c, each is compared with a threshold value. Then, of the waveform of the video signal, a portion higher than the threshold is output as a high level, ie, “1”, and a portion lower than the threshold is output as a low level, ie “0”.
is output as

FIG. 5 shows the state of the comparison. In the figure, the shaded area indicates the time when the binarization result becomes "1".

The binarized signal is processed by sampling circuits 32a and 32b.
.

32c. Here, the high level portion of the binary signal output is sampled. This sampling is performed in synchronization with a sampling clock from a synchronization signal generation circuit (not shown in the figure), and when the sampling clock is input. It is determined whether the level of the output waveform of the binary signal is high level or not, and if it is high level, sampling is performed.

That is, the binarized signals of each system are synchronized using the sampling clock as a reference.

This sampled signal is converted into a bar.

The read data is stored in the files 33a, 33b, and 33c. This bar 17733a, 33b +
33c, data is sequentially stored in a first-in, first-out format. Each buffer 33a, 3
The data stored in 3b and 33c is output to the buffer only when an output permission signal from a determination circuit 42, which will be described later, is input to the gate control terminal G.

Further, the sampling circuits 32a, 32b, 32
The signal sampled at c is also sent to the system selection means. Here, each sampling circuit 32a, 3
2b.

Counting circuits 41a, 41b, 4 corresponding to 32c
At 1c, high level signals are counted. That is, for example, the number of high level states per unit time is counted.

This count value is input to the determination circuit 42. In the determination circuit 42, among the counted values, those that match or are close to a preset mark rate (50% mark rate in this embodiment) are determined by comparison calculation.

Here, it is assumed that the waveform of the video signal and the threshold value have a relationship shown by a solid line B in the fifth UgJ. In this case, in the C system for which the threshold value a is set, the mark rate of its binarized output is greater than 50%, and in the C system for which the m value C is set, the mark rate of its binarized output is greater than 50%. On the other hand, in the b system in which the threshold value S is set, the mark rate of its binarized output is approximately 50%, and the count value closest to the set mark rate is output.

Therefore, under this condition, the b-system buffer 34b
sends an output permission signal to the Upon receiving this signal, the output gate of the buffer 34b is opened and the stored data is output onto the data bus.

Next, it is assumed that the waveform of the video signal and the threshold value have the relationship shown by broken line A or C in FIG. The former is a case where the video signal is shifted to the low level side, while the latter is a case where the video signal is shifted to the high level side. In these cases, the mark rate is 50 at the system threshold.
%.Therefore, in the conventional reading device, there is a high possibility that FM decoding will be performed incorrectly.However, in this embodiment, in the former case, the threshold value a, and in the latter case, Due to the threshold value C, the binarized output is approximately 50
%, so if you use this as the read data,
No errors occur during FM decoding.

As a result, the video signal is accurately binarized, and the reading accuracy of the reading device is improved.

<Modification of Embodiment> In the above embodiment, the high level state of the video signal is sampled in the sampling circuit, but it may be configured to sample the low level state.

Further, in the above embodiment, the mark rate is set to 50%, but it can be set to 0, for example, 75%, 25%, etc., depending on the mark rate in encoding of the optical recording medium.

Furthermore, in the above embodiment, as a binarization means.

Three systems, a, b, and c, are installed in parallel, but are not limited to this.
There may be four or more systems.

[Effects of the Invention] As explained above, the present invention allows the threshold value to be set at a plurality of levels, and even if the output video signal is distorted like a mountain, it is possible to respond more accurately to one of the threshold values, and the optically recorded information can be processed. In addition, instability of the entire video signal from the sensor due to deviations in the positional relationship between the optical recording medium and the sensor due to accuracy limits of the mechanism of the reading device, distortion of the optical recording medium itself, etc. Even if there is a problem, it can be effectively dealt with in the same way.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a video signal binarization device of the present invention, a block diagram showing the configuration of an embodiment of an optical recording information reading device, and FIG. 2 is a block diagram showing the configuration of an embodiment of an optical recording information reading device. FIG. 3 is an explanatory diagram showing the relationship between FM encoded and recorded data on an optical recording medium and a video signal. FIG. 4 is a block diagram showing the configuration of an embodiment of the video signal binarization device of the present invention, and FIG. 5 is an explanatory diagram showing the relationship between the video signal waveform and the threshold value. C... Optical memory card lO... CCD linear sensor 31a, 31b, 31c --- Comparator 32
a, 32b, 32c...sampling circuit 33a
, 33b, 33c = bar/7741a
, 41b, 41c - Counting circuit 42... Judgment circuit 50... Data bus applicant Computer Service Co., Ltd. Agent Patent attorney Iwao Mishina Figure 1

Claims (2)

[Claims] (1) A reading means photoelectrically reads optically recorded information that has been binary encoded by an FM encoding method and recorded as an optical pattern on an optical recording medium, and the output video signal from the reading means is set to a threshold value. In a video signal binarization method in which the video signal is converted into a high or low binary value as a reference and then binarized, the video signal is distributed to multiple systems, and each system:
Each signal is binarized using different threshold values as a reference, and in synchronization with a certain sampling signal, either the high or low state is sampled from the binarized signal in each of the above systems, and the state is calculated. The set mark is calculated by comparing the count value of each system in a unit time with a preset mark rate (the proportion occupied by either the high state or low state of the binary code in the FM encoding method). A video signal binarization method characterized in that the binarized signal of the system whose count value is closest to the ratio is set as a regular output signal. (2) A reading means photoelectrically reads the optical recording information that has been binary encoded by the FM encoding method and recorded as an optical pattern on the optical recording medium, and the output video signal from the reading means is set to a threshold value. A video signal binarization device that converts and binarizes the video signal into high or low binary values as a reference, comprising a plurality of systems of binarization means that binarize the video signal using different threshold values as a reference; Temporary storage means for a plurality of systems that temporarily store the signals binarized by the binarization means of the systems, respectively; Or, compare the ratio occupied by either the low state and the preset mark rate (the ratio occupied by either the high state or the low state of the binary code in the FM encoding method), and system selection means for instructing the temporary storage means of the system in which the proportion of one of the states is closest to the set mark rate to output the stored binary signal; A video signal binarization device characterized by: