JPH0584590B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides optical recording information that is binary-encoded and recorded as an optical pattern on an optical recording medium using an FM encoding method, 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 high or low binary 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 portions in a constant code pattern.

In an optical recording/reading device that reads this type of optical recording, an optical sensor reads the reflected light whose level fluctuates in response to the two high and low reflectances caused by the code pattern on the medium, and the level of the video signal is adjusted to a predetermined level. Depending on whether it is above or below the threshold, it is binarized and converted into a digital signal.

At present, optical sensors used for reading include compact disk pick-ups, etc.
There is a type that reads each point of the code pattern on the medium individually. 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 CCD linear sensor scans and reads a group of patterns as a data string at a constant speed, level fluctuations in reflected light due to the code pattern of the optical recording medium are 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 the conventional technology, a video signal is binarized by using a certain threshold as a reference and determining which parts of a series of video signals are higher than this threshold and which parts are lower than this threshold. but,
This conventional technology has the following problems:
Its practical implementation is 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). do not have. This is because there are problems with the responsiveness of the optical sensor itself, as well as the effects of resolution, aberration, 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. but,
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. instability is inevitable. When such an unstable state occurs, the deviation between the threshold value and the average level of the video signal fluctuates when the video signal is binarized, causing the above-mentioned problem.

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 has been made to solve the above-mentioned problems, and the threshold value can be set at multiple levels. The recorded information can be read accurately, and the entire video signal from the sensor can be read out accurately due to deviations in the positional relationship between the optical recording medium and the sensor due to the accuracy limits of the reading device mechanism, distortion of the optical recording medium itself, etc. An object of the present invention is to provide a video signal binarization method and apparatus that can similarly accurately cope with instability.

[Means for Solving the Problems] The first invention of the present application photoelectrically optically records information recorded as an optical pattern by binary encoding using an FM encoding method on an optical recording medium using a reading means. A video signal binarization method for reading and converting the output video signal from the reading means into high or low binary values based on a threshold value and binarizing the video signal, the video signal being distributed to a plurality of systems, Each system binarizes the signal based on a different threshold, and in synchronization with a constant sampling signal, samples either the high or low state from the binary signal in each system. Then, count the number of states, and calculate the count value of each system in unit time and the preset mark rate {ratio of either high state or low state of the binary code in FM encoding method (hereinafter referred to as (same)}, and the binarized signal of the system whose count value is closest to the set mark rate is set as the regular output signal.

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

[Operation] As described above, when the threshold value is set constant, it is difficult to accurately binarize a video signal that fluctuates due to various conditions such as mechanical shake during movement of the optical recording medium. The present invention solves the above problems by focusing on the property that when information is encoded using the FM encoding method, the mark rate becomes a substantially constant value (for example, 50%).

That is, in the present invention, a plurality of threshold values having different levels are set for a video signal that is distorted like a mountain, and binarization is performed for each threshold value. Compare the proportion of the high or low state of the signal in the unit time with the preset mark rate, and calculate the proportion of the high or low state in the unit time to the set mark rate. The closest one is adopted as the correct data.

Therefore, first of all, the FM
The encoding method will be explained.

The FM encoding method on which the present invention is based, as shown in Figure 2a, represents "1" with a pulse that has both high and low parts within a unit length; Alternatively, this is an encoding system in which any part of a row represents "0" with a certain pulse. As is clear from comparing this with the NRZ (non-return-to-zero) method shown in Figure b, the FM encoding method has a lower mark rate.
It's 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 3a, the resulting video signal will be the same. The waveform becomes a rough waveform as shown in Figure b.

In the present invention, a video signal having such a waveform is binarized in parallel by a plurality of systems of binarization means. Then, the number of pulses of the binary output signal from each system is counted, the number of high or low states per unit time is determined for each system, and the system for which this value is closest to the preset mark rate is calculated. The binarized output of the binarizing means is adopted as correct read data.

When a video signal is distributed to multiple systems and binarized, thresholds are set to different levels for each system. For example, when a video signal is output at a normal level, there is a threshold c corresponding to the level near the top of a mountainous waveform, a threshold b corresponding to the level of the half width of the same waveform, and a threshold value b corresponding to the level at the bottom of the same waveform. Thresholds of different levels are set, such as threshold a corresponding to . 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 b<threshold C In each system, this video signal is compared with a respective set threshold and binarized.

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

[Example] An example of the present invention will be described with reference to FIGS. 4 and 5. This embodiment is an example in which an optical memory card is used as the optical recording medium. 4 is a block diagram showing the structure 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. The device of this embodiment is an embodiment of the binarization device of the second invention of the present application, and is also an example of a device for implementing the binarization method of the first invention of the present application.

In this embodiment, first, comparators 31a and 31 are used as binarization means to binarize a video signal input via an amplifier 20 from a CCD linear sensor 10 that faces an optical memory card C and reads data.
b, 31c, and sampling circuits 32a, 32
b, 32c.

Second, the buffer 33 is used as temporary storage means for multiple systems that temporarily stores the signals binarized by the binarization means for each system.
a, 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. Counting circuits 41a and 41 serve as system selection means for instructing the means to output the stored binary signals.
b, 41c, and a determination circuit 42.

As the first component, comparators 31a, 3
1b and 31c are composed of operational amplifiers, for example, 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.

The variable resistance VR of each comparator 31a, 31b, and 31c is adjusted so that the threshold value is different from each other. 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 rate is larger than 50%, that is, the bottom portion of the waveform, and the level that approximately corresponds to the mark rate of 50%, that is, the half width of the waveform. a threshold value b of the level corresponding to , and a threshold value c of the level corresponding to the mark rate smaller than 50%, that is, the top of the waveform.
It is set so that

The sampling circuits 32a, 32b, and 32c are composed of logic circuits such as AND gate circuits, and use the sampling clock as a gate signal to operate the comparator 31.
The high level signal or low level signal (high level signal in this embodiment) of the binary signal output from a, 31b, 31c is sampled.

Buffers 33a, 33 which are second components
b, 33c are registers or random access memories. These buffers 33a, 33
b, 33c are equipped with gate circuits (not shown) for controlling output, and when an output permission signal is input, they output the stored data to a data bus 50 for sending to a data processing device or the like.

Further, a counting circuit 41a, which is a third component,
41b and 41c are composed of counters, for example,
The number of pulses of the output signals of the sampling circuits 32a, 32b, and 32c is counted.

Similarly, the determination circuit 42 which is the third component
For example, each of the counting circuits 41a, 41b, 4
It is configured to include a register or memory that holds the count value from 1c, and an arithmetic circuit. The arithmetic circuit has a reference mark rate set in advance.
This mark rate and each count value are compared and calculated, and an output permission signal is sent to one of the buffers 34a, 34b, or 34c belonging to the system whose binary output has the count value closest to the reference mark rate. Output.

<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 10 is
A linearly arranged photodetector detects the reflected light from the recording medium of the optical memory card C,
Outputs as serial data according to constant clock pulses. This output becomes a video signal with a waveform as shown in FIG. 3b. 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, the comparators 31a, 31b, 31c are
In each case, the threshold value is set in advance to the above-mentioned value by adjusting the variable resistor VR. In each comparator 31a, 31b, 31c, the video signal is
Each is compared with a threshold value. 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”.

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 sent to sampling circuits 32a and 32.
b and 32c, respectively. 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), and it is determined whether or not the level of the output waveform of the binary signal when the sampling clock is input is high level. If the level is high, sample it. That is, the binarized signals of each system are synchronized using the sampling clock as a reference.

The sampled signals are stored as read data in buffers 33a, 33b, and 33c, respectively. This buffer 33a, 33b, 33
Data is stored sequentially in first-in first-out format in c. Each buffer 33a,
The data stored in 33b 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, 32c
The signal sampled at is also sent to the system selection means. Here, each sampling circuit 32
Counting circuits 41a, corresponding to a, 32b, 32c,
High level signals are counted at 41b and 41c. 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. This determination circuit 42 performs a comparison calculation to determine, among the counted values, those that match or are close to a preset mark rate (50% mark rate in this embodiment).

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 FIG. In this case, in the system a for which the threshold value a is set, the mark rate of its binarized output is greater than 50%, and the threshold value c
In the c system with the setting, the mark rate of its binarized output is smaller than 50%. On the other hand, in the b system in which the threshold value b is set, the mark rate of its binarized output is approximately 50%, and the count value closest to the set rate is output.

Therefore, under this condition, an output permission signal is sent to the b-system buffer 34b. 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,
At threshold b of system b, the mark rate does not reach 50%. Therefore, with conventional reading devices, there is a high possibility that FM decoding will be performed incorrectly. However, in this embodiment, the binarized output becomes nearly 50% due to the threshold value a in the former case and the threshold value c in the latter case, so if this is adopted 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 as appropriate in accordance with the mark rate in encoding of the optical recording medium. for example,
It can be 75%, 25%, etc.

Furthermore, in the above embodiment, as the binarization means,
Although three systems a, b, and c are installed in parallel, the system is not limited to this, and four or more systems may be used.

[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 can be dealt with more accurately by using one of the threshold values, and the optical recording information It is possible to read out the data accurately, and also prevents 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 the accuracy limit of the reading device mechanism, distortion of the optical recording medium itself, etc. Even if it is qualitative, it has the effect of being able to respond accurately.

[Brief explanation of the drawing]

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. Waveform diagram showing the method in comparison with another method, the NRZ method, Part 3
The figure 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, 10... CCD linear sensor, 31a, 31b, 31c... Comparator, 3
2a, 32b, 32c...sampling circuit, 33a,
33b, 33c...Batsuhua, 41a, 41b,
41c... Counting circuit, 42... Judgment circuit, 50...
...data bus.

Claims (1)

[Claims] 1. Optical recording information that has been binary-encoded by FM encoding and recorded as an optical pattern on an optical recording medium is photoelectrically read by a reading means, and an output video from the reading means is read. In a video signal binarization method that converts a signal into binary values of high or low based on a threshold value and binarizes the signal, the video signal is distributed to multiple systems, and each system is set with a different threshold value. Binarize as a reference, and in synchronization with a constant sampling signal, sample either high or low states from the binarized signal in each of the above systems, and count the number of each state. Then, compare the count value of each system mentioned above in unit time with the preset mark rate (the proportion of either the high state or low state of the binary code in the FM encoding method), and select the one closest to the set mark rate. A video signal binarization method characterized in that a binarized signal of a system that becomes a count value is used as a regular output signal. 2 Optical recording information that has been binary-encoded using the FM encoding method and recorded as an optical pattern on an optical recording medium is photoelectrically read by a reading means, and the output video signal from the reading means is measured based on a threshold value. A video signal binarization device that converts the video signal into high or low binary values and binarizes the video signal, comprising a plurality of systems of binarization means that binarizes the video signal based on different threshold values, and each of the systems described above. a plurality of systems of temporary storage means for temporarily storing the signals binarized by the binarization means of each system; The proportion occupied by either the low state and the preset mark rate (the proportion occupied by either the high or low state of the binary code in the FM encoding method) are compared, and the high or low state is determined in a unit time. system selection means for instructing the temporary storage means for the system whose ratio 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: