JPH01251431A - Optical information reader - Google Patents

Abstract

PURPOSE:To realize binarization without being affected by the amplitude and the fluctuation of the DC component of a detection signal by making the change direction of an information pattern signal read out by an optical detector into a binary signal, and latching it corresponding to a signal inflection point detection signal. CONSTITUTION:Reflected light corresponding to the recording content of an optical recording medium is read out by the optical detector 1, and is converted to an electrical signal at a photoelectric transducing circuit 2, and is processed at a differentiation circuit 4, and a signal change direction is decided, and is read out at a binarization circuit 6, then, information is binarized. Simultaneously, the output of the circuit 4 is differentiation-processed further at a differentiation circuit 45, and a signal node point is detected, and the output latch of the circuit 6 to a latch circuit 8 is controlled via a zero-cross pulse oscillator 7, then, a binarization read signal is outputted. By employing constitution by the differentiation processing, stable binarization can be performed in spite of the fluctuation of the amplitude and the DC component of an original signal.

Description

[Detailed description of the invention] This invention is an optical card and a compact disk.

The present invention relates to an optical information reading device such as a video disk, and more specifically to an electric circuit for obtaining a binary signal of a reading pattern of information recorded on an optical recording medium.

[Conventional technology]

Various types of optical information reading devices have been proposed in the past. Generally, an information pattern recorded on an optical recording medium is scanned with a light spot, converted into an electrical analog signal by a photoelectric converter, and this analog signal is converted into a binary value and read. A conventional method for binarizing read information patterns will be described below.

FIG. 5 shows a method of comparison with a fixed reference value.

FIG. 5A shows the state of the photoelectrically converted signal, and FIG. 5B shows the binary signal. The signal 9 of the information pattern photoelectrically converted from the photodetector is compared with a preset reference value 10, and if it is larger than the reference value, it becomes "High", and if it is smaller than the reference value, it corresponds to "I, ow" and becomes a binary value. This is a method for extracting signals.

Figure 6 shows the DC component (DC component) from the information pattern signal.
The state diagram of the signal waveform and the binary signal are shown in Fig. 7A,
Indicated by B. A photoelectrically converted signal 15 from the photodetector is sent to a low pass filter (LPF) 13, where a DC component is extracted and a binary reference voltage signal 16 is output.

Based on this binarized reference voltage signal 16, the photoelectrically converted information pattern signal 15 is binarized by the binarization circuit 14, and a binarized signal 17 is output. 2 of the photoelectric conversion signal 15 is determined by the photoelectric conversion signal 15 and its DC component binary reference value.
This is a method to obtain a valued signal 17.

Furthermore, a method of detecting the envelope of a signal of an information pattern using the envelope method will be explained with reference to FIGS. 8 and 9. This is disclosed in Japanese Patent Application Laid-Open No. 56-44974. A photoelectrically converted signal 19 of an optical barcode information pattern expressed in black and white creates black and white envelopes by a white level side envelope circuit 21 and a black level side envelope circuit 22. The midpoint between these two envelope lines is found by the midpoint detection circuit 23, and this is used as the binarized reference signal 20, thereby outputting the binarized signal 25.

[Problems to be Solved by the Invention] However, the amplitude and DC component of the information pattern signal obtained by scanning with a light spot fluctuate due to the influence of various disturbance lights, dirt on the surface of the optical recording medium, fingerprints, etc.

Therefore, the above-mentioned conventional binarization method in which a reference value is provided for such a signal has the drawback that it is not possible to stably binarize the signal in accordance with the original signal due to DC fluctuations.

As shown in the state diagram of the photoelectrically converted signal of the information pattern in FIGS. 5A and 5H, the amplitude and D of the signal of the information pattern
When the C minute changes, waveform 11 of signal 9 that has been charged and converted
The portion should originally be output as a binarized signal 12 (dotted line portion), but since it is lower than the preset reference value 10, it has the disadvantage that it does not become a binarized signal.

Next, extract the DC component from the information pattern signal, and
In the method shown in FIG. 6 in which the C component is used as the reference value for binarization, the relationship between the signal 15 photoelectrically converted by the photodetector and its DC component is as shown in FIGS. 7A and 7H. Now, if the output potential of signal 15 changes intermittently or the same potential continues, D
If the time constant of the C component extraction circuit (integrator) is large, stable 2
Valued signal 17 cannot be obtained. For example, if a long continuous low potential is followed by one short reversal interval, and then a further continuous low or high potential, the DC extracted by the LPF The binarized reference voltage 16 does not follow the high potential of this short inversion period and shows a low potential, and as a result, the signal 18 (dotted line in Figure 8), which should originally be output as a binarized signal, is not output. Defects occur.

This extracts only the AC component of the photoelectric conversion signal 15 and extracts this A
The same problem occurs even if the binarization method uses the zero potential of C as the binarization reference value. The zero potential part is the DC component of the signal 15.
6 (binarization reference value), it also has the same drawback.

Furthermore, in the method shown in Figures 8 and 9, which detects the envelope of a photoelectric conversion signal and converts it into a binary value, the potential must be held by a capacitor in the envelope circuit.If the frequency of the signal is low, this smoothing capacitor has a large capacity. There are drawbacks that make it necessary.

Therefore, it is not suitable for IC implementation.

As described above, the information reading apparatus using the conventional method has the disadvantage that stable binarization cannot be performed depending on the signal state of the information pattern.

An object of the present invention is to provide an optical information reading device that can stably binarize the output of an information pattern from a photodetector even if the amplitude and DC component change.

[Means and effects for solving the problem] In order to achieve the above object, in this invention, light from a light source is irradiated onto an optical recording medium in the form of a spot, and the reflected light is recorded on the optical recording medium. An optical information reading device configured to read an information pattern, comprising: a photodetector for reading the information pattern; a means for expressing a signal change direction of an output signal from the photodetector as a binary signal; It consists of means for obtaining an inflection point detection signal, and means for latching the binary signal with the inflection point detection signal, and detects the direction of change of the signal from the first differential signal of the photoelectrically converted signal and converts it into a binary signal. An inflection point signal is obtained by second-order differentiation, and based on this a binary signal indicating the direction of change, a reliable binary signal can be obtained.

〔Example〕

First, an optical recording medium used in carrying out the present invention, particularly an optical card that the present applicant has succeeded in implementing, will be explained based on FIG. 4.

FIG. 4 is an enlarged view of the recording area of a wallet-sized optical card. A large number of tracks 26 are formed in the recording area extending in the direction of insertion into the optical card league, and seek sections 27a and 27b on which trunk numbers and the like are recorded are formed at both ends of these tracks. At the same time, a data section 2 in which necessary information is recorded is formed between the seek sections. Each track 26 is divided into 19 sections at approximately equal intervals.
It has a book line, and the 10th line counting from the top,
It has a clock pattern 29 for clock generation, focus error detection, and tracking error detection, which is formed of a black pattern at equal intervals and formed over the seek section 27a, the data section 28, and the seek section 27b. Also,
Seek section 27a.

A track number pattern representing the track number is formed on the track 27b, and a fixed recognition pattern common to each track for recognizing this rack number pattern is also formed.

Furthermore, in the data section 28, each track 26 is provided with a plurality of frames 30, and each frame is recognized between adjacent frames and between the seek sections 27a, 27b and the adjacent frames 30. A frame number pattern has been created for this purpose. In this way, in this example, the first to eighth clock patterns above the clock pattern 17 are
The line and the 12th to 19th lines below each constitute an information data byte of 8 bits, and these data can be read simultaneously in synchronization with the black clock pattern 17. In other words, the optical readout amplifier (not shown) has the first to nineteenth sections perpendicular to the track direction.
A total of 19 data bits of the line are captured at once and the image is focused on a plurality of corresponding photodetectors (not shown). Therefore, the optical big amplifier is moved in the direction perpendicular to the track by the seek parts 27a and 27b, and the desired trunk is sought by reading the seek part, and then,
Data section lines 1 to 8 and 12 to 1 of the trunk
By moving the optical card in the track direction to read the information recorded on the 9th line, the 1st to 19th lines can be sequentially read as a group while synchronizing with the clock pattern 17.

FIG. 1 is a block diagram of the basic configuration for obtaining a binary signal according to the present invention. According to an information pattern consisting of light and dark bits of the optical recording medium irradiated from a light source (not shown),
The reflected light beam is received by multiple arrays of photodetectors. These multiple arrays of photodetectors correspond to data section lines 1 to 19 of the laser card recording area, and read out data at once in synchronization with the clock pattern 17. Photodetector 1 represents one of the multiple arrays. The photocurrent is photoelectrically converted by a photoelectric conversion circuit 2 (1-V circuit), and its output is amplified by an amplifier circuit 3. The amplified signal (hereinafter referred to as original signal a) is input to the differentiating circuit 4 and first-order differentiated signal b
Get a signal. This first-order differential waveform is input to the binarization circuit 6, and Hlgh and L are set in advance.

Binarize with the value of W to obtain a d signal. Furthermore, this signal is input to the latch circuit 8 and launched. On the other hand, the b signal output from the differentiating circuit 4 is input to the differentiating circuit 5 to obtain a second-order differentiated C signal. The second-order differentiated C signal is input to a zero-crossing pulse oscillation circuit 7, and a clock pulse signal e is generated at the time of zero-crossing. This clock pulse is inputted to the latch circuit 8 as a human input C signal of the launch circuit 8, and
This serves as a latch timing clock for the signal to be binarized from the differential. By launching the output of the binarization circuit 6 with this clock signal, a binarized signal of the original signal a is obtained.

FIG. 3 is an example of a circuit embodying this basic block diagram. The photocurrent according to the information pattern from photodetector 1 is J-
Photoelectric conversion circuit 2 (1
-V circuit) and undergoes current-voltage conversion, and then outputs an amplified original signal a by an amplifier circuit 3 consisting of an operational amplifier A2. Furthermore, a b signal is obtained by a first-order differentiating circuit 4 comprising a capacitor C1 and a resistor R6. After amplifying this b signal, a differentiator circuit 5 consisting of a capacitor C2 and a resistor R10
After inputting it into the second-order differentiated C signal, the operational amplifier A
Amplify with 4.

The zero-cross pulse oscillation circuit is composed of a pulse generation circuit which is a combination of a zero-cross point binarization circuit of comparator A5 and an RC integration circuit NAND gate, and outputs a clock pulse e signal to a latch circuit. On the other hand, the first-order differentiated b signal is input to a binarization circuit consisting of a comparator A6, which binarizes it at a predetermined zero-crossing point and outputs the d signal to the latch circuit.

The latch circuit consists of a D-FF (flip-flop) that uses the C signal from the pulse generation circuit as a clock and the d signal as an information signal. It becomes f signal.

Next, based on this configuration, the operation will be explained according to the output waveforms of each part in FIG. 2 A to F. FIG. Since this original signal a has a DC component, it exhibits a higher value than OV. FIG.

The waveform of the binary signal obtained by inputting this b signal to the binarization circuit 6 is the d signal shown in the second diagram.

This d signal is a signal indicating the direction of change of the original signal, and is binarized into a high level when the original signal increases and a low level when it decreases.

Since the d signal is obtained by first-order differentiation of the original signal, it has a waveform whose phase is -rad ahead of the original signal a in principle.

Therefore, it is impossible to read information from the d signal using the clock signal of the clock pattern 29 (FIG. 4) of the optical card used in the present invention, which is phase-synchronized with the original signal a, due to this phase advance. The present invention makes it possible to generate a binary signal with no phase lead relative to the original signal a by using the C signal obtained by further differentiating the b signal. FIG. 2C shows the second-order differential signal waveform of the original signal a by the differentiating circuit 5,
The output waveform obtained when this C signal is manually applied to the zero-cross pulse oscillation circuit 7 is the C signal shown in FIG. 2E. This C
The time of pulse oscillation of the signal indicates the inflection point of the waveform of the original signal a.

241 waveform in Fig. 2F [The signal is the output d of the binarization circuit 6]
The signal is launched using the C signal of the zero-cross pulse oscillation circuit 7 as a clock signal. The f signal indicates the d signal at the instant of the rise of the human clock C signal. This f signal is a faithful binary signal of the original signal a.

As described above, according to this embodiment, it is possible to effectively remove the DC component superimposed on the photoelectric conversion output signal due to fluctuations in the reflective surface of the optical recording medium and the influence of ambient light. Furthermore, it is possible to provide a stable binarization circuit without changing the phase even for a signal where the maximum inversion interval of the information data signal is several hundred n5ec, which is several thousand times the minimum pinch interval.

That is, in a binarization method using only first-order differentiation, the binarized signal theoretically advances by -rad, so accurate information data may not be readable. , 2 of the original signal with no phase shift
It became possible to obtain a valued signal.

〔Effect of the invention〕

As described above, according to the present invention, the original signal from the photodetector is differentiated to the first order, the direction of change is differentiated to the second order, and the point of inflection is detected, and based on this information, the original signal is differentiated. 2 (i
To obtain a binary signal that is stable and synchronized with the original signal, regardless of fluctuations in the amplitude and DC component of the original signal, and without being affected by changes in amplitude due to information data patterns. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the basic configuration according to the present invention. FIGS. 2A to 2F are diagrams showing signal waveforms at various parts in the configuration of FIG. 1. FIG. 3 shows the configuration of an example that embodies the block diagram of FIG. 1. FIG. 4 is an enlarged view of the recording area section of the optical card. FIG. 5 to FIG. 9 are diagrams showing conventional examples. 1.--.-Photodetector 2.--.--Photoelectric conversion circuit (
1-V) 3--m-amplifier circuit 4.5-differentiator circuit 6--binarization circuit 7--zero cross pulse oscillation circuit 8--launch circuit 29--cross pattern procedure block l Authorized (spontaneous) July 72, 1986 Director General of the Patent Office Yoshi 1) Mr. Moon Yi
1. Indication of the case Patent Application No. 80104 of 1988 2. Title of the invention Optical information reading device 3. Person making the amendment (voluntarily) (1) Description from line 420 to page 5 1 At the beginning of the line, "DC component extraction circuit (integrator) j is rDC component extraction circuit (L, PF)
Add to J. (2) Lines 13 to 14 of page 5 indicate rDC min 16 (binarization standard value), so j is rDC min 1
6 (binarization reference value) and is corrected to J, which corresponds to the same operation. (3) Compensate "this rack number pattern" in lines 2 to 3 of page 8 with "this track number pattern J." (4) Compensate "clock pattern 17J" in lines 10 to 11 of page 8 with "this track number pattern J." Correct it to "two clock patterns." (5) "Clock pattern 17J on page 8, line 14 is corrected to "clock pattern 29J." (6) "Clock pattern 17J on page 9, line 6 is corrected as "clock pattern 29J."
Clock pattern 29". (7) On page 9, lines 15 to 16, [Tarlock pattern 17J is corrected to "clock pattern 29." (8)Amend Figure 7 in the drawings as shown in the attached sheet. Old figure 7

Claims (1)

[Claims] 1. Irradiate the optical recording medium with light from a light source in the form of a spot,
An optical information reading device that reads an information pattern recorded on the optical recording medium from the reflected light includes a photodetector for reading out the information pattern, and a signal change direction of an output signal from the photodetector. An optical information reading device comprising means for expressing a binary signal, means for obtaining an inflection point detection signal of the output signal, and means for latching the binary signal using the inflection point detection signal. .