JPS6028070B2 - position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a track of a reproducing transducer used when reproducing periodic signals recorded in the form of a large number of parallel recording traces (hereinafter referred to as tracks) on a video disc or the like. The present invention relates to a position detection device.

FIG. 1 is a diagram showing a conventional video disc player, and an automatic tracking method for a conventional video disc player will be explained with reference to FIG. In FIG. 1, a light beam generated from a laser 1 is transmitted through a diffusing lens 2, a diffraction grating 3, a beam splitter 4, a 1'4^ plate 5, and a deflection mirror 6.
, passes through a condensing lens 7 and is condensed in the form of a spot onto a rotating disk 8. The light reflected by the disk 8 passes through the condenser lens 7, the polarizing mirror 6, and the 1/4^ plate 5 again, is reflected laterally by the beam splitter 4, and is imaged on the light receiving elements 9, 10, and 11. If a voltage related to information recorded in the form of irregularities or holes on the track is obtained from the light receiving element 9, it is applied to the reproduced signal processing circuit 13 through the amplifier 12.

The outputs of the light receiving elements 10 and 11 are applied to a power amplifier 14. The output of this differential amplifier 14 is applied to the deflection mirror 6. On the other hand, FIG. 2 is a diagram showing a part of a conventional video disc. Reference numeral 15 in FIG.
b, 16c, . . . are formed in the form of a large number of spirals or concentric circles.

Information is recorded on these tracks 16a, 16b, . . . . FIG. 3 is an enlarged view of the video disc 15 shown in FIG.

FIG. 3 shows beam spots 17-19 projected onto a disc when the disc is played by a conventional video disc player. And the first
Due to the action of the diffraction grating 3 of the video disc player shown in the figure, beam spots 17, 18, 19 are formed on the disc 15.
is projected, and the beam spot 18 is the beam spot 17.
On the other hand, in the track radial direction, for example, the beam spot 19 is slightly offset toward the inside, and conversely, the beam spot 19 is slightly offset toward the outside with respect to the beam spot 17. Due to the deflection mirror 6, the beam spots 17, 18, 19 can be moved radially on the disk surface, but their mutual positions remain unchanged. In FIG. 1, it is assumed that beam spots 18 and 19 are imaged on the light receiving elements 10 and 11, respectively.

Due to the operation of the operational amplifier 14 connected to the light receiving elements 10 and 11, the difference in output between the light receiving elements 10 and 11 is supplied to the deflection mirror 6.
It stabilizes to the point where the output of 1 is balanced. At this time, the beam spots 18 and 19 are, for example, at symmetrical positions with respect to the center line of the track 16a, as shown in FIG. Since the beam spots 17, 18, and 19 move on the disk with a constant mutual relationship, the beam spot 17 is on the center line of the track in a stable state, and the light receiving element corresponding to the beam spot 17 records information on the track 16. A signal was obtained in good condition. The above-mentioned operation is called automatic beam spot tracking, and even if there is eccentricity or track distortion when the disk 15 rotates,
This function is necessary for the playback beam spot to follow a certain track.

As mentioned above, the secondary video disc player is equipped with a diffraction grating 3, as shown in FIG. 1, for automatic tracking.
The photodetectors 10 and 11 are provided, which is expensive and
The three beam spots must have a special positional relationship with respect to the track, and the beam spots must be focused on the three light-receiving elements provided for each, and the optical system must be The cost of video disc players was high because high precision was required and labor was required for adjustment.

The present invention provides a position detection device that does not require such complicated parts, can have low machining accuracy, and can reduce adjustment labor.

Embodiments of the position detection device of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram showing tracks of a video disc applied to one embodiment, and FIG.
FIG. 3 is an enlarged view of the truck shown in the figure. Reference numerals 20 to 24 in FIGS. 4 and 5 are tracks, respectively, and as shown in FIG. 4, these tracks are D-circular or spiral-shaped. Each track records a television signal in the form of FM modulation. As for the modulation method, the instantaneous frequency is sHZ at the beginning of the periodic signal, pHZ at the vedestal, and WHZ at the white level.In track 20, 26 to 29 are the frequencies corresponding to the ends of the horizontal synchronization signal of the television signal. This is where the SHZ is recorded, and this is called the synchronous part.

Such cases exist periodically over the entire circumference of the track. Tracks 21 to 24 are also recorded at the frequency 〆SHZ, and if the number of rotations of the disk is kept constant, the synchronous parts of each track are almost in a straight line in a narrow range, as shown by the dotted line. . Also, track 2
0 synchronous parts 25-29 are arranged at equal angles to the center of the disc, and tracks 21-2
The same applies to 4.

Let QH be the angle formed with the center of these adjacent synchronous parts. Next, if the angle between the synchronization signal 25 of track 20 and the synchronization portion 30 of the adjacent track 21 with respect to the center of the disk is QD, then two adjacent synchronization portions on different adjacent tracks The angle formed with the center is QD everywhere on the disk surface.

The beam spot 38 is stationary, but when looking at the synchronous part on the rotating disk from this beam spot, the synchronous part of the track 22 and the synchronous parts of the adjacent tracks 21 and 23 are the same as the beam spot. The time relationship of passing through the area is such that the time difference and the angle with respect to the center are proportional.

Further, QH corresponds to the horizontal scanning period. track 21
, 22, 23 is shown in an enlarged manner in FIG. 5. In FIG. It is 〆sHZ.

The instantaneous frequencies of other parts of the track are NapHZ and NawHZ
It's between. 38 in Figure 4 is the only one necessary for reproduction.
As shown in the figure, if the diameter is D, the middle of the track is w, and the track interval is p, the diameter D is slightly larger than (w+), and the center of the beam spot is When in the center of a track, the beam spot 38 shall also illuminate parts of two adjacent tracks.

Now, assuming that the number of rotations of the disk is N times per second, consider a period of time td seconds. FIG. 6 shows a block diagram of an automatic tracking circuit for a video disc player using a position detection device according to the present invention.

In this FIG. 6, 39 is a light receiving element, and this light receiving element 39 outputs a voltage according to the change in reflection intensity of the beam spot 38, and after amplifying the output by an amplifier 40, it is passed through a limiter 41 to an FM demodulator 42. Thus, a video signal can be obtained at the output terminal 55. This FM
The video signal obtained by the demodulator 42 is applied to a horizontal synchronous separation circuit 43, and the output of this horizontal synchronous separation circuit 43 is applied to delay circuits 44 and 45.

The respective delay times are td and (th, 1). However, th is the horizontal scanning period. The pulse shown in FIG. 7B5 is the output pulse of the horizontal synchronization separation circuit 43,
The pulse shown in FIG. 7B6 is the output pulse of the delay circuit 44. FIG. 7B7 shows the output pulses of the delay circuit 45. On the other hand, a part of the output of the amplifier 40 is applied to the input of a bandpass filter 46, and the center frequency of this bandpass filter 46 is
It is HZ.

FIG. 7 (BI) to FIG. 7 (B4) show the output waveform of this bandpass filter 46. In addition, Fig. 7 (AI) to Fig. 7 (A4) show the positional relationship between the beam spot and the track, of which Fig. 7 (AI) shows the center of the track 58 where the beam spot is located. indicates when the
The output waveform of the bandpass filter 46 at this time is as shown in FIG. 7 (BI).

At this time, the burst 64 is on track 5 in FIG. 7 (AI).
Bursts 63 and 65 correspond to synchronous parts 62 and 60, respectively. burst 63,6
5, since the beam spot 56 slightly illuminates the tracks 57 and 59, it is sufficiently smaller than the burst 64, and as a result, the reproduced signal is transmitted to the IJ emitter 41 and the demodulator 4 in FIG.
Even if demodulated through 2, due to the predatory phenomenon peculiar to FM,
Interference by adjacent track signals can be ignored. Further, in FIG. 7 (A2), the beam spot is located slightly below the center of the track 58, compared to FIG. 7 (AI).

At this time, the output waveform of the bandpass filter 46 becomes as shown in FIG. 7 (B2). At this time, the size of the burst 64 is almost the same as in the case of FIG. 7 (BI), but since the beam spot irradiates the track 59 more strongly than the track 57, the burst 63 becomes larger than the burst 65. Furthermore, FIG. 7 (A3) shows a case where the beam spot is located slightly above, contrary to FIG. 7 (A2), and at this time, the output of the bandpass filter 46 becomes as shown in FIG. 63 is smaller than burst 65. 7th
The pulses shown in FIG. 7 (B5), FIG. 7 (B6), and FIG. 7 (B7) are momentarily aligned with the bursts 64, 63, and 64, respectively. The output of the bandpass filter 46 is AM
After passing through the detector 47, as shown in FIG.
8 and gate 49, and are applied to sample and hold circuits 50 and 51, respectively. gate 48
is turned on by the pulse shown in FIG. 7 (B6), and gate 4
9 is turned on by the pulse shown in FIG. 7 (B7), so that the sample and hold circuits 50, 5
The outputs of 1 are voltages representing the magnitudes of bursts 65 and 63 shown in FIGS. 7BI to 7(B3), respectively.

Further, as described above, the beam spot 56 is located on the track 5.
The sizes of the bursts 65 and 63 change complementary to each other depending on whether they are located below or above the center line of 8, as shown in FIG. 7 (AI) to FIG. 7 (A3). As a result, the outputs of the sample and hold circuits 50 and 51 also change differentially.

The outputs of the sample and hold circuits 50 and 51 are connected to the switching amplifier 5.
2. ．． Therefore, as the outputs of the sample and hold circuits 50 and 51 change differentially, the output of the differential amplifier 52 also changes between positive and negative. In other words, the output voltage of the duty amplifier 52 represents the positional relationship between the beam spot 56 and the track 53, and this operation is the same as that of the conventional differential amplifier 14 shown in FIG. The output of the differential amplifier 52 is amplified by a power amplifier 53 and then drives a deflection mirror 54. FIG. 8 shows an overall block diagram of a video disc player to which the position detection device of the present invention is applied.

The output of the light receiving element 39 is amplified by an amplifier 401 and applied to a processing circuit 66. The inside of the processing circuit 66 corresponds to the portion 66 surrounded by the dotted line in FIG. 67 is the output end of the amplifier 53 in FIG. 6, and its output is applied to the deflection mirror 54, so that the beam spot moves radially around the disk and traverses the track. the result,
The output of the differential amplifier 52 is changed, an automatic tracking loop is formed, and the beam spot is stabilized on the center line of the track, as shown in FIG. 7 (AI), and a high quality signal is reproduced by this spot. When considering the case where the beam spot 56 is located halfway between the tracks 56 and 59 as shown in FIG. This is then converted to F by the limiter 41 and demodulator 42.
In the case of M demodulation, the signals of the tracks interfere with each other and a correct signal cannot be obtained.

For this reason, the horizontal synchronization separation circuit 43 does not operate correctly and the automatic tracking loop is unstable, but due to eccentricity of the rotating disk and noise in the circuit, the beam spot 56
Since the state shown in Fig. 7 (AI), Fig. 7 (A2), or Fig. 7 (A3) is quickly reached, the automatic tracking action immediately operates as described above and the beam spot stabilizes at the center of the track. and track it. It should be noted that various modifications can be made to the above-described embodiments without departing from the spirit of the invention.

Furthermore, the present invention can be applied even if there are a plurality of reproduction beam spots or light receiving elements as in the prior art. And the sixth
In the figure, a bandpass filter 46, an AM zero wave detector 4
Gates 48 and 49 are not placed after 7, and gates 48 and 49 are
After that, a bandpass filter 46 and an AM detector 4 are installed.
7 may be provided. Furthermore, in FIG. 4, the beam spot law D may be smaller than (w+?), and (w+p
) It may be slightly larger in the evening.

Also, even if it is larger than (w+2p), (3W+?)
It is fine if it is smaller. Regarding the diameter of the spot, in order to apply this invention, there is one main track and one or two secondary tracks irradiated by one spot, and the synchronization signal obtained from the main track is 0. This is because it is only necessary to select the synchronizing signal of the subordinate track and detect the amplitude of its carrier wave. Applicable signal is also FM
Not limited to demodulation, when there is crosstalk or crosstalk from adjacent tracks, and when the magnitude of the crosstalk is relatively small, other signals may be used as long as they are not adversely affected so much. QD in FIG. 4 may be of any size as long as it is a multiple of 1/2 of QH. The signal to be recorded is not limited to a television signal, and the present invention can be applied to any signal such as a synchronization signal that has a portion that takes a synchronously constant value, frequency, or pulse pattern. Furthermore, the reproducing device is not limited to one that reproduces an optical or mechanical track pattern using a laser beam; for example, a magnetization pattern or other chemical or physical pattern may be used. It is not limited to a light receiving element, but may also be a piezoelectric element, a magnetic head, an electromagnetic pickup, or a capacitive detector.

The shape of the recording medium is not limited to a disk, but may also be a card, sheet or tape cylinder, and the arrangement of tracks is not limited to the same D circle or spiral, but can be arranged in any other way as long as it has a partially parallel line shape. It can also be a form. The transducer and media motion may be one fixed and the other moving, or both may be moving. As detailed above,
Conventional video disc players require a complicated optical system as shown in FIG. 1 in order to detect the relationship between the beam spot and the track, but according to the present invention, this is not necessary. Something like the one shown in FIG. 8 is sufficient, and the configuration becomes extremely simple. Furthermore, compared to conventional position detection devices, only one beam spot is required on the disk, so a diffraction grating is not necessary, and only one light receiving element is required.

Therefore, the number of parts is reduced compared to the conventional method, and less technology and time are required for adjustment, so that an inexpensive position detection device can be provided.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing a conventional automatic tracking device for a video disc player, Fig. 2 is a plan view showing a part of a subordinate video disc player, and Fig. 3 is a system diagram showing a conventional automatic tracking device for a video disc player. 4 is an enlarged view showing the relationship between the beam spot and the track. FIG. 4 is an enlarged view of the track of a video disc player applied to the position detection device of the present invention. FIG. 5 is an enlarged view of the video disc player of FIG. 4. FIG. 6 is a block diagram showing the configuration of the processing circuit in the position detection device of the present invention, and FIG. 7 is an enlarged view of a part of the track of FIG.
7 (B7) are the sixth graphs for the positional relationship between the tracks of the video disc player and the beam spot, respectively.
FIG. 8 is a diagram showing the output waveform of the bandpass filter in the processing circuit shown in the figure, and FIG. 8 is a system diagram showing the configuration of the position detection method of the present invention. 1...Laser, 4...Beam splitter, 8...Video disk player, 20-24""" track, 25-
33, 35-37...Synchronized part, 39...
Light receiving element, 40...Amplifier, 41...
Limiter, 42...FM demodulator, 43...
...Horizontal synchronization separation circuit, 44, 45...Delay circuit, 46...Band pass filter, 47...
...AM detector, 48, 49...gate, 50, 51
...Sample and hold circuit, 52...Differential amplifier,
54... Deflection mirror, 60... Processing circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 1 Figure 2 Figure 3 Dimensions of the ship Figure 7 of the ship Figure 8

Claims (1)

[Claims] 1. At least a portion of a plurality of pieces in which periodic information is recorded have approximately parallel recording traces, and a periodic signal portion is provided on the recording traces, and a single reproducing transducer is used to generate adjacent recording traces. When the two above-mentioned recording traces are simultaneously reproduced, the periodic signal portion of each recording trace is reproduced with a certain time lag, and the direction of the time lag is the same as that of one adjacent recording trace when viewed from the predetermined recording trace. The adjacent recording trace on the opposite side corresponds to the periodic signal portion from the recording trace with the largest reproduction output signal among the plurality of recording traces reproduced by the single transducer. a means for obtaining a signal and extracting a periodic signal portion of an adjacent recording trace using the signal as a reference; and a reproduction transformer in a direction intersecting the recording trace from the reproduced intensity of the periodic signal portion extracted by this means. A position detection device comprising means for detecting the position of a deuser. 2. The position detection device according to claim 1, wherein the reproducing transducer uses a light receiving element that converts a light spot into an electrical signal. 3. The position detection device according to claim 1, wherein the reproducing transducer uses a piezoelectric element. 4. The position detection device according to claim 1, wherein the reproducing transducer uses a magnetic head. 5. The position detection device according to claim 1, wherein the reproducing transducer uses an electromagnetic pickup. 6. The position detection device according to claim 1, wherein the regenerative transducer uses a capacitive detector. 7. The position detection device according to claim 1, wherein the recording medium is a video disc.