JPH0381222B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup position control method for a video disc player for controlling the pickup position of a video disc player, and an object of the present invention is to improve the accuracy of pickup position control.

In general, video discs and video disc players, which are playback devices for the discs, are being developed from the viewpoint of high information storage density and short access time.

For example, in an optical video disk player, in order to shorten access time, a linear motor consisting of a magnet, a yoke, and a coil installed in a magnetic gap between the magnet and the yoke is moved in the radial direction of the disk. an optical pick-up and a detection object are attached to the linear motor, a current is applied to a coil of the linear motor, the linear motor is moved, and the pick-up is moved, and at the same time, the position of the linear motor or the pick-up is changed with a potentiometer. The pickup is detected by a linear encoder such as a meter, and the amount of movement of the linear motor is controlled based on the signal from the linear encoder to move the pick-up a predetermined amount to move the pick-up near a predetermined track to be aligned. After that, the detection body detects a deviation between the predetermined track to be aligned and the pickup, and the linear motor is slightly moved so that the output signal from the detection body becomes zero. It is then aligned and fixed to the predetermined track.

However, in this case, the detection accuracy of the detection object directly becomes the position control accuracy of the pickup, and conventionally the detection accuracy of the detection object is about several μm.
If the pick-up cannot be aligned, and even if the pick-up deviates from the predetermined track due to external vibrations, the deviation of the pick-up cannot be detected, and the pick-up cannot be fixed to the predetermined track. The disadvantage is that it cannot be done.

The present invention has been made with the above points in mind, and moiré fringes are formed by a fixed grating and a moving grating having the same grating interval as the fixed grating and disposed at an angle with respect to the fixed grating. The movable grating is moved along the fixed grating, and four sensors arranged at predetermined intervals detect changes in the brightness of the moiré fringes obtained by the movement of the movable grating, and each of the sensors outputting first to fourth detection signals in the form of sinusoids whose phases are sequentially delayed by 90 degrees from , and shaping the respective detection signals by a waveform shaping section to output first to fourth command signals in the form of rectangular waves;
During each high level period of each of the command signals,
With respect to the detection signal corresponding to the command signal that is at a high level, the control unit calculates a difference signal between the detection signal with a 90° delayed phase and the detection signal with a 90° advanced phase, and The present invention provides a pickup position control method for a video disc player, characterized in that the difference signal is outputted to a pickup moving motor as a control signal, and the pickup position is controlled by the output.

Therefore, according to the pick-up position control method for a video disc player of the present invention, a position control signal having a wavelength of 1/4 of the length of each sensor can be outputted from the control section, and By shortening the installation length, it becomes possible to easily output a position control signal with a short wavelength, and it is possible to improve the accuracy of position control of the pickup.

Next, the present invention will be described in detail with reference to drawings showing one embodiment thereof.

First, as shown in FIG. 1, a plurality of chromium films 1b each having a width of 20 μm are pasted on the surface of a long glass substrate 1a at intervals of 20 μm to form a fixed grating 1. The movable grating 2 is formed by pasting a plurality of 20 μm wide chromium films 2b with the same grating spacing as the fixed grating 1, that is, 20 μm spacing, and the movable grating 2 is placed in front of the fixed grating 1 as shown in FIG. As shown in FIG.
is arranged on the front side of the movable grating 2 so as to be perpendicular to the chrome film 1b of the fixed grating 1, and the light from the light source 5 consisting of a collimator, lens, etc. arranged on the rear side of the fixed grating 1 is The light is projected onto the grids 1 and 2 to generate moiré fringes consisting of light and dark stripes on the mounting plate 3 and each sensor 4a to 4d.

At this time, if the inclination of the movable grating 2 with respect to the fixed grating 1 is large, the pitch of the moiré fringes becomes small and the interval between the bright and dark stripes becomes narrow; conversely, if the inclination of the movable grating 2 with respect to the fixed grating 1 is small, As the pitch of the moire fringes becomes larger and the interval between the bright and dark fringes becomes wider, the pitch of the moire fringes becomes equal to the arrangement length of each sensor 4a to 4d of 40 μm, as shown in FIG. 1b. , the inclination of the movable grating 2 with respect to the fixed grating 1 is adjusted in advance.

Next, after adjusting the inclination of the movable grating 2, when the movable grating 2 is moved along the fixed grating 1 and the mounting plate 3 and the light source 5 are linked to the movable grating 2, each sensor 4a to 4d detects moiré patterns. As shown in FIG. 2a, the first to fourth detection signals A to A in the form of sinusoidal waves with a wavelength of 40 μm and whose phases are sequentially delayed by 90 degrees from each sensor 4a to 4d are detected.
D, and as shown in FIG. 3, the first to fourth comparators 7a to 7d of the waveform shaping unit WS each have a non-inverting input terminal (+) connected to a reference signal source via a connection terminal 6. Each of the detection signals A to D is input to the inverting input terminal (-) of the , and each of the comparators 7a to 7d determines the reference level of the level connecting each of the detection signals A to D and the positive intersection of each of the detection signals A to D. When the reference signals from the signal sources are compared and each of the detection signals A to D is larger than the reference signal indicated by the dashed line in FIG. 4 comparison signals are output, each of the comparison signals is input to one input terminal of the first to fourth AND gates 8a to 8d of the waveform shaping section WS, and each of the comparison signals is input to one of the input terminals of the first to fourth AND gates 8a to 8d of the waveform shaping section WS. The detection signals A to D are input to the other input terminals of the third, fourth, first, and second AND gates 8c, 8d, 8a, and 8b via the first to fourth inverting circuits 9a to 9d, and each detection signal A to D is waveform-shaped. As shown in FIGS. 2b to 2e, the AND gates 8a to 8d output rectangular waveform first to fourth commands that become high level when each detection signal A to D is larger than the reference signal, respectively. Signal W,
X, Y, and Z are output.

Further, resistors 10a to 10d and 1
First to fourth operational amplifiers (hereinafter referred to as OF-amps) 1 which together with 0a' to 10d' constitute the first to fourth subtraction circuits 11a to 11d of the control unit CC.
The first, fourth, third, and second detection signals A, D, C, and B are connected to the inverting input terminals (-) of 2a to 12d, respectively.
is input to the non-inverting input terminal (+) of each operational amplifier 12a to 12d, respectively.
While the fourth detection signals C, B, A, and D are input, the first to fourth electronic switches 13a of the control section CC
The fourth, third, second, and first command signals Z, Y, X, and W are input to 13d and 13d, respectively, and the signals e, d, and
During the respective high level periods of the fourth to first command signals Z to W as shown in c and b, the respective electronic switches 13a to 13d are turned on in sequence, and
The fourth to first command signals Z, Y, which are at high level
With respect to the fourth to first detection signals D, C, B, and A corresponding to X and W, respectively, detection signals A, D, C, and B with a 90° delayed phase and detection signals C, with a 90° advanced phase, respectively. Difference signals with each of B, A, and D are calculated by each subtraction circuit 11a to 11d and output.

That is, when the fourth command signal Z is at a high level, the difference signal S1 between the first and third detection signals A and C calculated by the first subtraction circuit 11a is at a high level, and when the third command signal Y is at a high level, the difference signal S1 is at a high level. If the second command signal If the first command signal W is at a high level, the difference signal S3 between the signals C and A becomes the difference signal S4 between the second and fourth detection signals B and D calculated by the fourth subtraction circuit 11d.
However, each switch 13a to 13 is in an on state.
d, the signal is sequentially outputted as a position control signal S to a pick-up moving motor such as a linear motor as described above.

At this time, although not shown, the output state of the position control signal S from the control unit CC to the motor is determined by the output control circuit to be only the difference signal, the difference signals S1 and S1, or the difference signals S1, S2, S3, S4. ,S
1, etc., and the motor moves the pickup by an amount corresponding to the input position control signal.

As described above, by making the pitch of the moiré fringes equal to the length of each sensor 4a to 4d, the wavelength of each detection signal A to D becomes 40 μm, and each high signal of each command signal W to Z becomes 40 μm. The level period is 1/4 of the period of each detection signal A to D, and the wavelength of the position control signal S is 10 μm, so that each sensor 4a
~4d is 1/4 of the installation length, so each sensor 4a
By shortening the arrangement length of ~4d, the wavelength of S of the position control signal becomes shorter. For example, by shortening the arrangement length of
By setting it to 4 μm, it becomes possible to easily obtain a position control signal S with a wavelength of 1 μm.

Therefore, according to the embodiment, each sensor 4
A position control signal with a wavelength of 1/4 of the length of the sensors 4a to 4d can be output from the control unit CC, and by shortening the length of each of the sensors 4a to 4d, the position control signal with a short wavelength can be output. can be easily output, and the accuracy of pickup position control can be improved.

[Brief explanation of drawings]

The drawings show an embodiment of the pick-up position control method for a video disc player according to the present invention, in which FIG. FIG. 2 is a perspective view of the moving grating and the sensor, FIGS. 2a to 2e are waveform diagrams of each detection signal and each command signal, FIG. 3 is a wiring diagram of the waveform shaping section, and FIG. 4 is a wiring diagram of the control section. DESCRIPTION OF SYMBOLS 1... Fixed grating, 2... Moving grating, 4a-4d... 1st - 4th sensor, WS... Waveform shaping part, CC... Control part.

Claims (1)

[Claims] 1. Forming moiré fringes by a fixed grating and a movable grating having the same grating interval as the fixed grating and disposed obliquely with respect to the fixed grating, moving the movable grating along the fixed grating, and Changes in the brightness of the moiré fringes obtained by the movement of the moving grating are detected by four sensors arranged at predetermined intervals. 4 Output the detection signal,
A waveform shaping section shapes each of the detection signals to output rectangular waveform first to fourth command signals, and during each high level period of each of the command signals, the first to fourth command signals corresponding to the high level command signal are output. A control unit calculates a difference signal between the detection signal with a phase delay of 90° and the detection signal with a phase lead of 90° with respect to the detection signal, and the control unit uses the difference signal as a position control signal to drive a motor for pick-up movement. 1. A pickup position control method for a video disc player, characterized in that the pickup position is controlled by the output.