JPH058498B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a focusing device that automatically performs focusing in an optical disk reproducing device such as a laser disk device.

Prior Art and Problems In an optical disc playback device such as a laser disk device, light is irradiated onto a recording medium such as a laser disk, and the reflected light from the recording medium is made to enter a light receiving element via a lens. This allows the recorded contents of the recording medium to be reproduced. In this case, in order to accurately reproduce the recorded content, it is necessary to keep the light receiving element always in focus with respect to the recording medium. For this reason, optical disc playback devices have conventionally provided a focusing servo loop to control the relative position between the recording medium and the lens, so that the light receiving element is always in focus on the recording medium during playback. That's what I do. However, in the focusing servo loop described above, if the deviation from the in-focus state is large, that is, if the deviation from the in-focus state is outside the retraction range of the focusing servo loop, the light receiving element is moved toward the recording medium. It was impossible to bring it into focus.

Therefore, in the past, an initial focus adjustment device was provided in addition to the focusing servo loop, and the initial focus adjustment device was used to cause the light receiving element to adjust the servo loop to the recording medium before starting playback of the recording medium (for example, when the power was turned on). The focus is kept within the pull-in range, and then controlled by a focusing servo loop.

Various types of initial focus adjustment devices have been proposed in the past, for example, by irradiating light onto a recording medium and moving a lens upward or downward.
A method has been proposed in which the movement of the lens is stopped when the level of the output signal of the light receiving element reaches a reference level. However, this conventional device had the following drawbacks. That is, since the amount of light reflected from the recording medium changes depending on temperature changes and the tilt angle of the recording medium, it is difficult to set the reference level.

In addition, there has been proposed a device that irradiates the recording medium with light, moves the lens upward or downward, and stops the movement of the lens when the level of the output signal of the light-receiving element reaches its maximum value. Although,
In order to detect the maximum value, it is necessary to detect that the level of the output signal of the light-receiving element begins to decrease, so there is a drawback that accurate focusing is difficult. In this case, if the moving speed of the lens is made slow, accurate focusing becomes possible, but there is a drawback that the time spent on focusing increases.

Additionally, a system has been proposed that detects the presence or absence of a playback signal while moving the lens upward or downward, and stops the movement of the lens when the presence of the playback signal is detected, but this method requires rotating the recording medium. Since a reproduced signal cannot be obtained and focusing cannot be performed until the rotation of the recording medium becomes stable, there is a drawback that focusing cannot be performed quickly.

OBJECTS OF THE INVENTION The present invention has been made to improve the above-mentioned drawbacks, and its purpose is to enable accurate and rapid focusing.

Configuration of the Invention FIG. 1 is a configuration diagram of the first invention. The light receiving element 30 receives the recording medium 3 through the lens 31.
Converts the reflected light from 2 into an electrical signal. The first signal generating means 33 outputs a first signal that causes the lens 31 and the recording medium 32 to move relatively, and the second signal generating means 34 outputs a first signal that causes the lens 31 and the recording medium 32 to move relative to each other.
The superimposing means 35 superimposes the first signal and the second signal, and the moving means 36 moves the lens based on the output signal of the superimposing means 35. 31 and the recording medium 32 are moved relatively. Bandpass filter 37
passes the frequency 2 component of the output signal of the light receiving element, and the determining means 38 is a bandpass filter 37.
When the power is turned on, the control means 39 determines whether the level of the output signal of the bandpass filter 37 is equal to or higher than a predetermined level. ,
The lens 31 and the recording medium 32 are moved relative to each other by the output signal of the superimposing means 35.

FIG. 2 is a block diagram of the second invention. The light receiving element 30 receives the recording medium 3 through the lens 31.
Converts the reflected light from 2 into an electrical signal. The first signal generating means 33 outputs a first signal that relatively moves the lens 31 and the recording medium 32, and the second signal generating means 34 outputs a first signal that relatively moves the lens 31 and the recording medium 32. A second signal that causes minute vibrations is output, and the first superimposing means superimposes the first signal and the second signal. The feedback signal creating means 40 creates a feedback signal based on the output signal of the light receiving element 30, and the second superimposing means superimposes the second signal and the feedback signal. The switching means 42 applies one of the output signals of the first and second superimposing means 35 and 41 to the moving means 36.
The moving means 36 relatively moves the lens 31 and the recording medium 32 based on a signal applied via the switching means 42. The band pass filter 37 passes the frequency 2 component of the output signal of the light receiving element 30, and the determining means 38 passes the frequency 2 component of the output signal of the light receiving element 30.
It is determined whether the level of the output signal is equal to or higher than a predetermined level. When the power is turned on, the control means 43 controls the switching means 42 when the determination means 38 determines that the level of the output signal of the bandpass filter 37 is higher than a predetermined level, so that the moving means 36
When the recording medium 1 is reproduced, the determination means 38 determines whether the level of the output signal of the bandpass filter 37 is below a predetermined level. If it is determined that
is switched to the output signal of the first superimposing means 35.

Embodiment of the invention FIG. 3 is a block diagram of an embodiment of the invention.
is a recording medium such as a laser disk, 2 is a lens, 3 is a recording medium such as a laser disk, etc.
is a beam splitter, 4 is a light emitting element, 5 is a light receiving element, 6 is a bandpass filter that passes the signal of frequency 2, 7 is an amplifier, 8 is a detection circuit, 9 is a comparator, 10 is a microprocessor, 11 is a memory,
12 is an input section, 13 is an output section, 14 is a compensation circuit that performs amplification, phase compensation, etc., 15 is an oscillator that outputs the sine wave signal a shown in FIG. 4A, and 16 is FIG. 4B
17 is a superimposition circuit that superimposes the output signal of the compensation circuit 14 and the output signal a of the oscillator 15; 18 is the oscillator 15, 1;
A superimposition circuit 19 superimposes the output signals a and b of 6 and outputs the signal c shown in FIG.
When the signal e is "0", the switching circuit is connected to the contact B side, and 20 is a drive circuit for the motor 21 that moves the lens 2 in the vertical direction. The lens 2 is placed at a corresponding position. Further, FIG. 5 is a flowchart showing an example of the processing contents of the microprocessor 10.
The operation of the diagram will be explained.

When the microprocessor 10 is powered on, a control means is added to the output section 13 to set the output signal e to "1" (step S1). This results in
The switching circuit 19 is connected to the contact A side, and the oscillator 15
A signal c, which is a superposition of the frequency signal a output from the oscillator 16 and the sawtooth wave b output from the oscillator 16, is applied to the drive circuit 20 via the switching circuit 19.
As described above, the drive circuit 20 is for disposing the lens 2 at a position corresponding to the level of the signal applied via the switching circuit 19, so the output signal c of the superimposition circuit 18 is applied to the drive circuit 20. As a result, the lens 2 moves upward or downward while vibrating minutely at the frequency.

Incidentally, the amount of reflected light from the recording medium 1 that enters the light receiving element 5 via the lens 2 and the beam splitter 3 changes as shown by curve A in FIG. 6 depending on the position of the lens 2. It is. however,
In the figure, the horizontal axis indicates the distance of the lens 2 from the focal point, and the vertical axis indicates the amount of light. Therefore, by slightly vibrating the lens 2 at a frequency as described above, when the lens 2 is located above the focal point, the amount of reflected light incident on the light receiving element 5 is changed as shown by curve B in the figure. When the lens 2 is below the focal point, the amount of reflected light changes as shown by curve C, and when the lens 2 is at the focal point, it changes as shown by curve D. Therefore, as described above, by moving the lens 2 upward or downward while causing minute vibrations at the frequency, as the position of the lens 2 approaches the in-focus point, the frequency 2 component included in the output signal g of the light receiving element 5 increases. Becomes large.

As mentioned above, the bandpass filter 6
Lens 2 passes the signal from Lens 2.
As the position approaches the in-focus point, the level of its output signal increases, and the level of the output signal of the detection circuit 8 which detects the average value of the output signal of the bandpass filter 6 via the amplifier 7 also increases. Comparator 9
compares the output signal of the detection circuit 8 with a predetermined threshold value L, and while the threshold value L is smaller, the output signal d is set to "1" and is applied to the input section 12. Therefore, the output signal d of the comparator 9 is
When the position coincides with the in-focus point, it becomes "1".

When the microprocessor 10 detects that the output signal d of the comparator 9 applied via the input section 12 becomes "1" (step S2), the microprocessor 10 determines that the position of the lens 2 is the in-focus point, and outputs the signal from the output section 13. control signal e
is added to set the output signal e to "0" (step S3). As a result, the switching circuit 19 is connected to the contact B side, and the output signal of the superimposing circuit 17 is transferred to the switching circuit 1.
9 to the drive circuit 20. That is, after setting the signal e to "0", the lens 2,
Beam splitter 3, light receiving element 5, compensation circuit 1
4, superimposition circuit 17, switching circuit 19, drive circuit 20
The position of the lens 2 is controlled by a focusing servo loop consisting of a motor 21 and a motor 21. Next, the microprocessor 10 starts a reproduction operation such as rotating the recording medium 1 (step S4), and then checks whether the signal d applied from the comparator 9 via the input section 12 is "0" or not. Make a judgment (step S5). If it is determined in step S5 that the signal d is "1", that is, if it is determined that the lens 2 is positioned at a position where the light receiving element 5 is in focus with respect to the recording medium 1, the microprocessor 10 determines whether or not the reproduction of the stored contents of the recording medium 1 has been completed (step S6), and if it is determined that the reproduction has been completed, it is determined whether or not to perform the reproduction operation again from the beginning (step S7). If the judgment result is YES, the process returns to step S1, and if the judgment result is NO, a reproduction stop operation such as stopping the recording medium 1 is performed (step S8), and then the process is ended. Furthermore, if it is determined that the signal d is "0" in step S5, that is, if it is determined that the lens 2 has deviated from the in-focus point due to vibration etc., a playback stop operation such as stopping the rotation of the recording medium 1 is performed. (Step S9), after which the process returns to Step S1.

Effects of the Invention As explained above, the first invention provides an oscillator 16
a first signal generating means which outputs a signal to relatively move the recording medium and the lens; a second signal generating means which comprises the oscillator 15 and causes the recording medium and the lens to minutely vibrate at a frequency; Consists of a bandpass filter that extracts the frequency 2 component from the output signal of the light receiving element, an amplifier 7, a detection circuit 8, and a comparator 9, and determines whether the level of the output signal of the bandpass filter is above a predetermined level. and a superimposing circuit 18,
a superimposing means for superimposing the output signal of the signal generating means; a moving means comprising a drive circuit 20, a motor 21, etc. for relatively moving the recording medium and the lens based on the output signal of the superimposing means; control means comprising a microprocessor 10 or the like that relatively moves the recording medium and the lens according to the output signal of the superimposing means until the means determines that the level of the output signal of the bandpass filter is equal to or higher than a predetermined level; Since the initial focusing is performed based on the frequency 2 component, it is less susceptible to fluctuations in the amount of reflected light due to the tilt of the recording medium, etc., and is less affected by the DC offset voltage. This has the advantage that it is less susceptible to influence, and therefore the focus position can be detected with high accuracy. In addition, since the lens 31 and the recording medium 32 are made to vibrate relative to each other, the focal position can be detected even when the recording medium is not rotating. It has the advantage of being able to do this.

Further, the second invention further includes a feedback signal generating means comprising a compensation circuit 14 and the like that generates a feedback signal based on the output signal of the light receiving element;
a second superimposing means consisting of a superimposing circuit 17 that superimposes the second signal and the feedback signal; and a switching means consisting of a switching circuit 19 that selectively applies the output signals of the first and second superimposing means to the moving means; When the power is turned on, when the determination means determines that the level of the output signal of the bandpass filter is equal to or higher than a predetermined level, the switching means is controlled to change the signal to be applied to the moving means from the output signal of the first superimposing means to the first one. When the determination means determines that the level of the output signal of the bandpass filter is equal to or lower than the predetermined level when the recording medium is reproduced;
A second signal is applied to the moving means by controlling the switching means.
Since it is equipped with a control means consisting of a microprocessor 10 or the like that switches from the output signal of the first superimposing means to the output signal of the first superimposing means, vibrations etc. are applied during reproduction of the recording medium and defocusing occurs. This has the advantage that focusing can be carried out immediately even in such a case.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the first invention, Fig. 2 is a block diagram of the second invention, Fig. 3 is a block diagram of an embodiment of the invention, Fig. 4 is an explanatory diagram of the operation of Fig. 3, FIG. 5 is a flowchart showing the processing contents of the microprocessor 10, and FIG. 6 shows the position of the lens 2 and the light receiving element 5.
FIG. 1 and 32 are recording media, 2 and 31 are lenses, 3 is a beam splitter, 4 is a light emitting element, 5 and 30 are light receiving elements, 6 and 37 are bandpass filters, 7 is an amplifier, 8 is a detection circuit, and 9 is a Comparator, 10 is a microprocessor, 11 is a memory, 12 is an input section, 1
3 is an output section, 14 is a compensation circuit, 15 and 16 are oscillators, 17 and 18 are superimposition circuits, 19 is a switching circuit, 2
0 is a driving circuit, 21 is a motor, 34 and 35 are signal generating means, 35 and 41 are superimposing means, 36 is a moving means, 38 is a determining means, 39 and 43 are controlling means, and 4
0 is a feedback signal generating means, and 42 is a switching means.

Claims (1)

[Scope of Claims] 1. An optical disk reproducing device that reproduces recorded contents of a recording medium based on an output signal of a light receiving element that converts reflected light from a recording medium that is incident through a lens into an electric signal. a first signal generating means for generating a first signal for relatively moving the recording medium and the lens in a focusing device which is provided and controls the relative position of the recording medium and the lens;
a second signal generating means for generating a second signal that makes the recording medium and the lens vibrate relatively at a frequency; a superimposing means for superimposing the first signal and the second signal; and a superimposing means for superimposing the first signal and the second signal. a moving means for relatively moving the recording medium and the lens based on an output signal of the means; a bandpass filter for passing a frequency 2 component of the output signal of the light receiving element;
determining means for determining whether the level of the output signal of the bandpass filter is equal to or higher than a predetermined level;
control means for relatively moving the recording medium and the lens by the output signal of the superimposing means until the determination means determines that the level of the output signal of the bandpass filter is equal to or higher than a predetermined level when the power is turned on; A focusing device comprising: 2. Provided in an optical disk reproducing device that reproduces recorded contents of the recording medium based on an output signal of a light receiving element that converts reflected light from the recording medium incident through a lens into an electric signal, the recording medium a first signal generating means for generating a first signal for relatively moving the recording medium and the lens in a focusing device that controls a relative position between the recording medium and the lens;
a second signal generating means for generating a second signal that causes the recording medium and the lens to vibrate minutely at a relative frequency; and a feedback signal generating means for generating a feedback signal based on the output signal of the light receiving element; a first superimposing means for superimposing the first signal and the second signal; a second superimposing means for superimposing the second signal and the feedback signal; and the first and second superimposing means. a switching means for outputting one of the output signals of the means; a moving means for relatively moving the recording medium and the lens based on the output signal of the switching means; and one of the output signals of the light receiving element. a band-pass filter that passes a frequency 2 component of the band-pass filter; a determining means for determining whether the level of the output signal of the band-pass filter is equal to or higher than a predetermined level; When it is determined that the level of the output signal of is equal to or higher than the predetermined level, the switching means is controlled to change the signal applied to the moving means from the output signal of the first superimposing means to the output of the second superimposing means. a signal that controls the switching means to apply a signal to the moving means when the determining means determines that the level of the output signal of the bandpass filter is below the predetermined level when the recording medium is reproduced; and control means for switching from the output signal of the second superimposing means to the output signal of the first superimposing means.