JPH0454569Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recorded information reading device, and more particularly to an improvement of a generation circuit for generating a read RF (high frequency) signal, that is, an information read signal of an optical recorded information reading device.

A conventional device of this type is shown in FIG. That is, a so-called 4-segment type light-receiving element 3 is used in which the light-receiving surface is divided by a dividing line 1 parallel to the tangent to the recording track of a recording disk (not shown) as a recording medium and a dividing line 2 perpendicular to the dividing line 1. There is a reading device of the same type. Outputs of the upper elements 3a and 3d in the figure are added by an adder 4, and both outputs of the lower elements 3b and 3c are added. are added by the adder 5. Then, the outputs of both adders 4 and 5 are added by an adder 6, and the result is derived as a read RF signal.

In such a configuration, a reading light beam is converged and irradiated onto the recording surface of the recording disk, and the reflected light from the recording surface of this irradiated light is guided to the four-divided light receiving surface of the light receiving element 3. It is reading recorded information.

FIG. 2 shows the relationship between the pit 7 on the recording track and the reading light beam spot 8, and the outline of the diffraction image of the reflected light 9 on the light receiving surface in that case. A is a diagram at each time _t1 to _t3 when the position of the spot light 8 with respect to the recording track 7 is slightly shifted to the right in the direction orthogonal to the track, and B is a diagram at each time when the position of the track and the spot light is normal. _t1 to _t3
Figures 1 and 2C are diagrams at each time _t1 to _t3 when the position of the spot light relative to the track is slightly shifted to the left in the direction orthogonal to the track. It is assumed that the depth of the pit 7 is λ/5 (λ is the wavelength of the spot light). In other words, the sum of the outputs of the light receiving elements 3a and 3d,
It can be seen that the sum of the outputs of the light receiving elements 3b and 3c have the same waveform with only a certain time difference (phase difference). An example of the waveform is shown in FIG. 3, where A is the waveform of the sum of the outputs of the light receiving elements 3a and 3d;
B is the waveform of the sum of the outputs of the light receiving elements 3b and 3c, and C is the sum of the outputs of all these light receiving elements, which is the read RF signal waveform. Since the waveform shown in A and the waveform shown in B are the same waveform with a phase difference t ₀ , the output waveform added by the adder 6 of these two waveforms has a slow rise and fall as shown in C. At the same time, when the pit length is small, the amplitude of the output waveform is smaller by A ₀ than when the amplitude is large.

In other words, the attenuation of the optically generated high-frequency characteristics appears in the RF signal as the above-mentioned distortion. Therefore, there is a method of compensating for these distortions using an equalizer or the like, but this method has the drawbacks of complicating the circuit configuration and causing unnecessary phase shifts.

The present invention was devised to eliminate such drawbacks of the conventional ones, and the purpose is to provide a recorded information reading device that can almost accurately eliminate distortion due to deterioration of high-frequency characteristics with a simple configuration. There is.

The recorded information reading device according to the present invention uses one of the reflected beams of the light beam irradiated onto the recording surface of the recording medium as an information reading beam and receives the light by at least one pair of light receiving elements arranged adjacently in a direction parallel to the recording track tangent. The recorded information reading device obtains an information reading signal by using the above-described method, and is configured to include a phase adjusting means for matching the phases of the output signals of the pair of light receiving elements, and an adding means for adding the two output signals whose phases match. ing.

An embodiment of the present invention will be described below with reference to FIG. In the figure _, parts equivalent to those in FIG. The output of the adder 5 is added to the output of the adder 6, and the output of the adder 6 is used as a read RF signal. The other configurations are the same as those in FIG.

That is, among the output sum of the elements 3a and 3d and the output sum of the elements 3b and 3c arranged adjacently in the direction parallel to the recording track tangent, the output sum of the elements 3a and 3d is delayed by the delay time _t0 . , the phase is made to match the sum of the outputs of the other elements 3b and 3c.

By doing this, the waveform of the output sum of elements 3a and 3d shown in FIG. 5A is delayed by _t0 as shown in FIG. 5A'. Therefore, the waveform of A' and B
The waveform of the sum of the outputs of elements 3b and 3c shown in FIG. 1 coincides in phase, and the sum of the two waveforms becomes a waveform like C, and there is no rise or fall distortion or decrease in amplitude.

In the above embodiment, a four-split light receiving element is used, but a two-segment type light receiving element in which the light receiving surface is divided only by the dividing line 2 in the direction perpendicular to the tracks may also be used.
Furthermore, the dividing line 2 is not limited to a straight line.
Furthermore, although only one output is delayed, both outputs may be delayed as desired so that the phases match.

The delay time t ₀ is approximately 220 ns in a digital audio disc reading device, but when applied to a video disc reading device, the delay time t ₀ may be adjusted accordingly.
Furthermore, in a reading device where the track linear velocity is not constant, a variable delay line may be used to vary the delay time in accordance with the linear velocity.

As mentioned above, according to the present invention, distortion due to deterioration of optical high-frequency characteristics can be compensated for very easily, so that the rising and falling edges of the RF signal become steep, and there is no reduction in level, so the signal This results in a reduction in the reading error rate.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional recorded information reading device, Figure 2 is a diagram showing the relationship between the reading light beam spot and the recording track pit, and the diffraction image on the light receiving surface in that case, and Figure 3 is the same as Figure 1. read by the device
4 is a block diagram of an embodiment of the present invention, and FIG. 5 is an RF signal waveform diagram read by the apparatus shown in FIG. 4. Explanation of symbols of main parts, 3... Light receiving element, 4,
5, 6...Adder, 10...Delay unit.

Claims (1)

[Claims for Utility Model Registration] One of the reflected beams of the light beam irradiated onto the recording surface of the recording medium is used as an information reading beam and is received by at least one pair of light receiving elements arranged adjacently in a direction parallel to the tangent to the recording track. A recorded information reading device for obtaining an information reading signal, comprising: a phase adjusting means for matching output signal phases of the pair of light receiving elements; and an adding means for adding the phase-matched output signals to obtain the information reading signal. A device characterized by comprising: