JPS6131507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording device that records information on a recording medium by means of a light beam.

For example, in an optical recording device that uses a recording medium in which a thin metal film is formed on a substrate with a highly reflective surface such as a glass plate, a light beam modulated (on/off) by a recording signal is projected onto the recording medium. , Dissolved parts (spots) and non-dissolved parts (non-spots) of metal thin film
Record information as a sequence of . A spot has a high reflectance because the substrate surface is exposed, whereas a non-spot has a low reflectance because it is a thin metal film surface. Therefore, by projecting a light beam and detecting the reflected light, recorded information on the recording medium can be reproduced.

Incidentally, the tip of a light beam for recording information on a medium has a finite spread, and its cross section is approximately circular. Therefore, the starting and ending ends of the spot formed on the medium are semicircular. The presence of this semicircular portion has the effect of increasing bit shift during reproduction, reducing the margin against reading errors.

The above will be explained in more detail with reference to FIG. In FIG. 1, WD is recorded information, which is designated as "1101" here. WS is a recording signal (binary signal) for recording information WD, and is created using the PM transformation method. D is a pattern of spots and non-spots recorded on the recording medium in response to the recording signal WS, and the hatched portions indicate spots. A high level of the recording signal WS corresponds to a spot. However, strictly speaking, the length of the light spot is γ+2Δγ for the high level period of the recording signal WS (γ when converted to distance on the medium). This Δγ corresponds to the radius of the light beam. In other words, even if the light beam is turned on (or turned off) at the same time as the recording signal rises (or falls), the tip (end) of the light spot will spread from the center of the light beam by the radius Δγ. When such a pattern is reproduced, the reproduced signal RS becomes as shown in the figure, and the high level portion of the reproduced data RD determined at a certain slice level extends by a total of 2Δt before and after the recorded signal WS.

The recording signal WS is generally created based on recording data using a self-clocking modulation method such as a PM method, an FM method, or an MFM method.
However, if a bit shift occurs due to the semicircular portions at both ends of the spot as described above, clocking will be disturbed and reading errors will no longer occur.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical recording device which solves the aforementioned problems caused by the semicircular portion of the spot.

In the optical recording apparatus according to the present invention, means for correcting the rising and falling phases of the recording signal is provided in order to compensate for the elongation of the spot caused by the thickness of the light beam. The correction effect by this means will be explained with reference to FIG.

FIG. 2 shows recorded data WD, recorded signal WS, recorded pattern D on the medium, reproduced signal RS of this pattern D, and reproduced data RD obtained by slicing this at a certain slice level by the optical recording device according to the present invention. An example is shown below. Conventionally, the rise and fall of the recording signal WS obtained by the PM modulation method are at the times indicated by dotted lines in the figure, but according to the present invention, the recording signal WS' rises with a delay of ΔT from the original rise time. The signal is caused to fall ahead of the original falling time by ΔT. The length of the spot is γ+2Δy, but Δy is smaller than the above-mentioned Δγ. Therefore, the playback data obtained from this recording pattern
RD rises and falls at predetermined times. In other words, the correction time ΔT of the transition time of the recording signal is determined so that Δt in FIG. 1 becomes approximately zero. Note that Δy must be determined by taking into consideration the rise time of the reproduced signal and the slice level thereof, and ΔT depends on the diameter of the light beam and the moving speed of the recording medium.

As described above, according to the present invention, accurate reproduced data can be obtained because the elongation of the spot caused by the thickness of the light beam is removed by correcting the timing of the rise and fall of the recording signal. It becomes like this.

An embodiment of the present invention is shown and explained in FIG. A laser beam 20 emitted from a light source 1 is input to an optical modulator 2. The output beam 21 of the optical modulator 2 passes through the half mirror 3 and is focused by the lens 4 onto the moving recording medium 5 . The control device 10 is
Binary data (recording data) given by "1" data input W1 and "0" data input W0 is converted into a recording signal (binary signal) 25 by a predetermined modulation method, for example, PM method. This recording signal 25 is input to the rising phase correction circuit 7 and the falling phase correction circuit 8 in the correction circuit 11. The mixing circuit 9 mixes the outputs of both circuits 7 and 8 and outputs a recording signal 24 in which the rising edge is delayed and the falling edge is advanced. Optical modulator 2
maintains the output beam 21 at a high (strong) level during the high level period of the corrected recording signal 24, and
The output beam 21 is kept at a low (weak) level during the low level period of 4. Thus, a pattern of spots for the corrected recording signal 24 is formed on the recording medium 5.

On the other hand, the reflected light from the recording medium 5 passes through the lens 4 and is guided to the analyzer 6 by a half mirror.
The analyzer 6 outputs a signal corresponding to the intensity of the reflected light beam 22, that is, a reproduced signal 23.

The feature of the apparatus of the present invention is that it is provided with a correction circuit 11, and the other parts may have the same configuration as the conventional apparatus.

As described in detail above, according to the present invention, the rise and fall times (phases) of the recording signal are corrected, so that the elongation of the spot caused by the thickness of the recording light beam is compensated for. Therefore, bit shifts during reproduction are reduced, ensuring reliable data reproduction.

[Brief explanation of the drawing]

FIG. 1 is a diagram conceptually showing the relationship between recorded data, recorded signals, recorded patterns, reproduced signals, and reproduced data in a conventional optical recording device, and FIG. 2 shows recorded data in an optical recording device according to the present invention, FIG. 3 is a diagram conceptually showing the relationship between a recording signal, a recording pattern, a reproduced signal, and reproduced data. FIG. 3 is a block diagram of an embodiment of an optical recording apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1... Light source, 2... Light modulator, 3... Half mirror, 4... Lens, 5... Recording medium, 6... Analyzer, 10... Control device, 11... Correction circuit.

Claims (1)

[Claims] 1. A first generator that generates a binary signal related to recorded information.
means for correcting the binary signal; and a second means for correcting the binary signal.
third means for projecting a light beam onto the recording medium;
a fourth means associated with the third means for changing the intensity of the light beam projected onto the recording medium according to the binary signal corrected by the second means; The second means corrects the uncorrected binary signal so as to delay the phase of change in the direction in which the intensity of the light beam increases and accelerate the phase of change in the opposite direction; an optical recording device configured to supply