JPH03120623A - Error signal detector - Google Patents

Abstract

PURPOSE:To always and effectively record/reproduce data without the shift of a servo by multiplying an error signal obtained based on the outputs of plural light-receiving elements by a signal obtained by means of adding the outputs of plural light-receivng elements. CONSTITUTION:An adder 61 adds the outputs of adders 54 and 55 and the sum signal (SUM signal) of the outputs of light-receiving areas 43-1 to 43-8 is obtained. The SUM signal, the output of a subtracter 56 and the output of a subtracter 53 are respectively multiplied in multipliers 62 and 63. Then, a focus error signal FE is obtained from the multiplier 62 and a tracking error signal TE from the multiplier 63. If focus servo and tracking servo are controlled based on the tracking error signal TE, an appropriate servo signal can always be obtained without being affected by recorded data. Thus, data can always and effectively be reproduced without the shift of the servo.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention records information on an optical recording medium such as an optical card, compact disc, or video disc through an objective lens, and reproduces recorded information. The present invention relates to an error signal detection device in an optical information recording and/or reproducing device.

[Conventional technology]

In an optical recording and/or reproducing device, focus servo and tracking servo are performed to maintain the relative position between the objective lens and the recording medium. Various types of error signal detection devices for performing such focus servo and tracking servo have been proposed in the past, and the present applicant also proposed, for example, in Japanese Patent Application No. 63-204819, that illumination light is applied to a recording medium from the normal direction thereof. Projecting the illumination light in a defocused state, among the reflected light, the reflected light inside and outside of the unchanged portion where the illuminance hardly changes even if the defocus state of the illumination light changes is received by a light receiving element, respectively.
We have proposed a system that generates error signals based on these outputs.

FIGS. 3 and 4 are a cross-sectional front view and a plan view showing the configuration of an example of an optical helad of an optical reproducing apparatus equipped with an error signal detection device previously proposed by the applicant. This optical playback device reads data recorded on the optical card 11 by relatively moving the optical card 11 and the optical head in the track direction of the optical card 11, and uses a light emitting diode ( LED) 12 is arranged slightly behind the focal position f0 of the collimator lens 13.

The illumination light from this LED 12 is transmitted to the collimator lens 13.
, half mirror 14, reflection mirror 15 and objective lens 1
6 and is projected onto the optical card 11 from its normal direction,
The tracks of the optical card 11 are illuminated in a defocused state, and the reflected light is collected by an objective lens 16, passes through a reflecting mirror 15, a half mirror 14, and a lens 17, and is received by a photodetector 18. There is.

The objective lens 16 is held by a holder 21 and connected via four parallel wires 22 to a focus direction F, which is the optical axis direction of the objective lens 16, and a tracking direction T, which is orthogonal to the focus direction F and the track of the optical card 11. It is movably supported by a wire stand 23 fixed to a base (not shown). The holder 21 has focus coils 24A and 24 on opposing end faces in the tracking direction T.
A flexible substrate 26 on which tracking coils 25A and 25B made of printed coils are formed is also mounted so that the tracking coils 25A and 25B are located outside of the focus coils 24A and 24B.

Also, a focus coil 24A is provided on the base (not shown).
, 24B are provided, and a pair of outer yokes 28A, 28B are opposed to these inner yokes 27A, 27B via focus coils 24A, 24B and tracking coils 25A, 25B, respectively. and 29A, 29B are provided, and these outer yokes 28A, 28B and 29A, 29
Permanent magnets 30A, 30B and 31A inside B, respectively.
, 31B are attached, and the tracking coil 25A and focus coil 24^ are attached by the permanent magnets 30A and 30B.
The permanent magnets 31A and 31B generate a magnetic flux that crosses the tracking coil 25B and the focus coil 24B, respectively. In this way, by supplying focus error signals to the focus coils 24A and 24B via two of the four parallel wires 22, the objective lens 16 is displaced in the focus direction F together with the holder 21. The objective lens 1 is integrated with the holder 21 by performing focus servo and supplying a tracking error signal to the tracking coils 25A and 25B via the other two wires.
6 is displaced in the tracking direction T to perform tracking servo. In addition, LED 12, collimator lens 13, half mirror 14, reflection mirror 1
5. The lens 17 and the photodetector IB are fixedly held on a base (not shown).

FIG. 5 shows an example of the track format of the optical card 1i shown in FIG. A guide pattern 36 consisting of a black and white pattern is formed in the center of the track 35 and extends in the track direction, and 8-bit data is recorded on each side of the guide pattern 36 in the track width direction. .

FIG. 6 shows the configuration of an example of the photodetector 18 shown in FIG. 4. 18 photodetectors, 16 in the track width direction
data reading light receiving areas 41-1 to 41-16 arranged corresponding to the data recording positions, and the guide pattern 3.
5 pairs of clock generation light receiving areas 42-1 to 42-1 arranged at a distance of 7 in the track direction so as to receive images of 6;
0 and four pairs of focus/tracking error detection light receiving areas 43-1 to 43-8 arranged apart in the track width direction so as to receive images of both edge portions of the guide track 36 in the track width direction. It is configured.

Here, as described above, when the LHDI 2 is arranged slightly behind the focal position fo of the collimator lens 13 and the optical card 11 is illuminated in a focused state, the illumination light is closer to the objective lens than the focal position of the objective lens 16. focused on. Therefore, the focal position of the objective lens 16 is
In the focused state located above, the illuminance distribution of the illumination light on the optical card 11 becomes as shown by the solid line in FIG. 7, for example,
Also, as the optical card 11 approaches the objective lens side (the spot diameter becomes smaller, the illuminance distribution becomes as shown by the broken line in Fig. As shown by the chain line, the illuminance distribution of the illumination light on the optical card 11 is carbonized depending on the distance between the objective lens 16 and the optical card 11, but as is clear from FIG. In addition, a ring-shaped constant portion (indicated by reference numeral 45 in FIG. 6) whose illuminance hardly changes even if the distance between the objective lens 16 and the optical card 11 changes is generated in the illumination area. The change in illuminance due to the change in the focal state of the objective lens 16 is opposite between the inside and outside of the changing portion 45. That is, as the optical card 11 approaches the objective lens side, the illuminance changes inside the unchanged portion 45. While it increases when in focus, it decreases on the outside, and conversely, when the optical card 11 moves away from the focal position of the objective lens 16,
Inside the unchanged portion 45, the illuminance decreases compared to when in focus, while outside it increases.

Here, as shown in FIG. 6, a data reading light receiving area 41-1 corresponding to the data recording position of the track 35 is
- 41-16 are arranged along the diameter direction of the unchanged portion 45 of the spot image of the optical card 11 caused by the illumination light formed on the photodetector 18 inside the unchanged portion 45, and focus/tracking error detection is performed. Light receiving area 43-3.43
-4 and 43-5, 43-6 are located at symmetrical positions with respect to the center inside the unchanged portion 45, and other focus/tracking error detection light receiving areas 43-1, 43-2, 43-7, 43- 8 are arranged at symmetrical positions with respect to the center of the unchanged portion 45 such that each center is located outside the unchanged portion 45. Furthermore, the five pairs of clock generation light receiving areas 42-1 to 42-10 form a pair of focus/tracking error detection light receiving areas 43-3.
The guide pattern 36 is arranged between 43-4, 43-5, and 43-6 at a pitch of 172 of the black and white pattern image. Note that in each of the focus/tracking error detection light receiving areas 43-1 to 43-8, the spot center of the illumination light (optical axis of the objective lens 16) is aligned with the track 35.
The white part (high reflectance part) between the guide pattern 36 and the data part has a length that can receive the images of the edge parts in the track width direction of the plurality of black and white patterns. ) has a width that is large enough to receive the reflected light from.

In this way, one of the paired clock generation/light receiving areas 42-1.42-3.42-5.42-7 and 42
−9, the other light receiving area for clock generation 42−
A clock signal is obtained based on the difference between the sum of the outputs of 2.42-4, 42-6.42-8 and 42-10. Further, as shown in the error signal detection device in FIG. 8, a light receiving area 43-1.43-3.43- receives an image of one edge portion of the guide pattern 36 in the track width direction.
A light receiving area 43-2.43-4.4 which adds the outputs of 5 and 43-7 with an adder 51 and receives the image of the other edge portion.
By adding the outputs of 3-6 and 43-8 in an adder 52 and subtracting the outputs of these adders 51 and 52 in a subtracter 53, a tracking error signal (TE) is obtained. The adder 54 adds the outputs of the light-receiving regions 43-3, 43-4, 43-5, and 43-6 located inside the changed portion 45, and the outputs of the light-receiving regions 43-1. 43-2.43-7 and 43-8
An adder 55 adds the outputs of these adders 54 and 55.
A focus error signal (FE) is obtained by subtracting the output from the subtracter 56.

Here, focus servo is performed by displacing the objective lens 16 in the optical axis direction so that the optical card 11 is located at its focal position based on the focus error signal obtained as described above, and also based on the tracking error signal. While performing tracking servo so that the spot center of the illumination light is located at the center of the desired track 35 of the optical card 11, the objective lens 16 is moved to the light receiving areas 41-1 to 41-16 for data reading in synchronization with the clock signal. The output of the 16-bit data is read at the same time.

[Problem to be solved by the invention]

However, in the above-mentioned error signal detection device, if there is a concentrated dark area in the data section of the optical card 11, for example as shown in FIGS. -1~43
-8, affecting the focus error signal and/or tracking error signal, and affecting the objective lens 16.
There is a problem in that servo deviation occurs such that the track is thick (displaced) or deviates from the desired track in one direction in the focus direction F, making it impossible to reproduce or record data.

That is, if there are areas where dark areas are concentrated on both sides of the guide pattern 36 as shown in FIG. Since the detection is based on the difference in the amount of reflected light, the influence of dark areas is canceled out and there is almost no influence, but the focus error signal FE is detected based on the difference in the amount of reflected light between the inside and outside of the unchanged portion 45. Because of the detection, as the optical card 11 and the illumination light move relative to each other in the track direction, the light changes greatly as indicated by the symbol a. Furthermore, if there is a concentrated dark area on one side of the guide pattern 36 as shown in FIG.
As indicated by b1, R is smaller than the case in FIG. 9A, but it still changes significantly, and the tracking error signal TH is detected based on the difference in the amount of reflected light between the edge portions on both sides of the guide pattern 36. Therefore, it is greatly affected by the dark area and changes greatly as shown by b2.

This invention was made by focusing on these problems, and it is possible to always obtain a proper servo signal without being affected by the recorded data, so the data can be used effectively without causing servo disconnection. It is an object of the present invention to provide an error signal detection device suitably configured to record/reproduce information.

[Means and Actions for Solving the Problems] In order to achieve the above object, the present invention uses illumination light projected through an objective lens onto an optical recording medium having a track composed of a plurality of mutually parallel bit strings. In the error signal detection device, the reflected light is received by a plurality of light receiving elements, and an error signal representing a relative positional deviation of the objective lens with respect to the optical recording medium is detected based on the outputs of these light receiving elements. A means for adding the outputs of a plurality of light receiving elements, and a means for multiplying the output of the adding means and the error signal, and obtaining an error signal from which the influence of the dark part of the optical recording medium has been removed from the multiplying means. Configure.

〔Example〕

FIG. 1 shows an embodiment of the present invention.

This error signal detection device is applied to an optical reproducing device that reproduces data using the optical head shown in FIGS. 3 and 4 for an optical card 11 having the track format shown in FIG. Among the light receiving areas 43-1 to 43-8 for focus/tracking error detection of the photodetector 18 shown in No. 6, the light receiving area receives an image of one edge portion of the guide pattern 36 in the track width direction. Area 4
3-1.43-3.43-5.43-7 and a light-receiving area 43-2.43-4.
The outputs of 43-6 and 43-8 are added by adders 51 and 52, respectively, and the outputs of these adders 51 and 52 are subtracted by a subtracter 53, as shown in FIG.

In addition, the light receiving area 43- located inside the unchanged portion 45
3.43-4.43-5.43-6 and the light receiving area 43-1 located outside the unchanged portion 45.
Similarly to the case shown in FIG.

In this embodiment, the outputs of adders 54 and 55 are input to adder 61.
The sum signal (S open signal) of the outputs of the light-receiving areas 43-1 to 43-8 is obtained, and this SUN signal, the output of the subtracter 56, and the output of the subtracter 53 are added by the multipliers 62 and 63. By multiplying them, the focus error signal FE is obtained from the multiplier 62 and the tracking error signal TE is obtained from the multiplier 63.

With this configuration, SUN obtained from the adder 61
If there is a concentrated dark area in the data section of the optical card 11 as shown in FIGS. 9A and 9B, the signal changes as shown by c1 and c2 in FIG. 2 accordingly.

In other words, when the SUN signal is affected by a dark area, the value becomes smaller than the normal level of "1". In contrast, the signal (F
f! ') and the signal (TE'') output from the subtracter 53
change in the same way as shown in Figure 1θ, so
When these PE' and TE' are multiplied by the SUN signal by the multipliers 62 and 63, the level obtained from the multiplier 62 becomes smaller than normal when the St1M signal is affected by the dark area. Focus error signal FIl! The tracking error signal TE obtained from the multiplier 63 and the tracking error signal TE each has the influence of the dark area corrected as shown in FIG. 2, so that an appropriate servo signal can always be obtained.

Therefore, if focus servo and tracking servo are performed based on the focus error signal FE obtained from the multiplier 62 and the tracking error signal TH obtained from the multiplier 63, the focus servo and the tracking servo can be performed without being affected by the recorded data. Since a proper servo signal can always be obtained, data can always be effectively reproduced without servo failure.

In the above description, the case where data is reproduced has been explained, but the present invention can also be effectively applied to the case where an error signal is detected when recording data.

〔Effect of the invention〕

As described above, according to the present invention, by multiplying an error signal obtained based on the outputs of a plurality of light receiving elements by a signal obtained by adding the outputs of the plurality of light receiving elements, Since the influence of It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining its operation, and FIGS. 3 and 4 are configurations of an example of the optical head previously proposed by the applicant. 5 is a diagram showing an example of the track format of the optical card shown in FIG. 3, FIG. 6 is a diagram showing the configuration of an example of the photodetector shown in FIG. 4, Fig. 7 is a diagram showing changes in the illuminance distribution of illumination light on the optical card in Fig. 3, Fig. 8 is a diagram showing the configuration of the error signal detection device proposed earlier by the applicant, and Figs. 9 A and B. 10 is a diagram showing a form of a dark area in the data section of an optical card, and FIG. 10 is a diagram for explaining a problem with an error signal due to the dark area. 11--Optical card 12--LED1
6.One objective lens 17.-Photodetector 35.
- Track 36 - Guide pattern 41-1 to 41-16 - Light receiving area for data reading 42-1 to 42-10... Light receiving area for clock generation 4
3-1 to 43-8 -- Light receiving area 51 for focus/tracking error detection, 52.54.55.61 -- Adder 53
．． 56 - Subtractor 62. 63 - Multiplier Fig. 1 Fig. 2 Fig. 5 Fig. 1 Fig. 3 Fig. 4 Fig. 6 Fig. 7 Fig. 9

Claims (1)

[Claims] 1. A plurality of light receiving elements receive reflected light of illumination light projected through an objective lens onto an optical recording medium having a track composed of a plurality of mutually parallel bit strings. An error signal detection device configured to detect an error signal representing a relative positional deviation of the objective lens with respect to the optical recording medium based on the output, comprising: means for adding the outputs of the plurality of light receiving elements; and the adding means. and means for multiplying the output of the error signal by the error signal, and is configured to obtain an error signal from which the influence of dark areas of the optical recording medium has been removed from the multiplication means.