JPS6045947A - Defocusing detector of optical disk head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention provides information 11! for digital audio discs, video discs, etc. #Reward 11' from 16 ζtI・
11°・°", Out.

Focus c1 of the optical disk head that penetrates a certain 1″l
Regarding the detection device ■.

[Prior Art] Conventionally, there has been a device for this illumination as shown in FIG. FIG. 1 shows a conventional disk head focus shift detection device. In =71.

"'" Semiconductor 1/ -Sanato'))'to +)
it, (2) 1.1) Y; Output from Jun full) 1
5 bundles, +: nt: l: digital; 4-i 1st 1st 1st 1st 1st 1st Y spiral track 141 (/(,) i! 4 recorded information record If the medium is one disk, fail It'', output 91 element flux 121 ?, focal point position U near pressure 1r (or i
'Lii leek °r, the light that gathers on the track (4) of the disk +31-IJ: Rue 1 object lens, (6 eyes τ1 objective lens from the condensed spot (7) on the optical disk (3) (
5) is a beam splitter that separates the emitted light beam (2) and reflected light beam (6), (9) is a 4-split photodetector, and 6G is a 4-split source detector (9). A cylindrical lens whose center line is tilted 45 degrees with respect to the dividing line.

(Ill is a reflected light spot given astigmatism by the cylindrical lens (IIIK) and focused on the 4-split detector (9), (12 is the reflected light spot in each diagonal direction of the 4-split detector (9) A differential amplifier that commonly connects the regions and obtains the difference in the light reception output of adjacent regions, Q (is a motor that rotates the optical disk (3), (141 is a motor that rotates the optical disk (3), and (141 is a motor that rotates the objective lens (5)
) in the radial direction.

That is, it is a truck actuator that causes pressure displacement in a direction perpendicular to the track (4).

Next, its operation will be explained. The light beam (2) emitted from the light source (1) is focused onto the C disk (31) by the objective lens (5), and the light beam from the focused spot (7) passes through the objective lens (5). (6) is separated from the output beam (2) by the beam splitter (8).This separated reflected beam (6) is given astigmatism by the cylindrical lens αl and is sent onto the 4-split source detector (9). reflected light spora)
(The light is focused on Ill.In order to read and write precisely from the disc (31)
:) 'e-task 13) must be precisely at the focal point position of the objective lens (5) and focused on the smallest original spot (7), but the actual optical disc (31) is not flat and rotates. J Two-sided vibration occurs, resulting in focus shift.

In response to this focus shift, the reflected light spot on the four-split photodetector (9) changes as shown in FIG. That is, when the original disk (31) is at the focused position, the circular reflected light spot (11b) as shown in FIG. ° Different elliptical reflected light spots (11
(11 is obtained. Therefore, the output B of the differential amplifier θ force is
f is the focus shift △yVcaJ and q+, in Figure 3]
” - The characteristic diagram for detecting scrap misalignment changes as shown in Fig. 1. However, in this conventional device, M: A focused spot (7 1. When the lens (5) is moved in the radial direction of the original disk by the tracking actuator I, the VC 4-division yt detector (
9) The position of the above reflected light spora) all also moves, which has the disadvantage that the defocus detection characteristics deteriorate.

That is, when the position of the reflected light spot all is displaced from a to b in FIG. 4 at 45 degrees with respect to the dividing line.

An offset occurs in the out-of-focus detection signal from the differential amplifier 01) and a decrease in sensitivity t occurs.If the direction busy spot l of the dividing line shifts from a to b in Fig. 5, no offset occurs but the sensitivity decreases. As mentioned above, with conventional focus shift detection devices, the detection characteristics deteriorate due to the displacement of the focused spot (7) on the original disk due to the tracking actuator drive, which is a major obstacle to accurate focus servo operation. .

[Summary of the Invention] This invention was made to eliminate the drawbacks of the conventional device described above, and by using a photodetector divided into three by two parallel lines, the original An object of the present invention is to provide a defocus detection device for an optical disk head that can eliminate the influence of displacement of a focused spot on a disk.

[Embodiments of the Invention] Next, an embodiment of this invention will be described with reference to FIGS. 6 to 8.

FIG. 6 is a schematic diagram showing an example of the structure of the 4F' of the photodetector fls according to the present invention and the connection with the differential amplifier pupil, and the other parts are constructed in the same manner as in FIG. 1. . BuC detector (I
9 is divided into 3 parts by 2 parallel straight lines *1! The width of the central region I, the interval between the two divisions, and the distance between the two direct interrogations of this photodetector when the optical disc (3) is in the focused position are It is smaller than the diameter, and the amount of light received by its central region (2) and the regions on both sides 1.
It is determined that the sum of the amount of light received by * is equal to the sum of the amount of light received. Then, by setting the direction of the division 210 mm to be the short axis direction of the reflected light spora l (1111,) when the focus is out of focus, and the same direction as the long axis direction y of the incident light spot (11C), 9 reflected light spots are created. In (11a,), both sides'↑11 area 1
．． If the amount of light received by I is larger than the amount of light received by center area 1, and 9 reflection source spots (11C), center 4 (1h)
The amount of light received by 41 is greater than that by regions 2 and 1 on both sides. Therefore, at the output of differential amplifier I.

A detection output having a polarity determined by the first direction of focus and a magnitude corresponding to the magnitude of the focus can be obtained. Furthermore, the direction 7Y of this dividing line is made to coincide with the displacement direction of the reflected light spot (0) due to the displacement of the collecting spot (7) by driving the ratkink actuator θ4,
Shadows such as deterioration of detection characteristics due to the displacement can be removed.

In the above embodiment, when the disk (31) is at the focal point position, the amount of light received by the central area 1 of the three-part photodetector 9 and the sum of the amount of light received by the two side areas 1.I are equal to 1- In order to It had the disadvantage that the adjustment was complicated and the adjustment cost was high.

In the first place, the second invention was made to eliminate the above-mentioned drawbacks, and FIG. 8 shows only the 3-split C detector Q51 of the embodiment, and the other parts are the same as in FIG. 1. are configured similarly. That is, a photodetector (l!il) is tilted so that the directions of its two straight lines are non-parallel, and the photodetector (l!il) is tilted so that the directions of its two straight lines are non-parallel. By moving the disc in the direction along the dividing line,
31 is at the focal point position, adjust the width of the center 2 area 10 at the reflected light spot position 1N to this photodetector (19), and adjust the light reception jl by the area 1 tail and the side areas 1.
So that the 't-ff1-sum received by I is equal,
That is, it can be adjusted so that the offset of the focus shift detection output from the differential amplifier (12) becomes O.

As a result, position 6 of the photodetector (19) [■ Adjustment can be performed only in the plane that intersects with B C1 God* N'X! Adjustment cost can be reduced.

By making the divided two straight lines non-parallel, some shadow ff4 due to the movement of the truck actuator will occur, but by appropriately determining the inclination angle V &C, Turning to things, it is h [noh] to make a small shadow @ of confusion or busyness.

In addition, in each of the two or more examples, 1-Ratsukinkakuchi 1-
Although we have shown an example in which the objective lens (5) is moved in the radial direction of the original disk using the mirror I, it is also possible to place a reflecting mirror in front of the objective lens (5) and use it as a mirror, or to move the objective lens (5) in the radial direction of the original disk.
Of course, 1) may also be applied to a device that moves in the lateral direction.

(The above explanation is about reading information from a disk.''1-
I have been talking about optical disk heads, and this is 41f.
It is clear that the present invention may also be applied to an optical disk head that records information on a disk.

[One result of the invention] As described above, the present invention is a defocus detection device using a cylindrical lens, and a photodetector divided into three by two parallel straight lines is used, so that the tracking actuator can be driven. Variations in the defocus detection characteristics can be easily removed. This has the effect that an extremely accurate out-of-focus detection device can be obtained at a relatively low cost.

[Brief explanation of the drawing]

f5', Figure 1 is a schematic diagram showing a conventional optical disk head focus shift detection device, Figure 2, Figure 3, Figure 4,
Fig. 5 is an explanatory diagram of its operation, Fig. 6 is a schematic diagram showing only a photodetector and a differential amplifier according to an embodiment of the present invention, Fig. 7 is an explanatory diagram of its operation, and Fig. 8 is a diagram illustrating its operation. FIG. 7 is a diagram showing only a photodetector of another embodiment. In the figure, (1) is a light source, (3) is an optical disk which is an information recording medium, (5) is an objective lens, and (8) is a beam splitter. (91iJ: 4-division original detector, αa is a cylindrical lens, +
13 is a differential amplifier that takes out a signal according to the focus shift, ■ is a tracking actuator, and 1151 is a 3-split source detector. The same reference numerals in the drawings indicate the same or corresponding parts. Agent Masuo Oiwa (and 2 others) Chain 1 figure ¥12WB $4111 C (L) (b) Figure 5 (α) (shi) Procedural amendment (voluntary) 59 4 27' Showa year month day 1, Display of incident Patent application No. 58-154333 2,
Title of the invention: Optical disk head focus shift detection device 3, relation to famous case for correction Patent applicant address: 2-2-3 Marunouchi, Chiyoguchi, Tokyo Name (601) Representative of Mitsubishi Electric Corporation Hitoshi Katayama Department 4, Attorney 5, Subject of amendment (1) Claims column of the specification (2) Prompt for detailed explanation of the invention in the specification (3) Prompt for a brief explanation of the drawings (4) ) Figure 5 (b) of the drawing 6. Contents of amendment (1) The specification is amended as shown in the attached sheet (the title of the invention remains unchanged). (2) Extend the drawer ties marked with the symbol (itb) in Figure 5(b) as shown in the attached sheet. [1] Description 10 Title of the invention Focus shift detection device for optical disk head
An objective lens that focuses light onto a track of an information recording medium recorded in a square shape, and a beam that separates the emitted light flux from the light source and the reflected light flux from a focused spot on the recording medium that passes through the objective lens. A splitter, a cylindrical lens that imparts astigmatism to the separated reflected light beam, and a reflected light beam that passes through this cylindrical lens is circular when the information recording body is at the focal point position of the objective lens, and at a position further away from it. The elliptical reflected light spot is placed at a position where the light is focused on an elliptical reflected light spot 1~ with major axes in different directions, x and y, by 90'' depending on whether the spot is located near or in the major axis direction of the elliptical reflected light spot. Equipped with a photodetector divided into three by two straight lines in approximately the same direction as X or Y, the difference between the amount of light received by the central area of the photodetector and the light phase received by the areas on both sides of the photodetector is used to determine the amount of light received by the recording medium. An optical device designed to extract a signal corresponding to the deviation from the focal point position of the objective lens is installed in the focus deviation detection device r of the ``suf head'', and detects the direction of the 1-2 straight lines of the light book. By tilting the photodetector so that it is non-parallel to the optical axis and moving it in the direction along the dividing line, one reflected light spot can be detected. A defocus detection device for an optical disk head, characterized in that the distance between both dividing lines can be adjusted.Detailed Description of the Invention [Technical Field of the Invention] This invention relates to a defocus detection device for an optical disk head that reads or writes information from an information recording medium such as a disk. [Prior Art] As a conventional device of this type, there has been one shown in Fig. 1. Fig. 1 1 is a schematic diagram showing a conventional phonics shift detection device for an optical disk head. In the figure, (1) is a light source such as a semiconductor laser, (2) is the emitted light flux from the light source (+), and (
3) is an optical disk which is an information recording medium on which information such as a digital audio signal or video signal is recorded on a spiral track (4); Track (4) of optical disc (3)
), the objective lens (6) focuses the light onto the optical disk (3
), the reflected light flux passes through the objective lens (5) from the condensing spot (7) on
), (9) is a 4-split photodetector, (10) is a cylindrical lens arranged with the center line of the lens tilted at 45 degrees with respect to the dividing line of the 4-split photodetector (9), ( 1
1) has a cylindrical lens (10) that causes astigmatism.
Divided photodetector (reflected light spot focused on 9 o 10, (
I2) is a differential amplifier that commonly connects the diagonal areas of the four-split photodetector (9) and obtains the difference in the received light output of adjacent areas, and (13) is a motor that rotates the optical disk (3). , (14) connects the objective lens (5) to the disk (3)
This is a 1-racking actuator that causes displacement in the radial direction of the 1-rack (4), that is, in the direction orthogonal to the 1-rack (4). Next, its operation will be explained. The light beam (2) emitted from the light source (1) is focused onto the solo disk (3) by the objective lens (5), and is reflected from the focused spot I-(7) through the objective lens (5). The light beam (6) is separated from the output light beam (2) by a beam splitter (8). This separated reflected light beam (6) is given astigmatism by a cylindrical lens (10) l: and is sent to a four-split photodetector (!I)-1- as a reflected light spot (11) M1. information)
16 Te, in order to read or write accurately from the C disk (3), the optical disk (3) must be accurately positioned at the focal point of the objective lens (5), and the light must be focused on the smallest light spot (7). However, the actual optical disc (3) is not flat and the circuit causes surface wobbling, resulting in focus shift.The 4-split photodetector (9)
The reflected light above (moon) changes as in the 211th. That is, when the optical disc (I3) is at the focused position,
As shown in No. 21mb, the circular h radiation light spot (l
lb) is out of focus and produces 1 mo, an elliptical reflected light spot h (III+) (Ilc) whose major diameter directions x and y differ by 90 degrees is obtained depending on the direction of the shift. Therefore differential amplification! The output j (r) of (+2) changes as shown in the focus shift detection characteristic diagram in FIG. 3 with respect to the focus shift ΔF. However, in this conventional #A position, - In order to make the position of the condensing spora I (7) follow the displacement of the track (4) in the optical disc radial direction due to the rotation of the optical disc (3), a racking actuator is used. (14) by the condenser lens (5
) is moved in the radial direction of the optical disk, the positions of the reflected light spoilers 1 to (11) on the 4-split photodetector (9) also move, resulting in deterioration of the defocus detection characteristics. That is, the position of the reflected light spot (11) is shown in FIG.
When the shift is made from 1 to b in a direction that makes a 45° angle with the dividing line, offset 1- occurs in the defocus detection signal from the differential amplifier (11), resulting in a decrease in sensitivity in J(. If the spora h (11) is displaced in the direction of the dividing line, the off-sera 1- will not occur, but the sensitivity will decrease.
- Detection characteristics deteriorate due to displacement of the focused spot (7) on the optical disk due to the driving of the racking attachator, which poses a major obstacle to accurate focus servo operation. Therefore, in order to eliminate such drawbacks, an improved plan was proposed using a photodetector divided into three parts by two parallel straight lines (see Japanese Patent Laid-Open Publication No. 55 B1328). Figure 6 shows the photodetector (1) used in this improvement plan.
5) Structure and differential amplification! ! f) A schematic diagram showing the connection with (12), Figure 7 is an explanatory diagram of its operation, and the other parts are the first
The hyC is configured as shown in the figure 1, light (σ mi detector (15)
has a three-division configuration divided by two parallel straight lines, and the width of the central region I, that is, the interval between the two divided straight lines, is the width of this photodetector (]B when the optical disc (3) is at the goldfish point position.
The amount of light received by the central area (■) which is smaller than the diameter of the spora 1 to (11), and the areas on both sides of it (■, III)
It is determined that the sum of the amounts of received light is equal to each other. By making the direction of the two divisions A1 and B the same as the t+j radial direction of the reflected light spot (II++) at the time of the out-of-focus point and the longer axis direction y of the reflected light spoilers 1 to (1, Ic), For the anti-light input box 1-(ll+1>, both sides n,
The amount of light received by the central region 1 is larger than the amount of light received by the central region 1+9l, and in the reflected light spot He), the amount of light received by the central region 1 is larger than the amount of light received by the both side regions (2) and (3). Therefore, the differential amplifier (12) provides a detection output with a polarity determined by the direction of the focus shift and a magnitude corresponding to the magnitude of the shift. Furthermore, the direction y of this dividing line is set to the reflected light spot (1
By matching the direction of displacement in 1), it is possible to eliminate the influence of deterioration of detection characteristics due to the displacement. However, even when such a parallel three-split photodetector (j5) is used, there are problems as described below, similar to the one shown in FIG. That is, the photodetector (15)
should be set correctly in the optical axis direction so that the incident optical spoilers 1 to 2 become circular when the optical spot (7) on the disk (3) is in focus. Due to placement errors of each optical component, the point forming the circular light beam may shift to the front or back of the photodetector (15) surface. In this case, the light spot I-(11) on the light detector (15) when in focus
has an elliptical shape, and a non-zero output signal fHp is generated from the differential amplifier (12) even though the disk (3) is in the focused position, which hinders accurate defocus detection. This kind of problem is exactly the same in the astigmatism method A-1 focus deviation detection device shown in Fig. 1, and in order to solve this problem, conventionally, the light detection flit is First, perform position side 1+' (in the optical axis direction of the photodetector,
The light spot on the IGvA 111 (when the disc was in the focused position) was made to be correctly circular. or,
Light detection of reflected light Spora I with Koji 1! In order to correctly determine the plane position of t', adjustments were also made within a plane perpendicular to the optical axis. In this way, simultaneous adjustment in the optical axis direction and C in the plane perpendicular to this, that is, 3-axis adjustment, is done:! It was made into part f and IE on a large scale, and it took a lot of adjustment time, and key '1:! This had the disadvantage of high cost. [Summary of the Invention] The present invention has been made to eliminate the drawbacks of the above-mentioned conventional device, and is as follows. Then, in the detection device, the light detection is divided into two straight cotton nozzles. The reflected light spots 11'1. In a fake. It is an object of the present invention to provide a defocus detection device for an optical disk head that is inexpensive in adjustment cost by making it possible to adjust the distance between the two dividing lines. [Embodiment of the Invention] Next, an embodiment of the present invention will be explained with reference to FIG.
Only the container (15) is shown, and the other parts are constructed in the same way as in FIG. That is, the photodetector (I5) is configured to be inclined so that the directions of the two dividing lines are non-parallel, and the direction along the dividing line in the plane perpendicular to the optical axis of the photodetector (15) is By moving the disc (3)
This )I(J detector (15) when is at the focused position r
Adjust the width of the central headrest 1 by t9 to the reflected light spoiler 1-position, and set the area l for light reception and the surface area 11.11.
One adjustment is made so that the light reception ambiguity caused by 1 becomes equal, that is, the offset of the defocus detection output from the differential amplifier (12) becomes 0 dom. As a result, the position of the photodetector (15) can be adjusted only in a plane perpendicular to the optical axis, and the adjustment cost can be reduced. By making the dividing line 2 non-parallel, the moving direction of the optical spot 1 of the photodetector when the tracking actuator is driven is approximately aligned with the direction of the dividing line (even if the tracking actuator is not affected by the However, by appropriately determining the inclination angle, it is possible to make the influence much smaller than when using a conventional 4-split photodetector.In addition, each of the above embodiments Now, we have shown an example of moving the objective lens (5) in the radial direction of the disk using the dragging actuator (14). what you made,
Alternatively, it is of course possible to apply the present invention to a structure in which the light source (1) is moved laterally. Furthermore, although the above description has been made with respect to an optical disk head that reads information from a disk, it is clear that the same may be applied to an optical disk head that records information on a disk. [Effects of the Invention] Since the present invention is configured as described above, it is possible to suppress the fluctuation in the out-of-focus detection characteristics when driving the 1-racking actuator to a level that does not have a practical effect, and moreover, the position adjustment of the photodetector can be done easily. The focus shift detection device 17r, which can be adjusted only in a plane perpendicular to the optical axis, is easy to adjust, takes a short adjustment time, and has low adjustment costs, can be provided at a relatively low cost! ). BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing a conventional optical disk head focus shift detection device, Figs. 2, 3, 4, and 5 are explanatory diagrams of its operation. A schematic diagram showing only the photodetector and differential amplifier used in the proposed improvement of the conventional device, FIG. 7 is an explanatory diagram of its operation, and FIG. 8 is a diagram showing only the photodetector used in the embodiment of the present invention. be. In the figure, (1) is a light source, (3) is an optical disk that is an information recording medium, (5) is an objective lens, (8) is a beam splitter, (9) is a 4-split photodetector, (10) is r '(i
! η lens, (12) is according to the focus shift (take out the symbol t, i',: dynamic amplifier, (1/I) is])
~The racking actuator (15) is a three-part photodetector. In addition, the same reference numerals in the figures indicate the same or corresponding parts. . Agent Masu Oiwa #t, (LT or 2f+) 4th (α) 5th (α) (b) Figure (shi)

Claims (1)

[Scope of Claims] (1) A light source, an objective lens for condensing a light beam emitted from the light source onto a track of an information recording medium on which an information signal is recorded in a track shape, a light beam emitted from the light source, and a light beam emitted from the light source; A beam splitter that separates a reflected light beam from a condensed spot on a recording medium that passes through the objective lens, a cylindrical lens that imparts astigmatism to the separated reflected light beam, and a reflected light beam that passes through this cylindrical lens. When the information recording medium is at the focal point of the objective lens, the reflected light is circular, and depending on whether it is located further or closer to the focal point, the reflected light is focused into an elliptical spot with long axes in x and y directions that differ by 90 degrees. A defocus detection device for an optical disk head, comprising a photodetector placed at a position where light is emitted, and a signal outputted from the photodetector according to the deviation of the objective lens from the focal point position of the recording medium. In this case, the elliptical reflected light spot of the photodetector is divided into three by two straight lines parallel to the major axis direction X or Y, and the interval between these two straight lines is , when the information recording medium is in focus, the amount of light received by the central area which is smaller than the diameter of the circular reflective spot C that is focused on it and which is divided by this dividing line. A focus deviation detection device for an optical disk head, characterized in that the sum of the amounts of light received by the inner region is determined to be equal to the sum of the amounts of light received by the inner region.
The displacement direction of the reflected light spot on the photodetector when the tracking actuator '9f (!+;t. The cylindrical lens and the photodetector are arranged so that the directions of the two parallel divisions coincide with each other. Detection device. (3) Light source, the emitted light beam from the light source C is
An objective lens condenses the light onto the recording medium of the information recording medium on which the φ signal is recorded in a track shape, the output beam C from the light source and the condensed light spot on the recording medium pass through the objective lens. a beam splitter that separates the reflected beam of
A cylindrical lens that imparts astigmatism to this separated single reflection source bundle, and a reflected light flux that passes through this cylindrical lens becomes circular when the information recording medium is at the focal point position of the objective lens,
Depending on whether it is located further or closer,
90 degrees different direction + The detector was divided into three parts by straight lines)'t, and the detector was divided into three parts (
'Mi, from the difference between the amount of light received by the central area of this photodetector and the sum of the amount of light received by the areas on both sides, a signal corresponding to the deviation from the focal point position of the objective lens of the recording medium is extracted. In a device for detecting a deviation of a fingernail of an optical disk, the directions of the dividing two-plane lines of the photodetector are tilted so as to be non-parallel, and the direction of the division 21 μ By moving in the direction along the line, there are 9 reflected light spots: J, Bow L-
A defocus detection device for an optical disk head, characterized in that the distance between the dividing lines can be adjusted by 91.