JPH0489637A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the number of parts by constituting a recording information signal detecting system and a spot position error signal detecting system out of an optical path splitter, a convergent lens, a double refraction type double image polarizing prism and a photodetector only. CONSTITUTION:Divergent light emitted from a laser diode 5 is turned into parallel light by a collimator lens 4, and is converged on the surface of an optical information medium 1 via a beam splitter 3 by an objective lens 2. Return light reflected from the surface of the optical information recording medium 1 is separated from the forward light again via the objective lens by the beam splitter. Then, the reflected return light obtained from the beam splitter 3 is detected by a photodetector 9 via the optical path splitter 6, the convergent lens 7 and the double refraction type double image polarizing prism 8, which are disposed to coincide with an optical axis of the reflected return light. Thus, since the recording information signal detecting system and the spot position error detecting system are not constituted independently, the number of parts are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording/reproducing apparatus, and more particularly to a signal detection system of an optical information recording/reproducing apparatus.

[Conventional technology]

Conventionally, this type of optical information recording/reproducing apparatus, as shown in FIG. Two beam splitters 48 and 49 for separating the transmitted light toward the optical information recording medium 1 and the reflected return light from the optical information recording medium 1
and an objective lens 2 that converges the light transmitted through these beam splitters 48 and 49 onto the plane of the optical information recording medium 1; , a converging lens 50 for converging the reflected return light separated by the beam splitter 48, a Wollaston prism 51 for separating the light beam converged by the converging lens 50 into two orthogonal polarization components, a recording information signal detection system comprising a two-split photodetector 52 that independently detects two light beams separated by a prism 51; and a recording information signal detection system that separates the reflected return light from the optical information recording medium 1 that has passed through the beam splitter 48; a converging lens 53 for converging the reflected return light separated by the beam splitter 49, and a converging lens 53 for converging the reflected return light separated by the beam splitter 49, and a light beam converged by the converging lens 50 to be used as track error detection light and focus error detection light. a beam splitter 55 for separating the light into light, and a two-split photodetector 54 for detecting track errors.
and a spot position error signal detection system comprising a knife 56 for detecting focus errors using the knife method, and a two-split photodetector 54; the recorded information signal detection system and the spot position error signal detection system are independent. The structure was as follows.

[Problem to be solved by the invention]

The above-described conventional optical information recording and reproducing apparatus has a disadvantage in that the number of component parts increases because the recorded information signal detection system and the spot position error detection system are configured independently. Furthermore, since there are two beam splitters between the laser diode and the objective lens, there is a drawback that when trying to increase the efficiency of using light for signal detection, the efficiency of using forward light becomes low. At the same time, there is also the drawback that the amount of light distributed to the spot position error detection system fluctuates depending on the recording information signal, and recording information wraps around the spot position error detection signal. Furthermore, since focus error detection is performed using the knife method, a certain amount of light is blocked by the knife, resulting in a disadvantage that the light utilization efficiency of the focus error detection system is low.

[Means to solve the problem]

The optical information recording and reproducing apparatus of the present invention includes a laser diode, a collimator lens for converting diverging light emitted from the laser diode into parallel light, and a collimator lens for collimating the divergent light emitted from the laser diode and the light directed from the laser diode toward an optical information recording medium. a beam splitter that separates reflected and returned light from the optical information recording medium; an objective lens that converges the light that passes through the beam splitter and goes toward the optical information recording medium onto the surface of the optical information recording medium; and the optical information recording medium. The reflected return light from the recording medium is divided into at least four areas in a plane perpendicular to the reflected return light optical axis, and at least four components of the divided reflected return light are directed to the reflected return light optical axis. a converging lens that converges at least four beams separated by the optical path splitter, and at least four beams converged by the converging lens; a birefringent double-image polarizing prism, each of which separates into at least eight polarized light components orthogonal to each other; and at least four two-split light detection sections that independently detect the light beams separated into the at least eight polarized light components. The photodetector is composed of at least four independent photodetectors.

Further, the track pitch of the optical information recording medium is set to P (μm
).

Let the wavelength of the light emitted from the laser diode be λ(
nm), the numerical aperture of the objective lens is NA and the radius of the entrance pupil is a<mm), and (NA - Pλ)≦0,
r=a-λ/(NA-P), and the optical path splitter divides the track direction of the optical information recording medium into Y in a plane perpendicular to the optical axis, with the intersection of the optical axis and the plane as the origin. When the direction perpendicular to the track is the X-axis, the dividing line or approximately the origin of the optical path splitter is the starting point, and the point T (r/2. and,
point, J(r/2.-FC"= extension line passing through FU and point K
(-r/2, Fn "=PdT) and the point L
(-r/2, -a''-r'')/4).

Further, the four regions formed by the optical path splitter start from the origin of the dividing line, and the region sandwiched between the extension line passing through the point L and the extension line passing through the point (■) is called an area A, and the point (■) is defined as an area A. Area B is the area sandwiched between the extension line passing through the point J and the extension line passing through the point J. Area C1 is the area sandwiched by the extension line passing through the point J and the extension line passing through the point J. A region sandwiched between an extension line and an extension line passing through the dot is defined as a region, and the components of the return light divided into the regions A, B, C, and D are made to correspond to each region, and the return light is Ingredients A, B
, C and D, and after passing through the convergent lens and the birefringent double-image polarizing prism, these are two polarized light components that are orthogonal to each other, luminous flux A0 and luminous flux Ae, luminous flux Bo and luminous flux Be, and luminous flux C0 and luminous flux. Ce and luminous flux. and a light beam De, and each of the light receiving surfaces of the at least four two-split light detection sections of the photodetector is a light receiving surface a.
, b, c, d, e, f, g, and h, and the light-receiving surfaces of the at least four independent photodetectors are respectively on the light-receiving surface, j, k, and 9, and the light flux Ao is on the light-receiving surface. a and b, the light beam Ae is on the light-receiving surfaces e and f, the light beam Bo is on the light-receiving surfaces C and d, the light beam Be is on the light-receiving surfaces g and 1], the light beam C0 is on the light-receiving surface, j, the light flux Ce is irradiated onto the light receiving surface 9, the light flux Do is irradiated onto the light receiving surface d, and the light flux De is irradiated onto the light receiving surface, and at that time each of the light receiving surfaces a and b
, c, d, e, f, g, h, i.

The outputs of j, 1 (and 9) are V (a) and V (b
), v(c), V(d), V(e), V
(f), V (g), V (h), V
(i), V(j), and V(ritoshina), as focus error F, F= {V(a) 10V(d) fV(e) fV(h)
+{V(c) fV(b) fV(g) 10V(f)
), and as an error signal T, T={V(i)fV(k))={V(j)fV(t))
It has a detection means for detecting, and as a magneto-optical signal, {V (a) + V (b) 10V (c) + V
(d) + V (i) fV(j)) −fV(e)
fV(f) fV(g) 10V(h) +v(k) fV(
1) ), and as a signal of the fluctuation in the amount of reflected light, {V(a) fV[b) fV(c) fV(d) f
It has a detection means for detecting V(e) V(f) fV(g) fV(h).

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 2 is a diagram showing an outline of the optical information recording/reproducing apparatus of the present invention. In FIG. 2, diverging light emitted from a laser diode 5 is made into parallel light by a collimating lens 4, and is focused onto an optical information recording medium 1 by an objective lens 2 via a beam splitter 3. The reflected return light from the surface of the optical information recording medium 1 is separated from the outbound light by the beam splitter 3 via the objective lens 2 again. The reflected return light obtained from the beam splitter 3 is then sent to a photodetector via an optical path splitter 6, a converging lens 7, and a birefringent double-image polarizing prism 8, which are arranged in alignment with the optical axis of the reflected return light. 9
Detected by

FIG. 1 is a basic configuration diagram showing an embodiment of the present invention. The basic configuration diagram shown in FIG. 1 uses a 4-split prism 45 as the optical path splitter 6 shown in FIG. 2, a Wollaston prism 46 as the birefringent double-image polarizing prism 8, and
A 12-divided photodetector 47 is used as a photodetector.

FIG. 3 is a diagram showing the pattern of the return light beam and the settings of the X-axis and Y-axis with respect to the return light optical axis.

FIG. 4 is a diagram showing divided regions in one embodiment of the optical path splitter.

FIG. 5 is a diagram showing the relationship between the return beam and the pattern in one embodiment of the optical path splitter of FIG. 4.

Here, the track pitch of the optical information recording medium 1 used is 16 μm, the wavelength of the light emitted from the racer diode 5 used is 0.83 μm, and the numerical aperture of the objective lens 2 is 0.
5 and the radius of the entrance pupil is 2.15 mm, as shown in FIG. 3, FIG. 4, and FIG. The intersection of the optical axis of the return light and a plane orthogonal thereto is the origin 0, and the Y axis is in the track direction of the optical information recording medium 1, and l
- When the X-axis is taken in the direction perpendicular to the rack, the dividing line is a half line starting from the point (sail 0) and passing through the points (1, 12, 1, 84), respectively, with the unit of mm being the point Point (1,12, -1,84) starting from (0,0)
A half-line passing through, starting from point (sail 0) and point (-1, 12, -1, 84)
A half-line passing through, starting from point (0,0) and starting at point (-1,1,2,1,84
), and is divided into four regions, namely, region A (58), region B (59), region C (60), and region D (61). And these areas A (58)
~Area D (61) uses a four-split prism 45 in which the fibers perpendicular to the optical axis have independent angles, and the rear surface of the optical path is parallel to the orthogonal plane.

It goes without saying that the effect of the four-split prism 45 remains the same even if the planes parallel to the orthogonal plane and the planes having four independent angles are reversed in front and back with respect to the optical path.

Moreover, the optical path splitter 6 is not limited to a prism, and has the above-mentioned division areas A (58) to area D (61), and the optical path splitter 6
It is sufficient that the optical path of the light passing through area A (58) to area D (61) after passing through has an independent angle with respect to the optical axis.
It is possible to use a device that uses diffracted light such as a hologram element or a device that combines a reflecting mirror.
It is also possible to form it integrally with.

Next, the components of the reflected return light 62 divided by the division areas A to D of the optical path splitter 6 are defined as return light components A, B, C, and D in correspondence with the respective areas.

These four return light components A-D pass through the converging lens 7 and the Wollaston prism 46, and the two orthogonal
The light is separated into two polarized components.

Here, with respect to the polarized light components separated by the Wollaston prism 46, the subscript 0 is added to the ordinary ray, and the subscript e is added to the extraordinary ray. That is, the four return light components A to D are Ao, A, , Bo, Be, and Co, respectively.
, Ce, D. and De are separated into eight beams.

Note that the birefringent double-image polarizing prism 8 is a birefringent polarizing prism as long as it can separate the two components of ordinary light and extraordinary light, and it goes without saying that a Rochon prism or the like can be used as another method.

Next, the eight luminous fluxes Ao, Ae, BoBe, C, .
Ce, Do, and D8 are respectively converged on each light receiving surface of the photodetecting section of the 12-divided photodetector 47 shown in FIG.

Then, as shown in FIG.
) and the light receiving surface b (16), the luminous flux A, (38) is the light receiving surface e (19) of the two-split light detection section.
) and the light-receiving surface f (20), the light beam C6 (41 is the light-receiving surface c (17) of the two-split light detection section)
and the light-receiving surface d18), the light flux Ce (42 is the light-receiving surface g of the two-split light detection section (21)
and the light-receiving surface h22), the light beam Bo (39 is on the light-receiving surface j (34), the light beam B,...
(40 is the light flux De on the light receiving surface Q (36). (43 is the light receiving surface) On (33) is the light flux De (44 is the light receiving surface k <
35>, 12-divided photodetectors 47 are arranged so as to coincide with each other. At this time, the 12-divided photodetector 4
Each light receiving surface of 7 a, b, c, d, e, f, gh, top, j,
and 9 outputs respectively to V(a).

V (b), V (c), V (d), V (e), V
(f), V (g), V (h).

When V(i), V(,i), and V(ritoshi, (1)
The focus error F is fV(a) fV(d) LV(e) 10V(h) 1
{V (c) 10 V (b) + V (
g) + V (f) )1? (2) The error signal T is T={V(i) fV(k)) {V(j)+V←D) (3) The magneto-optical signal is {V(a) 10V(b) fV(c ) fV(d) f
V(i) 10'V(j) )={V(e) fV(f)
fV(g> fV(h) fV(k) fV(1)
) (4) Signal of reflected light amount fluctuation (write-once type/phase change signal) or fV(a)+VD+)fV(c)fV(d) 10V(e
) ±V (f) + V (g) + V (h))
A calculation is performed using a calculation circuit (not shown) so that the recording information signal and the spot position error signal are detected.

〔Effect of the invention〕

As explained above, the optical information recording/reproducing apparatus of the present invention can perform the recorded information signal detection system and the spot position error signal detection system using only an optical path splitter, a converging lens, a birefringent double-image polarizing prism, and a photodetector. This configuration has the effect of reducing the number of parts. Further, with this configuration, since there is no light shielding part due to a knife in the error detection section, the efficiency of light utilization is increased and it is possible to increase the signal amplitude. In addition, since the recording information signal and the spot position error signal are detected using the same light, it is possible to keep the reflectance of the beam splitter low, and the number of beam splitters is reduced to one. This has the effect of increasing the efficiency of using light in the optical path from the laser diode to the optical information recording medium. That is, since sufficient light output power can be obtained for the forward optical path, there is also the effect that the reflectance of the beam splitter can be increased to increase both the recording information signal and the spot position error signal. Furthermore,
Since the optical path splitter extracts the light from which most of the first-order diffracted light components have been removed as a beam for focus error detection, it is possible to obtain a stable focus error signal with very little wrap-around of the track error signal, and also Since substantially the entire amount of reflected light is used to detect the substrate position error signal, there is an effect of significantly reducing the wraparound of the error signal of the magneto-optical signal.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an outline of the optical information recording/reproducing apparatus of the present invention, and FIG.
The figure shows the pattern of the return light beam and the X with respect to the return light optical axis.
FIG. 4 is a diagram showing the division areas in one embodiment of the optical path splitter, and FIG. 5 is a diagram showing the return light beam and pattern in one embodiment of the optical path splitter in FIG. 4. FIG. 6 is a diagram showing the light receiving surface of a 12-split photodetector, which is an example of a photodetector, and FIG. 7 is a diagram showing the relationship between 1 and 2 shown in FIG.
FIG. 8 is a diagram showing an example of the relationship between the light receiving surface of a two-split photodetector and the irradiated beam spot, and FIG. 8 is a basic configuration diagram showing a conventional example. 1... Optical information recording medium, 2... Objective lens, 3...
・Beam splitter, 4...Collimating lens, 5.
・Laser diode, 6... Optical path splitter, 7...
Converging lens, 8... Birefringent double-image polarizing prism, 9...
...Photodetector, 10...Origin 0111...Point ■, 1
2...Point J13...Point K, 14...Point, 15~
22. 33-36... Light-receiving surface, 37-44... Luminous flux Ao, AeB, ~De45... 4-split prism, 46
...Wollaston prism, 47...12-divided photodetector, 58...area A, 59...area B, 60...
- Area C161... Area D, 62... Reflected return light.

Claims (1)

[Claims] 1. A laser diode, a collimating lens for converting diverging light emitted from the laser diode into parallel light, and light directed from the laser diode toward an optical information recording medium and from the optical information recording medium. a beam splitter that separates the reflected return light from the optical information recording medium; an objective lens that focuses the light transmitted through the beam splitter and directed toward the optical information recording medium onto the surface of the optical information recording medium; The reflected return light is divided into at least four regions in a plane perpendicular to the optical axis of the reflected return light, and at least four components of the divided reflected return light are each independent with respect to the optical axis of the reflected return light. an optical path splitter that separates the beams so as to have an exit angle, a converging lens that converges the at least four beams separated by the optical path splitter, and the at least four beams that are converged by the converging lens.
a birefringent double-image polarizing prism that separates each of the two light beams into at least eight mutually orthogonal polarization components; and at least four two-split light detectors that independently detect the light beams separated into the at least eight polarization components. and a photodetector consisting of a section and at least four independent photodetecting sections, wherein the optical path splitter, the converging lens, the birefringent double-image polarizing prism, and the photodetector detect light from the optical information recording medium. An optical information recording/reproducing apparatus, characterized in that the apparatus is arranged so as to be aligned with the optical axis of the reflected return light. 2. The track pitch of the optical information recording medium is P (μm)
, the wavelength of the light emitted from the laser diode is λ
(nm), the numerical aperture of the objective lens is NA, the radius of the entrance pupil is a (mm), (NA・P−λ)≦0, and r=a・λ/(NA・P), The optical path splitter is configured such that, in a plane perpendicular to the optical axis, the intersection of the optical axis and the plane is the origin, the track direction of the optical information recording medium is the Y axis, and the direction orthogonal to the track is the X axis. When used as an axis, the dividing line of the optical path splitter starts from approximately the origin, and the extension line passes through point I (▲ where there are mathematical formulas, chemical formulas, tables, etc.), and the extension line which passes through point J (▲ where there are mathematical formulas, chemical formulas, tables, etc.). It consists of an extension line passing through point K (▲There are mathematical formulas, chemical formulas, tables, etc.▼), and an extension line passing through point L (▲There are mathematical formulas, chemical formulas, tables, etc.▼) 2. The optical information recording and reproducing apparatus according to claim 1, wherein: 3. The four areas formed by the optical path splitter start from the origin of the dividing line, and the area sandwiched between the extension line passing through the point L and the extension line passing through the point I is called area A, and the point I is defined as area A. Area B is the area sandwiched between the extension line passing through the point J and the extension line passing through the point J. Area C is the area sandwiched between the extension line passing through the point J and the extension line passing through the point J. The area sandwiched between the extension line passing through the point L and the extension line passing through the point L is defined as an area D, and the components of the return light divided into the areas A, B, C, and D are made to correspond to each area, and the return light is Light components A, B
.
The light flux B_o and the light flux B_e, the light flux C_o and the light flux C_e, and the light flux D_o and the light flux D_e are separated, and the light-receiving surfaces of the at least four two-split light detection sections of the photodetector are light-receiving surfaces a, b, and c, respectively. , d, e, f, g, and h, and the light receiving surfaces of the at least four independent photodetectors are light receiving surfaces i, j, k, and l, respectively, and the light flux A_o is on the light receiving surfaces a and b. , the luminous flux A_
e is on the light receiving surfaces e and f; the light beam B_o is on the light receiving surfaces c and d; the light beam B_o is on the light receiving surfaces c and d;
e is on the light-receiving surfaces g and h, the light beam C_o is on the light-receiving surface j, the light beam C_e is on the light-receiving surface l, the light beam D_o is on the light-receiving surface i, and the light beam D_e is on the light-receiving surface k. irradiated, each of the light receiving surfaces a at that time
, b, c, d, e, f, g, h, i, j, k and l as V(a), V(b), V(c), V(d), respectively.
, V(e), V(f), V(g), V(h), V(i)
, V(j), and V(l), as the focus error F, F={V(a)+V(d)+V(e)+V(h)}-{
The optical information recording and reproducing device 4 according to claim 1, characterized in that it is equipped with a detection means for detecting V(c)+V(b)+V(g)+V(f)}; An information recording/reproducing device using the following formula, where the error signal T is T={V(i)+V(k)}−{V(j)+V(l)}
What is claimed is: 1. An optical information recording and reproducing device characterized by comprising a detection means for detecting. 5. The optical information recording/reproducing device according to claim 3, wherein the magneto-optical signal is {V(a)+V(b)+V(c)+V(d)+V(i)
+V(j)}-{V(e)+V(f)+V(g)+V(
h)+V(k)+V(l)} An optical information recording/reproducing device characterized by comprising a detection means for detecting the following. 6. The optical information recording/reproducing device according to claim 3, wherein the signal of the reflected light amount variation is {V(a)+V(b)+V(c)+V(d)+V(e)
+V(f)+V(g)+V(h)} An optical information recording/reproducing device characterized by comprising a detection means for detecting the following.