JP2813255B2 - Optical tape memory device, signal detection method for optical tape memory device, and optical tape cassette - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical tape memory device, a signal detection method used in the optical tape memory device, and an optical tape cassette containing an optical tape and used in the optical tape memory device.

[0002]

2. Description of the Related Art Optical disks are widely known as memory media for recording and reproducing information by light. On the other hand, the use of "optical tape" is intended as a memory medium suitable for ultra-large-capacity storage that does not require much access time. The optical tape is a tape-shaped medium on which information is recorded and reproduced by light.

[0003] Recording and recording of information on such an optical tape.
As a method of performing reproduction, an optical information recording / reproducing device (in an optical disc system) provided in the tape guide while spirally winding an optical tape around the outer peripheral surface of a transparent cylindrical tape guide and feeding the tape at a low speed. 2. Description of the Related Art A technique is known in which recording and reproduction are performed by rotating an optical pickup (a device corresponding to an optical pickup) together with a tape guide at a high speed (Japanese Patent Laid-Open No. 1-19).
9331).

In this prior art, since an optical information recording / reproducing apparatus rotates at high speed, a strong centrifugal force acts on an optical element constituting the apparatus, and the optical element is deformed by a stress due to the centrifugal force, or the optical element becomes long. There is a problem that the alignment of the optical elements is likely to be out of alignment with the use of the period. In addition, the mass of the rotating portion becomes large, making it difficult to rotate at high speed, making it difficult to increase the speed of recording / reproducing.

Further, since the cylindrical tape guide rotates at a high speed with respect to the optical tape fed at a low speed, there is a problem that the optical tape is rubbed by the tape guide and the optical tape is easily damaged.

In the conventional method, the optical tape is loaded onto the tape guide when recording / reproducing the optical information. Therefore, the optical tape cannot be completely sealed. There is also a problem that it is easily contaminated by dust.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the optical system of the optical information recording / reproducing apparatus is hardly affected by centrifugal force, so that high-speed recording / reproducing is possible. An object of the present invention is to provide an optical tape memory device capable of reproduction, a signal detection method used in the device, and an optical tape cassette that can effectively prevent contamination of the optical tape by dust.

[0008]

According to an optical tape memory device of the present invention, an optical tape having a track set at a predetermined angle with respect to the longitudinal direction of the tape is spirally formed on the outer peripheral surface of a transparent cylindrical tape guide. A device that records and / or reproduces information on an optical tape by light while winding and feeding the tape at a low speed, wherein an optical system for recording and / or reproducing information by light is a movable part. And a fixed part. The “movable part” has a condensing optical system that rotates at high speed within a tape guide for recording and / or reproducing information. The “fixed portion” has a light source that emits light to be condensed on the recording surface of the optical tape by the movable portion, and a signal detection system for detecting a signal by returning light from the recording surface.
The “signal detection system” detects the return light from the recording surface of the optical tape by 2
A beam splitter for splitting, a Foucault detection system for detecting a focus error signal by the Foucault method for one light beam split by the beam splitter by a Foucault method, and a cross-quadrant light receiving element for receiving the other split light beam And

Tracking error signal: TE is cross 4
When the output signals from the respective light receiving units of the split type light receiving element are defined as I ₁ , I ₂ , I ₃ , and I ₄ around a predetermined direction, and the rotation angle of the condensing optical system of the movable unit is φ, TE = ( I ₁ −I ₃ ) sin φ + (I ₂ −I ₄ ) cos φ. In addition, 4 in the Foucault detection system described above.
When the output signals from the respective light receiving units of the continuous light receiving unit type are K ₁ , K ₂ , K ₃ , and K ₄ in a predetermined direction, {(K ₂ + K ₃ ) − (K ₁ + K ₄ )}. A signal obtained by passing the signal through a low-pass filter to remove high-frequency components is referred to as a focus error signal: FE.

An optical tape memory device according to a second aspect of the present invention is an optical tape memory device comprising: an optical tape having a track set at a predetermined angle with respect to the longitudinal direction of the tape and spirally wound around the outer peripheral surface of a transparent cylindrical tape guide; A device for recording and / or reproducing information by light on the optical tape while feeding the optical tape ", wherein an optical system for recording and / or reproducing information by light comprises a movable part and a fixed part. Is done.
The “movable part” has a condensing optical system that rotates at high speed within the tape guide for recording and / or reproducing information.

The "fixed portion" has a light source for emitting light to be condensed on the recording surface of the optical tape by the movable portion, and a signal detection system for detecting a signal by returning light from the recording surface. The “signal detection system” includes a beam splitter that divides the return light from the recording surface of the optical tape into two, and a pair of non-point luminous fluxes that make the luminous fluxes divided by the beam splitter into astigmatic luminous fluxes in directions orthogonal to each other. It has a point light beam forming optical system, and a pair of cross-shaped four-division light receiving elements that respectively receive the light beams that have been converted to non-point light beams by these non-point light beam forming optical systems.

A tracking error signal: TE is obtained by converting an output signal from each light receiving portion of one of the light receiving elements into a signal I around a predetermined direction.
₁ , I ₂ , I ₃ , I _4, and the rotation angle of the focusing optical system of the movable part is φ
Then, TE = (I ₁ −I ₃ ) sin (φ−π / 4) + (I ₂ −I ₄ ) cos (φ−π / 4) is obtained. The focus error signal: FE is
FE = {(I ₁ + I ₃ ) − (I ₂ + I ₄ )} − {(The output signals from the respective light receiving units of the other light receiving element are set to J ₁ , J ₂ , J ₃ , and J ₄ around a predetermined direction. J ₁ + J ₃ ) − (J ₂ + J ₄ )｝.

According to a third aspect of the present invention, there is provided a "signal detecting method for an optical tape memory device", wherein the signal detecting method is implemented in the optical tape memory device according to the first or second aspect, that is, the tracking error signal. : TE and a focus error signal: FE.

An optical tape cassette according to a fourth aspect is characterized in that "a transparent cylindrical tape guide is hermetically provided in a closed container for winding and storing the optical tape". But,
In carrying out the apparatus or method of claims 1 to 3, it goes without saying that cassettes other than the optical tape cassette of claim 4 can be used.

[0015]

As described above, in the optical tape memory device of the present invention, the "optical system for recording and / or reproducing information" is constituted by the movable part and the fixed part, and the optical element is provided in the movable part. Only the focused optical system is rotated at high speed.

The tracking error signal TE is obtained by using the output of a four-part cross-shaped light receiving element, and the rotation angle of the movable part:
Obtained by an operation involving φ.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment will be described below. Prior to the embodiment, an outline of an optical tape memory device will be described with reference to FIG. In FIG. 1A, reference numeral 10 denotes a light source, reference numeral 11 denotes a polarizing beam splitter, reference numeral 12 denotes a 波長 wavelength plate, reference numeral 13 denotes a collimating lens, reference numeral 14 denotes a cylinder lens, and reference numeral 15 denotes a light receiving element. These light sources 1
0, polarizing beam splitter 11, quarter-wave plate 12,
The collimating lens 13, the cylinder lens 14, and the light receiving element 15 constitute a "fixed part" of an optical system for recording and / or reproducing information. Reference numeral 16 denotes a mirror prism,
Reference numeral 17 denotes an objective lens, reference numeral 18 denotes a support, reference numeral 19 denotes a rotation axis, and reference numeral 20 denotes a tracking adjustment unit such as a piezoelectric actuator. Mirror prism 16 and objective lens 1
Reference numeral 7 denotes a “movable part” of the optical system. The support 18 and the rotation shaft 19, and the rotation drive device and the tracking adjustment unit 20 (not shown) constitute a part of a drive system. Although not shown, the objective lens 17 can be displaced in the optical axis direction by an actuator (electromagnetic or piezoelectric type) for focus control.

Reference numeral 21 denotes a sealed container of an optical tape cassette.
Reference numeral 22 denotes a tape guide, and reference numeral 23 denotes an optical tape.

In FIG. 1A, a light source 10 is a semiconductor laser or the like. The light beam from the light source 10 is reflected by the polarizing beam splitter 11 to the left in the figure, converted into circularly polarized light by the quarter-wave plate 12, then converted into a parallel light beam by the collimating lens 13, and emitted from the fixed part. The collimator lens 13 is movable in an optical axis direction and a direction orthogonal to the optical axis for position adjustment. The parallel light beam emitted from the fixed portion is deflected at right angles by the mirror prism 16 and is condensed on the recording surface of the optical tape 23 by the objective lens 17.

Here, the state of the optical tape 23 is shown in FIG.
This will be described with reference to FIG. This figure shows an optical tape cassette in which the optical tape 23 is stored. This optical tape cassette is an embodiment of the invention according to claim 4. Code 21
The optical tape 23 is wound and stored in a tape winding reel 25 in the closed container indicated by. Inside the container 21, a pair of guide rollers 24 and a cylindrical tape guide 22 are hermetically mounted.

The optical tape 23 is pulled out from the reel 25, is spirally wound around the outer peripheral surface of the tape guide 22 via the guide roller 24, and is again wound on the reel 25 via the guide roller 24.

The tape guide 22 is formed of a transparent material such as glass or plastic, and is integrated with the container 21 in this example.
3 slides on the outer peripheral surface of the tape guide 22. As another form, “the tape guide 22 can be rotated with respect to the container 21 and rotates with the movement of the optical tape when the tape is fed”.

As shown in FIG. 1D, the tracks of the optical tape 23 are set at a predetermined angle with respect to the longitudinal direction of the tape. The reason that the setting direction of the track T is inclined with respect to the longitudinal direction of the tape is that the optical tape is spirally wound around the outer peripheral surface of the tape guide 22, so that the direction of the track T in the wound state is changed. This is to make the light spot parallel to the moving direction of the light spot by the objective lens 17.

When the optical tape cassette is set in the optical tape memory set, the optical system of the movable part is
2, the mirror 16 and the objective lens 17 are integrally rotated by the drive shaft 19. Therefore, the light beam condensed by the objective lens 17 passes through the transparent tape guide 22 from the inside and is condensed as a light spot on the recording surface of the optical tape 23, and scans the track of the optical tape 23.

At this time, the focus control is performed by displacing the objective lens 17 in the optical axis direction by the above-mentioned actuator (not shown), and the tracking is performed by the tracking control unit 20 shown in FIG. It is performed by displacing the direction. As another tracking method, “the objective lens 17 may be displaced in a direction perpendicular to the optical axis” may be used. The focus control may be performed by displacing the collimating lens 13 in the optical axis direction by an electromagnetic type actuator instead of displacing the objective lens 17 in the optical axis direction by an actuator. By adopting such a method, it is not necessary to provide an actuator in the movable part, so that the movable part can be rotated at a higher speed, which is a preferable embodiment.

The light applied to the optical tape 23 is the optical tape 2
3, the light is emitted from the movable portion via the objective lens 17 and the mirror prism 16, becomes return light, enters the collimator lens 13, is converted into a convergent light beam by the lens 13, and is converted into a 波長 wavelength plate. The light is converted into linearly polarized light whose polarization direction has been rotated by 90 degrees from that of the original light, and passes through the polarization beam splitter 11.

Subsequently, a cylinder lens 14 shown in FIG.
When the light is further focused in the vertical direction in (a), the return light becomes a non-point light flux. That is, the return light that has been given a converging tendency by the collimating lens 13 is given astigmatism by the cylinder lens 14 and is converted into astigmatic light. Therefore, the collimating lens 13 and the cylinder lens 14 constitute the "astigmatic light beam forming optical system" in this embodiment.

The return light that has been turned into a non-point light beam enters the light receiving element 15. As shown in FIG. 1B, the light receiving element 15 is a “cross-shaped four-division light receiving element” in which the light receiving portion is divided into four crosses.
It is. As shown in the figure, the four divided light receiving units are denoted by reference numerals 15-1, 15-2, 15-3, and 15-4 in the counterclockwise direction, and the light receiving units 15-1, 15-2, and 15-3 are provided. sequentially I ₁ output from 15-4, I _2, I _3, and I _4. These outputs may be amplified as needed.

Hereinafter, the "signal detection method" according to the example of FIG.
Prior to that, the specifications of the apparatus will be briefly described. The outer diameter of the tape guide 22 is 25 mm, and the rotation speed of the movable part of the optical system is 900 rpm. The optical tape 23 has a width of 12.5 mm and a track interval of 1.6 μ.
m, the bit interval is 1.0 μm, the length is 15 m,
The tape feed speed is 5.2 mm / sec and the total recording amount is 10
¹¹ bits, data transfer rate is 1.2 Mb / sec, and access time is 15 seconds. When information is recorded in the optical tape 23 in a “form that causes a change in the amplitude of the return light”,
That is, a write-once type using TeO ₂ or an organic dye, or a phase change type rewritable type using Ge—Sb—Te is assumed.

In the case of the example in the description, the "detection of the focus error signal" may use an astigmatism method well known in relation to the conventional optical disk system. That is, the signal {(I ₁ + I ₃₎ using the I ₄ to not the output I ₁ - (I ₂ +
If I ₄ )｝ is set as a focus error signal and servo control is performed to set this to 0, focus control can be realized.

On the other hand, the tracking is different from that of the optical disk system. That is, the optical tape scanning method presupposed in the present invention is called a "helical scan" because the optical tape is spirally scanned, but in the present invention, the optical system for recording and / or reproducing information is movable. The scanning of the optical tape is performed solely by rotating the movable part. Therefore, when viewed from the position of the light receiving element 15, the direction of the track is relative to the light receiving element 15 with the rotation of the movable part. To rotate. That is, of the components constituting the light pattern obtained on the light receiving element 15, the component that gives a tracking error is transmitted to the light receiving element 15 together with the rotation angle φ of the condensing optical system of the movable part while maintaining the shape of the light pattern. It turns around. The rotation of the light pattern does not affect the focus control. This is because the focus error control is performed so that the shape of the light pattern is circular.

When the rotation of the optical pattern is taken into consideration, the conventionally known tracking in the optical disk system cannot be directly applied to the scanning of the optical tape.

In such a case, a tracking error signal TE can be obtained as follows. In relation to the light receiving element 15, the light intensity of the return light on the light receiving element 15 at a position where the position of the movable portion is a reference (φ = 0: the direction of the track at this time is referred to as a track reference direction) In general, the following can be written using the coordinate angle θ set on the element 15. i (θ) = a ₀ + {a (n) sin (nθ) + b (n) cos (nθ)} (1) In this equation, n is a parameter having a suffix character, and the sum is Take from 0 to. The intensity i (θ) of the return light when the movable part of the optical system rotates by φ from the reference position is as follows.

I (θ + φ) = a ₀ + {[a (n) sin {n (θ + φ)} + b (n) cos {n (θ + φ)}] + {c (n) sin (nθ) + d (n) cos (nθ)｝ (2) In equation (1), the first and third terms on the right side are components that do not change with the rotation angle φ, and the first term is a data signal and the third
The term represents the focus error signal, and the second term that changes with the rotation angle φ gives the tracking error signal.

The amount of light received at each light receiving portion of the light receiving element 15 divided into four crosses can be obtained by performing integration ∫i (θ + φ) dθ (3) for each light receiving portion.

In the expansion of the parameter (n) in the equation (1), it is assumed that the higher-order term of n ≧ 3 is negligibly small, and generality is not lost. So (2)
Taking into account the term of n = 2 in the expansion of the equation, the outputs I ₁ to I ₄ from the respective light receiving units obtained by the integration (3) are as follows.

I ₁ = (π / 2) a ₀ + √ [2] a (1) sinφ + √ [2] b (1) cosφ + a (2) sin2φ + b (2) cos2φ + √ [2] d (1) + d (2) (4) I ₂ = (π / 2) a ₀ + √ [2] a (1) cosφ−√ [2] b (1) sinφ−a (2) sin2φ−b (2) cos2φ + √ [ 2] c (1) −d (2) (5) I ₃ = (π / 2) a ₀ −√ [2] a (1) sinφ−√ [2] b (1) cosφ + a (2) sin2φ + b ( 2) cos2φ−√ [2] d (1) + d (2) (6) I ₄ = (π / 2) a ₀ −√ [2] a (1) cosφ + √ [2] b (1) sinφ−a (2) sin2φ-b (2) cos2φ-√ [2] c (1) -d (2) (7) Here, the symbol √ [] means taking the square root of the quantity in [].

In the following description, a known push-pull method is assumed as tracking. In this method, the tracking error signal is asymmetric in a direction orthogonal to the track because the tracking error signal is a difference between return lights from both sides of the track. From this, in the second term in the above equation (1),
The coefficient b (n) of the even function does not represent a push-pull signal,
It can be seen that the odd function coefficient a (n) represents a push-pull signal. Among the coefficients a (n), a for n = 1
(1) is the largest, so this is essentially a push
It can be considered to represent a pull signal. By using the equations (4) and (6), I ₁ −I ₃ {2} [2] a (1) sin φ + 2} [2] b (1) cos φ (8) is obtained, and (5) (7) Using the equation, I ₂ −I ₄ {2} [2] a (1) cosφ−2 {[2] b (1) sinφ (9) is obtained.

It should be noted that in the embodiment being described, the change in the focus error is that the light pattern shown in FIG. 1 (b) only becomes horizontal or vertical as shown in FIG. In the focus error signal represented by the third term, c (1) and d (1) can be set to ≒ 0, and this omission is performed when calculating the equations (8) and (9).

Equation (8) is multiplied by cosφ, and equation (9) is multiplied by s
Multiplying by inφ and adding them together gives (I ₁ −I ₃ ) sin φ + (I ₂ −I ₄ ) cos φ = 2√ [2] a (1) (10)

This equation includes only a (1), and as described above, a (1) represents a push-pull signal.
By using the left side of the equation (10) as the tracking error signal TE, tracking by the push-pull method can be realized.

In the track reference direction, that is, in the direction of φ = 0, the above TE becomes (I ₂ −I ₄ ) from the equation (10), and the value of (I ₂ −I ₄ ) at this time is given by the equation (9). 2√ [2]
a (1). This indicates that the TE always gives a tracking error signal regardless of the rotation angle φ.

Next, the focus error signal will be described.

Using equations (4) and (6), I ₁ + I ₃ = πa ₀ + 2a (2) sin2φ + 2b (2) cos2φ + 2d (2) (14) I ₂ + I ₄ = πa ₀ -2a (2) sin2φ-2b (2) cos2φ-2d (2) (15) is obtained.

As described above, the focus error signal is (I ₁ +
Since (I ₃ ) − (I ₂ + I ₄ ), when this is calculated by the equations (14) and (15), (I ₁ + I ₃ ) − (I ₂ + I ₄ ) = 4d ₂ + 4a (2) ) sin2φ + 4b (2) cos2φ (16) In the equation (16), the first term 4d ₂ gives a focus error signal. That is, in general, d
₂ >> a (2), b (2), Equation (16) is substantially
(I ₁ + I ₃ )-(I ₂ + I ₄ ) = 4d _2. Therefore, FE = (I ₁ + I ₃ )-(I ₂ + I ₄ ) can be used as the focus error signal FE.

The data signal S is obtained by adding the outputs from the respective light receiving sections of the light receiving element 15 and using S = I ₁ + I ₂ + I ₃ + I ₄ .

In order to configure each detection signal as described above from the output of the light receiving element 15, a circuit as shown in FIG. 2 may be used. That is, after the outputs from the respective light receiving portions of the light receiving element 15 are amplified by the preamplifiers 151, 152, 153, and 154, they are added and subtracted by the adders 161 and 162 and the subtracters 163 and 164, and the added one is subtracted. When the subtraction process is performed by the unit 191, a focus error signal FE is obtained. When the added ones are added by an adder 193, a data signal S is obtained.

The output of the subtractor 163 is added to the sine function generator 1
A multiplier 171 multiplies the sine function sinφ generated at 81 by a sine function, and a cosine function generator 18
The multiplier 172 multiplies the cosine function cos φ generated in 2 by the multiplier 172. When the outputs of the multipliers 171 and 172 are added by the adder 192, a tracking error signal TF is obtained. The rotation angle φ is generated from an encoder (not shown) in synchronization with the rotation of the movable unit, and is output from the function generator 18.
1,182.

In the case of the above description, the focus error signal FE
Functions as an appropriate signal under the condition of d (2) >> a (2), b (2) as described above. This condition is general, but there is a case where this condition is not satisfied exceptionally. In such a case, the tracking error signal may enter the focus error signal to cause an error.

In the optical tape memory device according to the second aspect,
Such a problem is effectively avoided as follows. That is, FIG. 3 shows a signal detection system in the embodiment of the optical tape memory device of the second aspect. In order to avoid complication, the same reference numerals as those in FIG. 1 are used for those which do not seem to be confused.

Reference numeral 11A denotes a beam splitter, and reference numeral 1
Reference numeral 4A denotes a cylinder lens, and reference numeral 15A denotes a cross-shaped quadrant light receiving element. The return light converted into a converging light beam by the collimating lens 13 is transmitted to the polarization beam splitter 1.
When the light passes through 1, the beam is split into two by the beam splitter 11A, and converted into astigmatic light beams by the cylinder lenses 14 and 14A, respectively. Since the power of the cylinder lens 14 is in the direction perpendicular to the drawing and the power of the cylinder lens 14A is in the horizontal direction in the drawing, these two light beams are converted into astigmatic light beams so as to be orthogonal to each other.

The relationship between the arrangement of the light receiving portions of the light receiving elements 15 and 15A and the track reference direction (direction in which φ = 0) is as shown in FIGS. 3B and 3C. From each of the light receiving portions 15-1,15-2,15-3,15-4 of the light receiving element 15 to the output I ₁ above as I ₄ is outputted, the light-receiving light-receiving element 15A portion 15A-1 and 15A-2 , respectively from 15A-3,15A-4 output _{J 1, J 2, J 3} , J 4 is output.

At this time, if the higher-order harmonic components are ignored, the outputs I ₁ to I ₄ are as follows. That is, I ₁ = (π / 2) a ₀ + √ [2] a (1) sin (φ-π / 4) + √ [2] b (1) cos (φ-π / 4) + a (2) cos2φ + b (2) sin2φ + c (1) + c (2) + d (1) (18) I ₂ = (π / 2) a ₀ + {[2] a (1) cos (φ−π / 4) −√ [ 2] b (1) sin (φ−π / 4) −a (2) cos2φ−b (2) sin2φ + c (1) −c (2) −d (1) (19) I ₃ = (π / 2) a ₀ −√ [2] a (1) sin (φ−π / 4) −√ [2] b (1) cos (φ−π / 4) + a (2) cos2φ + b (2) sin2φ−c (1 ) + C (2) −d (1) (20) I ₄ = (π / 2) a ₀ −√ [2] a (1) cos (φ−π / 4) + √ [2] b (1) sin (φ−π / 4) −a (2) cos2φ−b (2) sin2φ−c (1) −c (2) + d (1) (21) Using these outputs, the above equation (10) is derived. was's and performed the same calculation, TE = (I ₁ as the tracking error signal - _{3) sin (φ-π /} 4) + (I 2 -I 4) cos (φ-π / 4) (22) is obtained. In deriving this equation, since the beam pattern of the photodetector is symmetric by the astigmatism method, c (n),
The first order term of d (n), that is, c (1) and d (1) can be regarded as 0.

When (I ₁ + I ₃ )-(I ₂ + I ₄ ) is formed from the output of the light receiving element 15 in response to a normal focus error signal, (I ₁ + I ₃ )- (I ₂ + I ₄ ) = 4a (2) cos 2φ + 4b (2) sin 2φ + 4c (2) (23) is obtained, and (J ₁ + J ₃ ) is obtained from the output of 15 of the light receiving element 15A in response to the normal focus error signal. )-(J ₂ + J ₄ ), (J ₁ + J ₃ )-(J ₂ + J ₄ ) = 4a (2) cos2φ + 4b (2) sin2φ-4c (2) (24) can get. That is, the output of the light receiving element 15A is such that the sign is reversed only for C (2).

Then, as the focus error signal FE,
Using (23)-(24), FE = {(I ₁ + I ₃ )-(I ₂ + I ₄ )}-{(J ₁ + J ₃ )-(J ₂ + J ₄ )} = 8c (2) (25) is obtained, and the crosstalk of the tracking error signal, which is a problem in the equation (16) in the above embodiment, is canceled and eliminated, and a focus error signal without any error can be obtained.

On the other hand, if the signal detection system of the device configuration of FIG. 1A is configured as shown in FIG. 4, the left side of the above-described equation (10), ie, “(I ₁₋ I ₃ ) sin φ + (I ₂ −I ₄ ) cos φ ”can be used.

FIG. 4 shows a signal detection system which is a main part of one embodiment of the optical tape memory device according to the first aspect. In the entire fixed system, the right side of the polarization beam splitter 11 in the configuration shown in FIG. 3A may be configured as shown in FIG. Again, to avoid complications, the same reference numerals as in FIG. 3 are used for the same equipment. Reference numeral 14C denotes a Foucault prism, and reference numeral 15B denotes a quadruple light receiving section type light receiving element. The return light is converged by a collimator lens (not shown), passes through a polarization beam splitter (not shown), and is split into two by a beam splitter 11A. It converges on the ridge P of the prism 14C.

The tracking error signal TE is composed of TE = (J ₁ −J ₃ ) sin φ + (J ₂ −J ₄ ) cos φ (26) using the outputs J ₁ to J ₄ of the light receiving element 15 A. This equation is the same as equation (10).

Next, the structure of the focus error signal will be described.

FIG. 4D shows the state of the light-converging pattern at the ridge line portion P of the Foucault prism 14C. This pattern rotation of the track, that is, rotates with the rotation of the movable part, when the light intensity distribution of the upper and lower portions of the ridge line Ia, and Ib, they _{Ia = I 1 + I 2 =} πa 0 + 2a (1) cosφ- 2b (1) sin φ (27) Ib = I ₃ + I ₄ = πa ₀ -2a (1) cos φ + 2b (1) sin φ (28)

Assuming that the outputs of the light receiving sections 15B-1, 15B-2, 15B-3, 15-4 of the quadruple light receiving section type light receiving element 15B are K ₁ to K ₄ , these outputs are as follows. .

A: When the recording surface of the optical tape is farther from the focal point K ₁ = 0, K ₂ = X · Ia, K ₃ = X · Ib, K ₄ = 0 B: The recording surface of the optical tape is in focus K ₁ = K ₂ = (１ ／) Ia, K ₃ = K ₄ = (１ ／) Ib C: When the recording surface of the optical tape is closer to the focal point K ₁ = X · Ib, K ₂ = 0, K ₃ = 0, K ₄ = X · Ia where X is a constant that changes depending on the state of the near / ridge portion P between the Foucault prism 14C and the light receiving element 15B.

Therefore, when a signal of {(K ₂ + K ₃ ) − (K ₁ + K ₄ )} is constructed from these outputs K ₁ to K ₄ , this signal depends on the conditions of A, B and C. + X (Ia + Ib), 0, −X (Ia + Ib) (29), and from the above equations (27) and (28), Ia + Ib = 2
Considering that πa ₀ , the signal ｛(K ₂ + K ₃ ) −
(K ₁ + K ₄ )｝ corresponds well to the focus error and is separated from the tracking error signal. Therefore, the signal {(K ₂ + K ₃ ) − (K ₁ + K ₄ )} can be used as a focus error signal. Signal ｛(K ₂ + K ₃ ) −
(K ₁ + K ₄ )｝ changes to 2X · πa ₀ , 0, −2X · πa _0, and there is a possibility that the modulation signal and amplitude a _{0 of} the data signal may enter and cause an error in focus control. Since the signal is a high-frequency signal and the focus error signal is a low-frequency signal, the signal Ｋ (K ₂ + K ₃ ) − (K ₁ +
If K ₄ )｝ is “passed through a low-pass filter to remove high-frequency components”, a focus error signal without error can be obtained. In this embodiment, a condensed light beam that is not converted to an astigmatic light beam is incident on the light receiving element 15A for obtaining a tracking error signal. In this manner, the focus error signal is less likely to enter the tracking error signal and a good tracking error signal can be obtained as compared with a case where the focus error signal and the tracking error signal by the astigmatism method are obtained from the same light receiving element.

In the embodiment described above, an example was described in which a mirror prism and an objective lens were used as a condensing optical system constituting a movable portion.

In the conventionally known optical disk system, the optical pickup and the optical disk are driven separately, so that the distance between the objective lens and the recording surface of the optical disk always fluctuates, and therefore focus control is indispensable. However, in the scanning method according to the present invention, in which the optical tape is fed along the peripheral surface of the tape guide, by sufficiently increasing the positional accuracy of the tape guide and the movable part, the optical system between the movable part optical system and the optical tape recording surface is moved. It is also possible to keep the distance substantially unchanged, in which case focus control can be omitted.

FIG. 5 shows an example of the configuration of the movable portion when the focus control is omitted as described above. Code 16
A indicates a condensing optical system that forms a movable part. The condensing optical system 16A has a reflecting surface formed as a paraboloid, and is arranged and rotated so that its focal point coincides with the recording surface of the optical tape 23. Such a condensing optical system can be configured by forming a reflective film on a metal such as Al by ultra-precision cutting or polishing, or by molding a glass or plastic material. The use of such a condensing optical system can improve the workability, so that the cost of the optical tape memory device can be reduced, and the speed of scanning can be increased by reducing the weight of the movable portion. In the case of this method, when the focus control is necessary, the light source (for example, a semiconductor laser) itself can be displaced in the optical axis direction by a piezoelectric element or the like.

[0067]

As described above, according to the present invention, a new optical tape memory device, a signal detecting method, and an optical tape cassette can be provided. In the optical tape memory device of the present invention, an optical system for recording and / or reproducing information is composed of a movable part and a fixed part, and only the movable part rotates for scanning the optical tape. Rotation is possible, and high-speed information processing is possible. Further, since the movable portion is constituted by a minimum optical system, deformation and alignment change due to centrifugal force are unlikely to occur. According to the signal detection method of the present invention, good signal detection is possible. Further, by making the optical tape cassette a closed type, contamination by dust during transportation or the like is effectively prevented.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining an outline of an optical tape memory device, wherein FIG. 1A is a diagram of an optical system arrangement, FIG. 1B is a diagram of a light receiving section of a light receiving element, FIG. (D) is a figure explaining an optical tape.

FIG. 2 is a diagram for explaining an example of a signal detection circuit in the example shown in FIG. 1;

FIG. 3 is a diagram showing a signal detection system in an embodiment of the optical tape memory device according to claim 2;

FIG. 4 is a diagram showing a signal detection system in the embodiment of the optical tape memory device of the first embodiment.

FIG. 5 is a view showing one embodiment of a light condensing optical system of a movable unit.

[Explanation of symbols]

 Reference Signs List 10 light source 11 polarizing beam splitter 12 quarter-wave plate 13 collimating lens 14 cylinder lens 15 light receiving element 16 mirror prism 17 objective lens 22 tape guide 23 optical tape

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyoshi Funato 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (56) References JP-A-2-246023 (JP, A) JP-A JP-A-58-139340 (JP, A) JP-A-2-223026 (JP, A) JP-A-3-1331 (JP, A) JP-A-3-40229 (JP, A) JP-A-4-21947 (JP) , A) Tomoyuki Shirata, et al., "Proposal on Signal Detection System for Optical Compact Tape and Basic Experiment", Proc. Of the IEICE Fall National Conference 1990, IEICE IEICE, Sep. 15, 2009, Supplement 4, p. 373 (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/09-7/095 G11B 7/00 G11B 23/087 G11B 25/06

Claims (4)

(57) [Claims] An optical tape set at a predetermined angle with respect to the longitudinal direction of the tape and spirally wound around an outer peripheral surface of a transparent cylindrical tape guide to feed the tape at a low speed, An apparatus for recording and / or reproducing information by light, wherein an optical system for recording and / or reproducing information by light includes a movable part and a fixed part. And / or a condensing optical system that rotates at a high speed within the tape guide for reproduction, and wherein the fixed unit emits light to be condensed on the recording surface of the optical tape by the movable unit; A signal detection system for detecting a signal based on the return light from the recording surface, wherein the signal detection system detects the return light from the recording surface of the optical tape by two.
A beam splitter for splitting, a Foucault detection system for detecting a focus error signal by the Foucault method for one light beam split by the beam splitter by a Foucault method, and a cross-quadrant light receiving element for receiving the other split light beam When the output signal from each light receiving unit of the light receiving element is I ₁ , I ₂ , I ₃ , I ₄ around a predetermined direction, and the rotation angle of the focusing optical system of the movable unit is φ, The tracking error signal TE is defined as TE = (I ₁ −I ₃ ) sin φ + (I ₂ −I ₄ ) cos φ, and the output signal from each light receiving section of the quadruple light receiving section type light receiving element in the Foucault detection system is directed in a predetermined direction. K ₁ , K ₂ , K ₃ , K ₄
An optical tape memory device characterized in that a signal of {(K ₂ + K ₃ ) − (K ₁ + K ₄ )} is passed through a low-pass filter and a high-frequency component is removed to obtain a focus error signal. 2. An optical tape having a track set at a predetermined angle with respect to the longitudinal direction of the tape is spirally wound around the outer peripheral surface of a transparent cylindrical tape guide, and the tape is fed at a low speed. An apparatus for recording and / or reproducing information by light, wherein an optical system for recording and / or reproducing information by light includes a movable part and a fixed part. And / or a condensing optical system that rotates at a high speed within the tape guide for reproduction, and wherein the fixed unit emits light to be condensed on the recording surface of the optical tape by the movable unit; A signal detection system for detecting a signal based on the return light from the recording surface, wherein the signal detection system detects the return light from the recording surface of the optical tape by two.
A beam splitter for splitting, a pair of astigmatic light beam forming optical systems for converting each of the light beams split by the beam splitter into astigmatic light beams in directions orthogonal to each other, and an astigmatic light beam by these astigmatic light beam optical systems And a pair of four-part light receiving elements for receiving each of the converted light beams. The output signals from the respective light receiving parts of one of the light receiving elements are rotated in a predetermined direction around I ₁ , I ₂ , I ₃ , Assuming that I ₄ and φ are the rotation angles of the focusing optical system of the movable part, the tracking error signal TE is calculated as TE = (I ₁ −I ₃ ) sin (φ−π / 4) + (I ₂ −I ₄ ) cos (φ−π / 4), and the output signals from the respective light receiving sections of the other light receiving element are set to J ₁ , J ₂ , J ₃ , and J ₄ around a predetermined direction, and the focus error signal FE is FE = ｛( _{I 1 + I 3) - (} I 2 + I 4)} - {(J 1 + J 3) - , characterized in that the (J ₂ + J _4)} Tape memory device. 3. A method for detecting a signal in an optical tape memory device, the method being implemented in the optical tape memory device according to claim 1. 4. An optical tape cassette wherein a transparent cylindrical tape guide is hermetically provided in an airtight container for winding and storing an optical tape.