KR830000430B1 - Reading device of optical radiation carrier - Google Patents

Abstract

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Description

Reading device of optical radiation carrier

1 is a schematic diagram of a first embodiment of a reading apparatus of the present invention.

2A and 2B are layout explanatory diagrams of the focus detector of FIG.

3a and 3b are explanatory diagrams of FIG.

4 is a schematic diagram of a second embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading apparatus of an optical radiation reflection type carrier, in particular, a radiation source for generating a read beam, and a reading beam on a read spot on the information structure of the information carrier and the output signal is An objective system for imaging the read spot on a radiation sensing information detector for displaying information, and a photoelectric focusing error detection device for determining a deviation between a desired position and an actual position of the focal plane of the objective system; The focusing error detecting apparatus has two radiation detecting focusing detectors which cope with one fine focusing beam, and makes an optical radiation reflection information carrier for instructing the deviation by the difference of the output signals of these two focusing detectors. It relates to a reading device of.

In addition, the term "focusing beam" used in the present specification means an auxiliary beam used to detect a focusing error of the reading beam.

Known reading devices, such as our prior art, have been used to read information carriers that accumulate, for example, (color) television programs. In this case, the information structure is composed of a plurality of main and intermediate regions arranged alternately according to the spiral track, and the main and intermediate regions have different influences on the read beam, in which case the information is the length of the main region and the length of the intermediate region. It is embedded in the information carrier in the form of. In order to obtain a sufficiently long reproduction time, the fine portion of the information structure is extremely small for the limited dimensions of the information carrier. For example, on one side of a disk-shaped information carrier with a 30-minute television program, the track width is about 0.5 µm and the average length of the main and intermediate areas is accumulated in an annular area of about 15 cm in outer diameter and about 6 cm in inner diameter. About 1 μm.

In order to be able to read such minute details, an objective system having a very large numerical aperture must be used. However, the depth of focus of such an object system is small, and there is a fear that the distance between the plane of the information structure and the object system is larger than the depth of focus in the reading device, and the countermeasure that can detect such a change and correct the focusing. It is necessary to find out.

Therefore, in the prior invention of the present inventors, the beam is divided into the thin beam from the steep beam before entering the objective system, and the thin beam passes through the objective system in an oblique direction, is reflected by the information carrier, and then proceeds to the objective system again. In this case, a radiation spot, that is, a focusing spot, is formed on the plane of the two focusing detectors. In this case, the degree of focusing of the read beam on the information structure is indicated by the symmetry of the focusing spots of the two focusing detectors.

Such conventional reading apparatus requires a large number of additional elements such as a semi-transparent mirror, a complete reflector for forming a focusing beam, and an additional lens for focusing the sub-beam on the focal plane of the objective system. The drawback was that the placement position was extremely small.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide a reading device which minimizes the number of additional elements required for focus detection. The reading device of the present invention has a reading beam path on one side of an optical axis of an object system. And a radiation deflecting element in the chamber, so that the surface area of the radiation deflecting element is made smaller than the cross-sectional area of the read beam.

Due to the radiation deflection element, a read beam and a part of the read beam are directed in a different direction from the remaining read beam, are focused on the two focus detectors through an object system, and are focused on the radiation spot focused detectors formed on the planes of these focus detectors. The location of the data center depends on the degree of concentration of the reading beam on the information surface of the information carrier.

The information detector and the focus detector are arranged on the same plane perpendicular to the optical axis, and the radiation deflection element may be composed of an optical wedge or a diffraction grating.

According to a first embodiment of the present invention, the radiation deflecting element is appropriately arranged in a passage of a reading beam directed to the information carrier so that additional radiation spots other than the read spot on the information construct are caused by radiation incident on the radiation deflecting element. Is configured to form an image on the two focused detectors via an object system.

As the radiation source, a gas laser such as a helium-neon laser can be used. In that case, the distance between the object system and the plane of the focusing detector is relatively large, and the focusing spot is arranged at a point relatively far from the read spot.

On the other hand, semiconductor diode lasers may be used as radiation, and such lasers are also used as information detectors. In that case, the radiation emitted by the information carrier does not need to be separated from the radiation directed to the information carrier. Therefore, the structure of the optical information unit can be kept simple and small, and an objective system with a small magnification can be used. In such a reading apparatus, when the focusing beam is formed by the deflection element, the focusing spot may be arranged near the reading spot so that the focusing detector is not arranged within the required distance with respect to the diode laser. Even when the focus detector is arranged at the required position, if there is a small focus error of the read beam, a part of the read beam has already entered the focus detector, and an error occurs in the focus control signal.

In order to eliminate these problems, the first embodiment of the present invention furthermore uses the radiation deflecting element as the first optical wedge, and the second beam is formed in the second beam path formed by the first optical wedge and reflected by the information carrier. Characterized in that configured to install the optical wedge.

The second optical wedge is preferably installed in the first optical wedge formed through the lens carrier closest to the information carrier and the object carrier in the object system, and it is determined whether the area of the second optical wedge is equal to the area of the first optical wedge or It is smaller than this.

The objective system can include a plurality of lens elements or a single lens element, and in the latter case, the lens element closest to the information carrier of the objective system becomes the objective system itself.

The second optical wedge, which preferably has a diffraction angle larger than that of the first optical wedge, reads the focusing beam reflected by the information carrier and additionally deflects the beam, thereby increasing the distance between the focusing spot and the reading spot.

In order to keep the second optical wedge in the image of the first optical wedge irrespective of the position of the information carrier with respect to the objective system, the reading apparatus of the present invention is again applied to the information carrier of the objective system. It is characterized in that it is provided on the rear focusing surface of the near lens element.

According to a second embodiment of the reading apparatus of the present invention, the radiation deflecting elements are suitably disposed in a passage of a reading beam that is emitted by an information carrier and originates from a reading spot, and thus the two radiation detectors emit radiation incident on the radiation deflecting elements. It is characterized in that it is configured to deflect.

Furthermore, the reading apparatus of the present invention is characterized in that the straight line separating the two focusing detectors is configured to have an acute angle with respect to the direction in which the radiation spot formed on the plane of the two focusing detectors moves due to the focusing error. . In this way, complicated conditions for the installation position of the focus detector are eliminated.

의 각도를 이루도록 구성함으로 일층 저감할 수가 있다.The radiation deflection element used is very small compared to the read beam, so that the actual reading of information along the dimensions of the read beam is not affected. The slight effect on the reading of the radiation deflecting element is about 45 to the direction in which the information track of the information carrier is read by a straight line connecting the optical axis of the objective system and the radiation deflection element.

By configuring to achieve the angle of can be further reduced.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 shows a first embodiment of the present invention, in which the disk-shaped information carrier 1 displays a radial section of a part thereof and the information structure is a phase structure, for example, a plurality of concentric or quasi-concentric information tracks. (2), and these tracks comprise a series of main regions and intermediate regions. The main area can be arranged at a different level than, for example, the intermediate area in the information carrier. The information may be, for example, a color television program, but instead may be other information, such as multiple images or digital information. It is preferable that the information structure is provided on the rear side of the information carrier 1.

The information carrier 1 is irradiated by a reciprocating read beam 3 generated by a diode laser and is composed of a single lens or two lenses L ₁ and L ₂ as shown in FIG. The reading beam 3 is focused on the reading spot Vi on the information structure by the object system. In this case, the read beam 3 is reflected by the information structure, and as the information carrier 1 rotates, the read beam 3 is modulated by the information contained in the track portion to be read. After reflection, the read beam 3 traverses the object system to form an image Vi of the read spot Vi. At the position of the radiation spot Vi ', an information detector for converting the modulated beam into an electrical signal Si is arranged.

When the radiation source is a diode laser, this diode laser can be used as an information detector as described in West German Patent Application No. 2,244,119. In response to the intensity of the reflected reading beam, the resistance varies between the electrical resistance between the two ends of the diode laser or the intensity of the radiation emitted from the rear of the diode laser. When a diode laser is used as the radiation source, there is no need for a non-division element that separates the double wave modulated read beam reflected by the information carrier 1 and the unmodulated read beam which returns to the information carrier 1.

In the present invention, a small optical wedge 5 is arranged in the passage of the reading beam 3. The optical wedge 5 divides the read beam 3 to the sub-beam 6 (indicated by broken lines in FIG. 1). This sub-beam 6 is focused on the radiation spot Vf on the information structure by the lens L ₁ . The focusing beam is reflected by the information structure, and after traveling through the object system, a radiation spot Vf '(focusing spot) is formed on a focusing detection device composed of two focusing detectors 7 and 8. When the distance between the plane of the track 2 and the outside of the object system is appropriate, the focus spot Vf 'is symmetrical with respect to the focus detectors 7 and 8, so that both the focus detectors 7 and 8 have the same amount. Receives radiation and its output signals S ₇ (S ₈ ) are the same.

When the plane of the information structure moves downward with respect to the objective system, the position where the reflected beam 6 enters the lens L ₁ is shifted toward the optical axis 00 ', and in this case, the beam 6 by the objective system Deflection is slight and the focus spot Vf 'moves to the left. Therefore, the light receiving amount of the focusing detector 7 becomes larger than the light receiving amount of the focusing detector 8.

When the plane of the track 2 moves upward with respect to the objective system, a reverse phenomenon occurs and the light receiving amount of the focusing detector 7 becomes smaller than the light receiving amount of the focusing detector 8.

The output signals S ₇ (S ₈ ) of the focus detectors 7 and 8 are supplied to the electronic circuit 9. In the electronic circuit 9, these two signals are subtracted by a known method. The focusing control signal rf is generated at the output terminal of the electronic circuit 9, and the focusing of the objective system can be corrected by moving the objective system along the optical axis 00 'according to the focusing control signal. . Even when the radiation source is a diode laser, the optical reading unit can move along the optical axis.

The optical wedge or diffraction grating 5 is installed in the passage of the double reading beam facing the information carrier ₁ , and the focusing beam passing through the lens L ₁ is thin. Therefore, the focus spot Vf becomes considerably larger than the read spot Vi. In that case, the details of the information structure cannot be identified by the focusing beam, so the signal S ₇ (S ₈ ) does not show any high frequency fluctuations.

For simplicity of illustration, the focusing beam reflected in FIG. 1 is shown as passing through the boundary of the lens L ₁ . In practice, the beam is incident on the lens L ₁ closer to the optical axis.

In the reading apparatus of the present invention, the focusing beam is formed by an extremely simple means, namely, an optical wedge or a fine diffraction grating. Optical wedges or diffraction gratings can be installed, for example, on transparent plates. This transparent plate can be fixed to the lens L ₁ in the direction of the optical axis 00 '.

The diffraction angle of the optical wedge 5 is taken as its upper limit, and thus the deflection of the focusing beam by the optical wedge 5 is also taken as an upper limit. The location where the focus is adjusted in the information structure is preferably closest to the point where the reading is performed in the information structure. The distance between the read spot Vi and the focus spot Vf is, for example, 100 µm. The correct focusing of the read beam 3 can be maintained even when the information carrier 1 is inclined with respect to the optical axis 00 'or when the thickness of the information carrier 1 is uneven.

In order to have a sufficient distance between the focus spot Vf 'and the read spot Vi', either the magnification of the objective system is large or the radiation source does not simultaneously form an information detector and thus the information carrier 1 If the reflected radiation can be deflected in a mirror image relationship and the focusing detector can be arranged at an appropriate position from the information carrier 1, deflection by the optical wedge 5 is sufficient.

In the case of using a diode laser as a radiation source (see FIG. 1) and using an objective system in which a diode laser is formed on an information structure at a ratio of 2: 1, the distance between the objective system and the diode laser is reduced so that the optical film wedge ( As a result of the deflection by 5), it is suitable to make the distance between the read spot Vi 'and the focus spot Vf' extremely small. In this case, in the present invention, the second optical wedge 10 can be used. The optical wedge 10 is arranged as a barrel of the reflected focusing beam, and the optical wedge 10 has no influence on the distance between the spot Vi and the spot Vf, so the optical wedge 10 is optical. It can be made to have a larger relief angle than the wedge (5).

In addition, when the optical wedge 5 can obtain a sufficient distance between the spot Vi 'and the spot Vf', the second optical wedge 10 can be used. When the read spot Vi 'is extended because the information structure is out of focus, the radiation of the read beam 3 can be prevented from entering the focus detector by the second optical wedge 10.

The optical wedge 10 needs to be disposed in the window of the optical wedge 5, that is, the optical wedges 5 and 10 are imaged on different optical wedges by the lens L ₁ via the information carrier 1. It is necessary to do it. In FIG. 1, the peripheral light ray of the said phase image is shown by the constant chain line.

In the case where the plane of the optical wedges 5 and 10 is provided at a location of an arbitrary height between the lenses L ₁ and L ₂ , the image of the optical member 5 is the distance between the plane of the information structure and the objective system. Depends on. Therefore, care is taken in the present invention so that the planes of the optical wedges 5 and 10 coincide with the focal plane of the lens L1.

The second optical wedge needs to be slightly larger than the first optical wedge so that all radiation reflected by the first optical wedge 5 passes through the second optical wedge 10. However, a small portion of the reading beam 3 passes through the second optical wedge 10 to generate a separate radiation spot Vn on the surfaces of the focus detectors 7 and 8 (in a straight line in FIG. 1). Refer to the possible sizes (3 ')). In the state of FIG. 1, the read beam 3 is correctly focused on the information structure, and the radiation spot Vn is arranged near the focus detectors 7 and 8. As shown in FIG. When the plane of the track 2 is moved upward, if there is a small focusing error, the radiation spot Vn enters the focusing detector 7 and an error signal rf is generated to use this signal as the focusing control signal.

Therefore, the area of the optical wedge 10 needs to be such that its maximum value is equal to the area of the optical wedge 5, and the optical wedge 10 is disposed in the window of the optical wedge 5. As a result, part of the focusing beam, i.e., the beam 6 'indicated by the broken line, does not enter the detectors 7 and 8. However, this only causes the output signals S ₇ and S ₈ of both detectors to be slightly smaller, and the sensitivity of the detection device to the focusing error is not so affected.

Also the distance (d) between the portion with which the optical axis (00 ') and the converging beam incident upon the lens (L ₁₎ It is noted that about 0.7 times the radius of that study of the lens (L _1). In the reading method of FIG. 1 which crosses the information carrier of the reading beam 3 twice, when the thickness of the information carrier 1 is not equal, the influence on the shape of the spot Vi of the spherical aberration in the objective system is focused. The control method is minimum.

2A and 2B, two focusing detectors 7 and 8 are shown as a focusing spot Vf 'incident thereon. It is assumed that the focus spot Vf 'moves in the x direction in accordance with the change in the direct speed of the reading beam 3. In order to optimize the sensitivity to the focusing error of the detection apparatus, it is necessary to make the straight line g separating the detectors 7 and 8 perpendicular to the x direction as shown in FIG. 2A. However, in this case, the derived focusing control signal rf remarkably depends on the position in the directions of the focusing detectors 7 and 8.

를 이루도록 한다. 이 경우 집속제어신호(rf)의 영치통과 또는 영치교차는 광축(00')의 주위에서 광학웨지(5) 또는 광학웨지(5) 및 (10)을 회전하는 것에 의하여 조정할 수가 있다. 제3a도 및 제3b도에는 광학웨지(5) 및 (10)을 회전한 경우 집속스포트(Vf')에 의하여 그려지는 통로를 파선극선(C)로 표시한다. 검출기(7) 및 (8)이 제2b도의 방향을 가진 제3a도의 경우에 있어서는 검출기(7) 및 (8)에 있어서의 방사선 분포는 집속스포트(Vf')가 곡선(C)에 따라 검출기(7) 및 (8)상을 이동할때에 변화한다. 독취장치의 조립에 있어서 광학웨지(5) 및 (10)과 같이 투명판을 렌즈(L₁) 및 (L₂)의 사이에 배설하여 집속을 적정집속으로 조정한 후 투명판을 회전하여 집속스포트(Vf')가 검출기(7) 및 (8)에 대하여 대칭이 되게 한다. 이것은 검출기(7) 및 (8)이 제2a도에 표시한 방향을 가지는 경우에는 불가능하다. 그 경우에는 광학웨지용 투명판을 작은 각도만큼 회전하는 것에 의하여 검출기(7) 및 (8)상의 방사선 분포에 영향을 끼치도록 할 수는 없다(제3b도 참조).In the present invention, the focusing detectors 7 and 8 are appropriately arranged so that the separating line g forms an acute angle with respect to the x direction, for example, as shown in FIG. 2B. For 45

To achieve. In this case, the zero pass or zero crossing of the focusing control signal rf can be adjusted by rotating the optical wedge 5 or the optical wedges 5 and 10 around the optical axis 00 '. 3A and 3B, the passage drawn by the focusing spot Vf 'when the optical wedges 5 and 10 are rotated is indicated by the broken line C. As shown in FIG. In the case of FIG. 3A in which the detectors 7 and 8 have the direction of FIG. 2B, the radiation distribution in the detectors 7 and 8 is determined by the focus spot Vf 'according to the curve C. 7) and (8) changes when moving. In assembling the reading device, like the optical wedges 5 and 10, a transparent plate is disposed between the lenses L ₁ and L ₂ , the focus is adjusted to the proper focus, and the transparent plate is rotated to focus the spot. Let Vf 'be symmetrical with respect to detectors 7 and 8. This is impossible if the detectors 7 and 8 have the directions shown in Fig. 2A. In that case, it is not possible to influence the radiation distribution on the detectors 7 and 8 by rotating the transparent plate for optical wedge by a small angle (see also 3b).

When the focusing detectors 7 and 8 have the direction of FIG. 2b, the detector 7 caused by the movement of the focusing spot Vf 'in the x direction, that is, the movement of the spot Vf' resulting from the focusing error The change in the output signals S ₇ and S _{8 in} ( ₈ ) is smaller than in the case where these two detectors have the direction of FIG. 2A. Therefore, the sensitivity of the detection device is reduced. But this is not a problem. In the case of the configuration of FIG. 2B, the sensitivity of the detection apparatus is also appropriately maintained. In that case, the evaluation of the advantages obtained with respect to the tolerances of the positions of the detectors 7 and 8 is very important as compared with the reduction of the sensitivity.

의 각도로 설정함으로 일층 저감할 수가 있다.Since the focus beam is derived from the read beam 3, the read beam 3 does not fill the pupil part of the lens L _{1 with the} optimal aspect. Therefore, the radiation spot Vi becomes slightly larger in the direction of the straight line between the optical axis 00 'and the solid of the deflection element (the wedge portion or the diffraction grating). In that case, the decomposition function of the reading beam 3 in this direction becomes slightly smaller. The effect of its own mirror image is about 45 relative to the direction of the track portion that should read the optical axis (00 ') and the straight line through the deflection element.

The angle can be reduced even further.

The two radiation deflecting elements 5 and 10 necessary for setting the distance between the radiation spots Vi 'and Vf' to an appropriate value need to be aligned correctly with each other. In addition, both devices 5 and 10 need to be properly aligned with respect to the object system. This is because the element 10 must be disposed in the window of the element 5.

4 shows a second embodiment of the present invention, in which the focus spot Vf 'and the reshaped image read spot Vi' are formed by only one radiation deflecting element in which the conditions for the installation position are not so problematic. Make sure the distance between is the appropriate value. In FIG. 4, the same elements as those of FIG. 1 are denoted by the same symbols.

In the configuration of FIG. 4, the small optical wedge member 10 is appropriately arranged and arranged so that the sub beam or focus beam 6 is leveled from the read beam reflected by the information carrier 1. The breakage of FIG. 4 indicates which portion of the reading beam 3 passes through the wedge member 10.

The focusing beam 6 is focused onto the radiation spot or focusing spot Vf 'on the focusing detectors 7 and 8 by means of lenses L ₁ and L ₂ .

In this example, only one radiation spot on the information structure is used to read information and generate a focus error signal. In that case, the area in which the reading beam is concentrated in the information structure is always the area under reading.

The wedge member 10 also faces a portion of the reading beam 3 facing the information structure 1. However, this beam portion is focused on an additional radiation spot on the right side of the read spot Vi 'on the information construct. By means of the objective lens systems L ₁ and L ₂ , the additional radiation spot is imaged again at the position on the left side of the optical axis 00 ', that is, not on the focusing detectors 7 and 8.

When the optical element to be used is appropriately arranged and the distance between the plane of the information track 2 and the objectives L ₁ and L ₂ is proper, radiation incident on the optical wedge member 10 is removed. Proceed in the direction indicated by dashed lines at 4 degrees. In this case, the focusing beam 6 is flattened by the wedge member 10 so that the focusing spot Vf 'is symmetrical with respect to the detectors 7 and 8. As shown in FIG. Therefore, the detectors 7 and 8 receive the same amount of radiation, and the output signals S ₇ and S _{8 of} the detectors 7 and ₈ are the same.

When the plane of the information structure moves relative to the object system L ₁ , L ₂ , the convergence of the read beam 3 reflected by the information carrier 1 changes. As a result, the portion used as the focusing beam 6 in the read beam 3 is incident on the optical wedge 10 at an angle different from that shown in FIG. As a result, the position of the focusing spot Vf 'with respect to the detectors 7 and 8 also changes depending on the direction in which the beam 6 passes through the optical wedge 10. When the plane of the information structure moves toward the objectives L ₁ and L ₂ , the amount of radiation received by the detector 7 is greater than that of the detector 8. However, when the plane of the information structure moves in the direction away from the objectives L ₁ and L ₂ , the radiation received amount of the detector 7 is greater than the radiation received amount of the detector 8.

The additional means described above with respect to FIG. 1 also applies to the configuration of FIG.

The distance a between the center of the optical wedge 10 and the optical axis 00 'is preferably about 0.7 times the radius of the read beam 3 at the position of the optical wedge 10. When the thicknesses of the information carriers 1 are not the same, the influence on the shape of the spot Vi 'of spherical aberration in the object systems L ₁ and L ₂ becomes small again.

와 같은 예각을 이루도록 한다.In addition, the straight lines separating the focusing detectors 7 and 8 are 45 with respect to the direction in which the radiation spot formed in the plane of these focusing detectors moves in accordance with the change in the position of the plane of the information structure.

Make an acute angle such as

의 각도를 이루도록 하면 바람직하다.The straight line connecting the optical wedge 10 and the optical axis (00 ') is about 45 relative to the direction of the portion to be read of the track (2).

It is preferable to achieve the angle of.

As described above, the present invention has been described based on an optical wedge as a radiation deflecting element, but this does not mean that the present invention is limited to the use of such an optical wedge. That is, instead of the optical wedge, any other radiation deflection element such as a diffraction grating may be used.

회전할 수가 있다.Further, means for leveling the focusing beam 6 in a direction opposite to that shown in the drawing may be provided so that the focusing detectors 7 and 8 can be provided on the same side as the biasing element 10 with respect to the optical axis 00 '. For this purpose the optical element 10 is for example 180 around the axis of the optical element.

Can rotate

Claims (1)

In reading information from the optical radiation reflection type information carrier, the radiation source and the reading ratio generating the reading beam are focused on the reading spot on the information carrier and the information structure, and the output signal is displayed on the radiation sensing information detector displaying the information. An objective system for imaging a read spot, and a photoelectric focusing error detection device for determining a flatness between a desired position of the focal plane of the objective system and an actual position, and the focusing error detection device comprises one fine focusing device. A reading device of an optical radiation reflection type information carrier having an optical radiation reflection type information carrier having two beam-detecting focusing detectors which respond to a beam and causing an indication of said level difference by a difference of output signals of these two focusing detectors. A radial deflecting element is provided in the passage of the reading beam on one side to reduce the surface area of the radiation deflecting element. Optical radiation reflected type information reading device of the carrier, characterized in that is configured to be very small cross-sectional area than the beam takes.

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