TW455859B - Device to eliminate DC offset of tracking error signal for optical read/write pickup heads - Google Patents

Abstract

A device to eliminate DC offset of for optical read/write pickup heads is disclosed. The device uses a holographic optical element (HOE) to separate the return beam reflected from optical disc directly to 0 order diffraction beam, which generates focus error signal, and +1 and -1 order diffraction beams, which generate tracking error signal, in a single return beam path. The 0 order diffraction beam is focused on a quadrant photodetector and converted to a first electrical signal. The +1 and -1 order diffraction beams are focused on a first tracking sensor array and a second first tracking sensor array and converted to a second and a third electrical signal. Processing the first electrical signal in a focus error signal generating circuit and the second and third electrical signal in a tracking error signal generating circuit produces focus error signal and tracking error signal respectively. By using this technique, spot asymmetry due to aberration of return beam can be corrected.

Description

455859 V. Description of the invention α) '[Field of the invention] The present invention relates to a device used in an optical pickup head to eliminate the DC deviation of the command signal, especially a readable and writable DVD (Digital Versatile Disk ) Optical read-write head or CD optical read-write head, can use Η Ο E order 0 and + 1 in the same return optical path,-order 1 light to generate astigmatic focus signal and follow-up signal (such as using a drag-and-drop method) Or DPD and other tracking method generator) devices, ΗΟΕ of +1, -1 order light is used to correct the asymmetry of the shape of the light spot caused by the aberration of the return light, and the DC deviation of the tracking signal can be eliminated. [Related technology of the invention] The technology of generating a focus error signal (FES) and a tracking error signal (TES) on an optical pickup (such as an optical pickup of a DVD-RAM) is well known. The methods for generating a focus signal include: a knife edge method (K η ife Edge) (as disclosed in U.S. Patent No. 4,701,604), an astigmatism method (such as U.S. Patent No. 5) , Disclosed in No. 850, 081), and spot size detection and measurement method (S ρ 〇 t S ize Detecti ο η); The methods used to generate tracking signals are roughly: push-pull law enforcement (Push-pu 1 1 Tracking method (such as US Patent No. 5,856,961), and DPD (Differential Phase Detection) tracking method. In the optical pickup head, through the method of generating the tracking signal (such as any of the drag-type tracking method or the DPD tracking method), and different focusing methods (such as the knife edge method, astigmatism method, or Any one of the spot size detection methods) is used to control the optical pickup when reading and writing optical disc data.

455859 V. Description of the invention (2). + Tracking and servo signal for controlling the focus of the objective lens. An optical system (shown in FIG. 1) that generates a tracking signal and a focusing signal in a DV D optical pickup is known, in which a plate glass is used to provide the astigmatism method required to generate the focusing signal. The light return point, in conjunction with the DPD law enforcement method, generates a tracking signal, but in the traditional optical read-write system, the DPD tracking method or Push-P u 1 1 tracking method is used to generate the tracking signal, as shown in Figure 1 The optical system shown below has the following problems: 1. Astigmatism (Astigmatis in) and coma (Coma) occur due to the returning light passing through the inclined flat glass, making the spot shape bad. 2. The light spot (S p o t) is too small, so the position change of the light sensor is quite sensitive, resulting in the phenomenon of DC offset of the tracking signal (DC C f f s e t). 3. In addition, a quadrant photodetector is used to process both the focus signal and the follow-up signal at the same time. The DC balance of the signal cannot be taken into consideration at the same time. [Objective and Summary of the Invention] The main object of the present invention is to provide a device for eliminating the DC offset of the tracking signal applied in an optical pickup head, in particular to a digitally readable DVD (Digital Versatile Disk) optical reader The write head or CD optical read / write head can use the 0th order of H 0 E and + 1 in the same optical path, and the-1st order light can generate astigmatic focus signals and tracking signals (such as the use of drag or DPD). The generator of the compliance method), H0E tenth, 1st order light is used to correct the asymmetry of the spot shape caused by the aberration of the return light. Another object of the present invention is to provide an astigmatism method

Page 5 455859 Explanation of the Five 'Inventions (3) · Focus signal, and a device for generating a tracking signal using the DP tracking method and the dragging tracking method. The present invention uses a holographic optical element (E Ο E) to separately generate signals required for focusing and tracking in an optical path. The astigmatic focusing method and the dragging tracking method can be used at the same time, and simultaneous use of the tracking method can be avoided. In these two methods, the signal DC balance cannot be taken into account, and the asymmetry of the shape of the light spot caused by the aberration of the return light can be corrected, that is, the DC deviation can be eliminated; in addition, the DPD follow-up signal can be obtained at the same time. According to the technology disclosed by the present invention, a Holographic optical element (HOE; Holographic optical element) is used to directly separate all the returning beams reflected from the optical disc in a single returning optical path, which are used to generate the 0th order of the focusing signal, respectively. Diffraction beams, and 11th-order diffracted light east and -1th-order diffracted beams used to generate a directional signal. The 0th-order diffracted beam is focused on a quadrant photodetector (quadrant photodetector) and converted into The first telecommunication signal, the + 1st order diffraction beam and the-丨 order diffraction beam are focused on a first tracking sensor array and a second tracking sensor array, which are converted into a second telecommunication signal and a first Three electrical signals, the first electrical signal is processed into a focused signal through a focusing signal generating circuit, and the second and third electrical signals are processed into a sequential signal through a sequential signal generating circuit, which are used to control the optical read-write head for focusing and cycling. Track movement. The aforementioned first tracking sensor array and a second tracking sensor array include the first to fourth sensing blocks, and provide a telecommunication signal required by the loop signal generating circuit. The tracking signal generating circuit generates a tracking error signal (TES) based on the signal.

455859 V. Description of the invention (4) The device causes the drive to be driven by the electric motor to the SET. ^ This will be followed by a track and then the reading light movement diagram indicates the head of the unified light. Xuan Tongzhuan is the Ming Dynasty saying 'Shi Tu Tu' —_ ί Di Yi shows the head of the Confucianism. Take the picture and read the block diagram of the Fangguang system type photo of the Mingming Mingfa. This book is a system diagram. Figure 2 3 The first figure ijl ΓΕ 4 4 5 In the whole light of the sensor, the sensor is in the full light. Ί * > Ην Shi Shishi. |-° -1 1-I The first display is shown in FIG. 4 and the full. Photographs showing the shape and emotions of the group of photogrammers for modeling photometry in the group of models; focus on light is 4 pieces. The element is the photogram of the department of science. ΛT, £ 6 6 7 8 Shi Shishi's Lfn-I.Ifml's 2nd and 2nd piece cylinder element modeler's optical imaging sense full light display display diagram and image full. Illustrate the shape, show the photogrammetry of the modeler ’s photometry in B focus 6 and return the 6th element to the head of the Department of Optical Studies of the Department of Optical Sciences. hair. This picture shows the phylogeny of Confucianism, which is the meaning of the system, and the sale of ten degrees. The morphology of the pedagogy is all the system diagram B 9 IA 9 The first construction TJ Μ Ming Ming Shi Shoushi, the head of the light, reading and learning, the light type is transmitted as a series of discs, and the light is stored with a beam of light. • The product is included with a package, 10 of which are tools, and the image is produced by intentional shooting; Department of Science

455859 V. Description of the invention (5) A beam splitter (BS) 14 for separating the laser beam from the reflected light from the optical disc 13; a collimator lens 11 for Parallel processing of laser beams into parallel beams;-Objective Lens 12 for focusing the parallel beams onto the data storage surface of the optical disc 1 3 as an access light spot; and a light sensor module 3 0 , Used to convert the reflected light beam from the optical disc 1 3 into an electrical signal. The laser light source is emitted from a laser generator 10 (usually a laser diode (LD)), converted into a parallel beam by a collimating lens 11, and focused on an optical disc 1 2 by an objective lens 12 The data storage surface 130 forms a light spot for reading / writing data, and the returning beam is reflected from the data storage surface 130 of the optical disc 13 and passes through the objective lens 12 and the collimating lens 11 in sequence, and then to the light sensing. The module 3 0 completes the data reading operation of the optical disc 13. Please refer to "Fig. 2", which is a block diagram of the system of the present invention, in which a holographic optical element 20 is added between the dichroic prism 14 and the light sensor module 30, which is configured for optical reading The single return light path of the pickup head is used to diffract all the returning light beams reflected from the data storage surface 1 30 of the optical disc 13 to a focus quadrant type optical detector 31 and a first tracking sense. After the sensor array 32 and a light sensor module 30 of the second non-compliant sensor array 33, the return beam is directly separated after passing through the holographic optical element 20 and used to generate a focus signal, respectively. Order 0 diffracted beam 4 0 and + 1 order diffracted beam 4 1 and -1 order diffracted beam 4 2 for generating a tracking signal, of which order 0 diffracted beam 4 0 is focused on a focus quadrant type optical inspection出 器 3 1 is converted into first

4 5 5 8 5 9 V. Description of the invention (6) A telecommunication signal, +1 order diffraction beam 4 1 and -1 order diffraction beam 4 2 are focused on the first tracking sensor array 3 2 and the first The non-volatile sensor array 3 3 is converted into a second electric signal and a third electric signal. The first electric signal is processed into a focus signal (FES, Focus error signal) through a focus signal generating circuit 34. The electric signal is processed into a tracking error signal (TES) by a tracking signal generating circuit 35. The FES will be provided to a voice coil driver circuit 36 (Voice Coil Driver) to drive a voice coil 3 6 1 (V ο 1 ce C ◦ i 1) while moving the objective lens 12 in the direction of the optical head of the optical pickup head for focusing; and TES is provided to a driving circuit 37 for driving a linear actuator 3 7 1 (L inear

Actuator) moving the optical pickup head to perform the tracking movement in the radial movement of the optical disc 13, as shown in the dotted line in the figure is the tracking movement part. What is shown in "Figure 3" is an example of a laser generator 10, a holographic optical element 20, and a light sensor module 3 a packaged together and applied to a holographic optical pickup However, the optical path between the laser generator 10 and the objective lens 丨 2 can of course be configured with other optical elements (such as beam shaper, beam splitter, mirror (Mirror), 1/4) Wavelength plate (1/4 wavelength plate, etc., not shown), but applied to different types of optical read heads (such as traditional optical read heads or multi-light source optical read heads); The "picture" shows an example applied to a conventional optical pickup, in which a beam splitter 稜鏡 1 4 arranged on the optical path of the optical pickup is used to reflect and reflect the laser beam from the laser generator 10 The returning beam is separated from the data storage surface 130 of the optical disc 13, and the returning beam is still by a holographic optical element arranged in the same returning optical path

455859 V. Description of the invention (7) 2 0 is diffracted to the light sensor module 30 a to provide the return light required for generating T E S and FES respectively. By using such a means of holographic optical element 2 0 and light sensor module 3 0 a arranged in the same returning optical path, the complexity of the optical pickup head can be reduced, and Η Ο E can be used to correct the return The asymmetry of the shape of the light spot caused by the aberration of light eliminates the DC deviation; the matching of the aforementioned holographic optical element 20 and the light sensor module 3 0 a can be passed through the following several preferred embodiments To achieve the purpose of the invention. [Embodiment 1] As shown in "Figures 4A to 4B", the holographic optical element 20 and the return-beam push-pull pattern and the structure of the light sensor module 30 in the first embodiment are shown. Figure. In this embodiment, the returning beam has a first diffraction region i located at the center of the optical path, and a second diffraction region ii and a third diffraction region distributed on both sides of the first diffraction region i. 1 1 1, holographic optical element 20 divides the returning beam into a 0th order diffraction beam 40, a first to third diffraction beam + 1 order diffraction beam 41, and a first to third diffraction beam -1 order diffracted beam 4 2 of the diffracted beam; 0 order diffracted light east 4 0 is used to provide the return light required to generate a focusing signal using the astigmatism method; + 1 order diffracted beam 4 1 and -1 order diffracted beams 4 2 is used to provide the feedback needed to generate a directional signal using the drag-and-drop method. The focus quadrant type photodetector 31 includes first to fourth sensing blocks V, VI, VII, and VIII adjacent to each other, where the two regions V, VIII and the two regions VI, VII are divided by lines (TD ), While blocks V and VI and blocks V II and VIII are separated by a dividing line (RD). The first tracking sensor array 32 includes two first and

Page 10 45585 9 V. Description of the invention (8) The second sensing blocks I and II are separated by a dividing line (TD); the second tracking sensor array 33 includes two adjacent sensor blocks. The first and second sensing blocks 1 II and IV are separated by a dividing line (TD). As shown in "Figure 5", it is an optical structure diagram of "Figure 4A" and "Figure 4B", showing the situation where the holographic optical element 20 focuses the return light on the light sensor module 30. Through the 0th-order diffracted beam 4 0 of the holographic optical element 20, the light spot SP is formed by focusing on the aforementioned V, VI, V II, and V Π I blocks, and the four blocks V, VI, VII, and VIII Corresponding first electric signals (generally voltage signals) will be generated according to the energy of the received light points, and this first electric signal will be provided to a focused signal generating circuit 3 4 by (V + VII)- The formula of (VI + VIII) is calculated to obtain the astigmatism focus signal (Astigmatism FES, AFES). In addition, the diffracted light of the first order + 1 through the holographic optical element 2 0 is focused to the corresponding I and II. A light spot SP 1 is formed by the light sensing block; the -1 order diffracted light beam 4 2 of the holographic optical element 20 is focused to the two light sensing blocks corresponding to II and IV to form a light spot SP 2. The four light sensing blocks I, II, III, and IV also generate corresponding second and third electrical signals (voltage signals). A second and a third telecommunication signal are provided for a tracking signal generating circuit 3 5 to obtain a drag-type tracking signal (Push-Pull TES, by formula (I-11) + (111-IV). PPTES) = [Embodiment 2] In the second preferred embodiment (as shown in the "Figures 6A ~ 6B"), the holographic optical element 20 and the return-beam push-pull pattern and light thereon are displayed. The structure diagram of the sensor module 30, the light sensor module 30 and the

Page 11 455859 V. Description of the invention (9) 4 A ~ 4 B "The first embodiment is the same, the return beam has a first diffraction zone i and a second diffraction zone 1 located on both sides of the center of the optical path. i, a third diffraction region iii and a fifth diffraction region v distributed on both sides of the first diffraction region 1, and a fourth diffraction region iv and a distributed on both sides of the second diffraction region ii The sixth diffraction region v 1, and the third diffraction region i 1 i is adjacent to the fourth diffraction region 1 v, and the fifth diffraction region v is adjacent to the sixth diffraction region vi, and two regions i and ii and iii The two zones, iv, and v, vi are separated by a radial dividing line (RD) parallel to the radial direction of the optical disc. The holographic optical element 20 is used to divide the returning beam into a 0-order diffraction beam, a first The first, third, and fifth diffraction beams are +1 order diffraction beams, and the second, fourth, and sixth diffraction beams are -1 order diffraction beams. As shown in "Figure 7", it is an optical structure diagram of "Figure 6 A" and "Figure 6 B", showing that the holographic optical element 2 0 focuses the returning light on the light sensor module 3 0 In the situation, the 0th-order diffracted beam 40 of the holographic optical element 20 will focus on the aforementioned V, VI, VII, and VIII blocks to form a light spot SP. These four blocks V, VI, VII, and VI II will Corresponding first electrical signals (generally voltage signals) are generated according to the energy of the received light points, and this first electrical signal will be provided to a focused signal generating circuit 3 4 by (V + VII)-( VI + VIII) formula to obtain the astigmatism focus signal (Astigmatism FES, A FES); In addition, through the holographic optical element 20 + 1 order diffracted beam 4 1, focus on two corresponding I, II The light-sensing block forms a light spot SP 1; the -1 order diffracted beam 4 2 of the holographic optical element 20 is focused to the corresponding III and IV light-sensing blocks to form a light spot SP 2. Each light sensing block I, II, I ί I, IV also generates corresponding second and third electric signals (voltage signals This second and a third electric

Page 12 45585b V. Invention description (ίο) The signal is given again-follow the signal generation circuit 35, you can get the drag-type tracking signal by formula (I + I II)-(II + IV) P u S h--Pull TES, PPTES) y or the DPD tracking signal (DPD TES 9 DTES) obtained by the formula (I + IV) II + III) Figure _, which reveals the structure of the local optical system of the holographic optical pickup head. The electro-radiation generates a laser beam σσ10 emitted by a reflective element 50 (mirror) and reflected to the holographic optical element 20 and transmitted. , Xf The return light from the optical disc reflected from the optical disc will pass through the holographic optical element 20 again and will be diffracted to the light sensor module 3 0 to obtain the required signals such as data signal and focus signal And cyclic signal 〇1 Schematic symbol description] 10 • • Laser generator 11 • Collimation lens 12 Objective 13 • Optical disc 130 Data storage surface 14 • Beamsplitter 20 • Holographic optics 30% 3 0a • Light sensor module 3 1 Focusing quadrant light detection υσ 32 th-^ Tracking sensor array 33 Second tracking sensor array 34 Poly signal generating circuit 35 Tracking signal generating circuit

Page 13 4 5 5 8 5 V. Description of the invention (11) 36 ··· Voice coil driving circuit 361 ··· Voice coil 37 '.. Driving circuit 3 71. _ · Linear actuator 4 0.. · 0 Order diffracted beam 4 1., _ + Order 1 diffracted beam 4 2-order 1 diffracted beam 5 0.. Reflection element 1 · .. first diffraction region ii. · · Second diffraction region 1 i 1 · · · 3rd diffraction zone 1 V · · 4th diffraction zone V ·, 5th diffraction zone vi · '· 6th diffraction zone TD ·. Partition line RD parallel to the tangential direction of the disc track · · * Parallel to the radial dividing line SP, SP 1, SP 2 of the disc · · "Light spot TES" · · · FES signal · _ · Focus signal

Page 14

Claims (1)

4659_ VI. Scope of patent application 1 · A device used in optical pickups to eliminate the DC offset of tracking signals, which can convert a returning beam reflected from the data storage surface of an optical recording medium into a focused signal and a circular signal. The track signal includes at least: a holographic optical element arranged on the return optical path of the returning beam, the returning beam having a first diffraction region i located at the center of the returning optical path and distributed in the first diffraction region A second diffractive region ii and a third diffractive region iii on both sides of i, the holographic optical element is used to divide the returning beam into a 0th order diffraction beam, a first to third diffraction beam + 1st-order diffracted beam and -1st-order diffracted beams of first to third diffracted beams; a light sensor module with a focus quadrant type photodetector for the 0th-order diffracted beam Converted into a first electrical signal, a first tracking sensor array and a second tracking sensor array for converting the +1 order diffraction beam and the -1 order diffraction beam into a first Two telecommunications signals and a third telecommunication signal; a focused signal generates electricity Circuit for converting the first electrical signal into the focused signal; and a follow-up signal generating circuit for converting the second electrical signal and the third electrical signal into the tracking signal. 2 · The device for eliminating the DC offset of the tracking signal as described in item 1 of the scope of the patent application, wherein the 0th order diffraction beam forms a light spot on the focus quadrant optical detector. 3 * To eliminate the DC offset of the tracking signal as described in item 2 of the scope of patent application Page 15 45585 9 VI. Patent application device, wherein the focus quadrant type light detector includes first to fourth sensing blocks V, VI, VII, VIII adjacent to each other, wherein the V, VIII The two blocks and VI and VII blocks are separated by a dividing line parallel to the tangent direction of the disc track, and the two V and VI blocks and the VII and V Π I blocks are parallel to the disc The sheet is separated by a radial dividing line. 4 · The device for eliminating the DC bias of the tracking signal as described in item 3 of the scope of the patent application, wherein the first electrical signal will be given to the focus signal generating circuit according to the relationship of (V + VII)-(VI + VIII) Generates an astigmatic focus signal. 5. The device for eliminating DC bias of the tracking signal as described in item 1 of the scope of patent application, wherein the first compliance sensor array has two first and second sensing blocks I, II, and the second tracking sensor array has two third and fourth sensing blocks III, IV adjacent to each other, and the first to fourth sensing blocks I, II, III, and IV are all It is divided by a dividing line parallel to the tangent direction of the track of the optical disc, and is respectively used to convert the light spot into the second electric signal and the third electric signal. 6 · The device for eliminating the DC bias of the tracking signal as described in item 5 of the scope of the patent application, wherein the second signal and the third signal will be provided to the tracking signal generating circuit, according to (I _ II) The relationship of + (III-IV) produces a drag-like tracking signal. 7 _ The device for eliminating the DC offset of the tracking signal as described in item 1 of the scope of the patent application, wherein the holographic optical element and the light sensor module are Page 16 VI. Patent Application Fan Yuan-The laser generator used to generate the return beam is packaged together to form an integrated holographic optical element and light sensor module, which can be applied to holographic optical read heads To generate focus error and tracking error signals. 8 'The device for eliminating the DC offset of the tracking signal as described in the first item of the scope of the patent application, wherein the holographic optical element and the light sensor are applied to a conventional optical pickup head to generate a focus error and Tracking error signal. 9 · A device used in an optical pickup to eliminate the DC offset of the tracking signal, which can convert a returning beam reflected from the data storage surface of the optical recording medium into a focusing signal and a tracking signal, including at least :-Holographic optical element arranged on the return light path of the return light beam, the return light beam has a first diffraction area i and a second diffraction area ii located on both sides of the center of the return light light path, and is distributed on the first A third diffraction region 1 i and a fifth diffraction region v on both sides of the diffraction region i, and a fourth diffraction region iv and a sixth diffraction region distributed on both sides of the second diffraction region ii And the third diffraction area 1 i 1 is adjacent to the fourth diffraction area iv, the fifth diffraction area v is adjacent to the sixth diffraction area vi, and the two areas 1, 1 i, The two areas iii and iv and the two areas v and νι are separated by a radial dividing line parallel to the radial direction of the optical disc. The holographic optical element is used to divide the return beam into a 0th order diffraction beam, + 1st order diffraction beam for first, third, and fifth diffraction beams and -1 for second, fourth, and sixth diffraction beams Diffracted beam; Page 17 VI. Patent application scope A light sensor module with a focusing quadrant type light detector for converting the 0th order diffracted light beam into a first electrical signal and a first observable sensing Device array and a second compliance sensor array for converting the +1 order diffraction beam and -1 order diffraction beam into a second electrical signal and a third electrical signal; a focusing signal generating circuit, For converting the first electric signal into the focusing signal; and a tracking signal generating circuit for converting the second electric signal and the third electric signal into the following signal D 1 0. The device for eliminating the DC deviation of the tracking signal according to item 9, wherein the 0th-order diffraction beam forms a light spot on the focusing quadrant type light detector. 1 1. The device for eliminating DC bias of a tracking signal as described in item 10 of the scope of patent application, wherein the focus quadrant type light detector includes first to fourth sensing blocks V, VI, VII 'VIII, where the two blocks of V, VI ί and two blocks of VI, V 1 I are separated by a dividing line parallel to the tangent direction of the track of the optical disc, and the two blocks of V, VI The two blocks VII and V ί II are separated by a radial dividing line parallel to the radial direction of the optical disc. 1 2 · The device for eliminating the DC offset of the tracking signal as described in item 11 of the scope of patent application, wherein the first electrical signal will be given to the focus signal generating circuit according to (V + VII)-(VI + VIII) The relationship produces an astigmatic focus signal. 1 3 _To eliminate the DC bias of the cyclic signal as described in item 9 of the scope of patent application Page 4558ΰ 9 6. The device with a poor patent application range, wherein the first tracking sensor array has two first and second sensing blocks I and II adjacent to each other, and the second tracking The sensor array has two third and fourth sensing blocks III and IV adjacent to each other. The first to fourth sensing blocks I, II, III, and IV are all parallel to the track of the optical disc. The tangential direction is divided by a dividing line for respectively converting the light spot into the second electric signal and the third electric signal. 1 4 · The device for eliminating the DC deviation of the tracking signal as described in item 13 of the scope of the patent application, wherein the second and third signals will be provided to the tracking signal generating circuit, according to (I + III)-(Π + IV) relationship produces a drag-type tracking signal. 15. The device for eliminating the DC deviation of the tracking signal as described in item 13 of the scope of the patent application, wherein the second and third signals will be provided to the tracking signal generating circuit, according to (I + IV)-(II × I II) relationship produces a tracking signal for DPD. 16 · The device for eliminating the DC bias of the tracking signal as described in item 9 of the scope of the patent application, wherein the holographic optical element and the light sensor module are generated with a laser for generating the return beam The sensors are packaged together to form an integrated holographic optical element and light sensor module, which can be applied to a holographic optical pickup head to generate focusing error and tracking error signals. 1 7 · The device for eliminating the DC deviation of the tracking signal as described in item 9 of the scope of the patent application, wherein the holographic optical element and the light sensor are applied to a conventional optical pickup to generate a focus error Tracking error Page 19 Scope of Patent Application Signals. liiii p. 20