JPH08249720A - Apparatus system and method for readout of optical disk - Google Patents

Abstract

PURPOSE: To read an optical disk which is increased in density and capacity by sending light, reflected by a disk surface, to a TDI detection matrix through an objective and a tubular lens, and putting electric charges together by a plurality of parallel lines and respective detectors. CONSTITUTION: The light reflected by the disk surface is converged by the objective 12 and reflected by a mirror 8 toward a beam splitter 6. This beam splitter 6 reflects the light toward the tubular lens 14. The tubular lens 14 forms a microscope with the objective 12 and the disk is reflected to correct a chromatic aberration originating from a wide-band lighting system. The light from the tubular lens 14 is directed to a CCD/TDI detector matrix 16. Then the TDI 16 is equipped with a plurality of parallel lines and includes many detectors. Electric charges generated with light directed to the respective detectors for the lines are moved to adjacent detectors of adjacent lines and put together with electric charges of the adjacent detectors. Then the electric charges are read out of the final column.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical memory disk, and more particularly to an optical memory disk having a high data density and a high processing capacity ratio. More particularly, the present invention relates to optical disc reading utilizing a large area illumination source.

[0002]

BACKGROUND OF THE INVENTION Various optical discs consist of a disc with a reflective coating material, which has concentric or spiral tracks on which data is in the form of spots of change for some optical properties of the disc coating medium. Written. These changes are typically spots of lower reflectivity than the non-data containing portions of the disc. These data spots are spread out along a spiral or circular path on the disc. The disk is divided into sectors, and each loop of this spiral path within a sector is called a track.

Data is read from the optical disc by an electro-optical head, which projects a light intensity focused laser beam onto a rotating disc. The reflected light from the disc is detected and further converted into an electronic signal. At any point in time, the electron −
The optical head reads one data spot. The rotation of the disc makes it possible to read the track spot by spot. To read the data from the inner or outer track, the electro-optical head is moved to the desired track position by a motor. The data reading is done serially along the spiral path.

Commercially available CD-ROMs (Comp
Data conversion rate of act Disk Read Only Memory) is about 157 K
Byte / sec. CD-ROMs memory storage capacity is about 6
40MByte (for example, Publication E-93176PDO-0032,4 / 87 to Ph
ilips and DuPont Optical)). The limit of memory storage capacity is a function of wavelength and numerical aperture of the objective lens. One known method is to use optical memory disks of all kinds, eg CD-ROMs, WORM (Write
In Once Read Many) and magneto-optical disks, a way to increase memory capacity is to reduce the wavelength of the light emitted by the diode laser, which illuminates the data tracks of the optical memory disk. The wavelength reduction results in smaller data spots on the disc, thus higher resolution and higher data density. Current CD-ROMs employ a wavelength of 780 nanometers (nm).

For example, with the advent of new diode lasers that emit blue light (about 481 nm), the potential for increasing optical disk data density increases. However, the blue light diode laser emits low energy, which is not suitable for the reading / writing process of optical discs. Furthermore, these diodes are expensive and their operating life is very short.

Another way to achieve blue emission is by doubling the frequency for infrared lasers with non-linear optical materials. However, this system has very low frequencies and is not yet commercially available ("Compact Blue Laser Device Based on Non-Linear Frequency Up Convention""C
ompact Blue Laser Devices Based on Non-Linear Freq
uency Upconvension "WPRisk and W.lenth, IBM Reserc
h Division, SPIE Vol.7104,1989) Demetri Psaltis, "Parallel Optical Memories", BYTE Magazine, 9
In an article by Moon, 1992, pp.179, parallel access to an optical disk is described by illuminating the disk with a wide light beam without well focusing the spots. It is further stated that an increase in storage density is achieved by the development of required shorter wavelength semiconductor lasers. This is because the minimum area required to store a pixel is equal to the squared wavelength.

DC Kowalski et al, "Multichannel digital optical disk memory systems".
ystem, Optical Engineering, Vol.22, No.4, July / August,
An article by 1983, pp. 464, describes a write and read optical head for an optical disc system. It employs a gas laser to write and read data. The writing laser is an optical power argon laser, and the reading is performed by a low power HeNe laser.
Both lasers are expensive and bulky when compared to semiconductor diode lasers used in commercial equipment.

Another prior art system is the Demetri Psalit
is, “Optical Memory Disks in Optical Information Processing”, “Opt
icalmemory disks in optical information processin
g "Applied Optics, Vol.29, No.14 May 10, 1990, and
USPatent 5,1111, 445 to Psaltie et al.

US Patent Application No. 043,254, filed April 6, 1993 (corresponding to EP 93105995.0), the description of which is incorporated herein by reference, describes the optical reading mechanism of an optical disc. By employing a CCD / TDI detector matrix, a laser diode illumination system, and an image processing device for tracking and detection, it is possible to read many tracks in parallel.

To date, prior art systems have employed laser diodes to illuminate the optical disc, or, as noted above, seek to improve the performance of the optical disc system by providing more sophisticated lasers. Came. Prior art systems, however, present severe drawbacks. This is due to the high cost of improving the laser light for the purpose of CD illumination. Therefore, it would be highly desirable to be able to provide an improved system that does not require such expensive and low efficiency laser light sources.

[0011]

It has been found that it is possible to read data from a CD track without the use of light from a high efficiency laser source, which is the object of the present invention. Wide area illumination, for example using a simple LED, makes it possible to read the data from the track of the CD, and uses the light from the LED but can be advantageously developed to improve the data rate read from the CD. It has been found that this is another object of the invention.

Accordingly, it is an object of the present invention to provide a read system with an optical disc having an increased data density capacity. Furthermore, it is an object of the present invention to provide a higher data retrieval rate for an optical disc read system.

[0013]

An optical disk reader system according to the present invention comprises: a wide area illumination source for illuminating at least a portion of one track of an optical disk; and an optical disk illuminated by said wide area illumination source. It is provided with means for detecting the reflected light and means for combining the light in the direction along the track detected by the detecting means.

According to a preferred embodiment of the invention, the means for detecting the light reflected from the optical disc and further for summing said light contributions comprise a CCD / TDI detector. This CCD / TDI detector may, for example, be of the type described in the above-mentioned patent application Ser. No. 043,254. According to a preferred embodiment of the invention, an optical disc reader system comprises: a wide area illumination source for illuminating at least one track of the optical disc, and for projecting at least part of a beam from said wide area source onto the optical disc. An optical system for projecting an illuminated area of the disc onto a detector, a detector for detecting the beam reflected from the optical disc and for converting the detected light into an electrical signal.
A processor for processing the electrical signal.

The preferred illuminator is an LED illuminator. Therefore, in yet another preferred embodiment of the present invention, the lighting system comprises at least one light emitting diode (LED).
It comprises an illuminator and a bandpass filter for passing at least part of the light emitted by the LED illuminator. As will be appreciated by those skilled in the art, solid state wide area and wide area-band lighting systems such as LEDs.
To provide CD-ROMs that operate at shorter wavelengths without the use of expensive and bulky laser systems and without the use of diffraction limited illumination sources. To enable.

The system according to the invention comprises a detector matrix adapted to collect light from a large area of the optical disc. As will be appreciated by one of ordinary skill in the art, the system of the present invention may be used as described in the above-referenced continuation-in-part US patent application to simultaneously read multiple tracks in parallel. To enable.

All the above and other features and advantages of the present invention can be more fully understood through the following description and non-limiting description of the preferred embodiments of the present invention with reference to the accompanying drawings.

[0018]

EXAMPLE FIG. 1 will be described. This is a block diagram of a CD-ROM electro-optical read head constructed and operative for the preferred embodiment of the present invention. A light emitting diode (LED) illumination system 2 illuminates the disc 4 via an optical system, which comprises a beam splitter 6,
It comprises a mirror 8 and an objective lens system 12. The light reflected from the disk surface is collected by the objective lens 12 and reflected by the mirror 8 toward the beam splitter 6. In the beam splitter 6, the light passes through the tubular lens 14
Is reflected toward. The tubular lens 14 together with the objective lens 12 form a microscope, which reflects the disc and corrects the chromatic aberrations caused by the broadband illumination system. Light from the tubular lens 14 is directed to the CCD / TDI detector matrix 16. As an option, the detector matrix 16 may be a CCD detector matrix.

TDI (Time Delay and Integration) 1
6 has a plurality (tens or hundreds) of parallel lines and includes a large number (hundreds or thousands) of detectors. The charge generated by the light directed to each detector in the line is transferred to the adjacent detector in the adjacent line of detectors and can be summed with the charge in the adjacent detector. If the transfer of charge from one line of the detector is synchronized with the movement of the data spot along the detector column, the charge generated by the moving data spot of the detector in one of the columns is due to this transfer. Summed up to give a stronger signal to the last column of detectors. The charge from the last column is transferred to the read shift register. Each shift register is connected to the last column portion of the detector, and the charge from the detector in that portion is transferred to it. The charge from each cell of the shift register is read out in series. The read rate from the shift register is approximately the transfer rate of one detector divided by the number of detectors connected to the shift register. The read data rate from the shift register limits the rate of charge transfer from column to column. Since the column-to-column charge transfer is synchronized with the movement of the detector matrix data spots, the read rate must be equal to the optical disc data rate. Therefore, the number of detectors connected to each shift register should match the required read rate and detector transfer rate.
For example, for a disc with 15 Mspot / sec. And a CCD detector with a transfer rate of 60 Mhz, each shift register has 4
Connected to two detectors.

In another preferred embodiment of the invention, the detector matrix may be any type of detector arrangement that integrates the signals generated by multiple detectors. The light detected by the detector matrix 16 is the image processing unit 1
It is converted in the detector matrix into an electrical signal which is processed in 8. 2A and 2B will be described. Other lighting system embodiments are shown which may be used in the preferred embodiment of the present invention. FIG. 2 (a) shows a KOHLER lighting system according to a preferred embodiment of the present invention. The light from the LED array 30 passes through the projection lens 32 and the objective lens 36.
Is focused on the aperture. The bandpass filter 34 reduces the illumination bandpass to the bandpass corrected by the tubular lens of FIG. 1 by passing light concentrated in the dominant wavelength. Alternatively, the bandpass filter may be omitted if the correction bandpass is large enough. The light is focused on the focal plane behind the objective lens 36. Objective lens 36 condenses the light into a beam that uniformly illuminates disk 38.

FIG. 2 (a) shows a CRITICAL lighting system according to a preferred embodiment of the present invention. The LED array 50 illumination source is located in the focal plane of the projection lens 52. The projection lens 52 collimates the light into parallel beams. The bandpass filter 54 reduces the illumination bandpass to the bandpass corrected by the tubular lens 14 of FIG. 1 by passing light that is concentrated in the dominant wavelength. Alternatively, the bandpass filter may be omitted if the correction bandpass is large enough. The light is focused on the disk 58 by the objective lens 56.

The system of FIGS. 2 (a) and 2 (b) includes various LED arrays 30 and 50, such as a single LED, an LED array with an attached lens array, or a pigtail LE.
A D array may be provided. 3 for these systems
Various laser arrays can be provided to replace 0 and 50, such as a single laser, a laser array, a laser array with a lens array or a pigtail laser array.

It should be noted that the system of FIGS. 2 (a) and 2 (b) may not be provided with separate bandpass filters 34 and 54, respectively. In this case, the beam splitter 6 may be provided with a suitable coating layer which provides the required filtering. FIG. 3 will be described. The pattern of a prerecorded optical memory disc is shown schematically. The disk 70 is divided into a plurality of tracks 72. The data spots 74 are formed on the tracks. The space between two data spots on a track is called the non-data spot. The disk 70 is a CCD / T
The projection 76, which is imaged by a DI matrix (not shown), is a matrix of pixels 78, where each data spot is imaged by at least one pixel. In the preferred embodiment of the invention, each track cross section is imaged by one or more pixels. When the desk is rotated, the data spots 74 are swept along the TDI direction, and the light generated along the TDI direction by the detectors of the CCD / TDI detector matrix is accumulated in an image processing unit (not shown). It is processed to produce a track image.

In contrast to a laser illumination system, the focused LED illumination system according to the present invention illuminates a relatively large area but not a diffraction limited spot. The required signal level is achieved by the integration process performed by the CCD / TDI detector matrix. The integration time is matched to the scanning speed of the disc. FIG. 4 shows the experimental setup used to generate the images on the CD-ROM. Setup is equipped with CDROM80, Olympus
Located under the BHMJL microscope 96. The objective lens used was Olympus LWD MSPL20XLCD1,1,82, eyepiece
NFK6.7 x 88, camera adapter lens (0.3 x) 92, Dalsa
CA-D1 frame camera 92, image MFG frame grabber94
And was connected to a PC (not shown). The used LED is red HP LED HLMP8109
And used a central wavelength of 645 nm. The image obtained with this setup is shown in FIG. 5, with the image gray level extended to 7 bits for ease of display.

All the above description of the preferred embodiment is given for the purpose of illumination and is not intended to limit the invention in any way. Many variations can be made with the system of the present invention. For example, different LED sources may be used, different optical systems, lenses, etc. may be assembled or different detection means may be used without going beyond the scope of the invention at all.

[0026]

As described above, according to the present invention, it is possible to provide an optical disc having a high data density capacity to a reading system.

[Brief description of drawings]

FIG. 1 shows a schematic block diagram illustrating an optical memory disk reader according to a preferred embodiment of the present invention.

FIG. 2 is a diagram showing an optional configuration illustrating an illumination system adopted for a system according to a preferred embodiment of the present invention.

FIG. 3 is a diagram illustrating a pattern of an optical memory disc which is recorded in advance.

FIG. 4 shows an experimental setup used to generate an image of a CD ROM that uses LEDs.

5 is a photograph of an image produced by the setup of FIG.

[Explanation of symbols]

 2 ... LED illumination system 4 ... Disk 6 ... Beam splitter 8 ... Mirror 12 ... Objective lens 14 ... Tubular lens 16 ... Detector matrix 18 ... Image processing device

Claims (9)

[Claims] 1. A wide area illumination source for illuminating at least a part of one track of an optical disk, means for detecting light reflected from the optical disk illuminated by the wide area illumination source, and the detecting means. An optical optical disc reader system comprising means for combining light in directions along detected tracks. 2. The optical disk reader system of claim 1, wherein the wide area illumination source is an LED illuminator. 3. The optical disc reader system of claim 1, wherein the large area illumination source is a laser array. 4. The means for detecting the light reflected from the optical disc and further summing the contributions of said light is CC
Optical disc reader system according to any one of claims 1 to 3, comprising a D / TDI detector. 5. A large area illumination source for illuminating at least one track of the optical disc, and for projecting at least a portion of the beam from the large area source onto the optical disc, and the illuminated area of the disc to a detector. An optical system for projecting, a detector for detecting the beam reflected from the optical disc, and a detector for converting the detected light into an electric signal, and a processor for processing the electric signal. An optical disc reader system according to any one of claims 1 to 4, comprising. 6. The lighting system of claim 1, wherein the lighting system comprises at least one light emitting diode illuminator and a bandpass filter for passing at least a portion of the light emitted by the LED illuminator. The optical disc reader system according to any one of claims 1. 7. Illuminating at least one track of an optical disc with light generated by a wide area illumination source,
A method of reading data from an optical memory disc, comprising detecting light reflected from an optical disc illuminated by the wide area illumination, and combining the contributions of the reflection irrationals detected by the detection means in the direction along the track. . 8. A beam from a large area illumination source illuminates at least one track of the optical memory disk, at least a portion of the beam from the large area illumination source, and a portion of the light reflected from the illuminated light memory disk. 8. A method of reading data from an optical memory disk according to claim 7, comprising collimating, detecting the reflected light, converting the detected light into an electrical signal and processing the electrical signal. 9. The method of reading data from an optical memory disk according to claim 7, wherein the wide area illumination source is an LED illuminator.