Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1999-08-11
2000-11-21
Hindi, Nabil
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369 4437, 369112, G11B 700
Patent
active
061512915
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an optical reading device for reading digital data from a reflecting medium, this device being of the kind such as those which comprise a lighting source, means for focusing the beam emitted by the source onto an area of the medium, means for receiving the light energy reflected and means for processing the signals delivered by the receiving means.
The invention relates more particularly, but not exclusively, to such an optical reading device for laser-read disks, especially for audio disks.
The advantages of optically read digital data media are known. These media make it possible to store a large quantity of data in a reduced volume. Access to this data is fast and reading, which does not involve any mechanical contact, causes no wear to the medium. Furthermore, the quality of data reproduction is enhanced.
However, the digitizing of the data involves sampling which, for the low amplitude levels of the analog signal before digitization, may introduce data losses. Furthermore, the transferring of the digital data to the medium is necessarily accompanied by inaccuracies of manufacture, despite all the precautions taken. Additionally, the means for processing the signals provided for in the reading device involve one or more algorithms aimed at compensating for the data losses due to the inevitable imperfections of implementation, and at improving the signals reproduced.
Nevertheless, it is noted that, on reproduction of the data, there are still some points to be improved. In particular, in the case of laser-read audio disks, it is acknowledged that there is a degree of harshness and a degree of hardness to the sounds reproduced.
The purpose of the invention is, above all, to provide a device for optical reading by reflection, of the kind defined above which makes it possible to alleviate the drawbacks mentioned above, whilst remaining simple and relatively cheap.
According to the invention, an optical reading device for reading digital data from a reflecting medium, of the kind defined above, is characterized in that it comprises at least one second unfocused lighting means installed on or near the reading device so as to use its beam to illuminate the focusing area of the source on the medium, the wavelength and the luminous power of this second lighting means being chosen in such a way that the reproduction of the data is improved.
It has been noted, surprisingly, that the fitting of this second unfocused lighting means alleviated the aforesaid drawbacks; in particular, in the case of an optical reading device for laser-read disks, a noticeable difference in the reproduction of sounds has been noted when listening, the device of the invention improving the softness of reproduction and to a large extent removing the harshness and the hardness which are generally objected to when reading disks of this type.
The wavelength range of the second lighting means lies, preferably, in a region complementary to the wavelength range of the lighting source.
In the case of a source emitting in the red or the infrared, good results are obtained with a second lighting means emitting in the blue range of the visible spectrum. In particular, the second lighting means emits at a wavelength of 430 nanometers.
Means for adjusting the luminous power of emission of the second lighting means are advantageously provided.
This second lighting means preferably consists of a light-emitting diode. This diode is mounted in a supply circuit in series with an adjustable resistor. The user can adjust this resistor, especially in the case of the reading of an audio disk, to obtain the reproduction which seems preferable to him when listening.
The device of the invention can be applied not only to laser-read audio disks, but also to laser-read video disks.
The invention consists, apart from the provisions set out above, of a number of other provisions which will be dealt with more explicitly below in connection with an embodiment described together with references to the appended drawing, but which is in no way l
REFERENCES:
patent: 5754514 (1998-05-01), Guerra
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