Method and apparatus for removal of dust from an information carrier during recording and playback

A method and apparatus for removing dust from an information carrier includes a rotating member having at least one channel extending therethrough, operative to act as a centrifugal pump, and also includes apparatus for recording or playback of information from the information carrier.

CROSS REFERENCE TO RELATED APPLICATION 
This application is related to the application entitled "INFORMATION 
RECORDING METHODS AND APATUS" filed by John H. Jacobs on Apr. 12, 1985, 
Ser. No. 06/722,200, a divisional application of U.S. patent application 
Ser. No. 06/459,440, filed Jan. 20, 1983, now abandoned. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to an information recording and playback 
method and apparatus and in particular to an information scanner which 
provides a flow of filtered air onto an information carrier to thereby 
remove dust from the information carrier. 
2. Disclosure Statement 
One of the problems in optical digital recording is the presence of dust 
particles on the information carrier which, by obstructing a light beam, 
may prevent the recording of portions of information, or may prevent the 
playback of previously recorded information. 
Several configurations of optical scanners are disclosed by John H. Jacobs 
in the above cross-referenced U.S. patent application. These 
configurations show an optical scanner having at least one lens, where the 
scanner rotates adjacent to an information carrier which may be either 
stationary or moving. The axis of rotation of the scanner is substantially 
perpendicular to the information carrier. 
Because of the size of each information unit in an optical digital 
information carrier, particles of dust may block out part or all of an 
information unit with the result of an error in playback of that 
information unit. Likewise during a recording process, a dust particle may 
prevent the recording of an information unit. None of the configurations 
in the above cross-referenced U.S. patent application provide means for 
removal of dust particles on the information carrier. 
Accordingly, it is desirable to provide a method and apparatus for the 
removal of dust particles from an information carrier during recording and 
playback. 
SUMMARY OF THE INVENTION 
This invention is directed toward a method and apparatus for removing dust 
particles from an optical information carrier. In general, this is 
accomplished by utilizing an optical scanner in the form of a rotating 
member such as a disc. The disc contains at least one channel which has 
been bored into the disc such that as the disc rotates, the channel acts 
as a centrifugal pump, thereby causing air to flow through each channel 
and onto the information carrier. In addition, a filter may be added to 
each channel to remove dust particles from the air before the air strikes 
the information carrier. Alternatively, a single filter may be utilized to 
provide filtered air to more than one channel. 
Many additional features and advantages of the invention including the 
adaptability of the invention to other types of information carriers, such 
as magnetic, will be apparent from a reading of the specification in which 
an illustrative embodiment of the invention is described in detail. This 
specification is to be taken with the accompanying drawing in which the 
various characteristics of the preferred embodiment are illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing, FIG. 1 shows an optical scanner 10. The scanner 
consists of an optical beam focusing means, specifically a set of lens 
assemblies 12, 14, 16 and 18, mounted near the outer periphery of a disc 
20. Although four lens assemblies are shown in FIG. 1, any number of lens 
assemblies may be utilized in practicing the invention. Furthermore, 
although the lens assemblies 12, 14, 16 and 18 are shown to be symmetrical 
with respect to each other, the lens assemblies may be arranged at any 
selected angle with respect to each other. In addition, although lens 
assemblies are utilized, any other information handling element or 
transducer may be substituted for each lens assembly. 
A shaft 22 is fixedly mounted to the disc 20 to thereby transfer rotational 
motion from an external drive means (not shown) to the disc 20. The disc 
20 and the shaft 22 rotate about an axis 24. 
Within the disc 20 is a set of four channels. It is to be understood that 
any number of channels may be utilized in practicing the invention. 
Referring to FIG. 1, a channel 26 is comprised of a bore 28, a plenum 
chamber 30 and a filter chamber 32. The cross-sectional area of the 
channel 26 increases in two steps such that the cross-sectional area of 
the plenum chamber 30 is larger than the cross-sectional bore 28, and the 
cross-sectional area of the filter chamber 32 is larger than the 
cross-sectional area of the plenum chamber 30. 
Although not shown in FIG. 1, a channel extends from the top surface of a 
set of filters 34, 36 and 38 to the opposite side of the disc 20 as does 
the channel 26. 
Referring now to FIG. 2 the cross-sectional area of a channel 44 increases 
in two steps toward a first planar surface 42 of the disc 20 to thereby 
provide a bore 40, a plenum chamber 46 and a filter chamber 48. As shown 
in FIG. 2, the filter 34 is mounted within the filter chamber 48. The 
filter 34 may be secured with an adhesive or other suitable means. In the 
preferred embodiment of the invention a filter would be secured within the 
filter chamber 32. Such a filter is omitted in FIG. 1 for purposes of 
illustration. 
The filter chamber 48 provides a passageway between the first planar 
surface 42 and the plenum chamber 46. The bore 44 provides a passageway 
between the plenum chamber 46 and a second planar surface 50 of the disc 
20. Although FIG. 2 shows the outlet of the bore 44 adjacent to the end of 
the lens assembly 12 which is closest to an information carrier 52, that 
end of the bore 44 may be positioned away from that end of the lens 
assembly 12. 
In operation, the shaft 22 is rotated by an external drive means (not 
shown) to thereby rotate the disc 20 about the axis 24. Referring to FIG. 
2, because the end of bore 44 closest to the information carrier 52 is 
further from the axis 24, than is the center of the filter chamber 48, as 
the disc 20 rotates, from the frame of reference of the disc 20 
centrifugal force causes air to be forced through the filter 34 and the 
plenum chamber 46 through the bore 44 and onto the information carrier 52. 
In further detail, assuming for purposes of explanation that the 
information carrier 52 is stationary, as the shaft 22 rotates, from the 
frame of reference of the information carrier 52, all portions of the disc 
20 are accelerated toward the axis 24 in order to maintain the circular 
motion of the disc 20. Since the frictional or binding forces between the 
disc 20 and the air within the channel 40 are minimal, as the disc 20 
rotates the air within the channel 40 is accelerated at a lower rate than 
is the disc 20, thereby causing a pressure differential between the filter 
chamber 48 and the end of the bore 44 adjacent to the information carrier 
52. This pressure differential causes air to flow from a higher pressure 
area to a lower pressure area. In this case, the lower pressure area is 
the end of the bore 44 adjacent to the information carrier 52. 
If desired either the plenum chamber 46 or the filter chamber 48 or both 
may be eliminated by extending the bore 44 from the second planar surface 
50 to the first planar surface 42. As previously stated, the filter 34 
filters the air prior to its exit onto the information carrier 52. The 
plenum chamber 46 operates to increase the flow of air through the bore 
44. 
Alternatively, two bores may share a common filter, filter chamber and 
plenum chamber. As shown in FIG. 3, a pair of bores 54 and 56 communicate 
with a single plenum chamber 58, a single filter chamber 60 and a single 
filter 62 within a disc 64. The filter 62 is shown in a fragmented view to 
more clearly illustrate the configuration of the bores 54 and 56. The 
bores 54 and 56 each extend from the plenum chamber 58 through the disc 64 
to areas adjacent to optical beam focusing means 66 and 68 respectively. 
In the same manner a with the embodiment of FIGS. 1 and 2, as a shaft 70 
rotates about its axis, to thereby cause the disc 64 to rotate, 
centrifugal force causes air to flow through the filter 62, the filter 
chamber 60, the plenum chamber 58 through the bores 54 and 56 and onto an 
information carrier 72 to thereby force dust particles from the 
information carrier 72. 
Furthermore, the rotating structure need not be in the form of a disc but 
could be any rotating member having the required channel. For example, a 
single rotating arm could be utilized. In addition, instead of lens 
assemblies as shown in the preferred embodiment, optical transducers, 
magnetic transducers, capacitive transducers, mirrors or any suitable 
information handling elements could be utilized. 
It is to be understood that the subject invention has been described by 
reference to specific embodiments and that many additions and 
modifications thereto will be apparent to those skilled in the art. 
Accordingly, the foregoing description is not to be construed in a 
limiting sense.