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US 3,983,317 AGranted
Astigmatizer for laser recording and reproducing system
AssigneeTeletype Corporation
InventorCharles A. Glorioso
Life of this patent
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AssigneeTeletype Corporation
InventorCharles A. Glorioso
Estimating the term…
In a laser recording system, a high energy intensity laser beam is focused to form a circular write-spot on a rotating thermoplastic disc. This spot creates tracks of grooves and flat areas or lands in accordance with input data. To read the data from the disc a reduced energy beam is focused on the previously recorded track, and the pattern of grooves and lands is determined from the reflected energy. The optics associated with the reading process include an astigmatizer which elongates the read-spot in a direction transverse to the track. This reduces mechanical tolerances required to insure that the read-spot will impinge upon the desired track. The astigmatizer may also serve to reduce the beam spot energy intensity so that the same laser, without the astigmatizer, can be used for the recording process. In one embodiment, the astigmatizer is a movable plate having a single slit. For reading, the astigmatizer is positioned in the beam path and the slit creates an orthogonal diffraction pattern which provides the elongated read-spot of reduced energy intensity.
In combination with a recording and reproducing system of the type having a recording surface being recorded thereon in a pattern of grooves arranged along a track, means for moving the track, a beam source, means for directing a source beam from the beam source continuously along the track on the surface, and means for detecting a reflected beam of energy from the surface to produce an output indicative of the groove pattern on the track, the improvement wherein:
A recording and reproducing system comprising, a recording surface, a beam source for generating a high intensity beam of energy, means for directing the beam of energy from the source to a focused spot on the surface, means for moving the focused beam spot relative to the surface, means operable in a write mode for modulating the beam in accordance with input data to cause the focused beam spot to create a depression in the surface representative of selected data bits, the relative movement causing the representation of data to form a pattern of depressions along a track in the direction of relative movement, means operable by being removably positioned in the path of the beam from the source to the surface exclusively in a read mode distinctive from the write mode for astigmatizing the unmodulated beam to form an elongated cross-section of the beam and of the focused beam spot so that the dimension of the focused spot in the direction transverse to the track is greater than its dimension in the direction of the track, said means for directing the beam being operable in the read mode to focus the astigmatized beam to the surface so that the astigmatized beam is reflected from the surface, and means for detecting from the reflected beam an indication of the pattern of depressions.
Dependencies are inferred from the claim text.