Laser turntable plays records like CDs

The ELP laser turntable reads LPs with lasers — the manufacturer claims that the lasers can read "virgin" parts of the grooves that haven't been touched by needles and produce a better sound, and that the five laser read-head lets you skip forward and back across or within tracks as you would with a CD.

Two Tracking Laser beams are directed to the left and to the right shoulders of the groove of the record. Only the part of the beams that reach the groove are reflected to two PSD (Position Sensitive Detector) optical semiconductors. The part of the beams that fall on the land area of the record are deflected and not picked up by the PSD devices. The signals are sent to a microprocessor via analog to digital converters, then to servos to maintain the reader head position directly above the groove.

Two additional laser beams are directed at the left groove wall and the right groove wall just below the tracking beams. Modulation on the individual grooves is reflected to scanner mirrors and onto left and right photo optical sensors. The variations of the modulated light cause the audio sensors to develop an electrical representation of the mechanical modulation of the grooves. The entire sound reproduction chain is analog.


(via Digg)

Update: Darrin points out this former business-partner of ELP's warning you to stay away from them, and Luke raises some objections about the science behind the turntable.

Update 2: Steve sez, "I designed a laser turntable and described it in my 1982 book, Industrial Design with Microcomputers (Prentice-Hall), to illustrate some concepts of optical sensing. I never took it any further or actually built one (I got a bit distracted by computerized bicycles; besides, CDs were starting to appear, so it became a less interesting hack). Amusing, nevertheless, to see that someone is supposedly doing it…