Operational Amplifier
The laser diode, evidently emits the leisure beam. The set of photodiodes is on the two operational amplifiers, one for adjustment of the focus and another one for adjustment of the trilhagem, this set of photo diodes serves to evaluate power of emission of the laser and to allow the perfect adjustment of the focus and the trilhagem, as well as a reading of the recorded information in the record. The two sets of bobbins are: Bobbin of focus, makes the heave of the objective lens (up and down) and is controlled for the Servant of Focus. trilhagem bobbin, generates the lateral motion of the objective, and is controlled for the Servant of Trilhagem.O FUNCTIONING When we place the COMPACT DISC in the device and close the cover, or drawer, a placed key strategically is closed, ‘ ‘ avisando’ ‘ to the Microcontroller of the system, that exists a record to be twirled. The microcontroller (that it is obedient) sets in motion the engine of the stand that locates the unit at the beginning optics of the record (the center of the record) where is the TOC (content table) a species of archive with the number of bands, duration of each band, etc. When the unit optics arrives at the beginning of the record, one another key, called limit key informs to our microcontroller, that immediately it disconnect the engine of the stand and sets in motion the engine of the record that starts to turn so that it is deals the TOC. Here the work of the Unit starts Optics.
The laser beam reflects in the record and in the return it is deviated by the prism that does not allow that it comes back to the laser diode emitted that it. THE FOCUS The beam it follows in direction to the set of photodiodes, if the height of the record will be certain, the set of photodiodes will receive the same amount from light and the result in the exit of the Operational Amplifier will be zero, therefore the focus is correct. If the record will be very close or very far, a signal FAITH (error of focus) is generated. This signal FAITH is applied to the focus bobbin that corrects the positioning of the objective lens. THE TRILHAGEM Beyond the focus, the necessary beam if to locate in the certain track, for that is used the same joint of photodiodes (with a method called phase difference) that they generate the signal YOU (error of trilhagem) this signal is applied to the trilhagem bobbin producing a lateral motion of the beam. THE SIGNAL OF AUDIO It remembers the dark points and shining points printed matters throughout the tracks of the COMPACT DISC. infra red light, emitted for the laser diode and reflected in these points of the record, it is applied to the set of photodiodes that, in turn sends these dark and shining points to converter A/D (analogical/digital) it transforms that them into ‘ ‘ some or zeros’ ‘ (binary data), later they are tranformados in sound (analogical signal) through converter D/A (digital for analogical) and amplified normally.