The present invention is a pre-aligner capable of determining the center of a wafer by casting light onto a wafer that is positioned above a charge-coupled device (CCD). The pre-aligner performs this operation by directing light emitted from a single LED simultaneously onto the wafer and the CCD. The light emitted from the LED is directed through a light guide in order to direct the light onto the wafer and CCD. A lens collimates the light exiting the light guide such that the light, as it passes the wafer's edge, is substantially perpendicular to the wafer's edge. The light guide may be removably secured to the pre-aligner housing for easy installation removal. The pre-aligner is capable of self-calibrate the LED.
1. An aligner for aligning substantially flat workpieces having an edge, comprising:
a light emitting diode;
a sensor having a top surface that is capable of sensing light;
a chuck for rotating the workpiece substantially about the geometric center of the workpiece, said chuck supporting the workpiece such that the edge of the workpiece is suspended over said top surface of said sensor;
a light guide having an inlet and an outlet, said light guide including a plurality of internal reflective surfaces, each one of said plurality of internal reflective surfaces for directing light emitted into said inlet by said light emitting diode towards said outlet; and
a collimating lens seated within said outlet; and
wherein said light emitting diode is not housed within said light guide.
2. The aligner according to claim 1 , wherein said light emitting diode is located substantially beneath said inlet of said light guide device.
3. The aligner according to claim 2 , wherein said light emitting diode emits light upward into said inlet.
4. The aligner according to claim 1 , wherein said sensor comprises a charge coupled device.
5. The aligner according to claim 1 , wherein a workpiece seated on said chuck casts a shadow on said sensor when said light emitting diode is emitting light into said light guide.
6. The aligner according to claim 1 , wherein said lens comprises a convex lens.
7. The aligner according to claim 1 , wherein said plurality of reflective surfaces comprise mirrored surfaces.
8. The aligner according to claim 1 , further comprising a printed circuit board.
9. The aligner according to claim 8 , wherein said light emitting diode and said sensor are mounted on said printed circuit board.
10. An apparatus for aligning a wafer, comprising:
a light emitting diode;
a sensor having a top surface that is capable of sensing light;
a chuck for rotating the wafer substantially about the wafer's geometric center, said chuck supports the wafer such that the wafer is suspended over a portion of said top surface of said sensor; and
a light guide having an inlet and an outlet, said light guide including:
a plurality of reflective surfaces, each one of said plurality of reflective surfaces for reflecting light emitted into said light guide by said light emitting diode towards said outlet;
means for collimating light passing through said outlet; and
wherein said light emitting diode does not emit light directly towards said sensor.
11. An aligner for aligning substantially flat workpieces having an edge, comprising:
a light guide having an inlet and an outlet;
a light emitting diode located beneath said inlet of said light guide;
a sensor having a top surface that is capable of sensing light;
a chuck for rotating the wafer substantially about the wafer's geometric center and suspending a portion of the wafer over said top surface of said sensor;
said light guide including a plurality of internal reflective surfaces, each one of said plurality of internal reflective surfaces reflecting light emitted into said inlet by said light emitting diode and redirecting the light towards said outlet; and
a collimating lens seated within said outlet.
12. The aligner according to claim 11 , wherein a workpiece seated on said rotating chuck casts a shadow on said sensor when said light emitting diode is emitting light into said light guide.
13. The aligner according to claim 11 , wherein said collimating lens comprises a convex lens.
14. The aligner according to claim 11 , wherein said plurality of internal reflective surfaces each comprise a mirrored surface.
15. The aligner according to claim 11 , further comprising a printed circuit board.
16. The aligner according to claim 15 , wherein said light emitting diode and said sensor are mounted on said printed circuit board.