US 4,643,569 A · Dual beam laser inspection apparatus

Abstract

An optical input beam is split into first and second beams lying in first and second non-parallel planes. A polygon mirror scanner receives the first and second beams on a single facet and generates first and second angularly displaced, non-parallel synchronized scans. Redirecting means is positioned in the optical path between the scanner and a scanned plane for redirecting a portion of the first and second synchronized scans onto a timing plane to generate third and fourth non-coincident, synchronized scans. A beam position signal consisting of equally spaced, sequential pulses is generated in response to the travel of either the third or fourth synchronized scan along a second scanned line lying within a timing plane. The beam position signal is representative of the position of both the first and second synchronized scans along the first scanned line. The second section of the laser inspection apparatus reads information from a surface having an area illuminated by the dual beams of the optical scanner. The first and second synchronized scans from the optical scanner cause the illuminated area to emit radiation in the form of first and second modulated scans. Segmented radiation detection means includes first, second and sandwiched radiation detection means which each generated an electrical output signal representative of the detected radiation emitted by the first and second modulated scans. Signal processing means receives and selectively combines the electrical output signals from each of the three sections of the segmented radiation detection means in response to the beam position signal and generates first and second modulated output signals. The first modulated output signal is representative of the information residing within the area scanned by the first scan, while the second modulated signal is representative of the information residing within the area scanned by the second scan.

Claims35

Dependent claims

An optical scanner for repetitively scanning a first line with first and second angularly displaced synchronized scans comprising:

a. a light source for generating an input beam;
b. means for receiving the input beam and generating first and second angularly displaced beams lying in first and second non-parallel planes;
c. a polygon mirror scanner for receiving the first and second beams on a single facet and for generating first and second angularly displaced, non-parallel synchronized scans;
d. facet to axis error correction means including
a first cylindrical lens positioned in the optical path prior to said scanner;
ii. a second cylindrical lens positioned in the optical path between said scanner and the scanned line for reconverging the first and second synchronized scans onto the first scanned line;
redirecting means positioned in the optical path between said scanner and said second cylindrical lens for redirecting a portion of the first and second synchronized scans onto a timing plane to generate third and fourth non-coincident synchronized scans;
and
f. means for generating a beam position signal consisting of equally spaced, sequential pulses in response to the travel of the third or fourth synchronized scan along a second scanned line within the timing plane;
whereby the beam position signal is representative of the position of both the first and second synchronized scans along the first scanned line.

7 more elements

Apparatus for reading information from a surface having an area illuminated by an optical scanner repetitively generating first and second angularly displaced, synchronized scans and a beam position signal representative of the position of the first and second scans where the first and second scans cause the area to emit radiation in the form of first and second modulated scans, said apparatus comprising:

a. segmented radiation collection means for receiving the first and second modulated scans, including
i. sandwiched radiation detection means having first and second boundaries and being positioned to collect radiation alternately emitted by the first and second modulated scans within a beam overlap zone defined by the beginning of the second modulated scan and by the end of the first modulated scan and for generating an electrical output signal representative of the first and second modulated scans within the beam overlap zone;
ii. first radiation detection means having a third boundary positioned to collect radiation emitted by the first modulated scan from the beginning of the scan and a fourth boundary positioned adjacent to the first boundary of the sandwiched radiation detection means, wherein the first radiation detection means generates an electrical output signal representative of the first modulated scan as it moves between the third and fourth boundaries;
iii. second radiation detection means having a fifth boundary positioned adjacent to the second boundary of said sandwiched radiation detection means and a sixth boundary positioned to collect radiation emitted by the second modulated scan at the end of the scan, wherein said second radiation detection means generates an electrical output signal representative of the second modulated scan as it moves between the fifth and sixth boundaries;
and
b. signal processing means for receiving the electrical output signals from said first and second radiation detection means and from said sandwiched radiation detection means and for selectively combining said signals in response to the beam position signal to generate first and second modulated output signals, wherein the first modulated output signal is representative of the information residing within the area scanned by the first scan and wherein the second modulated signal is representative of the information residing within the area scanned by the second scan.

3 more elements

Dependencies are inferred from the claim text.

Dual beam laser inspection apparatus

Life of this patent

Dual beam laser inspection apparatus

Life of this patent

Abstract

Claims35