Telecentric laser beam optical focusing system of two diffractive optical elements

• US 5,914,814 A
• Filed: 06/26/1997
• Issued: 06/22/1999
• Est. Priority Date: 06/26/1997
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Ang, Anthony
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US08/882,976
• Time in Patent Office: 726 Days
• Field of Search: 359/565, 359/569, 359/663, 359/16, 359/19
• US Class Current: 359/565
• CPC Class Codes: G02B 27/4216 correcting geometrical aberrations

Abstract

A telecentric laser beam optical focusing system consists of two diffractive optical elements. The optical system has a spot size of less than one micron and a Strehl ratio of over 0.9 with a f/number of one and a total object/image field of 0.5 micron.

Claims

1. A telecentric optical focusing system comprising

a laser light source for emitting a light beam of a single wavelength,

a first diffractive optical element for diffracting said light beam, said first diffractive optical element being circularly symmetric,

a second diffractive optical element, said second diffractive optical element being circularly symmetric, for diffracting said light beam from said first diffractive optical element to a spot,

wherein the object field of said telecentric optical focusing system is 0.5 millimeters and the image field of said telecentric optical focusing system is 0.5 millimeters and wherein said spot size is less than one micron and said telecentric optical focusing system has a Strehl ratio of over 0.9.

2. The telecentric optical focusing system of claim 1 wherein the first diffractive optical element has a first surface with a diffractive phase profile and a second surface with a diffractive phase profile and wherein the second diffractive optical element has a first surface with a diffractive phase profile and a second surface with a diffractive phase profile, further wherein each of the diffractive phase profiles, Φ

, with regard to a position, ρ

, on the surface is defined by

space="preserve" listing-type="equation">Φ

(ρ

)=c.sub.1 ρ

.sup.2 +c.sub.2 ρ

.sup.4 +c.sub.3 ρ

.sup.6 +c.sup.4 ρ

.sup.8 +c.sub.5 ρ

.sup.10

where c_x are the polynomial coefficients.

3. The telecentric optical focusing system of claim 2 wherein the polynomial coefficients of the diffractive phase profile of the first surface of the first diffractive optical element are