Multipass cavity for illumination and excitation of moving objects

A beam detection system for use with an illumination system, to enable detection of beam misalignment in four degrees of freedom, comprising:

• (a) a first optical element disposed in an illumination system light path, said illumination system light path originating in said illumination system, such that a front focal plane of said first optical element is disposed facing an aperture of said illumination system;
• (b) a beam splitter disposed in said illumination system light path, said beam splitter receiving light from said illumination system that passes through said first optical element, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path;
• (c) a first position sensitive detector disposed in said first light path to receive said first beam, said first position sensitive detector determining an angular error associated with said illumination system light beam;
• (d) a second optical element disposed in said second light path, such that a front focal plane of said second optical element is disposed facing said aperture;
• and
• (e) a second position sensitive detector disposed in said second light path to receive said second beam, such that a rear focal plane of said second optical element is disposed facing said second position detector, said second position sensitive detector determining a positional error associated with said illumination system light beam.

A beam detection and alignment system for use with an illumination system, to enable detection and correction of beam misalignment at an aperture of said illumination system, comprising:

• (a) a first independently adjustable reflective element disposed in an illumination system light path, said first independently adjustable reflective element selectively redirecting said illumination system light path, thereby adjusting a beam angle at said aperture;
• (b) a second independently adjustable reflective element disposed in said illumination system light path, said second independently adjustable reflective element selectively redirecting said illumination system light path, thereby adjusting a beam position at said aperture;
• (c) a first beam splitter disposed in said illumination system light path, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path, said second light path being directed at said aperture;
• (d) a second beam splitter disposed in said first light path, said second beam splitter separating an illumination system light beam traveling along said first light path into a first detection beam that is directed along a first detection light path and a second detection beam that is directed along a second detection light path;
• (e) a first position sensitive detector disposed in said first detection light path to receive said first detection beam, said first position sensitive detector determining an angular error associated with said illumination system light beam;
• and
• (f) a second position sensitive detector disposed in said second detection light path to receive said second detection beam;
• said second position sensitive detector determining at positional error associated with said illumination system light beam.

A beam detection and alignment system for use with an illumination system, to enable detection and correction of beam misalignment at an aperture of said detection illumination system, comprising:

• (a) a first independently adjustable reflective element disposed in an illumination system light path, said first independently adjustable reflective element selectively modifying said illumination system light path by adjusting a beam angle at said aperture;
• (b) a second independently adjustable reflective element disposed in said illumination system light path, said second independently adjustable reflective element selectively modifying said illumination system light path by adjusting a beam position at said aperture;
• (c) a first alignment optical element disposed in said illumination system light path, between said first independently adjustable reflective element and said second independently adjustable reflective element, such that said aperture is imaged by said first optical element onto said first independently adjustable reflective element;
• (d) a second alignment optical element disposed in said illumination system light path, between said second independently adjustable reflective element and said aperture, such that said aperture is substantially collimated by said second optical element at said second independently adjustable reflective element;
• (e) a first beam splitter disposed in said illumination system light path, said first beam splitter separating said illumination system light beam into a first beam that is directed along a first light path and a second beam that is directed along a second light path, said second light path being directed at said aperture;
• (f) a second beam splitter disposed in said first light path, said second beam splitter separating said illumination system light beam into a first detection beam that is directed along a first detection light path and a second detection beam that is directed along a second detection light path;
• (g) a first detection optical element disposed in said first light path;
• (h) a second detection optical element disposed in said second detection light path, such that said second beam splitter is disposed between said first and second detection optical elements;
• (i) a first position sensitive detector disposed in said first detection light path to receive said first detection beam, said first position sensitive detector determining an angular error associated with said illumination system light beam;
• and
• (j) a second position sensitive detector disposed in said second detection light path to receive said second detection beam, said second position sensitive detector determining a positional error associated with said illumination system light beam.

A beam detection and alignment system for use with an illumination system, to enable detection and correction of beam misalignment at an aperture of said illumination system, comprising:

• (a) a first independently adjustable reflective element disposed in an illumination system light path, comprising a mechanical actuator operable to adjust a position of said first independently adjustable reflective element, thereby selectively modifying said illumination system light path, to adjust a beam angle at said aperture;
• (b) a second independently adjustable reflective element disposed in said illumination system light path, comprising a mechanical actuator operable to adjust a position of said second independently adjustable reflective element to selectively modify said illumination system light path, to adjust a beam position at said aperture;
• (c) a first beam splitter disposed in said an illumination system light path, said beam splitter separating an illumination system light beam traveling along the illumination system light path into a first beam that is directed along a first light path and a second beam that is directed along a second light path, said second light path being directed at said aperture;
• (d) a second beam splitter disposed in said first light path, said second beam splitter separating an illumination system light beam traveling along said first light path into a first detection beam that is directed along a first detection light path and a second detection beam that is directed along a second detection light path;
• (e) a first position sensitive detector disposed in said first detection light path to receive said first detection beam, said first position sensitive detector producing a signal indicative of an angular error associated with said illumination system light beam;
• (f) a second position sensitive detector disposed in said second detection light path to receive said second detection beam;
• said second position sensitive detector producing a signal indicative of a positional error associated with said illumination system light beam;
• and
• (g) a beam alignment processor electrically coupled to each of said first and second position sensitive detectors, and to each mechanical actuator, said beam alignment processor determining angular and positional correction factors based on the signals received from said first and second position sensitive detectors, and adjusting a position of each independently adjustable reflective element by activating said mechanical actuators to apply said angular and positional correction factors to reduce an error in said beam angle and said beam position relative to said aperture.

A method for detecting a positional beam misalignment and an angular beam misalignment relative to an aperture in an illumination system, comprising the steps of:

• (a) directing light from said aperture along a first light path;
• (b) diverting a portion of light traveling along said first light path to a second light path;
• (c) determining a positional error of the light traveling along the first light path relative to a central axis of said aperture;
• and
• (d) determining an angular error of the light traveling along the second light path relative to a central axis of said aperture.

A method for detecting a positional light path misalignment and an angular light path misalignment relative to an aperture in an illumination system, and correcting the misalignment, comprising the steps of:

• (a) directing light from the aperture along a first light path;
• (b) diverting a portion of light traveling along the first light path along a second light path;
• (c) determining a positional error of the light traveling along the first light path relative to a central axis of the aperture;
• (d) determining an angular error of the light traveling along the second light path relative to a central axis of said aperture;
• (e) if the angular misalignment is greater than a first predefined threshold, redirecting the light traveling from a source toward the aperture to correct the angular misalignment;
• and
• (f) if the positional misalignment is greater than a second predefined threshold, further redirecting the light that was redirected to correct the positional misalignment.

A method for detecting a positional misalignment and an angular misalignment of light traveling along a path relative to an aperture in an illumination system, and redirecting the light to correct the misalignment, comprising the steps of:

• (a) determining the magnitude of the angular misalignment relative to the aperture;
• (b) determining if the magnitude of the angular misalignment exceeds a predefined angular error limit;
• (c) if the magnitude of the angular misalignment exceeds the predefined angular error limit, determining and executing an adjustment necessary to correct the angular misalignment;
• (d) determining the magnitude of the positional misalignment relative to the aperture;
• (e) determining if the magnitude of the positional misalignment exceeds a predefined positional error limit;
• and
• (f) if the magnitude of the positional misalignment exceeds the predefined positional error limit, then determining and executing an adjustment necessary to correct the positional misalignment.