Laser detector and spectral analyzer

• US 4,346,992 A
• Filed: 02/15/1973
• Issued: 08/31/1982
• Est. Priority Date: 02/07/1969
• Status: Expired due to Term

• Current Assignee: Sanders Associates, INC. (BAE Systems Plc)
• Original Assignee: Sanders Associates, INC. (BAE Systems Plc)
• Inventors: Schwartz, Jacob
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US05/332,827
• Time in Patent Office: 3,484 Days
• Field of Search: 356/77, 356/98, 356/195, 356/310, 356/303, 356/326, 356/73, 356/419, 356/223, 356/227, 250/237 R
• US Class Current: 356/73
• CPC Class Codes: G01J 3/12 Generating the spectrum; Monochromators

Abstract

There is herein disclosed a laser detector and spectral analyzer comprising a plurality of photoelectric detector elements, at least, two of which are suitably masked and disposed behind a wedge type interference filter. An additional detector element is operated without any mask or filter. The detector output signals are electronically processed to provide a substantially instantaneous and independent indication of the mean spectral wavelength, spectral width, total power and pulse length of radiant energy incident upon the apparatus.

Claims

1. Apparatus for the detection and spectral analysis of radiant light energy comprising:

a wedge filter having a predetermined variation in optical passband which is dependent upon the position thereon;

photoelectric detection means disposed behind said filter and responsive to energy transmitted thereby to produce a first output signal which increases linearly with the position at which energy is transmitted by said filter and a second output signal which increases quadratically with said position; and

signal processing means coupled to said detection means for combining said output signals such as to provide outputs representative of selected spectral properties of said energy.

2. Apparatus as recited in claim 1 wherein:

said wedge filter passband varies with position along a longitudinal axis thereof; and

said detection means comprises a first photoelectric detector element having an aperture mask on the radiation incident side thereof which increases linearly with longitudinal position, and a second photoelectric detector element having an aperture mask on the rediation incident side thereof which increases quadratically with longitudinal position.

3. Apparatus as recited in claim 2 further including:

a third photoelectric detector element disposed such as to be fully exposed to radiation transmitted by said filter and producing a third output signal representative of the amount of energy incident thereon.

4. Apparatus as recited in claim 3 further including:

means coupled to said third detector for including the power of radiation incident thereon.

5. Apparatus as recited in claim 4 wherein:

said third output signal is applied to said power indicating means through a peak and hold circuit.

6. Apparatus as recited in claim 3 wherein said signal processing means includes:

first divider means for dividing said first output signal by said third output signal to thereby provide a signal representative of the longitudinal position at which said energy is transmitted by said filter and thus representative of the wavelength of said energy.

7. Apparatus as recited in claim 3 further including:

means coupled to said first dividing means for indicating the wavelength of said energy.

8. Apparatus as recited in claim 6 wherein said signal processing means further includes:

second divider means for dividing said second output signal by said third output signal,

means for squaring the output signal from said first divider, and

means coupled to said second divider means and said squaring means for subtracting said squaring means output signal from said second divider output signal to produce a signal representative of the square of the bandwidth of said energy.

9. Apparatus as recited in claim 8 further including:

means coupled to said subtracting means for indicating the square of the bandwidth of said energy.

10. Apparatus as recited in claim 1 further including:

a cone channel optical element disposed on the light incident side of said filter whereby the field-of-view of said apparatus is limited to a preselected value.

11. Apparatus as recited in claim 1 further including:

a diffusing screen disposed adjacent said filter and receiving an image of said energy transmitted by said filter, and

means for imaging said diffusing screen upon said photoelectric detection means.