Self-scanned photodiode array with selectively-skipped pixels

1. A device having a self-scanned photodiode array wherein charge from individual pixels is switched from each pixel sequentially onto at least one output video line after a predetermined exposure time (t 0 ) comprising:

at least one light source;

at least one sample cell having means for receiving light from said at least one light source;

a photo-diode array having pixels for collecting light transmitted through said at least one sample cell, wherein the intensity of said light may vary across the spatial extent of the array;

means for reading said pixels;

means for skipping the reading of selected pixels for one or more additional exposure times t 0 allowing said selected pixels to be exposed for specified integer multiples (M) of said predetermined exposure time t 0 , thereby allowing said selected pixels receiving less light to accumulate additional charge before being read out and thereby reducing the number of read cycles and improving the signal-to-noise ratio.

2. The self-scanned photodiode array of claim 1 wherein different pixels are exposed for the same or different integer multiples (M) of said predetermined exposure time.

3. The self-scanned photodiode array of claim 1 in which said predetermined exposure time t 0 does not exceed saturation of the pixel or pixels accumulating charge at a highest rate within a predetermined range of pixels.

4. The self-scanned photodiode array of claim 1 wherein specified integer multiples M are chosen such that each pixel signal, within a predetermined range of pixels approaches but does not exceed saturation.

5. The self-scanned photodiode array of claim 1 wherein said exposure time of individual pixels, Mt 0 , does not cause saturation of pixels from which charge is measured.

6. The self-scanned photodiode array of claim 1 wherein said exposure time of each pixel, is an integer multiple M of said predetermined exposure time t 0 , wherein the lowest value of M is greater than one.

7. The self-scanned photodiode array of claim 1 wherein a sample time is defined as a time taken for one or more complete measurements of the full or selected portion of the photodiode array, said individual pixel exposure times Mt 0 being submultiples of said sample time.

8. The self-scanned photodiode array of claim 1 wherein said predetermined exposure time t 0 is established when said photo-diode array receives said light according to a reference condition.

9. The self-scanned photodiode array of claim 3 wherein the predetermined range of pixels includes the full array.

10. The self-scanned photodiode array of claim 4 wherein the predetermined range of pixels includes the full array.

11. The self-scanned photodiode array of claim 1 wherein the value recorded when a pixel read is skipped is set to zero to avoid the addition of unnecessary read noise.

12. A method of improving signal to noise ratio of measurements made using a self-scanned photodiode array to detect light in the ultraviolet, visible and infrared portions of a light spectrum comprising the steps of:

exposing pixels of said photodiode array to light received from a reference condition and measuring the spectrum of a short exposure time causing no saturation of said pixels;

measuring a dark spectrum of said pixels with shutter closed using said short exposure time;

calculating a dark corrected reference signal from each pixel;

calculating an exposure time for each pixel such that its accumulated charge would reach a predetermined level, close to but below saturation;

establishing a predetermined exposure time t 0 , short enough that no pixel in a specified range of interest will saturate;

assigning integers M such that individual pixels are exposed for integer multiples of the predetermined exposure time Mt 0 , such that after time Mt 0 said individual pixels have accumulated charge close to but not exceeding saturation;

re-measuring dark spectrum with shutter closed using exposure pattern determined by integers;

re-measuring reference spectrum using exposure pattern determined by integers, thereby creating a dark-corrected reference spectrum;

Measuring sample spectra using the same exposure pattern determined by integers and creating dark corrected sample spectra;

combining reference and sample spectra to determine absorption characteristics of sample and thereby identify and quantitate same with improved signal-to-noise ratio.

13. A self-scanned photodiode array wherein charge from individual pixels is switched from each pixel sequentially onto at least one output video line after a predetermined exposure time (t 0 ) comprising:

an array of photodiode pixels for collecting light, wherein the intensity of said light may vary across the spatial extent of the array;

means for reading said pixels;

means for skipping the reading of selected pixels for one or more additional exposure times t 0 allowing said selected pixels to be exposed for specified integer multiples (M) of said predetermined exposure time t 0 , thereby allowing said selected pixels receiving less light to accumulate additional charge before being read out and thereby reducing the number of read cycles and improving the signal-to-noise ratio of the measured light.