CN111988546B - Method for measuring multiplication gain and readout noise of multiplication CCD - Google Patents

Abstract

The invention provides a method for measuring multiplication gain and read noise of a multiplication CCD (charge coupled device). The method comprises the steps of carrying out linear segment internal exposure on the EMCCD under flat field light, calculating the variance and mean value of image gray signals obtained after exposure, carrying out straight line fitting and calculating the slope through multiple groups of data, and simultaneously reading out noise expression intercept; and according to the given functional equation:

and calculating the multiplication gain of the EMCCD to obtain a multiplication result. The invention provides a stable measurement method based on line fitting under exposure data in multiple groups of EMCCD linear segments, which is stable and effective.

Description

Method for measuring multiplication gain and readout noise of multiplication CCD

Technical Field

The invention relates to a method for measuring multiplication gain and read-out noise of a multiplication CCD (charge coupled device), belonging to the technical field of electronic component testing.

Background

The EMCCD, electron multiplying CCD, is a high-end photoelectric detection product with extremely high sensitivity in the detection field. With the rapid development of the EMCCD, the EMCCD has been widely used in the fields of military, astronomy, etc., and gradually penetrated into the aspects required by people's daily life. The EMCCD has high quantum efficiency and strong detection efficiency on low-light-level images, and is an all-solid-state electron multiplier. The novel high-power LED driving circuit has the advantages of low manufacturing cost, long service life and high stability, and the multiplication gain is adjustable, so that the novel high-power LED driving circuit can meet the application requirements of all-weather and large dynamic range. In the identification test, the problems of large deviation of test results, poor stability and the like of the conventional gain test method of the EMCCD exist, the conventional method needs to be improved aiming at the corresponding problems, and the test method with higher precision and higher stability is designed.

Disclosure of Invention

The invention provides a multiplication CCD multiplication gain and a reading noise measuring method for obtaining more accurate multiplication gain.

The purpose of the invention is realized by the following steps:

a method for measuring multiplication gain and readout noise of a multiplication CCD comprises the following steps:

s1: setting multiplication gain control register as x, and subjecting EMCCD to linear exposure of flat field light for exposure time t _exp Obtaining data of image gray signal, mu _out (t _exp )、

And collecting a plurality of groups of data;

s2: by the formula:

the sets of data (. Mu.) thus obtained _out (t _exp )，

) Fitting the data to obtain a straight line, and calculating to obtain slope A M of the straight line _x * F x F and intercept>

Wherein:

t _exp integration time in linear section (exposure) of EMCCD;

for EMCCD exposure t under flat field light _exp Variance of the image gray signal obtained after the time;

μ _out (t _exp ) For EMCCD exposure t under flat field light _exp Average value of the image gray level signal obtained after the time;

is and t _exp Extraneous readout noise;

a is the system gain of the EMCCD when the multiplication gain is equal to 1;

M _x controlling EMCCD multiplication gain when the register is x for multiplication gain;

s3: from the slope A M of the resulting line _x * F × F, from the functional equation:

/>

and calculating the current read noise of the EMCCD when the multiplication gain is equal to 1

And a multiplication gain M _x 。

Compared with the prior art, the invention has the beneficial effects that:

compared with the existing method, the EMCCD multiplication gain measurement method based on multiple groups of data can obtain more accurate multiplication gain, is suitable for engineering application, and is stable and reliable.

Drawings

FIG. 1 is a flow chart of the measurement of the present invention;

FIG. 2 is an EMCCD information flow diagram;

FIG. 3 is a schematic diagram of straight line fitting of multiple sets of data of flat field light image gray signals.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Different from the commonly adopted two-point multiplication gain calculation method at present, the method carries out linear fitting and slope calculation on multiple groups of gray scale data exposed by a multiplication CCD (EMCCD) image sensor under flat field light, and reads out noise expression intercept at the same time, thereby calculating the EMCCD multiplication gain.

The imaging area, the storage area and the read-out register of the EMCCD are all the same as the structure of the traditional frame transfer CCD, but a series of gain register structures are added between the read-out register and the output amplifier. Based on the structure and the working mode of the EMCCD, an information flow diagram (figure II) of the EMCCD is given, wherein the system gain K comprises multiplication gain and output amplifier gain of the EMCCD. Through literature research and mathematical modeling, the following photoelectric conversion formula can be established by fully utilizing the existing research and experimental conclusions:

wherein:

t _exp integration time of the EMCCD in the flat field light linear section (exposure);

for EMCCD exposure t under flat field light _exp Variance of the image gray level signal obtained after the time;

μ _out (t _exp ) For EMCCD exposure t under flat field light _exp Average value of the image gray signal obtained after the time;

is given as _exp Extraneous readout noise;

a is the system gain of the EMCCD when the multiplication gain is equal to 1;

M _x controlling EMCCD multiplication gain when the register is x for multiplication gain;

f is the multiplied noise factor of the EMCCD device.

The measuring method is realized as follows:

s1: setting multiplication gain control register as x, and subjecting EMCCD to linear exposure of flat field light for exposure time t _exp Obtaining data of image gray signal, mu _out (t _exp )、

And a plurality of groups of data acquisition are carried out,

s2: by the formula:

/>

from the obtained sets of data (. Mu.) _out (t _exp )，

) Fitting the data to obtain a straight line, and calculating to obtain slope A M of the straight line _x * F x F and intercept>

Wherein:

t _exp integration time within the linear segment of the EMCCD (exposure);

for EMCCD exposure t under flat field light _exp Variance of the image gray signal obtained after the time;

μ _out (t _exp ) For EMCCD exposure t under flat field light _exp Average value of the image gray signal obtained after the time;

is given as _exp Extraneous readout noise;

a is the system gain of the EMCCD when the multiplication gain is equal to 1;

M _x to multiply the EMCCD multiplication gain with the gain control register at x,

s3: according to the slope A M of the obtained straight line _x * F × F, from the functional equation:

and calculating the current read noise of the EMCCD when the multiplication gain is equal to 1

And a multiplication gain M _x 。

Setting the multiplication gain control register as x, and the exposure time t of EMCCD under the linear exposure of flat field light _exp And carrying out multi-group data acquisition to obtain a group of mean values mu of image gray signals _out (t _exp ) Variance, variance

By the formula:

from the obtained data

μ _out (t _exp ) Fitting multiple sets of data to a straight line (mu) _out (t _exp )，/>

) And calculating the slope A M of the straight line _x * F, and according to the slope A M of the obtained straight line _x * F × F, from the functional equation:

and calculating the current read noise of the EMCCD when the multiplication gain is equal to 1

And a multiplication gain M _x 。

In conclusion:

the invention belongs to the technical field of electronic component testing, and particularly relates to a method for calculating multiplication gain of an Electron Multiplying Charge Coupled Device (EMCCD) through multiple groups of gray scale data of an EMCCD image sensor exposed under flat field light. The invention comprises the following steps: carrying out linear segment internal exposure on the EMCCD under flat field light, calculating the variance and mean value of an image gray signal obtained after exposure, carrying out straight line fitting through multiple groups of data, calculating the slope, simultaneously reading out the noise expression intercept, and according to a given function equation:

and calculating the multiplication gain of the EMCCD to obtain a multiplication result. The invention provides a stable measurement method based on line fitting under exposure data in multiple groups of EMCCD linear segments, which is stable and effective.

Claims (1)

1. A method for measuring multiplication gain and readout noise of a multiplication CCD is characterized by comprising the following steps:

s1: setting the multiplication gain control register as x, and the EMCCD exposing the flat field light for the exposure time t _exp Obtaining data of image gray signal, mu _out (t _exp )、

And collecting a plurality of groups of data;

s2: by the formula:

the multiple sets of data thus obtained

Fitting the data to obtain a straight line, and calculating to obtain the slope A M of the straight line _x * F x F and intercept>

Wherein:

t _exp the exposure integration time in the linear section of the EMCCD is defined;

for EMCCD exposure t under flat field light _exp Variance of the image gray signal obtained after the time;

μ _out (t _exp ) For EMCCD exposure t under flat field light _exp Average value of the image gray signal obtained after the time;

is given as _exp Extraneous readout noise;

a is the system gain of the EMCCD when the multiplication gain is equal to 1;

M _x controlling EMCCD multiplication gain when the register is x for multiplication gain;

f is the multiplication noise factor of the EMCCD device;

s3: according to the slope A M of the obtained straight line _x * F × F, from the functional equation:

and calculating the current read noise of the EMCCD when the multiplication gain is equal to 1

And a multiplication gain M _x 。/>

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