EMCCD Automatic Gain Calibration via Dark Charge
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Solution Overview
Problem
Electron multiplying Charge Coupled Devices (EMCCDs) face challenges in automatic recalibration due to the 'ageing effect,' which reduces EM gain over time, requiring skilled intervention and external hardware, making it difficult for users to maintain optimal performance without factory recalibrations.
Innovation Solution
A method and apparatus for determining and adjusting the EM gain using test signals derived from dark charge or clock-induced charge, allowing for automatic recalibration without external stabilised light sources or skilled intervention, by increasing darkcurrent or CIC through control signal manipulation and analyzing output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory recalibration is performed to maintain EM gain, then measurement precision is improved, but loss of time and productivity deteriorate due to requiring skilled intervention and external hardware
Solution Approach 1:
The EMCCD device performs self-calibration by using its own dark charge or clock-induced charge as test signals, eliminating the need for external calibration equipment and skilled operators. The system automatically determines EM gain by processing these internally generated signals through the electron multiplying register and comparing outputs with and without EM gain enabled.
Solution Approach 2:
The dark charge and clock-induced charge, which are normally considered unwanted artifacts, are repurposed as useful test signals for calibration. This multi-functional use of existing charge sources eliminates the need for separate external calibration hardware and light sources.
2Measurement precision
If factory recalibration with external hardware is used, then measurement precision is improved, but device complexity increases due to requiring external stabilised light sources
Solution Approach 1:
The calibration function is extracted from external equipment and integrated into the EMCCD device itself. The device uses its own internally generated dark charge and clock-induced charge as test signals, removing the dependency on external stabilised light sources and calibration hardware.
Solution Approach 2:
The dark charge and clock-induced charge serve as intermediaries that enable calibration without requiring external light sources. These internally generated charges mediate the measurement process by providing test signals that pass through the electron multiplying register for gain determination.
3Measurement precision
If darkcurrent or CIC is increased for calibration, then measurement precision is improved, but object-generated harmful factors worsen due to increased noise signal
Solution Approach 1:
The dark current and clock-induced charge, which are normally harmful noise sources, are converted into beneficial test signals for calibration. By intentionally increasing these signals during calibration mode, the system obtains sufficient test data for accurate EM gain determination while the same signals would otherwise be considered unwanted artifacts.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate and efficient recalibration of EMCCDs, maintaining device performance over time without the need for external equipment or user expertise, facilitating continuous operation in various applications.
Implementation Method 1
The structure normally comprises a solid state electron multiplier and is commonly referred to as the EM gain register or Charge Multiplication Register
Implementation Method 2
photons impinge upon the cells 14 in the image area 16, each cell 14 generating one or more electrons, i.e. a quantity of electrical charge, (by means of photo-generated electron-hole pairs the photoelectric effect)
Data Source
AI summary
A method of determining the gain of an electron multiplier, especially in an Electron Multiplying Charge Coupled Device (EMCCD). The electron multiplier multiplies, in use, signals received from a device, typically a CCD, comprising photodetectors. A test signal is input to the electron multiplier from the device, and the gain of the electron multiplier is determined from the output of the electron multiplier. The test signal comprises, or is derived from, electrical charge generated by the photodetectors other than as a result of the incidence of an electromagnetic signal on the photodetectors. The test signal comprises, or is derived from, dark current, or clock induced charge.