EMVA1288 Test

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The ACC systems conduct all measurements required by the newest release of the EMVA 1288 standard.

The systems do not measure temperature dependency of the dark current and spectral dependency of the quantum efficiency. By the standard, these measurements are optional because they require special equipment that would increase the effort considerably.

A Linearity, noise, and sensitivity

According to the standard, these measurements are performed with monochromatic green light for monochrome cameras and with blue, red, and green light for color cameras at 10 irradiances at least and at darkness.

B Spatial non-uniformities

With only a few illumination steps, mean and variance of each individual pixel are computed by averaging at least 100 images. With these data it is possible to analyze the spatial non-uniformities of the dark image and of the sensitivity of the sensor.

C Dark current

Dark current is determined by taking many images at different exposure times without any illumination.

Derived quantities and data sheet

From these measurements, the following parameters are derived:

Absolute gain factor

Absolute sensitivity threshold and saturation capacity

Maximal signal-to-noise ratio (SNRsat)

Dark noise

Dynamic range (DR)

Non-linearity

Spatial inhomogeneity of the dark image (dark signal non-uniformity, DSNU) and of the sensitivity (photo­response non-uniformity, PRNU)

Quantum efficiency at up to three or – dependent on the ACC model – four wavelengths (blue, green, red, and IR at 850 nm)

Measurement results are provided as diagrams in PDF format and as tables in CSV format. Images of the DSNU and PRNU are provided in PNG format. All essential intermediate results are stored for repeated evaluation. Data can be used to automatically generate a data sheet conforming to the standard.

The ACC is a modular optical system, which is described in more detail in the following. Please refer also to the table above.

The optical system consists of a tube system with interchangeable optical components including a homogeneous light source and a standard camera mount such as a Nikon F-mount, a C-mount or an M72. (From the camera's point of view, the ACC mount looks like a lense mount.) The length of the tube is determined by the diameter of the light source, as determined by the standard. The system is light-proof; no need for dim-out of light.

All light sources are current-controlled LEDs. Current is controlled digitally with 12-bit resolution. The irradiance of the image sensor can be varied either by changing the LED current at constant exposure time or by changing the exposure time of the camera at constant LED current or by using the pulse mode of the light source. The first two methods make measurements simple because it is not necessary to trigger the camera or the light source. The camera just needs to be connected to the computer for grabbing images.

The whole system is controlled by a computer via a single USB connection.

Specification:

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