Characterizing an image sensor is a crucial first step in selecting a camera for machine vision applications, but it can be complex and requires careful consideration. Fortunately, resources like specialized courses offer excellent guidance. For instance, CEI provides practical training on this topic. You might also reach out to Adimec—we’ve conducted thorough evaluations of numerous sensors used across our cameras to ensure optimal performance.

To further explore the subject, here’s an overview of key measurements involved in characterizing image sensors:

Measurements Without Light (Dark Conditions)

Even without light input, several critical sensor parameters can be measured. Since photodiodes collect charges regardless of their source—whether from photons or structural leakage—their accumulated charge provides valuable characterization data.

Through dedicated dark measurements, the following metrics are evaluated:

  • Dark Current Density: The rate at which unwanted charges accumulate in the absence of light.
  • Dark-current Non-uniformities: Variations in dark current across different sensor pixels.
  • Linearity: How accurately the sensor outputs proportional signals to charge levels.
  • Conversion Gain: The efficiency with which the sensor converts incoming photons into electrical signals.
  • Dark Reference Lines/Pixels: Used for calibrating and compensating sensor noise or defects.
  • Leaking Pixels: Identifies pixels that lose accumulated charge over time.
  • Temporal Noise: Measures fluctuations in signal output over short periods.
  • Dynamic Range: The ratio between the brightest and dimmest signals the sensor can capture.

Measurements With Light

Image sensors are primarily designed to convert incoming photons into measurable electrical outputs. Therefore, evaluating light-dependent characteristics is equally vital. Parameters measured when light interacts with the sensor include:

  • Light Sensitivity: How effectively the sensor responds to different light intensities.
  • Light Non-uniformities: Variations in sensitivity across the sensor array.
  • Linearity (light): The accuracy of output signals under varying illumination levels.
  • Conversion Gain (light): Measures how faithfully photons are converted into electrical charges.
  • Blooming Characteristics: How well the sensor handles high-light conditions without overflow or distortion.
  • Black Sun: Evaluates image artifacts caused by stray light reflections.
  • Green-Green Differences: Assesses color uniformity across different wavelengths of visible light.
  • Reciprocity Effect: The deviation from expected linearity under extreme exposure variations (e.g., very bright vs. dim light).
  • Saturation Level: The maximum signal output before the sensor becomes overloaded.

During this course, participants are divided into subgroups to work on distinct setups—though not all measurements may be identical across groups. However, everyone receives a comprehensive summary of all characterization results at the end.

Last Updated: 2025-09-04 18:47:13