Dark Current Compensation

Sensor Baseline

Silicon detectors in spectrophotometers produce a small electrical current even when the shutter is closed. This unwanted signal increases with sensor temperature and exposure time, simulating a light response. By measuring this dark current when no light hits the sensor, the instrument establishes a zero-point baseline for subsequent scans.

Measurement Accuracy

Color measurement of deeply dyed cotton or polyester fabric requires high sensitivity in low-reflectance regions. Uncorrected thermal noise falsely elevates the measured reflectance, leading to incorrect dye concentration calculations. Executing the adjustment before each measurement ensures that the recorded values represent only the light reflected from the fabric surface.

Spectral Boundary

The effectiveness of the adjustment diminishes if the sensor temperature shifts rapidly after the calibration phase. In dye houses with fluctuating room temperatures, the spectrophotometer must perform this subtraction frequently to maintain calibration integrity. High-precision color control requires a stable environment to minimize baseline drift.