A Practical Guide to Spectral Response and QE in Industrial Cameras 1. How to Read an Industrial Camera Spectral Response Curve A spectral response chart typically consists of two axes: X-axis: Wavelength Unit: nanometers (nm) Visible light range: approximately from violet to red (about 400–700 nm)

1. How to Read an Industrial Camera Spectral Response Curve

A spectral response chart typically consists of two axes:

X-axis: Wavelength

Unit: nanometers (nm)

from violet to red (about 400–700 nm)

Invisible light:

Below the visible range → Ultraviolet (UV)

Above the visible range → Near-Infrared (NIR)

Y-axis: Response Intensity

Quantum Efficiency (QE): the ratio of photons converted into electrons (0%–100%)

The higher the QE, the higher the photoelectric conversion efficiency and the better the low-light performance

MV-GE231GM(Monochrome (Black & White) )	MV-GE231GC(Color Cameras)
MV-GEC130I(short-wave infrared)	MV-SUC405U(UV)

Monochrome (Black & White) vs. Color Cameras

Monochrome Cameras

Usually feature a single smooth response curve

Achieve peak sensitivity within the visible spectrum

Maintain a certain level of sensitivity in the near-infrared range (>700 nm)

Color Cameras

Display three overlapping curves: Red, Green, and Blue

The overlap between these curves (crosstalk) directly determines the camera’s color reproduction accuracy

2. What Is the Practical Value of Spectral Response Curves in Camera Selection?

The spectral response curve directly determines whether an industrial camera can “see” the target clearly and how accurately it can capture information.

A. Matching the Light Source to Improve Image Contrast

This is the most critical factor in camera selection.

Example:
If infrared illumination is used for covert surveillance or material penetration inspection, the industrial camera must maintain a sufficiently high QE value in that wavelength range.

Selection logic:
Check whether the center wavelength of the light source falls within the camera sensor’s peak response region.
If the sensor is insensitive at that wavelength, the image will be noisy or even completely dark.

B. Detecting Special Materials Beyond Human Vision

Many objects that appear identical under visible light show significant differences at specific wavelengths.

Moisture detection: Water exhibits strong absorption at certain wavelengths and distinct characteristics in the near-infrared range.

Agricultural sorting: Rotten apple skin shows noticeable reflectance changes at specific NIR wavelengths compared to healthy fruit.

Selection logic:
Choose an industrial camera with the highest spectral sensitivity in the wavelength range where the target material exhibits the strongest contrast.

C. Evaluating Color Reproduction (Color Cameras)

Degree of overlap: Less overlap among RGB curves generally results in higher color purity, though overall sensitivity may decrease.

Color rendering accuracy: In industries such as textiles and printing, the spectral response curve should be compared with the CIE standard observer curves to ensure measured colors match human visual perception.

D. Optical Filter Selection

Spectral response curves help determine whether additional optical filters are required:

IR-Cut Filter:
If a color camera is highly sensitive to infrared light and used under outdoor daylight conditions, the absence of an IR-cut filter may cause color distortion (grayish or purplish tones).

Narrowband Filters:
In environments with strong ambient light interference, selecting a narrowband filter matched to the sensor’s peak response wavelength can significantly improve the signal-to-noise ratio.

Summary: A Three-Step Guide to Industrial Camera Selection Using Spectral Response Curves

1.Define the target:
Are you imaging visible light or invisible wavelengths (UV / NIR)?

2.Align with the illumination:
Review the camera’s QE curve and ensure efficiency at the illumination wavelength is ideally above 30%–50%.

3.Consider the environment:
If infrared interference is strong, use the spectral response curve to determine whether an IR-cut filter is required or select a NIR-enhanced industrial camera.