Color lighting

ILLUMINATION SOLUTIONS

Complementary color

Detection using complementary colors

The contrast between the red candy wrapper and the carton is compared with white, red, or blue LED light.

With white LED Contrast is not clear as objects have homogeneous brightness.

With red LED The red object is slightly brighter than the carton.

With blue LED The red object appears darker than the carton and detection can be stably carried out.

Hue circle

The contrast of the image is produced by the complementary colors of the illumination to the candy wrapper.

CCD camera sensitivity

CCD sensitivity is close to that of the human eye and detects in the vicinity of 500nm with highest sensitivity. So, the sensitivity is better with blue light than with red light. Also, a brighter image can be captured with blue light than with red light. This is why blue light is suitable to capture a bright image with a high-speed shutter and large depth of field.

Blue 460nm/spectral sensitivity approx 90%
Red 660nm/spectral sensitivity approx 60%
Blue light is 1.5 times brighter than red light.

Scattering rate

Blue light from an angle Stain area 2749

Red light from an angle Stain area 786

Installation

To obtain a clear contrast with LED illumination, the scattering rate can be used along with color relation (complementary/similar colors). Blue light has a short wavelength and a high scattering rate. In contrast, red light has a long wavelength, low scattering rate and a high transmission. Light with a high scattering rate is effective to detect surface conditions as shown in the pictures.

Contrast between gold and silver colors

To obtain a clear contrast between gold and silver colors, blue illumination is more efficient than red illumination as blue is a complementary color to gold.

With color camera

With color camera and red light

With color camera and blue light

With monochrome camera and red light

With monochrome camera and blue light

Characters on a chip carrier tape

Inspecting characters printed on a chip through a film. Since red has higher transmission (low scattering rate) than blue, red illumination produces clear contrast.

With color camera

With color camera and red light

With color camera and blue light

With monochrome camera and red light clear contrast is created through the film.

With monochrome camera and blue light less contrast is created.