Machine vision illumination unit

01

Choose the lighting geometry for the surface

Advanced Illumination separates system geometry, the placement of camera, light and part, from light-ray geometry, how light reaches and leaves the surface. On-axis lights, centred on the camera's optical axis, include dome, tunnel, flat diffuse, ring and true coaxial lights. A diffuse dome lights the part “from a broad range of directions and angles”, giving soft, even lighting with few shadows, and suits curved and highly reflective surfaces but must sit close to the part. [1]

A flat diffuse light sits between dome and coaxial: it can work at longer distances over larger areas and suits code reading on flat surfaces and PCB inspection, but is less suited than a dome to highly curved reflective parts. True coaxial lighting uses a beam splitter so light travels the camera's own optical path; flat reflective surfaces appear bright and engravings, textures or defects appear dark, which suits polished metal, laser markings and flat-surface defects. [1]

Ring lights mount around the lens and reach the part at an angle set by ring diameter, LED optics and working distance; at direct angles they give bright-field lighting for matte surfaces, and at low angles dark-field lighting where only scratches, edges and irregularities reflect into the camera. Backlights, standard or collimated, light the part from behind for dimensional inspection, hole detection, liquid level and translucent glass or plastic; combined with monochromatic light and collimation film they give sharper edges for precise measurement. [1]

Give the supplier the part material, colour and surface finish, the feature to detect, field of view, working distance, camera and lens, space around the part, line speed and exposure time, ambient light, environment and mounting, and the controller or trigger interface.

02

Choose the wavelength and drive mode

Advanced Illumination notes that an object's colour is the wavelength it reflects, so complementary-colour light raises contrast even for monochrome cameras; shorter wavelengths such as blue enhance scattering for small surface defects, while near-infrared can penetrate translucent materials and some plastics. Its bottle fill-level example compares backlighting at 660 nm red, 880 nm infrared and 470 nm blue. For UV-excited fluorescence, filters must block the excitation light. [2]

Advanced Illumination explains that with short exposure times and a low duty cycle, an LED can be overdrive-strobed at 10 or more times its nominal constant rated current, with pulse widths from about one microsecond to a few milliseconds, raising output during the pulse while limiting heat at the LED junction and protecting filters or polariser films from continuous light. [3]

Nanjing Hecho lists LED ring lights for machine vision using 1–3 W high-power LEDs for surface inspection and OCR on integrated circuits, and a light controller giving stepless intensity control, short-circuit protection and constant-current drive. [6] [7]

Editorial calculation: 470, 660 and 880 nm span blue, red and near-infrared; photon energy is inversely proportional to wavelength, so a 470 nm photon carries about 1.9 times the energy of an 880 nm photon (880 ÷ 470 ≈ 1.87). [2] [4]

03

Compare what suppliers offer

The supplier linked to this page lists machine vision lights and controllers; its card links to the page reviewed.

Ask any supplier for the light type and size, LED wavelength and spectral data, irradiance or intensity at your working distance, uniformity over the field, supply voltage and current, continuous and strobe ratings, controller and trigger options, cable and connector, housing and ingress rating, and operating temperature.

04

Trace what each part does

This is a functional reference built from the sources cited; it is not one maker's specification.

05

Fill the specification fields with values for your order

An illumination unit quotation needs values for your inspection. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the part, feature and camera data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Part: [material; colour; finish]
Feature: [defect; code; edge; fill level]
Geometry: [dome; flat diffuse; coaxial; ring; dark-field; backlight]
Wavelength: [white; 470; 660; 880 nm; UV]
Drive: [continuous; strobe; overdrive; trigger]
Optics: [camera; lens; working distance; field of view]

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