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Dome Lights for Machine Vision

Dome Lights for Machine Vision

Dome lights enable an even and homogeneous illumination of the object. They can be used to illuminate complex reflective objects by creating a diffuse lighting from all directions. Dome lights are based on the modular ring lights in combination with special dome accessories, thus offering a broad range of functionalities – manufactured by wenglor.

Illumination Methods Using Dome Lights

Dome Illumination

Dome lights distribute light homogeneously over the whole diameter. The modular ring light is directed upwards illuminating the inside of the dome surface. The light is then reflected and diffused from the surface down to the target.

LMDX Dome Light

LMDX dome lights are based on the LMRX modular ring light platform. The reflective dome accessories ZMRG001 and ZMRG002 turn the light source into a traditional “cloudy day illumination” where the light is homogeneously distributed over the whole diameter. This is an excellent tool for reading inkjet or laser markings on shiny, curved and/or uneven surfaces and inspecting areas inside of holes from a close working distance. The Machine Vision dome lights are bi-color available in infrared or white and red or cyan. 

Comparison of Different Brightfield Illuminations

What is the advantage when using dome illumination instead of ring illumination?

A dome light is usually mounted very close to the inspected part so that the full potential of illumination intensity is used. Due to the highly diffuse light output, the illumination intensity decreases rapidly with a bigger working distance.

Illumination Method

Illuminated Object

A ring light can be mounted at a bigger working distance to the inspected part.
Due to very diffuse LEDs, the optimal working distance is between 100 and 600 mm.

Illuminated Object

Illumination Method

Working Distance

When increasing the working distance, the dark spot perceived by the camera is reduced in size and the illumination emitted from the dome light becomes linear along the camera axis. The effect on an engraved marking can be observed in the video.

Hole Aperture Adapter

The need of a camera hole at the top of the dome leads to a reduced illumination intensity in the center of the captured image (dark spot effect). If the industrial environment does not allow a bigger working distance to eliminate this effect, hole aperture adapters enable the reduction of the camera hole diameter. Camera hole sizes start from 30 mm (LMDX1xx) or 35 mm (LMDX2xx) as a standard going down to 20, 15, 10 or even 5 mm as required for the machine vision system.

All hole aperture adapters are included in the scope of delivery of the dome light (LMD) and the dome accessories (ZMRG001 and ZMRG002). The 20 mm hole aperture adapter also serves as a platform for the smaller adapter diameters.

Dome Light without HAA

Clearly visible dark spot

Dome Light with HAA 15 mm

Reduced dark spot

Dome Light with HAA 10 mm

Faint dark spot

Dome Light with HAA 5 mm

No dark spot

Illumination Alternative – Creating the Dome Effect Using Bar Lights

Besides using the LMD dome lights, a Machine Vision dome effect can also be created using LBA bar lights inside a box. The bar light illuminates the ceiling of the box which should be made of a white, matte surface, thus creating a homogeneous field of view which is perfect for illuminating complex surfaces.