Machine vision illumination - Front lighting and diffuse light

In machine vision, lighting situations can be divided into two fundamental cases. Front lighting, where the object is illuminated from the camera direction, and backlighting, where the camera looks toward the light source and captures the object as a silhouette.

In this part of our illumination series, we want to focus on front lighting. More precisely, on the allrounder. Diffuse light.

Diffuse light - why it works so well

In the past, photographers often referred to a “cloudy day” as the ideal condition. A uniformly overcast sky produces soft light that comes from all directions. This exact characteristic is what makes diffuse light so valuable.

Transferred to machine vision, this means: Only when light reaches the object from as many directions as possible can photons, following the rule angle of incidence equals angle of reflection, find their way to the sensor at every point on the surface. For our “path of light”, diffuseness is therefore ideal.

The result is fewer harsh shadows, fewer issues with reflections, and very uniform illumination. If the goal is not to deliberately increase contrast but instead to “see everything”, then diffuse light is exactly the right choice.

Dome lighting

The best solution for truly diffuse front lighting is the dome. Simply put, it is half of an integrating sphere. A complete integrating sphere is, from a physical point of view, the only setup that produces perfectly diffuse light. Anyone interested can easily find more detailed explanations on this topic on the web.

The dome applies this principle very effectively. The light is scattered multiple times and reaches the object almost without direction. This makes even complex surfaces reliably visible.

Our approach: Diffuse light for large components

In industrial practice, domes are not always the ideal solution. Especially for larger components, geometric limitations quickly arise. For this reason, we also use “cubes” made of highly diffuse light panels in many applications.

This concept is what led to the development of our pvLight. A flexible and very homogeneous diffuse lighting solution for larger inspection objects. The goal was to transfer the advantages of the dome principle into a practical and scalable design.

Want to know if diffuse light is the solution for your application? Let us test for you!