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Components

Telecentric lights

Thumbnail of Telecentric lights image Thumbnail of Telecentric lights image

​Ideal for measurement applications where precision is key, Telecentric lights, used in combination with a matching lens give extremely high contrast images with no “bleed” around the part edges. This benefit is seen most clearly on shiny parts and parts with curved sides where a standard diffuse light could introduce reflections on the part sides.

A diffused back light illuminator will not give the same crisp results as the contrast around the edges is just nowhere near as high. As a result, a higher measurement accuracy can be achieved. This is especially true of objects with rounded edges such as cylinders or globe shaped components. Reflections are dealt with much better using a telecentric light leading to much more accurate sizing measurements. This is because rays of light from a standard light expand and interfere with one another, producing diffuse reflections.

Telecentric lights (sometimes known as a collimated backlight) rely on excellent optics in front of the LED light source to produce a collimated beam of light from 10 to 130 mm diameter. Collimated light rays exit the illuminator and remain collimated as they strike an object’s surface. These lights only work in conjunction with the matching telecentric lens and are available with a full range of accessories from prisms that fit on the end of the light for tight working areas to mounting and adjustment aids.

Benefits of a Telecentric Light

Other benefits include the collection of more light by the camera detector when used in conjunction with a telecentric lens. This ensures a higher signal to noise ratio.

The parallel rays produced by collimated illumination increase the depth of field of the lens allowing greater focussing accuracy. A key characteristic of telecentricity, then, is constant magnification regardless of image and/or object location.

Translucent objects and glass can also be imaged with extremely high contrast using these lights as any part of an item that blocks or distorts the light gives a very dark response.

Specific benefits include:

  • A much higher chance of detecting small defects
  • Increased measurement accuracy compared to standard backlight illumination
  • Blurred edges are negated as diffuse reflections are practically eliminated
  • Light intensity from collimated light rays can be controlled
  • Contrast in images can be massively increased
  • Increased light intensity means reduced camera exposure times
  • Machine vision systems can deal with more measurements in a period of time using telecentric light compared to standard lights
  • An increased working distance between inspection object and light can be coped with

How Does Telecentric Illumination Create a High Contrast Silhouette?

Telecentric lights work using high grade glass optical lenses to collimate light from a fiber optic light source or LED spotlight. Scattered light from the source becomes parallel after moving through the lens which also increases its concentration. Very little light is wasted and close to 100% hits the object being inspected. Reflection is negligible. The intensity of light illuminating the object can be controlled with many telecentric lights to achieve the optimum lit environment.

Why You Need Telecentric Lighting in Machine Vision Applications

Machine vision systems rely on imaging lenses, lighting sources and cameras along with other components in order to maximise performance. Each must be set up correctly in order to achieve precise results. Lighting is a key factor and cannot be underestimated in its importance so having someone to advise which type of light is best for your application is key. This is where Fisher Smith can add value by applying real world experience to optimise for your needs.

Our case study below shows one example of what can be achieved with telecentric lights. To talk to us about how we can supply the telecentric lights you need, please use the contact form here or give us a call on +44 (0) 1933 625162.