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The Curve Effect

The Curve Effect

The Curve Effect is a powerful tool for creating excellent homogeneity over a large Field of View (FoV) such as those in Pick and Place applications. The patented Curve Effect is created using angle changers on the LBA bar light which varies the illumination intensity along it’s length. This dims the light in the centre of the field of view and eliminates hotspots.

What Is an Angle Changer?

Angle changers are rugged light diffusers which clip securely onto the front of LBA bar lights to vary the intensity of the illumination. Different angle changers can be used to change the beam angle, providing Narrow, Medium, Wide or Line illumination, starting from a 7° bar light configuration. Each angle changer is 125 mm long and can be used on LBA bar lights from 125 mm to 500 mm long. Note that the shortest bar that can utilise the Curve Effect is 375 mm.

How to Create the Curve Effect?

In order to create the Curve Effect, a wider angle changer is used in the center of the bar light than those at the ends of the bar light. This will dim the light intensity in the center of the light source. 

To illustrate the curve effect, the sample images were taken with the same setup on an LBAW301 bar light with 375 mm, each with three Angle Changers. The first image uses three medium Angle Changers (ZBAG002). In the second image, the Angle Changer in the middle was replaced by a wide Angle Changer (ZBAG003) to dim the light in the center and thus help to eliminate hotspots.

The Curve Effect allows to create the best balance between brightness and uniformity. It is suitable for high-speed applications that require more homogeneity across the illuminated field.

Please contact our illumination experts to set up similar applications.

What Does the Camera See?

There is a big difference in the perception of images between the human eye and the camera. The aim of Machine Vision illumination is to achieve a uniform brightness across the field of view captured by the camera.

Note: The Curve Effect can only be used in brightfield illumination scenarios.

Creating Homogeneity for the Camera

When a light source strikes a surface, it reflects with a Lambertian distribution. This means the reflected light in the direction of the red arrow may be 30% and the light in the direction of the green arrow may be 80% of the intensity of the direct reflections.
It can be assumed that a bar light consists of an array of light point sources which follow the Lambertian distribution effect. For LBA bar lights, this means that the illustration of this light effect can be simplified as shown in the picture. 
The camera will perceive the light based on the distribution shown by the blue arrows. If each arrow length is relative to the illumination intensity, it means that the camera will capture a hotspot in the center of the field of view (FoV). Hotspots can be deceiving as the measurement of brightness with a lux meter would appear homogeneous.
The light intensity emitted by the bar light can be varied using Angle Changers. Due to this, the homogeneity of the light as perceived by the camera can easily be controlled. In the shown example, two different Angle Changers reduce the light intensity in the middle of the bar light. As the blue arrows are now close to being the same length, this results in an image which is perceived as uniform by the camera.
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