Infra Red Emittor and Collector

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Discussion Overview

The discussion revolves around the behavior of infrared rays emitted from different types of infrared emitters, specifically whether they spread out or maintain a narrow beam similar to lasers. Participants explore the implications of emitter design on the spread of infrared light and seek information on how to determine the characteristics of specific components.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether infrared rays spread out or behave like lasers, depending on the distance from the object being scanned.
  • Another participant states that infrared light behaves similarly to visible light, being either coherent like a laser or diffuse like a flashlight, depending on the emitter.
  • A further contribution notes that even lasers exhibit some degree of spreading, which is influenced by the design of the source.
  • Participants inquire about indicators of emitter design that would reveal whether it is intended to produce a focused beam or a spread pattern.
  • One participant suggests that the intensity profile of the emitted beam, which may follow a bell-shaped curve, is crucial for understanding its spread, and emphasizes the need for manufacturer specifications to obtain this information.
  • Another participant references a specific component and its datasheet, noting that while the design suggests some angular spread, the exact angle is not specified in the documentation.

Areas of Agreement / Disagreement

Participants express varying views on the behavior of infrared emissions, with some agreeing that design influences spread while others seek clarification on specific components. The discussion remains unresolved regarding the exact nature of the spread for the component in question.

Contextual Notes

Limitations include the lack of specific data on the angular spread of the infrared beam from the referenced component, as well as the dependence on the design characteristics of different emitters.

Jones1987
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Do infra red rays spread out or do they work the same as lasers and fire in a single ray?

Example if I have the emittor at different distances from the object it is scanning (e.g a ground surface say 10mm and 30mm distances) do the rays spread and further to cover a wider range, or do they fire down straight no matter the distance?

Thanks.
 
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That depends on the emitter. Infrared light works the same way as visible light. It can be coherent as in a laser or diffuse like a flashlight.
 
Even lasers spread out. In general, every source does. It is a matter of design.
 
It surely spreads to some degree, but it may not be relevant. The information you may need would be the intensity profile, or the intensity of the beam as a function of the exit angle. This should be some kind of bell shaped curve I(theta). What you are asking for is the shape of this curve. Only the manufacturer can provide such information (or anyone else who has the device and has bothered to the measurement).
 
Jones1987 said:
What are the tell tale signs of how the component is designed? How will I know if it is set-up to fire in a line, or create a spread?

This is the component I've been looking at:

http://www.active-robots.com/products/sensors/sensors-fairchild.shtml
That page has a link to http://www.active-robots.com/products/sensors/fairchild/qrb113x.pdf" which has a scale drawing of the part. Looks like the beam is emitted by an IR LED in a recessed hole. So the beam will have some angular spread, but there's nothing in the datasheet telling us how big that angle is.
 
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