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So, I basically want to know the range of the IR light that comes from a CD reader/writer (KSS-213C). I used an IR sensor(IR Photodiode) to detect the light that comes from the pickup reader, but until I go very close to the lens, I'm not getting any reading. (Following image source: google.com)enter image description here

Also, if I remove the lens, will the range of the IR laser increase?

If you need any other information, I will add it along later.

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  • \$\begingroup\$ They had to know for build quality, x +\- y can be expensive when y is small ie the positioning has to be very precise - as you are finding out... \$\endgroup\$
    – Solar Mike
    Jul 18, 2019 at 8:23

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http://www.farnell.com/datasheets/1944121.pdf Should tell you most of what you want to know. The lens focus is 3.6mm so that would be where the CD or your sensor needs to sit for the beam to be focused. Removing the lens will cause the beam to spread out over a large area as opposed to focusing on a spot so i'm not sure what you would achieve in doing that. In terms of the 'range of IR light' the data sheet says 760-800nm wavelength so no measuring needed :)

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  • \$\begingroup\$ I'm not repairing this device but trying to hack it and use it for something else. I basically need an IR source but with the ability to use lenses. So I thought the CD reader would be a nice and cheap way to do so. But I need the IR light to travel at least a couple of centimeters. Is that possible here? \$\endgroup\$
    – Dan
    Jul 18, 2019 at 8:51
  • \$\begingroup\$ Yes, the focs of the lens is about 3.6cm, but will the light completely dissipate after say 5cm? Has anyone tried to detect at such a distance using a really good sensor is what I meant to ask. Sorry for the confusion. \$\endgroup\$
    – Dan
    Jul 18, 2019 at 8:52
  • \$\begingroup\$ The further away from the light source the greater the dissipation. If you want to keep the light focused at a further distance you would need to create your own lens. I'm sure you will still detect some light at 5cm as is but without a clear idea of what the end goal that you want to build its difficult to help further. In terms of 'has anyone tried to detect at such a distance' sure, probably, but I don't know them :) Perhaps IR LEDs might be more suitable? what is the application of your device \$\endgroup\$
    – andowt
    Jul 18, 2019 at 8:59
  • \$\begingroup\$ So what I'm trying to create is like an IR source and I need to be able to focus that beam on different points on height. So something like spectacles but for Infrared light. Different focal lengths would focus on different points. So I should have instead first tried for an IR Source, but wouldn't be able to move a lens up and down with such precision. Hence I went in the direction of CD readers, where I have the ability to move the lens and change the focal point. But what I need is of a higher dimension, i.r of order of centimeters \$\endgroup\$
    – Dan
    Jul 18, 2019 at 9:02
  • \$\begingroup\$ That's a start but before you can go further we need constraints. What height range are you working within nm, mm, m? what medium is the light projecting onto? is a sensor reading the emitted IR light? and most importantly what is the application ie purpose, so you want to focus IR light at varying height but why?... All these questions are important to produce a specification so you select correct parts and design accordingly \$\endgroup\$
    – andowt
    Jul 18, 2019 at 9:09

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