Modifying a Digital Webcam to Create Infrared Images: Theory

All continuous light sources, such as the sun, tungsten lamps, candles and some flourescent lights emit visible light and infrared radiation. It is the reflection of this light off of an object that enables the object to be seen.

While the human eye can only see the spectrum of visible light, digital camera sensors are inherently sensitive to both visible light and infrared light. However, to improve the quality of digital images, digital cameras are outfitted with filters that attempt to eliminate as much of the infrared light as possible.

These filters on older model cameras were not always successful at eliminating the full range of infrared light so that it might be possible to create infrared images without making any modifications to the camera. With such a camera true infrared images could be produced in two ways:
1. Illuminate objects in a completely dark space using a light source consisting of infrared light wavelengths only (an infrared light).
2. Illuminate objects with a continuous light source (sun, tungsten lamp or candle), but outfit the camera with a filter to block any visible light wavelengths.

Newer models of digital cameras have filters that can block the full range of infrared light. In order to create an infrared image with such cameras, the camera would have to be modified either by:
1. removing the infrared filter from the camera lens assembly or
2. outfitting the camera with a lens assembly that does not include an infrared filter.

See the posts below to find out how to test your webcam's sensitivity to infrared light and how to make any necessary modifications to the camera so that it will be capable of producing infrared images.

Testing the Infrared Sensitivity of Your Webcam

To see how well your camera's infrared filters block the infrared wavelengths of light, try any of the following procedures:

1. Start up your webcam and make sure it it functioning properly under normal lighting. Use a remote control from a television, cd/dvd player, VCR or other such device to send an infrared signal toward the camera sensor. If you see a change in the camera's output on your computer monitor, the infrared wavelengths are not being completely blocked by the camera's infrared filter.

For a further test, try illuminating an object in a darkened room or under a thick blanket using the remote control as a light source. Make sure that the camera is displaying the object correctly under normal light and that the screen image goes black in the darkened environment. Then use the remote control to illuminate the object. If you can see an image on the screen, then your camera is capable of creating an infrared image as it is.

See the step below for filtering out the visible light wavelengths so that you can create true infrared images using continuous light sources.

Testing Infrared Sensitivity (continued)

2. Outfit your camera with a filter to block any visible light wavelengths and see if you can still see any image on your computer screen. You can use a standard #87 photo filter over your webcam lens or your can make your own filter from two pieces of developed color film. Just find a part of the color negative that looks completely black and cut out two pieces large enough to fit snugly over the lens opening as shown in the photo above.

If you can still see an image on your computer that is clear and bright enough for normal viewing, you do not have to make any other modifications to your camera. You are seeing infrared images! If your screen is black, you will have to modify your camera to remove its infrared filters. Follow the steps below.

Modifying a Webcam to Remove Infrared Filters

Removing an infrared filter involves disassembly of the lens unit from the camera.

For the Kensington webcam this was just a matter of pulling out the lens unit. It is held in place by the pressure of a rubber O-ring.
The Intel webcam needs to be disassembled to get to the lens assembly. Here the camera bottom has been removed.

Removing Infrared Filters - Intel Camera (continued)

This is the Intel camera module removed from its housing. The lens assembly unscrews from the front of the module to expose the CCD sensor.




The dark square in the middle of the lens housing is the CCD sensor that creates the digital signals for the image.

Removing the Infrared Filter (continued)

To remove the infrared filter, further disassembly of the lens unit would be required. Unfortunately, the lens units on both the Kensington and Intel webcams were glued together making further disassembly difficult if not impossible.

If you have a lens unit that can be taken apart, you would want to remove the infrared filter that is part of its assembly and then reassemble the camera. You would then be ready to take infrared pictures and videos.

We will have to build a replacement lens assembly for the two webcams we have. First reassemble the cameras without the lens assembly as shown in the picture above. Then proceed to the steps below.

Materials for the Lens Assembly

A glass or plastic lens. This lens had a focal length of about 10".

For the lens base I used an 6"long cardboard mailing tube that was the same diameter as the lens.

For the lens sleeve I used a piece of black poster board 5" wide and long enough to go twice around the circumference of the lens.


The only other item you will need is a roll of double-stick cellophane tape, that is, tape that is sticky on both sides.

Prepare the Lens for Mounting

Put a layer of double-stick tape around the outside of the lens.

Prepare the Lens for Mounting

I added strips of poster board to make the lens diameter slightly larger than the diameter of the mailing tube.






The lens unit ready for mounting.

Constructing the Lens Sleeve

I put a couple strips of double-stick tape around the outside of the lens unit. then I set the mailing tube on top of the lens in order to help keep the lens and the poster board sleeve aligned.



Finally, I wrapped the poster board around the lens and mailing tube.

Constructing the Lens Sleeve

Be sure to roll the poster board tightly around the lens unit and keep the edge of the poster board aligned with the edge of the lens.







Tape the edge of the sleeve to complete the sleeve assembly. The sleeve should move freely over the lens base (the mailing tube).
Click here to see how the lens assembly functions.

Preparing the Camera

I removed the lens assembly from the Kensington webcam by simply pulling it out.









You can see the square image sensor inside of the lens opening.

Preparing the Camera

I covered the power-on light with a piece of black electrical tape.








The lens base will fit over the face of the Kensington webcam and will enclose the lens opening and the power-on light.

Fitting the Lens Base to the Webcam

I attached the cardboard mailing tube to the face of the webcam using strips of duck tape.







Narrow strips of tape follow the irregular contours of the camera better and create a tighter connection.

Fitting the Lens Base to the Webcam

The completed duck taped camera and lens base assembly.








Because duck tape is semi-translucent I added a strip of black electrical tape around the base of the tube to keep the light out.

Fitting the Lens Base to the Webcam

The completed duck taped camera and lens base assembly.








Because duck tape is semi-translucent I added a strip of black electrical tape around the base of the tube to keep the light out.

Finishing the Lens Assembly

The final taped lens assembly.








I added calibration markings on the barrel of the lens assembly to aid in focusing the webcam.

The Completed Camera and Lens Assembly

Top View








View of the lens.

Fitting a Replacement Lens to the Intel Webcam

The lens used has a shorter focal length and therefore needs a shorter base tube.


Try to keep the camera sensor centered in the tube opening.



Be sure to outfit the camera with a visible light filter as described in the previous blog "Testing Infrared Sensitivity (continued)" located above.

Intel Webcam Lens (continued)

The finished webcam with replacement lens.



The modified webcam mounted on a tripod.

Infrared Test: Modified Lens with no Filters

The camera was mounted on a tripod and was focused on a CD-Rom disc spinning on a turntable.

A movie of the spinning CD was created using the flourescent lighting in the room. Click here to see the movie using flourescent light.

Next, all of the room lights were turned out and the spinning CD was illuminated with infrared light from a TV remote control. Click here to see the movie using an infrared light source. The flickering of the light is due to the continuous sending of control codes by the remote control.

As would be expected, the movie using the flourescent lighting has recorded all of the colors in the spectrum of visible light that are being reflected by the CD. However, when using the infrared light source for illumination, only the infrared light is being picked up by the camera and recorded in black and white on the movie.

Infrared Testing: Modified Lens with Filters

This is the Intel modified webcam outfitted with a visible light filter. It will only record the image as it is illuminated by the infrared light of the sun.



The camera is directed at the treetops where the green of the trees meets the blue of the sky.

Click here to see a video of the infrared images.

As expected, the blue sky appears as dark grey. The green leaves in bright sunlight are almost white. The leaves with less sunlight appear in various shades of grey.

References

For more information on how to modify a digital camera to create infrared images follow these links:

These two are from Rob's list. Good overall discussion of how to modify a webcam for infrared.
www.hoagieshouse.com/IR/
www.hoagieshouse.com/IR/Creative/Creative.html

www.instructables.com/id/EF7RFPCE2YEP287GZV modifying a Logitech Quickcam.

Here is a book available in the Milwaukee Public Library that has a lot of good information about infrared photography and modifying digital still cameras to create infrared images:

Rice, Patrick (2005). Digital Infrared Photography, Buffalo, NY: Amherst Media.