Images with a Single Photoresistor

When you take a digital photograph, an array of (many) photodetectors captures the scene in front of the camera. This data is then recorded with the help of advanced electronics and processed into images ready for posting, sharing, or maybe even printing. However, as Jon Bumstead explains in his project tutorial and “illuminates” in the video below, it’s possible to obtain digital images with just one photoresistor — AKA light-dependent resistor (LDR).

The big caveat to this process is that Bumstead’s setup won’t capture fast-moving sports photography, or even a family photo, but requires a stationary object, careful lighting via a projector, and a dark environment. On the other hand, as the writeup's “Non-line-of sight Imaging” title implies, the sensor doesn’t actually have to be aimed at the to-be-captured object.

To take an image, a projector illuminates the “photographed” object point by point, or in different patterns of light and darkness. The reflected light patterns are then picked up by an LDR and fed into a database, using an Arduino as the physical interface. This data is then processed by a Python script, producing images via this single sensor “array.”

Interestingly, the LDR doesn’t even have to be facing the to-be-sensed scene, potentially producing better results when pointed at a reflective piece of paper acting as a diffuser instead.

While the acquired images are low-res and in black-and-white, it’s an amazing concept that could be further developed for better and better quality. Perhaps it could even be used to solve specific niche imaging challenges. Or you could simply say it’s a new twist on Plato’s ancient cave allegory... if the ancient philosopher had access to a projector and modern processing techniques!