Researchers have developed SweepLED, a low-cost smartphone accessory designed to help travelers find concealed cameras in hotel rooms and short-term rentals.
The prototype uses an LED-equipped phone case, computer vision, and machine learning to identify the optical signatures of camera lenses in under 5 seconds.
Hidden cameras can be placed inside common objects such as clocks, adapters, smoke detectors, power banks, motion sensors, and decorative items.
Detecting them has traditionally required costly equipment or slow manual checks with handheld lens finders. These tools often produce false alarms because glossy plastic, glass, metal, and reflective surfaces can look similar to a camera lens.
New $7 SweepLED Gadget
SweepLED aims to reduce that problem by changing how light is used during an inspection. The system attaches a compact LED array to a smartphone case.
Instead of using a single fixed flashlight angle, the LEDs illuminate a suspected object from multiple angles in a controlled sequence while the phone camera remains still.
According to KAIST researchers report through Singapore Management University, the method exploits differences in how camera lenses and ordinary shiny objects reflect light. Glossy surfaces typically produce bright reflections that move as the light direction changes.
A camera lens can create more stable and structured reflections because of its lens, aperture, and image sensor assembly. During a scan, SweepLED records a short video while LEDs switch on in sequence.
The software stabilizes the video to reduce hand movement, compares LED-on and LED-off frames, and locates small bright regions that may resemble a lens.
It then tracks those reflections over several frames. It uses a machine-learning classifier to decide whether the object is likely to contain a hidden camera.
The KAIST researchers tested the prototype against 12 commercially available hidden-camera objects and 18 non-camera reflective items. The system achieved an overall detection accuracy of 93.9 percent.
It detected hidden cameras in about 95 percent of the camera-equipped objects it tested. It produced a 7.2 percent false-positive rate on non-camera objects.
Each inspection uses 3 viewpoints, with every LED sweep lasting about 1.5 seconds. That brings the total scan time for one object to roughly 4.5 seconds.
The core electronic components used in the prototype cost less than $7, making the concept suitable for a low-cost travel accessory or hotel-provided privacy tool.
The prototype uses directional LEDs, a PWM controller, and an ATmega328P microcontroller. The accompanying Android application controls the LED pattern and captures video through the phone camera. The researchers said the design could eventually be built into normal phone cases or integrated into future smartphones.
SweepLED is not a guarantee that every hidden camera will be found. Its performance can fall when a lens is behind heavily tinted, opaque, or highly diffusive material.
Detection accuracy also declined when the camera was scanned from around 100 cm away, so users should inspect suspicious objects at closer range.
The system also cannot replace a full physical inspection or a report to hotel management and law enforcement when a device is discovered.
Still, SweepLED demonstrates how a $7 LED attachment and a smartphone could make hidden-camera checks faster, more accessible, and less dependent on specialist equipment for hotel guests and Airbnb travelers.
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