Suppressing Background Light in Multispectral Imaging

Suppressing Background Light in Multispectral Imaging

Just in time for the end of the year, a new paper published by Heliotis is entitled “Background Light Suppression for Multispectral Imaging in Surgical Settings.” By using a smart pixel camera and active illumination, the researchers effectively suppress background light in multispectral imaging. For example, this technique will work even when taking measurements with fireworks in the background.

The experimental setup included the Heliotis heliCam^Tm C4 Lock-In camera. Here is an excerpt from the paper explaining usage of the camera:

The smart pixel camera, referred to as C4, is a dual-phase lock-in camera (C4.0S41U, Heliotis AG, Root, Switzerland). It features an image sensor with a specialized pixel architecture with a spatial resolution of 512 × 542 pixels, which measures the in-phase (I) and quadrature (Q) components of a signal at a given reference frequency, 𝑓𝑟𝑒𝑓.

The working principle of the C4 involves dividing each demodulation period by duration 𝑇=1/𝑓𝑟𝑒𝑓 into four quarter-periods (I, II, III, and IV). This is shown in part b of the figure above. The I-component of one such period is calculated by taking the difference between the signal in quarter-periods I and III, while the Q-component is obtained from the difference between quarter-periods II and IV. This process is repeated for a set number of demodulation periods, 𝑛𝑝𝑒𝑟𝑖𝑜𝑑𝑠. The resulting in-phase and quadrature images are formed by summing the respective I- and Q-components over 𝑛𝑝𝑒𝑟𝑖𝑜𝑑𝑠. This principle is realized directly on the sensor in an analog manner, and only the resulting in-phase and quadrature images are transmitted after a burst.

Features of the heliCam^Tm C4 Lock-In camera include:

• Standard C-mount for lenses
• GigE and GenICam interfaces
• Configurable lock-in functionality
• Amplitude and phase information from every pixel
• Demodulation of signals up to 250 kHz
• High background suppression
• Configuration and image acquisition using heliViewer™
• Python, Matlab, LabVIEW, C++, .NET interfaces with heliSDK™ 4
• Programming examples to get you started

To request more information or a quotation for Heliotis products, contact IL Photonics.