SALSA
Full Stokes polarization camera
Overview
Compact and robust, the SALSA Full Stokes polarization camera has all the attributes of a regular digital video camera (easy operation, point & shoot, Ethernet connection) plus the polarization analysis capability.
Coupled with a dedicated software, the SALSA Full Stokes polarization imaging system is able to measure all the Stokes polarization information for each pixel of the image, in real time. Applications of SALSA range from target detection and identification to 3D reconstruction and robotic vision. SALSA can be operated in passive and active imaging.
Principle
Along with the intensity and the spectrum, the polarization of light carries abundant information. The Stokes formalism allows for complete description of any partial or total polarization state. While most of the available polarization imaging cameras perform only linear Stokes polarization imaging – only the linear polarization can be quantified – the SALSA performs live measurement of the full Stokes vector for each pixel of the image at a video frame rate. Many polarization-related parameters can be visualized in real time such as the Stokes parameters (S0, S1, S2 , S3), the Degree Of Polarization (Linear or Circular), the Angle Of Polarization or the Ellipticity angle.
This example shows two pairs of glasses. Left ones are linearly polarized sunglasses; right ones are circularly polarized 3D-movies glasses
Stokes
parameters
Advanced
parameters
SALSA software can acquire – in real-time – the raw polarization images and display the resulting Stokes vector images. Different polarization images (Angle Of Polarization, Degree Of Linear Polarization, Normal to the observed surface, etc.) are then easily computed at video rate.
Applications such as image contrast enhancement, imaging through canopies and shades, target detection and identification and complex 3D surface reconstruction can be easily carried out.
Technology
The first polarization cameras were made with mechanical rotation of polarizer(s) and waveplate(s) between each frame. Those systems are usually quite slow and very sensitive to motion of the scene between frames. We use a patented polarization filter based on ferroelectric liquid crystals (FLC) which dramatically reduces the time required to acquire the polarization frames. This architecture allows fast acquisition of four polarization frames that are later used to calculate the Stokes vector for each pixel of the image.
The critical point is to link the polarization raw frames to the Stokes parameters. We developed a calibration procedure to determine the calibration matrix that permits to calculate the four Stokes parameters for any incident polarization state, partial or total.
Specifications
(80mm x 80mm x 100mm) | |
Resolution (pixels) | 1,600 x 1,200 1,920 x 1,080 |
(1,040 x 1,040 version) | 20 frames/second (8 bits) |
(custom in visible wavelength upon request) | |
(other option available upon request) | |
Contact us for more details.
* Due to Bossa Nova Vision continuous improvement policy, specifications are subject to change without notice.
Applications examples
Dehazing through fog
Top : Without our multispectral polarimetric method
Bottom : With our multispectral polarimetric method
Stress application
For more details please check the following article :
SPIE 2016 – Time translation architecture
Article on SPIE website
3D reconstruction
For more details please check the following article :
SPIE 2010 – SALSA – 3D reconstruction
Biology
Top : Intensity image
Bottom : Ellipticity image obtained with the SALSA
Resources
SALSA resources include litterature (articles & application notes) and videos to download.