SALSA

Capture the unseen by measuring all the light polarization information with a single portable device

Salsa camera full stokes polarization

Overview

Compact and robust, the SALSA Full Stokes polarization imaging has all the attributes of a regular digital video camera (easy operation, point & shoot, Ethernet connection) plus the polarization analysis capability.

Salsa camera full stokes polarization presentation

Coupled with a dedicated software, the SALSA Full Stokes polarization imaging system allows 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), 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, the Ellipticity angle, etc. 

Salsa camera full stokes presentation images

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

Degree of Polarization
Degree of Linear Polarization
Degree of Circular Polarization
Angle of Polarization

SALSA software allows the acquisition in real-time of the raw polarization images and the calculation of the 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 ans shades, target detection and identification and complex 3D surface reconstruction can be easily carried out.

Technology

The first polarization imaging systems 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.

SALSA Camera Full stokes presentation technology concept

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

SALSA specifications are summarized in the following table:
SPECIFICATIONS
Camera Size
3.2"x3.2"x4"
(80mm x 80mm x 100mm)
Video Format
Digital GigE

Resolution (pixels)
1,040 x 1,040
1,600 x 1,200
1,920 x 1,080
Frame rate at max resolution
(1,040 x 1,040 version)
12 frames / second (12bits)
20 frames/second (8 bits)
Bit depth
8 or 12 bits
Sync. interface
USB
Spectral bandwidth
520-550 nm
(custom in visible wavelength upon request)
Calibration
Factory calibrated
Lens mount
C-mount
(other option available upon request)
Software
SALSA 2.3
We also propose a SALSA working in the near infrared (750 nm – 830 nm). 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

Left : Without our multispectral polarimetric method
Right : With our multispectral polarimetric method

Stress application

Salsa camera full stokes polarization stress visualization

For more details please check the following article :
SPIE 2016 – Time translation architecture

3D reconstruction

Salsa camera full stokes polarization target detection

For more details please check the following article :
SPIE 2010 – SALSA – 3D reconstruction

Target detection

Salsa camera full stokes polarization target detection

For more details please check the following article :
JPL – Mud detection – ASC2008

Biology

Left : Intensity image
Right : Ellipticity image obtained with the SALSA

Resources

SALSA resources include litterature (articles & application notes) and videos to download.