Polarization Navigation Research Articles

Design and Calibration of a Novel Camera-Based Bio-Inspired Polarization Navigation Sensor

The remarkable ability of animals using the skylight polarization pattern provides a significant inspiration for the autonomous robotic navigation. The bio-inspired polarization navigation approach with advantages of efficiency and reliability has aroused much interesting for experts to perform further research. The sensor of measuring the skylight polarization pattern plays a key role in bio-inspired polarization navigation. A novel camera-based bionic polarization navigation sensor is designed and implemented. We propose a robust measurement method based on the least squares by utilizing all outputs of measurement units. For improving the precision of measurement, the errors of sensor are analyzed, and an effective calibration algorithm is proposed in detail. The experiment results show that the measurement accuracy is improved greatly after calibration. Finally, to evaluate the performance of our sensor, experiments of measuring the actual skylight polarization pattern are performed and compared with the results from the single-scattering Rayleigh theory. The comparison results indicate that our sensor can achieve an effective and accuracy measurement in practice.

Real-time Imaging Orientation Determination System to Verify Imaging Polarization Navigation Algorithm.

Bio-inspired imaging polarization navigation which can provide navigation information and is capable of sensing polarization information has advantages of high-precision and anti-interference over polarization navigation sensors that use photodiodes. Although all types of imaging polarimeters exist, they may not qualify for the research on the imaging polarization navigation algorithm. To verify the algorithm, a real-time imaging orientation determination system was designed and implemented. Essential calibration procedures for the type of system that contained camera parameter calibration and the inconsistency of complementary metal oxide semiconductor calibration were discussed, designed, and implemented. Calibration results were used to undistort and rectify the multi-camera system. An orientation determination experiment was conducted. The results indicated that the system could acquire and compute the polarized skylight images throughout the calibrations and resolve orientation by the algorithm to verify in real-time. An orientation determination algorithm based on image processing was tested on the system. The performance and properties of the algorithm were evaluated. The rate of the algorithm was over 1 Hz, the error was over 0.313°, and the population standard deviation was 0.148° without any data filter.

Algorithm and Accuracy Evaluation of Autonomous Bionic Positioning Method based on Skylight Polarization

As the skylight polarization navigation at present is based on dead reckoning which can only provide orientation information to navigate or relative position but not the absolute location of the observer, in this paper, a bionic absolute positioning method based on skylight polarization was proposed: the longitude and latitude of the current position could be solved through the polarization angle of the skylight, the course angle of the vehicle, the relative relationship between the solar and the earth. In addition, the simulation verification provided an accuracy of 0.483km in average. A positioning error model was developed, and the simulation shows that the precision of the sensors has a great impact on the positioning accuracy. Finally, the initial outdoor tests give a longitude accuracy of -0.149o in average and a latitude accuracy of 0.418o in average. Although the positioning accuracy obtained from the experiment is no better than the existing positioning systems, such as GPS, the proposed positioning method which is totally autonomous, convenient and without accumulated error is still worth to be improved since it would be useful when manmade positioning systems are disabled.

A Novel Calibration Model of Polarization Navigation Sensor

In this paper, a polarization navigation sensor is designed based on the polarization sensitivity mechanisms of insects. A new calibration model by taking full advantage of both reference angle of polarization and constant degree of polarization is presented to determine calibration parameters. Unlike existing calibration algorithms, the proposed algorithm makes the calibration problem well-posed. The results of simulations and experiments show that the proposed algorithm is more stable than the compared methods for the calibration applications of polarization navigation sensors.

A Robust Adaptive Angle Algorithm for Imaging Bionic Polarization Navigation Sensor

This paper presents a precise angular algorithm for the imaging bionic polarization navigation sensor. The algorithm is targeted for a imaging sensor with bilayer nanowire polarizer which is multi-orientated of 0°, 60°, 120° and 90°, 150°, 210°. The algorithm is considered to extract intensity values of pixels in homogeneous regions, eliminate noise contained in image and compensate errors occured in the fabricaiton process of nanowire polarization filters. And the occlusion problem has to be compensated by neighboring pixels. The algorithm considered in this paper is able to solve overdetermined system of linear equations, and give a set of least square solutions of the Stokes parameters and the angle of polarization as output. The performance of the algorithm along with the experimental results of the angle measurement are also presented. Based on the comparison results, the algorithm achieves a best performance for the angle of polarization.

Angle algorithm based on Hough transform for imaging polarization navigation sensor.

Polarization navigation is a promising orientation-determination method inspired by insects' foraging behavior that offers the advantages of autonomous and high precision. In this paper, using the solar meridian as an azimuth reference is proposed. The model of the distribution pattern of the polarized skylight projected onto an imaging sensor is analyzed. The sufficient features of the solar meridian are proven. According to these features, an angle algorithm for an imaging polarization navigation sensor based on a machine-vision algorithm is proposed. In consideration of noise in images, the relation between the measured angle and the noise in images is modeled. This model cannot only optimize the threshold tolerance R in the algorithm but also describe the effects of several primary factors that can affect the measuring precision. In the simulation test, the measurement accuracy was better than 0.34°. When the algorithm was tested on the polarization-detection system, the measurement accuracy was better than 0.37°.

Compass information extracted from a polarization sensor using a least-squares algorithm.

Skylight polarization provides a significant navigation cue for certain polarization-sensitive animals. We designed a polarization navigation sensor based on the polarization sensitivity mechanism of insects. In this paper, the principle of our polarization navigation sensor is introduced. The relationship between the degree of polarization (DOP) and the error of the angle of polarization (AOP) is examined. A new DOP and AOP calculation algorithm using a linear least-squares algorithm is presented. The results of simulation and experiments reveal the essentiality of DOP calculation and demonstrate the efficiency and accuracy of the proposed algorithm.

A novel angle computation and calibration algorithm of bio-inspired sky-light polarization navigation sensor.

Navigation plays a vital role in our daily life. As traditional and commonly used navigation technologies, Inertial Navigation System (INS) and Global Navigation Satellite System (GNSS) can provide accurate location information, but suffer from the accumulative error of inertial sensors and cannot be used in a satellite denied environment. The remarkable navigation ability of animals shows that the pattern of the polarization sky can be used for navigation. A bio-inspired POLarization Navigation Sensor (POLNS) is constructed to detect the polarization of skylight. Contrary to the previous approach, we utilize all the outputs of POLNS to compute input polarization angle, based on Least Squares, which provides optimal angle estimation. In addition, a new sensor calibration algorithm is presented, in which the installation angle errors and sensor biases are taken into consideration. Derivation and implementation of our calibration algorithm are discussed in detail. To evaluate the performance of our algorithms, simulation and real data test are done to compare our algorithms with several exiting algorithms. Comparison results indicate that our algorithms are superior to the others and are more feasible and effective in practice.

A bionic camera-based polarization navigation sensor.

Navigation and positioning technology is closely related to our routine life activities, from travel to aerospace. Recently it has been found that Cataglyphis (a kind of desert ant) is able to detect the polarization direction of skylight and navigate according to this information. This paper presents a real-time bionic camera-based polarization navigation sensor. This sensor has two work modes: one is a single-point measurement mode and the other is a multi-point measurement mode. An indoor calibration experiment of the sensor has been done under a beam of standard polarized light. The experiment results show that after noise reduction the accuracy of the sensor can reach up to 0.3256°. It is also compared with GPS and INS (Inertial Navigation System) in the single-point measurement mode through an outdoor experiment. Through time compensation and location compensation, the sensor can be a useful alternative to GPS and INS. In addition, the sensor also can measure the polarization distribution pattern when it works in multi-point measurement mode.

Integrated Polarization Dependent Photodetector and Its Application for Polarization Navigation

Navigation technology is an essential ability for the survival and development of animals and humans. We integrate a bilayer nanowire polarizer with a photodetector using nanoimprint lithography, and apply the integrated polarization dependent photodetector (PDP) as a polarization navigation sensor. The proposed device is designed to have the top sensitivity at the blue band. The integration process can fabricate nanowires with multiorientations simultaneously and eliminate the alignment error. The angle output experiment of the navigation sensor using the integrated device is investigated. The angle output error is within <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\pm}{0.1}^{\circ}$</tex></formula> . The results show that the fabricated PDP has good application prospects in the field of polarization navigation.

A New Mechanical Moving Device Based on the Polarization Navigation Method

The polarization phenomenon occurs when the sunlight is scattered by atmospheric molecules. As a result, there is a polarization pattern in the sky. An amount of research shows that many nature insects can derive orientation information from this pattern, such as bees and ants. The fundamental polarization pattern in the sky is presented. The characters and the orientation mechanism of the nature insects are discussed. The basic principle of designing the polarization skylight navigation sensor is explained. The domestic and foreign relevant researches and application situation of this new navigation method are summarized in details. In the end, the characters of application fields and its application prospect are previewed.

Positioning algorithm based on skylight polarization navigation

Possessing an autonomous navigation and positioning capabilities that does not rely on GPS or other satellite navigation systems is of great importance when satellite signal is out of service. Many insects, such as desert ant Cataglyphis and dung beetle, are able to derive the direction information according to the pattern of polarization in the sky. Inspired by the polarization sensitivity mechanisms of the insects, several kinds of bionic polarization navigation sensors have been developed. However, all of them can only derive the orientation information, but not the latitude and longitude of the current position. In this study, an integrated positioning algorithm based on skylight polarization navigation was proposed. Combining skylight polarization navigation with celestial navigation, the geographical position could be determined by two independent observations. The result validated the feasibility of the algorithm.

Biologically inspired autonomous agent navigation using an integrated polarization analyzing CMOS image sensor

The navigational strategies of insects using skylight polarization are interesting for applications in autonomous agent navigation because they rely on very little information for navigation. A polarization navigation sensor using the Stokes parameters to determine the orientation is presented. The working principle of the sensor is based on egocentric navigation predominant in insects. The Stokes parameters computed from the measured intensities using a metallic wire grid micropolarizer are used to retrieve positional information. The computation of the Stokes parameters is simplified to allow for a future on-chip computational algorithm implementation, which would result in highly miniaturized navigational sensors. The image sensor consist of an array of 128×128 pixels, occupies an area of 5×4 mm2 and it has been designed and fabricated in a 180 nm CMOS process.

Polarization patterns of the summer sky and its neutral points measured by full–sky imaging polarimetry in Finnish Lapland north of the Arctic Circle

Using 180° field–of–view (full–sky) imaging polarimetry, the patterns of the degree and angle of polarization of the entire summer sky were measured on 25 June 1999 at a location north of the Arctic Circle in Finnish Lapland as a function of the angular solar zenith distance. A detailed description of the used full–sky imaging polarimeter and its calibration is given. A series of the degree and angle of polarization pattern of the full sky is presented in the form of high–resolution circular maps measured in the blue (450 nm) spectral range as a function of the solar zenith distance. Graphs of the spectral dependence of the degree and angle of polarization of skylight at 90° from the Sun along the antisolar meridian are shown. The celestial regions of negative polarization and the consequence of the existence of this anomalous polarization, the neutral points, are visualized. The measured values of the angular zenith distance of the Arago and Babinet neutral points are presented as a function of the zenith distance of the Sun for the red (650 nm), green (550 nm) and blue (450 nm) ranges of the spectrum. The major aim of this work is to give a clear and comprehensive picture, with the help of full–sky imaging polarimetry, of what is going on in the entire polarized skydome. We demonstrate how variable the degree of polarization of skylight and the position of the neutral points can be within 24 h on a sunny, almost cloudless, visually clear day.