In order to meet the demands of high precision localization and anti-interference performance for optoelectronic
detection and imaging devices, a new subpixel edge detection approach based on orthogonal Pseudo-Zernike moments is
proposed in this paper with both theoretical analysis and experimental demonstration. First, the ideal step model of
subpixel edge is established, and the specific characteristics of edge points can be extracted through the convolution with
each order of Pseudo-Zernike moments. According to the principle of amplitude rotation invariance, the parameters of
subpixel edge can be obtained by analyzing the relationships between different orders and repetitions of Pseudo-Zernike
moments when the image edge is rotated to the vertical direction. And then the actual coordination of the subpixel edge
point can be identified. Comparing with other approaches such as spatial moment operators, and Zernike moment
algorithm, the experiment results prove that the proposed method has the virtue of higher measuring precision and better
noise suppression performance. The edge detection accuracy is up to 0.07 pixel for straight lines with noise, and 0.1 pixel
for curves with noise. Therefore, it can be concluded that the proposed method is an efficient approach with a relatively
high accuracy and stabilization for image edge detection.
In order to satisfy the requirements for the uniformity of infrared irradiance distribution and system energy efficiency, a
freeform surface reflector is designed in this paper. First of all, the model of the infrared light source is established,
basing on the shape of the actual light source and its radiation characteristics. Subsequently, a set of differential
equations are presented according to the desired irradiance distribution on the optical stop. Afterwards, the surfaces data
of the freeform reflector can be obtained by solve the equations using successive approximation method. Then the optical
ray-tracing simulation is done by using the Monte Carlo approach. And the allowance of the infrared system is analyzed;
the impacts that affect the simulation accuracy and the compensation process are also presented. The simulation results
indicate that the distribution uniformity of infrared irradiance characteristics on the optical stop is higher than 95%, and
the system energy efficiency reaches to 80%. Therefore, it can be concluded that the designed freeform surface reflector
is an efficient approach to meet the demands of the uniform illumination of infrared light source and system energy efficiency.
The laser spot determination is the critical technique in laser detecting systems. Due to atmospheric turbulence and other
factors, the laser spot intensity distributes unevenly in the long-distance measurement. In order to improve the location
precision of the laser spot detection, an improved sub-pixel algorithm based on Zernike moments is presented in this
paper with theoretical analysis. The experimental results of the proposed algorithm with CCD image test are also given
and compared with that of four conventional algorithms including gravity model, Hough transform, circle fitting, and
spatial moment operators. The comparative results demonstrate that the improved algorithm based on Zernike moments
has the virtue of higher measuring precision. The stability and interference suppression ability are also improved. The
proposed algorithm has already been applied into the processing of our laser detecting system, which can also play an
important role in automatic recognition, etc.
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