Monocular visual depth measurement technology has an excellent application prospect in the field of reconnaissance and detection in miniature unmanned systems. In this paper, a monocular depth perception method based on zoom image is studied. At first, the basic principle of monocular image depth perception is analyzed according to the geometric optics theory. On this basis, a depth measurement method that combines chain-code method to calculate target area is constructed: two different focal lengths are used to image the object and two independent sets of functions are listed according to the correspondence between the object distance and the focal length. The image area is used to replace the image point vector, and finally the depth of the object is solved. Then, the design and program compilation of monocular zoom measurement algorithm are realized and the measurement accuracy of the algorithm is preliminarily verified by experiments. Finally, three sets of test experiments are designed with the target distance, focal length ratio and target size as parametric variables. The experimental results show that the measurement accuracy of this algorithm appears a downward trend with the decrease of the target size and the increase of the distance, while the monocular zoom measurement can obtain higher accuracy under the condition of large focal length ratio. The research results can provide technical and theoretical basis for the realization of high-performance monocular depth measurement.
With the continuous development of micro-unmanned system technology, the application requirements of small, lightweight and range-measuring are put forward for the mounted vision module. First of all, this paper proposes a monocular ranging method based on small liquid lens focusing, the position of the equivalent principal plane of the imaging system and the relationship between the equivalent focal length and the voltage of the liquid lens are deduced. Then, combined with the image focusing algorithm and the Gaussian optical imaging theory, establishing a nonlinear mapping model between the distance information of the target and the control voltage value of the liquid lens. Finally, the monocular ranging experiment is designed with the optical imaging system of liquid-solid lens combination as the hardware platform. The results show that the monocular ranging error based on the liquid adjustable focus lens can be controlled within 1mm, so the method proposed in this paper is feasible and can meet the visual ranging requirements of micro-unmanned systems.
As a new type of zoom element, the liquid lens has the characteristics of fast response, no wear, and small size, which brings new ideas to the design of the zoom system. This paper proposes a liquid-solid composite zoom optical system without mechanical movement. In the system, two liquid lenses are used as the zoom group and the compensation group of the system, so that the image plane position is always stable during the zooming process of the system. Based on the Gaussian theory, the relationship between the focal length of the system and the focal length of a single liquid lens is derived, and a multi-layer traversal algorithm is proposed to solve the initial structure parameters of the system. The optimized design of the zoom optical system and image quality analysis was completed by using ZEMAX software. The results show that the system can achieve continuous zoom in the range of 20-60mm, the zoom ratio of the system is 3, and the image quality is good. The modulation transfer function of each focal length of the zoom system at a spatial frequency of 50lp/mm is greater than 0.2, and the RMS value of wave aberration is greater than 0.3 times the wavelength of the probe light, which meets the design requirements.
Computer-generated hologram (CGH) is an important component for high-precision aspherical surface testing. This paper puts forward a manufacturing method of amplitude-type CGH by femtosecond laser direct etching, and carries out detailed analysis and demonstration. Firstly, the demand of microstructure fabrication of amplitude-type CGH was analyzed by optical diffraction theory. Furthermore, we have established the theoretical model of femtosecond laser machining amplitude-type CGH fringe. Finally, we developed basic verification experiments, and analyzed the feasibility of fabricating CGH by direct etching process based on the testing results of processing fringe characteristics.
Inductively coupled plasma processing (ICPP) is regarded as an unrivaled technique in the field of aspheric and freeform optics fabrication for its non-contact chemical etching and high efficiency. In this paper, to evaluate the obliquely incident machining behavior of removal function during inductively coupled plasma, we did some plasma beam line scanning test treatments on the fused silica surface with different obliquely incident angles in two vertical directions. Test results show that the full width at half maximum (FWHM) of the footprint of removal function increases from 13.1699 mm to 14.8368 mm with the increase of the obliquely incident angle from 0° to 30° along the X-direction line scanning processing, and that of another direction only increases from from 13.1699 mm to 14.0598 mm. Furthermore, the material removal rate in both directions reduces in a small range with the increase of the obliquely incident angle less than 10° under our processing condition. Therefore, test results demonstrate that the three-axis machining system can be effective supposing that the local slopes of the part to treat are less than about 10°. The presented conclusions can provide technical guidance for fused silica aspheric and free-form optical surface machining.
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