Kimio Tatsuno

Athermal design and analysis of glass-plastic hybrid lens

With the rapid development of security market, the glass-plastic hybrid lens has gradually become a choice for the special requirements like high imaging quality in a wide temperature range and low cost. The reduction of spherical aberration is achieved by using aspherical surface instead of increasing the number of lenses. Obviously, plastic aspherical lens plays a great role in the cost reduction. However, the hybrid lens has a priority issue, which is the large thermal coefficient of expansion of plastic, causing focus shift and seriously affecting the imaging quality, so the hybrid lens is highly sensitive to the change of temperature. To ensure the system operates normally in a wide temperature range, it is necessary to eliminate the influence of temperature on the hybrid lens system. A practical design method named the Athermal Material Map is summarized and verified by an athermal design example according to the design index. It includes the distribution of optical power and selection of glass or plastic. The design result shows that the optical system has excellent imaging quality at a wide temperature range from -20 ℃ to 70 ℃. The method of athermal design in this paper has generality which could apply to optical system with plastic aspherical surface.

Design of a continuously zoom optical system

With the majority needs of the various observation, such as the public security system including security and traffic monitoring system, we can use the optical system, which can not only satisfy the wide field observation, also meet the needs of monitoring. The continuous zoom optical system, which can realize the wide field of monitoring and remain off the accurate detection would meet the requirements.

Realization of surface plasmon polaritons by Fresnel diffraction

When a part of an optical wave-front experiences a sharp change in its phase, Fresnel diffraction becomes appreciable. Sharp change in phase occurs as a wave-front reflects from a surface with an abrupt change in reflectivity. We apply this concept to a modified Kretschmann configuration for coupling surface plasmon. In Kretschmann configuration a metal film is placed at the interface of two dielectric media. First medium with higher refractive index is a prism and second medium with lower refractive index can be the air or the solutions of interest. But, in our modified configuration, the metal film is coated only on one half of a specified face of the prism. When a parallel-polarized light travels from the higher refractive index medium to the lower refractive index medium with an angle θ<θc, where θc is the critical angle, the total internal reflection can take place within first medium. Subsequently, enhanced evanescent waves, namely surface plasmons are confined to the metal–dielectric interface. In this case, the total internal reflection amplitude decreases at the half section covering the metal film. Therefore, the Fresnel diffraction fringes are formed due to abrupt change of the reflection amplitude. We measure the visibility of the diffraction fringes versus wavelength of the incident light, for while, we get the maximum visibility. This wavelength is corresponding to the surface plasmon resonance. We present the technique by theory and experiment.

Shack-Hartmann reflective micro profilometer

We present a quantitative phase imaging microscope based on a Shack-Hartmann sensor, that directly reconstructs the optical path difference (OPD) in reflective mode. Comparing with the holographic or interferometric methods, the SH technique needs no reference beam in the setup, which simplifies the system. With a preregistered reference, the OPD image can be reconstructed from a single shot. Also, the method has a rather relaxed requirement on the illumination coherence, thus a cheap light source such as a LED is feasible in the setup. In our previous research, we have successfully verified that a conventional transmissive microscope can be transformed into an optical path difference microscope by using a Shack-Hartmann wavefront sensor under incoherent illumination. The key condition is that the numerical aperture of illumination should be smaller than the numerical aperture of imaging lens. This approach is also applicable to characterization of reflective and slightly scattering surfaces.

The optical design and simulation of the collimated solar simulator

The solar simulator is a lighting device that can simulate the solar radiation. It has been widely used in the testing of solar cells, satellite space environment simulation and ground experiment, test and calibration precision of solar sensor．The solar simulator mainly consisted of short—arc xenon lamp, ellipsoidal reflectors, a group of optical integrator, field stop, aspheric folding mirror and collimating reflector. In this paper, the solar simulators optical system basic size are given by calculation. Then the system is optically modeled with the Lighttools software, and the simulation analysis on solar simulator using the Monte Carlo ray -tracing technique is conducted. Finally, the simulation results are given quantitatively by diagrammatic form. The rationality of the design is verified on the basis of theory.

Simulation of aspheric tolerance with polynomial fitting

The shape of the aspheric lens changes caused by machining errors, resulting in a change in the optical transfer function, which affects the image quality. At present, there is no universally recognized tolerance criterion standard for aspheric surface. To study the influence of aspheric tolerances on the optical transfer function, the tolerances of polynomial fitting are allocated on the aspheric surface, and the imaging simulation is carried out by optical imaging software. Analysis is based on a set of aspheric imaging system. The error is generated in the range of a certain PV value, and expressed as a form of Zernike polynomial, which is added to the aspheric surface as a tolerance term. Through optical software analysis, the MTF of optical system can be obtained and used as the main evaluation index. Evaluate whether the effect of the added error on the MTF of the system meets the requirements of the current PV value. Change the PV value and repeat the operation until the acceptable maximum allowable PV value is obtained. According to the actual processing technology, consider the error of various shapes, such as M type, W type, random type error. The new method will provide a certain development for the actual free surface processing technology the reference value.

The novel support structure design of high stability for space borne primary reflector

The novel support structure design of high stability for space borne primary mirror is presented. The structure is supported by a ball head support rod, for statically determinate support of reflector. The ball head assembly includes the supporting rod, nesting, bushing and other important parts. The liner bushing of the resistant material is used to fit for ball head approximated with the reflector material, and then the bad impact of thermal mismatch could be minimized to minimum. In order to ensure that the structure of the support will not be damaged, the glue spots for limitation is added around the reflector, for position stability of reflector. Through analysis and calculation, it can be seen that the novel support structure would not transfer the external stresses to the reflector, and the external stresses usually result from thermal mismatch and assembly misalignment. The novel method is useful for solving the problem of the bad influence form thermal stress and assembly force. In this paper, the supporting structure is introduced and analyzed in detail. The simulation results show that the ball head support reflector works more stably.

A method based on analytical expression to study echo laser pulse

The integrated model of echo laser pulse (ELP) of a target with arbitrary shape is studied under the condition of the ELP affected by target and atmospheric turbulence simultaneously. The ELPs of two typical targets (a plane and an aspherical surface) are employed to test the validity of the model by analytical expression. Based on simulations of the ELP under different targets and atmospheric turbulence intensity, the results show the ELP of a target with complicated surface is more easily affected by atmospheric turbulence than that with simple surface. Besides that, we study the relationship between the number of grids and the relative error of analytical expression, which is of interest to obtain the optimal number of grids used in the simulations.

The design research of the test support structure for a large-diameter main mirror

The accuracy of the main mirror surface shape measurement on ground is vital because of the importance of the main mirror in a optical remote sensor. Generally speaking, the main effects of the mirror surface shape measurement accuracy are due to the optical measurement system and support structure. The aim of this thesis is researching the design of the mirror shape measurement support structure. The main mirror discussed in this paper equipped with 650mm diameter. The requirements of PV and RMS for surface shape are no more than 0.136λ and 0.017λ respectively while λ is determined as 632.8nm. At present, the on ground adjustment methods of camera lens are optical axis horizontal and gravity discharging. In order to make the same condition between camera lens adjustment and main mirror operating, the surface shape measurement of main mirror should keep optical axis horizontal condition for mirror either. The support structure of the mirror introduced in this paper is able to extremely reduce the surface shape distortion caused by the effects of support structure mostly. According to the simulating calculation, the variation of main mirror surface shape is no more than 0.001λ. The result is acceptable for camera adjustment. Based on the measurement support structure mentioned before, the main mirror could rotate 360-degree under the condition of optical axis horizontal; the four-direction measurement for mirror is achieved. Eliminate the effects of ground gravity for surface shape measurement data, the four-direction mirror shape error is controlled no more than 0.001λ on this support structure which calculated by simulation.

A novel automotive headlight system based on digital micro-mirror devices and diffractive optical elements

The DMD (Digital Micro-mirror Device) has the advantages of high refresh rate and high diffraction efficiency, and these make it become an ideal loader of multiple modes illumination. DOEs (Diffractive Optical Element) have the advantages of high degree of freedom, light weight, easy to copy, low cost etc., and can be used to reduce the weight, complexity, cost of optical system. A novel automotive headlamp system using DMD as the light distribution element and a DOE as the light field modulation device is proposed in this paper. The pure phase DOE is obtained by the GS algorithm using Rayleigh-Sommerfeld diffraction integral model. Based on the standard automotive headlamp light intensity distribution in the target plane, the amplitude distribution of DMD is obtained by numerical simulation, and the grayscale diagram loaded on the DMD can be obtained accordingly. Finally, according to simulation result, the light intensity distribution in the target plane is proportional to the national standard, hence verifies the validity of the novel system. The novel illumination system proposed in this paper provides a reliable hardware platform for the intelligent headlamps.