In the micro-nano structure manufacturing field, large field of view, flexibility, and single exposure are the advantages of laser interference lithography. However, this method can only produce periodic patterns. In this paper, laser interference lithography and optical field modulation techniques are combined. By adjusting the parameters such as the phase and amplitude of the incident light beam, a light field modulation interference model was constructed to study the relationship between the parameters of the incident light beam and the intensity distribution of the interference light field. We verified the feasibility of the method through simulation. Considering the performance of existing optical modulation devices such as the pixel size of spatial light modulators, we discuss the challenges of this approach and the actual resolution that can be achieved. There is no doubt that this provides a new direction for the preparation of multiscale, variable period micro-nano patterns.
Unlike traditional imaging, the light field imaging can obtain location and direction information by one shot, which makes the dynamic three-dimensional shape measurement possible. Firstly, this paper establishes a pixel light field model, and calibrates the measurement system, which lays the foundation for light field refocus. Then proposes light field 3-D shape measurement method based on digital focus distance measurement and appropriate sharpness evaluation function. Meanwhile, hardware module used in dynamic three-dimensional shape measurement based on light field imaging is designed, which is responsible for real-time collection and processing of the light field images and greatly improves the reconstruction speed of the images. Finally achieve light field 3-D shape measurement. The experimental results are present to demonstrate the feasibility of this technique.
Proc. SPIE. 9685, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; and Smart Structures and Materials
KEYWORDS: Lithography, Control systems, Semiconducting wafers, Clocks, Photomasks, Process control, Stepper motor drivers, Data communications, Telecommunications, Camera shutters
Three-dimensional wafer stage is an important component of lithography. It is required to high positioning precision and efficiency. The closed-loop positioning control system, that consists of five-phase step motor and grating scale, implements rapid and precision positioning control of the three-dimensional wafer stage. The MCU STC15W4K32S4, which is possession of six independent PWM output channels and the pulse width, period is adjustable, is used to control the three axes. The stepper motor driver and grating scale are subdivided according to the precision of lithography, and grating scale data is transmitted to the computer for display in real time via USB communication. According to the lithography material, mask parameter, incident light intensity, it's able to calculate the speed of Z axis, and then get the value of PWM period based on the mathematical formula of speed and pulse period, finally realize high precision control. Experiments show that the positioning control system of three-dimensional wafer stage can meet the requirement of lithography, the closed-loop system is high stability and precision, strong practicability.
In this paper we analyze the change of polarization state for a laser optical system which includes a Cassegrain beam expander and several fold mirrors. First, this system operates over a broad spectral band and is with several separated wavelengths, therefore, strong polarization effects will occur at certain waveband. The polarization state changes of different wavelengths at the exit pupil are discussed mainly based on the comparison of their Point Spread Function (PSF) and Strehl Ratio respectively. Then, fold mirrors cause large angles of incidence and can rotate in azimuth and zenith. The amplitude diattenuation and retardance are calculated at different azimuth and zenith of the beam director assembly. In this paper, Code-V commercial optical-engineering software is used to model the polarization behavior for the system. The factors mentioned above, which are spectral bandwidth, angle of incidence of surfaces and systemic coatings, are taken into consideration in the process of simulation. The result of the study shows that the polarization properties at certain wavelength are satisfactory except some other wavelengths are not. This laser system is more sensitive to retardance than to diattenuation. It is concluded that polarization is an important factor that affects the performances of the whole system and the design of laser optical system should take into account the polarization effects.
A novel PSD-based Hartmann-Shack wavefront sensor (HSWFS) prototype has been developed, which employs a 4X4 PSD array as the detector to measure the displacements of the sub-aperture spots. Compared with the conventional CCD-based HSWFS, it can operate at very high sampling rate, and it only has very short readout delay time. Our system can measure wavefront at frame rate up to 5KHz, and the detected wavefront error is less than λ/50 (λ=632.8<i>nm</i>). In this paper the experimental results are given. The measurement error of the PSD-based HSWFS for a given aberrated plate is compared with the measure result of the Zygo interferometer.
A novel PSD-based Hartmann-Shack wavefront sensor(HSWFS) prototype has been developed. Compared with the conventional CCD-based HSWFS, it can operate at very high sampling rate, and it only has very short readout delaytime. In this paper, the PSD-based HSWFS is described in details, and the performances of the PSD-based HSWFS and the CCD-based HSWFS are compared.