Courses are an important way of cultivating talents in college education. Advanced training schemes and the course system are implemented through course teaching. Advanced teaching notions and methods also rely on course teaching. Therefore, the quality of course teaching is the fundamental guarantor for grooming talent. The teachers of the course “Microcontroller Principles and Interface Techniques” in the Optical Science and Engineering College of Zhejiang University insist on course teaching becoming student centered and ability-training–oriented. They pay attention to students’all-round development in terms of learning ability, practical ability, innovation ability, and exploring spirit. They actively carried out course reforms in four aspects, namely teaching, learning, evaluation, and experimentation. This paper mainly introduced these reforms. First, the teaching method was reformed by introducing case analysis and the notion of a flipped classroom to shift the course focus from the teacher to the students. Second, the learning method was reformed through the use of techniques such as peer learning and project design to promote students’ sense of enquiry and learning initiative. Third, the evaluation method was reformed through the use of process assessment and diversity evaluation to encourage students to develop logical thinking and a down-to-earth manner. Fourth, the experimentation method was reformed by introducing hierarchical content, process management, and diversification of examination to change students’learning attitude from “dependence, passivity, and imitation” to “independence, active involvement, and creation.”In general, the teaching method reform promoted reforms in learning, evaluation, and experimentation methods and further improved the style of study. These reforms improved teachers’ teaching abilities and enabled course teaching to transform from being teacher centered to student centered. Years of exploration and practice results have shown that such reforms not only effectively inspire students to learn, explore, and practice actively, but also cultivate their creative spirit and courage to face challenges, providing a good platform for theirself-learning and personal growth. The course reforms discussed here have been highly recommended for their reference value.
Traditional laser lithography systems cannot write sub-wavelength patterns due to the diffraction limit. In this paper, a novel super-resolution laser direct writing method is proposed to break through the diffraction limit. Compared with conventional lithography systems, the photoresist layer in this method is overlaid by an extra photochromic layer which is a mixture of metanil yellow and aqueous PVA solution. Then a vortex beam with a hollow energy distribution is used to expose the photochromic layer and make an annular region of the photochromic layer opaque to the writing beam. Thus, a virtual aperture is formed in the photochromic layer which can confine the diameter of the writing beam and reduce the linewidth exposed in the photoresist layer. Lithography process of this new method was modeled and a corresponding simulation was made. In this simulation, the intensity ratio of the two beams, relative absorption coefficients and other parameters were changed to study their influence to linewidth in the photoresist. An experimental setup was designed to validate the simulation, where the wavelengths of the writing beam and the vortex beam are 405 nm and 532 nm, respectively. These two beams are strictly coaxial when they are incident to the photochromic layer. The experimental results agree quite well with the model simulation, showing that the linewidth could be reduced by increasing the intensity ratio of the vortex beam to the writing beam. They also indicate that the vortex beam could effectively reduce the lithography linewidth to 300nm or even smaller.
In this paper, a method to detect internal pocks and bubbles of optical elements based on laser line
source scanning is proposed. In dark field environment, a laser line source is used to illuminate from
one side of the glass under test, a high-resolution CCD camera is used to take pictures in front of the
glass sample. Images which contain information of defects are acquired through rough scanning and
accurate scanning. Accurate three-dimensional coordinates of the internal defects are acquired after
image processing, which descript the characteristic information of internal defects quantificationally.
Compared with the microscope imaging measurement, this proposed detection of defects in optics
based on laser line source scanning has a relative aberration smaller than 2%. In addition, the detection
time is approximately reduced to 20 minutes from 1 hour dramatically. The analysis indicates that the
error of the position of defects is much smaller than the size of them, which means the position of the
defects can be acquired accurately by this approach.
A new approach called dynamic-scan-detection is presented to detect the focal spot on nonplanar surfaces, which is a key technique for laser direct writing on nonplanar surfaces. From the depth response properties of a confocal system on a nonplanar surface, the approach scans the axial shift of intensity response peak by oscillating the modified pinhole in the axial direction, and demodulates the defocus by measuring the length of time between two peaks of measured intensity waveform in one period. Compared with conventional methods, this approach features easy implementation, wide depth measurement range without deterioration of the depth discrimination property, dynamically adjustable scan amplitude, and more importantly, suppression of common-mode noise or variable system factors.
In this paper, a new method of calculating the diffraction efficiency for diffraction / refraction infrared hybrid system is
given. By using this method, an automatic measurement system is designed. This system covers the wavelength range of
1~3 μm, 3~5μm and 8~12μm. We use a blackbody as the energy source, put the lens which is to be measured above
a computer controlled turntable in order to gain different results in different filed of view. We also have several relay
lenses to cope with long or negative focal length. We use two types of detectors to deal with wavelength range of
1~3μm and 3~12μm .Both the detector and preamplifier are assembled together so we can easily change them for
different wavelength ranges. To improve the accuracy of the measurements, a new theory of measuring the main energy
is developed to minimize the negative impacts of other diffraction orders and the environment. We use an adjustable slit
cooperating with a two-axis stage to scan the focal point and by adjusting the width of the slit we can reduce the energy
of other diffraction orders and the environment that may come into our detector. During the experiment process we can
manually control the slit and two-axis stage to improve the efficiency and use our computer program to improve the
accuracy. The energy modulator and lock-in amplifier also help to improve the accuracy of our system. We designed two
standard lenses for the 3~5μm wavelength range. Both of them are made of the same material, have the same focal
length of 200mm and their shape is almost the same. The only difference between them is that one of them is pure
refraction piece which acts as a reference and the other one has a diffraction surface to achromatic aberration. The result
fits our theory well and the possible causes of the differences are discussed. This system has a practical meaning in the
quality evaluating of infrared hybrid system.
A new method based on confocal microscopy is presented to measure the distance between the focus of an objective lens
and the curved surface. The focus error signal based on this method is constructed. And this signal features not only the
possession of the linear relationship to the defocus, that is the distance between the focus of the objective lens and the
curved surface, and direction information of defocus and a wide measuring range, but also the independence of the tilt
angle of curved surface, the power fluctuation and the like.
An infrared hybrid refractive/diffractive optical system for 3 to 5μm band, which is composed of four refractive elements and one binary optical element (BOE), has been designed and manufactured. The BOE, whose chromatic behavior is opposite to that of the refractive element, has made it possible for us to design the diffraction limited optical system with field of 40× 40, aperture of 60mm, F number of 2.46, total track of 140mm and temperature range from minus 30°C~70°C. A polar coordinate laser direct writing system (PLDWS) and a reactive ion beam etching (RIBE) device have been established to manufacture the BOE. The imaging performance of our optical system has been tested by Ealing IR MTF equipment, which shows that the diameter of spot is less than 80μm when the energy within the spot is 90% of the total.