Better ground sampling distance (GSD) has been a trend for earth observation satellites. A long-focal-length telescope is required accordingly in systematic point of view. On the other hand, there is size constraint for such long-focal-length telescope especially in space projects. Three-mirror-anastigmat (TMA) was proven to have excellent features of correcting aberrations, wide spectral range and shorter physical requirement [1-3].
Collimator is popular used in optical testing in laboratory to simulate target in a distance. Glass plate with pattern is fundamental constitute of collimator focal plane, which should be placed precisely with respect to its optics. For collimator in used or to be built, it is necessary to check position of its focal plane. We develop a fast method to check focal plane position with interferometer. Results derived from this method are compared with that derived from angle deviation measurement method. Meanwhile, focal plane adjustment of imaging telescope can be performed with same way.
3D printing is a high freedom fabrication technique. Any components, which designed by 3D design software or scanned from real parts, can be printed. The printing materials include metals, plastics and biocompatible materials etc. Especially for those high transmission components used in optical system or biomedical field can be printed, too. High transmission lens increases the performances of optical system. And high transmission cover or shell using in biomedical field helps observers to see the structures inside, such as brain, bone, and vessels. But the surface of printed components is not transparent, even the inside layer is transparent. If we increase the transmittance of surface, the components which fabricated by 3D printing process could have high transmission. In this paper, we using illuminating and polishing methods to improve the transmittance of printing surface. The illuminating time is the experiment parameters in illuminating method. The roughness and transmission of printing components are the evaluating targets. A 3D printing machine, Stratasys Connex 500, has been used to print high transmittance components in this paper. The surface transmittance of printing components is increasing above 80 % by polishing method.
Direct imaging has widely applied in lithography for a long time because of its simplicity and
easy-maintenance. Although this method has limitation of lithography resolution, it is still adopted in
industries. Uniformity of UV irradiance for a designed area is an important requirement. While
mercury lamps were used as the light source in the early stage, LEDs have drawn a lot of attention for
consideration from several aspects. Although LED has better and better performance, arrays of LEDs
are required to obtain desired irradiance because of limitation of brightness for a single LED. Several
effects are considered that affect the uniformity of UV irradiance such as alignment of optics,
temperature of each LED, performance of each LED due to production uniformity, and pointing of
LED module. Effects of these factors are considered to study the uniformity of LED Light Illumination.
Numerical analysis is performed by assuming a serious of control factors to have a better understanding
of each factor.
This paper proposes a newly developed fast measure of MTF optical system inclusive of on axis and off-axis. Firstly, we discusses how a description of an imager in terms of its optical transfer function is not appropriate for discrete imaging system when aliasing occurs, since these optical systems transform high spatial frequencies into low frequencies; then measure how efficient microscanning method could remove the aliasing effects from assigned telecentric optics and non-telecentric optics. Knife edge and slit function as a light source is employed in this measurement. Experiment with newly-designed MTF measurement system synchronizes on axis and off-axis measurement. In addition, micro-scan method with specially written macro is introduced in this experiment to eliminate aliasing effects. After simulation and experimental analysis, first, slit function as a target deliver decent MTF repeatability for this newly developed MTF measurement system which synchronize with on axis and off-axis measurement simply in two seconds after all equipment is ready and aligned. Secondly, after six step microscanning, aliasing will be eliminate to near zero in most cases. Finally, it is concluded that during microscan, there is no difference between telecentric and non-telecentric optics.
The conventional measurements of the speed of light were performed before the early twentieth century. Only few used extraterrestrial sources and got the result with large uncertainty. We design a transmitter to modulate the rays from the local infrared light source and the extraterrestrial sources simultaneously into pulses. Both are received by a distant receiver. We have the white light travelling exactly along the path of the starlight pulses for calibration. It is found that the travel times of Aldebaran and Capella pulses are longer than that of Vega pulses. The results indicate that the speeds of starlights are different.
Bar chart patterns projects by collimator was adopted to measure contrast transfer function (CTF)values at Nyquist frequency before assembly of imaging sensor with telescope for earth-observing pushbroom imager. A relay imaging probe consisting of optical objective and 2D imaging sensor was builded to image these projected pattern and estimate the image quality of optical system before alignment of linear imaging sensor. By riding on a hexapod stage and measuring at a series focus position at several field angles, this probe provides a reference map for alignment of imaging sensor and image quality assessment. Certainly, testing result can be used to anticipate result of focusing alignment.
For a currently developing multispectral space Cassegrain telescope, the primary mirror with 450 mm clear aperture is
made of Zerodur and lightweighted at a ratio about 50 % to meet both thermal and mass requirement. For this mirror, it
is critical to reduce the astigmatism caused from the gravity effect, bonding process and the deformation from the
mounting to the main structure of the telescope (main plate). In this article, the primary mirror alignment, MGSE,
assembly process and the optical performance test for the primary mirror assembly are presented. The mechanical shim
is the interface between the iso-static mount and main plate. It is used to compensate the manufacture errors of
components and differences of local co-planarity errors to prevent the stress while iso-static mount (ISM) is screwed to
After primary mirror assembly, an optical performance test method called bench test with novel algorithm is used to
analyze the astigmatism caused from the gravity effect and the deformation from the mounting or supporter. In an effort
to achieve the requirement for the tolerance in primary mirror assembly, the astigmatism caused from the gravity and
deformation by the mounting force could be less than P-V 0.02λ at 633 nm. The consequence of these demonstrations indicates that the designed mechanical ground supported equipment (MGSE) for the alignment and assembly processes meet the critical requirements for primary mirror assembly of the telescope.
The speed of light is an important physical parameter. Currently it is a common belief of the constance of the speed of light regardless of the relative velocity between the source and the observer. Because the speed of light is very fast, if the relative velocity is small compared with the speed of light, it is difficult to detect the effect of the relative velocity on the measurement of the speed of light. In this paper we present a method of comparing the speeds of starlight and the light emitting from a terrestrial source. We use a telescope to collect the light from the star having significant relative velocity with respect to the earth, e.g. Capella. Then we modulate the starlight and the light emitted from the local source into pulses i.e. these pulses leave the modulator simultaneously. After travelling 4.2 km, these pulses are detected by a receiver. If the starlight and the terrestrial light have the same speed, then these pulses must arrive at the receiver at the same time. Our results show that the arrival times of the pulses of starlight are different from that of the local light. For example, the Capella is leaving away from the earth. The Capella pulses arrive later than the local light pulses. It indicates that the speed of Capella starlight is slower than the common believed value, c. The presented method uses one clock and one stick, so the clock synchronization problem and any physical unit transformation can be avoided.
In order to give consideration to both resolution and swath of airborne remote sensing instrument, pan-sharpening
method was used to get high resolution pan-sharpened image. This research provides a description of the optomechanical
system design and assembly of airborne imager, VCDi-660 (Vegetation and Change Detection imager).
Opto-mechanical components of VCDi-660 consist of six optical lenses, focal plane adjustment, bore sight alignment
adjustment, filter-exchanging mechanical device and circuit protected housing. An improved adjustment device for bore
sight alignment of the multiple-band camera in this Taiwanese airborne imaging sensor, VCDi-660, has been presented.
Target of this mechanical device is to provide a translational and rotational movement in the focal plane of VCDi-660.
Sensor can be aligned into the best focal position, thus the central point deviations for individual camera module can be
less than 3 pixels in both axes in image after alignment.