After several changes over the past two years, mid-Infra Red (IR) spectral band 3-4µm has been decided to use for LAPAN's IR camera module. Moreover, the IR camera only will equip with one microbolometer as the detector. The peat fire and Indonesia's volcano activities are two major missions of this experimental IR camera.
Applying the generally used design process including the trade-off, the LAPAN's IR camera module has been made. Optical analysis as the initial step has been laid a solid foundation for subsequent process. A commercial process, in this cases Zemax, plays an important role during this design process. Meanwhile, mechanical design, the second step of designing, includes the structure / thermal analysis as well. Structure/Thermal analysis basically is to ascertain whether the LAPAN's IR camera module meets all the performance or not when operating in harsh condition. Once again, the commercial software, Thermal Desktop/Sinda Fluint, and Solidworks have been utilized for the analysis and design process. Electrical design as the last procedure is the least process done due to limited time.
The spot diagram, encircled energy, and MTF graph shows that design of our refractive lens including the selected material meet the performance requirement. The natural frequencies as the mechanical analysis result indicate that our mechanical design is on the track. Meanwhile, for structure/thermal problem, the analysis tells the LAPAN's IR camera module will work well in space environment as well. Furthermore, the electrical design provides a good enough interface between the FPA detector and the electronics
Besides the wavelength used, there is another factor that we have to notice in designing an optical system. It is material used which is correct for the spectral bands determined. Basically, due the limitation of the available range and expensive, choosing and determining materials for Infra Red (IR) wavelength are more difficult and complex rather than visible spectrum. We also had the same problem while designing our thermal IR camera equipped with two microbolometers sharing aperture. <p> </p>Two spectral bands, 3 - 4 μm (MWIR) and 8 - 12 μm (LWIR), have been decided to be our thermal IR camera spectrum to address missions, i.e., peat land fire, volcanoes activities, and Sea Surface Temperature (SST). Referring those bands, we chose the appropriate material for LAPAN's IR camera optics. This paper describes material of LAPAN's IR camera equipped with two microbolometer in one aperture. <p> </p>First of all, we were learning and understanding of optical materials properties all matters of IR technology including its bandwidths. Considering some aspects, i.e., Transmission, Index of Refraction, Thermal properties covering the index gradient and coefficient of thermal expansion (CTE), the analysis then has been accomplished. Moreover, we were utilizing a commercial software, Thermal Desktop/Sinda Fluint, to strengthen the process. Some restrictions such as space environment, low cost, and performance mainly durability and transmission, were also cared throughout the trade off the works. The results of all those analysis, either in graphs or in measurement, indicate that the lens of LAPAN's IR camera with sharing aperture is based on Germanium/Zinc Selenide materials.
As new player in Infra Red (IR) sector, uncooled, small, and lightweight IR Micro Bolometer has been chosen as one of
payloads for LAPAN’s next micro satellite project. Driven the desire to create our own IR Micro Bolometer, mission
analysis design procedure has been applied. After tracing all possible missions, the Planck’s and Wien’s Law for black
body, Temperature Responsivity (TR), and sub-pixel response had been utilized in order to determine the appropriate
spectral radiance. The 3.8 – 4 μm wavelength were available to detect wild fire (forest fire) and active volcanoes, two
major problems faced by Indonesia. In order to strengthen and broaden the result, iteration process had been used
throughout the process. The analysis, then, were continued by calculating Ground pixel size, IFOV pixel, swath width,
and focus length. Meanwhile, regarding of resolution, at least it is 400 m.
The further procedure covered the integrated of optical design, wherein we combined among optical design software,
Zemax, with mechanical analysis software (structure and thermal analysis), such as Nastran and Thermal Desktop /
Sinda Fluint. The integration process was intended to produce high performance optical system of our IR Micro
Bolometer that can be used under extreme environment. The results of all those analysis, either in graphs or in
measurement, show that the initial design of LAPAN’S IR Micro Bolometer meets the determined requirement.
However, it needs the further evaluation (iteration). This paper describes the initial design of LAPAN’s IR Micro
Bolometer using mission analysis process
We have since 2 years ago been doing a research in term of an IR Micrometer Bolometer which aims to fulfill our office, LAPAN, desire to put it as one of payloads into LAPAN’s next micro satellite project, either at LAPAN A4 or at LAPAN A5. Due to the lack of experience on the subject, everything had been initiated by spectral radiance analysis adjusted by catastrophes sources in Indonesia, mainly wild fire (forest fire) and active volcano. Based on the result of the appropriate spectral radiance wavelength, 3.8 – 4 μm, and field of view (FOV), we, then, went through the further analysis, optical analysis. Focusing in illumination matter, the process was done by using Zemax software. Optical pass Interference and Stray light were two things that become our concern throughout the work. They could also be an evaluation of the performance optimization of illumination analysis of our optical design. The results, graphs, show that our design performance is close diffraction limited and the image blur of the geometrical produced by Lapan’s IR Micro Bolometer lenses is in the pixel area range. Therefore, our optical design performance is relatively good and will produce image with high quality. In this paper, the Illumination analysis and process of LAPAN’s Infra Red (IR) Micro Bolometer is presented.