The development of techniques to rapidly identify samples ranging from, molecule and particle imaging to detection of high explosive materials, has surged in recent years. Due to this growing want, Raman spectroscopy gives a molecular fingerprint, with no sample preparation, and can be done remotely. These systems can be small, compact, lightweight, and with a user interface that allows for easy use and sample identification. Ocean Optics Inc. has developed several systems that would meet all these end user requirements. This talk will describe the development of different Ocean Optics Inc miniature Raman spectrometers. The spectrometer on a phone (SOAP) system was designed using commercial off the shelf (COTS) components, in a rapid product development cycle. The footprint of the system measures 40x40x14 mm (LxWxH) and was coupled directly to the cell phone detector camera optics. However, it gets roughly only ~40 cm-1 resolution. The Accuman system is the largest (290x220X100 mm) of the three, but uses our QEPro spectrometer and get ~7-11 cm-1 resolution. Finally, the HRS-30 measuring 165x85x40 mm is a combination of the other two systems. This system uses a modified EMBED spectrometer and gets ~7-12 cm-1 resolution. Each of these units uses a peak matching algorithm that then correlates the results to the pre-loaded and customizable spectral libraries.
A miniature Raman spectrometer was designed in a rapid development cycle (< 4 months) to investigate the performance capabilities achievable with two dimensional (2D) CMOS detectors found in cell phone camera modules and commercial off the shelf optics (COTS). This paper examines the design considerations and tradeoffs made during the development cycle. The final system developed measures 40 mm in length, 40 mm in width, 15 mm tall and couples directly with the cell phone camera optics. Two variants were made: one with an excitation wavelength of 638 nm and the other with a 785 nm excitation wavelength. Raman spectra of the following samples were gathered at both excitations: Toluene, Cyclohexane, Bis(MSB), Aspirin, Urea, and Ammonium Nitrate. The system obtained a resolution of 40 cm-1. The spectra produced at 785 nm excitation required integration times of up to 10 times longer than the 1.5 seconds at 638 nm, however, contained reduced stray light and less fluorescence which led to an overall cleaner signal.
Color is an important metric for determining the quality of petroleum products, as it is a characteristic readily observed by operators and end users and can also be indicative of the degree of refinement of a petroleum product. There are two primary color standards covering a wide range of petroleum color in industry; ASTM D 156 (Saybolt Color Scale) and ASTM D 1500 (ASTM Color Scale). For highly refined petroleum products the industry uses the Saybolt color scale, ranging from 30 at the clearest to -16 at the darkest. Fuels that are darker in color than -16 on the Saybolt scale are tested using the ASTM Color scale, which ranges from 0.5 at the clearest to 8 at the darkest. As fuels age (increased time from the point of refinement), their color darkens because of oxidizing olefins, such as ethylene and propylene. Traditionally, this color scale is measured using a series of photodiodes and optical filters with a blackbody light source. The spectroscopic method described in this paper incorporates a white LED designed for maximizing color measurements. The spectra are processed using CIE 1931 color space, which is then converted into CIELab color space. Results using this method are accurate and repeatable.
Precision glass molding (PGM) directly into metallic structures is a process similar to the plastic injection molding
process of insert molding, however fundamental differences exist due to the processing temperatures, nature of materials
and manufacturing requirements. Despite some limitations, insert precision glass molding (IPGM) extends many benefits
to the product designer. IPGM occurs at the glass transition temperature of the glass therefore materials must be matched
by their thermal properties so that undue stress is not exerted on the glass during processing or significant inherent stress
left in the part after processing. Either of these conditions could lead to cracking, birefringence or failures due to thermal
cycling during operation. This paper will discuss the techniques and specific design considerations that must be taken
into account when designing for IPGM. Design aspects such as interface diameters, wall thicknesses, aspect ratios and
material properties will be analyzed. The optical and mechanical performance and properties of the glass and holder
assembly will also be reviewed, including strength of the assembly, quality of the sealing interface (hermeticity), optical
to mechanical alignment and impact on optical quality. The review includes both chalcogenide and traditional oxide
based moldable glasses.