Ball lens

Abstract Thin and flexible probes made with hollow-optical fibers may be useful for remote spectroscopy. Experimental results showed that these probes are useful for endoscopic measurements of infrared and Raman spectroscopy. A hollow-fiber probe has been used for remote FT-IR spectroscopy in the form of endoscopic measurement of infrared reflectometry spectra inside the body. This measurement was made possible by the hollow-fiber probe s flexibility, durability, nontoxicity, and low transmission loss. A hoUow-fiber probe with a ball lens at the end works as a confocal system for Raman spectroscopy. It can thus detect the molecular structure of biotissues with a high signal-to-noise ratio. Owing to their small diameter, the probes are useful for in vivo, noninvasive analysis using a flexible endoscope. 

Figure 11 shows the appearance and structure of the focusing-lens cap using a ball lens attached to the end of a hoUow-hber. The diameter of the cap is small (i.e., 0.64 mm), so the hber with the cap is easily inserted into the working channel (whose inner diameter is usually larger than 1 mm) of a thin endoscope. 

Fig. 13 Intensity of Raman signal from silicon measured by using a hollow-fiber probe with a ball lens...

Figure 14 shows the Raman spectrum of a rat stomach measured ex vivo using the hollow-fiber probe. A spectrum taken by using a Raman microscope is also shown for comparison. The excitation power was 29 mW, and the exposure time for the measurement was 60 s. Although Raman peaks of the sapphire-ball lens at 630... 

Optical fiber, a ball lens, CCD detector Ca ions 0.027 mM [36]... 

Later, the same group developed what they call a hybrid microdevice as an alternative to quartz microchips. This device consisted of a short, fiised-sihca capillary column containing a 2.8-cm long polymer gel prepared from acrylamide, 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPS), and allyl- -cyclodextrin as crosslinker. This capillary was set in a groove on a polyvinyl chloride support plate that included sample reservoirs, electrodes, and a sht for on-tube UV-detection. In addition, a ball lens was mounted beneath the detection sht to focus the UV beam. Gel electrophoresis and electrochromatography were then performed in this system. For example, several alkyl phenones were separated in the electrochromatographic mode in less than 200 s. The suggested separation mechanism was related to interactions between the hydrophobie cavity of the P-eyelodextrin and the analytes. However, no direet evidence for this meehanism was presented. 

J. N. McMullin (Canada) Appl Photon Technol 2003 6 114 Multimode fiber core 1,000 pm, clad 1,200 pm NA = 0.50 material PMMA Green LED X = 570 nmred laser diode X = 640 nm Ball lens Fluorescence... 

J. N, MoMullln (Canada) AppI Photon Teohnol 2003 6 114 multimode fiber core 1000 pi,m, clad 1200 pi,m NA = 0.50 matarlal PMMA green LED X =hlOnm red laser diode X = 640nm ball lens fluorescence PMT... 

The advantages of a ball lens connection between optical fibers are schematically shown in Figure 7.8 in comparison with conventional direct butting. The output... 

Without ball lens vVith Dali lens... 

Figure 7.10 Reduction in coupling losses of Gl POF with ball lens under (a) axial and (b) longitudinal misalignment.

Fig. 2.4 Some spherical and aspheric discrete microlenses for optical concentrators in MWIR and LWIR range that may be fabricated by microsystem technologies, a calotte b hemisphere c hyperhemisphere d ball lens e truncated sphere f bulb g hemi-cylinder h cylinder i curvilinear cone j concave concentrator k gradient-index lens (GRIN) I complex two-element lens (sphere/GRIN). The grid corresponds to the homogeneity of refractive index, i.e., describes its gradient...

---