Filters, optical neutral density

Figure 6 (A) A fibre optic probe for reflectometry. The light scattered from a single excitation fibre is detected by a linear array of collection fibres. Tilting the excitation fibre shifts the profile along the surface by an amount that is determined by the sample s optical properties. (B) A fibre optic probe with a circular fibre arrangement for reflectometry. A 2 cm probe head consist of a central calibration fibre, an excitation fibre and non-equally spaced fibres. Neutral density (ND) filters adapt the light intensity in a transfer array to a smaller dynamic range.

To determine optical damage in bulk benzil crystals a Q-switched Nd YAG laser with 1KW peak power, pulse width of 0.1 ps and pulse repetition rate of 500Hz was used. The laser power was attenuated using a set of neutral density filters and focussed onto a bulk benzil crystal using a x10 microscope objective. No optical damage was observed with optical intensities of upto 100MW/cm - Also, no optical damage was observed in benzil cored fibres with similar optical intensities. 

The initiation system consists of a nitrogen laser and the necessary optics to lead the beam to the sample cell. The laser emits pulses at 337.1 nm with 800 ps duration, with a typical repetition rate of less than 5 Hz. The optical components, aligned between the laser and the calorimetric cell, consist of an iris (I), a support for neutral density filters (F), and a collimating lens (L). The iris is used to cut out most of the laser output and allow only a thin cylinder of light to pass through its aperture, set to 2 mm. The laser energy that reaches the cell is further... 

Pt acts like a neutral density filter through a wide wavelength range and can be used in the UV when the film is on quartz. Au has an optical window with maximum transmission at 540 nm. On quartz, Au can also be used in the UV when the conductivity is comparable to Pt. For the visible region, Au films with good transmission and with resistance as low as a few ohms per square can be prepared. Typical optical properties are shown in Figure 11.3 [55]. The electrochemical properties are similar to bulk Pt and Au, as seen in Figure 11.5 [74],... 

Figure 8 Schematic of the optical system used to perform the Raman FID and echo experiments. P = Polarizer (D)BS = (dichroic) beamsplitter MD = manual delay line SD = computer-scanned delay line CSA = charge sensitive amplifier CH = chopper PH = pinhole S = sample F = bandpass and neutral density filters PD = photodiode A/D = analog-to-digital converter PC = computer PMT = photomultiplier X/2 = half-wave plate. (From Ref. 6.)...

Attenuance filter An optical device (filter) which reduces the radiant power of a light beam by a constant factor over all wavelengths within its operating range. Sometimes called attenuator or neutral density filter. 

Filter optical) A device which reduces the spectral range (bandpass, cut-off, and interference filter) or radiant power of incident radiation (neutral density or attenuance filter) upon transmission of radiation. 

Bathypho tome ter Detector. The submersible system, which employs the same basic approach of pumping seawater past a PMT, also consisted of an RCA 8575 PMT used in the photon count mode, a filter-wheel disc with a capacity for carrying 20 optical filters, a temperature thermistor, a beam transmissometer, and a depth sensor. The central wavelengths of the optical filters used were 360, 370, 380, 390, 400, 420, 440, 460, 480, 500, 520, 540, 650, 580, 600, 620, and 640 nm. Neutral-density filters of varying attenuation powers complemented the filter set, and all components were contained in an aluminum pressure housing (Figure 2). 

Light modulation devices such as acousto-optic modulators (AOM) or neutral density filters to provide attenuation for the excitation source. 

Instrumentation. Steady-state fluorescence spectra were obtained on an SLM-Aminco SPF-500 spectrofluorometer equipped with an LX300 UV illuminator, a 1200-grooves per millimeter grating, and a Hamamatsu R 928P photomultiplier tube in conjunction with a Zenith Z-368 computer. A neutral density filter, optical density 1.0, was placed in the excitation line to prevent photodecomposition of surface-bound fluorophore. 

In contrast to the setup shown in Figure 5, our experiment uses two coaxial laser beams focused onto the sample C by a lens L (Figure 7). The dye laser beam (power 1 to 10 mW) creates the thermal lens in the sample, whereas the helium-neon laser is used only for monitoring development of the thermal lens. To avoid a thermal lens being induced by the helium-neon laser, a neutral density filter F2 reduces the power of its beam to 6 to 7 /xW in the sample. In front of the detector D, an interference filter F, blocks the beam of the dye laser, and a pinhole P is placed such that only light near the optical axis reaches the detector. To monitor the wavelength of excitation Ao, part of the dye laser beam is deflected by a glass plate Gj onto a... 

The t q)ieal optical setup of a fluorescence-lifetime spectrometer is shown in Fig. 5.5. The sample is exeited by a laser. The excitation intensity is adjusted by a variable neutral density filter. An additional bandpass filter may be required to bloek unwanted emission wavelengths of the laser. 

Other optics (neutral density filter, mirror and lens) Sigma Koki... 

Figure lb, c illustrates the optical configuration of objective-type TIRFM on an inverted microscope see Note 1). An objective lens with high numerical aperture (>1.4) is mounted on the inverted microscope (rrrNote 2). Alaser beam is passed through a neutral density filter and a beam expander to adjust its power and diameter. In order to convert the polarization of the beam from linear to circular, we used a quarter-wave plate. The incident laser beam is focused on the back focal plane (BFP) of the objective (rrrNote 3). To perform singlemolecule imaging, a laser beam is incident to the specimen at a power of 1 mW on a circular area 30 pm in diameter. 

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