Wedge, interference

For exceedingly weak chemiluminescent reactions it is possible to improve the light collection geometry at the expense of spectral resolution and to use a wedge interference filter spectrometer as shown in Fig. 4 (Hamman, Biggley and Seliger, 1979). 

In Fig. 4 an opaque plastic sample holder (H) whose 0.5-mm thick base contains a 3 mm wide x 10 mm long slit (S), positions the bottom of a 13 mm I.D. x 45 mm glass vial at 1.5 mm above the top surface of a Verlauf B-60 wedge interference filter (F) (60 mm long x 25 mm wide x 3 mm thick Schott Optical Glass Co., Inc.). The filter is mounted in a 3-mm thick filter holder which slides horizontally 1 mm above the photocathode of an EMI 9789 QB phototube (effective diameter of photocathode 10 mm). The total distance from the bottom of the solution in the glass vial to the photocathode is 6 mm. A synchronous motor rotates a screw drive which in turn drives the... 

Fig. 4. Schematic drawing of the details of the construction of the wedge interference filter spectrometer. J, injection port C, light-tight cover V, sample vial sample vial holder S, slit FH, filter housing F, wedge interference filter PT phototube PC, photocathode L, linkage to screw drive RF, RF shielded phototube housing.

At any wavelength setting of the wedge interference filter spectrometer the current measured due to a known chemiluminescent reaction in exactly the same geometry as any unknown reaction will be... 

A wedge-interference filter (WIF) consists of two quartz plates spaced by a dielectric wedge. Moving the wedge in front of a slit produces incremental wavelength bands. Paul Wilks has been its strongest supporter. Spectrometers that incorporate a WIF are full-spectrum instruments. 

Wedge-Interference Filters. Figure 4.1.7 is a schematic of a wedge-interference filter (WIF) spectrometer. Wedge filters are constructed similarly to fixed filters, with... 

Figure 4.1.7. Schematic of a wedge-interference filter spectrometer. The optical dielectric is held statically hy the two quartz plates.

Figure 4.1.8. The Wilks wedge-interference filter spectrometer (A) picture and (B) schematic. (Reproduced with permission from Wilks Enterprises, 140 Water Street, Norwalk, CT 06854).

Wilks Enterprise, Inc. 140 Water Street So. Norwalk, CT 06854 USA TEL 203-895-9136 FAX 203-838-9868 URL http //www.wilksir.com/ DA, wedge interference filters... 

Stryker Biosteon Wedge interference screw Bioabsorbable 25 % Hydroxyapatite (HA), 75 % amorphous PLEA... 

Figure 4.20.A shows a more recent cell reported by Cobben et al. It consists of three Perspex blocks, of which two (A) are identical and the third (B) different. Part A is a Perspex block (1) furnished with two pairs of resilient hooks (3) for electrical contact. With the aid of a spring, the hooks press at the surface of the sensor contact pads (4), the back side of which rests on the Perspex siuface, so the sensor gate is positioned in the centre of the block, which is marked by an engraved cross as in the above-described wall-jet cell. Part B is a prismatic Perspex block (2) (85 x 24 x 10 mm ) into which a Z-shaped flow channel of 0.5 mm diameter is drilled. Each of the wedges of the Z reaches the outside of the block. The Z-shaped flow-cell thus built has a zero dead volume. As a result, the solution volume held between the two CHEMFETs is very small (3 pL). The cell is sealed by gently pushing block A to B with a lever. The inherent plasticity of the PVC membrane ensures water-tight closure of the cell. The closeness between the two electrodes enables differential measurements with no interference from the liquid junction potential. The differential signal provided by a potassium-selective and a sodium-selective CHEMFET exhibits a Nemstian behaviour and is selective towards potassium in the presence of a (fixed) excess concentration of sodium. The combined use of a highly lead-selective CHEMFET and a potassium-selective CHEMFET in this type of cell also provides excellent results.

It is sometimes desirable to eliminate interference bands from transmission spectra this is particularly true in the measurement of absorption spectra (a as a function of wavelength), where interference bands can be a nuisance. If 8h X/An, a condition that can be achieved by using a wedge-shaped sample, for example, then the observed transmittance is given by (2.76). 

Figure 1. Schematic illustration of sample geometries and THG interference fringing patterns, a). Wedge sample geometry, x is the cell displacement direction, b). Wedge THG interference fringes as a function of x. c). Slab sample geometry, 8 is the angle of incidence, d). THG interference fringes as a function of 8 (Maker Fringes).

---