Band Filtering

Band filtering does just that. The program listed below takes a stream of x-y coordinates, one data pair per line, and returns just the points needed to plot the curve. You control the smoothness of the curve by setting the -filter (or -f) option. By default, the filter is 0.001, but you can set it smaller to get a smoother curve with more data points, or larger to get a rougher curve. By default, the program takes input from the standard input stream, but you can specify an input file with the -input (or -i) option. The results are sent to the standard output stream, which you can redirect as usual. 

---

Colorimeters. Also known as tristimulus colorimeters, these are instniments that do not measure spectral data but typically use four broad-band filters to approximate the jy, and the two peaks of the x color-matching functions of the standard observer curves of Figure 7. They may have lower accuracy and be less expensive, but they can serve adequately for most industrial color control functions. Examples of colorimeters are the BYK-Gardner Co. XL-835 the Hunter Lab D25 series the Minolta CA, CL, CS, CT, and CR series (the last of these is portable with an interface) and the portable X-Rite 918. 

If it is necessary for engineering purposes to know the tonal make-up of a noise, several approaches are possible. A bandpass filter can process the noise. The most common filters are octave band filters, and the agreed center frequencies are as follows ... 

Figure 2. Transmittance spectral profile of a coating consisting of a quarterwave stack of 23 layer stack centered on 800 nm. Light gray without ripple control. Dark gray with ripple control. It can be used either as a intermediate band filter, or a shortwave dichroic beam splitter or a longwave one.

Band filters have several advantages over rotary vacuum filters which are described in the following section. These include ... 

Fig. 4. Bottom the Double-Band-Filtered COSY spectrum obtained by selection through DANTE-Z of the H region (prior to the evolution interval) and by the selection through SPlN-PlNGING [11] of the amide region (before the acquisition interval) of toxin 7. Top the corresponding region of a standard COSY spectrum. Note, in the bottom diagram, the considerable increase in spectral resolution as well as the occurrence of additional crosspeaks (indicated with asterisks). Experiments were performed at 360 MHz (Bruker AMX360) in H2O at 318 K. The 50 W class C amplifier of the proton channel was used as transmitter.

In electrical engineering terms, we can say that the operation of the brain and nervous system and the ordinary consciousness that results constitutes a high-gain, narrow-band filter dealing with the immediate physical present. This is obviously of high biological significance for our survival. The second dimension of time, which awareness can sometimes work with, is a filter with a much wider band, but its output is ordinarily quite low. 

Fig. 5.38 Microwave ceramic components (a) metallized ceramic engine block for 40 MHz pass band filter at 1.4 GHz (b) 11.75 GHz oscillator incorporating ceramic dielectric resonator together with various resonator pucks.

Fig. 5.39 (a) Schematic of a 2/4 strip line resonator pass-band filter exploiting LTCC technology the approximate overall dimensions are 15x10x1 mm. (b) Equivalent circuit Q is the pad-to-strip-line capacitance and L and C the inductance and capacitance of the stripline. 

By reference to the equivalent circuit explain why the device is a pass-band filter and suggest a design modification which would more closely define the band, and why. [Answer 5 GHz]... 

If sensitivity, spectral resolution, and minimal photobleaching are primary concerns, single narrow band filters sets with black and white CCD camera detection is the best option. Image registration shifts are minimized in today s filters by the use of polished substrates and virtually eliminated by using filter sets made to zero shift specifications. 

The type and number of fluorescent probes also plays a role in the optimizing of the filters. For a small number of probes with adequate spectral separation it is possible to use traditional wide bandpass filter sets. In protocols where 5 or 6 probes are being used, it is necessary to use dye-specific narrow band filter sets to reduce spectral bleedthrough. 

Improvements in the single side-band performance of a mixer-based receiver can be made by filtering the unwanted side band before it is down-converted in the mixer. Such a scheme, which is described in detail by Goldsmith (1982) is based on interferrometric techniques. We will not discuss single side-band filtering any further, except to note that it is a particularly apposite demonstration of the use of optical techniques to process the radiation in the spectrometer. We will discuss the use of interferometric techniques in Section IX as a means to realize a reflection mode spectrometer. These few examples indicate the flexibility of application of optical techniques to problems of instrument design in the FIR. 

---