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01:26Scaling
In designing and analyzing filters, resonant circuits, or circuit analysis at large, working with standard element values like 1 ohm, 1 henry, or 1 farad can be convenient before scaling these values to more realistic figures. This approach is widely utilized by not employing realistic element values in numerous examples and problems; it simplifies mastering circuit analysis through convenient component values. The complexity of calculations is thereby reduced, with the understanding that...
01:20Design Example: Capacitance Multiplier Circuit
In integrated circuit technology, a capacitance multiplier is often utilized to produce a larger capacitance value when a small physical capacitance falls short. This is achieved by a circuit that multiplies capacitance values by a factor of up to 1000, such that a 10-pF capacitor can replicate the performance of a 100-nF capacitor.
The circuit illustrated in Figure 1 below incorporates two op-amps, with the first operating as a voltage follower and the second acting as an inverting amplifier.
The circuit illustrated in Figure 1 below incorporates two op-amps, with the first operating as a voltage follower and the second acting as an inverting amplifier.
01:22Upsampling
Managing signal sampling rates is essential in digital signal processing to maintain signal integrity. A decimated signal, characterized by a reduced frequency range due to its lower sampling rate, can be upsampled by inserting zeros between each sample. This upsampling process expands the original spectrum and introduces repeated spectral replicas at intervals dictated by the new Nyquist frequency. To refine this zero-inserted sequence, it is passed through a lowpass filter with a cutoff...
01:15Optimizing Chromatographic Separations
Optimizing chromatographic separations is crucial for obtaining clean separations in a minimum amount of time. Optimization is required for several factors, including kinetic effects related to band broadening, plate height, capacity factor, and separation factor.
Band broadening refers to spreading solute bands as they travel through the column. This broadening can impact resolution. Plate height (H) represents the length required for one theoretical plate. A lower plate height corresponds to...
Band broadening refers to spreading solute bands as they travel through the column. This broadening can impact resolution. Plate height (H) represents the length required for one theoretical plate. A lower plate height corresponds to...
01:25Active Filters
Active filters are electronic circuits that use operational amplifiers (op-amps), resistors, and capacitors to filter out unwanted frequency components from a signal. A first-order low-pass active filter is designed to pass signals with a frequency lower than a certain cutoff frequency and attenuate frequencies higher than that cutoff frequency. The transfer function for a first-order low-pass active filter is:
01:37Super-resolution Fluorescence Microscopy
Super-resolution fluorescence microscopy (SRFM) provides a better resolution than conventional fluorescence microscopy by reducing the point spread function (PSF). PSF is the light intensity distribution from a point that causes it to appear blurred. Due to PSF, each fluorescing point appears bigger than its actual size, and it is the PSF interference of nearby fluorophores that causes the blurred image. Various approaches to achieving higher resolution through SRFM have recently been developed.
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Updated: Jun 16, 2026
10:16
Digital Inline Holographic Microscopy (DIHM) of Weakly-scattering Subjects
Published on: February 8, 2014
Increasing the holographic matched filter information capacity.
Applied Optics
|February 23, 2010
Summary
This study demonstrates how sampled Fourier holograms increase character capacity in matched spatial filters for Vander Lugt correlator systems. Sampling acts as a multiplexing technique, enabling denser hologram recording without information loss.
Area of Science:
- Optics and Photonics
- Information Optics
- Holography
Background:
- Vander Lugt correlators are optical systems used for pattern recognition.
- Matched spatial filters (MSFs) are crucial components in correlator systems.
- Traditional holograms can have limitations in data storage density.
Purpose of the Study:
- To investigate the advantage of using sampled Fourier holograms in Vander Lugt correlator systems.
- To enhance the number of characters that can be stored in a matched spatial filter.
- To explore sampling as a multiplexing technique for Fourier holograms.
Main Methods:
- Recording sampled Fourier holograms by inserting a sampling mask during hologram recording.
- Applying the Whittaker-Shannon theorem to ensure no information loss when the sampling period matches the object spectrum.
- Utilizing the reduced area coverage of sampled holograms to record multiple Fourier holograms on a single plate.
- Adjusting the offset angle of the reference beam to prevent image overlap.
Main Results:
- Sampled Fourier holograms significantly enhance the number of characters storable in MSFs.
- Sampling acts as an effective multiplexing technique for Fourier holograms.
- Multiple closely packed Fourier holograms can be recorded on the same photographic plate area.
- Cross-correlation and autocorrelation images are successfully generated at the correlator output.
Conclusions:
- Sampled Fourier holograms offer a practical method for increasing data capacity in optical correlator systems.
- The proposed technique allows for denser storage of information in matched spatial filters.
- This approach provides a viable solution for multiplexing holographic data for enhanced pattern recognition capabilities.