Related Experiment Video
Updated: Jun 13, 2026
13:44
Detection of Architectural Distortion in Prior Mammograms via Analysis of Oriented Patterns
Published on: August 30, 2013
Rotation-invariant digital pattern recognition using circular harmonic expansion.
Y N Hsu1, H H Arsenault, G April
1Universite Laval, Departement de Physique, Laboratoire de recherches en optique et laser, Quebec, P.Q. GK 7P4.
Applied Optics
|April 20, 2010
Summary
A novel rotation-invariant pattern recognition method uses circular harmonic expansion for precise target orientation detection. This technique achieves high accuracy, making it suitable for optical applications.
Area of Science:
- Computer Vision
- Optical Engineering
- Signal Processing
Background:
- Pattern recognition often struggles with variations in object orientation.
- Traditional methods may require complex computations or be sensitive to rotation.
Purpose of the Study:
- To develop a robust method for rotation-invariant pattern recognition.
- To achieve high-accuracy detection of target orientations.
Main Methods:
- Utilizing a component of the circular harmonic expansion for reference preparation.
- Performing correlation via Fast Fourier Transform (FFT) and frequency domain multiplication.
Main Results:
- Demonstrated accurate detection of target orientations within approximately 0.1 degrees.
- Successfully recognized targets within a 192 x 192 pixel image.
Conclusions:
- The proposed method offers effective rotation-invariant pattern recognition.
- The technique is well-suited for practical optical implementation.
Related Concept Videos
01:03IR Frequency Region: Fingerprint Region
IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the C=O, C=N, and C=C occur between 1600–1850 cm−1.
The...
The...
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
01:42Simple Harmonic Motion and Uniform Circular Motion
While simple harmonic motion and uniform circular motion may be two separate concepts, they correlate and interlink with each other. Simple harmonic motion is an oscillatory motion in a system where the net force can be described by Hooke's law, while uniform circular motion is the motion of an object in a circular path at constant speed.
There is an easy way to produce simple harmonic motion by using uniform circular motion. For instance, consider a ball attached to a uniformly rotating...
There is an easy way to produce simple harmonic motion by using uniform circular motion. For instance, consider a ball attached to a uniformly rotating...
01:23Curvilinear Motion: Rectangular Components
Curvilinear motion characterizes the movement of a particle or object along a curved path, notably evident when envisioning a car navigating a winding road. If the car starts at point A, its position vector is established within a fixed frame of reference, where the ratio of the position vector to its magnitude signifies the unit vector pointing in the position vector's direction.
As the car advances, its position evolves over time. Quantifying the car's velocity involves computing the time...
As the car advances, its position evolves over time. Quantifying the car's velocity involves computing the time...
01:24IR Frequency Region: X–H Stretching
In IR spectroscopy, signals produced by the X−H bonds (such as C−H, O−H, or N−H) can be observed in the frequency range of 2700–4000 cm–1. The C−H stretching vibration forms sharp bands in the region 2850–3000 cm–1. The presence of the O−H stretching vibration leads to the forming of an absorption band in the frequency range 3650–3200 cm−1. At the same time, N−H stretching can be confirmed by absorption bands in the 3500–3100 cm−1 range. Even though both O−H and N−H bonds vibrate at a similar...
01:22Non-uniform Circular Motion
In uniform circular motion, the particle executing circular motion has a constant speed, and the circle is at a fixed radius. However, not all circular motion occurs at a constant speed. A particle can travel in a circle and speed up or slow down, showing an acceleration in the direction of motion. In that case, the motion is called non-uniform circular motion, and an additional acceleration is introduced, which is in the direction tangential to the circle.
For example, such accelerations...
For example, such accelerations...