6 Difference Between High Pass And Low Pass Filters In Image Processing

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A filter is a circuit that removes or filter-out a specified range of frequency components. In other words, it separates the signal’s spectrum into frequency components that will be passed and frequency components that will be blocked.

Filters can be classified in accordance with the general characteristics of the filter’s frequency response. If a filter passes low frequencies and blocks high frequencies, it is referred to as a low-pass filter. If it blocks frequencies and passes high frequencies, it is a high-pass filter.

Also filters can be classified based on the type of components that are used to implement the circuit. In this regard, they are classified as either Active or passive filters. An active filter can filter a signal and apply gain, because it includes an active component such as a transistor or an operational amplifier, whereas Passive filters use resistors, capacitors and inductors; these components have no ability to provide amplification and consequently a passive filter can only maintain or reduce the amplitude of an input signal.

What Is High Pass Filter?

A high pass filter (HPF) is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with frequencies lower than the cutoff frequency.  The amount of attenuation for each frequency depends on the filter design.

The basic high pass filter is built by a series connection of capacitor and resistor. While the input signal is applied to the capacitor, the output is drawn across the resistor.

A high-pass filter is usually modeled as a linear time-invariant system. It is sometimes referred to as low-cut filter or bass-cut filter. High-pass filters have many uses, such as blocking DC from circuitry sensitive to non-zero average voltages or radio frequency devices. They can also be used in conjunction with a low-pass filter to produce a band-pass filter.

What You Need To Know About High Pass Filters

  1. A high pass filter allows frequencies higher than its corner frequency to pass through it cleanly (ideally) while blocking high frequencies.
  2. High pass filter consists of capacitor followed by a resistor in parallel.
  3. High pass filter is used in audio amplifier for coupling or removing distortions due to low-frequency signal such as noise.
  4. Operating frequency of high pass filter is higher than the cut off frequency.
  5. It is used for sharpening the image.
  6. It attenuates the low frequency

What Is Low Pass Filter?

A low-pass filter (LPF) is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filter design. The exact frequency response of the filter depends on the filter design. The filter is sometimes referred to as a high-cut filter or treble-cut filter in audio applications.

Low pass filters can be constructed using resistors with either capacitors or inductors. A low pass filter composed of a resistor and a capacitor is referred to as a Low-pass RC filter whereas a low pass filter with a resistor and an inductor is referred to as a Low-pass RL filter.

There are many forms of low pass filters including electronic circuits such as a hiss filter used in audio, anti-aliasing filters for conditioning signals prior to analog-to-digital conversion, digital filters for smoothing sets of data, acoustic barriers, blurring of images etc.  

Low-pass filters provide a smoother form of a signal, removing the short-term fluctuations and leaving the longer-term trend. Major examples of low-pass filters occur in acoustics, optics and electronics.

What You Need To Know About Low Pass Filters

  1. A low pass filter allows frequencies lower than its corner frequency to pass through it cleanly (ideally) while blocking high frequencies.
  2. Low pass filter circuit consists of resistor followed by the capacitor.
  3. Low pass filter is used in removing aliasing effect in communication circuits.
  4. Operating frequency of low pass filter is lower than the cut off frequency.
  5. It is used for smoothing the image.
  6. It attenuates the high frequency.

Also Read: Difference Between Opening And Closing In Digital Image Processing

Difference Between High Pass And Low Pass Filters In Tabular Form

BASIS OF COMPARISON HIGH-PASS FILTERS LOW-PASS FILTERS
Description A high pass filter allows frequencies higher than its corner frequency to pass through it cleanly (ideally) while blocking high frequencies.   A low pass filter allows frequencies lower than its corner frequency to pass through it cleanly (ideally) while blocking high frequencies.  
Components High pass filter consists of capacitor followed by a resistor in parallel.   Low pass filter circuit consists of resistor followed by the capacitor.  
Application High pass filter is used in audio amplifier for coupling or removing distortions due to low-frequency signal such as noise.   Low pass filter is used in removing aliasing effect in communication circuits.  
Operating Frequency Operating frequency of high pass filter is higher than the cut off frequency.   Operating frequency of low pass filter is lower than the cut off frequency.  
Use It is used for sharpening the image.   It is used for smoothing the image.  
Attenuation Frequency It attenuates the low frequency   It attenuates the high frequency.  

Similarities Between High-Pass And Low-Pass Filters

  • They consist of a stop band, a corner frequency and a pass band
  • They can both be constructed using two circuit elements.
  • They can both be constructed in two ways. A capacitor in shunt mode will provide a low pass filter whereas in series mode it will provide a high pass filter.

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