US 12,591,956 B2 · Noise reduction and feature enhancement for a thermal imaging camera

Abstract

Thermal cameras, particularly less elaborate inexpensive designs, may deliver high temperature resolution at the expense of less clear displayed images. For many low visibility uses, such as firefighting, it may be advantageous to sacrifice some temperature detail for clarity and object recognition. Without sacrificing the actual detailed temperature information available in a captured scene, it may be beneficial to apply filters in series to raw image data that reduce visible noise and build back in feature contrast for the purposes of providing a user a displayed image that permits ease of object recognition, while still providing the raw data to a thermography module to maintain high resolution of temperature information if desired. In addition, more efficient and useful edge highlighting techniques are disclosed. For very low contrast scenes, such as smoky rooms and the like, other specific filters and equalization methods may be applied.

Claims16

Dependent claims

A method for reducing noise in a thermal image in a thermal camera including a thermal imaging sensor, and image processing capability for implementing a signal processing chain of processor executed functions, the method comprising:

receiving partially processed image frame data at a noise reduction filter in the signal processing chain, the partially processed image frame data comprising frames of pixel values;
and, for each pixel of a plurality of pixels of the frame:
calculating n delta values for the pixel, each of the delta values comprising a difference between the pixel value of the pixel and the pixel value of a near or nearest neighbor pixel;
deriving, based on a weight look up table (LUT), n weight values each corresponding to one of the n delta values;
summing the n weight values;
deriving n weighted delta values each equal to a product of the corresponding weight and delta values;
summing the n weighted delta values;
and
passing forward to the signal processing chain a filtered pixel value equal to the received pixel value for the pixel minus a quotient of the sum of the n weighted delta values divided by the sum of the n weight values.

6 more elements

A method for enhancing features in a thermal image in a thermal camera including a thermal imaging sensor, and image processing capability for implementing a signal processing chain of processor executed functions, the method comprising:

receiving a frame of partially processed image frame data comprising pixel values at a feature enhancement filter in the signal processing chain;
and, for each pixel of a plurality of pixels of the frame:
applying a low pass filter (LPF) to the pixel to generate a LPF pixel value;
subtracting the LPF pixel value from the received pixel value of the pixel;
applying a high pass filter (HPF) to the LPF pixel value to generate a HPF pixel value;
applying a variable gain to the HPF pixel value according to a gain LUT;
adding the LPF pixel value to the pixel value derived from the gain LUT to derive a feature enhanced pixel value;
and
passing forward the feature enhanced pixel value to the signal processing chain.

6 more elements

Dependencies are inferred from the claim text.

Noise reduction and feature enhancement for a thermal imaging camera

Life of this patent

Noise reduction and feature enhancement for a thermal imaging camera

Life of this patent

Abstract

Claims16