SYSTEMS AND METHODS FOR PICTURE EDGE ENHANCEMENT
Systems and methods for effectively and naturally enhancing the relative contrast between an image object and the surrounding background image in television pictures. In one embodiment, a television system preferably comprises a central processing unit (CPU) coupled to an audio-video output unit. The CPU preferably comprises non-volatile memory coupled to a logic unit which is adapted to receive and process a program signal S P and output an enhanced program signal S EP to the audio-video output unit. The logic unit preferably includes a differential waveform generator in one embodiment and a low pass filter in another embodiment. In operation in one embodiment, a waveform comprising a second differential of an original waveform and an inverted copy of the second differential of the original waveform is low pass filtered, and, depending on the shape of the original waveform, inverted prior to adding it to the original waveform to generate an enhanced waveform with improved relative contrast. In operation in an alternative embodiment, an aperture waveform is generated by adding a low pass filtered and inverted waveform of an original waveform to the original waveform, and then added to the original waveform to generate an enhanced waveform with improved relative contrast.
1 . A television system adapted to enhance the relative contrast between image objects and backgrounds images of a television picture through edge enhancement comprising
an audio-video output unit, and
a central processing unit (CPU) coupled to the audio-video output unit, the CPU comprising,
non-volatile memory, and
a logic unit coupled which is configured to receive and process a program signal by providing a gradual transition from low to high contrast in a contrast transition region along an edge of an object image enhancing the relative contrast between the object image and a surrounding background image of a picture in the program signal.
2 . The television system of claim 1 wherein the login unit comprises
an object edge detection circuit adapted to detect the edges of an object image within a picture in a program signal and identify a corresponding object edge waveform surrounding the edge of the object image,
a signal divider circuit coupled to the object edge detection circuit,
a differential waveform generator circuit coupled to the signal divider circuit, and
a signal adder circuit coupled to the differential waveform generator circuit and the signal divider circuit to add the waveform generated by the differential waveform generator circuit to the object edge waveform surrounding the edge of the object image and output an enhanced object edge waveform.
3 . The television system of claim 2 wherein the differential waveform generator circuit comprises
a first differential module adapted to generate a first differential waveform from the object edge waveform surrounding the edge of the object image, and
a second differential module coupled to the first differential module and adapted to generate a second differential waveform from the first differential waveform.
4 . The television system of claim 3 wherein the differential waveform generator circuit further comprises
a signal divider coupled to the second differential module,
an inverter coupled to the signal divider, and
a signal adder coupled to both the inverter and the signal divider to add the second differential waveform and the inverted second differential waveform.
5 . The television system of claim 4 wherein the differential waveform generator circuit further comprises a positive waveform slicer coupled to the signal adder and a low pass filter coupled to the waveform slicer.
6 . The television system of claim 1 wherein the login unit comprises
an object edge detection circuit adapted to detect the edges of an object image within a picture in a program signal and identify a corresponding object edge waveform surrounding the edge of the object image,
a signal divider circuit coupled to the object edge detection circuit,
a low pass filter coupled to the signal divider circuit,
an inverter coupled to the low pass filter,
a first signal adder circuit coupled to the inverter and the signal divider circuit, and
a second signal adder circuit coupled to the first signal adder circuit and the signal divider circuit.
7 . A method for enhancing the relative contrast between image objects and backgrounds images of a television picture through edge enhancement comprising the steps of
receiving a program signal
detecting a object edge waveform surrounding an edge of an object image in a television picture in the program signal, and
modifying the object edge waveform to include a gradual transition from low to high contrast in a contrast transition region surrounding the edge of the object image.
8 . The method of claim 7 wherein the step of modifying the object edge waveform comprises the steps of
generating a first differential waveform from the object edge waveform,
generating a second differential waveform from the first differential waveform,
combining the second differential waveform to an inverted copy of itself to form a combined second differential waveform and slicing the second differential waveform to capture a positive second differential waveform,
low pass filtering the positive second differential waveform to generate a low pass filtered waveform, and
combining the low pass filtered waveform with the object edge waveform to form an enhanced object edge waveform surrounding the edge of the object image.
8 . The method of claim 7 wherein the step of modifying the object edge waveform comprises the steps of
low pass filtering the object edge waveform is passed through a low pass filter to generate a low pass filtered waveform,
inverting low pass filtered waveform,
combining the inverted low pass filtered waveform with the object edge waveform to generate an aperture image waveform, and
combining the aperture image waveform with the object image waveform to form a an enhanced waveform corresponding to an improved image with aperture.