Method and apparatus for inspecting engine head valve retainer assemblies for missing keys

Apparatus for automatically inspecting a valve spring assembly of an engine head to determine whether both valve spring cap keys are present, said apparatus comprising camera means, conveyor means for moving said engine headpast said camera means, means for monitoring the position of said engine head relative to said camera means, computer means responsive to said monitoring means for controlling said camera means to obtain a digitized image of a portion of the valve spring assembly as represented by a two dimensional array of pixel light intensity values, said computer being programmed to

• (a) construct an edge pixel array of binary values from said array of pixel light intensity values,
• (b) identify the center of symmetry of the array of edge pixels,
• (c) count the number of pixels located at a predetermined radius from the center of symmetry of the edge pixel array which have a light intensity value which is greater than a predetermined threshold, and
• (d) indicate whether both keys of the assembly are present based on the value of the count.

A machine implemented method of processing a digitized image of a valve spring assembly of an engine head, the image being represented by a two dimensional array of pixel light intensity values;

• the method comprising the steps of:
• (a) constructing an edge pixel array of binary values from said array of pixel light intensity values,
• (b) identifying the center of symmetry of the array of edge pixels;
• and
• (c) determining the percent of those pixels located at a predetermined radius from the center of symmetry of the edge pixel array which have a light intensity value which is greater than a predetermined threshold to determine whether both keys of the valve spring assembly are present.

A machine implemented method of processing digitized image of a portion of an engine head, the image being represented by a two dimensional array of pixel light intensity values;

• the method comprising the steps of:
• (a) calculating the edge strength at each pixel of the array, comparing the horizontal and vertical components of the edge strength to determine whether the predominate direction is horizontal or vertical, and identifying edge pixels as those having an edge strength which is greater than or equal to the edge strength of a similarly directed pixel in adjacent rows if the pixel has a predominate horizontal direction and in adjacent columns if the pixel has a predominate vertical direction;
• (b) convolving the edge pixels on the left with those on the right for each of a plurality of vertical axes to determine the vertical axis of symmetry, convolving the edge pixels above with those below for each of a plurality of horizontal axes to determine the horizontal axis of symmetry, and determining the center of symmetry of the array of edge pixels from the intersection of the two axes of symmetry;
• (c) aligning the centers of symmetry of the edge pixel array with a model edge array and determining if there is a predetermined number of corresponding located edge pixels to verify that the center of symmetry of the edge pixel array is the center of a digitized image of a valve spring assembly;
• and
• (d) counting the number of pixels located at a predetermined radius from the center of symmetry of the edge pixel array which have a light intensity value which is greater than a predetermined threshold to determine whether both keys of the valve assembly are present.

A machine implemented method of processing a digitized image of a portion of an engine head to determine whether both keys of a valve spring assembly of the engine head are present, the image being represented by a two dimensional array of pixel light intensity values;

• the method comprising the steps of:
• (a) calculating the horizontal and vertical components of the edge strength at each pixel of the array, summing the absolute values of the components to obtain an edge strength, comparing the horizontal and vertical components of the pixel edge strength to determine whether the predominate direction is horizontal or vertical, and identifying edge pixels as those having an edge strength which is greater than or equal to the edge strength of a similarly directed pixel in adjacent rows if the pixel has a predominate horizontal direction and in adjacent columns if the pixel has a predominate vertical direction;
• (b) convolving the edge pixels on the left with those on the right for each of a plurality of vertical axes to determine the vertical axis of symmetry, convolving the edge pixels above with those below for each of a plurality of horizontal axes to determine the horizontal axis of symmetry, and determining the center of symmetry of the array of edge pixels from intersection of the two axes of symmetry;
• (c) aligning the centers of symmetry of the edge pixel array with a model edge array and determining if there is a predetermined number of correspondingly located edge pixels to verify that the center of symmetry of the edge pixel array is the center of a digitized image of a valve spring assembly;
• and
• (d) counting the number of pixels located at a predetermined radius from the center of symmetry of the edge pixel array which have a light intensity value which is greater than a predetermined threshold and indicating that the assembly has both keys if the count is greater than a predetermined count.