Detection of a sheet of light based on second derivative

A field-programmable gate array (FPGA) to detect a position of a sheet of light in an image, the FPGA comprising:

• a set of one or more processing units;
• and
• a non-transitory machine-readable storage medium containing code, which when executed by the set of one or more processing units, causes the FPGA to:
• apply a second derivative filter to an intensity profile of a line of pixels included in an image of the sheet of light as projected onto an object to obtain a plurality of second derivative values associated with corresponding pixel positions,
• determine an ingress pixel position associated with an ingress zero-crossing second derivative value, wherein the ingress pixel position is between a first pixel position with a first minimum intensity value of the intensity profile and a second pixel position with a first maximum intensity value of the intensity profile,
• determine an egress pixel position associated with an egress zero-crossing second derivative value, wherein the egress pixel position is between a third pixel position with a second maximum intensity value of the intensity profile and a fourth pixel position with a second minimum intensity value of the intensity profile,
• determine a midpoint pixel position between the ingress pixel position and the egress pixel position, and
• output the midpoint pixel position as the position of the sheet of light.

A non-transitory computer readable storage medium that provide instructions, which when executed by a processor of a proxy server, cause said processor to perform operations comprising:

• applying a second derivative filter to an intensity profile of a line of pixels included in an image of a sheet of light as projected onto an object to obtain a plurality of second derivative values associated with corresponding pixel positions;
• determining an ingress pixel position associated with an ingress zero-crossing second derivative value, wherein the ingress pixel position is between a first pixel position with a first minimum intensity value of the intensity profile and a second pixel position with a first maximum intensity value of the intensity profile;
• determining an egress pixel position associated with an egress zero-crossing second derivative value, wherein the egress pixel position is between a third pixel position with a second maximum intensity value of the intensity profile and a fourth pixel position with a second minimum intensity value of the intensity profile;
• determining a midpoint pixel position between the ingress pixel position and the egress pixel position;
• and
• outputting the midpoint pixel position as a position of the sheet of light.