Range And Accuracy - Parallax 28044 Manual

This command can be used from within the LRF Image Viewer tool to easily view the image. YUVTools
(www.sunrayimage.com) can also be used to convert the raw binary data into a YUV422-decoded color
image.
Example:
:C
<binary data>END
:
P: Capture & send image processed frame (16 bits/pixel YUV422 color @ 640x16)
Capture a 640x16 resolution "processed" image with the LRF Module's camera and return the data in a
binary format. This mode is specific for range finding functionality and consists of a background
subtracted image where one frame is taken with the laser diode off, one frame taken with laser diode on,
and the data subtracted to help isolate the laser spot from the rest of the image frame. See Image
Processing and Blob Detection, page 18, for more details.
The data is sent MSB first, two bytes per pixel, starting at the upper-left pixel location (0,0), moving left
to right, top to bottom across the frame, and ending at the lower-right pixel location (640,16). Every two
bytes corresponds to a single pixel. The pixel format is YUY2 (www.fourcc.org/yuv.php), a subset of
YUV422 formatting in which each 16-bit pixel is given an 8-bit Y component (luma/brightness) and
alternating 8-bit U or 8-bit V component (chroma). See Camera Interface, page 17, for more details.
A total of 20,480 bytes of binary data is sent. An ASCII footer ("END") is then attached to the end of the
binary data stream to assist in identifying the end of frame.
This command can be used from within the LRF Image Viewer tool to easily view the image. YUVTools
(www.sunrayimage.com) can also be used to convert the raw binary data into a YUV422-decoded color
image.
Example:
:P
<binary data>END
:

Range and Accuracy

The LRF Module is most accurate within its optimal measurement range of 6–48 inches (15–122 cm).
Within this range, error can span from zero (no difference between actual distance and the distance
calculated by the LRF) to 5%. On average, the error is approximately 3%.
Within the optimal measurement range, the horizontal position of the laser spot within the camera's
frame (which is used to determine distance to the target object) changes noticeably. At longer distances,
although the camera can still "see" the laser spot, the horizontal position does not change as much,
causing a significant reduction in accuracy. Accuracy also varies with lighting conditions and material of
the target object, which affect the LRF Module's capability to determine the laser spot within the camera's
frame.
The LRF Module intentionally limits the maximum detectable distance to ~8 feet (100 inches). At
distances less than 6 inches, the laser spot is out of the camera's field-of-view, so no range calculation
can occur. See Theory of Operation, page 14, for range finding and image processing details.
Copyright © Parallax Inc. Parallax Laser Range Finder (#28044) v1.0 9/16/2011 Page 8 of 24