5.3 Physical Anti-Collision Based on Wavelet
191
the horizontal camera and the center of the turntable is L, the horizontal
distance d i between the tag and the horizontal camera can be obtained
in Eq. (5.43).
d i = L − r i
(5.43)
Then, the theoretical distance l i which the horizontal camera needs so that
the horizontal camera can exactly focus on the i th RFID tag is calculated
in Eq. (5.44).
l i =
f l
l − f
(5.44)
where l
is the distance between the lens and CCD sensor inside horizontal
camera, f is the focal length of the horizontal camera.
Finally, the distance that the horizontal camera needs to move can be
calculated in Eq. (5.45).
L i = d i − l i
(5.45)
If L i is larger than zero, the horizontal camera approaches the tag.
Otherwise, the horizontal camera moves away from the tag.
(2) RFID tag 2D coordinate measurement.
After obtaining the 2D coordinates of the tags, we choose one tag as the
temple. Then, the control-computer controls the servomotor to drive the
turntable to rotate. The control computer adjusts the horizontal camera
to obtain the template’s image. The vertical distance from the center of
the template to the turntable is calculated as the vertical coordinate of
the template. After taking the vertical coordinate of the template as the
reference zero in vertical direction, the control computer controls the
servomotor to drive the turntable to rotate. The control computer adjusts
the horizontal camera to get every tag’s image. Each tag is matched with
the template by using the template matching method, and part of the tags
matching results are shown in Fig. 5.31.
After successful matching, the vertical distance of the template is used as
the reference zero to calculate the number of pixels between the center
of the tag and the center of the template. Because each pixel in the
CCD size is known and the horizontal distance from image plane to
horizontal camera is a fixed value, the size of each pixel in the image
can be calculated by using the triangular similarity principle. The vertical
coordinate of the i th RFID tag in the vertical direction is calculated by the
tag’s side view image and the difference number of pixels in the vertical
direction between the i th RFID tag and the template. The equation is:
191
the horizontal camera and the center of the turntable is L, the horizontal
distance d i between the tag and the horizontal camera can be obtained
in Eq. (5.43).
d i = L − r i
(5.43)
Then, the theoretical distance l i which the horizontal camera needs so that
the horizontal camera can exactly focus on the i th RFID tag is calculated
in Eq. (5.44).
l i =
f l
l − f
(5.44)
where l
is the distance between the lens and CCD sensor inside horizontal
camera, f is the focal length of the horizontal camera.
Finally, the distance that the horizontal camera needs to move can be
calculated in Eq. (5.45).
L i = d i − l i
(5.45)
If L i is larger than zero, the horizontal camera approaches the tag.
Otherwise, the horizontal camera moves away from the tag.
(2) RFID tag 2D coordinate measurement.
After obtaining the 2D coordinates of the tags, we choose one tag as the
temple. Then, the control-computer controls the servomotor to drive the
turntable to rotate. The control computer adjusts the horizontal camera
to obtain the template’s image. The vertical distance from the center of
the template to the turntable is calculated as the vertical coordinate of
the template. After taking the vertical coordinate of the template as the
reference zero in vertical direction, the control computer controls the
servomotor to drive the turntable to rotate. The control computer adjusts
the horizontal camera to get every tag’s image. Each tag is matched with
the template by using the template matching method, and part of the tags
matching results are shown in Fig. 5.31.
After successful matching, the vertical distance of the template is used as
the reference zero to calculate the number of pixels between the center
of the tag and the center of the template. Because each pixel in the
CCD size is known and the horizontal distance from image plane to
horizontal camera is a fixed value, the size of each pixel in the image
can be calculated by using the triangular similarity principle. The vertical
coordinate of the i th RFID tag in the vertical direction is calculated by the
tag’s side view image and the difference number of pixels in the vertical
direction between the i th RFID tag and the template. The equation is: