CHAPTER 9. HARDWARE DESCRIPTIONS
PN-T321/T322B
HARDWARE DESCRIPTIONS
9 – 5
5. TOUCH PANEL (PN-T322B)
5 - 1. PRINCIPLE OF TOUCH PANEL
Reflected light from the retroreflective border is received by the camera
units mounted to the left and right upper section of the screen to obtain
the position of a shielded material by the triangulation.
1 ) A command is delivered from the CPU on the control PWB to con-
verge LED lights from the left and right camera units in the range of
a fan-shaped section of about 90° . The LED of camera unit 1 emits
light to the right side and the lower since of the screen, and the
LED of camera unit 2 to the left side and the lower side of the
screen.
2 ) When the LED light reaches the retroreflective border to the left
and eight sides and the lower side, it is reflected in the same direc-
tion as the angle of incidence. The line sensor in the camera unit
detects reflected light in the range of about 90° . At that time, if the
screen is touched with a finger, etc., reflection light at that section
does not come back, generating a shade.
DETECTION RANGE OF CAMERA UNIT 1
DETECTION RANGE OF CAMERA UNIT 2
3 ) The CPU calculates the touch position by triangulation according to
the results detected by camera units 1 and 2, and send the infor-
mation to the connected PC via the USB.
Camera unit
Line sensor
Glass substrate
LED
Reflected light
Touch by a finger
Retroreflective border
Detection range of
camera unit 1
LED light
Camera unit 1
Camera unit 2
Touch by a finger
Detection range of camera unit 2
Reflected light
Retroreflective
border
LED light
Camera unit 1
Camera unit 2
ἕ
Camera unit
1
2
(X,Y)
Retroreflective border
