Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 BACKGROUND Of THE INVENTION
2 1. Field of the Invention
3 The invention generally relates to a
4 light pen and, in particular, a fiber optic light pen
employed in combination with an illuminated surface
6 such as a cathode ray tube, to sense information
7 displayed on the tube.
8 2. Description of the Prior Art
9 Optical light pens are well known in
the prior art. Basically, there are two types of
11 light pens. The first type is disclosed in U.S.
12 Patent No. 4,182,956 and is used in reading coded
13 information appearing on the label of an item. Such
14 light pens typically have a light source which
generates light intended to strike the region of the
code. The second type of light pen is intended for
17 responding to visual information displayed on an
18 illuminated surface such as a cathode ray tube.
19 ~lthough the present invention is described with
particular regard to this second type of light pen, it
21 should be understood that the inventive features of
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1 the light pen disclosed herein may also be employed in
2 the first type of light pen.
3 Light pens of the prior art for use with a
4 color cathode ray tube (CRT) generally had
problematical electrical noise. In particular, the
6 light detectors of prior art pens were located within
7 the light pen itself and would react to spurious
8 electrical pulses caused by the close proximity of the
9 detector to the CRT faceplate. These spurious pulses
lû caused false detections to take place, especially when
11 the light pen was used to sense areas of low
12 brightness or luminance where the normal detector
13 output is low.
14 ûne way to avoid this noise problem W3S to
provide a better electrical shielding for the light
16 pen's detector and amplifier circuitry. However,
17 increasing the shielding does not eliminate all the
18 noise, although the noise level will decrease.
19 SUMMARY OF THE INVENTION
It is an object of this invention to
21 provide a new and improved optical light pen emoloying
22 fiber optics.
23 It is a further object of this invention to
24 provide a fiber optic light pen assembly which is not
susceptible to electrically induced noise when placed
26 close to a CRT.
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1 The fiber optic light pen according to the
2 invention is for use in combination with a cathode ray
3 tube and a remote light detector to sense information
4 displayed on the tube. The pen includes a housing
having a front portion and a rear portion with an
6 opening therethrough. An actuating means is slidably
7 located within the opening of the housing and projects
8 from the front portion of the housing. The actuating
9 means has a light guiding aperture associated with at
least one fiber optic element which conducts the light
11 to the remotely located light detector where it is
12 detected. A switch in the light pen controls the
13 light detector circuitry and is responsive to the
14 position of the actuating means within the opening of
the housing. In use, the front portion of the pen is
16 pressed against the cathode ray tube causing the
17 actuating means to slide rearwardly, triggering the
18 switch and activating the light detector. The light
19 detector detects light transmitted through the
combination of the light guiding aperture of the
21 actuating means and the fiber optic element associated
22 therewith.
23 For a better understanding of the present
24 invention, together with other and further objects,
reference is made to the following description7 taken
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1 in conjunction with the accompanying drawings, and its
2 scope will be pointed out in the appended claims.
3 8RIEF DESCRIPTION ûF THE DRAWING
4 r igure 1 is a partial, longitudinal,
cross-sectional view of a fiber optic light pen
6 according to the invention;
7 figure 2 is a side view of the actuator
8 employed in the light pen illustrated in Figure l;
9 Figure 3 is a front end view of the bracket
4 taken along lines 3-3 of Figure l; and
ll Figure 4 is a partial, longitudinal,
12 cross-sectional view of an alternative embodiment of
13 the fiber optic light pen according to the invention.
14 DETAILED DESCRIPTION OF THE INVENTION
As shown in Figure 1, the optical light pen
16 according to the invention has an outer housing member
17 3 comprising a cylindrical tube which may be
18 conveniently gripped by the user of the light pen.
19 Although the housing member 3 is illustrated as
cylindrical, it is contemplated that the outer body of
21 the light pen may be any convenient shape for handling
~2 by a user. It is only necessary that the outer body
23 be provided with an opening, such as axial opening 3a,
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1 for supporting the inner parts of the li~ht pen
2 according to the invention. The forward end 20 of the
3 light pen is provided with an opening 3b, through
4 which nose piece 1 projects, ~Nith inwardly tapering
shoulders 3c for supporting the nose piece 1.
6 Generally, the nose piece 1 has a tapered portion la
7 integrally terminating in an engaging portion lb which
8 is axially and slidably mounted within the forward end
9 20 of axial opening 3a of the housing member 3. It is
contemplated that the tapered end la of the nose piece
11 may contact the surface of the CRT with which the
12 light pen is employed.
13 The engaging portion lb of nose piece 1
14 abuts against an actuator 2 and is slidably arranged
within the axial opening 3a of the housing member 3
16 and slidably arranged therein. The nose piece 1 and
17 actuator 2 form the actuating means of the invention.
18 The actuator 2 may best be appreciated by referring to
19 Figure 2. The actuator 2 is provided with a forward
surface 2a, for contacting the engaging portion lb of
21~ the nose piece 1, and two rearward projecting prongs
22 15 and 16. Actuating prong 15 is provided with a bend
23 15a so that the tip 15b of the prong 15 is located
24 near the body member axis 21, indicated by a dotted
line in figure 2. Parallel to the axis 21, guiding
26 prong 16 also projects rearwardly from the support
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1 member 17. Prongs 15 and 16 engage switch bracket 4,
2 also located within the axial opening 3a of the
3 housing member 3. The rearward end 30 of the housing
4 member 3 is provided with internal threads 6 for
engaging the external threads 7 on the switch bracket
6 4.
7 Figure 3 is a front end view of the switch
8 bracket 4 showing surface 4a. As can be appreciated
9 by referring to Figure 1, the switch bracket 4 is
generally U-shaped, having an engaging portion 4b, a
11 threaded portion 4c and an interconnecting portion
12 4d. The engaging portion 4b is provided with two
13 openings 22 and 23 for receiving the prongs 15 and 16,
14 respectively. Portion 4b is also provided with
opening 24 through which fiber optic bundle 9,
16 comprising at least one fiber optic element, passes.
17 Disposed on the interconnecting portion 4d
18 is switch 11, which is attached to portion 4d by
19 switch screw 13. The switch 11 is provided with a set
of terminals lOa connected to switch wiring lOb which
21 for~s a part oF the wire harness 8. The opposing end,
22 or front end, of switch 11 is provided with a pressure
23 sensitive trip 12 in contact with rearward end 15b of
24 prong 15. Separating the switch bracket 4 from the
actuator 2 is a coil spring 14 located axially
26 therebetween and within the axial opening ~a.
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1 Portion 4c of the switch bracket 4 is externally
2 threaded to engage the internal threads 6 of housing
3 member 3, thereby holding the switch bracket 4 rigidly
4 in place with respect to the housing member 3. The
threaded portion 4c of the switch bracket 4 is also
6 provided with an axial opening 25 through which the
7 wire harness 8 passes. A set screw 26, perpendicular
8 to the harness 8, is provided within the portion 4c to
9 engage the wire harness 8 and hold it rigidly in place
with respect to the switch bracket 4 and housing
11 member 3. The rearward end 30 of the housing member 3
12 is provided finally with an end cap 5 having external
13 threads 7a for engaging the internal threads 6 of the
14 housing member 3.
The wire harness 8 includes the fiber optic
16 bundle g and the switch wiring lOb. At the remote end
17 of wire harness 8 (not shown) bundle 9 terminates in a
18 fiber optic connector and switch wiring 106 terminates
19 in a wire connector. The fiber optic connector
engages a light detector (not shown) for detecting
21 light transmitted by the fiber optic bundle. The wire
22 connector is connected to the light detector circuitry
23 so as to actuate the detector whenever switch 11 is
24 actuated by contact of tip 15b with pressure sensitive
trip 12. The entire wire harness 8 projects through
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1 axial opening 5a in cap 5 and through the axial
2 opening 25 in the rear portion 4c of the switch
3 bracket 4. The harness 8 is held in place by set
4 screw 26. The wire harness 8 runs parallel to the
interconnecting portion 4d of the switch bracket 4 and
6 the switch wiring lOb branches off from the harness 8
7 to connect to terminals l~a of the switch 11. The
8 fiber optic bundle 9 is routed around switch 11 and
9 within opening 24 in the forward portion 4b of the
switch bracket 4, within the coil spring 14, between
11 the prongs 15 and 16 and through axial opening 2b in
12 support member 17.
13 The nose piece 1 includes light guiding
14 aperture 33 and supports an optional fiber optic lens
18, which is associated with the fiber optic bundle 9
16 by means of interface 19. It is contemplated that
17- interface 19 may be any convenient termination of the
18 bundle 9 which promotes the acceptance of light into
lg the element or elements of the bundle 9. For example,
the bundle 9 may terminate in a brass ferrule into
21 which the fiber optic element or elements are
22 adhesively secured. The end of the bundle 9 is then
23 polished to permit entry of light into the fiber optic
24 element or elements. The fiber optic bundle 9 and
lens 18 are rigidly supported with respect to the
26 housing member 3 and switch bracket 4.
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1 OPERATION 3F THE INVENTION
2 As described previously with respect to
3 Figures 1-4, the optical fiber bundle 9 and switch
4 wiring lOb feed and activate, respectively, a remotely
located light detector (not shown). The light
6 detector is used to detect the light provided by the
7 CRT with which the light pen of the invention is being
8 employed. By feeding back a signal representing the
9 detected light from the detector to the CRT, the
particular position of the light pen on the face of
11 the cathode ray tube can be determined and the image
12 or character information displayed at that position on
13 the CRT can be eliminated or changed.
14 A user grasps the light pen by housing
member 3 and gently places the nose piece 1 against
16` the face of the CRT with which the pen is associated.
17 When the nose piece 1 is located at the desired
18 position on the face of the CRT, the housing member 3
19 is firmly pressed against the CRT face causing the
2û nose piece 1 to retract into axial opening 3a and move
21 axially with respect to the housing member 3. The
22 light pen is configured such that during the rearward
23 movement of the nose piece 1, the actuator 2 is also
24 moved rearwardly, due to the contact between the nose
piece 1 and forward surface 2a of the actuator 2.
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1 This rearward movement of the actuator 2 causes the
2 coil spring 14 to compress and also moves the prongs
3 15 and 16 rearwardly. Rearward movement of prong 15
4 engages the pressure sensitive trip 12 of the switch
11, thereby actuating the remotely located light
6 detector and detecting the light which is transmitted
7 to the detector by the fiber optic bundle 9.
8 The light pen body 3 is dimensioned in such
9 a way that the tip 18b of the fiber optic lens 18 or
bundle 9, if no lens is used, is about a one-quarter
11 inch from the tip of the nose piece 1. In operation,
12 it is contemplated that the user would pick up the
13 light pen by housing member 3, place the tip 18b
14 against the face of the CRT and push gently toward the
screen until an audible feedback signal indicates that
16 the light at that point has been detected. The
17 pressure against the tip of the actuator forces it to
18 axially move within opening 3a, closing switch 11.
19 which is normally open. The light from the CRT passes
2û through the light guiding aperture 33 in the nose
21 piece 1 to the fiber optic bundle 9 or optional lens
22 18 which focuses the light nn interface 19 and fiber
23 optic bundle 9. The light is transmitted along the
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l fiber optic bundle 9, which is connected to the light
2 detector by a conventional fiber optic cable
3 connector. The connector is configured to position
4 the remote end of fiber optic bundle 9 adjacent to the
light detector so that light transmitted by the bundle
9 strikes the detector with little or no loss. The
7 light detector device contemplated for use in
8 combination with a light pen according to the
9 invention is a conventional combination
detector/amplifier. The output of this device is
11 applied to a conventional light pen amplifier and
12 pulse detector circuits associated with the CRT
13 chassis.
14 It should be noted that the use of the
fiber optic bundle 9 permits great versatility in the
16 selection and use of light detectors. For example, to
17 change a particular detector for different response to
18 color, phosphor, time, etc., does not require a
19 complete change or redesign of the light pen assembly
itself. Only the remotely located detector need be
21 changed. Furthermore, the light pen according to the
22 invention eliminates electrostatic interference with
23 sensitive light detector circuits. Static charges
24 which normally build on the CRT face plate and users'
hands cause static discharge which significantly
26 affects conventional light pens employing light
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1 detectors within the head of the pen. The light pen
2 according to the invention is not affected by such
3 static charges and discharges because the light
4 detector circuitry may be remotely located.
In addition, the reliability of the light
6 pen of the invention is found to be significantly
7 improved over the prior art. The fact that the light
8 pen according to the invention has only one moving
9 part to actuate the switch 11 avoids the need for
flexible wiring and moving light detectors, which are
11 normally employed in conventional light pens and are
12 subject to frequent failures.
13 It is also noted that the light pen
14 according to the invention improves producibility and
maintainability by avoiding the need for miniature
16 circuitry located within the head of the light pen.
17 the design, according to the invention, allows
18 conventional circuit packaging of the light detector
19 in the chassis of the CRT, for example, and requires
only the simple wiring of switch 11 in the light pen.
21 Figure 4 is an alternative embodiment of
22 the invention wherein the nose piece and actuator are
23 integrally combined into a single actuator assembly
24 100 located within the housing member 3. The assembly
100 is provided with support 101 for retaining the
26 optional fiber optic lens 18 and fiber optic bundle
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1 9. The end of assembly 100 terminates in flange 102
2 for engaging switch 11 and trip 12 for actuating the
3 detector connected thereto. Switch 102 supports the
4 fiber optic bundle 9 and switch wiring lOb. Trip 12
is spring-biased in the normally open position and
6 abuts flange 102 which retains the assembly 100 in a
7 position projecting from the body 3. This alternative
a embodiment operates in the same manner as the
9 embodiment of Figures 1-3.
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