Cordless light pen

• US 4,677,428 A
• Filed: 06/07/1985
• Issued: 06/30/1987
• Est. Priority Date: 06/07/1985
• Status: Expired due to Fees

• Current Assignee: HEI, Inc.
• Original Assignee: HEI, Inc.
• Inventors: Bartholow, Paul A.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US06/742,399
• Time in Patent Office: 753 Days
• Field of Search: 455/617, 455/603, 340/707, 340/708
• US Class Current: 345/180
• CPC Class Codes: G06F 3/0386 for light pen

Abstract

A cordless light pen for use with a cathode ray tube display screen as a data input for a digital computer. Contained within the exterior barrel of the pen is a depressible tip having a core made from a plastic which has been treated and whose index of refraction causes light entering in a direction parallel to the longitudinal axis of the core to pass through. The other end of the tip is operatively disposed relative to a light sensor. Also contained within the barrel of the cordless pen is a circuit card containing circuitry for amplifying, filtering and shaping the signals from the light sensor and to discriminate between signals due to the CRT sweep in the field of view of the tip and ambient noise. The so-called "hits" occasioned by the passage of the CRT beam past the tip member when it is depressed cause an IR LED to be energized to produce a directed beam of IR energy. The IR energy is transmitted to a receiver positioned to detect it, provided the light pen is held on the face of the CRT screen. The receiver output is fed to the digital computer driving the CRT display causing the dot and line counts (refresh address coordinates) to be latched. With this latched information, the computer is able to determine the coordinate location on the face of the CRT screen where the hit occurred and is made to carry out a preprogrammed function as a result of the detected hit. The receiver is designed to provide a high degree of noise masking.

Claims

1. A cordless light pen comprising:

(a) a hollow, generally cylindrical barrel member having a first end and a second end;

(b) an end cap member secured to said first end of said barrel member, said end cap member being formed from a light energy transmissive material and containing a light source;

(c) a source of potential and switch means contained within said barrel member, said switch means being operatively coupled to said light source and to said source of potential;

(d) a tip member reciprocally movable within said barrel member and having a first end portion thereof extending outwardly from said second end of said barrel member and a second portion within said barrel comprising a longitudinally extending light transmitting channel which terminates at the other end of said tip member within said barrel;

(e) a light sensor disposed adjacent said other end of said tip member proximate said light transmitting channel for producing electrical signals upon receipt of light energy from a source external to said barrel; and

(f) an electronic circuit containing amplifying means, filtering means and comparator means connectable through said switch means to said source of potential and responsive to said electrical signals for driving said light source when said switch means changes from a normally open condition to a closed condition upon depression of said reciprocally movable tip member.

2. The light pen as in claim 1 and further including:

(a) frame means insertable into said barrel member for maintaining a predetermined longitudinal spacing between said source of potential and said light sensor; and

(b) a substrate having a pattern of printed wiring thereon, said substrate being secured to said frame means and supporting said circuit and said switch means thereon.

3. The light pen as in claim 2 wherein said tip member includes an extension projecting from the first end thereof and said frame means includes guide means for slidingly receiving said extension.

4. The cordless light pen as in claim 3 wherein said switch means comprises first and second magnetic reed switches and wherein the actuating magnet for said magnetic reed switches is affixed to said extension and reciprocally movable therewith relative to said frame means.

5. A cordless light pen comprising:

(a) a generally cylindrical, hollow barrel member having first and second ends;

(b) a tip member mounted for reciprocating movement within said barrel, a portion of said tip member extending outwardly from said first end of said barrel, said tip member containing a light transmitting conduit extending lengthwise from end-to-end of said tip member;

(c) frame means disposed within said barrel having one end thereof adjacent the end of said tip member which is contained within said barrel member;

(d) a photo-sensing element supported by said frame and positioned to receive light energy passing through said conduit;

(e) a printed circuit card having a pattern of conductors formed thereon and supporting electrical components comprising signal amplifying, signal filtering and signal level comparison means;

(f) an electrical energy source contained within said barrel;

(g) a light energy transmitting means located proximate the end of said barrel opposite to said tip member;

(h) first and second switching means operated by the reciprocating movement of said tip member for connecting said electrical energy source to said printed circuit card and for connecting said electrical energy source to said light transmitting means; and

(i) means connected in circuit with said second switching means and with said comparator means for causing said light transmitting means to be energized by light energy of a predetermined intensity traveling through said light transmitting conduit when said tip member is depressed into said barrel member.

6. A cordless light pen system comprising:

(a) a hand-held instrument having a light conducting tip member for picking up light energy emanating from a display screen disposed at one end of said instrument and a light energy transmitting means at the other end of said instrument, said instrument further including

(i) light-to-electrical transducing means coupled to said tip member for producing an electrical signal proportional to the light intensity reaching said transducing means,

(ii) signal processing means coupled to said transducing means for producing an output signal when said electrical signal exceeds a predetermined threshold level, and

(iii) means coupling said output signal to said light energy transmitting means; and

(b) a separate light energy receiving means positioned in the field of view of said light energy transmitting means, said light energy receiving means including

(i) light energy sensing means for receiving light energy from said light energy transmitting means and producing an electrical signal proportional thereto,

(ii) signal amplifying means and filtering means coupled to receive said electrical signal produced by said light energy sensing means,

(iii) comparator means coupled to the output of said amplifying and filtering means for producing a hit signal when said output of said amplifying and filtering means exceeds a predetermined reference level,

(iv) pulse generating means for producing an acquire signal, and

(v) delay means operatively coupled to said pulse generating means and to said comparator means for inhibiting said pulse generating means from producing said acquire signal when said hit signals emanating from said comparator means occur at a rate below a predetermined lower rate limit.

7. The cordless light pen system of claim 6 wherein said pulse generating means comprises a first retriggerable monostable multi-vibrator having its trigger input coupled to the output of said comparator means and its output coupled to said delay means and a second retriggerable monostable multi-vibrator having its enable input connected to the output of said delay means, its trigger input coupled to the output of said comparator means, said acquire signal being obtained at the output of said second retriggerable monostable multi-vibrator.

8. The cordless light pen system of claim 7 wherein said delay means comprises a voltage comparator having first and second input terminals and an output terminal, said first input terminal being connected to a source of reference voltage and said second input terminal being coupled to said output of said first retriggerable monostable multi-vibrator through a resistance/compacitance charging circuit, said output terminal of said voltage comparator being coupled to said enable input of said second retriggerable monostable multi-vibrator.