Dual density display

• US 3,903,517 A
• Filed: 02/26/1974
• Issued: 09/02/1975
• Est. Priority Date: 02/26/1974
• Status: Expired due to Term

• Current Assignee: Recognition Equipment Incorporated
• Original Assignee: Raymond A. Hafner
• Inventors: Hafner, Raymond A.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/445,964
• Time in Patent Office: 553 Days
• Field of Search: 340/324AD,146.3ED 315/22,26 178/7.5D,7.5SE
• US Class Current: 348/732
• CPC Class Codes: G06V 10/987 with the intervention of an operator
• CPC Class Codes: G09G 1/04 Deflection circuits ; Constructional details not otherwise provided for electron-optical arrangements H01J29/46, H01J37/04, H01J37/302
• CPC Class Codes: G09G 5/227 Resolution modifying circuits, e.g. variable screen formats, resolution change between memory contents and display screen
• CPC Class Codes: G09G 5/40 characterised by the way in which both a pattern determined by character code and another pattern are displayed simultaneously, or either pattern is displayed selectively, e.g. with character code memory and APA, i.e. all-points-addressable, memory

Abstract

A display system using a CRT and capable of simultaneously displaying both a true video picture and matrix characters produced by a character generator. Such display is economically achieved by processing the matrix and video display signals in ways most compatible with each. A code responsive matrix display section includes a code word storage memory for storing the code words corresponding to the characters to be displayed, and a character generator responsive to the code words for producing the dot patterns of the matrix characters. A video display section responds to a digital signal which contains the actual video information for producing the dot pattern of the video picture. The CRT vertical and horizontal sweep rates are dynamically variable. A first rate, utilized with the matrix display section, produces individual dots which are sufficiently separated to generate readable matrix characters. A second rate, operational with the video display section, produces a denser dot pattern, making the individual dots in the video picture relatively imperceptible. In an illustrative application, the display system is adapted for use in a CRT key entry terminal for a re-entry document optical scanning system.

Claims

1. In a display system having a CRT, deflection means for causing an electron beam to sweep through successive lines on the face of the CRT, and means for selectively blanking the electron beam in synchronism with the sweep thereof to produce a dot pattern on the face of the CRT, the combination comprising, a code responsive character generator, a digitally responsive video generator, means for selectively enabling the character generator and the video generator for controlling the blanking means, and density control means for varying the deflection rate of said deflection means, said density control means arranged to be operable in conjunction with said enabling means for producing dot patterns of different densities under the control of the character generator and under the control of the video generator.

2. The display system as set forth in claim 1 wherein the deflection means includes horizontal and vertical deflection circuits, the density control means including means for varying deflection rate of both of said circuits.

3. In a matrix display system having a CRT, deflection means for causing an electron beam to sweep through spaced lines on the face of the CRT, means for selectively blanking the beam to produce dots on the face of the CRT, a character generator containing data representative of a plurality of dot patterns, the character generator being coupled to the blanking means for producing dot patterns on the CRT face represented by said contained data, the improvement comprising, means for preempting a portion of the CRT face for displaying a video picture, said preempting means including a digitally responsive video generator for producing the dot pattern of the video picture and density control means for increasing the dot density on the preempted portion of the CRT tube face.

4. In a display system having a CRT, horizontal and vertical deflection circuits for causing an electron beam to sweep through successive spaced lines on the face of the CRT, means for selectively blanking the electron beam in synchronism with the sweep thereof to produce dots on the face of the CRT, a source of digital code words representative of characters selected from a predetermined set for display, each of said characters being formable from a patterned matrix of dots, and a source of digital data representative of a video picture for display, the combination comprising, a character generator containing data representative of the patterned matrix of dots for forming each of the characters of said set, means for operatively coupling the selected code words to the character generator and the character generator to the blanking means so that the electron beam is selectively blanked while sweeping the face of the CRT to produce the dot pattern corresponding to each of the selected code words, a video generator for operatively coupling the digital data representative of the video picture to the blanking means so that the electron beam is selectively blankeD while sweeping the face of the CRT to produce the video picture, and means for selectively enabling the character generator and the video generator.

5. The display system as set forth in claim 4, further including means responsive to the enabling of the video generator for dynamically decreasing the deflection rate of said horizontal and vertical deflection circuits whereby the video picture is displayed with a dot pattern which is denser than the matrix dot pattern.

6. The display system as set forth in claim 5 further including first storage means interposed between the source of code words and the character generator for storing the selected code words and coupling said selected code words in sequence to the character generator.

7. The display system as set forth in claim 6 wherein the first storage means includes a recirculating shift register adapted to couple said selected code words to the character generator in a recurring sequence timed with successive sweep lines so that the dot pattern of each level of the matrix is individually produced.

8. The display system as set forth in claim 6 further including second storage means interposed between the source of digital data and the video generator.

9. The display system as set forth in claim 5 wherein the enabling means alternately enables the character generator during a first series of scan lines and the video generator during a second series of scan lines whereby the CRT simultaneously displays the selected characters and the video picture.

10. In a display system having a CRT, deflection means for causing an electron beam to sweep through successive lines on the face of the CRT, means for selectively blanking the electron beam to produce dots on the face of the CRT, a source of digital code words representative of a pattern of dots selected for display from a predetermined set of patterns, and a source of digital data representative of a video picture for display, the combination comprising a character generator containing data representative of each of the dot patterns of said set, means for coupling selected code words to the character generator, means for coupling the character generator to the blanking means so that the electron beam is selectively blanked while sweeping the face of the CRT to produce the dot patterns corresponding to each of the selected code words, a video generator, means for coupling the digital data representative of the video picture to the video generator, means for coupling the video generator to the blanking means so that the electron beam is selectively blanked while sweeping the face of the CRT to produce the video picture, means for selectively enabling the character generator and the video generator, and means responsive to the enabling of the video generator for dynamically decreasing the deflection rate of said deflection means whereby the dot density is increased for display of the video picture.

11. In a display system having a CRT, means for causing an electron beam to sweep through successive spaced lines on the face of the CRT to produce a scan thereof in a raster pattern, means for selectively blanking the electron beam in synchronism with the scan thereof to produce a dot pattern on the face of the CRT, a source of digital code words representative of characters selected from a predetermined set for display, each of said characters being formable from a patterned matrix of dots, a source of digital data representative of the dot pattern of a video picture for display, the combination comprising, a matrix display section, a video display section, and means for selectively enabling said matrix and video display sections, the matrix display section comprising code word storage means coupled to the source of digital code words for storing said selected code words, a character generator containing data representative of the patterned matrix of dots for forming each of the characters of said set, the character generator operatively interpOsed between the code word storage means and the blanking means to produce the dot patterns of said selected characters on the face of the CRT, means for producing a relatively coarse sweep rate so that the dots in the matrix are spaced to produce matrix characters of readable size on the face of the CRT, the video display section comprising video storage means coupled to the source of digital data for storing said digital data, a video generator operatively interposed between the video storage means and the blanking means to produce the dot pattern of the video picture on the face of the CRT, means for producing a relatively fine sweep rate so that the individual dots in the video picture are relatively imperceptible to produce a continuous video picture, whereby the CRT face may display both matrix characters and a video picture with a dot density compatible with each.

12. The display system as set forth in claim 11 wherein the enabling means selectively enables the video and matrix display sections during respective portions of each scan whereby the CRT displays the matrix characters and the video picture simultaneously.

13. An optical scanning system for use with documents containing characters of a predetermined set, each of said characters having a corresponding code word, comprising in combination, scanning means for optically scanning the characters on the documents and for producing a digital video signal containing the dot pattern of said scanned characters, recognition means for receiving the digital video signal and for producing the code word corresponding to each of the characters recognized in said digital video signal, means coupled to the recognition means for storing said code words, means for producing a first signal in response to the failure of the recognition means to recognize a character in said digital video signal, a CRT display having a character generator responsive to said set of code words, the CRT being adapted to display a representation of said characters formable from a matrix of dots, said first signal causing the display of the matrix representation of the recognized characters on a first portion of the CRT face, means for preempting a second portion of the CRT face in response to said first signal, said preempting means including a video generator, means for coupling said digital video signal to the video generator for producing the dot pattern of the scanned unrecognized character, density control means for increasing the dot density on the preempted portion of the CRT face, and a keyboard located near the CRT and having a key corresponding to each of the characters of said set, each key of the keyboard being adapted to produce the code word corresponding to the associated character in response to the depression thereof and to couple the produced code word to the storage means, whereby the CRT and keyboard allow an operator to enter the code word corresponding to unrecognized characters into the storage means.