CRT device light versus input signal characteristic function

• US 4,862,265 A
• Filed: 09/01/1988
• Issued: 08/29/1989
• Est. Priority Date: 09/01/1988
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Hartmann, Wayne T., Darrow, William K., Bartow, Richard E.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Kostak, Victor R.
• Application Number:
  US07/239,246
• Time in Patent Office: 362 Days
• Field of Search: 358/139, 358/10, 358/32, 358/164, 358/243, 358/903, 358/242, 358/29, 324/404, 356/121, 371/20, 371/25, 371/26, 371/27, 340/703
• US Class Current: 348/191
• CPC Class Codes: H04N 17/04 for receivers

Abstract

The present invention is a system and a method for measuring and then predicting the light output from a cathode ray tube device as a function of the input signal to the device. An input signal series is selected and a table is formed indicating the light output level for each signal input level. Parameters of a characteristic equation are then determined by a regression and an automatic or manual optimization process. The optimum values of these parameters (units-converter constant, gain, offset, and gamma) are then used to predict the light output from the measured device.

Claims

1. A method for determining the light output from a cathode ray tube device comprising the steps of:

(a) positioning a light sensor to receive the light output from the cathode ray tube as a function of differing valued input signals driving the device;

(b) forming a light table of light measurement values for each value of each input signal;

(c) determining the optimum values of K, G, O and γ

utilizing a predicted light equation,

space="preserve" listing-type="equation">L=K(GS+O).sup.γ

by using the sum of the percent differences between the light measurement values and the predicted light values,

where;

L=predicted phosphor-light output

K=a constant which converts a specific unit of signal into a specific unit of light

S=input signal to the device

G=device gain

O=device offset, and

γ

=an exponential relationship between a CRT'"'"'s drive signal and its light output.

2. A method for determining the light output from a cathode ray tube as a function of the input signal driving the device comprising the steps of:

(a) rigidly positioning a light meter'"'"'s sensor to receive the light output of the cathode ray tube and to provide an output signal having a value corresponding to the received light;

(b) setting the input signal to a series of discrete values;

(c) at each discrete signal input value, form an entry in a light table for each corresponding value of the light sensor output signal;

(d) forming a sum of a percent difference from the measured light and the predicted light to establish an error value;

(e) determining the preferred values of K, G, O and γ

based on the equation;

L=K(GS+O).sup.γ

where;

L=predicted phosphor-light output

K=a constant

S=input signal to the device

G=device gain

O=device offset and

γ

=an exponential relationship between a CRT'"'"'s drive signal and its light output, by;

(a) an automatic minimization process selecting one of the following;

(i) minimization of the said error value by adjusting the said G term and then the said O term

(ii) minimization of the said error value by adjusting the said O term and then the said G term

(iii) minimization of the said error value by holding the said G term at a constant and adjusting the said O term

(b) a manual minimization process; and

(h) using the light table values and the preferred values of step (e) to predict the light output from a cathode ray tube for selected discrete values of the input signal.

3. A system for determining the light output from a cathode ray tube device comprising:

a cathode ray tube device having an input for receiving an input signal and an output for providing light as a function of the input signal;

a light sensor rigidly linked to said cathode ray tube device for receiving the light therefrom and for transforming the received light to electrical signals;

a signal generator having its output connected to the input of said cathode ray tube device, which signal generator is responsive to various levels of its own input for generating said input signal to said cathode ray tube device; and

computer means having table formation capabilities, for receiving as an input the electrical signals from said light sensor, for directing as an input to said signal generator, formed table values which consist of the light values corresponding to the received electrical signals and the various levels of the input to said signal generator; and

for forming a characteristic equation of the type L=K(GS+O).sup.γ

from the values stored in said table;

where;

L=predicted phosphor-light output

K=a constant

S=input signal to the device

G=device gain

O=device offset and

γ

=an exponential relationship between a CRT'"'"'s drive signal and its light output,

4. A system for determining the light output from a cathode ray tube device comprising:

a first CRT monitor device response to RGB input signals;

a second CRT monitor device responsive to standard encoded input signals;

a light sensor for repeated optical coupling to said first and said second monitor devices;

a computer means for running a two-stage program;

a host signal generator compatible with said first monitor device;

a standard signal generator compatible with said second monitor device;

a standard encoder means compatible with said second monitor device;

a first switch means having a first and a second switch position for connecting the output of said standard signal generator and the host signal generator, respectively, to the inputs of said first monitor device and said standard encoder means;

a second switch means having a first and a second switch position for connecting said signal path of said first switch and said standard encoder means, respectively, to the input of said second monitor device;

an output device coupled to said computer means; and

whereby said computer means operates to provide requested signal levels to the standard or the host signal generators for the purpose of forming a table of light values received from said light sensor and said requested signal levels; and

for generating a characteristic equation which predicts the light from the CRT of the monitor device as a function of input signals to the device.