Method and apparatus for predicting retinal illuminance

• US 5,738,430 A
• Filed: 08/07/1996
• Issued: 04/14/1998
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Asev Display Labs Inc. (AmTRAN Technology Co., Ltd.)
• Original Assignee: David Sarnoff Research Center, Inc.
• Inventors: Brill, Michael Henry
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US08/693,725
• Time in Patent Office: 615 Days
• Field of Search: 353/120, 353/122, 382/312, 382/321, 382/324, 348/78, 359/630
• US Class Current: 353/122
• CPC Class Codes: A61B 3/112 for measuring diameter of pupils

Abstract

A method and apparatus for predicting how any given spatio-temporal light distribution would change an observer'"'"'s pupil diameter. The method generates the instantaneous effect of luminance driving the pupil diameter, the cumulative driving function of the pupil diameter, and the evolving pupil diameter. Using the evolving pupil diameter together with the input luminance, the method computes the retinal illuminance distribution for the given input illuminance. The method is implemented as a software routine executed by a general purpose computer.

Claims

1. A method for predicting retinal illuminance with regard to an image depicted on an image display comprising the steps of:

generating an instantaneous effective luminance in response to luminance information representing luminance of each pixel in said video image;

computing a cumulative driving function of pupil diameter in response to the instantaneous effective luminance;

computing evolving pupil diameter in response to the cumulative driving function of pupil diameter; and

predicting retinal illuminance from the luminance information and the evolving pupil diameter.

2. The method of claim 1, wherein said step of generating said instantaneous effective luminance further comprises the step of evaluating

3. The method of claim 1, wherein said step of computing said cumulative driving function of pupil diameter further comprises the step of evaluating

4. The method of claim 3, wherein said step of solving said cumulative driving function of pupil diameter further comprises the step of evaluating

5. The method of claim 1, wherein said step of computing said cumulative driving function of pupil diameter further comprises the step of evaluating ##EQU5## where:

(cL)_cntrl (j·

dt ₁) is the cumulative driving function of pupil diameter for a sampling rate dt₁ , I_D is an image sequence;

space="preserve" listing-type="equation">H(τ

)=F(max 0,τ

!)-F(max 0,τ

-dt);

space="preserve" listing-type="equation">F(τ

'"'"')=-c( τ

-b!/c )+( τ

'"'"'-b !/c).sup.2/ 2!e .sup.(- τ

'"'"'-b!/c) u(τ

'"'"'-b );

N is 0.5 seconds/dt;

τ

is (j dt₁ -k dt); and

k is constrained by (j dt₁ /dt-N<

k<

j dt₁ /dt).

6. The method of claim 1, wherein said step of computing evolving pupil diameter further comprises the step of evaluating

7. The method of claim 1, wherein said step of computing retinal illuminance further comprises the step of evaluating

8. A method for predicting retinal illuminance with regard to a video image depicted on a video display comprising the steps of:

a) generating an instantaneous effective luminance in response to luminance information representing luminance of each pixel in said video image by evaluating

space="preserve" listing-type="equation">(cL).sub.eff (t)=5.7037D.sup.-3 ∫

dxdyL(x,y,t)(x.sup.2+ y.sup.2).sup.0.5

where (cL)_eff (t) is the instantaneous effective luminance, D is a viewing distance from a virtual observer to said video image, x and y are pixel location coordinates for each pixel in said video image, and L(x,y,t) is a luminance value of each pixel;

b) computing a cumulative driving function of pupil diameter in response to the instantaneous effective luminance by evaluating

space="preserve" listing-type="equation">(cL).sub.cntrl (t)=∫

dt'"'"' g(t-t'"'"')(cL).sub.eff (t'"'"')

where (cL)_cntrl (t) is the cumulative driving function of pupil diameter, and g(t) is an open-loop pupil-response function that is computed by evaluating

space="preserve" listing-type="equation">g(t)=0.5.sup.-3 (t-b).sup.2 e .sup. -(t-b)/c! u(t-b)

where b is 0.18 seconds, c is 0.1 seconds, and u is a unit step function;

c) computing evolving pupil diameter in response to the cumulative driving function of pupil diameter by evaluating

space="preserve" listing-type="equation">d(t)=5-3tan h 0.4 log.sub.10 {(cL).sub.cntrl (t)}!

where d(t) is the evolving pupil diameter; and

d) predicting retinal illuminance from the luminance information and the evolving pupil diameter by evaluating

space="preserve" listing-type="equation">B(x,y,t)=L(x,y,t)π

d(t)/2!.sup.2

where B(x,y,t) is the retinal illuminance.

9. A method for predicting retinal illuminance with regard to a video image depicted on a video display comprising the steps of:

a) generating an instantaneous effective luminance in response to luminance information representing luminance of each pixel in said video image by evaluating

space="preserve" listing-type="equation">(cL).sub.eff (t)=5.7037D.sup.-3 ∫

dxdyL(x,y,t)(x.sup.2+ y.sup.2).sup.0.5

where (cL)_eff (t) is the instantaneous effective luminance, D is a viewing distance from a virtual observer to said video image, x and y are pixel location coordinates for each pixel in said video image, and L(x,y,t) is a luminance value of each pixel;

b) computing a cumulative driving function of pupil diameter in response to the instantaneous effective luminance by evaluating ##EQU6## where (cL)_cntrl (j·

dt₁) is the cumulative driving function of pupil diameter for a sampling rate dt₁, I_D is an image sequence, where

space="preserve" listing-type="equation">H(τ

)=F(max 0,τ

!)-F(max 0,τ

-dt !),

space="preserve" listing-type="equation">F(τ

'"'"')=-c 1+( τ

'"'"'-b!/c)+( τ

'"'"'-b!/c).sup.2 !e .sup.(- τ

'"'"'-b!/c) u(τ

'"'"'-b), and

N is 0.5 seconds/dt, τ

is (j dt₁ -kdt), and k is constrained by (j dt₁ /dt-N<

k<

j dt₁ /dt);

c) computing evolving pupil diameter in response to the cumulative driving function of pupil diameter by evaluating

space="preserve" listing-type="equation">d(t)=5 -3 tan h 0.4 log.sub.10 {(cL).sub.cntrl (t)}!

where d(t) is the evolving pupil diameter, and (cL)_cntrl (t) is the cumulative driving function of pupil diameter; and

d) predicting retinal illuminance from the luminance information and the evolving pupil diameter by evaluating

space="preserve" listing-type="equation">B(x,y,t)=L(x,y,t)π

d(t)/2!.sup.2

where B(x,y,t) is the retinal illuminance.

10. Apparatus for predicting retinal illuminance with regard to an image depicted on an image display comprising:

means for generating an instantaneous effective luminance in response to luminance information representing luminance of each pixel in said video image;

means for computing a cumulative driving function of pupil diameter in response to the instantaneous effective luminance;

means computing evolving pupil diameter in response to the cumulative driving function of pupil diameter; and

means for predicting retinal illuminance from the luminance information and the evolving pupil diameter.