BRIGHTNESS CONTROL OF A STATUS INDICATOR LIGHT

• US 20080111500A1
• Filed: 11/09/2006
• Published: 05/15/2008
• Est. Priority Date: 11/09/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Hoover, Bryan
• Granted Patent: US 8,373,355 B2
• Time in Patent Office: Days
• US Class Current: 315/293
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light

Abstract

An apparatus and method for controlling the brightness and luminance of a light, such as an LED. The embodiment may vary the brightness and luminance of the LED in a variety of ways to achieve a variety of effects. The exemplary embodiment may vary the rate at which the LED'"'"'s luminance changes, such that an observer perceives the change in the LED'"'"'s brightness to be smooth and linear as a function of time, regardless of the ambient light level. Changes to the LED'"'"'s luminance may be time-constrained and/or constrained by a maximum or minimum rate of change.

Claims

1. A method for varying a luminance of a light, comprising:

varying an input to the light, the input affecting the luminance;

setting a threshold value for the luminance of the light; and

adjusting a rate of change of the input when the luminance is below the threshold.

2. The method of claim 1, wherein the light is chosen from the group comprising:

a light-emitting diode; and

a liquid crystal display.

3. The method of claim 1, wherein the threshold value is a pulse-width modulation value.

4. The method of claim 1, wherein the input is a pulse-width modulation output generated by a pulse-width modulation control circuit.

5. The method of claim 4, wherein:

the luminance is increasing; and

the operation of adjusting a rate of change of the input comprises increasing the rate of change of a duty cycle of the pulse-width modulation output.

6. The method of claim 4, wherein:

the luminance is decreasing; and

the operation of adjusting a rate of change of the input comprises decreasing the rate of change of a duty cycle of the pulse-width modulation output relative to a previously-determined rate.

7. The method of claim 6, wherein the operation of setting a threshold value for the luminance of the light comprises setting a threshold value for the pulse-width modulation output.

8. The method of claim 7, further comprising:

in the event the pulse-width modulation output is above the threshold, permitting the pulse-width modulation output to vary by a previously-determined change per time increment.

9. The method of claim 7, wherein the operation of adjusting a rate of change of the input when the luminance is below the threshold comprises:

in the event the pulse-width modulation output is below the threshold, subtracting the current pulse-width modulation output from the threshold to yield a threshold distance;

determining a slope adjustment;

determining if an initial rate of change is less than the slope adjustment; and

in the event the initial rate is less than the slope adjustment, permitting the pulse-width modulation output to change by a minimum increment.

10. The method of claim 9, wherein the slope adjustment is directly proportional to the threshold distance.

11. The method of claim 9, further comprising:

in the event the initial rate exceeds the slope adjustment, determining if the initial rate minus the slope adjustment is less than the minimum increment;

in the event the initial rate minus the slope adjustment is less than the minimum increment. changing the pulse-width modulation output by the minimum increment;

otherwise, changing the pulse-width modulation output by the initial rate minus the slope adjustment.

12. An apparatus operative to perform the method of claim 1.

13. An apparatus operative to perform the method of claim 9.

14. A method for varying a luminance of a light, comprising:

determining a target change in a signal, the signal setting the luminance of the light;

determining the lesser of the target change and a maximum allowed change; and

limiting a change in the signal to the lesser of the target change and the maximum allowed change, thereby limiting a rate of change in the luminance of the light.

15. The method of claim 14, wherein the light is a light-emitting diode.

16. The method of claim 14, wherein the maximum allowed change is user-selectable.

17. The method of claim 15, wherein:

the signal is a pulse-width modulation signal having a duty cycle; and

the change in the signal is a change in the signal'"'"'s duty cycle.

18. A method for varying a luminance of a light, comprising:

setting a target luminance of the light; and

changing the luminance of the light from a current luminance to the target luminance;

wherein

the operation of changing the luminance of the light from the current luminance to the target luminance occurs within a predetermined time.

19. The method of claim 18, further comprising:

determining an ambient light level;

wherein

the operation of setting a target luminance of the light is based on the ambient light level.

20. The method of claim 18, wherein the light is chosen from the group comprising:

a light-emitting diode;

a liquid crystal display;

a cathode ray tube device; and

a plasma display.

21. The method of claim 18, wherein the predetermined time is a dwell time of a breathing curve.

22. The method of claim 21, further comprising:

changing the luminance of the light from the target luminance to a high luminance;

maintaining the high luminance for a period; and

changing the luminance of the light from the high luminance to the target luminance after the period.

23. The method of claim 21, wherein:

the dwell time comprises a first segment, second segment and third segment;

the luminance changes from the current luminance to the target luminance by a first rate during the first segment, a second rate during the second segment and a third rate during the third segment.

24. The method of claim 23, wherein the second rate exceeds the first rate and third rate.

25. An apparatus configured to execute the method of claim 24.

26. The method of claim 24, wherein at least the operation of changing the luminance of the light from a current luminance to the target luminance occurs only during a specific time of day.

27. A method for changing a luminance of a light, comprising:

determining a target luminance to be reached by the luminance of the light;

determining a minimum time in which the target luminance may be reached;

setting a minimum number of increments necessary to vary the luminance from an initial luminance to the target luminance; and

changing the luminance of the light from the initial luminance to the target luminance in a number of increments at least equal to the minimum number of increments.