Visual privacy protection system
A visual privacy system unilaterally blocks rolling shutter cameras by providing a periodically interrupted ambient light source imposing bright and dark bands on the image yet at a frequency imperceptible to human observers in the environment. Communication of the modulation pattern to authorized cameras allows unaffected imaging in these regions by authorized individuals. The system also contemplates operation in a barcoding mode with a light modulation providing embedded barcodes that can be extracted from images taken in the region to indicate that the images were improperly acquired and to block the images in certain applications.
1. A visual privacy system comprising:
a privacy-enforced environment having a floor area of at least 100 square feet;
a plurality of LED light fixtures synchronously modulatable to provide at least 50 percent of an ambient illumination of the environment and its contents;
a modulator communicating with the light fixtures to synchronously modulate the light of the light fixtures between on and off values at a frequency above the flicker fusion rate to impose a banding in images taken by rolling frame shutter cameras relying on the ambient illumination for image acquisition, the banding completely obscuring portions of the image; and
wherein the modulator further provides a barcoding modulation pattern when an illumination in the environment by the LED light fixtures is below a predetermined percentage of the illumination in the environment, the barcoding modulation pattern imposing a non-obscuring banding in images taken by rolling frame shutter cameras relying on the ambient illumination for image acquisition and encoding a predetermined data pattern.
2. The visual privacy system of claim 1 wherein the modulator synchronously modulates the light of the light fixtures between on and off values at a frequency in excess of 400 Hz.
3. The visual privacy system of claim 2 wherein the modulator synchronously modulates the light of the light fixtures between on and off values at a frequency less than 2,000 Hz.
4. The visual privacy system of claim 3 wherein the modulator synchronously modulates the light of the light fixtures between on and off values with a duty cycle greater than 40 percent.
5. The visual privacy system of claim 1 wherein the ambient illumination provides an illumination within the environment of no less than 2000 Lux.
6. The visual privacy system of claim 1 , wherein the LED light fixtures provide separate red, green, and blue light sources that are independently modulatable and wherein the modulator provides different modulation frequencies to the red, green, and blue light sources.
7. A visual privacy system comprising:
a privacy-enforced environment having a floor area of at least 100 square feet;
a plurality of LED light fixtures synchronously modulatable to provide at least 50 percent of an ambient illumination of the environment and its contents;
a modulator communicating with the light fixtures to synchronously modulate the light of the light fixtures between on and off values at a frequency above the flicker fusion rate to impose a banding in images taken by rolling frame shutter cameras relying on the ambient illumination for image acquisition, the banding completely obscuring portions of the image; and
wherein the modulation varies among different frequencies in a nonrepeating pattern over an interval less than 1 second and such that time-adjacent different frequencies are not related by an integer multiple.
8. A visual privacy system comprising:
a privacy-enforced environment having a floor area of at least 100 square feet;
a plurality of LED light fixtures synchronously modulatable to provide at least 50 percent of an ambient illumination of the environment and its contents;
a modulator communicating with the light fixtures to synchronously modulate the light of the light fixtures between on and off values at a frequency above the flicker fusion rate to impose a banding in images taken by rolling frame shutter cameras relying on the ambient illumination for image acquisition, the banding completely obscuring portions of the image; and
further including at least one authorized camera positioned to view contents of the environment, the at least one authorized camera intercommunicating with the modulator to exchange a timing signal controlling timing of an image acquisition; and
wherein the timing signal synchronizes the modulation of the light fixtures and the image acquisition by the authorized camera to eliminate banding in images acquired by the at least one authorized camera.
9. The visual privacy system of claim 8 wherein the at least one authorized camera provides a rolling shutter in which rows of an image acquired by the at least one authorized camera are sequentially exposed and wherein the timing signal allows the at least one authorized camera to coordinate an exposure of each row with a time period to produce an exposure spanning a constant cumulative on-time of the plurality of light fixtures.
10. The visual privacy system of claim 9 wherein the timing signal indicates at least one of a frequency and a period of repetition of a modulation pattern and/or at least one of a beginning of a period of repetition and a phase of a modulation pattern.