Full-spectrum flash for electronic devices
Introduced here are light sources for flash photography configured to produce high-fidelity white light that is tunable over a broader range of correlated color temperatures (CCTs) than conventional flash technologies. The light source can include multiple independently controllable color channels representing illuminants (e.g., light-emitting diodes) of different colors with varying degrees of saturation. Operating collectively, the multiple color channels can produce a high spectral quality white light corresponding to different CCTs (e.g., “warm” white light having a red hue, “cool” white light having a blue hue). Operating independently, these same color channels can be pre-flashed in a variety of prescribed sequences to probe the spectral characteristics of a scene, thereby allowing for an enhanced, spectrally matched white flash as well as collecting per-pixel reflectivity data that can be later used in during post processing of the captured image.
1. A method for capturing an image, the method comprising:
accessing a database that associates one or more color mixing models with previously recorded spectral properties of a multi-channel light source,
wherein the multi-channel light source includes at least three color channels, each of which includes one or more illuminants configured to produce a substantially similar color;
characterizing a spectral property of the multi-channel light source by
producing a series of flashes in which each color channel is separately illuminated,
causing a series of images to be captured in conjunction with the series of flashes,
identifying a spectral characteristic of each color channel by examining the image in the series of images that is associated with the corresponding flash, and
examining the spectral characteristics to discover the spectral property of the multi-channel light source;
identifying an appropriate color mixing model from among the one or more color mixing models based on the spectral property; and
simultaneously driving the at least three color channels by separately addressing each color channel in accordance with the appropriate color mixing model, thereby causing the multi-channel light source to produce a flash of white light having a particular correlated color temperature (CCT).
2. A method for capturing an image, the method comprising:
accessing a database that associates one or more color mixing models with previously recorded spectral properties of a multi-channel light source,
wherein the multi-channel light source includes at least three color channels, each of which includes one or more illuminants configured to produce a substantially similar color;
characterizing a spectral property of the multi-channel light source by
producing a reference flash in which the at least three color channels are simultaneously illuminated,
causing a reference image to be captured in conjunction with the reference flash,
producing a series of flashes in which all color channels except one are simultaneously illuminated,
causing a series of images to be captured in conjunction with the series of flashes,
identifying a spectral characteristic of each color channel by estimating a corresponding discoloration effect,
wherein the corresponding discoloration effect for a given color channel is estimated by comparing the image associated with the flash in which the given color channel was not illuminated to the reference image, and
examining the spectral characteristics to discover the spectral property of the multi-channel light source;
identifying an appropriate color mixing model from among the one or more color mixing models based on the spectral property; and
simultaneously driving the at least three color channels by separately addressing each color channel in accordance with the appropriate color mixing model, thereby causing the multi-channel light source to produce a flash of white light having a particular correlated color temperature (CCT).
3. The method of claim 1 , wherein the multi-channel light source includes at least five color channels.
4. The method of claim 1 , wherein the multi-channel light source includes at least seven color channels.
5. The method of claim 1 , wherein the multi-channel light source includes four color channels configured to produce red light, blue light, green light, and white light.
6. The method of claim 1 , wherein the multi-channel light source includes four color channels configured to produce red light, blue light, green light, and amber light.
7. The method of claim 1 , wherein the multi-channel light source includes five color channels configured to produce red light, blue light, amber light, cyan light, and lime light.
8. The method of claim 1 , wherein the one or more illuminants in each color channel are light-emitting diodes (LEDs).
9. The method of claim 2 , wherein the multi-channel light source includes at least five color channels.
10. The method of claim 2 , wherein the multi-channel light source includes at least seven color channels.
11. The method of claim 2 , wherein the multi-channel light source includes four color channels configured to produce red light, blue light, green light, and white light.
12. The method of claim 2 , wherein the multi-channel light source includes four color channels configured to produce red light, blue light, green light, and amber light.
13. The method of claim 2 , wherein the multi-channel light source includes five color channels configured to produce red light, blue light, amber light, cyan light, and lime light.
14. The method of claim 2 , wherein the one or more illuminants in each color channel are light-emitting diodes (LEDs).