Thick backlight for RGB LED of a liquid crystal display used in a virtual reality head mounted display
A liquid crystal display (LCD) device including a backlight with vertically stacked light emitting diodes (LEDs). The LCD device includes an LCD panel and a backlight for illuminating the LCD panel. The backlight includes a plurality of LEDs and a light guide. The plurality of LEDs are stacked vertically and disposed behind the LCD panel along one or more edges of the LCD panel. The plurality of LEDs include at least a first color LED and a second color LED emitting first light and second light at a first direction, respectively, at a first wavelength and a second wavelength, respectively. The light guide is disposed behind the LCD panel and adjacent to the plurality of LEDs. The light guide is configured to combine the first light and the second light received from the plurality of LEDs into combined light to illuminate the LCD panel.
1. A liquid crystal display (LCD) device, comprising:
an LCD panel;
a backlight for illuminating the LCD panel, the backlight including:
a plurality of light emitting diodes (LEDs) stacked vertically and disposed behind the LCD panel along one or more edges of the LCD panel, the plurality of LEDs including at least a first color LED and a second color LED emitting first light and second light at a first direction, respectively, at a first wavelength and a second wavelength, respectively, the first color LED including a first emission response time and the second color LED including a second emission response time that is different from the first emission response time; and
a light guide disposed behind the LCD panel and adjacent to the plurality of LEDs, the light guide configured to:
combine the first light and the second light received from the plurality of LEDs into combined light to illuminate the LCD panel; and
direct the combined light to the pixels of the LCD panel in a second direction; and
a controller configured to:
drive a lower efficiency color LED of the first and second color LEDs with a first current level and drive a higher efficiency color LED of the first and second color LEDs with a second current level lower than the first current level; and
drive the first color LED with a first pulsed signal and drive the second color LED with a second pulsed signal including a timing offset from the first pulsed signal to adjust for the first emission response time being different from the second emission response time and match timing of light emission output from the first color LED and the second color LED.
2. The LCD device of claim 1 , wherein:
the plurality of LEDs includes a third color LED stacked with the first and second color LEDs.
3. The LCD device of claim 2 , wherein:
the plurality of LEDs includes a fourth color LED stacked with the first, second, and third color LEDs;
the first color LED is a red LED, the second color LED is a green LED, the third color LED is a blue LED, and the fourth color LED is a blue LED.
4. The LCD device of claim 1 , wherein the first color LED is included in a first LED assembly and the second color LED is included in a second LED assembly separate from the first LED assembly, and the first LED assembly and second LED assembly are stacked vertically.
5. The LCD device of claim 1 , wherein both the first color LED and the second color LED are included in a single LED assembly.
6. The LCD device of claim 1 , wherein the plurality of LEDs include a first array of LEDs vertically stacked with a second array of LEDs, the first array of LEDs stacked with an offset relative to the second array of LEDs.
7. The LCD device of claim 6 , wherein the first array of LEDs and the second array of LEDs each includes first color LEDs and second color LEDs.
8. The LCD device of claim 6 , wherein the first array of LEDs and the second array of LEDs each include a red LED, a green LED, and a blue LED.
9. The LCD device of claim 1 , wherein:
the first light includes a first emission spectrum and the second light including a second emission spectrum different from the first emission spectrum; and
the controller is further configured to control an emission spectrum of the combined light based on controlling the first emission spectrum of the first color LED relative to the second emission spectrum of the second color LED.
10. A head mounted display (HMD), comprising:
a liquid crystal display (LCD) device, including:
an LCD panel;
a backlight for illuminating the LCD panel, the backlight including:
a plurality of light emitting diodes (LEDs) disposed behind the LCD panel along one or more edges of the LCD panel, the plurality of LEDs including at least a first color LED and a second color LED emitting first light and second light at a first direction, respectively, at a first wavelength and a second wavelength, respectively, the first color LED including a first emission response time and the second color LED including a second emission response time that is different from the first emission response time; and
a light guide disposed behind the LCD panel and adjacent to the plurality of LEDs, the light guide configured to:
combine the first light and the second light received from the plurality of LEDs into combined light to illuminate the LCD panel; and
direct the combined light to the pixels of the LCD panel in a second direction; and
a controller configured to:
drive a lower efficiency color LED of the first and second color LEDs with a first current level and drive a higher efficiency color LED of the first and second color LEDs with a second current level lower than the first current level; and
drive the first color LED with a first pulsed signal and drive the second color LED with a second pulsed signal including a timing offset from the first pulsed signal to adjust for the first emission response time being different from the second emission response time and match timing of light emission output from the first color LED and the second color LED.
11. The HMD of claim 10 , wherein the plurality of LEDs include a first array of LEDs vertically stacked with a second array of LEDs with an offset between the first array and the second array such that centers of LEDs of the first array of LEDs align with spaces between adjacent LEDs of the second array LEDs, adjacent LEDs of the first array of LEDs being spaced apart by a distance and adjacent LEDs of the second array of LEDs being spaced apart by the distance.
12. The HMD of claim 10 , wherein:
the plurality of LEDs includes a third color LED stacked with the first and second color LEDs.
13. The HMD of claim 12 , wherein:
the plurality of LEDs includes a fourth color LED stacked with the first, second, and third color LEDs;
the first color LED is a red LED, the second color LED is a green LED, the third color LED is a blue LED, and the fourth color LED is a blue LED.
14. The HMD of claim 10 , wherein the first color LED is included in a first LED assembly and the second color LED is included in a second LED assembly separate from the first LED assembly, and the first LED assembly and second LED assembly are stacked vertically.
15. The HMD of claim 10 , wherein both the first color LED and the second color LED are included in a single LED assembly.
16. The HMD of claim 10 , wherein the plurality of LEDs include a first array of LEDs vertically stacked with a second array of LEDs, the first array of LEDs stacked with an offset relative to the second array of LEDs.
17. The HMD of claim 16 , wherein the first array of LEDs and the second array of LEDs each includes first color LEDs and second color LEDs.
18. The HMD of claim 16 , wherein the first array of LEDs and the second array of LEDs each include a red LED, a green LED, and a blue LED.
19. The HMD of claim 10 , wherein:
the first light includes a first emission spectrum and the second light including a second emission spectrum; and
the controller is further configured to control an emission spectrum of the combined light based on controlling the first emission spectrum of the first color LED relative to the second emission spectrum of the second color LED.
20. The LCD device of claim 1 , wherein the plurality of LEDs include a first array of LEDs vertically stacked with a second array of LEDs with an offset between the first array and the second array such that centers of LEDs of the first array of LEDs align with spaces between adjacent LEDs of the second array LEDs, adjacent LEDs of the first array of LEDs being spaced apart by a distance and adjacent LEDs of the second array of LEDs being spaced apart by the distance.