Image display system, movable object, and image display method
View Patent ↗The image display system includes a processing unit and a driving unit. The processing unit is configured to receive an image signal indicative of an instruction value of luminance of a light source. The driving unit is configured to supply a drive current to the light source in accordance with the instruction value indicated by the image signal received by the processing unit. The driving unit includes a shaping circuit and an adjusting unit. The shaping circuit includes a plurality of D/A converters and an arithmetic unit. The arithmetic unit is configured to output the drive current to the light source based on a computation result of analog signals outputted from the plurality of D/A converters. The adjusting unit is configured to determine values of digital signals inputted into the plurality of D/A converters of the shaping circuit in accordance with the instruction value.
1. An image display system for forming an image by use of light from a light source of a luminaire, the image display system comprising:
a processing unit configured to receive an image signal indicative of an instruction value of luminance of the light source; and
a driving unit configured to supply a drive current to the light source in accordance with the instruction value indicated by the image signal received by the processing unit,
the driving unit including a shaping circuit and an adjusting unit,
the shaping circuit including
a plurality of D/A converters each configured to, in response to input of a digital signal, output an analog signal corresponding to a value of the digital signal, and
an arithmetic unit configured to output the drive current to the light source based on a computation result of analog signals outputted from the plurality of D/A converters, and
the adjusting unit being configured to determine values of digital signals inputted into the plurality of D/A converters of the shaping circuit in accordance with the instruction value.
2. The image display system according to claim 1 , wherein
the plurality of D/A converters each have a value of an analog signal linearly changing relative to a value of a digital signal.
3. The image display system according to claim 1 , wherein
the plurality of D/A converters include at least a first D/A converter and a second D/A converter which are different in amount of change in an analog signal relative to a value of a digital signal.
4. The image display system according to claim 3 , wherein
the adjusting unit is configured to divide a series of bits indicative of the instruction value into a series of lower bits including a least significant bit and a series of upper bits including a most significant bit, and is configured to provide a digital signal based on the series of lower bits to the first D/A converter and provide a digital signal based on the series of upper bits to the second D/A converter.
5. The image display system according to claim 3 , wherein
the adjusting unit is configured to provide a digital signal having a value changing in accordance with at least the instruction value to the first D/A converter when the instruction value falls within a first numerical range, and is configured to provide a digital signal having a fixed value to the first D/A converter and provide a digital signal having a value changing in accordance with at least the instruction value to the second D/A converter when the instruction value falls within a second numerical range of numerical values larger than those of the first numerical range.
6. The image display system according to claim 5 , wherein
the adjusting unit is configured to provide, to the first D/A converter, a digital signal allowing the first D/A converter to output an analog signal with a value of zero when the instruction value is equal to a lower limit value of the first numerical range.
7. The image display system according to claim 5 , wherein
the adjusting unit is configured to provide, to the first D/A converter, a digital signal allowing the first D/A converter to output an analog signal with a maximum value when the instruction value is equal to an upper limit value of the first numerical range.
8. The image display system according to claim 5 , wherein
a digital signal with the fixed value is a digital signal allowing the first D/A converter to output an analog signal with a maximum value.
9. The image display system according to claim 5 , wherein
the adjusting unit is configured to provide, to the second D/A converter, a digital signal allowing the second D/A converter to output an analog signal with a value of zero, when the instruction value is equal to a lower limit value of the second numerical range.
10. The image display system according to claim 5 , wherein
the adjusting unit is configured to provide, to the second D/A converter, a digital signal allowing the second D/A converter to output an analog signal with a maximum value when the instruction value is equal to an upper limit value of the second numerical range.
11. The image display system according to claim 3 , wherein
resolution of the first D/A converter is lower than resolution of the second D/A converter.
12. The image display system according to claim 1 , wherein
the shaping circuit includes a current source for supplying an offset current for the drive current.
13. The image display system according to claim 12 , wherein
the arithmetic unit is configured to generate the drive current by adding the offset current to the computation result of the analog signals outputted from the plurality of D/A converters.
14. The image display system according to claim 1 , wherein
the light source includes a laser.
15. The image display system according to claim 1 , further comprising a scanning unit configured to perform scanning with light from the light source,
wherein the processing unit is configured to control the scanning unit based on the image signal to form the image.
16. The image display system according to claim 1 , wherein
the adjusting unit is configured to determine the values of the digital signals inputted into the plurality of D/A converters of the shaping circuit in accordance with the instruction value so that a relation between change in the luminance and change in the instruction value comes close to a linear relationship.
17. The image display system according to claim 1 , wherein:
the luminaire includes a plurality of the light sources emitting light with mutually different wavelengths; and
the driving unit includes the shaping circuit for at least one of the plurality of light sources.
18. The image display system according to claim 1 , wherein
the computation result is a sum of or a difference between the analog signals outputted from the plurality of D/A converters.
19. A movable object comprising:
the image display system according to claim 1 ; and
a body where the image display system is installed.
20. An image display method for forming an image by use of light from a light source of a luminaire, the method comprising:
receiving an image signal indicative of an instruction value of luminance of the light source;
determining values of digital signals inputted into a plurality of D/A converters in accordance with the instruction value; and
outputting the drive current to the light source based on a computation result of analog signals outputted from the plurality of D/A converters.