Image display system, movable object, image display method, and non-transitory computer-readable medium

1. An image display system, comprising:

a light source driver that

supplies, to a light source, a drive current including a first current which changes in accordance with a gradation value indicated by an image signal and a second current which does not change in accordance with the gradation value, and

generates the first current based on a set value of the first current;

a processor that generates the set value of the first current in accordance with the image signal and output the set value of the first current generated to the light source driver;

a corrector that performs a correction process on the first current generated based on the set value of the first current generated in the processor to correct the drive current; and

a temperature sensor that detects an ambient temperature of the light source at each correction process,

wherein

the processor further

sets the set value of the first current to a current value proportional to the gradation value when the gradation value of the image signal is within a first gradation range, and

sets, based on a correspondence relationship between the gradation value and the current value of the first current, the set value of the first current to a current value determined with reference to the correspondence relationship when the gradation value is in a second gradation range in which numerical values are smaller than numerical values in the first gradation range,

the correction process includes a process of correcting the correspondence relationship such that a difference between a measured intensity and a target intensity of a light beam from the light source falls within a prescribed range, and

the corrector further

determines whether or not to correct the second current in the correction process based on the ambient temperature of the light source detected during a current correction process in comparison with a previous ambient temperature of the light source detected during a previous correction process, and

executes the correction process of the second current in the correction process when the ambient temperature of the light source detected during the current correction process is changed by at least a predetermined amount from the previous ambient temperature of the light source detected during the previous correction process.

2. The image display system of claim 1 , wherein

the second current is set to a current value smaller than or equal to a threshold current value at which the light source starts emitting the light beam.

3. The image display system of claim 1 , wherein

the corrector, when the current value corresponding to the gradation value in the corresponding relationship is defined as the set value of the first current,

obtains correction coefficient for matching a change rate of the measured intensity of the light beam from the light source with respect to the drive current to a change rate of the target intensity with respect to the drive current, and

corrects the correspondence relationship based on the correction coefficient.

4. The image display system of claim 1 , wherein

the light source driver generates the second current based on the set value of the second current, and

the correction process includes a process of correcting the set value of the second current.

5. The image display system of claim 1 , wherein

the correspondence relationship includes a plurality of the gradation values,

the second gradation range includes a defined range on a low-gradation side and a remaining range on a high-gradation side, and

an interval between each two of the plurality of gradation values is smaller in the defined range on the low-gradation side than in the remaining range on the high-gradation side.

6. The image display system of claim 1 , wherein

the light source driver includes

a first current source that generates the first current,

a second current source that generates the second current, and

an adder that adds the first current to the second current to generate the drive current.

7. The image display system of claim 1 , wherein

the light source includes a plurality of the light sources that output light beams of colors different from each other,

the light source driver supplies each of a plurality of the drive currents to a corresponding one of the plurality of light sources,

the processor includes a plurality of the correspondence relationships each corresponding to an associated one of the plurality of drive currents, and

the corrector performs the correction process on each of the plurality of drive currents.

8. The image display system of claim 7 , wherein

the corrector executes the correction process on each of the plurality of drive currents to adjust white balance of a light beam including light beams output from the plurality of light sources.

9. A movable object, comprising:

the image display system of claim 1 ; and

a movable object body on which the image display system is mounted.

10. An image display method, comprising:

a light source driving process of supplying, to a light source, a drive current including a first current which changes in accordance with a gradation value indicated by an image signal and a second current which does not change in accordance with the gradation value to generate a first current based on a set value of the first current;

an output process of generating the set value of the first current in accordance with the image signal and outputting the set value of the first current generated;

a correction process of performing a correction process on the first current generated based on the set value of the first current generated in the output process to correct the drive current; and

detecting, by a temperature sensor, an ambient temperature of the light source during each correction process,

wherein

the output process includes

setting the set value of the first current to a current value proportional to the gradation value when the gradation value of the image signal is within a first gradation range, and

setting, based on a correspondence relationship between the gradation value and the current value of the first current, the set value of the first current to a current value determined with reference to the correspondence relationship when the gradation value is in a second gradation range in which numerical values are smaller than numerical values in the first gradation range,

the correction process includes a process of correcting the correspondence relationship such that a difference between a measured intensity and a target intensity of a light beam from the light source falls within a prescribed range,

the correction process further includes

a process of determining whether or not to correct the second current based on the ambient temperature of the light source detected during a current correction process in comparison with a previous ambient temperature of the light source detected during a previous correction process, and

a process of correcting the second current when the ambient temperature of the light source detected during the current correction process is changed by at least a predetermined amount from the previous ambient temperature of the light source detected during the previous correction process.

11. A non-transitory computer-readable medium on which a program causes a computer system to execute the image display method of claim 10 is recorded.