feat(camera): add manual exposure, gain, and white balance options for RealSense cameras

The RealSense camera integration lacked sensor-level controls, causing
issues like unstable lighting from auto-exposure hunting. This adds
optional `exposure`, `gain`, and `white_balance` fields to
RealSenseCameraConfig that disable the corresponding auto modes and
apply fixed values when set.

src/lerobot/cameras/realsense/camera_realsense.py

@@ -191,6 +191,7 @@ class RealSenseCamera(Camera):
             ) from e
 
         self._configure_capture_settings()
+        self._configure_sensor_options()
         self._start_read_thread()
 
         # NOTE(Steven/Caroline): Enforcing at least one second of warmup as RS cameras need a bit of time before the first read. If we don't wait, the first read from the warmup will raise.
@@ -339,6 +340,59 @@ class RealSenseCamera(Camera):
         self.new_frame_event.clear()
         return self._async_read(timeout_ms=10000, read_depth=read_depth)
 
+    def _get_color_sensor(self) -> "rs.sensor":
+        """Returns the color sensor from the active pipeline profile."""
+        if self.rs_profile is None:
+            raise RuntimeError(f"{self}: rs_profile must be initialized before use.")
+
+        device = self.rs_profile.get_device()
+        for sensor in device.query_sensors():
+            if sensor.get_info(rs.camera_info.name) == "RGB Camera":
+                return sensor
+        raise RuntimeError(f"{self}: no RGB Camera sensor found on device.")
+
+    def _configure_sensor_options(self) -> None:
+        """Applies manual sensor options (exposure, gain, white balance) to the color sensor.
+
+        When exposure or gain is set, auto-exposure is disabled first. When white_balance
+        is set, auto white balance is disabled first. Skipped entirely if no options are set.
+        """
+        config = self.config
+        if config.exposure is None and config.gain is None and config.white_balance is None:
+            return
+
+        color_sensor = self._get_color_sensor()
+
+        if (config.exposure is not None or config.gain is not None) and color_sensor.supports(
+            rs.option.enable_auto_exposure
+        ):
+            color_sensor.set_option(rs.option.enable_auto_exposure, 0)
+            logger.info(f"{self} auto-exposure disabled.")
+
+        if config.exposure is not None:
+            if color_sensor.supports(rs.option.exposure):
+                color_sensor.set_option(rs.option.exposure, config.exposure)
+                logger.info(f"{self} exposure set to {config.exposure}.")
+            else:
+                logger.warning(f"{self} sensor does not support manual exposure.")
+
+        if config.gain is not None:
+            if color_sensor.supports(rs.option.gain):
+                color_sensor.set_option(rs.option.gain, config.gain)
+                logger.info(f"{self} gain set to {config.gain}.")
+            else:
+                logger.warning(f"{self} sensor does not support manual gain.")
+
+        if config.white_balance is not None:
+            if color_sensor.supports(rs.option.enable_auto_white_balance):
+                color_sensor.set_option(rs.option.enable_auto_white_balance, 0)
+                logger.info(f"{self} auto white balance disabled.")
+            if color_sensor.supports(rs.option.white_balance):
+                color_sensor.set_option(rs.option.white_balance, config.white_balance)
+                logger.info(f"{self} white balance set to {config.white_balance}.")
+            else:
+                logger.warning(f"{self} sensor does not support manual white balance.")
+
     @check_if_not_connected
     def read_depth(self, timeout_ms: int = 200) -> NDArray[Any]:
         """

src/lerobot/cameras/realsense/configuration_realsense.py

@@ -46,6 +46,15 @@ class RealSenseCameraConfig(CameraConfig):
         use_depth: Whether to enable depth stream. Defaults to False.
         rotation: Image rotation setting (0°, 90°, 180°, or 270°). Defaults to no rotation.
         warmup_s: Time reading frames before returning from connect (in seconds)
+        exposure: Manual exposure value for the color sensor. When set, auto-exposure is
+            disabled and this fixed value is used. Valid range depends on the camera model
+            (e.g., 1-10000 for D400 series). Defaults to None (auto-exposure).
+        gain: Manual gain value for the color sensor. When set, auto-exposure is disabled
+            and this fixed gain is used. Valid range depends on the camera model
+            (e.g., 16-248 for D400 series). Defaults to None (auto).
+        white_balance: Manual white balance value for the color sensor. When set, auto
+            white balance is disabled and this fixed value is used. Valid range depends on
+            the camera model (e.g., 2800-6500 for D400 series). Defaults to None (auto).
 
     Note:
         - Either name or serial_number must be specified.
@@ -61,6 +70,9 @@ class RealSenseCameraConfig(CameraConfig):
     use_depth: bool = False
     rotation: Cv2Rotation = Cv2Rotation.NO_ROTATION
     warmup_s: int = 1
+    exposure: int | None = None
+    gain: int | None = None
+    white_balance: int | None = None
 
     def __post_init__(self) -> None:
         self.color_mode = ColorMode(self.color_mode)