docs: update log_file_name parameter description in launch parameters and FAQ documentation

docs/en/source/camera_devices/4_application_guide/launch_parameters.md

@@ -318,7 +318,7 @@ The following are the launch parameters available:
   * Shared SDK and ROS node log level. By default, only current device status is printed; set it to `debug` for more debug logs. Optional values: `none`, `debug`, `info`, `warn`, `error`, `fatal`.
   * SDK logs and crash files are saved to `~/.ros/Log` by default. ROS logs remain in `~/.ros/log`.
 * **`log_file_name`**
-  * Saved SDK log file name. Effective when `log_level` is `debug`; the actual path is usually `~/.ros/Log/<camera_name>/<log_file_name>`.
+  * SDK log file name. When empty, the log file is named after the node startup time in the format `OrbbecSDK_<YYYYMMDD_HHMMSS>.log`. When specified, the resulting path is `~/.ros/Log/<camera_name>/<log_file_name>`.
 * **`enable_firmware_log`**
   * Enable firmware logging. This switch is independent from `enable_heartbeat` and can be enabled only when firmware logs are needed.
 * **`diagnostic_period`**

docs/en/source/camera_devices/8_FAQ/FAQ.md

@@ -29,12 +29,12 @@ If the camera node crashes unexpectedly, it will generate a crash log under `~/.
 
 **1. SDK debug logs**
 
-Set the launch parameter `log_level` to `debug`. After running, the SDK will generate log files under `~/.ros/Log/<camera_name>/`. If you want a more recognizable file name for this test, you can set the parameter `log_file_name`.
+Set the launch parameter `log_level` to `debug`. After running, the SDK will generate log files under `~/.ros/Log/<camera_name>/`.
 
-- The actual SDK log file path is usually `~/.ros/Log/<camera_name>/<log_file_name>`.
+- When `log_file_name` is empty, the SDK log file is named after the node startup time in the format `OrbbecSDK_<YYYYMMDD_HHMMSS>.log`, for example `~/.ros/Log/camera/OrbbecSDK_20260713_143025.log`.
-- In multi-camera setups, SDK logs are separated by `camera_name`, for example `~/.ros/Log/camera_01/camera_01.log` and `~/.ros/Log/camera_02/camera_02.log`.
+- You can also use `log_file_name` to specify the file name; the resulting path is `~/.ros/Log/<camera_name>/<log_file_name>`. When a fixed file name is specified, multiple launches may continue writing to the same file.
-- SDK logs are appended to the same file: multiple launches will continue writing into the same log file.
+- In multi-camera setups, SDK logs are stored in separate directories by `camera_name`. The current `multi_camera.launch.py` and `multi_camera_synced.launch.py` explicitly use `camera_01.log` and `camera_02.log`.
-- Recommendation: before packaging logs to send to technical support, delete old log files, then reproduce the issue and collect new logs. This keeps the logs cleaner and makes troubleshooting more accurate.
+- When submitting an issue, provide the SDK log file that corresponds to the time when the issue occurred. If a fixed file name is used, delete or back up the old log before reproducing the issue.
 
 **2. ROS 2 logs (`~/.ros/log`)**
 

docs/zh/source/camera_devices/4_application_guide/launch_parameters.md

@@ -316,7 +316,7 @@
     *   SDK和ROS节点日志级别。默认只输出设备当前状态；需要更多调试信息时可设置为 `debug`。可选值：`none`、`debug`、`info`、`warn`、`error`、`fatal`。
     *   SDK日志和崩溃文件默认保存在 `~/.ros/Log`，ROS日志仍保存在 `~/.ros/log`。
 * **`log_file_name`**
-  * 保存的SDK日志文件名。当`log_level`为`debug`时生效；实际路径通常为 `~/.ros/Log/<camera_name>/<log_file_name>`。
+  * SDK 日志文件名。为空时，日志默认以节点启动时间命名，格式为 `OrbbecSDK_<YYYYMMDD_HHMMSS>.log`；指定后，实际路径为 `~/.ros/Log/<camera_name>/<log_file_name>`。
 *   **`enable_firmware_log`**
     *   启用固件日志。该开关与 `enable_heartbeat` 解耦，适合在需要抓取固件日志时单独开启。
 *   **`diagnostic_period`**

docs/zh/source/camera_devices/8_FAQ/FAQ.md

@@ -29,12 +29,12 @@
 
 **1. SDK debug 日志**
 
-将 launch 参数 `log_level` 设为 `debug` 运行后，会在 `~/.ros/Log/<camera_name>/` 目录下生成 SDK 日志文件。如果需要为本次测试指定一个更易识别的日志文件名，可以修改参数 `log_file_name`。
+将 launch 参数 `log_level` 设为 `debug` 运行后，会在 `~/.ros/Log/<camera_name>/` 目录下生成 SDK 日志文件。
 
-- `log_file_name` 对应的实际文件路径通常为 `~/.ros/Log/<camera_name>/<log_file_name>`。
+- `log_file_name` 为空时，SDK 日志默认以节点启动时间命名，格式为 `OrbbecSDK_<YYYYMMDD_HHMMSS>.log`，例如 `~/.ros/Log/camera/OrbbecSDK_20260713_143025.log`。
-- 多相机场景下，SDK 日志按 `camera_name` 分目录保存，例如 `~/.ros/Log/camera_01/camera_01.log`、`~/.ros/Log/camera_02/camera_02.log`。
+- 也可以通过 `log_file_name` 指定文件名，实际路径为 `~/.ros/Log/<camera_name>/<log_file_name>`。显式指定固定文件名后，多次启动可能继续写入同一个文件。
-- SDK 日志是追加写入的：多次启动会在同一个文件里不断累积日志。
+- 多相机场景下，SDK 日志按 `camera_name` 分目录保存。当前 `multi_camera.launch.py` 和 `multi_camera_synced.launch.py` 会分别指定 `camera_01.log`、`camera_02.log`。
-- 建议：在准备打包日志发给技术支持前，先删除旧的日志文件，然后重新复现问题并采集新的日志，这样日志更干净、定位更准确。
+- 提交问题时，请根据问题发生时间提供对应的 SDK 日志文件；如果使用固定文件名，建议先删除或备份旧日志，再重新复现问题。
 
 **2. ROS2 日志（~/.ros/log）**