Operation of CR-Series Cameras

The CR-series devices offer on-board computation. Therefore there are some fundamental differences in the underlying hardware and software concepts compared to other devices. In general CR-series cameras are operated in the same way as all other Ensenso devices, but some differences in usage exist which are listed and explained in this topic.

Note

The device specific procedures for operating the stereo camera are the same as for XR-series cameras, operation of the separate color sensor corresponds to the operation of the color sensor in C-series cameras.

Software Concept

Commands

The main difference during operation is that the execution of cmdComputeDisparityMap will internally be executed on the camera’s FPGA accelerator. This offloading is performed within EnsensoSDK and the user does not need to take care of this. The computed disparity map will be sent to the host PC where most post processing filters are being executed. The reprojection of points in cmdComputePointMap is also done on the host PC to save transfer time.

Image Acquisition

CR cameras perform undistortion and rectification of images on the fly while receiving the image data, therefore during normal depth measurement operation only rectified images are available from the camera. In order to collect calibration patterns for pose estimation or camera calibration the rectification module needs to be disabled by setting the capture mode parameter Mode to “Raw”. This disables on the fly rectification and writes raw images into the camera’s Raw image nodes. The Rectified image nodes will not be updated in “Raw” mode and therefore the camera cannot perform depth measurement until you switch back to “Rectified” capture mode.

Image Transfer Times

Transferring the acquired images to the host PC can take a considerable amount of time. Therefore you can control the image transfer of acquired image data via the ImageDownloadLimit parameter. If you do not need image data you can entirely disable image download, alternatively you can download the first image for visualization.

Functional Limitations

  • Only PatchMatch2 stereo matching Method is supported.

Limitations of Patch Match 2

Separate Color Sensor

CR-series cameras contain a color sensor in addition to the stereo camera. In the NxLib, this color sensor is represented as a separate mono camera. It behaves like a separate color sensor which is calibrated to the stereo camera. The data of the two cameras can be combined as explained in this guide.

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Interaction Between Stereo and Color Devices

The two devices can be operated mostly independently from each other, though there are some operations that affect both of them and require special handling.

IP Configuration

Stereo and color camera share the same IP configuration. It can be changed through either device, but the change will apply to both of them at once.

Note

If the device is not configured correctly yet, discovery of the color sensor is not possible. Only the left sensor of the stereo camera is visible in this case. Configure the IP of this device in order to make the color sensor show up as well.

Firmware Updates

Firmware updates can only be installed on the stereo camera.

Device-Internal Trigger

Stereo and color camera can be triggered independently from each other. To synchronize them, set the color sensor to the special TriggerMode Internal in order to trigger it automatically when the stereo camera gets triggered.

In this mode, sensors are triggered as close together as possible while still respecting the different light settings.

  • When the stereo camera triggers multiple FlexView frames, only one frame gets triggered for the color sensor.

  • When the requested lighting is the same (stereo Projector is disabled and both stereo and color sensor have identical FrontLight settings), the color sensor gets triggered at the same time as the first stereo camera frame. Otherwise the color sensor gets triggered immediately after all of the stereo sensor’s FlexView frames were captured.

  • When the stereo camera has its Projector enabled, the color sensor gets triggered separately, using its own FrontLight parameters instead.

Factory Calibration

The raw factory calibration as well as the corresponding pattern observations are stored directly on the device. See the Restore Factory Calibration guide for more details.