Wikipedia says "The active stereo vision is a form of stereo vision which actively employs a light such as a laser or a structured light to simplify the stereo matching problem. The opposed term is passive stereo vision".
Stereoscopic refers to the fact that there are left and right IR imagers. To quote Wikipedia again it is, "a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision".
This message was posted on behalf of Intel Corporation
Thank you for your interest in the Intel RealSense Technology.
The Intel RealSense R200 module uses stereo vision to calculate depth. The stereo vision implementation consists of left infrared camera, right infrared camera, and an infrared laser projector. The left and right camera data is sent to the R200 ASIC. The ASIC calculates depth values for each pixel in the image. The infrared projector is used to enhance the ability of the system to calculate depth in scenes with low amounts of texture. Traditionally, scenes with low texture such as walls presented a challenge for stereo vision systems to calculate depth.
The Intel RealSense D435 uses left and right image capture same scene and send data to image processor. The image processor calculates depth values for each pixel by correlating the shift in points between the 2 images, and knowing the baseline between the cameras. The depth pixel values are then processed to generate a depth frame.
For more information regarding this matter, you can consult the datasheets available for both products:
D400 Series: https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/Intel-RealSense-D400-Series-Datasheet.pdf
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