We suggest a Time-of-Flight (TOF) video camera capturing real-time depth images (a.k.a depth map), which are generated from the fast-modulated IR images utilizing a novel MOEMS modulator having switching speed of 20 MHz. In general, 3 or 4 independent IR (e.g. 850nm) images are required to generate a single frame of depth image. Captured video image of a moving object frequently shows motion drag between sequentially captured IR images, which results in so called ‘motion blur’ problem even when the frame rate of depth image is fast (e.g. 30 to 60 Hz). We propose a novel ‘single shot’ TOF 3D camera architecture generating a single depth image out of synchronized captured IR images. The imaging system constitutes of 2x2 imaging lens array, MOEMS optical shutters (modulator) placed on each lens aperture and a standard CMOS image sensor. The IR light reflected from object is modulated by optical shutters on the apertures of 2x2 lens array and then transmitted images are captured on the image sensor resulting in 2x2 sub-IR images. As a result, the depth image is generated with those simultaneously captured 4 independent sub-IR images, hence the motion blur problem is canceled. The resulting performance is very useful in the applications of 3D camera to a human-machine interaction device such as user interface of TV, monitor, or hand held devices and motion capturing of human body. In addition, we show that the presented 3D camera can be modified to capture color together with depth image simultaneously on ‘single shot’ frame rate.
20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system
prototype are presented. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of
20MHz high-speed micro-optical image modulator, so called 'optical shutter'. The high speed image modulation is
obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical
resonance cavity which maximizes the magnitude of optical modulation. The optical shutter device is specially designed
and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is
positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the
object to capture a depth image. Suggested novel optical shutter device enables capturing of a full HD depth image with
depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been
limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture
14Mp color and full HD depth images, simultaneously. The resulting high definition color/depth image and its capturing
device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields
of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical shutter
design, fabrication, characterization, 3D camera system prototype and image test results.