VC-DIS Sensors and Lensless Cameras

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flyinglentris Contributing Member • Posts: 587
VC-DIS Sensors and Lensless Cameras

I didn't sleep last night as I had drank some Cherry Doctor Pepper. My head was swimming with thought and I had been thinking about posts that replied to the thread "CoC vs Higher Megapixel Res." Normally, when a person wakes, they often forget what they dreamed in REM. Not this time.

Last night generated a proposal for a very unique and new type of camera, a lensless camera based on a special type of digital image sensor.

Not possible? I think it is and I'm going to share how I envision it.

I would expect that if this idea catches wind, a working prototype camera could be made available for production in perhaps 5 to 20 years?

Today is July 16, 2019 and this is when the idea originated.

For those of you who are students looking for a thesis, pay attention.

NOTE: A Vectored Cell Digital Image Sensor (VC-DIS) is my term for what will be described below.

It may be stated that the quality of light is such that the more distant its source, the tinier its Field of View. The Hubble Space Telescope by way of example, produces sharp fine resolution images of very distant objects in space. It is this quality of light which a lensless camera must capitalize on. VC-DIS Sensor technology is the tool and means of doing so.

The lensless camera completely eliminates the lens, the aperture diaphragm, all the lens aberrations, focus and zoom rings and so forth. Yet the camera is able to alter field of view and exposure to acquire its images. Depth of Field is also a casualty. Lensless Cameras with VC-DIS Sensors maintain sharp focus from working distance out to infinity. DoF would have to be achieved by mathematical algorithm to artificially generate blur and within specific zones of the image.

As far as exposure goes, only sensor sensitivity is required and algorithmically, the mid-tone values are automatically identified and sensitivity is used to center exposure. Ideally, the VC-DIS Sensor would allow night vision shots and on up to what would otherwise be coined as snow blind conditions, achieving adequate detail. Exposure could be supplemented temporally with a shutter, but by preference, the sensor is always active calculating image resolution, FoV and exposure. It would require minimally, a translucent protective screen and an opaque cover when not in use.

VC-DIS Sensors allow a Field of View to be selectively acquired based upon the design of the sensor cells. It does not do this automatically and requires user input to instruct the sensor how to acquire the FoV.

Exposure and FoV are therefore the two main facets of the VC-DIS Sensor based Lensless Camera. And while you might think that such a camera might require some rather complex controls, it doesn't. A simple thumb dial can be used to zoom in or out to acquire wider or narrower FoV. A second Thumb Dial can be used to adjust exposure as an override on the automatic calculation. Of course there will be other controls, but these are similar to those found in current DSLRs.

But how can a flat substrate digital sensor selectively acquire images with varying FoVs? That is the crux of this proposal.

Let's dig in and uncover the details of this revelation.

From Paleontologists to Biologists, all known fauna that have visual systems, ie. eyes, have lenses. That's what they know. The trilobite has multifaceted eyes like an insect's and human beings have fluid filled eyes with lens and an iris for a diaphragm. But could there be a life form, past and extinct or extant and living, that has a different sort of visual system, a system that is lensless? If so, their sensory mechanism would be flexible. It would bend and reshape itself, warping to allow far away objects to be focused upon or nearby objects at a wider angle of view. It's that flexibility that is the key to VC-DIS Sensors. And yet, as a digital sensor as a rigid fixed flat substrate - how can that be?

First, evaluate a possible proof of concept. Take for example, a wide field of mathematically controlled sensors which can be tilted to achieve a algorithmically generated curved sensor, such that each sensor's individual images can be stitched. Curve tighter and achieve a smaller FoV to fill the sensor with subject matter in a narrower FoV. Curve looser and achieve a wider angle FoV. Run a test rig with a patterned card, moving it further away or closer, altering the composite sensor's FoV via mathematically controlling individual sensor tilt. See if it works.

I don't have the resources to build such an array and test it out. If anybody would like to volunteer, report back with your results.

But OK, let's assume it works (for now). Again, a fixed flat semiconductor substrate cannot be physically curved. The only solution is to design the sensor cells so that they can be varied in some way, algorithmically, to create a pseudo-curved surface to achieve wider or narrower FoV. That, my fellow DPR members, can be achieved. Yes.

Please note that zooming in or out to different FoVs is not to be considered magnification. In fact its not even zooming. It's just acquiring a wider or narrower FoV. Magnification is defined as a function of the lens, the exit pupil diameter divided by the entrance pupil diameter and this provides what is called a reproduction ratio. This new camera is lensless and there are no pupils to calculate magnification with. Zooming in and out is an illusion created by choosing different FoVs and filling the sensor with the image at that FoV. And yes, it generates the illusion of magnification.

To achieve pseudo-curvature in a digital sensor, I have visualized a special kind of sensor cell, a recessed main sensor cell, ringed by smaller sensor cells which control the angle of sampled light ray reception. The sensitivity of the main cell and only a part or sector of the encircling ring, the part opposite the direction which it should be physically angled to control and define the pseudo-curvature.

Mathematical algorithms control the sensitivity of the main cell and that portion of the ring cells necessary to steepen or shallow the angle of reception. Of course, things are steeper near the periphery of the sensor. At the center, ultimately, the sensitivity of the ring cells is equally distributed and produces no angled reception.

Again, I have no resources to build and test this out. It requires a team of scientists and engineers in semiconductor lithography to achieve. And I don't know how well it will work, but I present the concept here as an eye opener to demonstrate possibility.

Finally, since the lens is gone, so are lens aberrations. All that remains are natural light aberrations like polarized light and such. Except ... the system may have algorithm produced aberrations. In particular, the mathematical control over the sensor cells can produce periphery fading. This aberration can be overcome by making the sensor edges extend beyond the image size intended, sort of like what printers call bleed.

When it comes to applications, lensless cameras can be similar to other cameras, minus the lens, but would not allow DoF and filter attachment unless this is accommodated algorithmically. The Vectored Cell Digital Image Sensor can be used to beef up cell phone camera technology, for sure.

In closing, I would note that VC-DIS Sensors would require very high resolution. Test rigs and prototypes can be generated with less resolution to evaluate the concept, but production cameras would have to be built around high resolution VC-DIS Sensors.

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flyinglentris in LLOMA

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