Pancakelensesvs fresnelreddit

Flournoy, Blake. How To Calculate The Field Of View In A Microscope last modified March 24, 2022. https://www.sciencing.com/calculate-field-microscope-7603588/

But if we have already 2,000 nits displays in smartphones, why are VR headsets running at only 100 nits? The answer lies in the type of lens used and the need for low-persistence displays in VR.

The percentage of ON time of the display, also referred to as persistence, is typically set to around 10%. In contrast to a direct view display, which is always ON, the VR display will flicker very quickly and only emit light 10% of the time.

Flournoy, Blake. "How To Calculate The Field Of View In A Microscope" sciencing.com, https://www.sciencing.com/calculate-field-microscope-7603588/. 13 April 2018.

LED LCDs in combination with pancake lenses are the next best alternative, but they suffer from similar issues. While LEDs are very efficient and can deliver millions of nits on their own, when put in a VR headset they are backlighting an LCD panel (~2–3% transmission) in combination with a pancake lens (10% transmission) and run at 10% persistence. There is a reason for the fans behind the Meta Quest Pro display modules!

Low persistence mode helps to reduce motion blur and ghosting by briefly flashing the image on the screen for a short period of time, usually only a few milliseconds. This reduces the amount of time that the image is displayed on the screen and allows for smoother, clearer motion tracking.

“Probably the hardest challenge in terms of the display and getting it to be super vivid, [is] the [HDR] problem. TVs have gotten a bit better on HDR recently. But the vividness … of screens that we have compared to what your eye sees in the real world [is] just an order of magnitude or more off.”

Asphericvs pancakelenses

Fresnel lenses have been widely used in the first generation of headsets as they are commercially available and have high optical transmission. Unfortunately, they produce image artifacts (“God rays”) and cannot deliver the ultra-short focal distances required for compact headsets. Additionally, the contrast obtained in headsets using Fresnel lenses is typically much lower than the native panel contrast.

Quest 3pancakelenses

Unlike normal displays used in smartphones, laptops, or TVs, a VR display will be looked at with a lens. A lens is necessary for a VR headset to help focus and magnify the images displayed on the screen. In a typical VR headset, the screen is placed very close to the eyes, which makes it difficult for the eyes to focus on the images without magnification.

Valve Indexpancakelenses

Using OLEDoS with pancake lenses makes it extremely challenging to deliver a bright image. Current panels deliver ~1,800 nits at full power, which results in roughly 18 nits at the eye after being transmitted through a pancake lens system and running at 10% persistence. The result is a very dark image. Of course, technology will improve and eMagin has showcased a 10,000 nits display (with 20,000 nits in the pipeline), but even that will bring the brightness delivered to the eye to just 200 nits, about a factor 100x short of the 20,000 nits required for good immersion. It is hard to believe that OLED displays will be able to deliver the brightness required for true HDR in a VR headset, in particular, when the heat load is considered.

Several types of lenses are available to do this job: refractive, Fresnel, pancake, folded holographic, and transmissive holographic lenses. Since we need a large lens with a short focal length, we already know that a refractive lens will not work.

Compound light microscopes are valuable tools in the lab. They magnify our ability to see in detail by up to 1,000 times, allowing us to study things as small as the nucleus of a cell. With them, we can determine the shape and structure of cells, observe the movements of microorganisms, and examine the smallest parts of plants, animals and fungi. Because the objects under a microscope's view are so small, it is often impossible to use a ruler to determine their size. However, calculating a microscope's field of view (FOV), the size of the area visible through the microscope, allows you to determine the approximate size of a specimen under examination.

Fresnellenses

Following the discussion above, it becomes clear that VR headset engineers are facing a formidable challenge: delivering 10,000 nits to the eye while using a display that is only ON 10% of the time and potentially using a lens system that will transmit only 10% of the light (in the case of pancake lenses).

Brightness and contrast are crucial for good image quality but are an often misunderstood topic in VR. Naively, one would expect that in a closed VR headset low display brightness would be sufficient as there is no external light to compete with. For example, a current VR headset like Meta Quest 2 delivers only 100 nits to the eye, compared to ~2,000 nits of the latest iPhone generation, and is widely used by millions of people.

Fresnel lens vs pancake lenscost

If you want to get in touch and learn more about VitreaLab’s laser backlighting technology, contact us at office@vitrealab.com.

Whenever you change microscopes or switch eyepieces or objective lenses, remember to repeat the FOV calculations with the new field number and magnifications. When dealing with objects observed at higher magnifications, it may be useful to convert your measurements from millimeters to micrometers. To do so, multiply the FOV diameter in millimeters by 1,000 to convert the diameter to micrometers.

Knowing a compound light microscope's field of view (FOV) allows you to determine the approximate size of objects too small to measure with a standard ruler. To calculate field of view, you need to know the magnification and field number of the microscope's lens currently in use. Divide the field number by the magnification number to determine the diameter of your microscope's field of view.

Pancake lensVR

When the user moves his head quickly in VR, the image displayed on the headset’s screen can become blurry or smeared, making it difficult for the brain to process the visual information accurately. These effects can lead to motion sickness symptoms such as nausea, dizziness, and headaches.

Holographic lenses are manufactured using laser interference, hence their name (no relation to holographic displays). Holographic lenses use diffraction to control light, which is a very powerful approach, with the limitation that it only works with coherent laser light. This is because the diffractive structures used in the lens are wavelength dependent, and the wide spectrum of, e.g., an OLED display leads to image artifacts. Holographic lenses combine excellent image quality with high transmission and a short focal length, making them the ideal candidate for VR headsets. Folded holographic lenses have been pioneered by JDI and Meta and enable extremely short focal lengths but suffer from a low transmission. Transmissive holographic lenses are more difficult to manufacture but enable very high optical efficiency and image quality.

To determine the FOV of your microscope, first examine the microscope itself. The microscope's eyepiece should be labeled with a sequence of numbers, such as 10x/22 or 30x/18. These numbers are the eyepiece magnification and the field number, respectively. Also, take note of the magnification of your objective lens at the bottom of the microscope, if applicable – generally 4, 10, 40 or 100 times.

Fresnel lens vs pancake lensvr headset

While 100 nits are “bright enough” to see an image, it falls far short of delivering the immersive experience we seek when using a VR headset. If a lamp in real life outputs 10,000 nits, but the headset can only render it at 1/100th of that brightness, then the world will look “flat” and unrealistic.

Flournoy, Blake. (2018, April 13). How To Calculate The Field Of View In A Microscope. sciencing.com. Retrieved from https://www.sciencing.com/calculate-field-microscope-7603588/

Pancake lenses use a folded optical path to achieve a short focal length and retain the optical quality of refractive optics. While the image quality that they produce is superior to Fresnel lenses, they introduce unwanted reflections and ghost images due to multiple optical surfaces in their design. In particular, for OLEDoS displays, which typically have a size of only ~1" diagonal, pancake lenses are the best option to achieve an acceptable FOV. One of the biggest drawbacks compared to Fresnel lenses is their low optical transmission at about 10% for unpolarized light and 20% for polarized light.

Once you've taken note of the eyepiece magnification, field number and objective lens magnification number, if applicable, you can calculate your microscope's field of view by dividing the field number by the magnification number. For example, if the microscope's eyepiece reads 30x/18, then 18 ÷ 30 = 0.6, or an FOV diameter of 0.6 millimeters. If your microscope only uses an eyepiece, this is all you need to do, but if your microscope uses both an eyepiece and an objective lens, multiply the eyepiece magnification by the objective magnification to find the total magnification before dividing the field number. For example, if the eyepiece reads 10x/18, and the magnification of your objective lens is 40, multiply 10 and 40 to get 400. Then divide 18 by 400 to get an FOV diameter of 0.045 millimeters.

Laser LCD and holographic lenses are the only good option to deliver HDR content. Using transmissive holographic lenses immediately increases brightness by a factor of ~10x without compromising image quality or FOV. Moreover, by using VitreaLab’s collimated laser backlighting technology, another large factor of improvement can be found: a display emitting light over 20° will appear 80x brighter than a display emitting light over 180° while emitting the same number of lumens! The benefits of collimation and holographic lenses increase the brightness 100x compared to OLEDoS.