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.

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.

Since the objective is closest to the specimen being examined, it will relay a real image to the ocular lens. While doing so, it contributes a base magnification of anywhere from 4x (for a scanning objective lens, typically used to provide an overview of a sample) to 100x (for oil immersion objectives).

A microscope is a special optical device designed to magnify the image of an object. Depending on the type of microscope, it may project the image either onto a human eye or onto a recording or video device. As an example, consider the photographs of cells that can be found in a science textbook. These photographs have all been taken by a specialized microscope, and may be called micrographs.

Many objectives are designed to be used with a cover glass. Using an incorrect coverslip thickness can greatly reduce the optical performance of a microscopy system.

Objective lenses can be classified based on the objective construction, field of use, microscopy method, performance (optical aberration corrections), and magnification. Many microscope objective manufacturers offer a wide range of objective designs, which provide various degrees of optical aberration corrections for supporting different needs. Mirrors or reflective elements are used in objective lenses for the applications that requires chromatic aberration over board spectral ranges. Most traditional microscopy systems use refractive objectives such as achromatic objectives (the cheaper objectives) for laboratory microscope applications and plan apochromats (expensive objectives) for biological and science research microscope applications.

For keeping the objective at the proper position, there are mounting threads on almost all objectives. Commonly used mounting threads include RMS, M25 x 0.75, M26X 0.706, M32 x 0.75.

Valve Indexpancake lenses

Field of View is the area of the object that can be imaged by a microscopy system. The size of the field of view is determined by the objective magnification or focal length of the tube lens for an infinite-corrected objective. In a camera system, the field of view of the objective is related to the sensor size.

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.

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.

where θ is the maximum 1/2 acceptance ray angle of the objective, and n is the index of refraction of the immersion medium. Figure 2 shows the ray angle θ of an infinity-corrected objective.

Pancake lenses vs fresnelvr headset

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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.

Pancake lenses vs fresnelcost

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.

While the simplest of microscopes is simply a magnifying glass with a single lens, compound microscopes used today are highly complex devices with a carefully designed series of lenses, filters, polarizers, beamsplitters, sensors, and perhaps even illumination sources. The exact combination of optical components used will depend on the application of the microscope; the wavelength of light with which it is intended to be used, and the resolution and magnification required in the final image.

Pancakelens VR

Each microscope objective is itself a complex assembly of lenses, and besides contributing to the magnification, it is the objective lens which determines the resolution power of the microscope. An objective lens can also provide optical aberration corrections.  A reflective objective, for instance, includes two mirrors within the assembly. These mirrors can focus laser light as well as provide chromatic corrections.

A simple magnifier (magnifying glass), works when the object to be examined is situated within focal length of the magnifier lens, enabling larger virtual image is produced. This type of magnifier is very limited in both resolution and magnification. A compound microscope, on the other hand, uses a relay lens system instead of the single lens, and since each lens component can contribute magnifying power, the result is greatly increased capability.

The ocular lens, or eyepiece, is also an optical assembly rather than a single lens, but it is typically more simple than the objective. Often it is composed of two lenses: a field lens and an eye lens. The design of the ocular lens determines the field of view of the microscope, as well as contributing to the total magnification of the system.

Two major lens components—the objective lens and the ocular lens, or eyepiece—work together to project the image of the specimen onto a sensor. This may be the human eye or a digital sensor, depending on the microscope setup.

Pancake lenses vs fresnelreddit

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.

Quest 2pancake lenses

Objectives are complex multi-element lenses. For any given application, careful consideration of the optical parameters and specifications is necessary. In many cases, custom-designed objective assemblies provide the best-fit solution for meeting all the requirements of a specialized application.  Custom parameters may include antireflection coatings, chromatic focus shift, working distance, image quality (MTF and spot size), lens mount, glass window thickness, and field of view, among others.

Microscope Objectives or Objective lenses are in many ways the heart of the microscope, and are typically mounted on a rotating nosepiece or turret to enable easy selection. Many microscopes will be equipped with a scanning objective (4x), a low power objective (10x), a high power objective (40x), and perhaps even an oil immersion objective lens.

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.

A microscope objective is an important component of a microscopy or imaging system for a range of science research, biological, industrial, and general lab applications.. An objective lens determines the basic performance of an optical microscope or imaging systems and is designed for various performance needs and applications. It is located closest to the object and is an important component in imaging an object onto the human eye or an image sensor.

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.

The optical aberration correction determines the optical performance of an objective lens and plays a central role in the image quality and measurement accuracy of imaging or microscopy systems. According to the degrees of the aberration corrections, objective lenses are generally classified into five basic types: Achromat, Plan Achromat, Plan Fluorite (Plan Semi-Apochromat), Plan Apochromat, and Super Apochromat.

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

The ocular lens, located at the top of a standard microscope and close to the sensor (receiving eye) receives the real image from the ocular lens, magnifies the image received and relays a virtual image to the sensor. While most eyepieces magnify 10x, there are some which provide no magnification and others which magnify as much as 30x. The magnification power of the microscope can be calculated by multiplying the magnification power of the eyepiece, or ocular lens, by the magnification power of the objective lens. For example, an objective lens with a magnification of 10x used in combination with a standard eyepiece (magnification 10x) would project an image of the specimen magnified 100x.

Asphericvs pancake lenses

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.

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.

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!

Most objectives are designed to image specimens with air as the medium between the objective and the cover glass. However, for achieving higher working numerical apertures, some objectives are designed to image the specimen through another medium such as special oil with a refractive index of 1.51.

“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.”

The parfocal length is the distance between the objective mounting plane and the specimen / object. This is another specification that can often vary by manufacturer.

Magnification is one important parameter. Magnification is usually denoted by an X next to a numeric value.  Objectives are available in a range of magnifications from 2X to 200X.

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.

Quest 3pancake lenses

Since indirect backlight illumination is generally more effective than direct illumination, most microscopes do not include an internal light source.  Instead, they rely on daylight or on background illumination such as a lightbulb. In brightfield illumination, also known as Koehler illumination, two convex lenses saturate the specimen with external light admitted from behind. These two lenses, the collector lens and condenser lens, work together to provide a bright, even, and constant light throughout the system: on the image plane as well as on the object plane.  This system of illumination is used in many compound microscopes, including student microscopes and those found in many research labs.

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.

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).

Important specifications are marked on the barrel of the objective, so students or researchers can easily identify the properties of an objective and determine the optical performance and working conditions for proper use. Figure 1 shows a diagram of an objective lens. A detailed discussion of the objection specifications is provided below.

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At Shanghai Optics, we design and manufacture custom objectives and imaging systems to support our customers’ needs in many industries, including medical, biomedical, machine version, scientific research, and metrology, etc. Taking the client’s budget and precision requirements into consideration, our experienced engineering team ensure that each design can be manufactured at a reasonable cost and the optical performance is being met based on fabrication, assembly, and alignment tolerance analysis.