Chromatic aberration

Cataract removal is one of the safest and most common types of surgery performed today. Advanced lens implant technology can dramatically improve the visual quality and resulting quality of life for those with cataracts.

IntroductionThorlabs has a series of quality control procedures in order to ensure our singlets meet our standards and specifications. This starts with in-process inspections of the lens’ imaging capabilities and ends with a final inspection of surface quality and dimensions. Specifications for particular products can be found in their linked documentation by clicking the  symbol. This tab will take you through the general process used to check for quality.Singlet Quality PracticesIn-process inspection begins once the singlet has been shaped to specifications. Focal length, surface irregularity, and surface power are checked, following sampling plan Level VI given in MIL-PRF-13830B (see below). These three specifications are imperative for proper imaging. Surface irregularity of parts is kept to below either a quarter wavelength or a half wavelength at 633 nm, depending on the material of the singlet. Below is a graph of over 200 batches of singlets with irregularity data of both their front and back sides.At this point, some uncoated singlets will proceed to final inspection, while others will receive an antireflective (AR) coating. The application of optical coatings has its own in-process inspections. To ensure the AR coating is applied properly, we verify both reflectance and transmission performance by scanning witness pieces using spectrophotometry; the material of these 2 mm thick witness samples matches the other parts in the run. For reflectance verification, we use at least one witness sample for each coating run. Transmitting optics receive two AR coatings, one on each surface, so for the verification of transmission, we use one witness sample that is also coated on both of its sides. Large runs use multiple witness samples to ensure the uniformity across the deposition chamber. By testing coating performance during every run, variance over time is kept low. To see how coatings vary, see the table below.Final inspection of both uncoated and AR-coated singlets includes a batch check of diameter and thickness and a 100% visual check to ensure that the surface quality, chamfer, and clear aperture meet our published specifications. While surface quality is cosmetic to a degree, scratches, digs, and other inclusions in the surface of a part can increase the chances of damage to the singlet when used with high-power sources. These inspections are done in a clean, dark room under lighting that meets the requirements of MIL-PRF-13830B. Inspection under a single light source in a dark room allows for inconsistencies in the glass to be located without being obscured by glare or reflections.MIL-PRF-13830B: Performance Specifications for Optical ComponentsMIL-PRF-13830B is a document created by the U.S. Army Armament Research, Development and Engineering Center's Defense Quality and Standardization Office for the specifications covering how finished optical components should be manufactured, assembled, and inspected. While primarily for use in letting the military dictate how products they use can be incorporated into their equipment, these standards have been adopted by many optics manufacturers. To download a copy of the full document, click here.

Perspectivedistortion

Click on the image to download the raw data. In the thick lens equation, use the index of refraction for N-BK7 at the wavelength of interest to approximate the wavelength-dependent focal length of any of the plano-convex lenses.

Lensdistortioncorrection

N-BK7 is probably the most common optical glass used for high-quality optical components. It is typically chosen whenever the additional benefits of UV fused silica (i.e., good transmission further into the UV and a lower coefficient of thermal expansion) are not necessary.

Extra-thick retaining rings offer several features that aid in mounting high-curvature optics such as aspheric lenses, short-focal-length plano-convex lenses, and condenser lenses. As shown in the animation to the right, the guide flange of the spanner wrench will collide with the surface of high-curvature lenses when using a standard retaining ring, potentially scratching the optic. This contact also creates a gap between the spanner wrench and retaining ring, preventing the ring from tightening correctly. Extra-thick retaining rings provide the necessary clearance for the spanner wrench to secure the lens without coming into contact with the optic surface.

For bi-convex lenses, where the front and back radii of curvature are equal in magnitude and opposite in sign, R1 = -R2 = R, we have

Lendistortion

Sphericalaberration

The focal length of a thick spherical lens can be calculated using the thick lens equation below. In this expression, nl  is the index of refraction of the lens, R1 and R2 are the radii of curvature for surfaces 1 and 2, respectively, and d is the center thickness of the lens.

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Thorlabs' retaining rings are used to secure unmounted optics within lens tubes or optic mounts. These rings are secured in position using a compatible spanner wrench. For flat or low-curvature optics, standard retaining rings manufactured from anodized aluminum are available from Ø5 mm to Ø4". For high-curvature optics, extra-thick retaining rings are available in Ø1/2", Ø1", and Ø2" sizes.

After treating nearsightedness and astigmatism with the Wavelight laser, night vision clarity after treatment is actually better on average than before treatment. LASIK technology, combined with our surgical expertise makes it possible to correct a very wide range of optical imperfections.

We use the Zeiss VisuMax laser to create the delicate LASIK flap, and then our Wavelight laser to perform the optical sculpting for vision correction.  Using the Wavelight laser, our surgeons have an outstanding track record. Our results show that over 98% of patients achieve 20/20 vision, and about 30% achieve even sharper vision (20/15 or better).

Thorlabs' uncoated N-BK7 Bi-Convex Lenses are popular for many finite imaging applications. This type of lens is best suited for use in situations where the object and image are on opposite sides of the lens and the ratio of the image and object distances (conjugate ratio) is between 0.2 and 5. These lenses are designed to have a focal length of f= (R1*R2)/((n-1)*(R2-R1)).

The focal length of the lens calculated using the simplified thick lens equation directly above is the distance between the second (back) principle plane (H") and the position at which a collimated beam incident on the curved surface of the bi-convex is focused. The same analysis can be performed using a point source and the first (front) principle plane (H'). The principle plane positions of a thick lens can be calculated with the following equations:

With our custom-tailored approach, it is possible to enjoy glasses-free vision for near, and far, and in-between. Dr. Moarefi, Dr. Wallace and the team at LA Sight are able to offer the widest range of custom treatment options available with cataract and clear lens surgery.

Radialdistortion

New Lifestyle Intraocular Lenses (IOLs) can correct nearsightedness, farsightedness,  and astigmatism; affording the ability to see well at distance after treatment, without glasses. Other special multifocal lenses allow focus at a fuller range of vision, reducing or eliminating the need for glasses at any distance.  We personalize our recommendations to you based on your lifestyle, visual desires, habits, and preferences during a comprehensive evaluation.

In September, 2016, the Zeiss VisuMax laser received FDA approval for a new form of laser treatment, called “SMall Incision Lenticule Extraction” or SMILE.   This technique allows the Zeiss VisuMax laser to etch both front and rear surfaces of a tiny lens-shaped bit of tissue (lenticule) from the collagen layer of the cornea, which can then be removed through a very tiny incision.  There may be distinct advantages to SMILE in certain situations when compared to LASIK.  We will be happy to explain the differences and provide additional information to you during your consultation.

We don’t think you should have to make any compromises when it comes to your vision. LA Sight in Los Angeles is world class LASIK center specializing in LASIK, PRK and SMILE laser vision correction and advanced cataract surgery. We focus on providing unsurpassed vision care for very reasonable cost.

Simply stated, we put patients first. We strive to educate, inform, demonstrate, and discuss your options.  Properly done, vision correction surgery is a terrific option for those who are interested and are determined to be good candidates for care.

Coma aberration

Our high-performance multilayer AR coatings have an average reflectance of less than 0.5% (per surface) across the specified wavelength ranges and provide good performance for angles of incidence (AOI) between 0° and 30° (0.5 NA). For optics intended to be used at large incident angles, consider using a custom coating optimized at a 45° angle of incidence; this custom coating is effective from 25° to 52°. The plot shown below indicates the performance of the standard coatings in this family as a function of wavelength. Broadband coatings have a typical absorption of 0.25%, which is not shown in the reflectivity plots.

Although this page features our uncoated bi-convex lenses, these lenses are also available with one of four antireflection coatings (-A, -AB, -B, or -C) deposited on both sides to reduce the amount of light reflected from each surface. Links to each of these pages can be found in the table to the right. Please see the Graphs tab for coating details.

Disclaimer: The coated transmission data presented here are of 2 mm thick witness samples of N-BK7 or equivalent glass, and all the data here are typical. Some variations in performance data will occur from lot to lot. Please contact Technical Support with any questions regarding the use or reliability of these data.

LA Sight was founded by Dr. David Wallace, one of the country’s foremost vision correction specialists. Our surgeons, Dr. Moarefi and Dr. Wallace, use the most advanced laser technology and provide custom treatment to ensure each patient obtains their best possible vision.

What is the first thing we hear after a LASIK procedure?  “I wish I’d done it sooner!” It is true. Our patients are always surprised by how quick, easy and painless LASIK is. In fact, most patients can see clearly within hours of treatment and the vast majority  return to their activities the very next day.

Below is the transmission curve for N-BK7, a RoHS-compliant form of BK7. Total Transmission is shown for a 10 mm thick, uncoated sample and includes surface reflections. Each N-BK7 bi-convex lenses can be ordered uncoated (available below) or with one of the following broadband AR coatings: 350 - 700 nm (designated with -A), 400 - 1100 nm (designated as -AB), 650 - 1050 nm (designated as -B), or 1050 - 1700 nm (designated as -C).