Inroduction
When a patient orders a pair of glasses they first choose a set of frames that suits them. The patient must have a prescription must be written by an optometrist which states the needed lens power and pupil distance (PD). Lenses in the needed power are either ordered or taken from stock. These lenses come from the factory as uncut round blanks approximately four inches across. Edging is the process of cutting these optical lens blanks to fit frames, producing a pair of glasses.
Equipment
There are four pieces of equipment used in the lens edging process. A lensometer is used to check the power in the lens. The tracer is used to determine the dimensions and shape of the frame. The blocker is used to prepare the lens for handling by the edger. The edger cuts the lens to the dimensions specified by the tracer.
Lensometer (Source: Topcon)
Tracer (Source: National Optronics)
Blocker (Source:Topcon)
Edger (Source: National Optronics)
Process
Step 1 Checking the Lens
After receiving the lens blanks the lab technician first checks them visually for any scratches or imperfections that would be cause for rejection. Next using the lensometer the power of the lens is verified. The lens is rotated to the correct axis (lenses with astigmatism or bifocal correction only) and the optical center (point where the prescription is strongest in the lens) and horizontal axis are marked.
Step 2 Tracing the Frame or Pattern
After lens checking the technician must trace the frame. Tracing determines the needed dimensions of the finished lens. There are two methods of doing this, tracing the frame and tracing the lens. The technician determines which method will work best with a particular frame based on experience and the lab's equipment. In frame tracing the demo lenses or the patients old lenses are removed from the frame and the frame is placed face down in the tracer and held in place with specialized clips. In pattern tracing either a pattern of the needed lens shape, a demo lens, or the patients old lens is used. Using a double sided adhesive the pattern or lens is attached to a stand that will hold it in the tracer. The technician will enter relevant information into the tracer such as a job number, patient's name, or other identifying information and also specifies whether he will be tracing a frame or a pattern, and whether he is tracing the right or left side.
This is the distance from the lens to the camera sensor and is measured in millimeters. This distance helps to identify how much the lens can zoom towards an object in the frame without losing any detail. A short length leads to an image that comes in a wide-angle and captures more of the scene in your pictures. A long length creates a magnified image that comes with a field of view that is narrow. The focal lengths available with macro lenses can extend from 8-millimeters to around 400-millimeters.
The MATALBs ‘edge(… )’ function is used to detect edges in the input image with various options for an argument (e.g. ‘Sobel’, ‘Canny’, ‘Prewitt’, ‘zerocross’). An example of detected edges is shown in Fig 10.
The optical lenses of the eyes are used to focus light. The light that penetrates the lens is controlled by the iris, which constricts and dilates in response to varying light conditions. Controlling the amount of light that reaches the lens, and subsequently the photoreceptors in the pigmented retina, is not enough to adequately discern images in three dimensions. The lens is therefore responsible for adjusting to conditions based on how far away or near an object is that is being viewed. To view something relatively close, the lens is bent to form a more spherical shape by the ciliary body muscles. Likewise, to view further distanced objects, the lens must undergo accommodation
Whether you have plastic or glass, concave lenses or convex lenses they are produced in much of the same way. Years ago opticians relied on separate optical laboratories to produce eyeglass lenses. However today optical outlets receive lens “blanks” (blanks received from optical laboratories) which are plastic pieces already formed to fit exactly into the front of the lens. The stages are grinding, polishing, and shaping. Materials used are plastic or glass blanks, which are thick in size to eyeglass frames, though slightly larger. Thickness may vary depending upon the prescription. Other raw materials used to make eyeglass lenses are adhesive tape, a liquid with a lead alloy base, metal, and dyes and tints. Eyeglass lenses are designed in many shapes in order to match the eyeglass frame.
The word microscope is often used to define an instrument used for viewing small objects, such as bacteria, minerals, and cells that can’t be seen with the naked eye by magnifying them using a series of lenses. Microscopes vary from models and styles, but each consists of similar parts including lens, eyepiece, stage, adjustment knobs, light, nosepiece, and arm. The eyepiece allows an individual to look through it to view samples. Usually the magnification of an eyepiece 10x. The arm supports the tube which connects the eyepiece to the objective lenses and the base. The objectives are referred to as the different magnification lenses that are rotated on the nosepiece. Usually one will find three objective lenses on a microscope. They consist
Contact lenses are a thin lens placed on the surface of the eye. They are considered a
People usually buy high index eyeglasses because of their aesthetic appeal. They don't produce the bug eye or beady eye effect, and their thinness makes them compatible with a wide variety of stylish frames.
This is a representation of the eye's lens system. This eye has no eye condition, such as nearsightedness or farsightedness, and the lens is drawn in its relaxed position. The light rays are focused appropriately on the retina. The thickness of the cornea is 0.449 mm, the distance from the cornea to the lens is 2.
Glaucoma can occur in any age patient, therefore yearly screenings is necessary for all ages (Understanding and Living with Glaucoma , 2012). Patients who are at a higher risk for glaucoma include patients of African and Asian decent, patients over the age of 60 years, patients who are very myopic, or nearsighted, and patients who excessively use steroids (Understanding and Living with Glaucoma , 2012). There are two types of screenings for glaucoma (Understanding and Living with Glaucoma , 2012). They are tonometry and ophthalmoscopy (Understanding and Living with Glaucoma , 2012). In order to measure the intraocular pressure, IOP, the health care provider will use tonometry (Ignatavicius & Workman, 2013). Eye drops are used to numb the eye so that a tonometer can be used to measure the inner pressure within the eyen (Understanding and Living with Glaucoma , 2012). The normal range for patients with normal eye pressure ranges from 10-21 mm Hg (Ignatavicius & Workman, 2013). Patients with open-angle glaucoma have a pressure of 22 mm Hg, and with closed-angle the pressure reading is 30 mm Hg or higher (Ignatavicius & Workman, 2013). During ophthalmoscopy, eye drops are also used, but to dilate the pupil (Understanding and Living with Glaucoma , 2012). The health care provider can then examine the optic nerve for damage due to glaucoma (Understanding and Living with
Much like taking pictures on Earth, astronomers have to deal with many issues with distortion when it comes to taking images. The solution to this issue is a technology called adaptive optics (often referred to as AO), which was originally used to improve the performance of optical systems on ground based telescopes. [1] Adaptive optics are made up of mirrors, that can be reshaped that are controlled by computers. These mirrors fix the distortion caused by the turbulence of the Earth’s atmosphere. This makes the images that are obtained have a quality that is as good as those taken from space, with the best image so far being twice as sharp as an image from the Hubble Telescope taken in Chile by the Magellan-Clay telescope. [2] Adaptive optics have medical benefits as well as astronomical benefits and are used in retinal research and imaging. Adaptive optics gets rid of ocular aberrations, which are distortions in images of objects caused when rays of light do not obey the laws describing perfect optical system on the retina. However, the eye is far from a perfect optical system since it is not centred on its axis perfectly and it is not a fixed optical instrument. The eye has many natural adaptations that lessen the aberrations, so that they are not troublesome or noticeable for everyday vision. Adaptive optics have many positive interactions with economical and ethical factors because of the cheap building price compared to alternative options and the little concern with any harm the technology actually does. It is a beneficial piece of technology that has developed valuable uses outside of astronomy that can lead to more uses in the future.
To focus the camera, place the very edge of the aluminum frame guide to what you wish to photograph,
The principle behind the refractive telescopes is the use of two glass lenses (objective lens and eyepiece lens) to gather and bend parallel light rays in a certain way so that the image fits the size of the eye's pupil. Light rays is gather through the opening of the telescope called the aperture and passes through the objective lens and refracts onto a single point called the focal point. From there the light rays continue the same direction until it hits the eyepiece lens which also refract the light back into parallel rays. During the process, the image that enters our eyes is actually reverse of the original image and magnified because the size in which we preceive the image.
The microscope is made up of many parts. The ocular lenses which you use to look through, body tube which is the tube you look through using t...