With the ability to collimate light beams with high accuracy and high resolution, collimating lenses are an essential component of many systems for various applications including spectrometers, beam-expander systems, display measuring systems, laser illumination systems, optical fiber couplers, sensor testing systems, etc. Collimating lenses allow users to control the field of view, spatial resolution and light collection efficiency of their instruments or setups.

Laser collimatinglens

Room 609, 6/F, Global Gateway Tower, No.63 Wing Hong Street, Cheung Sha Wan, Kowloon, Hong Kong +852-54993705 info@shanghai-optics.com

The modulation transfer function (MTF) is an optical bench measurement used by engineers to evaluate the performance of a lens, or a lens system. In its most basic sense, the MTF is a way to describe the contrast sensitivity of a lens system. For the human eye, this could be though of as its “visual performance.”

East Valley Ophthalmology offers comprehensive eye exams and world-class eye surgery using state-of-the-art medical procedures designed to enhance your life through better vision.

The human eye can be thought of in the same way as any optical system, with two basic components: the cornea and the lens. The cornea is an optical structure with positive spherical aberration and the lens is an optical structure with negative spherical aberration. The lens, with its negative spherical aberration greatly reduces the effect of the positive spherical aberration of the cornea.

Collimatinglensvs focusinglens

When a sound is recorded, each component frequency gets recorded, but the process invariably changes the volume of each frequency. The playback is a mixture of tones that constitute the original sound, but usually at different volumes. This change in volume for a specific tone causes the recorded sound to differ from the original. Likewise, when an image is projected or recorded, the contrast is typically differs from the original object by small or large amounts.

If you’re looking for a more specific solution, we can also help you with custom collimating lens design and consulting. Please contact our sales team for additional information.

As stated above, the difference between the bending of paraxial rays and the marginal rays is the amount of either positive or negative spherical aberration. The human cornea has naturally occurring positive spherical aberration and the human lens as naturally occurring negative spherical aberration. The net result is that these two structures together produce an optical system with a very low amount of positive spherical aberration. But if an older style spherical intraocular lens is implanted (which has positive spherical aberration) this increases the total amount of spherical aberration and degrades the image quality at larger pupil sizes.

The typical production process for a collimating lens assembly involves manufacturing the lenses through molding or polishing, followed by inspecting, coating, assembling, and testing. Although the manufacturing process remains the same regardless of the collimating lens type, the application of the lens may influence the testing method and design details, such as glass material selection and coating design. Collimating lenses can be tailored to better suit customers’ specific needs.

How to collimatelight

Overall, improving the modulation transfer function of the human eye represents an attempt to achieve the best possible visual experience. The newest generation of intraocular lenses, such as the IQ lens attempt to do this based on the above scientific principles.

We provide a variety of standard collimating lenses, including aspheric and achromatic lenses, suitable for many different light sources such as highly divergent laser diodes. Our standard collimating lenses can convert divergent laser beams into well-collimated beams, ideal for applications like interferometry, laser material processing, and laser scanning. To reduce the lead time, you can build your own beam expanders to meet application requirements by selecting different sets of our standard collimating or focusing lenses. Using our standard collimating / focusing lenses, the beam expander can be designed to have magnification up to 10 times for the wavelengths of 405 nm, 543 nm, 633 nm, 780 nm, 1064 nm, 1310 nm, 1550 nm, and 2000 nm.

The MTF of an ideal optical system (one with no loss of contrast, or detail) would be a horizontal line. Of course, this is impossible to achieve. At some point, the MTF becomes 0; which is known as the cutoff frequency. A SWG with a frequency exceeding the cutoff will image as uniform gray, with no variation in contrast. In other words, SWGs with frequencies above the cutoff do not appear in the image. SWGs with frequencies below the cutoff appear in the image, but at reduced contrast when compared to the original. The cutoff frequency roughly corresponds to the resolution.  The MTF gives a more complete evaluation of optical performance than resolution, but it is harder to measure and interpret.

where Tmax is the maximum transmittance of the grating and Tmin is the minimum  transmittance. When we look at the ratio of the transmission from the light and dark bars, we are measuring contrast. We can look at a sine wave grating in the same manner. Now, let’s assume that you have a sine wave grating of a specific frequency (u) and modulation (contrast), and its image is passed through a lens. The modulation of the image can now be measured. The modulation transfer function at a specific frequency, MTF(u), is defined as the modulation, Mi, of the image divided by the modulation of the object, Mo, and is described by the following:

Collimatinglens

The most common way that MTF is explained is as an analogy to sound. Just as in optical imaging, audio recordings do not perfectly duplicate the original. A sound consists of many individual frequencies, or pure tones, simultaneously reaching the ear. Two parameters characterize a pure tone: the frequency, or tone, and the loudness, or volume.  A pure tone is typically represented by a sine wave.  The horizontal distance between peaks determines the frequency and a vertical distance from peak to valley determines the volume. Of course, most sounds are a mixture of many hundreds of different frequencies, each with its own volume. This would be a complex sound. In much the same way, an optical image is made up of many spacial frequencies and differing amounts of contrast.

Intraocular lenses used in ophthalmic surgery are generally spherical, are made of either silicone or plastic and have a single index of refraction. They are also not generally aspheric, and as such produce positive spherical aberration due to the fact that pencils of light traveling through the visual axis (known as paraxial rays) are bent less than those that travel through an area away from the visual axis (known as marginal rays).

Collimating lenses are used to convert divergent light beams into parallel beams and are designed for various applications from the UV to visible to long wave infrared spectrum. At Shanghai Optics, we design and manufacture a wide variety of standard and custom collimating lenses for customers around the world. Learn more about these lenses and their uses below.

The collimating lens typically consists of an aluminum housing with one or more lens elements and is designed with the required focal length, diameter and mount. The main purpose of a collimating lens is to collect light from a light source and produce a parallel beam of light with the required spatial resolution. A collimating lens can be attached directly to the measurement device or testing instrument. Collimating lenses can slide relative to the lens fixture to adjust the focus position.

Collimated lightsource

Alpha Industrial Park, Tu Thon Village, Ly Thuong Kiet Commune, Yen My District, Hung Yen Province Vietnam 17721 +84 221-730-8668 rfqvn@shanghai-optics.com

The greater the power of a spherical intraocular lens, the more spherical aberration it will produce. And the more the spherical aberration, the more the MTF is degraded, almost like unwanted noise in a poor quality sound recording. With an intraocular lens of a non-physiologic power, such as +35.00 diopters, there is an increase in spherical aberration on the order of the square of each doubling of diopteric strength.  This means that there is roughly four times as much spherical aberration for a +35.00 diopter intraocular lens as there would be at an intraocular lens implant power of +17.50 diopters.

Laser collimation

Whenever light passes through a reflective object, it scatters into different angles. An optical collimator transforms a divergent beam of light into a parallel beam and reduces the spatial cross-section of the light beam, making it smaller. When collimating lenses are attached to light sources and/or spectrometers, the light enters the sample at a specific angle with minimal variation, contributing to stable and repeatable measurement results. Collimation ensures that light rays travel parallel to each other and do not disperse in unwanted directions.

At Shanghai Optics, we design and manufacture custom and pre-engineered collimating lenses to meet customers’ application requirements. For some simple projects like laser collimators and beam expanders with the need for fast turnaround time, we can provide many different standard collimating lenses with different diameters, focal lengths, coating, and mounting sizes. For collimating lenses, we offer different coating options including the coating for the wavelength of 405 nm, 543 nm, 633 nm, 780 nm, 1064 nm, 1310 nm, 1550 nm, 2000 nm, etc.

Now back to the audio analogy.  Just as a typical sound is a mixture of many pure frequencies, optical images are also mixtures of many SWGs. The image of a single SWG has the same frequency and orientation as the original SWG, but the contrast is always decreased. The ratio of the image SWG contrast and the object SWG contrast is the transfer factor. The transfer factor is always between 0 and 1 and different frequencies have different transfer factors.  The graph of transfer factor vs. frequency is the modulation transfer function and is analogous to the frequency response curve of an audio system.

Optical images of any kind can be analyzed in much the same way. The difficult part here is that the optical analogy of a pure tone is a sine wave grating, or SWG. The frequency of the sine wave grating is determined by the horizontal peak-to-peak distance. The sine wave grating contrast is indicated by the difference in brightness between the brightest and darkest points, and is analogous to the volume of a tone. One difference between sound and optics is that SWGs also have an orientation, which can be vertical, horizontal, or oblique.

Modulation transfer is the ability of a lens system to transfer an object’s contrast to its image.  Modulation is therefore a ratio of image contrast to object contrast. Ideally, it would be one, or 100%. Modulation transfer plots describe the modulation of a lens system as the object increases in complexity. Therefore, the Y-axis is modulation and the X-axis is spatial frequency, measured in line pairs per millimeter. As you would expect, as the spatial frequency increases, the modulation of any lens system decreases. Outside of optical engineering, most are unfamiliar with the importance of MTF because there are no easy ways to standardize it.

For a Ronchi rulings there are basically dark bars and light bars and we can measure the amount of light coming from each. The maximum amount of light will come from the light bars and the minimum from the dark bars. If the light in a lens system is measured in terms of transmittance (T) we can define modulation according to the following equation:

Unlike a sine wave grating, which gradually changes from dark to light, another pattern, known as Ronchi rulings, change abruptly and is instead is based on a square wave rather than a sine wave. Snellen figures (the standard visual acuity eye chart) are essentially Ronchi rulings. This is why Snellen acuity is such a poor way to asses visual performance. Contrast sensitivity testing, using charts that are basically SWGs, provides a more complete evaluation of visual performance, but this is a more complicated test to administer and is poorly understood by those outside of optics and ophthalmology, such as insurance companies.

We also provide custom collimating lenses for projecting a source at infinity for infinite conjugate testing of optical systems. These lenses can consist of several optical elements. The selection of optical materials and configuration depends on the entrance pupil diameter, wavelength, focal length, and field of view of the optical system under test.

If a single pure tone is recorded, the frequency of the recording matches the frequency of the original, but the recorded volume usually changes. The ratio of the recorded volume to the original volume would be the measured response of an audio system to that particular frequency. If an audio system has different responses to different frequencies, the recorded sound will not match the original. However, if the audio system has the same response to all frequencies, the recorded sound will duplicate the original sound. A graph of response vs. frequency, known as a frequency response curve, is typically constructed to show the fidelity, or frequency response of any audio system. High-end audiophiles spend much of their time (and most of their money) chasing this.