High powerobjective

Optical wave plates are constructed from birefringent materials that have a difference in refractive index between two orthogonal axes. This birefringent property introduces a velocity difference between light polarized along the fast and slow principal axes of the wave plate. The fast principal axis of the wave plate has a lower refractive index, resulting in a faster velocity for light polarized in this direction. Conversely, the slow axis has a higher refractive index, resulting in a slower velocity for light with this polarization. When light passes through a wave plate, this velocity difference leads to a phase difference between the two orthogonal polarization components. The actual phase shift depends on the properties of the material, the thickness of the wave plate, and the wavelength of the signal, and can be described as:

The higher the NA, the smaller the distance between two objects. As we mentioned previously, choosing the right NA for your application is crucial in determining the resolution of your microscope system.

There are many different types of objectives available for microscopes, but without a basic understanding of how they work, it can be difficult to know which ones are best suited to the specific needs you have. That's why this article takes you through the basics points to keep in mind ,so that you'll have a better idea of what type is right for your needs.

Objectivelens microscope function

In addition to these options, Thorlabs also has the ability to design and manufacture custom wave plates for both OEM sales and individual low quantity orders. Our technical staff is able to help with all phases of your request: quoting, sales, and planning and manufacturing support. If you have a custom request or a question about our capabilities, please contact Tech Support to start a discussion.

Low powerobjective magnification

Each objective and eyepiece has a specific purpose or function. Objective lenses magnify the image that enters the objective and bring it to a sharp, clear focus. Eyepieces take the light that has been focused by the objective lenses and magnify it further so that you can see it. The magnification power is measured by objective magnification multiplied by eyepiece magnification.

Types ofobjectivelenses

Attach each objective to each lens mount hole of the revolving nosepiece, starting from the lowest magnification objective and increasing the magnification in the clockwise direction seen from the bottom. By attaching objectives in this way, the objectives can be switched in ascending order of magnification

The resolution of the microscope objective determines the smallest distance between two objects that can be observed. It is directly proportional to the illumination wavelength of light and inversely proportional to the NA.

Is the distance from the objective’s front lens to the closest surface of the coverslip when the specimen is in focus? WD is inversely proportional to the NA, which means that higher NA objectives typically have low working distances.

MIR Wave Plates are made from a single piece of high-quality magnesium fluoride and provide either quarter-wave or half-wave retardance at 2.5 µm, 2.713 µm, 2.94 µm, 3.5 µm, 4.0 µm, 4.5 µm, or 5.3 µm. Light passing through these MIR wave plates will undergo a low number of full or partial wavelength shifts (also referred to as the order, or m) in addition to the fractional design retardance. This differs from true zero-order and multi-order wave plates which undergo no shift or a high number of shifts, respectively. The low-order design maintains near to true zero-order performance, making it a good alternative to true zero-order wave plates. The single magnesium fluoride substrate is also thinner compared to a zero-order design, which combines two multi-order wave plates, making our low-order retarders well suited for applications that are sensitive to dispersion.

The angle between the output polarization and the input polarization will be twice the angle between the input polarization and the wave plate’s axis (see diagram to the lower right). When the polarization of the input beam is directed along one of the axes of the wave plate, the polarization direction will remain unchanged.

What is objectivelens in microscope

Achromatic Wave Plates provide phase retardance that is relatively independent of wavelength over a wide spectral range, and Superachromatic Wave Plates provide phase retardance almost entirely independent of wavelength over a much wider range than achromatic wave plates. In contrast, zero-order and multi-order wave plates provide a phase shift that is strongly wavelength dependent. Our achromatic wave plates are available with four operating ranges: 260 - 410 nm, 350 - 850 nm, 400 - 800 nm, 690 - 1200 nm, and 1100 - 2000 nm. Additionally, we offer superachromatic wave plates for the 310 - 1100 nm and 600 - 2700 nm ranges.

Denoted by a number (such as 0.17mm) the cover slip thickness is labeled on the objective to note the type of cover slip that should be used. A cover slip changes the way light is refracted from the specimen. Therefore, it is important to ensure that the right cover slip is used in order to produce a good quality image. Zero(0) denotes no coverslip to use. Dash(-) denotes use of coverslip or no cover slip, it does not matter.

Half-wave (λ/2) plates are typically used as polarization rotators. Mounted on a rotation mount, a λ/2 wave plate can be used as a continuously adjustable polarization rotator, as shown below. Additionally, when used in conjunction with a Polarizing Beamsplitter a λ/2 wave plate can be used as a variable ratio beamsplitter.

The objective depth of field is the axial range, which enables you to focus an objective without any considerable change in image sharpness. This value varies radically from low to high numerical aperture objectives; it usually decreases as the numerical aperture increases.

As described above, a wave plate has two principal axes: fast and slow. Each axis has a different refractive index and, therefore, a different wave velocity. When a linearly polarized beam is incident on a half-wave plate, and the polarization of this beam does not coincide with one of these axes, the output polarization will be linear and rotated with respect to the polarization of the input beam (see image at right). When applying a circularly polarized beam, a clockwise (counterclockwise) circular polarization will transform into a counterclockwise (clockwise) circular polarization.

Multi-Order Wave Plates are made such that the retardance of a light path will undergo a certain number of full wavelength shifts (also referred to as the order, or m) in addition to the fractional design retardance. Compared to their zero-order counterparts, the retardance of multi-order wave plates is more sensitive to wavelength and temperature changes. Multi-order wave plates are, however, a more economical solution for many applications where increased sensitivities are not an issue. Our multi-order wave plates are available for a number of discrete wavelengths ranging from 405 nm to 1550 nm. Thorlabs also offers Dual-Wavelength Multi-Order Wave Plates designed for use at both 532 nm and 1064 nm.

What is objective magnificationin microscope

In a finite conjugate design, the objective focuses light from the object into the focal plane of the eyepiece. An infinite corrected objective collects light from the object and forms a parallel beam that passes through a tube lens.  The advantage of this design is that additional optical elements, such as polarizers, filters, and wave-plates, can be placed in between the tube lens and the objective without interfering with the focusing of the beam. The infinite conjugate design is often used in fluorescence microscopes, which rely on filters.

High powerobjectivemicroscope function

Thorlabs offers achromatic, superachromatic, zero-order (both unmounted wave plates and mounted wave plates), low-order, and multi-order wave plates (single wavelength and dual wavelength) with either λ/4 or λ/2 phase shift.

A quarter-wave plate is designed such that the phase shift created between the fast and slow axes is a quarter wavelength (λ/4). If the input beam is linearly polarized with the polarization plane aligned at 45° to the wave plate's fast or slow axis, then the output beam will be circularly polarized (see image at right). If the linearly polarized beam is aligned at an angle other than 45°, then the output will be elliptically polarized. Conversely, the application of a circularly polarized beam to a λ/4 wave plate results in a linearly polarized output beam. Quarter wave plates are used in Optical Isolators, optical pumps, and EO Modulators.

What is objective magnificationused for

It is an angle of incidence. It is the most important parameter of a microscope. NA measures its ability to gather light. It’s an important factor to determine resolution, depth of focus, and the brightness of images. Objectives with a larger NA gather a wider range of light, resulting in brighter, higher resolution images.

NA is also important to observe very fine structures or detect dim signals during fluorescence observation. When determining which microscope objective will resolve the smallest feature in your specimen, think about the NA. As you weigh your options, keep in mind that numerical aperture typically ranges between 0.10 to 1.25.

Zero-order wave plates are designed such that the phase shift created is exactly one quarter or one half of a wave. They offer substantially lower dependence on temperature and wavelength than multi-order wave plates. Our Zero-Order Quartz Half-Wave and Quarter-Wave Plates are composed of two wave plates stacked together with the fast axis of one aligned to the slow axis of the other to achieve zero-order performance. Thorlabs' zero-order wave plates are available for a number of discrete wavelengths ranging from 266 nm to 2020 nm. Our Polymer Zero-Order Half-Wave and Quarter-Wave Plates consist of a thin layer of liquid crystal polymer retarding material sandwiched between two glass plates and are available at discrete wavelengths between 405 nm and 2700 nm. Our quartz zero-order wave plates provide better retardance accuracy and lower reflectance (see table), while our LCP zero-order wave plates produce a smaller decrease in retardance at larger AOIs. In addition, Thorlabs also offers unmounted true Zero-Order Telecom Wave Plates for WDM applications.

Optical correction such as achromatic, apochromatic, plan and semi-plan are often denoted on the objective in order to show the design of the objective. Plan and semi-plan objectives correct for field curvature. Field curvature often results in blurred images on the periphery and correction for this helps produce good quality images. Whereas plan objectives correct better, allowing for better display (over 80 per cent) of field flat, semi-plain objectives produce about 65 per cent.

On the objective, this is usually denoted by an X next to a numeric value (100X, 10X etc). On the other hand, objectives will also have a colored band around the circumference of the objective that indicates the magnification of the objective. For instance, a yellow band around the objectives (lower part of the objective) indicates that it is a 10x objective.

Wave plates are typically available with a retardance of λ/4 or λ/2, meaning that a phase shift of a quarter wavelength or a half a wavelength (respectively) is created.

where n1 is the refractive index along the slow axis, n2 is the refractive index along the orthogonal fast axis, d is the thickness of the wave plate, and λ is the signal wavelength.