elements with different background colors. The left-hand one is given the unmodified --base-color, while the middle and right ones are given variants of that --base-color that successively remove more from the red channel and add more to the blue channel.

Darkfield illumination directs light rays obliquely onto the object, avoiding direct entry into the objective. Despite this oblique angle, the rays still illuminate the object plane. The resulting darkfield illumination image achieves high contrast between the transparent object and the light source. In a darkfield setup, a light source forms an inverted cone of light that blocks central rays but allows oblique rays to illuminate the object (see Figure 3). This design effectively forces light to illuminate the object without entering the optical system, making darkfield illumination particularly suitable for transparent objects. In contrast, no rays are blocked in a brightfield illumination setup.

In many microscopes, backlight illumination is favored over traditional direct light illumination due to the latter’s tendency to over-saturate the object under inspection. One specific backlight illumination technique employed in microscopy is Koehler illumination. This method involves flooding the object with light from behind using incident light from a source like a light bulb (see Figure 2). Koehler illumination utilizes two convex lenses, the collector lens and the condenser lens(or called field lens) , to ensure even and bright illumination on both the object and image planes. This design prevents imaging the light bulb filament, a common issue with direct light illumination. Backlight illumination is also commonly referred to as brightfield illumination.

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Microscope objective lenses, vital optical elements in microscopy, enable precise observation of specimens. Objective lens manufacturers offer a wide range of objective designs for specific needs: high power for detailed observation, scanning for broader views, oil immersion for high-resolution imaging, and long working distance for manipulation without compromising quality. Those objectives are designed with advanced construction techniques for high performance objectives with a spring loaded retractable nose cone assembly that protects the front lens elements and the specimen from collision damage.

This is the most common method, but if you focus on the center of the field of view, the periphery becomes blurred, so it is not suitable for inspection photography.

In the following example, the hsl() origin color is again converted into an rgb() representation — rgb(255 0 0). calc() calculations are applied to the R, G, B, and A values. After calculating, the R, G, B and A values are 127.5, 25, 175, and 0.9 respectively. The final output color is the equivalent of rgb(127.5 25 175 / 0.9) in the sRGB color space: color(srgb 0.5 0.0980392 0.686275 / 0.9).

In the following content, we delve intensively into the various components and features of microscope objective lenses, exploring their construction, functionality, and specialized designs that enable researchers to gain deeper insights into the microscopic world.

Note: As mentioned above, if the output color is using a different color model to the origin color, the origin color is converted to the same model or space as the output color in the background so that it can be represented in a way that is compatible (i.e. using the same channels).

Confocal microscopy offers the capability to capture sharp images from a slender slice of a dense sample, minimizing background noise and reducing out-of-focus disturbances. Optical sectioning, widely employed in biomedical science and materials science, involves placing a sample on the microscope stage. An image is initially acquired at the primary focal plane, and subsequently, the stage or objective is adjusted vertically to capture images at successive focal planes.

Infrared microscopy, alternatively referred to as infrared microspectroscopy, is a form of light microscopy that employs a light source transmitting infrared wavelengths to observe a sample’s image. In contrast to conventional optical microscopes utilizing absorbent glass optics, an infrared microscope incorporates reflective optics, enabling it to encompass the complete spectral range of infrared light.

Epi-illumination, a third form of illumination employed in microscopy, generates light from above the objective. This setup replaces the need for a Koehler illumination configuration, as both the objective and the epi-illumination source contribute to the illumination process. The compact structure  of epi-illumination is a significant advantage, as the objective serves as a primary source for a considerable portion of the illumination. Figure 4 provides a depiction of a frequently used epi-illumination setup, particularly common in fluorescence applications.

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Although today’s microscopes are usually far more powerful than the microscopes used historically, they are used for much the same purpose: viewing objects that would otherwise be indiscernible to the human eye.  Here we’ll start with a basic compound microscope and go on to explore the components and function of larger more complex microscopes. We’ll also take an in-depth look at one of the key parts of a microscope, the objective lens.

It is suitable for inspection photography because it focuses not only on the center of the field of view but also on the periphery, producing a flat image.

In the examples we've seen so far in this section, the alpha channels have not been explicitly specified for either the origin or output colors. When the output color alpha channel is not specified, it defaults to the same value as the origin color alpha channel. When the origin color alpha channel is not specified (and it is not a relative color), it defaults to 1. Therefore, the origin and output alpha channel values are 1 for the above examples.

Both the objective lens and the eyepiece also contribute to the overall magnification of the system. If an objective lens magnifies the object by 10x and the eyepiece by 2x, the microscope will magnify the object by 20 times. If the microscope lens magnifies the object by 10x and the eyepiece by 10x, the microscope will magnify the object by 100x. This multiplicative relationship is the key to the power of microscopes, and the prime reason they perform so much better than simply magnifying glasses.

While a magnifying glass consists of just one lens element and can magnify any element placed within its focal length, a compound lens, by definition, contains multiple lens elements. A relay lens system is used to convey the image of the object to the eye or, in some cases, to camera and video sensors.

When using relative color syntax inside an rgb() function, the browser converts the origin color into an equivalent RGB color (if it is not already specified as such). The color is defined as three distinct color channel values — r (red), g (green), and b (blue) — plus an alpha channel value (alpha). These channel values are made available inside the function to be used when defining the output color channel values:

Numerical aperture, magnification, optical tube length, degree of aberration correction, and other important characteristics are typically imprinted or engraved on the external portion of the barrel for easy reference. These specifications help researchers select the appropriate objective for their experiments, ensuring optimal performance and total magnification when combined with the ocular lens. Specifications like numerical aperture and magnification are typically labeled on the barrel for easy reference. These lenses are indispensable in scientific research providing high powered optics essential for research.

Microscopes are usually complex assemblies that include an array of lenses, filters, polarizers, and beamsplitters. Illumination is arranged to provide enough light for a clear image, and sensors are used to ‘see’ the object.

In terms of performance, it is positioned between the plan achromat objective lens and the plan apochromat objective lens. High Grade type.

Avantier is a premier manufacturer of high performance microscope objective lenses, and we produce a wide range of quality microscope objectives for applications ranging from research to industry to forensics and medical diagnostics. We carry many types of objectives in stock, including apochromat objectives, achromatic objectives,  and semi apochromat objectives.  We can also produce custom objectives designed to work as desired in your target spectral range.

An representing the alpha channel value of the output color, where the number 0 corresponds to 0% (fully transparent) and 1 corresponds to 100% (fully opaque). Additionally, the keyword none can be used to explicitly specify no alpha channel. If the A channel value is not explicitly specified, it defaults to the alpha channel value of the origin color. If included, the value is preceded by a slash (/).

A microscope is an optical device designed to magnify the image of an object, enabling details indiscernible to the human eye to be differentiated. A microscope may project the image onto the human eye or onto a camera or video device.

The keyword from is always included when defining a relative color, followed by a value representing the origin color: This is the original color that the relative color is based on. The origin color can be any valid syntax, including another relative color.

When defining a relative color, the different channels of the output color can be expressed in several different ways. Below, we'll study some examples to illustrate these.

The next function uses absolute values for the output color's channel values, outputting a completely different color not based on the origin color:

In modern microscopes, neither the eyepiece nor the microscope objective is a simple lens. Instead, a combination of carefully chosen optical components work together to create a high quality magnified image. A basic compound microscope can magnify up to about 1000x. If you need higher magnification, you may wish to use an electron microscope, which can magnify up to a million times.

Note: The rgba() functional notation is an alias for rgb(). They are exactly equivalent. It is recommended to use rgb().

Each value can be represented as a between 0 and 255, a between 0% and 100%, or the keyword none (equivalent to 0% in this case). These values represent the red, green, and blue channel values of the output color, respectively.

Choosing the right microscope objective is pivotal for optimal imaging performance. Consider your specific application requirements, utilize the provided guide, and explore Avantier’s diverse objective offerings to ensure accurate and reliable results in your microscopy endeavors.

Let's start with an origin color of hsl(0 100% 50%) (equivalent to rgb(255 0 0)). The following function outputs the same color as the origin color — it uses the origin color's r, g, and b channel values (255, 0, and 0) as the output channel values:

The chromatic aberration of the three wavelengths, with a slight chromatic aberration remaining in the purple, and the curvature of the field have been corrected. Also called fluorite.

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Let's look at some examples that specify origin and output alpha channel values. The first one specifies the output alpha channel value as being the same as the origin alpha channel value, whereas the second one specifies a different output alpha channel value, unrelated to the origin alpha channel value.

Each value can be represented as a between 0 and 255, a between 0% and 100%, or the keyword none (equivalent to 0% in this case). These values represent the red, green, and blue channels, respectively.

If you’re interested in acquiring in-stock microscope objective lenses, please visit our ‘Stock – Microscope Objective‘ page.

Fluorescence microscopy is a powerful imaging technique used primarily in biomedical research to visualize and study samples labeled with fluorescent dyes or proteins at the microscopic level. The method relies on the phenomenon of fluorescence, where materials absorb light at a specific wavelength (excitation light) and then emit light at a longer wavelength (emission wavelength). A focused light source, such as a laser, is used to selectively excite fluorescent molecules within the sample. The emitted fluorescence is captured to form detailed images, providing valuable information about the sample’s internal structure and composition.

In the above case, the output color is the sRGB color() equivalent of rgb(132 132 224): color(srgb 0.517647 0.517647 0.878431).