Key Takeaways Optical filters like Longpass, Shortpass, Bandpass, Multi-bandpass, Notch, and Neutral Density are essential for controlling wavelength ranges in diverse applications. The electromagnetic spectrum comprises Gamma rays, X rays, UV, visible light, IR, and radio waves. Human eyes perceive colors in visible light (380-780nm), while optical filters play a vital role in manipulating light for diverse purposes. Understanding the Electromagnetic Spectrum and Human Vision The electromagnetic spectrum encompasses a broad range of wavelengths, including Gamma rays, X rays, ultraviolet, visible light, infrared, and radio waves, arranged in order from shorter to longer wavelengths. Despite this extensive spectrum, our eyes are restricted to detecting visible light, which spans from 380 to 780nm in wavelength. Consequently, these variations in wavelength translate into visible light appearing as an array of distinct colors to the human eye. Visible Spectrum Exploring the Diversity of Optical Filters in Design and Manufacturing In the optical field, an optical filter stands out as one of the most prevalent components in design and manufacturing. The selective transmission of specific wavelengths and the blocking of unwanted light are accomplished through the utilization of optical filters. These filters, available in a variety of designs, include: Longpass filters, designed to transmit wavelengths above a specified value, exclusively allow longer wavelengths to pass while blocking shorter ones. Notably, these filters exhibit a sharp cut-on, gradually approaching zero transmission in the blocking range and nearing 100% transmission in the passband. Longpass Filter Shortpass filters, contrasting with longpass filters, exclusively permit the passage of shorter wavelengths while obstructing longer ones. In contrast, they exhibit a sharp cut-off, gradually approaching zero transmission from the high transmission end. Shortpass Filter Bandpass filters, in essence, can be seen as a fusion of longpass filters and shortpass filters. These filters exhibit high transmission within a specified wavelength range while effectively blocking all other wavelengths. Bandpass filter Multi-bandpass filters, can be regarded as duplication of bandpass filters, which have high transmission for multiple wavelength regions; Multi-bandpass Filter Notch filters, alternatively known as band stop filters, serve to obstruct a designated wavelength range while permitting the transmission of light on either side of that range. Notably, the shape of the curve on a wavelength–transmission chart resembles a V. Notch Filter Neutral density (ND) filters, conversely, serve to uniformly diminish the intensity of all wavelengths, ensuring the preservation of color integrity. Notably, a prevalent application of ND filters is discovered in photography. Once attached in front of the lens, an ND filter provides photographers with precise control over the light reaching the sensor. This empowerment enables photographers to finely adjust various specifications, thereby preventing overexposure and ultimately producing superior results in photos. Neutral Density Filter Typical Applications of Optical Filters Optical filters find extensive applications across various fields, encompassing photography, optical instruments, color lighting, astronomy, and fluorescence microscopy and spectroscopy. Illustratively, fluorescence filters enhance fluorescence microscopy systems. Additionally, laser line filters are employed in laser devices to prevent distortion and enhance image contrast. Raman filters play a crucial role in Raman spectroscopy, and machine vision filters are utilized in machine vision camera and sensor applications to enhance image contrast. RELATED CONTENT:

Key Takeaways Type of microscope objective lenses, such as Achromatic and Plan Apochromatic, are vital for imaging and address specific aberration correction needs. Corrections for cover glass thickness and working wavelengths are vital for optimal performance. Balancing magnification and resolution, alongside factors like working distance, ensures detailed observations. Critical Role of Objective Lenses in Microscopy In microscopes, objective lenses play a crucial role as the most complex and important component. These lenses, designed as multi-element lenses located closest to the specimen, receive light emitted by the specimen. Their primary function is to produce a real image, which is then transmitted to the eyepiece or computers. Widely employed in scientific research, biology, industry, and laboratory work, these lenses serve essential functions in various fields. Objective Lenses Types of Objective Lenses A diverse array of objective lenses, classified as types of objective lenses, is available for selection based on design and quality. The classification is generally determined by intended purpose, microscopy method, performance, magnification, and aberration correction. In this article, we will introduce the five types of objective lenses classified by aberration correction. Achromatic Objectives: These objective lenses, recognized as achromatic lenses, are not only widely used but also the most affordable. If no markings suggest otherwise, one can assume their achromatic nature. These lenses proficiently correct chromatic aberration in red and blue light, ensuring the convergence of these wavelengths at a single focal point, while also addressing spherical aberration in green light. Plan Achromatic Objectives (Achroplan): In a non-corrected objective, you can find sharp focus around the edges of the field of view or the center of the field of view. This type of microscope lens offers correction for chromatic aberration in two wavelengths and a correction of field curvature. Plan Fluorite Objectives (Plan Semi-Apochromats): These lenses were originally manufactured using the mineral fluorite, but now are mainly made of synthetic materials. These versatile lenses provide improved chromatic aberration correction and a flat field, with spherical aberration corrected for two wavelengths. Plan Apochromatic Objectives (Plan Apo): These lenses outperform Plan Fluorite Objectives by achieving superior transmission in the 400nm to 100nm range. They actively correct chromatic aberration for three colors (red, green, and blue), ensuring the convergence of these wavelengths at a single focal point. Furthermore, they actively correct spherical aberration for two or three wavelengths. Super Apochromatic Objectives: These lenses deliver outstanding performance over the entire visible to near-infrared field of view with axial color aberration. Objective Lenses Objective Lenses Key Specifications in Microscopy Aberration Correction or Resolution: Spherical and chromatic aberrations limit the resolution of conventional microscopes. Lenses with a high degree of aberration correction result in high-resolution images over the entire field of view. Magnification: Magnification refers to a microscope’s capacity to produce larger images, and high-magnification objectives offer detailed specimen images. Observers often confuse magnification with resolution, which defines an imaging system’s ability to reveal object detail. High magnification without adequate resolution may render small microbes visible but prevents distinguishing between microbes or sub-cellular parts. Avantier has dedicated years to design and manufacturing, ensuring simultaneous fulfillment of both magnification and resolution requirements. Numerical Aperture (NA): NA is the measure of its capability to gather light and to resolve fine specimen details at a fixed object. A lens with a high NA collects more light and can resolve finer specimen details at a fixed distance. Conjugate Distance: Objectives are corrected for a specific projection distance. In finite conjugate optical design, light from a non-infinite source is focused down to a point. In infinity-corrected optical systems, light emitted from the specimen passes through the objective lens and enters the tube lens as an infinity parallel beam, forming a real image. Cover Glass: Objectives are usually corrected for a specific cover glass thickness, with 0.17 millimeters being the standard. Immersion Media: The main purpose of using different types of immersion media is to minimize the refractive index between the objective and the sample. It is crucial to use the correct media, such as water, oil, or air/dry, as specified by the objective. Working Distance: The distance between the front end of the microscope objective and the surface of the specimen at which the sharpest focus is achieved. Proper positioning is important to obtain a good image at the specified magnification. Parfocal Length: The distance from the shoulder of the objective to the sample plane.  Working Wavelength(s): Objectives are corrected for specific wavelengths, with shorter wavelengths yielding higher resolution. RELATED CONTENT:

Manufacturing optical components faces challenges in achieving full clear apertures meeting specifications.

Key Takeaways Field of View (FOV) in a camera lens, influenced by focal length and sensor size, captures the scene. Angular Field of View (AFOV), measured in degrees or length, is determined through optical tests. Shorter focal lengths intensify light convergence, affecting Angular FOV. Exploring the Field of View (FOV) in Camera Lenses The camera lens captures the extent of the observable area in a single shot, known as the Field of View (FOV). This encompasses what one can see through the eyes or an optical device. In photography, the FOV determines “what we are seeing in our image” and “how much of the scene we are seeing.” As light passes through the camera lens, it focuses on the subject being imaged by converging the light. Shorter focal lengths intensify the convergence of light to focus on the subject being imaged. Focal Length & Angle of View Guide Focal Lengths and Field of View (FOV) Dynamics Conversely, shorter focal lengths focus the image by converging the light more intensely. The determination of the focal length distance depends on how strongly the lens converges the light to focus the subject being imaged. This, in turn, affects the angle from the horizontal of the light captured by the lens. Referred to as the angular field of view (AFOV), it is necessary for determining the overall FOV. The FOV is expressed in either angular or size terms, with the former indicating the full angle in degrees and the latter denoting the length in millimeters or meters. Influences on Field of View (FOV) The lens focal length and sensor size influence the FOV, necessitating a wider FOV for a larger sensor if the lens focal length remains fixed. Typically measured horizontally due to the rectangular shape of sensors, FOV is usually expressed in millimeters. Optical tests commonly determine the FOV of UV, visible, and infrared cameras. These tests involve focusing light from a black body (an object that absorbs all light that falls on it) onto a test target at the focal place. A set of mirrors creates a virtual image at an infinitely far distance during the test. Camera FOV (or Camera Coverage) Field of View Formula Note: f is the lens focal length. Camera FOV vs. Lens FOV The image below shows the difference between the camera FOV and lens FOV. Camera FOV vs. Lens FOV Note: the maximum image (circle) diameter of the lens should be equal to or larger than the Sensor diagonal size. RELATED CONTENT