Hamilton's optico-mechanical analogy - mechanic optics

 2024-08-06 23:02:44

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You can plug a USB 2.0 device into a USB 3.0 port and it will always work, but it will only run at the speed of the USB 2.0 technology.

Released in September 2017, USB 3.2 allows compatible devices to take advantage of the SuperSpeed (5 Gbit/s) or SuperSpeed+ (10 Gbit/s) transfer rates. However, this latest version also introduced a new SuperSpeed+ mode (20 Gbit/s) that comes into play when using a USB-C connector and the very latest models of devices.

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Here the confusion arose, as USB’s creators called its new version USB 3.1 Gen 2 (second generation), while giving USB 3.0 the new name of USB 3.1 Gen 1 (first generation).

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One of the most user-friendly aspects of USB is that its primary shape—the classic rectangle (Type-A) —is physically compatible with all earlier versions. This means USB Type-A plugs in versions 3.0, 3.1 or 3.2 will fit into old USB 2.0 ports and vice versa.

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By the time version 3.0 came along, USB was well established as the industry standard. In 2013 came USB 3.1, which doubled speeds to 10 Gbit/s—known as SuperSpeed+—when using USB Type A and USB-C connectors. (Read more on the different types of USB connector here.)

A USB 2.0 cable has four wires inside it—a USB 3.0 cable has eight—and so will only transfer data at USB 2.0 speed. All components in the chain—the two devices and the cable—must be USB 3.0 to achieve that later version’s high speeds.

The function to create a magnified image of a specimen consists of three basic functions of "obtaining a clear, sharp image", "changing a magnification", and "bringing into focus". An optical system for implementing these functions is referred to as an observation optical system. Meanwhile, the function to illuminate a specimen consists of three basic functions of "supplying light", "collecting light", and "changing light intensity". An optical system for implementing these functions is referred to as an illumination optical system. In other words, the observation optical system projects a sample (specimen) through an optical system and moreover leads a projection image to eyes or a pickup device such as CCD. On the other hand, the illumination optical system effectively collects light emitted from the light source and leads the light to a specimen to illuminate it. The layout of observation and illumination optical systems in an optical microscope is as in the figure below for an upright microscope. Meanwhile, for an inverted microscope the layout relation between those optical systems is upside down at the center of a specimen with respect to an upright microscope.

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Launched in 2008, USB 3.0 improved significantly on its predecessor USB 2.0 by introducing SuperSpeed, a new data transfer rate that increased processing speeds more than tenfold, from 480 Mbit/s to 5 Gbit/s.

So, if you plug a USB 3.0 flash drive into a USB 2.0 port, it would only run as quickly as the USB 2.0 port can transfer data and vice versa.

However, where USB Type-C differs is that it’s been created purposely to take advantage of the new USB 3.1 standard. So rather than the version determining the speed and power at which data can be transferred, with USB-C it’s the connector itself.

Because USB 3.2 is still in development, it’s unlikely to be widely adopted until the industry has made its hardware fully compatible.

Compound microscope

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Yet despite being built into some of the latest hardware (newer MacBooks, for example), USB 3.1 wasn’t very widely adopted. The smartphones and other devices many people use today tend to feature USB 3.0 or earlier versions.

An optical microscope creates a magnified image of an object specimen with an objective lens and magnifies the image further more with an eyepiece to allow the user to observe it by the naked eye. Assuming a specimen as AB in the following figure, primary image (magnified image) A'B' of inverted real image is created with an objective lens. (ob). Next, arrange the eyepiece (oc) so that primary image A'B' is located closer to the eyepiece than the anterior focal point, then more enlarged erect virtual image A"B" is created. Put your naked eye in the eye (pupil) position on the eyepiece barrel to observe the enlarged image. In short, the last image to be observed is an inverted virtual image. As described above, this type of microscope which creates a magnified image by combining an objective lens making an inverted real image and an eyepiece making an erect virtual image is called a compound microscope. The observation optical system in an optical microscope is commonly standardized on this compound microscope. Meanwhile, such type of microscope that directly observes an inverted real image magnified with an objective lens is called a single microscope. A microscopic observation on a TV monitor, recently popularized increasingly, uses the way of directly capturing this inverted real image with a CCD camera, thereby being comprised of a simple microscope optical system.

As the USB standard has developed over time, it’s seen improvements in terms of speed and power, making it much quicker to run and charge USB devices and transfer data.

Anything with a version number (e.g. 2.0 or 3.0) is a standard—the technology that allows data to be transferred along a cable from one device to another.

Optical microscopes are categorized on a structure basis according to the intended purpose. An upright microscope (left photo) which observes a specimen (object to be observed) from above is widely known as the most common type with a multitude of uses. An inverted microscope (right photo) which observes a specimen from beneath is used for observing the mineralogy and metallogy specimens, etc.

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