Resolution, also known as resolution and resolution, generally refers toMeasurementordisplay system The resolution of details determines the fineness of bitmap image details[1], usually used as a measure of the detail and clarity displayed in an image, video, or display device.Resolution describes the number and density of pixels in an image or video, as well as the level of detail that display devices can present, which can be subdivided intoDisplay resolution、Image resolution、Print resolutionandScanning resolutionEtc.In the field of display, resolution usually refers to the number of pixels in the horizontal and vertical directions of the screen.The resolution size is expressed by product, such as 1920 × 1080.When the screen resolution is high, there are many pixels displayed on the screen, and the size of a single pixel is relatively small.Image resolution refers to the amount of information stored in the image, usually the number of pixels contained in the unit inch.With the development of image technology, the image resolution will become larger and larger theoretically.
Resolution originated from screen display technology, and the development of screen display technology has promoted the continuous improvement of display resolution.
In 1869, German physicists Julius Pl ü cker and Johann Wilhelm Hittorf observed cathode rays for the first time.
In 1987, Karl Ferdinand Braun, a German physicist, invented CRT (method ray tube,crt）, originally known as the Braun tube, is also one of the earliest electronic displays in the world.
crt
In 1907, Boris Rosing, a Russian scientist, used CRT to transmit simple geometric images to the television screen, which became an important milestone in the television field.
In the late 20th century, cathode ray tubes were widely used in television and computer monitors.During this period, the performance and resolution of the display have been continuously improved.
In 1888, Friedrich Reinitzer, an Austrian botanist, discovered liquid crystals when studying cholesterol benzoate in carrots.
In 1990, IBM's XGA display displayed 16.8 million colors at a resolution of 800 × 600 pixels.
In 1936, K á lm á n Tihanyi, a Hungarian engineer, described the flat panel plasma display system in a paper.
In 1962, Richard Williams, a physical chemist in RCA laboratory, found that when a thin liquid crystal layer was applied with an electric field, the crystal would form a stripe pattern and enter a nematic state.
In 1962, General Electric engineer Nick Holonyack invented the world's first visible lightLED。
In 1964, Donald Bitzer, H. Gene Slottow and Robert Wilson shared by Barnes Champagne at the University of Illinois developed the first monochromatic plasma display for the PLATO computer system.
In 1969, Howard C. Borden and Gerald P. Pighini of Hewlett Packard Company launched the first LED device HP model 50282-7000 calculator using integrated circuit technology.
In 1987, Deng Qingyun, two chemists from Eastman Kodak, and Steven Van Slyke jointly developed the first practical OLED device.
In 1987, Digital Projection launched the first DLP projector.[2]
Fundamentals
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After a long period of development, display technology has derived a variety of technical routes.It can be mainly divided into the technology of the pre tablet era and the technology of the tablet era. The pre tablet era includes CRT technology. Its screen uses the principle of reflecting light of different colors into the eyes to form a picture. Combining RGB technology, a large number of RGB arrays are arranged on the screen, and then the brightness of each RGB light is adjusted to produce a specific color at a specific point to form a picture.LCD technologies in the tablet era include LCD,LED，OLEDEtc., using the lamp asBacklightLight source, through the control of auxiliary optical module and liquid crystal layer on light, achieves the most ideal display effect, with reasonable price and other advantages.Compared with traditional technologies, OLED technology has become a popular display technology with the advantages of ultra-thin, high contrast, energy saving and power saving.Some display technologies will be briefly introduced as follows:
sampling
In the real world, it means that the image first changes the continuous image in space into discrete points by sampling. The higher the sampling frequency, the more realistic the restored image will be[3]。In the relevant sampling technology, CRT uses a special electron gun to emit an electron beam that strikesFluorescent screenOn the screen, to achieve the effect of producing pictures.During shooting, the number of shooting positions determines the resolution of the screen display.
Cathode Ray Tube (CRT) Profile (Penetrating)
LCD color is processed by liquid crystal and polarizer to achieve RGB color.The larger the grid number of liquid crystal, the more details LCD can display.
LCD Schematic
LED is a matrix composed of numerous small light-emitting diodes, and each small light-emitting diode can be understood as a pixel.Compared with traditional LEDs, OLEDs use organic light-emitting materials and have different color forming methods.In OLED screen, RGB primary colors are arranged in 1:1:1, and each group can be regarded as a pixel block.
Schematic diagram of LED pixels
In the process of developing the display, the researchers found that the life span of the sub pixels of RGB tricolor was different. The life span was green>red>blue.Therefore, researchers invented Pentile technology to reduce the brightness required for imaging by increasing the volume of red and blue sub pixels, thus increasing the life of the display.In this process, the number of pixel blocks decreases, and the resolution of the image decreases.
OLED pixel block
At the same time, AMOLED (Active matrix organic light emitting diode) uses smaller sub pixels and diamond like sub pixel array, which greatly improves the life of the screen and image quality.
AMOLED pixel block
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PPI
Image Resolution refers to the amount of information stored in an image.This resolution can be measured in many ways, typically bypixelPPI (pixel per inch) and PPC (pixel per centimeter).Image resolution determines the quality of image output, and image resolution and image size (height and width) together determine the size of the file.The image resolution affects the size of the file in a proportional manner. Generally, the file size is proportional to the square of the image resolution.If you keep the image size unchanged and double the image resolution, the file size will be quadrupled.[4]
PPD (Pixels Per Degree) angular resolution, or spatial resolution, refers to the number of pixels filled in every 1 ° included angle in the field angle.
Unlike the mobile phone screen, which uses PPI to determine the screen definition, the definition of the head mounted display product is measured by PPD.Because the head mounted display is a virtual image magnified by the screen through the optical system (referred to as virtual image), rather than looking at the screen directly, PPI alone cannot measure the clarity of the head mounted display.When using the head mounted display product, the more pixels filled in the image of the unit area in the visual field of the human eye, the clearer and more exquisite the visual experience (before the clarity reaches the limit of the human eye).
The unit area of the field of vision can be represented by "the area of the average 1 ° field angle FOV". For the head mounted display products, "the area of the average 1 ° field angle FOV" is "the circle with PPD as the diameter".Through the formula of circle area, it can be concluded that the number of pixels in the area of "the average 1 ° field angle FOV" is proportional to the square of "the value of PPD", so the larger the PPD, the more pixels filled in the picture of the unit area in the visual field of the human eye, the clearer the user's perception of the displayed picture.A doubling of PPD means that the number of filled pixels in the same field of view increases by four times.
PPD calculation equation:
(Line segment ab: number of pixels with diameter of monocular imaging circumscribed circle; FOV: field angle)
The formula for calculating the number of pixels in the area with an average 1 ° field angle FOV is as follows:
SPI
Scanning resolution refers to the resolution set before scanning an image. It affects the quality and performance of the generated image file and determines how the image will be displayed or printed.If the scanned image is used for 640 × 480 pixel screen display, the scanning resolution need not be greater than the device resolution of the general display screen.
In most cases, images are scanned to output images using high-resolution devices.If the image scanning resolution is too low, the output effect will be very rough.If the scanning resolution is too high, the digital image will produce more information than is needed for printing, which will not only slow down the printing speed, but also cause excessive loss of image tone during printing.Generally, the image resolution should be twice the screen resolution, which is the standard adopted by most output centers and printing plants in China.However, in fact, the image resolution should be 1.5 times of the screen resolution. The specific situation varies from image to image.[4]
LPI
Screen Resolution (ScreenResolution), also known as screen frequency (a printing term), refers to the number of screen lines per inch (that is, the number of hanging screen lines) of the screen used for printing images, expressed in (LPI). For example, 150LPI refers to 150 screen lines per inch.[4]
DPI
Device Resolution, also known as output resolution, refers to the number of points per inch that can be generated by various output devices (such as displays, inkjet printers, laser printers, and plotters).This resolution is measured by DPI. The device resolution of PC display is between 60 and 120 DPI, and the resolution of printing device is between 360 and 2400 DPI.[4]
Bit resolution
Bit resolution, also called bit depth, is used to measure the number of bits of information stored in each pixel.This resolution can mark the number of color levels. The common ones are 8-bit, 16 bit, 24 bit or 32-bit colors. Sometimes, bit resolution is also called color depth.The so-called "bit" actually refers to the square degree of "2". 8 bits is the octave of 2, that is, the multiplication of 8 2 equals 256.An 8-bit color depth image can represent 256 levels of color.[4]
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Display resolution[5]
Display resolution refers to the physical resolution of the computer display itself.Display resolution refers to phosphor dots on the screen for CRT display;For LCD display, it refers to the pixels on the display, which are processed during production [5].The display resolution is usually expressed in the form of "horizontal pixels × vertical pixels", such as 800 × 6001024 × 7681280 × 1024, etc., and can also be expressed in specification codes, such as VGA, XGA, SXGA, etc.The resolution supported by traditional CRT displays is more flexible, while the pixel spacing of LCD displays is fixed, so the supported display modes are not as many as CRT displays.
The best resolution of LCD display is also called the maximum resolution, under which the LCD display can display the best image.In the past, the dpi value representing the resolution of the display was not marked when the display was delivered from the factory, but only the dot pitch was given. From the dot pitch, the dpi value of the resolution of the display can be calculated, and then the maximum display mode that the display can support can be calculated.Modern LCD displays also show the best resolution. The best resolution for 15 inch LCDs is 1024 × 768. The best resolution for 17~19 inch LCDs is usually 1280 × 1024. Larger LCDs have a larger optimal resolution.
Screen resolution
Screen resolution (display resolution) refers to the precision of the screen image, which represents how many pixels the display can display.Since the dots, lines and planes on the screen are all composed of pixels, the more pixels the display can display, the finer the picture will be, and the more information can be displayed in the screen area.Think of the whole image as a large chessboard, and the resolution is expressed as the number of intersections of all longitude and latitude lines.When the display resolution is fixed, the smaller the display screen, the clearer the image will be. On the contrary, when the display screen size is fixed, the higher the display resolution, the clearer the image will be.The screen resolution must be less than or equal to the display resolution, which describes the number of pixels of the display itself and is inherent and unalterable.
Image resolution[5]
Image resolution refers to the resolution of a digital image saved and displayed in the computer, which represents the number of points in the length and width of the image. It has a direct relationship with the pixels of the image.For example, a picture with a resolution of 640 × 480 pixels has a resolution of 307200 pixels, or 300000 pixels;A picture with a resolution of 1600 × 1200 has 2 million pixels.
The image resolution determines the image quality.For an image of the same size, if the image resolution is higher, the number of image pixels that make up the image is more, the pixel points are smaller, and the image is clearer and more realistic.For example, the 1-inch × 1-inch image with 72dpi resolution contains 5184 pixels, while the 1-inch × 1-inch image with 300dpi resolution contains 90000 pixels.
Image resolution and display resolution are two different concepts: display resolution is used to determine the area size of the displayed image, and image resolution is used to determine the number of pixels that compose an image.For example, on a display screen with a resolution of 1024 × 768, an image with a resolution of 320 × 240 accounts for about 1/12 of the display screen, while an image with a resolution of 2400 × 3000 cannot be fully displayed on this display screen.For images with the same image resolution, the lower the screen resolution (such as 800 × 600), the larger the image looks, but the fewer items are displayed on the screen;The higher the screen resolution (e.g. 1024 × 768), the smaller the image looks.
Scanner resolution[5]
The scanner resolution needs to be determined from three aspects: the optical part, the hardware part and the software part. The scanner resolution is equal to the resolution of its optical parts plus the resolution obtained by its own processing and analysis through hardware and software.The optical resolution is the actual number of light points that can be captured by the scanner's optical components within each square inch area, that is, the physical resolution of the scanner's CCD, which is also the true resolution of the scanner.The optical resolution is the value obtained by dividing the pixels of the CCD by the maximum horizontal scanning size of the scanner.
The resolution of the optical part of the scanner with a resolution of 1200DPI only accounts for 400-600DPI. The resolution of the expansion part is generated by analyzing the image and scientifically filling the blank part (generated by hardware and software, this process is also called "interpolation" processing).Optical scanning and output are one-to-one. After the optical scanning output is processed by computer software and hardware, the output image will become more realistic and the resolution will be higher.Most scanners sold on the market have software and hardware expansion functions for resolution.For example, the resolution of a scanner is up to 4800DPI (this 4800DPI is the sum of optical resolution and software difference processing), which means that when the scanner is used to input an image, 4800 × 4800 pixels can be collected on a scanning format of 1 square inch, that is, a scanning area of 1 inch square. The image size generated after scanning with a resolution of 4800DPI is 4800Pixel × 4800Pixel.When scanning images, the higher the scanning resolution is set, the finer the image effect is generated, and the larger the image file is generated, but the more interpolation components are[6]。
Digital camera resolution[6]
The resolution of the digital camera determines the size of the final output high-quality picture of the captured image, or the size of the picture that can be displayed on the computer display.The resolution of a digital camera depends on the pixels on the CCD (Charge Coupled Device) chip in the camera. The more pixels, the higher the resolution.The maximum resolution of a digital camera is also determined by its production process. Users can adjust to a lower resolution to reduce the space occupied by photos.For similar digital cameras, the higher the maximum resolution, the higher the camera grade.High resolution cameras generate large data files, which have high requirements on the speed of processing and processing computers, the capacity of memory and hard disk, and the corresponding software[6]。
The height of the digital camera pixel level and the final size of the photos that can be printed with a certain resolution can be simply calculated by the following method: assuming the resolution of the color printer is N DPI, the horizontal pixel of the digital camera is M, then the maximum photos that can be printed are M ÷ N inches.If the resolution of the printer is 300DPI, the maximum size of the image file taken by the digital camera with 3600 horizontal pixels can be printed without interpolation processing is 12 inches (3600 ÷ 300).To print digital photos with larger size, a digital camera with higher pixel level is required.In addition, the method of calculating the display size is the same as that of calculating the print size[6]。
