Ham radio enthusiasts from throughout the region were at the Polk County Fairgrounds on Saturday, drawn by the lure of the semi-annual swap meet.

For some, ham radio is a hobby. Hams tends to use two kinds of gear: HF and VHF/UHF. HF gear is made to talk over long distances, while VHF/UHF radio is for talking around town. But for Kjell Lindgren, it was an out-of-this-world experience.

Ham radios work when other forms of communication don't. "(That's) huge, especially with the first one (Helene) that went through North Carolina. You could listen on the radio. They were able to facilitate getting aid to a lot of people,” said Josh Scott, Yamhill County Amateur Radio Emergency Services Group. “And in those events, there were people getting on their radio that weren't licensed. But they were still able to get on the Frs two way radio and ask for help.”

Oregon isn't home to major hurricanes. But local residents have their own worries. Fires, for example, and a ticking time bomb off the coast.

“If the Cascadia earthquake were to hit, the reality is that we will probably not have cell phones or telephones of any sort. The Internet will be down,”Scott said. "The only way you're going to be able to communicate after Cascadia is with radios.”

“Ham radios used to be more popular. Most of the people in their 70s and 80s were part of ham radio clubs and got their licenses. This was in almost every school,” she said. “Now, there’s a lot less of that going on. It’s a great hobby. But it’s going to be very valuable when the big one hits.”

The environment of an electron microscopy lab does not directly impact the electron microscope itself but rather affects the imaging quality and overall performance of the microscope. During the operation of an electron microscope, the fine electron beam needs to travel in a high vacuum environment, covering a distance of 0.7 meters (for Scanning Electron Microscope) to over 2 meters (for Transmission Electron Microscope). Along the path, external factors such as magnetic fields, ground vibrations, noise in the air, and airflows can cause the electron beam to deviate from its intended path, leading to a degradation in imaging quality. Therefore, specific requirements need to be met for the surrounding environment.

As is well known, electromagnetic waves consist of alternating magnetic and electric fields. However, it is important to consider the frequency when measuring electromagnetic waves using either magnetic or electric fields. In practice, it is necessary to take the frequency into account.

At very low frequencies (as the frequency tends to zero, equivalent to a DC magnetic field), the magnetic component of the electromagnetic wave becomes stronger while the electric component weakens. As the frequency increases, the electric component strengthens and the magnetic component decreases. This is a gradual transition without a distinct turning point. Generally, from zero to a few kilohertz, the magnetic field component can be well characterized, and units such as Gauss or Tesla are used to measure the field strength. Above 100 kHz, the electric field component is better measured, and the unit used for field strength is volts per meter (V/m). When dealing with a low-frequency electromagnetic environment with a strong magnetic field component, reducing the magnetic field directly is an effective approach.

Next, we will focus on the practical application of shielding a low-frequency (0-300 Hz), electromagnetic field with a magnetic field strength ranging from 0.5 to 50 milligauss (peak-to-peak) in a shielded volume of 40-120 cubic meters. Considering cost-effectiveness, the shielding material used is typically low-carbon steel plate Q195 (formerly known as A3).

Since the eddy current loss of a single thick material is greater than that of multiple thin layers (with the same total thickness), thicker single-layer materials are preferred unless there are specific requirements. Let's establish a mathematical model:

1. Derivation of the formula

Since the energy of low-frequency electromagnetic waves is mainly composed of magnetic field energy, we can use high-permeability materials to provide magnetic bypass paths to reduce the magnetic flux density inside the shielding volume. By applying the analysis method of parallel shunt circuits, we can derive the calculation formula for the parallel shunting of magnetic flux paths.

Here are some definitions:

Ho: External magnetic field strength

Hi: Magnetic field strength inside the shielding volume

Hs: Magnetic field strength inside the shielding material

A: Area through which magnetic lines pass through the shield A = L × W

Φo: Permeability of air

Φs: Permeability of the shielding material

Ro: Magnetic resistance of the internal space of the shield

Rs: Magnetic resistance of the shielding material

L: Length of the shielding volume

W: Width of the shielding volume

h: Height of the shielding volume (i.e., length of the magnetic channel)

b: Thickness of the shielding material

From the schematic diagram (Figure 1), we can obtain the following equations:

Ro = h / (A × Φo) = h / (L × W × Φo) (1)

Rs = h / ((2b × W) + (2b × L)) × Φs (2)

From the equivalent circuit diagram (Figure 2), we can obtain the following equation:

Rs = Hi × Ro / (Ho - Hi) (3)

By substituting equations (1) and (2) into equation (3) and rearranging, we get the formula (4) for calculating the thickness b of the shielding material:

b = L × W × Φo × (Ho - Hi) / ((W + L) × 2Φs × Hi) (4)

Note:

In equation (4), the length of the magnetic channel h is eliminated during the simplification process, and physical units such as Φo, Φs, Ho, Hi, and others are also eliminated. It is only necessary to ensure that the length units are consistent.

From equation (4), it can be seen that the shielding effectiveness is related to the permeability and thickness of the shielding material, as well as the size of the shielding volume. A higher permeability and thicker shielding material result in lower magnetic resistance and higher eddy current losses, leading to better shielding effectiveness. When the permeability and thickness are the same, a larger shielding volume will result in poorer shielding performance.

2. Validation of the formula

We can use equation (4) Φo=1, L=5m, W=4m, Φs=4000 to calculate the thickness of the shielding material and compare the calculated results with experimental data (which took several months to collect):

Table 1

Note:

1. The external magnetic field strength is in the range of 5-20 milligauss (peak-to-peak).

2. The measured values are obtained by converting multiple tests under different conditions. Since the test conditions for each measurement are not the same, the presented values represent approximate average measurements.

In reality, due to various factors, it is quite challenging to establish a simple mathematical model for analyzing and calculating low-frequency electromagnetic shielding effectiveness. The significant deviations between the calculated results and experimental data can be attributed to the following reasons.

Firstly, the function relationship in the parallel shunt circuit is linear, while in magnetic circuits, permeability, magnetic flux density, and eddy current losses do not exhibit linear relationships. Many parameters are nonlinear functions of each other (although they may exhibit good linearity in certain ranges). During the derivation of the parallel shunting mechanism in magnetic circuits, some parameters were omitted, approximations were made, and conditions were simplified to avoid complex calculations, linearizing the magnetic circuit. These factors are the main reasons for the differences in precision between calculations and experiments.

Secondly, commercial low-carbon steel plate specifications are usually 1.22m × 2.44m in size. Considering a room size of 5m × 4m × 3m as an example, even with full welding, there would still be over 50 welds, and the thickness of the welds is often smaller than that of the steel plate. Additionally, there may be openings and gaps in the shielding material, resulting in an overall increase in magnetic resistance and a decrease in permeability. Therefore, the calculation formula for magnetic shielding derived from the parallel shunt circuit needs to be modified to approach actual conditions.

3. Modified calculation formula

Based on equation (4), we introduce a correction coefficient μ and consider the permeability of air to be approximately 1. The modified equation for calculating the thickness b of the shielding material is as follows (equation 5):

b = μ × [L × W × (Ho - Hi) / ((W + L) × 2Φs × Hi)] (5)

The value of μ is selected between 3.2 and 4.0. A smaller value is preferred for smaller shielding volumes and higher process levels, while a larger value is better for larger shielding volumes. Using equation (5) with μ = 3.4, the calculated results are compared with experimental data (see Table 2), showing significantly improved agreement.

Table 2

Note: Other conditions remain the same as in Table 1.

It should be noted that multiple test data confirm the high concurrence between the results obtained from equation (5) and various on-site measurements. However, there have been isolated cases with significant deviations. These cases can be attributed to construction issues.

The following are several situations that may occur during construction: 

1. Thin steel plates used in individual areas (such as doors).

2. Non-continuous welding or large gaps in welded joints.

3. Insufficient depth of welds, resulting in decreased permeability at weld locations and multiple "bottlenecks."

4. Larger openings in shielded areas and improper treatment of waveguide openings.

5. Arbitrary shortening of waveguide length or substandard processing.

6. Insufficient wall thickness of waveguide.

7. Multiple grounding points in the shielding material lead to non-uniform current distribution.

8. Connection of the shielding material to the neutral wire of the power supply.

Even a small oversight can lead to a significant deterioration in effectiveness, the capacity of a bucket depends on the shortest piece of wood. For concealed projects like this, quality is often ensured by the craftsmanship. Therefore, it is important to pay careful attention to selecting a reliable construction company, strictly adhering to the design requirements and process, strengthening on-site construction supervision, and implementing phased inspections.

Shielding enclosure aperture design:

When designing a shielding enclosure, one will inevitably encounter the issue of apertures. The theoretical methods commonly used for aperture design are difficult to directly apply to low-frequency magnetic shielding design. Here, we will discuss the example of a room's shielding design.

1. Small apertures: In rooms with small shielded devices, there are usually power supply, energy supply, and cooling water requirements. These auxiliary facilities are mostly located outside the shielding enclosure and are connected through water pipes, air pipes, and cables. These pipes and cables can be appropriately centralized and passed through the shielding enclosure using one or several small holes. These holes, made of the same material as the shielding enclosure, are called "waveguide openings." The length-to-diameter ratio of the waveguide openings is generally considered to be at least 3-4:1 (if the on-site conditions permit, longer is better). For example, if the diameter of a small hole is 80mm, the length should be at least 240-320mm.

2. Medium-sized apertures: Ventilation openings for air conditioning and exhaust openings for fans typically have diameters (or side lengths for squares or rectangles) of around 400-600mm. Calculating the length of a waveguide opening based on these dimensions would result in lengths of 1200-2400mm, which is not feasible in practical construction. In this case, the original aperture can be divided into several smaller openings of the same size using a grid. For example, if a 400×400mm air inlet is divided into nine equal-sized grids, the length would be reduced from 1200-1600mm to 400-530mm (the increase in airflow resistance due to the grids is negligible).

When designing and fabricating, pay attention to the following points:

- The material of the grids should be the same as the shielding enclosure, and the thickness of the material should not be arbitrarily reduced.

- The cross-section of the grids should be as close to square as possible.

- Try to reduce the number of grids as much as possible, within acceptable lengths, to reduce processing difficulties and airflow resistance.

- Ensure continuous welding at all locations of the grids to prevent an increase in magnetic resistance.

- Increase the magnetic permeability by adding silicon steel plates at the junctions of the grids.

3. Large closable apertures: Doors and windows of a room typically have openings measuring 1m×2m or even larger. In this case, the waveguide openings should be designed based on the non-magnetic gaps when the doors and windows are closed (made of the same material as the shielding enclosure). Assuming a non-magnetic gap of 5mm (which is not technically challenging, and additional edge folds can be added in difficult-to-handle areas), the length of the waveguide opening should be 15-20mm. Given that the gap is narrow and long, it is preferable to have a longer length. Note that the waveguide openings are not only formed by the frames of doors and windows; there should be a certain thickness of edge folds at all non-magnetic gap locations to ensure the length of the waveguide opening. To ensure safe evacuation in special circumstances, the door frames of the shielding room should be reinforced, and the shielding doors should open outward.

Here is a practical design example:

The dimensions of the room are length 5m, width 4m, and height 3.3m, with original magnetic field strengths of x=10mGauss, y=8mGauss, and z=12mGauss. The goal is to design a low-frequency electromagnetic shielding that ensures the magnetic field strength in any direction inside the enclosure is less than 2mGauss. See Figure 3.

1. Select commercial low-carbon steel plates with Φs=4000 and specifications of 1.22m×2.44m.

2. Use equation (5) to calculate the thickness of the steel plates from the x, y, and z directions:

Taking μ as 3.8, substitute the given length, width, and height into L×W, corresponding to the original magnetic field strengths in the x, y, and z directions.

bx=3.8〔3.3m×4m×(10mGauss -2mGauss)/(4m+3.3m) 2×4000×2mGauss〕

=3.43mm

by=3.8〔3.3m×5m×(8mGauss -2mGauss)/(5m+3.3m) 2×4000×2mGauss〕

=2.83mm

bz=3.8〔5m×4m×(12mGauss -2mGauss)/(4m+5m) 2×4000×2mGauss〕

=5.28mm   (If lengths and widths are 10m and 6m, respectively, the calculated thickness would be b=2280/56000=8.91mm)

The thickness of all steel plates should be at least 6mm (to allow for environmental magnetic field variations, 8-10mm can be used as well) as a single layer.

All welding seams should be continuous and try to achieve a depth close to the thickness of the base material.

3. Waveguide opening treatment

(Omitted. See the section on shielding enclosure aperture design).

After completion, the shielding enclosure was tested and fully met the design requirements.

Note: Magnetic shielding cannot improve DC interference environments. When there is a need to improve DC electromagnetic interference environments, it should be used in conjunction with demagnetizers that have DC elimination capabilities.

Do police have portable fingerprint scanners?

Yes, portable fingerprint scanners are used by law enforcement agencies in many countries. These devices allow the police to quickly capture and analyze fingerprints in the field without the need to transport the individuals to a police station or a dedicated fingerprinting facility. Portable fingerprint scanners are compact, lightweight devices that can scan and analyze fingerprints using optical or capacitive technology.

These scanners typically work by capturing an image of the ridges and valleys on a person's fingertip and converting it into a digital format. The image is then compared against a database of known fingerprints to identify if there is a match. Portable fingerprint scanners are beneficial for on-site identification and verification purposes, aiding in crime scene investigations, suspect identification, and rapid checks of individuals' identities during field operations.

In an era of rapid technological advancement, law enforcement agencies are increasingly turning to innovative tools to improve operational efficiency. One such advancement is the use of portable fingerprint biometric scanners. But do police have portable fingerprint scanners? The answer is yes, and the SFT Portable Android Fingerprint Scanner leads the way.

The SFT Biometric Fingerprint POS is not an ordinary fingerprint scanner; It is EMV/PCI certified and FBI certified, ensuring it meets the highest standards of security and reliability. This portable device allows officers to quickly and accurately identify people on scene, making it a valuable tool for law enforcement. With its built-in fast receipt printer, officers can provide immediate documentation of investigation results, which is critical to maintaining accurate records during an investigation.

In addition, SFT scanners are equipped with GPS capabilities, allowing officers to record the exact location of their interactions. This feature is particularly useful for tracking crime patterns and ensuring accountability of police actions. The device also supports 4G network connectivity and can transmit data to a central database in real time. This means officers can obtain vital information about a suspect or missing person without having to return to the police station, significantly speeding up the investigation process.

As crime rates fluctuate and the need for rapid identification grows, it becomes increasingly important to integrate portable fingerprint scanners such as the SFT model into police work. Not only do these devices increase law enforcement efficiency, they also improve public safety by responding to incidents faster.

The answer to whether police have portable fingerprint scanners is clear. With advanced technologies like the SFT Portable Android Fingerprint Scanner, law enforcement agencies can better serve and protect their communities. The future of policing is here, and it's portable.

LED Display, we could simply recognize it as a big size monitor, which is always widely used for commercial applications. It also be named as led screen, led video wall, led display panel, led display billboard etc.,

Light emitting diode, driving ICs and other electronic components  mounted together on current PCB board forms LED display modules; LED modules, switching power supplies and control cards fixed on specialized metal  cabinet forms led display cabinet; several led display cabinets fixed on specialized metal structure and worked with specialized control system; this is the whole led display system.

As it is said, led display is always widely used for commercial application. Main applications would be stage rental, VP virtual production, XR virtual photo shoot, exhibition, creative shape display, advertisement & media, security monitoring, commanding & controlling, transports, meeting room, education, stadium, broadcasting, smart city creation, finance, communication , estate, medical, meteorology, military etc., Advertisement, information display, specific places decoration, and stage background are main usage for led display application. The most common applications we will see would be led displays on the wall of buildings, led displays of cinema stage back ground, led display on evet stage, and led displays in night club...

LED display screens are classified into different categories based on various criteria. Initially, there were several classification methods, which included:
1. Installation Scene: Indoor LED display screens and outdoor LED display screens.
2. LED Encapsulation Type: DIP LED display screens, SMD LED display screens, and dot matrix LED display screens.
3. Display Color: Single color LED display screens, dual color LED display screens, and full-color LED display screens.
4. Pixel Pitch: This classification refers to the commonly heard "P" number for LED display screens. Popular pixel pitch of display screens now ranges from less than 1 millimeters to 10 millimeters.

With the continuous advancement of LED display screen technology and its increasing application scenarios, the classification of LED display screens has become more detailed. One notable example is rental LED display screens. In the beginning, rental LED display screens were primarily achieved by reducing the weight of indoor and outdoor screen bodies and equipping them with corresponding fast locks, without significant changes in appearance and size. However, as the technology of various components in the LED display screen supply chain has improved, the current rental cabinets can achieve both aesthetic appeal and lightweight design, truly meeting the requirements of quick assembly, disassembly, and easy transportation.

Currently, the most popular LED display screens in the market include small pixel pitch LED display screens, GOB LED display screens, COB LED display screens, and creative LED display screens. These advancements have revolutionized the visual experience and expanded the possibilities of LED display screens.

Choose the right LED display screen for your needs and elevate the impact of your presentations, advertisements, and visual displays. Experience the impressive capabilities of LED display screens and unlock a world of vibrant and dynamic visuals.

1. Environmental Resistance: Outdoor LCD digital signage is designed to withstand harsh weather conditions such as rain, sunlight, temperature extremes, and dust. They have higher IP ratings for protection and special coatings to reduce glare and ensure visibility in bright outdoor environments. Indoor signage, on the other hand, is not built to handle such extreme conditions.
2. Brightness and Visibility: Outdoor signage requires higher brightness levels to be visible in direct sunlight. They typically have much brighter screens, often several times brighter than indoor models. Indoor signage has lower brightness as the lighting conditions indoors are usually more controlled.
3. Temperature Tolerance: Outdoor units have better heat dissipation and can operate within a wider temperature range to cope with hot summers and cold winters. Indoor units are designed for more stable and moderate temperature environments.
4. Durability and Construction: Outdoor digital signage is made of more robust materials and has better sealing to prevent damage from moisture and debris. The casing is often more rugged and vandal-resistant.
5. Cost: Due to the enhanced features and durability requirements, outdoor LCD digital signage tends to be more expensive than indoor counterparts.

LCD and LED Basics

Liquid crystal displays have been a cornerstone in the world of visual displays for decades. The principle behind LCD technology involves liquid crystals sandwiched between two transparent electrodes. When you subject these liquid crystals to an electric current, they align to control the passage of light through the display.

Traditional LCD screens use cold cathode fluorescent lamps (CCFLs) behind the screen for illumination. These lamps serve as the light source, emitting light that passes through the liquid crystal layer to create images. People use LCDs extensively in electronics such as computer monitors and televisions.

LED stands for light-emitting diode. Unlike LCDs, LEDs utilize an array of semiconductor light-emitting diodes to produce light. Each diode emits its own light when a current passes through it, eliminating the need for a separate light source, such as CCFLs.

LCD vs. LED: 8 Key Differences

LEDs offer several advantages over traditional LCDs.

They consume less power, provide higher brightness levels and have superior contrast ratios. LED technology also enables thinner displays with better picture quality, compared to their LCD counterparts. It's no wonder LED displays have gradually become the preferred choice for consumers and TV manufacturers alike.

Here's how the two displays stack up against each other in the most important categories of comparison.

1. Light Source

LCD monitors and TVs typically utilize cold cathode fluorescent lamp backlighting technology. These lamps provide the light source necessary to illuminate the LCD panel.

In contrast, LED monitors and TVs employ LED backlighting. LEDs serve as the light source, offering better efficiency and control over the brightness, compared to CCFLs.

2. Energy Efficiency

LED displays are known for their superior energy efficiency, compared to LCDs. LED backlighting consumes less power, resulting in lower energy bills and reduced environmental impact.

LED monitors and TVs are designed to produce light directly, minimizing the wasted energy you might typically associate with CCFL backlighting in LCD displays.

3. Picture Quality

When it comes to image quality, LED displays often outperform LCDs. LED screens offer higher brightness levels, deeper contrast ratios and more vibrant colors.

The use of LED backlighting enables better control over individual pixels, resulting in sharper images. LED panels also tend to have wider color gamuts, which also enhances the overall image quality.

4. Thinness

One significant advantage of LED displays is their thinness. LED monitors and LED televisions can achieve sleek and slim designs, due to the compact nature of the LED backlighting technology.

In contrast, LCD monitors and TVs may be thicker, especially those using CCFL backlighting, which requires additional space.

5. Local Dimming

LED displays often incorporate local dimming technology to enhance the contrast and black levels. This feature can dynamically adjust the brightness of specific areas of the screen, resulting in deeper blacks and a better overall picture quality.

While some high-end LCD televisions may also offer local dimming, LED displays are generally better in this category.

6. Viewing Angle

While modern LCD panels have improved viewing angles (compared to earlier models), they may still exhibit color distortion or reduced brightness when you view them from extreme angles, which can make for a frustrating viewing experience.

On the other hand, LED backlighting technology provides more uniform illumination across the entire screen in LED monitors and TVs. This helps to maintain consistent image quality across a wider viewing angle, such as when you're viewing the screen from an off-center position.

7. Cost

While LED displays tend to offer better performance, they also tend to come with a higher price tag compared to traditional LCDs. The advanced technology and materials in LED backlighting contribute to the higher price tag.

However, over time, the energy savings and longevity of LED displays may offset your initial investment.

8. Longevity

LED TVs last longer with a lifespan of around 100,000 hours. On the other hand, LCD TVs have a lifespan of about half that, or 50,000 hours. This can make an LED display a worthwhile investment if you're looking for an option that will last you as long as possible.

More Practical Applications of LED and LCD Displays

In addition to their use in televisions and computer monitors, LED and LCD displays are in use across other industries and settings.

Signage and Video Walls

Both LED and LCD displays are common in digital signage applications in indoor environments, such as retail stores, airports and corporate offices, where space constraints and controlled lighting conditions are present.

LED displays are suitable for both indoor and outdoor uses, due to their high brightness levels, wider viewing angles and durability in various weather conditions.

You can utilize both LED and LCD displays for video walls. A video wall consists of multiple display panels arranged seamlessly to create a larger display area. They're popular in command centers, entertainment venues and corporate lobbies.

Gaming

LED and LCD displays are also integral components of gaming consoles and gaming laptops. Some gamers favor LCD monitors with fast response times and high refresh rates for smoother gameplay and reduced motion blur. Meanwhile, LED-backlit displays enhance visual clarity, color accuracy and contrast, contributing to a more immersive gaming experience.

What Is an OLED Display?

In research LCD and LED displays, you might also come across what's called an OLED display. An organic light-emitting diode display is a type of display technology that utilizes organic compounds to emit light when an electric current is applied.

Unlike traditional LED and LCD displays, which require backlighting to illuminate the screen, OLED displays produce their own light on a pixel-by-pixel basis.

The structure of an OLED display consists of several organic layers sandwiched between two conductors. When an electric current passes through these organic layers, it stimulates the emission of light. Organic LED displays are made up of individual OLED pixels, each capable of emitting its own light and producing colors independently.

One of the key advantages of OLED displays is their ability to achieve true blacks and infinite contrast ratios. Since you can turn off OLED pixels completely to display black, OLED screens can achieve deeper blacks and higher contrast levels — compared to LCD and LED displays, which rely on backlighting.

OLED displays also offer a wider viewing angle, faster response times and better color accuracy compared to traditional display technologies. On the downside, OLED displays are susceptible to burn-in and have higher manufacturing costs compared to LCD displays.

However, advancements in OLED technology continue to address these challenges, making OLED displays increasingly popular in consumer electronics, including smartphones, televisions, computer monitors and automotive displays.

What Are Quantum Dots?

To better understand color performance and image quality in both LED and LCD displays, you'll want to become familiar with quantum dots, the semiconductor nanocrystals that have gained significant attention in the display industry, due to their ability to enhance the performance of both LED and LCD displays.

Quantum dots are primarily a backlighting technology in displays, serving to improve the color accuracy, brightness and energy efficiency in LEDs and LCDs, making them more competitive with other display technologies, such as OLED.

Quantum dot technology has become increasingly prevalent in high-end displays, including premium LED TVs and LCD monitors, offering consumers a more immersive viewing experience.

In LED displays, quantum dots are a color conversion layer in conjunction with blue LEDs. Blue LEDs are the primary light source, and quantum dots convert some of the blue light into red and green wavelengths, thus creating a broader spectrum of colors.

This process, known as photoluminescence, allows LED displays to achieve a wider color gamut and more accurate colors, resulting in richer images.

In LCD displays, quantum dots are part of a technology called quantum dot enhancement film (QDEF). QDEF is a thin film containing quantum dots that manufacturers place between the backlight source and the LCD panel.

The quantum dots in QDEF absorb blue light from the LED backlight and re-emit it as pure red and green light. This process enables LCD displays to produce a wider color range and higher color saturation, approaching the performance of OLED displays in terms of color reproduction.

Digital signage refers to LED, LCD, or OLED screens that showcase dynamic material, including text, graphics, video, interactive media, and live-streaming content via software that facilitates it all.

These versatile displays are a common sight in outdoor public spaces, serving as high impact billboards in iconic locations such as Times Square. Their indoor applications are equally diverse, enhancing customer experience and communication in retail spaces, restaurants, modern office buildings, healthcare facilities, transport hubs, and educational and religious institutions

A standout advantage of signage technology is its operational efficiency, particularly in content management and playback. Unlike traditional signage, electronic signs eliminate the need for printing, enabling instantaneous content updates and allowing for timely and relevant communication with audiences.

Most modern signage networks are controlled using using software that offers the ease of maintenance. This often comes these software applications come equipped with media design toolset. That means, one can create, publish and manage all of their on-screen messaging from one single platform.

What is a digital signage system?

From the above definition, it is clear that digital signage is any screen that we use for specific information to a target group

But, these screens are not the sole component; there is a particular technology working at the backdrop. That is why we often refer to the entire technology as a 'digital signage system.'

A digital signage system is a network of displays powered by software that enables the creation, management, and playback of multimedia content for advertising or informational purposes. These systems are commonly used in public spaces and commercial environments to engage and inform viewers.

There are three primary components of this system:

1. The hardware
2. The software or Content Management System (CMS)
3. The content

LED displays promise to change the way movie and television productions are created, but the effects are only as good as the video walls on which they’re shown. Those displays are constantly improving. Just a few decades ago the pixel pitch, or the distance between individual pixels in an LED display, was in the range of 12 mm, making them suitable primarily for viewing from a distance. Today, the pixel pitch of some displays is in the range of .6 mm or smaller, making them comparable in resolution to an LCD display. Although that shrinking pixel pitch has greatly improved the resolution of the displays it does create challenges that need to be overcome to make them suitable for video applications. Concerns that need to be addressed when using LED displays in video productions include:

Brightness

Adjustable screen brightness For different scenarios, the brightness of screen is needed to adjust to meet requirements.

Refresh rate

Refresh rate at high brightness – According to the “10 times refresh” theory, the refresh rate for high brightness LED displays needs to be more than 10 times the camera shutter speed for images taken by the camera to be free of lines and defects. A typical camera has a shutter speed of about 1/200 second, so the refresh rate of an LED display in a broadcast application needs to be greater than 2,000Hz or bright lines will appear in the image.

Most fine-pitch LED displays today use PWM-based driver chips, which have the characteristics that the refresh rate at low-grayscale levels is lower than that at high-grayscale levels. As a result, when showing a low-grayscale image on the LED screen black streaks appear on the picture taken by the camera, greatly affecting the visual experience.

Grayscale

The loss and discontinuity of pixel data at low grayscale levels greatly reduces the smoothness of images, causing them to appear unclear to viewers. There are two causes of this problem. The first is that the grayscale data of the video source is compressed. This leads to a loss of a certain amount of grayscale and is likely to cause blocky images. The second is that the grayscale output bit number of the LED display is too low. Therefore, the jump span of each level at low grayscale is too large, thereby causing discontinuity.

HDR

If the LED display has a higher grayscale output, such as 16-bits, it can decrease discontinuity problems and lead to a better visual performance. Viewers can see more details, especially under low brightness conditions. In addition, when the video source is HDR, an LED displays would perform better with 16-bit grayscale output and a higher refresh rate. This kind of opulent image quality will bring a photorealistic performance making it well suited for movie backdrop use.

Contrast

Insufficient contrast causes a loss of image detail and results in images without multiple layers, similar to a painting without depth and color.

Moire

Moiré patterns are large-scale interference patterns that can be produced in an image when an opaque ruled pattern with transparent gaps is overlaid on another similar (but not identical) pattern.

LED displays are notorious for using a great deal of energy and generating a large amount of heat that can drive up costs and shorten display life.

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View Distance

The image perception is influenced by the distance between the viewer and the LED screen. The ideal viewing distance is 1x ~1.5x the pixel pitch in meters. So in a 12 mm pixel pitch screen it is around 12 meters. At this distance the human eye (or brain) no longer sees individual pixels but the whole picture. Of course you can get closer (and certainly further away) watching the screen. Closer to the screen the pixels will become increasingly evident, but the image will no long remain acceptable.

The viewing angles for an LED displays are measured horizontally and vertically, and indicate over what range images on the LED screen are fully visible without the screen displaying a negative image.The viewing angle of a LED display represents the limit of its optimal picture quality. Sit at a position at a wider angle than that of its viewing angle and you will experience worse picture.

The LED industry defines viewing angle as the full angle at which brightness is half of the brightness from dead center. (The view angle of a screen is by convention the angle within which the brightness of a display is equal to the 50% of the frontal luminosity.).More scientifically, if ø (angle theta) is the angle from off center (0°) where the LED’s brightness is half, then 2ø is defined as the full viewing angle.

For example, a LED screen with 5000 NIT frontal brightness has a visibility angle equal to the angle by which the brightness is reduced to 2500 NIT. This visibility angle can vary depending on the LED and the technical features of the display.

In conclusion, it can be stated that loss of brightness under viewing angle start with radiation characteristics of individual LEDs. In most cases radiation characteristics of LEDs show 50% brightness level at about 60°.

If the viewing angle of the LED screen becomes lower, the LED screen brightness will be higher, or vice versa. If the contrast ratio between LED screen's brightness and environmental brightness is higher, the led screens’ showing performance will be more colorful. But a too high brightness will consume a lot of energy and create high heat. For that the LED's brightness decreases much faster, and of course, its lifespan will become shorter.

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