Laser collimation

If you are satisfied with the results of the test, you can go ahead and buy the monitor. If not, we advise you to keep looking.

If you are using an HDMI cable for connecting to your display, it is advised to shift to a display port as it offers better video quality when compared to HDMI.

In addition, you can also look at the connectors on the two ends, and if they show signs of corrosion or are damaged in some way, it's best to replace the cable itself.

Try the model featured throughout this blog post yourself by clicking the button below, which will take you to the Application Gallery:

We have taken the example of a monitor with a 60-hertz refresh rate, and as the refresh rate goes up, the response time of the liquid crystals plays a more crucial role. Therefore, ghosting can increase if you have a monitor with a high refresh rate.

A nonzero scattering coefficient, \sigma_s, can be added to the absorption coefficient used within the Radiative Beam in Absorbing Media interface, so we can write \kappa_{tot} = \kappa + \sigma_s. The absorbed energy can now be decomposed in the absorbed fraction, \kappa/\kappa_{tot}, and the scattered fraction, \sigma_s/\kappa_{tot} .

You see, your GPU/CPU is responsible for creating the visuals you see on your screen. Once created, the CPU/GPU sends this information to your monitor based on its refresh rate. The monitor then collects the information and displays the visuals on the screen.

Collimatedbeam

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It should be noted that essentially all real materials exhibit some degree of anisotropic scattering, meaning that light is preferentially redirected into certain directions. However, in some applications, the scattering can be approximated as isotropic, and that is the case we will address here. We will consider a ray of collimated light, a laser beam, incident upon a material, where an isotropic scattering coefficient and isotropic absorption coefficient quantify the change in the light intensity.

To implement such a model within COMSOL Multiphysics®, we can use a combination of the Radiative Beam in Absorbing Media interface and the Radiation in Absorbing-Scattering Media interface. The former interface only needs be solved for in a subdomain surrounding the path of the incident beam. Within the Radiative Beam in Absorbing Media interface, the absorption coefficient needs to be modified to include both the scattering and the absorption coefficients. When evaluating the results, it is thus important to reduce the absorbed heat by the absorbed fraction.

When it comes to display settings, you can tweak video settings to reduce ghosting. Right from contrast ratios, gamma levels, brightness values, and shadow correction to color values, your display allows you to make several changes to improve display quality.

Your GPU creates the visuals you see on screen. If there is an issue with how these graphics are created or sent to the display, you are bound to see some ghosting on your screen.

Do you rush to the monitor service team to get the issue resolved, or is there something that you can do to fix monitor ghosting on your own?

Although changing these parameters does not reduce ghosting at a physical level, these changes can reduce the amount of ghosting visible on the screen. For example, decreasing the contrast ratio can reduce the ghosting you see, as the difference between the brightest and darkest pixels is reduced.

Along with the governing equation, we also need a set of boundary conditions for the material when solving for the scattered light. Given that the incident laser light can enter the domain, it is also reasonable to assume that the scattered light can leave the modeling domain. The Semitransparent Surface feature is appropriate for this situation, and lets us enter an emissivity, \epsilon, and a diffuse transmissivity, \tau_d. These two quantities must be less than or equal to one and define a diffuse reflectivity \rho_d = 1-\epsilon – \tau_d. Scattered light incident upon this boundary will entirely pass through if \tau_d = 1, and, if \tau_d < 1, then the light will be partially diffusely reflected back into the domain.

Therefore, if you look at it, each monitor will offer different levels of monitor ghosting based on its technology. So, if you are planning to buy a new monitor and don't want to fall prey to monitor ghosting, it's best to test the monitor for ghosting using the UFO test.

A semitransparent medium is any material through which a ray of light can travel a significant distance before being extinguished due to a combination of absorbing and scattering. Absorption is the mechanism by which the light energy is converted into thermal energy, leading to a rise in temperature. Scattering is the mechanism by which the light is redirected into other directions. The scattering of light can take many forms: At one extreme is the specular reflection and refraction that occurs at the surfaces of mirrors and dielectrics, while at the other extreme, there can be nearly isotropic scattering, as is observed within a turbid medium such as very muddy water, where the turbidity is due to small suspended particles that are randomly shaped and oriented.

Need a new monitor but confused by different sizes, resolutions, and types? Here's what you need to know when buying a new monitor.

All the wireless devices you have connected to your system use radio waves to communicate with one another. In some cases, these waves can interfere with the signal sent over the video cable and cause ghosting.

Collimatedmeaning in Physics

Now that we know why ghosting happens, we can look at ways to solve it. That said, before trying to fix the issue, it's important to understand that every monitor in the market uses different types of liquid crystal technology, offering different advantages and disadvantages.

Introducing a visual defect that follows fast-moving objects, monitor ghosting is a video artifact that makes your gaming experience less rewarding. That said, ghosting is not a permanent defect like pixel burn-in, and it can be fixed by tweaking the settings on your system/display.

We now need to compute how the scattered fraction of this light propagates through the medium, keeping in mind that it will be both absorbed and re-scattered everywhere. This is where we turn to the Heat Transfer Module’s Radiation in Absorbing-Scattering Media interface, which offers the P1 approximation that solves the equation:

So, if you have a lot of wireless devices connected to your system, you can disconnect them one at a time and see if it fixes the issues you are facing. Not only this, but you can also try to move around the devices that are connected to your system and see if ghosting reduces.

TN panels offer the lowest response time—being the most responsive, while VA panels are the slowest. IPS panels are somewhere in between the two when it comes to response time.

Collimation

As explained earlier, your monitor uses voltages to change the orientation of liquid crystals. Pixel overdrive increases this voltage so that the response time of the liquid crystals is reduced.

Therefore, it is advised that you check the wire for any physical damage or fraying of the cables. If you find any external damage, then simply changing the cable could solve the problems that you are facing.

where G is the radiant intensity of light per steradian, meaning that it accounts for light going in all directions, not just a single direction. The conversion of light to thermal energy is quantified by the term -\kappa G on the right-hand side, which leads to a decrease in radiant intensity. The source term, Q, leads to a volumetric increase in radiant intensity, and, in this situation, comes from the scattered fraction of the losses computed from the Radiative Beam in Absorbing Media interface; so, Q = \frac{\sigma_s}{\kappa_{tot}}Q_r.

Keeping an extra copy of your operating system on a handy USB is often one of the fastest ways to fix a malfunctioning machine.

Most monitors offer three different intensities for pixel overdrive, and selecting the right one can help reduce ghosting drastically. That said, increasing pixel overdrive can cause inverse ghosting as the increased voltage can cause the pixels to overshoot the colors they are supposed to show.

As explained earlier, a higher refresh rate can increase monitor ghosting. So, if you want to reduce ghosting, you can decrease the refresh rate on your system. Doing this will give the pixels on your monitor more time to react, reducing ghosting.

Coherentlight

As we have seen, it is possible to implement a model of absorption and scattering of light quite easily, but it is worth emphasizing that this method has two limitations. First, any specular reflection or refraction of light within the material, such as due to a mirror or lens, is not addressable, so only a reasonably homogeneous piece of material can be modeled. Next, the scattering within the medium is assumed to be isotropic. These limitations are counterweighted by the advantage of computational simplicity: Solving two sets of scalar equations for the collimated and scattered light intensity has very low computational cost. Furthermore, the source terms are easily combined with a thermal analysis to compute the rise in temperature. So, if you are modeling laser light interacting with a reasonably uniform sample of a semitransparent material and can assume isotropic scattering, then this approach is attractive because of its efficiency.

The Radiation in Absorbing-Scattering Media interface allows us to 1) add the absorption and scattering coefficient separately and 2) add a source term using the Radiative Source feature, which provides the scattered fraction of the absorbed heat from the Radiative Beam in Absorbing Media interface.

In some cases, a damaged video port could cause ghosting, and such defects can only be fixed by changing the video decoding hardware on your monitor.

Broadly speaking, monitors use three types of liquid crystals: Twisted Nematic (TN), In-Plane Switching (IPS), and Vertical Alignment (VA). Each of these liquid crystal technologies offers different response times.

Collimating lens

Monitor ghosting is a visual defect seen on monitors while playing fast-paced games or viewing content with expeditious action. This fast-paced nature of the content causes the pixels on the screen to give up— causing a shadow/trail of the object to be seen behind it. So as the name suggests, monitor ghosting is a visual defect that causes a ghost trail of the object to be visible behind it.

But why do the pixels on your display give up, and why does monitor ghosting occur? To understand why ghosting happens, we must understand how a display works and how data is sent from your CPU/GPU to the display.

In addition to this, you should also update the drivers on your system, as it could also solve the ghosting issues you are experiencing.

How to collimatelight

Therefore, if your monitor has a refresh rate of 60 hertz, information on the visuals is sent to the display every 16.6 milliseconds. Once the information is received, the monitor gets to work and starts manipulating the millions of pixels on the screen to display the received images.

where \mathbf{e}_i is the vector describing the direction of the beam and I_i is the intensity of the light as power per unit area, measured in the plane perpendicular to the beam path. There can be several different spatially overlapping incident beams, and one equation, indexed by i, is solved for each. The term \kappa is the absorption coefficient, which quantifies how these beams are absorbed. The absorbed energy is the sum from all incident beams: Q_r = \kappa \sum_i I_i. The assumption of this interface is that all absorbed light energy is converted to heat energy, but we can easily modify the interface settings to also account for scattering.

Distribution of the heat sources arising from the incident beam, left, and the scattered light, right. The sum of these sources contributes to a rise in temperature.

But what do you do if your monitor shows these visual artifacts? Don't worry; we have a set of solutions to help you solve monitor ghosting.

Looking at video artifacts while gaming is any gamer's nightmare, and monitor ghosting is one that tops the list. Not only does ghosting make gaming distracting, but it also affects how you consume content.

The cable connecting your monitor to the system is responsible for transmitting all the video data to the monitor. So, if the cable is damaged, you are bound to get some video artifacts while you game on your monitor.

Hence, it is a good idea to update the GPU drivers on your system before blaming the monitor for the ghosting issues you are seeing.

When a ray of collimated light, such as from a laser, is incident upon a semitransparent medium, it can experience both absorption and scattering. This means that the incident light is both converted to thermal energy and redirected. Under certain assumptions, these phenomena can be modeled using a diffusive approximation in the COMSOL Multiphysics® software. This modeling approach has applications in laser heating of living tissue as well as materials processing. Let’s learn more!

Not only this, modern gaming displays come with overdrive technology that is designed to fix ghosting. So, if you are tired of monitor ghosting, tweak your monitor settings, but if that does not fix the issue, you might need to get a new monitor.

Collimatedbeam divergence

To understand the modeling approach, we will begin by assuming that we have a material with no scattering, only absorption. This situation is possible to model using the Heat Transfer Module’s Radiative Beam in Absorbing Media interface, which solves for the Beer–Lambert law within the material. When using this interface, it is assumed that the beam intensity is known at the illuminated boundary. That is, considering a beam of light of known power propagating through surrounding free space, the specified intensity is based on the fraction of the light that propagates into the material.

Liquid crystals are special compounds containing molecules whose orientation can be changed by applying a voltage. This change in orientation changes the amount of light that can pass through the liquid crystal. Due to this change, the brightness of each sub-pixel can be changed, and the monitor can display any image on the screen.

Coupling the scattering light from the Radiative Beam in Absorbing Media interface to the Radiation in Absorbing-Scattering Media interface.

If you have tried everything listed above and feel that the ghosting on your monitor hasn't reduced, it is best to contact the technical support team for your monitor.

But there is a catch here: although the monitor can change the brightness of each pixel, the liquid crystals take some time to react to the change in the voltage, and this delay is known as the monitor's response time. Therefore, if your monitor has a response time of 20 milliseconds, then the liquid crystals on your monitor take 20 milliseconds to react to the changes in voltage. This delay causes ghosting on your monitor.

A beam of collimated light incident upon a semitransparent medium can experience isotropic scattering, meaning that the light is redirected into all directions equally. This scattering occurs everywhere along the path of the beam, and the scattered light is itself immediately re-scattered, so this image presents a simplified view of the process.

Accounting for both absorption and scattering of collimated light via the Absorption coefficient of the Radiative Beam in Absorbing Media interface.

As explained earlier, if your display has a refresh rate of 60 hertz, then new information reaches the display every 16 milliseconds. That said, the liquid crystals in the display can't react to the information so fast, as they have a response time of 20 milliseconds. Due to this, your monitor shows a shadow of a fast-moving object as the liquid crystals have not changed the brightness levels, and part of the older image is still visible on the monitor.

In terms of evaluating the results, it can be particularly insightful to evaluate the integral of the thermal losses of the incident beam, the thermal losses of the scattered light, and the fraction of the incident beam and scattered light that leaves the modeling domain. The plots and table below show the distribution of these losses as well as the integrals. The distribution of losses can subsequently be used within a heat transfer analysis to compute the variation in temperature.

This brings up the next question, how does the monitor change the images displayed on the screen every 16 milliseconds? Each of the millions of pixels on your monitor comprises sub-pixels consisting of three colors: red, green, and blue. A pixel can display any color using these three colors by changing its sub-pixel brightness. To do this, monitors use liquid crystals.