Lmax camera

When observing an object, the angle formed by the light emitted from two ends of the object (up, down or left and right) at the center of the human eye. The smaller the size of the object, the farther away from the observer, and the smaller the viewing angle. The minimum visual angle that normal eyes can distinguish two points on an object is about 1 point.

[Edit this paragraph] Overview

The angle between the line of sight and the vertical direction of the display, etc. The reflection of the screen is different in all directions. The farther away from the center of the screen in the horizontal direction, the lower the brightness. The viewing angle when the brightness drops to 50% is defined as the viewing angle.

The brightness of the image in the viewing angle is satisfactory; From the perspective, the brightness of the image is not enough. Generally speaking, the greater the screen gain, the smaller the viewing angle (metal curtain); The smaller the gain, the larger the viewing angle (white plastic curtain, because taking care of students, educational curtain is mostly white plastic curtain). Glass bead curtains are more popular.

The angle formed by the intersection of two rays from two ends of an object in the eyeball. The smaller the object, the farther the distance, and the smaller the viewing angle.

The angle between the two points with the largest distance on the scene that can be photographed by the camera lens and the connecting line of the lens. The viewing angle is inversely proportional to the focal length.

Camera viewing angle

The angle between the lens center and the diagonal ends of the imaging plane is the lens angle. For the same imaging area, the shorter the focal length of the lens, the larger the viewing angle. For the lens, the angle of view mainly refers to the angle range it can reach. When the focal length becomes shorter, the viewing angle becomes larger, and a wider range can be photographed, but this will affect the clarity of distant subjects. When the focal length becomes longer, the viewing angle becomes smaller, which can make distant objects clear, but the width range that can be photographed becomes narrower.

Television perspective

Also known as the viewing angle, the so-called viewing angle refers to the maximum angle at which the screen image can still be clearly seen when standing at a certain angle near the screen. The viewing angles are all horizontally symmetrical, but not necessarily vertically, and the up and down viewing angles are often smaller than the left and right viewing angles. The viewing angle of plasma is mostly about 160 degrees, and it has a wide field of vision, which can provide exceptionally bright, uniform and smooth pictures and an unprecedented viewing angle. When ordinary TV sets are watched at a temperature greater than 160 degrees, the picture has been seriously distorted, and the LCD is far behind.

Viewing angle of display

Refers to the angle at which users can clearly observe all the contents on the screen from different directions. Because the light source for LCD display has a certain directivity when it is output after refraction and reflection, color distortion will occur when it is viewed beyond this range, and CRT display will not have this problem.

At present, the viewing angles of liquid crystal displays sold in the market are all symmetrical, but the up and down angles are not necessarily symmetrical, and often the up and down angles are smaller than the left and right angles. When we say that the viewing angle is about 80 degrees, it means that when we stand 80 degrees away from the normal of the screen (that is, the imaginary line in the middle of the display), we can still see the screen image clearly. The larger the viewing angle, the better the viewing angle, and the more applicable the LCD display.

Because everyone's vision is different, we take contrast as the standard, and the greater the contrast measured at the maximum viewing angle, the better. At present, the viewing angle of most products on the market is above 120 degrees, and some products are above 140 degrees.

[Edit this paragraph] The application of visual angle change

1. Automatic perspective and user perspective

Rocky provides a variety of perspectives, including automatic perspective and user perspective for more reasonable use.

Through the screen photos above, we can find that even in the same place, we can get completely different feelings.

2. Switching method between automatic viewing angle and user viewing angle

You can press the Z key on the keyboard.

3. Advantages of automatic viewing angle

Playing games from multiple perspectives may make you a lost child in a rockery. Moreover, if you can't accurately judge the shadow in Loki, you are likely to be late for an important date. In order to prevent these situations, an automatic viewing angle is designed.

Using automatic viewing angle, you can easily find the lost direction.

(1) Find your way in the fields of Loki.

As shown in the screen photo above, the arrow in the auto-view mini-map points to the north, which is very useful when viewing the map.

(2) Watching time in Loki's game.

Rocky's time is judged by the shadow, and the role of the shadow is the same as that of the coronation instrument.

Only when the viewing angle is due north can we estimate the time more accurately.

Working in Loki judges time according to the shadow, so pay attention to the shadow and time when working!

(3) Determine Loki's game time (automatic perspective).

■ Shadow of the West: 6 am (Avica disappears)

■ Shadow facing north: 12 noon

■ Shadows of the East: 6 pm (Avica rises)

4. Advantages of user perspective

(1) can fix the desired viewing angle.

When watching magnificent scenery or fighting, if you choose automatic viewing angle, it will be very inconvenient because the viewing angle is constantly moving. The user's perspective can fix the desired perspective to play the game.

In places with dense trees or complex terrain, like the screen photos above, monsters may fall on books.

If you use the user's perspective instead, you can bypass the terrain obstacles and find the hidden monsters.

You can see the bear behind the tree in the screen photo above.

(2) Ensure a broad vision.

Using a top-down perspective, you can only see a certain spatial range.

Especially when judging monsters in underground rooms, user perspective is much more useful than automatic perspective.

(3) Find your way in the underground city according to the complicated map.

The red arrow in the mini map indicates the direction of the current viewing angle. The small white circle is the direction of the character's perspective.

But try to change the angle, and you will find the door and the road in front of you.

(4) Change your perspective when traveling in the field.

In Dugar Corridor, Dunbaron and other places. Escape to the south, and their roles can't be seen from the automatic perspective.

Like the entrance to the dugard corridor. If you use automatic viewing angle, you can't judge where to escape.

You can easily find the corridor to Dugard from another perspective.

Similarly, when entering a village building, the change of perspective is very useful.

[Edit this paragraph] Color management of liquid crystal display changing with viewing angle

One of the main disadvantages of liquid crystal display technology is color shift caused by viewing angle change. With the increase of viewing angle, not only the color will shift, but also the brightness and contrast will decrease, and the image quality will deteriorate. This paper will introduce the measurement of chromatic aberration characteristics and the consideration of human factors in the change of viewing angle, and put forward new solutions. By adjusting the transmittance of backlight and LCD panel at the same time, the color shift phenomenon can be reduced, which can not only reduce the loss of brightness and color saturation with the increase of viewing angle, but also reduce the power consumption of backlight and prolong the service life of battery.

Liquid crystal panel is the mainstream of display at present. Whether it is a small-sized panel for portable devices such as digital cameras, mobile phones, personal digital assistants and video games, or a large-sized LCD TV, wide viewing angle is an important appeal. Generally speaking, LCD TV really needs wide viewing angle technology to meet the needs of many people sharing high-quality pictures at the same time, but on the other hand, small-sized panels, such as PDA, also need wide viewing angle technology to adapt to the changing viewing angle of users. Although these small-sized monitors that can be put on your hand can be adjusted at will to find perfect angle, in fact, there are more important factors that will determine the direction of the handheld monitor. Taking the display screen of a digital camera as an example, one of the main reasons why a digital camera can replace the traditional negative camera is that it can view the results just shot or about to shoot on the spot. The images presented on the screen can help the photographer decide the shutter timing, composition method and exposure adjustment. Once the image shooting is completed and the effect is not as expected, he can immediately decide whether to retake it to get a better image, or delete the image file to save memory space, and finally decide the size and quantity of enlarged printing, or send it to friends and relatives to share through the network. Therefore, the image quality of LCD plays a vital role in the process of image acquisition and reproduction. In the actual shooting process, the orientation of the camera is usually determined by the subject, not by the photographer's perspective. For example, use a low angle when shooting children, use a prone angle when shooting flowers, and hold the camera above your head when catching stars surrounded by fans. Under different circumstances, it is not easy and practical to adjust the LCD to the positive viewing angle, and the color deviation caused by the off-angle viewing angle leads to the photographer's misjudgment of the image. In order to make up for this shortcoming of LCD, professional digital cameras will provide a histogram for photographers to accurately check the image quality.

In the past few years, wide viewing angle has become the focus of research and development in LCD industry, such as variations of different vertical alignment (VA) technologies (references. 2). Although VA technology improves the width of acceptable viewing angle, it is not an ideal solution for portable screens, and its cost is to maintain color saturation by using filters with low transmittance, which leads to higher power consumption and energy consumption.

These methods focus on increasing more acceptable viewing angles, because the panel cannot be changed after design and manufacture, nor can it be dynamically adjusted according to the number and direction of users.

Another method is to let the LCD automatically correct the brightness and color according to the user's direction. This method requires the camera to capture the user's face image to calculate the user's perspective. The advantage of this independent plug-in method is that it has nothing to do with panel design, and it can be applied to panels with different processes, and even different modifications can be made for each individual panel to make up for the differences in manufacturing processes.

It is not a brand-new concept to use the information provided by external sensors to adjust the image of the display. In the current TV products, there are many low-priced models that use sensors to detect the intensity of ambient light, and then adjust the intensity of backlight according to it, so as to achieve the effect of comfort and power saving. In the foreseeable future, this technology, which can adapt to different viewing environments, is bound to be extended to other application fields. For mobile phones and handheld computers, the current mid-priced models have already provided the camera function, and even CCD camera lenses are available before and after. If we can use these cameras to capture users' behaviors, we can manage the operation of the system more effectively. When the user leaves, the system can turn off unnecessary modules such as display, keyboard and mouse to save energy. In recent years, more and more attention has been paid to the trend of improving product design by using the research of man-machine interface and interaction.

Viewing angle characteristics of liquid crystal panel

In general industrial applications, the acceptable viewing angle (VA) of LCD is defined by brightness contrast.

Brightness contrast is defined as the ratio of maximum brightness to minimum brightness (Lmax/Lmin). This method can only express the breadth of acceptable visual angle, ignoring the phenomenon of color deviation, so it can not express the trend of color quality deterioration under acceptable visual angle. For example, in Figure 2, the same monitor (Acer AL 19 13) is viewed from three different angles. Although all three images meet the above definition of acceptable viewing angle of CR≥ 10, in practice, most users cannot accept the quality of the last two images. The definitions of viewing angle (θ) and azimuth angle (φ) are shown in figure 1.

Figure 1: Definition of viewing angle and azimuth.

The viewing angle of the LCD is from 0 to 30. The brightness and contrast of M60 gradually decrease, and the color shifts.

It is an arduous task to sample the measured value if it is measured by a general luminometer. With the help of Cone Polarization Tester (ConoScope, autronic-MELCHERS GmbH), the brightness and chromaticity values of all viewing angles in the hemisphere can be obtained within one minute. Therefore, we can measure different pictures and accurately grasp the viewing angle characteristics of LCD.

In the white picture (middle picture), the maximum brightness appears at 0 horse ugly A, and decreases with the increase of viewing angle; However, when the picture is black, the minimum brightness appears at 0 Ma Chou A and increases with the increase of viewing angle. On the contrast map, if we draw a horizontal line with CR= 10, the area above the horizontal line defines an acceptable perspective, that is, 45 positions and 60 wealth.

The picture shows the relationship between brightness and viewing angle change under four different gray levels of black and white. Observe the change trend of the right cross-sectional curve. The bell-shaped normal distribution curve originally in the white picture will be deformed with the decrease of gray level. It can be observed from the contour map that when the gray level decreases, the viewing angle of maximum brightness will shift to the upper right. Fig. 5 shows the measurement results of LCD panel power consumption. The measurement results of backlight brightness and power consumption are shown in Figure 6.

Study on Human Factors of Perspective Change

In order to understand the phenomenon of visual angle change when ordinary people use monitors, we conducted two experiments to explore the degree of visual angle change. These two experiments are aimed at the application of fixed display and portable display respectively. The purpose of the experiment is to show that it is difficult for users to maintain a fixed viewing angle even with a fixed display, let alone a portable display.

Fixed application

In this experiment, we recorded the eye movement of the user when operating the desktop computer, and then calculated the changing behavior of the viewing angle.

First, between the user and a 19 "LCD, we give M a 45-horse semi-reflective and semi-transmissive mirror. Set the cameras at the same optical distance to record the position of the user's eyes. In order to locate the position of eyes, we put a grid background behind the user as a reference coordinate. Next, let the user operate a computer game and shoot at the same time. The recorded eye trajectory is shown in Figure 8. The relationship between visual angle change and time is shown in fig. 9.

The results show that the change of viewing angle is close to normal distribution. Three conclusions can be drawn here. First, it is difficult to maintain the user's viewing angle at 0. Second, the viewing angle of 0 is quite high, that is, the larger the viewing angle, the smaller its probability. Third, there is no certain trend in the direction of visual angle change, although the probability of left-right change will be slightly higher than that of up-and-down change.

Portable application program

Taking personal digital assistant (HP iPaq 6530) as the experimental platform, we made a simple device to record the change of visual angle when using portable system. First, install a webcam above the PDA to shoot the user's eyes. At the front end of the webcam lens, we put a transparent hemisphere with concentric rings with different radii as the reference coordinates for calculating the viewing angle. The principle of calculating viewing angle is similar to that of a three-dimensional protractor. After the experiment, the film was analyzed, the position of eyes was recorded, and the change of viewing angle was calculated.

In the experiment, we let users use PDA to do two functions. The first operation is telephone dialing. First, the user clicks on the phone application with the pen of the right hand to dial. The graph 1 1 shows the trajectory of the user's eye movement. First of all, when the user dials, the perspective will focus on the vicinity. After the call is dialed, the user picks up the personal digital assistant and moves it to his ear, which will greatly change the perspective.

The second operation is to take a photo with PDA. The user first selects the photography mode with the pen of the right hand, and at this time, the angle of view is focused on (0 A0? . Next, rotate the PDA 90 degrees clockwise and adjust the shooting angle (-15 degrees A- 12? . After pressing the shutter, the user holds a PDA and looks at the shooting results (-5 A-3? .

The experimental results show that it is almost impossible to keep PDA at a fixed angle.

Literature review of automatic backlight adjustment

LCD includes two main parts: LCD panel and backlight module. Each sub-pixel on the LCD panel can be regarded as a voltage-controlled light valve. Open light valves represent bright sub-pixels, while closed light valves represent dark sub-pixels. In other words, in transmissive liquid crystal displays, we achieve the required brightness by blocking the backlight. Therefore, we not only waste the blocked light, but also waste the energy needed to generate it.

Automatic backlight adjustment is the most effective way to reduce the power consumption of transmissive displays. Simply put, the concept of backlight automatic adjustment is to dim the backlight to reduce power consumption, and at the same time increase the light transmittance of the panel to maintain brightness (References 6, 7 and 8).

In order to compensate the image distortion caused by backlight dimming, it is necessary to adjust the light transmittance of the panel properly. Literature 6 puts forward a method to restore the original brightness.

Where bw is the backlight intensity and α is the backlight adjustment rate (for example, 80% means that the backlight is dimmed by 20%). According to this formula, the panel transmittance must be multiplied by 1/0.8 when the backlight is dimmed to 80%. When t/α is greater than 1, the original brightness has reached saturation and cannot be restored, resulting in image distortion. Although this algorithm can restore the brightness of the dark part, the bright part is easily distorted because of saturation.

Because the above methods of restoring brightness are often not feasible in many images, we must find other methods. One way is to restore the original contrast. Literature 8 proposes to compensate the loss of brightness by increasing contrast.

Where bw is the backlight intensity, α is the backlight adjustment ratio, C is the contrast defined by us, L is the original brightness, L* is the adjusted brightness, and gl and gu are the best solutions we are looking for. Our goal is to keep the same brightness when viewing the monitor from any angle. When the viewing angle deviates from 0, the brightness of Ma Cong A may increase or decrease. If the brightness increases, we can dim the backlight to save power. If the brightness decreases, you must brighten the backlight to restore the original brightness. The whole problem can be solved as an optimization problem. Our objective functions are bL, gl, gu, and under the specified visual angle and FC conditions, the power consumption P is minimized.

discuss

We developed a software tool with Visual Basic to simulate the visual effects of LCD in different perspectives. As long as we input the specified image and the specified viewing angle (θ, φ), the screen will show the predicted visual effect. Based on the measurement results of the cone polarization tester in the early stage, the program predicts brightness attenuation and color shift with the help of look-up table and interpolation method, and presents the simulated designated image on the display in real time. Here, we need a CRT or other screen that is not affected by the viewing angle to present the simulation results. Represents the visual effect of simulation.

We can predict the power consumption by adding the equation 1, 2 to the measurement results of the cone optical polarization tester. When the viewing angle cuts from 0 to 0? 5. The maximum brightness of image A of Gancha decreased from 250.6cd/m2 to 194.83 cd/m2 and 127.03 cd/m2 respectively. When backlight adjustment is not used, in order to maintain the original brightness, it is necessary to increase the backlight intensity to 128% and 197%. Therefore, automatic backlight adjustment can effectively reduce power consumption.

label

We propose to detect the user's viewing angle, and use the algorithm proposed in this paper to adjust the transmittance of backlight and LCD panel to maintain the image quality at different viewing angles and save power consumption. We also developed software to simulate the brightness and color shift caused by the change of viewing angle. In the future, we will study and apply similar methods to solve other problems related to display.