CN103700350B - A kind of liquid crystal display that can eliminate motion image blurring - Google Patents

Abstract

A liquid crystal display capable of eliminating blurring of moving images is composed of a liquid crystal panel, a backlight source, a display drive module, a backlight control module, a button panel, a power supply, etc. The backlight control module includes a delay circuit, a pulse stretching circuit, and a power drive circuit. The field synchronizing pulse in the video signal is sent to the delay circuit, delayed by T _delay time, and then stretched by the pulse stretching circuit into a backlight lighting pulse with a width of T _on . The power driving circuit turns on the backlight source of the liquid crystal panel when the backlight turn-on pulse is effective. The brightness control signal from the key panel of the display is used to adjust the brightness of the backlight of the LCD panel. The lighting time of the backlight of the LCD panel is only T _on ∕ T _vsync of ordinary displays, the average power of the backlight of the LCD panel does not increase, no additional heat dissipation design is required, and the structure is simple. All the light-emitting components constituting the backlight of the liquid crystal panel are still on and off as a whole, and do not need to be controlled separately.

Description

A liquid crystal display that eliminates blur in moving images

technical field

The invention relates to the field of image display, in particular to a liquid crystal display capable of eliminating blurring of moving image display, which can be applied to various fields requiring clear display of moving images, such as security inspection equipment, food testing equipment, subtitle machines, and dynamic information release screens.

Background technique

LCD monitors are the most mainstream display devices on the market today. Since its inception, although with the advancement of technology, liquid crystal displays have become increasingly perfect in terms of screen size, spatial resolution, color fidelity, viewing angle, etc., but the unique blurring problem when displaying moving images has always troubled manufacturers. and users, limiting its application in occasions where moving images need to be displayed clearly. Studies have shown that the unique image display and switching methods of liquid crystal displays are the root cause of motion blur. The liquid crystal display continuously displays all the pixels of an image until a new image arrives, and then replaces the old image point by point and line by line from top to bottom. This continuous display mechanism causes the human visual system to have a persistent effect, superimposing new and old images together in the mind, resulting in a sense of blur. The faster the motion speed of the image, that is, the greater the displacement between the new image and the old image, the stronger the blur. For observers who need to stare at the LCD screen for a long time, not only can they not see the details of moving images clearly, but their eyes will soon feel tired and uncomfortable.

In order to overcome the problem of blurred display of moving images on liquid crystal displays, there are currently different technical solutions:

Backlight scanning technology: Divide the backlight of the liquid crystal display into multiple groups from top to bottom, and light up each group sequentially. Since any group in the backlight does not emit light for most of the time, for the human visual system, it is equivalent to leaving a long interval between the new and old images, thereby overcoming the persistence of vision effect. This solution can achieve better results when the number of backlight groups is sufficient, but the optical and electrical design of the display backlight is relatively complicated and the cost is high.

Black screen insertion technology: The backlight of the display is always on, but in order to achieve the effect that the images of each field are not displayed continuously, the display time of each image is compressed by software and hardware technology, and the image is displayed between each field. Insert a black image. However, in order to accommodate the doubled number of fields per unit time, the field frequency of the display needs to be doubled, thus requiring a corresponding increase in the response speed of the liquid crystal panel. Therefore, this solution also has the problems of complex design and high cost, and the effect is not ideal when the multiplier of field frequency increase is small.

Image prediction compensation technology: similar to the black screen insertion technology, this technology needs to double the field frequency of the display. The difference is that the image inserted between the real images is no longer a black image, but an image in an intermediate state of motion predicted and calculated by the monitor based on the real image. It can be seen that the technical complexity of this solution is higher than that of the black screen insertion solution, and these inserted images may not be consistent with the real scene, and the effect cannot be guaranteed to be natural and realistic in practice.

High field frequency technology: Different from the above-mentioned black screen insertion technology and image prediction compensation technology, the field frequency of the image is not raised by the display itself, but is given by the image signal source sent to the display. This obviously can avoid the problem of image prediction distortion. However, on the one hand, limited by the physical conditions of the image generation equipment, not all image signal sources have a high enough field frequency; Universal application value.

The above technical solutions can be used alone or in combination to achieve better results. However, as mentioned above, the general problems of these solutions are that the technology is complex and the cost is high, and they are usually only used in the field of broadcasting and television, and only used in occasions requiring a large display area. As for the small-area liquid crystal display matched with ordinary personal computers, due to the dual reasons of technology and market, there are almost no products that can clearly display moving images so far. This is the dilemma faced by the vast number of users who need to clearly observe the image movement process.

In fact, other display technologies other than liquid crystal, as long as they do not adopt a continuous display method, but a point-by-point or progressive scanning display method similar to a traditional CRT (cathode ray tube) display, can effectively avoid motion image blur. Among them, the area of the plasma display is too large, the resolution is low, and the price is still high so far, which cannot meet the requirements of security inspection, food inspection and other equipment for small size, fine image and low price. However, the emerging OLED (Organic Light Emitting Diode) display is troubled by technology, cost, etc., and the area of practical products is too small. It can only be used in mobile phones and tablet computers, and products suitable for ordinary personal computers are still in the research and development stage.

Contents of the invention

The object of the present invention is to provide a liquid crystal display capable of eliminating blurring of moving images, especially a liquid crystal display capable of eliminating blurring of moving images in the horizontal direction. When the movement direction of the image is mainly horizontal and basically stable in the vertical direction, the human eye will see a clear image with fully presented details without feeling tired. Unless otherwise specified, "horizontal" in the text refers to the line scanning direction of the video, and "vertical" refers to the field scanning direction of the video.

In a large number of application examples such as security inspection equipment, food testing equipment, subtitle machines, dynamic information release screens, etc., the image usually only moves in the horizontal direction, and the moving image display area in the vertical direction of the screen is determined in advance. In the layout of the screen, there are usually static image display areas such as menu bars. Therefore, the height of the moving image display area is slightly smaller than the total height of the screen, and there is a spot that the observer focuses on in the moving image display area. The ratio of the total height is usually within 1/2. The method proposed in the present invention ensures that the observer has a clear and no afterimage display effect when observing the moving image of the key attention part, and at the same time ensures that the moving images of other parts in the moving image display area are also clear and identifiable although they have a slight afterimage, and The static image display area such as the menu bar keeps the original clear display effect unchanged. Fig. 1 shows the layout of the display screen of a certain common type of security inspection equipment as an example.

A kind of liquid crystal display that can eliminate moving image blur of the present invention, is the same as conventional liquid crystal display, mainly is made up of several parts such as liquid crystal panel and backlight source, display driver module, backlight control module, button panel, power supply, is characterized in that, The backlight control module includes three main parts: delay circuit, pulse stretching circuit and power drive circuit. The vertical synchronizing pulse in the video signal is sent to the delay circuit for a delay of T _delay time, and then is stretched by the pulse stretching circuit into a backlight lighting pulse with a width of T _on . The power driving circuit turns on the backlight source of the liquid crystal panel when the backlight turn-on pulse is effective. The brightness control signal from the key panel of the display is used to adjust the brightness of the backlight of the LCD panel.

Wherein, according to different adjustment principles, the brightness control signal can be introduced into a pulse stretching circuit to increase or decrease the brightness of the LCD panel backlight by increasing or decreasing T _on ; it can also be introduced into a power drive circuit to control the T _on time The instantaneous power output to the backlight of the LCD panel is used to adjust the brightness.

A liquid crystal display capable of eliminating moving image blur in the present invention, wherein the delay circuit is composed of a first monostable device D1-A and a peripheral resistive capacitor device, and the input field synchronization of the first monostable device D1-A The pulse VSYNC is triggered to generate a low-level pulse LEDDLY with a duration of T _delay . The width of T _delay can be adjusted by adjusting the resistor R2. The pulse stretching circuit is composed of the second monostable device D1-B and surrounding resistive capacitor devices. The second monostable device D1-B is triggered by the rising edge of the low-level pulse LEDDLY to generate a low level with a duration of T _on Pulse LEDLIT. The width of T _on can be adjusted by adjusting the resistor R4. The power drive circuit is composed of operational amplifier D2-A, triode V1, V2 and so on. Under the action of the negative feedback loop composed of operational amplifier D2-A, transistor V2, resistor R9, etc., the voltage at the inverting input terminal of operational amplifier D2-A, that is, the voltage at both ends of resistor R9 will be equal to the non-inverting input of operational amplifier D2-A terminal voltage.

Among them, the resistor R4 and the resistor R7 can use a button-type digital potentiometer with a power-off memory function.

Among them, the brightness control signal comes from the brightness increase and decrease buttons of the panel, which can be added to the input pins of the increase and decrease buttons of the resistor R4 or resistor R7, thereby changing its resistance value or the position of the voltage dividing contact.

A kind of liquid crystal display of the present invention can eliminate moving image blur, its advantage and efficacy are: compared with common liquid crystal display, the time that the backlight source of liquid crystal panel of the present invention is lighted is only T _on / T _vsync of common display, Therefore, the instantaneous power of the backlight source (11) of the liquid crystal panel needs to be increased to _Tvsync / _Ton times of the ordinary display, so that human eyes can feel that the brightness of the screen is equivalent to that of the ordinary display. However, the average power of the backlight source of the liquid crystal panel does not increase, so no additional heat dissipation design is required, and the structure is simple. Moreover, all the light-emitting components constituting the backlight of the liquid crystal panel are still turned on and off as a whole, and it is not necessary to divide them into multiple groups and control them separately as in the conventional backlight scanning technology. To sum up, the liquid crystal display of the present invention does not have obvious technical difficulties in actual implementation, and has remarkable economic efficiency.

Description of drawings

Figure 1 shows the screen layout of a certain type of security inspection equipment

Figure 2 shows the timing relationship between the field sync pulse and the backlight on pulse

Fig. 3 shows the functional block diagram of the backlight control module of the display of the present invention

Fig. 4 shows the circuit diagram of the backlight control module of the display of the present invention

The specific labels in the figure are as follows:

1. Moving image display area 2. Static image display area

3. The total height of the screen 4. Key areas of concern

5. Field synchronization pulse 6. Backlight lighting pulse

7. Delay circuit 8. Pulse stretching circuit

9. Power drive circuit 10. Brightness control signal

11. Backlight

detailed description

The technical solutions of the present invention will be further described below in conjunction with FIGS. 1-4 and embodiments.

As we all know, a conventional liquid crystal display is mainly composed of a liquid crystal panel, a backlight source, a display driver module, a backlight control module, a button panel, and a power supply. The present invention only needs to redesign the backlight control module, without modifying other parts, so as to achieve the purpose of eliminating the blurring of moving images in the horizontal direction. The basic principle is: the backlight control module delays each field sync pulse 5 in the received video signal for a period of time (denoted as T _delay ), and then triggers a backlight lighting pulse 6, so that the backlight is in a field period (denoted as T delay ). T _vsync ) is only turned on for a short time (denoted as T _on ), as shown in FIG. 2 , which is the timing relationship between the field sync pulse 5 and the backlight on pulse 6 . Obviously, the ratio of the image display time of each field is only T _on ∕ T _vsync , if this value is small enough, there will be enough dark time intervals between the images of adjacent fields, and what the human eye sees will be clear images without blurring . If compared with the aforementioned black screen insertion technology, T _vsync ∕ T _on is equivalent to the multiplier of the vertical frequency. Usually, the T _on used in this method is about 1/8 of the value of T _vsync , so the equivalent multiplier of the vertical frequency is 8. The effect of avoiding motion blur is significantly better than the black screen insertion technology with field frequency multiplier of 2 or 4. T _vsync is the reciprocal of the field frequency. The physiological characteristics of the human eye require the field frequency to be higher than 70Hz to avoid flickering. Therefore, T _vsync should usually be within 14ms.

In fact, in the present invention, what the human eye sees is the state of the liquid crystal panel at the moment when the backlight lighting pulse is effective. At this time, a new field of images is replacing the old field of images in a certain width area in the vertical direction of the screen. If the image is in motion, that is to say, the old and new images are different in this alternate area, the human eye will see the afterimage of the old image. Obviously, adjusting T _delay can adjust the position of the image overlapping area in the vertical direction, so that it covers the static image display area 2 and is far away from the focus area 4 as much as possible. If T _alt is defined as the time required for a certain pixel of the LCD panel to complete the change, then the ratio of the image change area to the total screen height 3 is (T _alt +T _on -T _blank )/(T _vsync -T _blank ), where T _blank is Vertical blanking time, about 1/20 of T _vsync . Ordinary LCD panel T _alt ∕T _vsync is about 1/6~1/3, if T _on ∕T _vsync is 1/8, then the image switching area accounts for about 25%~43% of the screen height 3, and the remaining 57% of the screen The ~75% part is completely sufficient for the display of focus area 4. Apparently, increasing the response speed of the liquid crystal panel (that is, shortening the pixel replacement time T _alt ) and shortening the backlight lighting time T _on are beneficial to the expansion of the focus area 4 . Under the current technical conditions, there is indeed a possibility that part of the overlapping area falls into the moving image display area 1, and at this time, the observer will see a slight afterimage at a position opposite to the direction in which the image advances. However, the residual image appears outside the focus area 4, and the residual image is always kept at a certain distance from the image, so it does not cause blur and fatigue to the human eye. For a specific application instance, after the T _delay is adjusted according to the actual situation of the application instance, it is not necessary to adjust the T _delay in daily use.

A kind of liquid crystal display that can eliminate moving image blur of the present invention, its backlight control module functional block diagram is shown in Figure 3, and it comprises delay circuit 7, pulse stretching circuit 8, power drive circuit 9 three main parts. The vertical synchronization pulse 5 in the video signal is sent to the delay circuit 7 for a delay of T _delay time, and then is stretched by the pulse stretching circuit 8 into a backlight lighting pulse 6 with a width of T _on . The power drive circuit 9 turns on the backlight source 11 of the liquid crystal panel when the backlight turn-on pulse 6 is valid. The brightness control signal 10 from the key panel of the display is used to adjust the brightness of the backlight source 11 of the liquid crystal panel. According to different adjustment principles, the brightness control signal 10 can be introduced into the pulse stretching circuit 8 to increase or decrease the brightness of the liquid crystal panel backlight source 11 by increasing or decreasing T _on ; it can also be introduced into the power drive circuit 9 to control T The instantaneous power output to the liquid crystal panel backlight source 11 during the _on time is used to adjust the brightness.

In order to further understand the specific implementation method of the backlight control module involved in the present invention, please refer to the schematic circuit diagram shown in FIG. 4 . The first monostable device D1-A and surrounding resistive capacitor devices constitute a delay circuit 7, and the first monostable device D1-A is triggered by the input field synchronization pulse VSYNC to generate a low-level pulse LEDDLY with a duration of T _delay . The width of T _delay can be adjusted by adjusting the resistor R2. The second monostable device D1-B and surrounding resistive capacitor devices constitute the pulse stretching circuit 8, and the second monostable device D1-B is triggered by the rising edge of the low-level pulse LEDDLY to generate a low level with a duration of T _on Pulse LEDLIT. The width of T _on can be adjusted by adjusting the resistor R4. The operational amplifier D2-A, the triodes V1, V2 and the like constitute the power drive circuit 9 . Under the action of the negative feedback loop composed of operational amplifier D2-A, transistor V2, resistor R9, etc., the voltage at the inverting input terminal of operational amplifier D2-A, that is, the voltage at both ends of resistor R9 will be equal to the non-inverting input of operational amplifier D2-A terminal voltage. Therefore, when LEDLIT is at a low level, the triode V1 is cut off, the voltage across the resistor R9 will be equal to the divided voltage value of the resistors R6, R7, and R8, a large current flows from the collector to the emitter of the triode V2, and the backlight 11 is turned on. light up. When LEDLIT is at a high level, the transistor V1 is turned on, the voltage of the non-inverting input terminal of the operational amplifier D2-A is almost 0, the voltage drop on the resistor R9 is also close to 0, the transistor V2 is cut off, and the backlight 11 is turned off. Among them, the resistor R4 and the resistor R7 can use a button-type digital potentiometer with a power-off memory function. The brightness control signal 10 comes from the brightness increase and decrease buttons of the panel, and can be added to the input pins of the increase and decrease buttons of the resistor R4 or resistor R7, thereby changing its resistance value or voltage-dividing contact position. When the resistance value of the resistor R4 increases, the width of T _on will increase, so that the lighting time of the backlight source 11 will be prolonged, and the brightness perceived by human eyes will increase. When the position of the voltage dividing contact of the resistor R7 moves upward, the voltage of the non-inverting input terminal of the operational amplifier D2-A increases, and the current flowing through the backlight source 11 increases, which also increases the brightness.

Claims (4)

1. can eliminate a liquid crystal display for motion image blurring, mainly by liquid crystal panel and backlight, display driver mouldPiece, backlight control module, key panel, power supply composition, is characterized in that: backlight control module wherein comprise delay circuit,Stretch circuit, three major parts of power driving circuit; Field system chronizing impulse in vision signal is sent in delay circuit, prolongsT late_delayTime is then that width is T by stretch circuit broadening again_onBacklight lightening pulse; Power driving circuit is at the back of the bodyWhen the bright pulse of luminous point is effective, light liquid crystal panel backlight; Be used for adjusting liquid from the brightness control signal of display key panelThe brightness of crystal panel backlight;

Wherein, delay circuit is made up of the first monostable unit D1-A, resistance R 1, R2 and capacitance resistance ware C4, the first monostable devicePart D1-A, resistance R 1, R2 and capacitance resistance ware C4 connect successively, are connected between VDD-to-VSS, and the tie point of R2 and C4 is connected to D1-ATime constant control input end; The field system chronizing impulse VSYNC that the first monostable unit D1-A is transfused to triggers, and produces while continuingBetween be T_delayLow level pulse LEDDLY; Stretch circuit is by the second monostable unit D1-B, resistance R 3, R4 and resistance-capacitance devicePart C1 forms, and the second monostable unit D1-B, resistance R 3, R4 and capacitance resistance ware C1 connect successively, are connected between VDD-to-VSS R4Be connected to the time constant control input end of D1-B with the tie point of C1; The second monostable unit D1-B is by low level pulse LEDDLYRising edge trigger, the generation duration is T_onLow level pulse LEDLIT; Power driving circuit by operational amplifier D2-A,Triode V1, V2, resistance R 5, R6, R7, R8, R9 form; R5 one end receives the low level pulse from stretch circuitLEDLIT, the other end is connected to the base stage of V1; R6, R7, R8 connect successively, are connected between VDD-to-VSS; The grounded emitter of V1, collectionThe tap of electrode and R7 is all connected with the in-phase input end of operational amplifier D2-A; The inverting input of operational amplifier D2-ABe connected with V2 emitter stage, output is connected with the base stage of V2; R9 is connected between the emitter stage and ground of V2, and backlight is connected on V2Colelctor electrode and backlight power supply between; The work of the feedback loop forming in operational amplifier D2-A, triode V2, resistance R 9With under, the inverting input of operational amplifier D2-A, the voltage at resistance R 9 two ends will equal the homophase of operational amplifier D2-AThe voltage of input.

2. a kind of liquid crystal display that can eliminate motion image blurring according to claim 1, is characterized in that: this is brightDegree control signal both can have been introduced stretch circuit, by increasing or reduce T_onImprove or reduce liquid crystal panel backlightBrightness; Also can introduce power driving circuit, by controlling T_onIn time, exporting to the instantaneous power of liquid crystal panel backlight comesAdjust brightness.

3. a kind of liquid crystal display that can eliminate motion image blurring according to claim 1, is characterized in that: resistanceR4 and resistance R 7 can be used the push button digital regulation resistance with power failure memory function.

4. a kind of liquid crystal display that can eliminate motion image blurring according to claim 1, is characterized in that: brightnessControl signal derive from panel brightness increase, subtract button, can be added in resistance R 4 or resistance R 7 increasing, subtract on button input pin,Thereby change its resistance or point voltage contact position.