KR20070105514A - Apparatus for representing gradation and method thereof - Google Patents

Abstract

An apparatus for displaying gray scale according to the number of bits of a gray scale level and a method thereof are provided to display gray scale exactly by using minimum numbers of switching units. An apparatus for displaying gray scale includes an illumination unit(210), a gray scale displaying unit(230), and a gray scale controller(220). The illumination unit radiates lights in proportion to a magnitude of a current. The gray scale displaying unit controls switching of switching elements corresponding to the number of bits of a gray scale level, varies current amounts flowed into the illumination unit, and determines a gray scale of the lights radiated from the illumination unit. The gray scale controller receives image signals, generates gray scale levels of the image signals, and switches the switching elements.

Description

Apparatus for representing gradation and method according to the number of bits of gradation level

1 is a block diagram of a conventional gray scale display apparatus using a diode.

2 is a block diagram of a gradation representation device according to the number of bits of a gradation level according to the present invention.

3 is a detailed block diagram of FIG. 2 using a FET.

4 is a detailed block diagram of FIG. 2 using BJT.

5 is a flowchart of a gradation representation device according to the present invention.

6 is a detailed flowchart of FIG. 5.

7 is a graph showing the light output-current characteristics of a laser diode.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection system, and more particularly, to a gradation representation device and method according to the number of bits of gradation level using light emitting means.

Laser diodes (LDs) or light emitting diodes (LEDs), which are representative light emitting means, are semiconductor devices used as micro light sources such as laser pointers, CDs, DVDs, and bar code readers.

By the way, when such a diode is used for a display device or a medical device, it is necessary to appropriately adjust the output of the diode.

1 is a block diagram of a conventional gray scale display apparatus using a diode.

In FIG. 1, the power supply circuit 100 is connected to an input terminal of the laser diode 110 to supply a current, and the magnitude of the current passing through the MOSFET 125 changes in proportion to the voltage by the DAC output 120. By using, to control the magnitude of the current passing through the laser diode (110). As a result, the gray level of the emitted light is adjusted according to the magnitude of the current passing through the laser diode 110.

However, the conventional gray scale display device is sensitive to the voltage level applied to the MOSFET, is weak in noise, and can not instantaneously change the current flowing through the MOSFET, resulting in a slow rate of gray scale change.

An object of the present invention is to determine the number of switching means connected in parallel according to the number of bits of the gradation level to configure the gradation representation device, an apparatus and method for expressing gradation accurately and quickly using the minimum switching means To provide.

The technical problem as described above includes the step of constantly applying a predetermined voltage to the input terminal of the light emitting means; Receiving an image signal and generating a gradation level corresponding to the image signal; And switching the switching means corresponding to the number of bits of the gradation level to determine the gradation of light emitted from the light emitting means.

In order to achieve the above technical problem, the light emitting means for emitting light having a brightness proportional to the magnitude of the current; A gradation representation unit for controlling the switching of the switching elements corresponding to the number of bits of the gradation level to determine the gradation of light emitted from the luminescence means by changing the amount of current flowing through the luminescence means; There is a need for a gray scale display device including a gray control unit for receiving a video signal, generating a gray level for each video component of the received video signal, and switching the switching means corresponding to the number of bits of the gray level. .

Light emitting diodes are also referred to as light emitting diodes (LEDs). The luminescence that occurs when a voltage is applied to a semiconductor is called electric luminescence.

Suitable materials for light emitting diodes are those that satisfy the conditions such that the light emission wavelength is present in the visible or near infrared region, the light emission efficiency is high, and the p-n junction can be manufactured. Light-emitting diodes mainly include gallium arsenide GaAs, gallium phosphide GaP, gallium-arsenide-phosphorus GaAs1-x Px, gallium-aluminum-arsenic Ga1-xAlxAs, indium phosphide InP, indium-gallium-phosphate ln1-xGaxP, and the like. Group 2 or 3 element compound semiconductors are used, but research is also being conducted on 2 B, 6 B, 4 A, and 4 B groups.

The light emitting mechanism is largely divided by recombination of free carriers and recombination at an impurity emission center. By recombination of free carriers, the emission wavelength is approximately equal to ch / Eg (c is the luminous flux, h is Planck's constant, and Eg is the energy width of the forbidden band). In the case of gallium arsenide, it becomes near-infrared light of about 900 nm. In gallium-arsenic-phosphorus, Eg increases with increasing phosphorus content, making it a visible light emitting diode.

On the other hand, in the case of recombination at the impurity emission center, the emission wavelength varies depending on the type of impurities added to the semiconductor. In the case of gallium phosphide, light emission involving zinc and oxygen atoms is red (wavelength 700 nm), and light emission involving nitrogen atoms is green (wavelength 550 nm). Light emitting diodes are smaller than conventional light sources, have a long lifespan, and have low power and good efficiency because electrical energy is directly converted into light energy.

In addition, it is used in display devices of automotive instrumentation, display lamps of various electronic devices such as optical communication light sources, numeric display devices, and card readers of calculators. In addition, the injection type semiconductor laser is a kind of light emitting diode having a very high injection density, and the inversion distribution can be generated to generate coherent light.

Meanwhile, the laser diode LD is a diode that generates a laser using a forward semiconductor junction as an active medium. The laser diode LD is called an injection type diode or a semiconductor laser diode, and gallium arsenide (GaAs) is used as a material.

In particular, the laser diode (LD) is a device that can emit light of various wavelengths (ultraviolet, visible, infrared) depending on the type of material, and the color of the output light is very sharp and the output of the light is strong. It has been used for optical communication, laser printer, etc., but in recent years, its application field is gradually expanded to display light source, lighting and special light source of specific wavelength, and as the optical communication market recovers, the world market of laser diode (LD) is gradually It is expected to increase.

PN junction, quantum well or superlattice structure is mainly used for the active layer stacking structure, and group III-V compound composition such as AlGaAs series and gallium nitride is used as the active layer material.

The development of devices that record large amounts of data is accelerating as the high-speed Internet network becomes faster and the demand for quality service increases. Diodes are widely used in communications, storage and recording devices, and medical fields.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention.

2 is a block diagram of a gradation representation device according to the present invention.

The power supply circuit 200 constantly applies a predetermined voltage to the diode 210. Preferably, the power supply circuit 200 may include a direct current (DC) voltage source.

The diode 210 is connected in series with the power supply circuit 200 and emits light in proportion to the magnitude of the current passing through it. Preferably, the diode 210 may include at least one of a laser diode (LD) or a light emitting diode (LED).

The gradation expression unit 230 includes a plurality of switching means connected in series with the diode 210 and each connected in parallel. The number of the plurality of switching means is determined by the number of bits of the gradation level to be expressed. That is, the number of the switching means needs one more than the number of bits of the gradation level to be expressed. That is, nine switching means are required to express the eight-bit grayscale (256 grayscale).

The gradation expression unit 230 controls the magnitude of the current passing through the diode 210 in a digital manner rather than an analog manner. That is, the magnitude of the current passing through the diode 210 becomes a discontinuous value with respect to time.

The gray control unit 220 receives an image signal and generates a gray level of the image signal. In addition, the gray control unit 220 controls switching to turn on as many switching means as necessary to express the gradation level of the image signal among the plurality of switching means included in the gradation display unit 230. In this case, a description of the number of switching means to be turned on will be described later.

Preferably, the plurality of switching means included in the gray scale display unit 230 may be a plurality of transistors, and the gray control unit 220 applies a predetermined voltage to each of the plurality of transistors to turn on the transistors. You can. In this case, the predetermined voltage is a threshold voltage of the transistor.

Preferably, the gray control unit 220 may include an input means of an image signal, a gray level calculation unit of the image signal, and a voltage application unit according to the gray level.

Preferably, the gray control unit 220 may be configured in a firmware (firmware) method.

The operation of the gradation expression unit 230 will be described as follows. In order to control the current as a digital signal, the switching means for controlling the current of the laser diode LD are arranged by one more than the number of bits, and the switching means corresponding to the number of bits is the switching control of the gray controller 220. It is turned on or off by. In this case, the gray controller applies a threshold voltage for switching control.

For example, when the input image signal is 0, the switching means for flowing an offset current is turned on. Similarly, when the gray level of the input video signal is 1 (00000001), the first switching means through which the smallest current flows is turned on and at this time, 1 mA is designed to flow. If the gray level of the input video signal is 2 (00000010), the second switching means is designed so that the current flows by twice as much as the switching means through which the smallest current flows, that is, by 2 mA. The rest of the switching means are also designed to flow 4mA, 8mA, 16mA, 32mA, 64mA, 128mA. Then, it is possible to express the gray scale using nine switching means to represent the 8-bit gray scale.

)는 3개의 스위칭 수단들이 통과시킬 수 있는 크기의 전류량 ,즉 11mA가 된다. 또한 이 전류량은 다이오드(210)를 통과하는 전류량이므로, 이 전류량에 따라 다이오드에서 방출되는 빛의 계조가 결정된다. If the gray level of the image signal is 11, the gray control unit 320 includes three switching means designed to flow 1 mA, 2 mA, and 8 mA, including an offset switching means. Switching control to be on. At this time, since the switching means are connected in parallel with each other, the total current passing through the switching means (

) Is the amount of current that the three switching means can pass, ie 11mA. In addition, since the current amount is the amount of current passing through the diode 210, the gray level of light emitted from the diode is determined according to the amount of current.

3 is a detailed block diagram of FIG. 2 using a FET. Referring to Figure 3, the configuration of the gray scale representation device using the FET as follows.

The power supply circuit 300 constantly applies a predetermined voltage to the diode 310. Preferably, the power supply circuit 300 may include a direct current (DC) voltage source.

The diode 310 is connected in series with the power supply circuit 300 and emits light in proportion to the magnitude of the current passing through it. Preferably, the diode 310 may include at least one of a laser diode (LD) or a light emitting diode (LED).

Preferably, the present invention may further include a heat sink (not shown) connected to the diode 310 to cool the temperature of the diode 310 to a predetermined temperature or less. Preferably, the heat sink unit (not shown) may be in the form of a heat sink attached to the diode 310 or in the form of a heat sink attached to the diode 310 and a cooler attached to the heat sink. In this case, the heat sink unit (not shown) prevents the diode from overheating.

On the other hand, the gray scale display unit 330 includes an offset transistor 332 for passing the offset current of the diode 310. That is, in FIG. 3, the transistors may be divided into a gray scale transistor 331 and an offset transistor 332.

In this case, the gray scale transistors 331 need as many as the number of bits of the gray level. That is, in order to express the number of levels of the gradation level 8 bits, eight gradation expression transistors 331 are required in addition to the offset transistor 332.

In addition, the predetermined resistors 333 included in the gray scale display unit 330 are connected in series to each of the plurality of transistors 331 and 332. These resistors 333 determine the magnitude of the current passing through each of the on transistors when the transistors are on. That is, the value of the resistor 333 is changed to flow a set current of 1 mA, 2 mA, 4 mA, etc. to each transistor.

Such a resistor 333 is called a current limiting resistor 333 because the current value can be directly adjusted by connecting the resistor 333.

의 전류 제한 저항(333)이 연결되었을 때 다이오드(310)에 1mA의 전류가 흘렀다면

의 전류 제한 저항(333)이 연결되었을 때에는 2mA의 전류가 다이오드(310)에 흐르게 된다. 이후에도 상기 저항(333)값을 더 작게 하여 연결하면 더 큰 전류값들을 얻을 수 있다.for example,

If a current of 1 mA flows in the diode 310 when the current limiting resistor 333 of

When the current limiting resistor 333 is connected, a current of 2 mA flows in the diode 310. Subsequently, if the resistance 333 is smaller and connected, larger current values can be obtained.

Meanwhile, the gray scale representation unit 330 may further include a plurality of OP amplifiers 334 for amplifying the differential voltages of the two input terminals. In this case, the output terminals of the OP amplifiers 334 are connected to respective gate ends of the plurality of transistors, and one of the two input terminals of the OP amplifiers 334 is connected to the gray control unit 320, and the other is a predetermined reference voltage. It is connected to each of the reference voltage generator for applying a.

The gray control unit 320 receives an image signal and generates a gray level of the image signal. Also, as described with reference to FIG. 2, the gray control unit 320 may turn on the offset transistor 332 of the gradation display unit 330 to allow the offset current to flow even when the gradation level of the image signal is zero. Switching control.

Preferably, the gray control unit 320 separates the received image signal by R, G, and B to generate gray level by R, G, and B, and among the plurality of transistors included in the gray representation unit 330. In addition to the offset transistor 332, switching control is performed such that transistors corresponding to the number of bits of the gradation level for each of R, G, and B are turned on. Therefore, applying the present invention to a projection system such as a projection TV, it is possible to express the gradation of a color image quickly and accurately.

4 is a detailed block diagram of FIG. 2 using BJT.

The gray scale display unit 430 includes an offset transistor 432 for passing the offset current of the diode 410. That is, in FIG. 4, the transistors may be divided into a gray scale transistor 431 and an offset transistor 432.

At this time, the gray scale transistors 431 need as many as the number of bits of the gray level. In addition, predetermined resistors 433 included in the gray scale display unit 430 are connected in series to each of the plurality of transistors 431 and 432. These resistors 433 determine the magnitude of the current passing through each of the on transistors when the transistors are on. That is, the resistance value is changed so that a set current of 1 mA, 2 mA, 4 mA, etc. flows through each transistor.

In this case, the resistance 433 is also referred to as a current sensing resistor 433, which is called a current sensing resistor because the value of the current flowing through the diode 410 can be inferred from the voltage applied to the resistor 433.

의 전류 센싱 저항(433)이 연결되었을 때 다이오드(410)에 1mA의 전류가 흘렀다면

의 전류 센싱 저항(433)이 연결되었을 때에는 2mA의 전류가 다이오드(410)에 흐르게 된다. 이후에도 저항(433)값을 더 작게 하여 연결 하면 더 큰 전류값들을 얻을 수 있다.for example,

If a current of 1 mA flows in the diode 410 when the current sensing resistor 433 of the

When the current sensing resistor 433 is connected to the current of 2mA to the diode 410. Afterwards, when the resistance 433 is connected with a smaller value, larger current values can be obtained.

However, in the gray scale display device using the FET of FIG. 3, the OP amplifiers AMP are connected only for voltage amplification and the current value is directly obtained by connecting the resistor 333. However, in the case of using the BJT of FIG. The difference is that the op amps have feedback, so they get the current through this feedback.

Meanwhile, the gray scale representation unit 430 may further include a plurality of OP amplifiers 434 that amplify the differential voltages of the two input terminals. At this time, the output terminals of the OP amplifiers 434 are connected to base ends of the plurality of transistors, one of the two input terminals of the OP amplifiers 434 to the gray control unit 420, the other is already Connected to each stage. In this way, the input terminal of the OP amplifier and the emitter terminal of the transistor are connected to form a feedback circuit.

The gray control unit 420 receives an image signal and generates a gray level of the image signal. In addition, the gray control unit 420 controls the switching so that the offset transistor 432 of the gray scale display unit 430 is turned on even when the gray level of the image signal is zero.

 Preferably, the gray control unit 420 separates the received image signal by R, G, and B to generate gray level by R, G, and B, and among the plurality of transistors included in the gray representation unit 430. In addition to the offset transistor 432, switching control is performed such that transistors corresponding to the number of bits of the gradation level for each of R, G, and B are turned on.

The components of the video signal are not limited to R, G, and B, and may be selectively applied to various video components according to embodiments.

5 is a flowchart of a gradation representation device according to the present invention.

First, a predetermined voltage is constantly applied to the input terminal of the diode (500). In this case, the predetermined voltage is at least a bias voltage that allows at least the offset current of the diode to flow.

Next, the image signal is received and a gray level corresponding to the image signal is generated (510).

Finally, the switching means corresponding to the number of bits of the gradation level among the plurality of switching means included in the gradation representation part is turned on (520).

6 is a detailed flowchart of FIG. 5.

First, a predetermined voltage is constantly applied to the input terminal of the laser diode (600). At this time, the predetermined voltage is at least a bias voltage that allows the offset current of the laser diode to flow.

Next, an image signal is received (610).

When the video signal is received, the video signal is separated by R, G, and B, and a gray level of the video signal is generated by R, G, and B (620).

When the gray level of the image signal is generated for each of R, G, and B, at least one of the switching means connected in series with the laser diode is turned on to pass the offset current of the laser diode (630). This process is necessary to conduct the laser diode. Preferably, this process 630 is a process of passing the offset current of the diode by turning on at least one of the switching means even when the gray level of the image signal is zero.

Next, among the plurality of switching means connected in series with the laser diode, each of the switching means corresponding to the number of bits of the gradation level for each of R, G, and B is turned on (640). Through this process 640, the projection system is connected to the operation of the optical system for each color of the image signal to scan a color image on the screen.

Preferably, the laser diode is finally cooled. Laser diodes, light emitting diodes, and the like emit light and heat according to the flowing current. At this time, the operating characteristics of the diode may be changed by the stored heat. Therefore, a process of cooling the laser diode is required for stable operation.

7 is a graph showing the light output-current characteristics of a laser diode.

In FIG. 7, the laser diode LD exhibits a property in which the flowing current is directly proportional to the light output. Light emitting diodes (LEDs) also have similar light output characteristics. Therefore, as in the present invention, it is possible to accurately correspond to the increase / decrease of the light output by the diode according to the on / off of the switching means.

)에 따라 다이오드의 광출력 특성이 변화하므로, 다이오드의 온도를 일정하게 유지하기 위한 수단 또는 과정이 필요하다. In addition, as shown in FIG.

Since the light output characteristics of the diode change according to), a means or process for maintaining a constant temperature of the diode is required.

The light emitting means in the present invention is not limited to a light emitting diode or a laser diode, and various light emitting means may be selectively applied according to an embodiment.

Preferably, a program for executing the gradation representation method of the present invention on a computer can be recorded on a computer-readable recording medium.

The invention can be implemented via software. When implemented in software, the constituent means of the present invention are code segments that perform the necessary work. The program or code segments may be stored on a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary and will be understood by those of ordinary skill in the art that various modifications and variations can be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the present invention, by configuring the gradation display apparatus by determining the number of switching means connected in parallel according to the number of bits of the gradation level, the effect of expressing gradation accurately and quickly by using the minimum switching means have.

Claims (5)

In the gradation display device, Light emitting means for emitting light of brightness proportional to the magnitude of the current; A gradation representation unit for controlling the switching of the switching elements corresponding to the number of bits of the gradation level to determine the gradation of light emitted from the luminescent means by changing the amount of current flowing through the luminescent means; And a gray control unit configured to receive an image signal, generate a gradation level for each image component of the received image signal, and control switching switching means corresponding to the number of bits of the gradation level. The method of claim 1, And the gradation display unit is a plurality of switching means for passing the current set by the switching control, respectively, and connected in parallel. The method of claim 2, The gray scale expression unit, A plurality of OP amplifiers for amplifying the differential voltages of the two input stages; And A reference voltage generator for applying a predetermined reference voltage to one of two input terminals of the OP amplifiers; And a field effect transistor (FET) connected to the output terminal and the gate terminal of the OP amplifiers and controlled by a gray control unit. The method of claim 2, The gray scale expression unit, A plurality of OP amplifiers for amplifying the differential voltages of the two input stages; And And a bipolar junction transistor (BJT) connected to the output terminal and the base terminal of the OP amplifiers and controlled by the gray control unit. In the gradation expression method, Constantly applying a predetermined voltage to an input terminal of the light emitting means; Receiving an image signal and generating a gradation level corresponding to the image signal; And And switching the switching means corresponding to the number of bits of the gradation level to determine the gradation of light emitted from the light emitting means.

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