JP2000163006A - Digital address specification of plane display screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a sense of an illumination level by a human as to a dark level by receiving a digital illumination instruction while a 1st electrode addresses a 2nd orthogonal electrode and making light emission intensity not constant while the 2nd electrode is addressed. SOLUTION: For the time t1 when the 1st electrode of the plane display screen addresses the 2nd orthogonal electrode, the digital illumination signal which is applied and sets pulse width is received and for the time when the 2nd electrode is addressed, the light emission intensity is made not constant. The illuminance of emitted light is not constant while the screen electrode which is scanned, line by line, is addressed. Namely, a discharging current is not constant for a line time, which therefore corresponds to variation in the intensity of the current for the address specification time of, for example, a grid line in case of a microchip screen, so that the light emission intensity can be varied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flat microchip display screen. More specifically, it relates to a flat screen where the respective lighting commands for the different elements are digitally applied to the screen electrodes.

[0002]

2. Description of the Related Art An example of a display screen to which the present invention is more specifically applied is, for example, a microchip type flat field effect screen. FIG. 1 shows a very schematic and partial view of the structure of a planar microtip screen. This screen emits electrons towards the anode electrode 2 which is separated from the cathode by the space 3,
Including the cathode electrode and the microchip 1. Grid electrodes 4 are generally combined with cathodes 1 in a vertical direction to form an electron emission array network.

An example of a microchip screen to which the present invention is applied and the principle of its implementation are described in Commisariat
USP for a l'Energy Atomicue
4,940,916.

It should be noted that the representation of FIG. 1 has been greatly simplified. In particular, this display is not intended to elaborate the structure of the microchip screen,
It is intended to distinguish between different electrode addressing potentials.
In practice, there are thousands of microchips per screen element, but FIG. 1 shows a single microchip for each element.

[0005] The anode 2 is brought to a potential _VA which is substantially higher than the cathode potential (eg a potential of several hundred volts) to attract electrons emitted by the microtip.
In a monochrome screen, the anode is permanently applied with an addressing potential. Color screens commonly use three different dye anodes that are addressed sequentially for each color frame of three different dyes (blue, green, red).

[0006] The grid electrode 4 is arranged in the row direction of the first direction, the addressing potential in line scanning, are generally biased to turn on the positive potential V _G with respect to the cathode electrode 1. The cathode electrodes 1 are arranged in a column direction in a second direction perpendicular to the first direction and are simultaneously addressed by the signals V _K and V _K ′ with the grid electrodes 4 during addressing of the grid lines, respectively. The electron emission current represents the brightness of the element determined in each grid row by the intersection of the cathode column and the grid row.

The two addressing methods of the display screen type described above can be essentially distinguished.

[0008] In the first screen scheme, the cathode electronic addressing potential represents the brightness of the element as determined by the intersection of the cathode columns and grid rows. The cathode row is like this
Between the maximum emission potential and no emission potential (e.g., 0 for each grid having an addressing potential of about 80 volts).
Volts and 30 volts).

In a second screen scheme to which the present invention is more particularly applied, the brightness is determined by the address time (pulse width addressing) of the column in question during the grid addressing time (line time).

FIG. 2 shows a cathode address finger by pulse width modulation.
One example is described very schematically in the form of a time chart
FIG. In such an addressing form,
During the addressing time t1 of the grid line 4,
All the cathode rows are signal V _KAnd V_KAdd by ´
Is specified. Each signal V_KAnd V_K´ is a pulse
And the pulse width depends on the intersection of the line and column in question.
Depends on the required brightness of the device. FIG.
In the example described by the grid electrode and the cathode electrode
High potential difference between them (for example, a 50 volt electron emission threshold)
The signal V_KBy ´
The column addressed is the signal V_KBy address finger
It has a lighting instruction larger than the specified column. in this way,
Address the display screen type column to which the present invention applies.
Lights in pulse width modulation performed to specify
Is generally the minimum pulse width. But
In order to obtain different lighting rules depending on the pulse width,
It is enough to invert the loose, at which time it is released
The principle of pulse width modulation to determine the amount of electrons
is there.

The modulation of the width of the cathode electrode addressing pulse is
It is often implemented digitally. FIG. 3 (A) and
As described respectively in FIG._K´
And I _KIs the binary word W_K'And W_KBy
It is determined. In the example shown in FIGS. 3 (A) and (B)
Therefore, the higher the required brightness, the more binary words
The numerical value represented by is also higher. (Eg columns_K1 for '
01, column_K011)

Digital addressing is particularly suitably applied to array screens where one of the electrodes is addressed by a pulse signal, the pulse width of the pulse signal determining the luminance command. In fact, this pulse-width modulation is usually performed by slicing an integer number of clock cycles, often based on a clock (dotted line in FIG. 2). This clock has a higher frequency than the pulse train frequency corresponding to the line scanning frequency.

[0013]

However, the screens of the prior art, in particular, lack the reproduction of low-definition lighting that can detect the shadow between two adjacent brightness levels in the low-lighting screen part. There are inconveniences.

It is an object of the present invention to improve the perception of the lighting level by a person at a dark level.

It is also an object of the present invention to provide a new method of digitally addressing a display screen that implements such an improvement.

The present invention also aims to provide a simple way to implement and to provide a way to minimize the traditional digital addressing variants of such screens.

[0017]

SUMMARY OF THE INVENTION To achieve these objects, the present invention is a method for digitally addressing a flat display screen configured in an array, wherein the first electrode of the flat display screen is provided. Receiving a digital lighting command applied during the time to address the second orthogonal electrode and setting the pulse width such that the light emission intensity is not constant during the time to address the second electrode.

According to an embodiment of the present invention, the non-constant change obeys a law based on the relationship of visual sensitivity.

According to an embodiment of the present invention, the invention is applied to a flat display screen in which a first electrode is formed by a field emission cathode and a second electrode is formed by a grid associated with the cathode.

According to an embodiment of the present invention, the addressing potential of the second electrode is changed during the addressing time.

According to an embodiment of the present invention, the addressing potential of a grid line increases non-linearly during a line time.

According to the embodiment of the present invention, the frequency of the pulse width modulation clock for addressing the first electrode is changed.

According to an embodiment of the present invention, the clock frequency is changed with the addressing time of the second electrode being modulo.

According to an embodiment of the present invention, the addressing potential of the third electrode is changed along with the time for addressing the second electrode.

According to an embodiment of the present invention, the third electrode is formed by cathodoluminescence.

According to an embodiment of the present invention, the addressing voltage of the first electrode is changed along with the time for addressing the second electrode.

[0027] The foregoing objects, features and advantages of the present invention will be discussed in detail in the following non-limiting description of the detailed embodiments in conjunction with the accompanying drawings.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS The same elements are denoted by the same reference symbols in different drawings. For clarity, only those elements that are necessary to the understanding of the present invention are shown in the drawings and, moreover, the time chart is not scaled.

The present invention has been devised from observation of visual sensitivity by lighting. This sensitivity is expressed almost logarithmically, not first order, ie, two adjacent gray levels are:
When it is dark, it is better distinguished from each other than when it is bright.

FIG. 4 illustrates the effect of the logarithm of visual sensitivity on digital addressing of the display screen. This figure shows the response of the sight E according to the luminance I.

In a digitally addressed screen, the luminance axis I is sliced (sampled) and encodes this luminance in binary form. In the example, it is indicated by 3 bits (8 states) or more. The non-linear visual sensitivity to brightness is such that two adjacent lighting commands (101 and 110) of high brightness are interpreted as an approaching visual response, while two adjacent low lighting commands (000 and 001). Is interpreted as a strongly different response of vision.

Further, when the non-linear visual response interprets the high sensitivity (dark level) of the vision, sampling the lighting command will result in two neighboring areas that are strongly different from each other in terms of light emission level (eg, gray level). The result is to have a matching level. As a result, the visually perceived level difference in the range of low brightness levels is larger than the accumulated level difference.

It should be noted that the problem of inconsistency between the distribution of lighting commands and the visual sensitivity occurs on screens where the lighting controls are digital in nature. In fact, on all other types of screens, such as CRTs, all required levels of gray can be displayed by analog features of the lighting control. The same applies to liquid crystal screens whose emission is controlled in an analog manner.

A feature of the present invention is to vary the light emission intensity during the scan line addressing time. Thus, according to the present invention, the brightness of the light emitted during the addressing of the line-scanned screen electrode is not constant, ie the emission current is not constant during the line time. For a microtip screen,
For example, this corresponds to changing the current intensity during the grid line addressing time.

According to the present invention, in the case of a field effect screen, the difference in light intensity amplitude, that is, the difference in the amount of emitted electrons,
Receiving two adjacent low lighting binary commands is smaller than receiving two adjacent high lighting binary commands.

FIG. 5 is a diagram for explaining the first embodiment of the present invention in the form of a time chart. Time table of FIG. 5 shows a signal V _G addressing grid lines between the line time t1, an example of a cathode column addressing signals V _K and V _{K 'during} this line time. The display of FIG. 5 is shown in FIG.
This is for comparison with the display.

[0037] According to a first embodiment of the present invention, the grid line addressing potential V _G during the selection time t1 of grid lines are analog modulated. Thus, at each line time, the potential of the addressed line is brought to a first value V0 (eg, about 75 volts), which increases to a potential V1 at the end of the line time.
(Eg, about 80 volts).

In the first embodiment, the cathode column addressing signals V _K and V _K ′ do not change with respect to the conventional case (FIG. 2).

As described above, the period during which the cathode emits electrons is the period during which the grid is at a high addressing potential and the cathode is at a low potential.

[0040] FIG. 6 (A) and (B) is, 'brightness against and _{W K, I K'} examples _{W K} of the two binary words and _{I K}
FIG. 4 is a diagram for explaining the effect of the present invention in FIG. FIG. 6 (A)
3B and 3B are for comparison with FIGS. 3A and 3B described above.

[0041] As described in FIGS. 6 (A) and (B), analog modulation of the grid voltage V _G results in a non-linear relationship between brightness and binary instructions. In FIGS. 6A and 6B, the interpolation of the average value of luminance (increasing slope) by the binary command is represented by a dotted line pnl. The non-linear shape of the interpolation pnl is for comparison with the dotted line pl in FIGS. 3A and 3B, which also represents the interpolation of the average luminance value, but is linear.

The non-linearity in the relationship between luminance and the binary command (dashed line pnl) presented by the present invention depends on the correction required to be implemented by visual sensitivity. This correction is adjusted by the shape given to the analog modulation of the grid line potential at the line time t1, and is adjusted for each application. Determination of this shape is within the skill of one skilled in the art due to the functional indications described above.

In certain embodiments, the range of line time is about 20 μs to 40 μs for a conventional microtip screen. This range is completely compatible with the modulation performed by the present invention.

FIG. 7 is a diagram illustrating a second embodiment according to the present invention. This drawing takes the form of a time chart,
During line time t1 grid line is addressed by the signal V _G, two cathode signal V _K and V _K '
Shows the shape of each.

A feature of the second embodiment is that the frequency of the modulation clock CLK having the cathode control pulse width is changed during the line time. As illustrated in FIG.
Clock signal CLK does not represent the same frequency along the line time. In the embodiment shown, this frequency increases along the line time.

In connection with FIG. 2, in the example shown in FIG. 7, the number of clock cycles provided in the line time is:
It is assumed that the lighting command applied to the cathode column corresponds to the number of states to be coded.

As illustrated in FIG. 7, the clock signal C
Pulse width modulation of the signals V _K and V _K ′ with respect to LK results in a non-linear pulse width for the same numerical interval of lighting command bits.

To achieve a change in the clock signal frequency CLK with the line time modulo, for example, a faster clock can be used, and packets of this clock are sampled more at the beginning than at the end of the line time. This means that this clock can be modulated analogously.

One advantage of the present invention is that by reducing the spacing between two consecutive lighting levels, the perception of lighting level differences in dark areas of the image is improved, thereby improving the quality of the visual image. Is to do.

Another advantage of the present invention is that it is particularly simple to implement with only minor modifications to conventional display screens for addressing circuits.

One or another embodiment described above can be selected depending on the application and the type of circuit used. Particularly when it is desirable not to change the cathode column addressing, it is preferable to use the first embodiment.
Conversely, if it is desired to maintain conventional grid line addressing, the second embodiment is selected.

Of course, it is expected that the present invention will have various alterations, modifications, and improvements which will readily occur to those skilled in the art. In particular, other means for changing the luminance during the line time can be used, provided that the above-mentioned functionality is respected. For example, the anode addressing potential can be changed with the line time being modulo. Such a change, interpreted as an anode-cathode change, causes a change in emission current and a change in brightness during the line time. For example, it may also provide for changing the cathode addressing voltage with grid line time modulo, as well as with non-constant emission current with line time modulo.

Further, while the present invention has been described in terms of a screen in which the lighting commands are adjusted by the cathode, replacing the present invention with a screen in which line scanning is performed on the cathode side is a matter of skill in the art. Within the capability range of

For further clarity, it should be noted that the present invention has been discussed in connection with the encoding of a 3-bit lighting instruction, but the number of bits is typically larger.

Further, in the second embodiment, the pulse train has a frequency at least equal to the lowest frequency of the variable frequency signal CLK, and the addressing pulse whose width can be changed can be formed from the respective pulse trains.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a conventional technique and a problem to be solved.

FIG. 2 is a diagram illustrating a conventional technique and a problem to be solved.

FIG. 3 is a diagram illustrating a conventional technique and a problem to be solved.

FIG. 4 is a diagram schematically illustrating human visual sensitivity based on luminance.

FIG. 5 is a diagram illustrating a first embodiment of the present invention in the form of a time chart.

FIG. 6 is a diagram showing luminance as a function of a binary addressing instruction according to two instructions.

FIG. 7 is a diagram illustrating a second embodiment of the present invention in the form of a time chart.

[Explanation of symbols]

1 microchip 2 electrode 3 space 4 grid electrode _{V A,} V G, V1 potential _{V K,} V _K 'signal t1 addressing time _{I K,} I _K', I luminance _{W K,} W _K 'binary word pl, pnl Interpolation of average luminance value E Visual response V0 First numerical value CLK Clock signal

Claims (10)

[Claims] 1. A method for digitally addressing a flat display screen configured in an array, wherein a first electrode (1) of the flat display screen addresses a second orthogonal electrode (4). Receiving a digital lighting command applied for a time (t1) to set a pulse width, wherein the light emission intensity is not constant during a time for addressing the second electrode. Digital addressing method. 2. The digital addressing method of a flat display screen according to claim 1, wherein the non-constant change obeys a law based on a relationship of visual sensitivity. 3. The field emission cathode according to claim 1, wherein the first electrode is a field emission cathode.
2. The method of claim 1, wherein the second electrode is applied to a flat display screen formed by a grid associated with the cathode. 4. The method of claim 1, wherein the addressing potential (V _G ) of the second electrode (4) is changed during an addressing time (t1). . 5. The digital display of claim 3, wherein during a line time (t1), the addressing potential (V _G ) of the grid line (4) increases non-linearly. Addressing method. 6. The method according to claim 1, wherein the frequency of a pulse width modulation clock (CLK) for addressing the first electrode (1) is varied. 7. The clock frequency (CLK) with the addressing time (t1) of the second electrode (4) being modulo.
7. The method according to claim 6, wherein a change of the number is performed. 8. The method according to claim 1, characterized in that the addressing potential of the third electrode (2) is varied along a time (t1) for addressing the second electrode (4). Digital addressing method for flat display screens. 9. The method according to claim 3, wherein the third electrode is formed of cathodoluminescence. 10. The method according to claim 1, characterized in that the addressing voltage of the first electrode (1) is varied along a time (t1) for addressing the second electrode (4). Digital addressing method for flat display screens.