DE10138005A1 - Display device esp. for vehicle, uses control device for establishing control variables relative to measured non-control variable - Google Patents

Abstract

A display device comprises a colored, flat display (2) and a device (14) for controlling the display. The control/drive device (14) is designed for compensating for unwanted color shifts for establishing control/drive variables in relation to at least one measured, non-control/drive variable. An Independent claim is given for (A) a drive/control device for the display and (B) for a method for driving/controlling a display especially for vehicle.

Description

The invention relates to a display device according to the Preamble of claim 1, control means for a Display device and a method for the control a display device according to the preamble of Claim 12.

State of the art

It is known to backlight from Liquid crystal displays, control panels, dials Electroluminescent foils or LEDs (light emitting Diodes).

In addition, indicators are introductory significant type, e.g. B. in the form of colorable Liquid crystal displays in driver information systems such as For example, instrument clusters are already known.

With the combination of differently backlit colored ads, e.g. B. in the form of a dial and one flat screen often occur unwanted Color differences.

Object and advantages of the invention

The invention is based, if possible defined color rendering for color-capable advertisements to reach.

This object is achieved by the features of claims 1, 11 and 12 solved.

In the subclaims are advantageous and expedient Developments of the invention specified.

First of all, the invention is based on a display device for especially a vehicle that has a colorable, in particular flat display, hereinafter also with display referred to, and comprises means for driving the display. The essence of the invention is that the Control means for compensation of unwanted Color shifts to determine control variables in Dependence on at least one measured non- Control variable of the display device are designed. As Non-control variable is in the sense of the invention for example the temperature in the area of the display or a backlight for the display, the operating time a backlight or the display or the Light intensity for a color filter color of the display defined control mode understood, provided color filter for Come into play. This is regularly e.g. B. at TFT-driven liquid crystal displays the case (TFT = thin film transistor).

This approach was based on an accurate Analysis of causes that indicate a color shift color-capable flat displays, e.g. B. TFT screens May have consequence.

First of all, when designing color displays, this is the point make sure that these are adapted to the desired color locations. This is of particular interest when combined with other colored displays, such as dials or the like is intended.

Another category of causes can be through an adjustment the display during the manufacturing or assembly process the desired color location can be compensated. Let her through tolerances of the illuminants and the color filters for the Display and tolerances of the transmission behavior z. B. of Compensate liquid crystal in liquid crystal displays.

With the procedure according to the invention, color shifts caused by the causes mentioned can be compensated for during operation. In addition, however, color shifts can be corrected, which have the following causes and have previously been accepted:
Color shifts in the illuminants of the display when backlighting is used, e.g. B. depending on the state of aging, the temperature, the current through illuminants of the backlight or, for example, in the case of LC displays, color shifts which are dependent on the temperature, aging or the cell voltage driven on average.

That is, it is now with the present invention possible, color deviations at least partially compensate that cannot be compensated in advance because they are time-varying.

In a particularly preferred embodiment of the invention the control means comprise a light sensor Light intensity measurement, optically with the display area of the display is connected. For example, get one light sensor arranged next to the display above Coupling agent light from the display surface of the display. So that the light intensity for z. B. the color filter colors a flat display with color filter at given Control conditions measured and compared with setpoints be in the given control conditions per se should occur. If there is a difference correction data for the control can be determined from this with which the color rendering of the display allows predefined conditions to be adjusted in situ, so to speak.

The same effect can be achieved if the Control means as in the display area of the display built test field next to the display area of the display comprise, which is optically connected to a light sensor.

There are many elements of a display device temperature dependent. One can already in advance Color shift of the display depending on the temperature determined and correction data derived therefrom, which in the Operation of the display at the respective temperature Application come. However, this requires that the Control means for at least one temperature sensor Detection of the temperature of one Display device element, such as. B. the display that Backlighting, etc. or the surrounding area.

• a) der Dunkelstrom eines Lichtsensors durch eine zusätzliche Messung der Anzeige im Schwarzzustand rechnerisch eliminiert werden kann;
• b) die Empfindlichkeitsdrift eines Lichtsensors, z. B. einer Fotodiode durch eine Normierung der Messwerte beseitigt werden kann (als Normierungsgröße kann z. B. die Addition der einzelnen Farbintensitäten dienen);
• c) regelmäßig bei flachen Bildschirmen zum Einsatz kommende Farbfilter, z. B. Mosaikfarbfilter, eine gute Langzeitstabilität besitzen.

In a further preferred embodiment of the invention, it is preferred if the control means are designed to determine the light intensity for at least two color filter colors of the color-capable display and to compare them with target values for the light intensity of the respective color filter color, and on the basis of this comparison corrected control variables for to determine the respective color representation. In the case of a liquid crystal display with a color matrix and broadband (white) backlighting, any colors can be shown on the display in a wide range. With such an arrangement, a measurement of the color location of the display can be carried out with the aid of a light sensor (for example a photodiode) which is arranged over a defined display area. For this purpose, the colors of the color filter, for. B. red, green and blue, and each set the light intensity, for. B. determined via the photocurrent of the photodiode. The "actual color location" of the display determined in this way can now be compared with a target value which was determined at the time of the design or via a reference measurement during production. The color of the display can then be corrected in such a way that the color deviation is eliminated or greatly reduced. Such a procedure for correcting the color location is generally comparatively long-term stable, since

• a) the dark current of a light sensor can be mathematically eliminated by an additional measurement of the display in the black state;
• b) the sensitivity drift of a light sensor, e.g. B. a photodiode can be eliminated by normalizing the measured values (e.g. the addition of the individual color intensities can serve as a standardization variable);
• c) color filters used regularly on flat screens, e.g. B. mosaic color filters, have good long-term stability.

A dependency when comparing an actual color locus with the target color location from the ambient lighting largely to switch off, it is further proposed that the Display means when determining the intensity for a Color filter paint are designed from the measured Intensity for the color filter color is the light intensity of the Subtract the display in black.

For a simple correction of the color representation of an advertisement it is further proposed that the Display means for the generation of a correction vector the comparison of intensities determined from measurements for Color filter colors and intensity setpoints for these colors are designed.

In a further preferred embodiment, the Display means designed for an iterative color locus adjustment make. This allows the color locus of the display to be combined in one Control process to be gradually approximated to setpoints.

A color scheme has the advantage of being very long-term stable and reliable, even without the System parameters are known exactly.

However, there can also be computational compensation made without a light sensor that if it's over the active area of an ad, this area is reduced or the visual appearance of the Display may be adversely affected.

In the case of arithmetic compensation, it is proposed that the control means comprise at least one memory or to be connected with one in which related values for non-control variables, Correction data for the control and data for the desired Color are filed so that based on at least one measured non-control variable and a desired color for the most exact approximation of this color correction data can be removed for the control. In a memory of Control means can entire characteristic fields for Color shifts can be filed, e.g. B. color shifts of Display depending on the temperature, the running time of the Display, the current through backlight or like.

• 1. schwarz (S)
• 2. rot (R)
• 3. grün (G)
• 4. blau (B).

In a method for the control of a display device for vehicles in particular with a color-capable, in particular flat display and control means for the display, the main idea of the invention is that control variables of the control means based on measured non-control variables, such as. B. the display temperature, the light intensity for color filter colors of the color display, etc. can be determined. Preferably, the respective intensity of an area of the display area of the screen or of a secondary test field is measured sequentially with predetermined control variables for at least two color filter colors of the screen and compared with target values for the intensity of the respective color representation. Depending on the difference between the values determined from the measurement and the target values, correction data for the control are generated in order to be able to achieve the target values as far as possible. With this correction data, other mixed colors can then be set more precisely. For example, in a small edge area of the display, so to speak in a test field, for z. B. A color sequence is preferably cyclically represented as follows for a few 100 ms:

• 1. black (S)
• 2. red (R)
• 3. green (G)
• 4. blue (B).

The intensity of these colors (light intensity) can e.g. B. can be determined with a photo sensor, resulting in the raw values R ₀ , G ₀ and B ₀ for the intensity of the color components red, green and blue. The intensity value for a black-switched display area, the so-called black value (S), is preferably subtracted from the measured light intensities in order to be able to compensate for external light influences and the limited contrast of the display. The values R _m , G _m and B _m corrected from this, from which a current color location of the display can be determined, can be compared with target values R _s , G _s and B _s for which the colors of the display meet the requirements (e.g. B. a specification). Correction data are then created from the comparison, e.g. B. a correction vector, on the basis of which control data for which the desired color should actually result are corrected so that the desired color is then actually essentially achieved. Such a color correction can be carried out either for the entire color range of the display or only for selected display colors. If the correction works across the entire color range, all color specifications must be in z. B. an imaging software can not be changed to actually be able to largely achieve the desired colors.

In a preferred embodiment it is proposed Repeat this correction process so often until the intensity values determined from the measurement in one Tolerance range around the required intensity setpoints lie.

In a further particularly preferred embodiment of the Invention is intended to achieve an intended Color setting of the display at least one non- Control variable, e.g. B. the temperature of the display, measured and based on previously stored values for certain Color settings for different non-control variables Control data determined. This corresponds to the one above specified procedure, with which data from before determined characteristic curves or fields for a correction be used.

drawings

Several embodiments of the invention are in the following drawings with further advantages and Details explained in more detail.

Show it

Fig. 1a shows a detail of a partially sectional side view of a display device shown schematically,

Lichtauskoppelmittel schematically illustrated Fig. 1b, as they are used in Fig. 1a, in a somewhat more detailed sectional view,

Fig. 2 is a block diagram of a color control with light sensor and

Fig. 3 is a block diagram for a mathematical correction of the colors of a display.

Description of the embodiments

FIG. 1 a shows a display device 1 which comprises a TFT-addressed liquid crystal display 2 . A light guide 3 is arranged on the rear side thereof, into which light from a fluorescent tube 4 is laterally coupled. For color display, the liquid crystal display 2 comprises, for example, a mosaic color filter 5 with individual color filter areas in the colors red, green and blue. At an edge of the display, light (symbolically represented by two arrows 6 ), which passes through the liquid crystal display 2 and exits on the display surface 23 , is passed on to a photosensor 8 via a deflection prism 7 .

For this purpose, the deflection prism 7 has mirrored side surfaces 9 , 10 (see FIG. 1b) and a translucent coupling window 11 and a translucent decoupling window 12 . The remaining boundary surfaces of the prism 7 are preferably designed to absorb light. This ensures that the measured color characteristic corresponds approximately to that of normal vertical viewing (reduced solid angle).

The display device 1 with photosensor 8 can also be found in the schematic block diagram according to FIG. 2, on the basis of which the color control process is to be explained.

Light 6 , which passes through the liquid crystal display 2 and arrives at the photosensor 8 , generates an electrical signal there, which is processed in a filter and amplifier unit 13 and passed on to a computer unit 14 (microcontroller).

The computer unit 14 takes over the color control and the control of the liquid crystal display 2 for displaying desired color images.

The computer unit 14 carries out a color control process, which is symbolized by the blocks indicated by arrows in the computer unit 4 .

For the color control process, the computer unit 14 processes a color control algorithm 15 , in which, as already described above, the color filter colors of the mosaic filter 5 of the liquid crystal display 2 are shown sequentially and their intensity is determined. In addition, a black value and a white value can be determined. With the black value z. B. Eliminate ambient light influences. By comparing the individual intensities with known target values of the color filter colors, the color control algorithm creates a correction vector 16 for the color shift of the color filter colors, the vector elements for the colors red, green and blue being indicated by boxes 17 , 18 and 19, for example. With the aid of the correction vector 16 , a corrected color palette is created. This means that for a predetermined number of n individual colors C ₁ to C _n , the respective RGB values R ₁ , G ₂ , B ₁ to R _n , G _n , B _n in a color look-up table (CLUT) 20 filed with matrix elements 21 for the RGB values (intensity values for the colors red, green and blue). In this way, control software can easily work with the address in the look-up table for the colors C ₁ to C _n without the exact RGB values having to be specified in control software. The accessibility of the software to the color look-up table 20 is illustrated by the "box" 22 . The color control algorithm continuously adjusts the RGB values by calculating a correction vector in such a way that the colors actually displayed on the liquid crystal display largely correspond to the desired colors.

Fig. 3 shows a schematic block diagram of a color matching without the use of a color control algorithm.

Rather, data is determined here in advance for the fluorescent tube 4 and the liquid crystal display 2 as a function of the temperature in the region of the liquid crystal display or the fluorescent tube, with the aid of which it is possible, with knowledge of the current temperature and e.g. B. the parameter for pulse width modulation to control the fluorescent tube and the liquid crystal display so that for this current temperature with the liquid crystal display 2 colors can be displayed that correspond to the desired colors. This requires at least one temperature sensor 30 in the area of the liquid crystal display 2 and a device 31 for specifying data H ₁ to H _n for the pulse width modulation of the backlighting. In a first correction range for z. B. evenly spaced temperature values T ₁ to T _n pulse width modulation data a ₁₁ to a _nm filed. The pulse width modulation control data a ₁₁ to a _1m are, for. B. used when the temperature sensor measures a temperature that falls within a predetermined range of fluctuation around the temperature T ₁ .

In addition, there is a second correction area 33 , in which correction data for the RGB values of the liquid crystal display are stored as a function of successive temperature values T ₁ to T _n . At a measured temperature that falls within a predetermined fluctuation range around the temperature T ₁ , the correction vector b _{1 is} used to obtain desired color representations on the liquid crystal display 2 . Taking into account the data from the correction area, the matrix elements 35 for RGB values are again defined in a color look-up table 34 , as shown symbolically in FIG. 2.

In control software, it is therefore sufficient to simply specify the address of a color in the color look-up table, without the need to know more precise RGB values in the software. If the address is addressed, the corresponding RGB values, e.g. B. R ₁ , G ₁ , B ₁ read and used to control the liquid crystal display. The accessibility of the software is symbolically represented by the "box" 37 . However, the RGB control values are continuously recalculated depending on the temperature. The desired color then results not only from reading the corresponding RGB value, but also from the correct specification of pulse width modulation data for this temperature.

The use of a look-up table either for the color control process or compensation, in which e.g. B. the temperature is taken into account, has the additional advantage that, for example, an 8-bit word is sufficient for 256 colors to be able to specify 256 colors in the control software , which enables a considerable saving of storage space.

Claims (16)

1. Display device for in particular a vehicle, comprising a color-capable, in particular flat display ( 2 ) and means ( 14 ) for controlling the display, characterized in that the control means ( 14 ) for the compensation of undesired color shifts for determining control variables as a function of at least a measured non-control variable are designed. 2. Display device according to claim 1, characterized in that the control means ( 14 ) have a light sensor ( 8 ) for measuring the strength of light, which passes through the display ( 2 ) and which is optically connected to the display surface ( 23 ) of the display ( 2 ) communicates. 3. Display device according to claim 1 or 2, characterized in that the control means comprise a test field constructed like the display ( 2 ) in the region of the display area ( 23 ) next to the display area ( 23 ) of the screen ( 2 ), which is optically equipped with a light sensor in Connection is established. 4. Display device according to one of the preceding claims, characterized in that the light sensor ( 8 ) via light decoupling means ( 7 ) receives light from the display surface ( 22 ) of the display ( 2 ). 5. Display device according to one of the preceding claims, characterized in that the control means ( 14 ) have a temperature sensor ( 30 ) for detecting the temperature in the region of the display ( 2 ). 6. Display device according to one of the preceding claims, characterized in that the control means ( 14 ) are designed to determine the light intensity for at least two color filter colors of the color-capable display ( 2 ), to compare with target values for the light intensity of the respective color filter colors and on the Determine correction control variables for the display of colors on the display ( 2 ) on the basis of this comparison. 7. Display device according to one of the preceding claims, characterized in that the control means ( 14 ) in the determination of the intensity for a color filter color are designed to subtract the light intensity of the display ( 2 ) in the black state from the measured intensity for the color filter color. 8. Display device according to one of the preceding claims, characterized in that the display means ( 14 ) are designed to generate a correction vector ( 16 ) from the comparison of light intensities determined from measurements for color filter colors and intensity setpoints for these colors. 9. Display device according to one of the preceding claims, characterized in that the display means ( 14 ) are designed to carry out an iterative color location adjustment. 10. Display device according to one of the preceding claims, characterized in that the control means ( 14 ) comprise at least one memory or are connected to one in which related values for non-control variables, correction data for the control and data for the desired color are stored , so that correction data for the control can be obtained on the basis of at least one measured non-control variable and a desired color for the most exact approximation of this color. 11. Control means for a display device according to a of the preceding claims. 12. A method for controlling a display device for vehicles in particular with a color-capable, in particular flat display ( 2 ) and control means ( 14 ) for the display, characterized in that control variables of the control means ( 14 ) are determined on the basis of measured non-control variables , 13. The method according to claim 12, characterized in that with predetermined control variables for at least two color filter colors of the display ( 2 ), the respective light intensity of a display area of the display ( 2 ) or an adjacent test field is measured sequentially and compared with target values for the intensity of the respective color representation and that depending on the difference between the values determined from the measurement and the target values, correction data for the control are generated in order to be able to achieve the target values as far as possible. 14. The method according to claim 12 or 13, characterized characterized that the correction process repeats so often until the intensity values determined from the measurement in a tolerance range around intensity setpoints. 15. The method according to any one of the preceding claims 12 to 14, characterized in that when determining from of the measurement determined intensity values of the respective A black value is subtracted. 16. The method according to any one of the preceding claims 12 to 15, characterized in that to achieve a intended color setting of the display at least one Non-drive quantity is measured and that based from previously stored values for certain color representations with different values of non-control variables Control data determined and available for control be put.