DE19721984C2 - monitor - Google Patents

Description

The invention relates to a monitor with a picture tube, a video amplifier and a focus and deflection unit Generation, focusing and deflection of an electron of the picture tube.

In US-A 5,253,281 there is an X-ray diagnostic device described, which has a monitor by a how dergaberschaltung, in the playback parameters digitally entered are, an analog video signal is supplied. The like monitors have a video amplifier at their input ker, whose output signal from the electron gun Picture tube is used as control voltage to get the Current of the electron beam depending on the gray scale value of the bil to regulate that. The electron beam writes the picture down the screen of the picture tube.

The luminance of the pixel depends non-linearly the current-voltage characteristic of the electron gun and of possible non-linearities of other components of the Moni tors, for example the video amplifier and the phosphorre sponse of the fluorescent screen. However, a so-called called equality of gray values in the perceived NEN brightness (perceptual linearization), with which the number perceived grayscale can be maximized. In order to the diagnostic performance is optimized.

From this aspired equality results in Framework of models for the human visual system tuned function for the relationship between input signal and displayed monitor luminance. That relationship will but i. a. not met by the monitor under consideration. To si ensure that the display curve of the monitor of the pre Function follows, is either by software or by  Hardware a look-up table (LUT) in the digital part of the Mo nitor controlling computer provided. This LUT is now hanging depending on the brightness and contrast setting of the monitor, which in turn differs depending on the ambient brightness to get voted.

Applications are also conceivable where the representation of the Gray values determined depending on the input signal of one predetermined function follows that of the respective application depends. For example, there are different display curves that the Luminance as a function of the digital gray value on the Moni represent gate entrance, on the one hand for chest images on the other hand, conceivable for mammograms. Different dis play curves are also for different viewers (users) imaginable.

The advantages of setting the monitor characteristic using LUT, in contrast to the approximate iterative setting using brightness and contrast controls, are:

• - This procedure is available within the Number of bits exactly,
• - Even at low luminance and relatively high levels Practice lighting can ensure the correct setting become steady
• - Through this procedure, the entire system and not only a component such as the electron gun be taken into account.

In US 5,253,281 an X-ray diagnostic device is wrote, in which in the image processing circuit Look-up table (LUT) is provided. In this LUT is as Ab the characteristic relationship between the dif stored reference video signal.

From JP 1-212983 A is a circuit for contrast enhancement kung known, in which the maximum and minimum value of a Vi deosignales is evaluated. Based on this evaluation  generates a control signal which is fed to a LUT circuit in which a dependency on the image signal is assigned characteristics is included. Using the LUT circuit the image signal is raised such that an optimal con is given. Then the signal is analog Video signal fed to the monitor.

The invention is based on the task of the monitor in this way train that the respective in a simple and safe manner correct or desired display curve can be set in the monitor and the LUT in the luminance range to be set is tunable that even for low luminance the goal curve is achievable.

The object is achieved in that the Mo nitor still has a video memory and one attached to it has closed LUT circuitry with a Digital / analog converter is connected to which the videover is more connected, the LUT used depending depending on the ambient brightness. By the idea of the invention, including the video memory a certain number of predetermined LUTs and the Di Integrate digital / analog converter (DAC) into the monitor, can set the correct display curve to simple Way because the monitor has "more intelligence".

A slight adjustment can be made if the monitor has one LUT memory, in which various look-up tables stores are. An automatic consideration of the space Brightness can occur when the monitor illuminates the room sor, which is connected to the LUT memory in such a way that he added the due to the measured illuminance select the appropriate look-up table from the LUT memory. Leave it intermediate values are formed, so that look-up tables are saved can be if the LUT circuitry is a scarf device arrangement for interpolation is assigned.  

The object is also achieved by a method according to the invention in that a look-up table for implementing luminance values in the luminance range to be set L _min ≦ L einz L _{max can be selected} as a function of the ambient brightness.

According to the invention, a transformation can be carried out by the look-up table according to the following equation:

G → G ₀ + (100 - G ₀ ) G / 100,

in which

G ₀ = L _Z ^-1 (L _min )

is, and / or

L _Zr (G) = L _Z (G ₀ + (100 - G ₀ ) G / 100).

It has proven beneficial if the lighting strength of the surroundings of the monitor is measured because of an associated look-up for the measured illuminance Table is selected with which the gray values of the digital Input signals of the monitor are implemented, and that the converted signal after an analog / digital conversion Controls the brightness of the monitor. Intermediate values can be used formed by interpolation from neighboring look-up tables become.

The invention is based on in the drawing illustrated embodiments explained in more detail. It shows gene:

Fig. 1 is an X-ray diagnostic device having an imaging system,

Fig. 2, an image system and a monitor according to the prior art,

Fig. 3 shows an inventive monitor with an image system and

FIGS. 4 and 5 characteristic curves to illustrate the invention.

In FIG. 1, an X-ray diagnostic device is illustrated with egg ner X-ray tube 1, which is operated by a high-voltage generator 2. The x-ray tube 1 emits an x-ray beam 3 , which penetrates a patient 4 and falls on an x-ray detector 5 according to the transparency of the patient 4 .

The x-ray detector 5 converts the x-ray image into electrical signals, which are processed in a digital image system 6 connected to it and fed to a monitor 7 for reproducing the x-ray image. The digital image system 6 can have processing circuits, converters, differential stages and image memories in a known manner.

In such an X-ray diagnostic device, the X-ray detector 5 can be a solid-state image converter, for example made of amorphous silicon (aSi: H), or an X-ray image intensifier with a coupled television camera, which can have a television recording tube or a CCD image converter. However, it can also be used from a DLR image plate or a film / film system that is subsequently digitized. In the case of DLR or film / film, a reading device for imaging plates or a film developer and digitizer are required in a known manner between detector 5 and image system 6 .

Fig. 2 shows a structure of the monitor 7 and the image system 6 according to the prior art. The images stored and processed in an image memory 8 of the image system 6 , for example X-ray images, are read out and temporarily stored in a video memory 9 . The digital video signals are implemented in a digital / analog converter (D / A converter 10 ) and fed to the monitor 7 . In a video amplifier 11 , the analog video signal is amplified and fed to a focus and deflection unit 12 for generating, focusing and deflecting an electron beam of a picture tube 13 connected to the unit 12 .

In Fig. 3, an inventive monitor 7 is Darge. The X-ray images stored in the image memory 8 of the image system 6 are read out and temporarily stored in the video memory 9 arranged in the monitor 7 . The digital video signals are implemented in a look-up table for transforming the gray values (LUT circuit arrangement 14 ), digitized in the D / A converter 10 and fed to the video amplifier 11 . The amplified analog video signal is fed to the focus and deflection unit 12 of the picture tube 13 .

An ambient light sensor 15 arranged in the monitor 7 measures the illuminance prevailing at the location of the monitor 7 , on the basis of which a look-up table is selected from an LUT memory 16 and supplied via a circuit arrangement 17 for interpolation of the LUT circuit arrangement 14 .

The integration of video memory 9 and D / A converter 10 in the monitor 7 ensures that the LUTs used for display, which depend on the properties of the monitor 7 , and the monitor 7 represent a physical unit.

The following components or steps are required for this (see Fig. 1):

• 1. The ambient light sensor 15 arranged in the monitor measures the illuminance prevailing at the location of the screen.
• 2. The video memory 9 , for example a VRAM, and the D / A converter 10 , which converts the digital image signals coming from the image memory 8 into the analog video signal, are integrated in the monitor 7 .
• 3. Furthermore, a certain number N of look-up tables with 2 ^M entries each (e.g. M = 12) is:
  f _k ⁽ⁱ⁾ ; i = 1, ..., N; k = 0, ..., 2 ^M - 1
  saved to transform the gray values. The index i can be used to denote various predefined ambient brightnesses or different applications. The LUTs are determined before commissioning the monitor 7 in dependence on the illuminance, ie depending on the output signal of the ambient light sensor 15 and / or the desired application.
• 4. The monitor system also includes a circuit arrangement 17 for interpolation. B denotes the measured at a gege surrounded illumination output of the light sensor 15 in order to be the values of an LUT (f _k) determined by the following interpolation:
  f _k = f _k ⁽ⁱ⁾ (1 - p) + f _k ^{(i + 1)} p
  with p = (B - B _i ) / (B _{i + 1} - B _i ),
  where B _i and B _{i + 1} denote the adjacent previously measured um light sensor signals and f _k ⁽ⁱ⁾ and f _k ^{(i + 1)} denote the associated values of the LUTs. This linear interpolation is only to be understood as an example. Any other type of interpolation, for example with cubic or quadratic functions or with spline functions, is also conceivable.
• 5. The monitor system includes a device for applying the LUTs to the digital input gray values G _k with the result that the output gray values G _k ', which represent the input for the D / A converter 10 , provide exactly the desired display curve :
  G _k '= f _k (G _k ).
• 6. The D / A converter 10 transforms the digital gray values into an analog voltage video signal.
• 7. The monitor 7 transforms this video signal into a luminance image using the known monitor technology.

Before starting up, the look-up tables to be used certainly. The following procedure is used:

Given the target display curve L _Z (G), which follows from a perceptual linearization model or is suitable for a specific application, where G denotes the digital gray value in percent of the maximum value (e.g. 255) (0 ≦ G ≦ 100% ).

The values of L _Z (G) are defined between L _Zmin and L _Zmax , the minimum and maximum possible values L _Zmin and L _Zmax depending on the model. For example, for the standardization proposed by ACR / NEMA and described in SPIE Proceedings Medical Imaging 1996, Image Display, on pages 344 to 360, L _Zmin = 0.05 cd / m ² and L _Zmax = 4000 cd / m ² applies to the curve proposed by CIE, described in DIN 5033, Part 3, July 1992, applies L _Zmin = 0 and L _Zmax = L _max , where L _max denotes the desired maximum _luminance . Accordingly, L _{min is} the minimum luminance to be set. These two target curves are just two examples of many possible display curves.

A solution to the problem is proposed to map the area to be mapped L _min ≦ L den L _max into the corresponding area of the standard display curve.

The following transformation is carried out:

G → G ₀ + (100 - G ₀ ) G / 100, where

G ₀ = L _Z ^-1 (L _min )

applies ( Fig. 4 and 5). Then the curve poses

L _Zr (G) = L _Z (G ₀ + (100 - G ₀ ) G / 100)

the curve restricted to the range L _min ≦ L _Zr ≦ L _max for 0 ≦ G ≦ 100. In the event that L _{Z is} only given for discrete arguments, the curve L _{Z must} be interpolated accordingly.

This ensures that the monitor characteristic can be clearly corrected by means of LUT even at low luminance levels, as can be seen in FIG. 4.

The LUT f is then given by in a known manner

L _Zr (G) = L _m (f (G)), 0 ≦ G ≦ 100%,

where L _m denotes the uncorrected, intrinsic display curve of the monitor

(L _min ≦ L _m ≦ L _max ).

The LUT is therefore determined by the following equation, the curve shape of which is shown in FIG. 5:

f (G) = L _m ^-1 (L _Zr (G)).

As a rule, the calculated value of the digital gray value (0, ..., 2 ^M - 1), which corresponds to f (G), lie between two adjacent elements of the set {0, 1, 2, ..., 2 ^M - 1}. In practice, one of these two values is chosen, preferably the one with the smaller distance. The resulting quantization error is imperceptible for bit depths M ≧ 8.

The method described here is for all perceptual lineages rization models applicable. The basic idea of the invention is the treatment at low luminance and finite Ambient lighting.

With this arrangement according to the invention, a digital monitor 7 is obtained in which all the data relevant to the monitor 7 for the brightness setting are directly and permanently assigned to it, since they are stored in it itself.

Claims (11)

1. monitor ( 7 ) with a picture tube ( 13 ), a video amplifier ( 11 ) and a focus and deflection unit ( 12 ) for generating, focusing and deflecting the electron beam of the picture tube ( 13 ), characterized in that the monitor ( 7 ) further comprises a video memory ( 9 ) and an LUT circuit arrangement ( 14 ) connected to it, which is connected to a digital / analog converter ( 10 ) to which the video amplifier ( 11 ) is connected, the one used LUT is selected depending on the ambient brightness. 2. Monitor according to claim 1, characterized in that the monitor ( 7 ) has a LUT memory ( 16 ), in which various look-up tables are stored ge. 3. Monitor according to claim 1 or 2, characterized in that the monitor ( 7 ) has an order light sensor ( 15 ) which is connected to the LUT memory ( 16 ) in such a way that it illuminates the associated look due to the measured illuminance -up table from the LUT memory ( 16 ). 4. Monitor according to one of claims 1 to 3, characterized in that the LUT circuit arrangement ( 14 ) is associated with a circuit arrangement ( 17 ) for interpolation. 5. Monitor according to claim 4, characterized in that the circuit arrangement ( 17 ) interpolates for interpolation according to the following equation:
f _k = f _k ⁽ⁱ⁾ {1 - (B - B _i )} / (B _{i + 1} - B _i )} + f _k ^{(i + 1)} (B - B _i ) / (B _{i + 1} - B _i ). 6. A method for setting the characteristic curve of digital monitors according to one of claims 1 to 5, characterized in that a look-up table for converting luminance values in the luminance range to be set L _min ≦ L ≦ L _{max can be selected} as a function of the ambient brightness. 7. The method according to claim 6, characterized in that the look-up table carries out a transformation according to the following equation:
G → G ₀ + (100 - G ₀ ) G / 100, where
G ₀ = L _Z ^-1 (L _min ). 8. The method according to claim 6 or 7, characterized in that the look-up table performs a transformation according to the following equation:
L _Zr (G) = L _Z (G ₀ + (100 - G ₀ ) G / 100). 9. The method according to any one of claims 6 to 8, characterized in that the illuminance of the surroundings of the monitor ( 7 ) is measured, that on the basis of the measured illuminance an associated look-up table is selected with which the gray values of the digital Input signals of the monitor ( 7 ) are implemented, and that the converted signal controls the brightness of the monitor ( 7 ) after an analog / digital conversion. 10. The method according to any one of claims 6 to 9, there characterized by that intermediate values by interpolating neighboring look-up tables be formed. 11. The method according to any one of claims 6 to 10, characterized in that interpolation is carried out according to the following equation:
f _k = f _k ⁽ⁱ⁾ {1 - (B - B _i )} / (B _{i + 1} - B _i )} + f _k ^{(i + 1)} (B - B _i ) / (B _{i + 1} - B _i ).