DE2415173B2 - PROCESS AND EQUIPMENT FOR THE COLOR REPRODUCTION OF BLACK AND WHITE IMAGES VIA COLOR TELEVISION TUBES - Google Patents

Description

4. Device for carrying out the method according to claim I. characterized in that for phase modulation a known back posture (I) mil two constant resistors (21, 22) on one branch and a variable resistor (19) and a capacitor (23) on the other Branch is provided. A field effect transistor (19) controlled by the black and white signal serves as a variable resistor and the voltage (Uce) of the reference color carrier (3) is applied to one diagonal, while the phase-shifted signal (LJa) is picked up on the other diagonal.

5. Device according to claim 4, characterized in that three bridge formwork (1) to form a phase modulator (2) acting over 360 'are connected in series (F i g. B).

b. Device according to Claims 4 and 5, characterized in that the phase-shifted signal (Ua) is converted into the color difference signals (RY and BY) via two synchronous demodulators (4, 5) 5 ".

7. Device for performing the method according to claim 3, characterized in that the phase modulation (111) is preceded by a contrast intensifier (window intensifier 31).

8. Device according to claim 7, characterized in that a clamping circuit (30) is arranged in front of the contrast intensifier (31), to which a synchronous pulse generator ¹ (32) is connected which, together with the contrast intensifier,

to which the first phase modulator (2) is applied, passes on Leuehtdichiesignal (Y) directly to the color television picture tube via an Additionssicllc (33).

In order to help living people better distinguish between different types of bone structures or to distinguish between bones and soft tissues. It is known that the eye responds much better to color differences and differences in brightness after corresponding, joint reproduction and can recognize them better than when different ones of a black-and-white image are to be diagnosed. In the known method (DT-OS 13 093) one makes use of the fact. __ß Bone structures or soft tissue structures represent a certain black and white distribution in the television picture, which can be understood as a line grid, the dimension of which is a certain spatial frequency. This spatial frequency is greater, the finer the structure of the object. Depending on the spatial frequency of the black-and-white image, certain colors are assigned to the individual structures and / were due to the fact that the frequency is converted into a voltage with the help of a frequency demodulator, which assigns certain types of color to certain line densities.

The facility provided for this provides. that the alternating voltage to be demodulated via an amplifier tube is fed to a parallel resonance circuit, the resonance frequency of which is adjusted so that all occurring frequencies of the supplied alternating voltage either greater or less than that Are resonance frequency. ) e more then the supplied Frequency corresponds to the resonance frequency, the greater the alternating voltage applied to the resonant circuit, whose amplitude can be measured, so that a voltage at the output of the demodulator pending, which is approximately linear to the frequency of the supplied AC voltage in a small area. With this voltage can then either influence the brightness of one or more primary colors, it but it is also possible to use a reference color carrier known from color television technology. to influence. Of the The disadvantage of this known method is that there is only a distinction between coarse and fine Structures are shown in different colors, so it is difficult. to interpret a corresponding picture. For example, different thick bones would appear in the same color with no differences, for the brightness values are largely drowned out.

There are other methods of coloring in front of black and white images using photographic methods the known (W. Bergerhoff "Handbuch Medizinischer Radiologie", Vol. 3, Springer Verlag 1966) and c; DT-Oi 20 53 894) a black-and-white picture has already been proposed To convert images, for example to a red and ii a blue picture, which are then superimposed again. The disadvantage of such a procedure consists in the fact that the result is basically a black and white image with an upstream color filter speaks and that a black and white image appears as a negati, so that here too the desired one is not clear There is a possibility of differentiation.

It is also an arrangement as mentioned in the opening paragraph

Type known in which the amplitude of the black-and-white signal is broken down into steps and each of these steps is assigned a color that must be set beforehand according to hue and saturation (DT-CS 20 53 555). This method and the corresponding arrangement has the disadvantage that only a relatively rough subdivision is possible with an economically justifiable effort, which is possibly suitable for converting cartoons in color, but not for the conversion of, for example, X-ray images. Within the individual stages is namely in each case the same color before and it is even possible that if the Bright; itswert threshold in the vicinity of a switch located between the stages, the thus caused interference to local Farbänderun- gene from one to completely different color. For certain applications, e.g. B. in order to X-ray images for better differentiation ^: n Umzuwandein color images or other black-and-white images. For example, the known method is unsuitable for precisely resolving the scientific evaluation based on satellite images.

A low-pass filter is provided there, which is intended to avoid dall wiping / wiping on the Shah shoo malfunctions occur in the individual stages. However, this low-pass filter in turn has the disadvantage of mn that it has a cut-off frequency of 0.5 MH / for a signal with a bandwidth of about 5 MHz. That means that because of this low-pass filter there are gray-tone gradations in the black-and-white image structures that are less than '/ w line length (1 to 1.5 cm) where Reproduction via picture tubes with a diagonal of 3 cm cannot be reproduced in color.

In the known arrangement, the amplitude is also broken down with limiters. That means that the Signals black and white must also appear in the picture. So precautions must be taken that the black-and-white signal is rearranged in such a way that these two end values are also present are and remain unchanged, because otherwise the known arrangement is not functional.

In contrast, the present invention is based on the object of even the smallest differences in holy wedges to assign different colors or shades of color to the black and white image - thus a for The color image is easily evaluated by the eye - without affecting the reproduction of the smallest image structures must be dispensed with.

The invention consists in the features specified in the characterizing part of claim 1. These measures, in which the amplitude of the black-and-white television signal is used as a control for the coloring, makes it possible to use the entire color scale for the reproduction of a black-and-white image, which is not changed in its basic structure with regard to the differences in brightness. The invention therefore creates a color image which reproduces all gray tones in different color gradations and color saturations, so that even very small differences in brightness of the black and white image can be recognized by changes in the hue or in the color saturation. Since no low-pass filter has to be provided in the method according to the invention. a very fine geometric resolution of the black and white image is also possible. The method according to the invention is therefore particularly suitable for the scientific evaluation of black and white images. such as B. X-ray images, or satellite images od. The like. Suitably, there is provided television signal black and white to rotate with the amplitude of the one known from television technology reference carrier in its phase accordingly and supply it to two synchronous demodulators of the color television picture tube.

To a large extent adaptation of the color tone to the subjective characteristics of the viewer of the television picture can also be achieved in an advantageous further development of the method according to the invention still be provided, the reference color carrier arbitrarily via a further adjustable phase modulation rotate in phase so that the start and end points of the color scale are shifted as desired can be. The image area of interest can thus be placed in such a way that it coincides with the maximum Sensitivity range of the eye coincides.

In order to finally create the possibility, only one to pick out the part of the entire image that is of interest and the differences in brightness within it over the whole Sigiiiilbereich to be able to enlarge, is before the phase modulation and influencing the reference color carrier Clamped on the contrast intensifier, which separates the areas of the sacred wedge that are not of interest and only the remaining area passes so that this Subarea, in turn, can be assigned the full color range. It is thereby possible. Γιη / elheiien one different shades of gray at certain points, for example an X-ray image in an and Way to be able to divide and graduate as it is with optical means and by means of the human eye would not have been possible.

To carry out the method according to the invention and the advantageous Vcrfalircnsausgesialumgcn a circuit can be provided in which a known bridge circuit with two constant resistors on one branch and a variable resistor and a capacitor on the other branch is provided for phase modulation. A field-effect transistor controlled by the black-and-white signal serves as the variable resistor and the voltage of the vehicle is applied to one diagonal, while the phase-shifted signal is picked up on the other diagonal. Since it has been shown in practice that such an arrangement allows a perfect phase rotation only over about 120 phase angles, three bridge circuits are connected in series in an expedient embodiment to form a phase modulator acting over 360 °. The phase-shifted signal can also use two synchronous demodulators ^! into the l'arbdifferen / sig nals R- V and B-Y are converted. These signals then correspond to the color difference signals customary in color telephoto technology.

To achieve a range enhancement, the Phase modulation a contrast amplifier. a so-called Window reinforcement · can be switched on. before the contrast intensifier is then advantageously arranged a clamping circuit, which is connected to the one synchronizing pulse disconnection circuit connected. which together with the contrast enhancer on which the eiste phase modulator is applied, the luminance signal is sent directly to the color television tube via an addition point passes on. In this way, the sync pulse is before the phase modulation and range gain separated, which gives certain advantages in signal forwarding.

The invention is based on an exemplary embodiment

shown in the drawing and is in the The following description explains, It shows

F i g. 1 is a block diagram of a device for carrying out the method according to the invention,

2 shows the schematic representation of the color value signal generated by the phase modulation in the color wheel,

F i g. 3 is a block diagram similar to FIG. 1, but with the additional possibility of subjective Setting of the color ion,

F i g. 4 the circuit arrangement for generating a standard-compliant remote control signal,

F i g. 5 shows a phase modulator as used in accordance with the present invention for phase rotation of the reference color carrier is used,

F i g. 5a shows the phasor diagram for the phase modulator in FIG. 5 generated partial voltages,

F i g. 6 the combination of three phase modulators according to FIG. 5 to achieve a 30 ° phase shift.

F i g. 7 shows a circuit in which the phase modulation arrangement a clamping circuit with a contrast amplifier for range selection is connected upstream,

F i g. 8 shows the schematic representation of the circuit shown in FIG. 7 from the original black and white signal hideable area of interest and

F i g. 9 shows the representation of the black / white signal. how it is fed to the color assignment of the phase modulation device after the range selection.

In Fig. 1, a phase modulator 2 is switched on in line 1, which is connected, for example, to a television camera or to a black-and-white receiver, through which a signal BAS in the form of a black-and-white television signal is passed / ugsfarbirägcrs 3 changed, the frequency of which is selected to be 13.56MHz. The mode of operation of the phase modulator 2 will be explained in detail with reference to FIGS. 5 described. It is sufficient to explain the basic idea of the invention. that this phase modulator 2 rotates the phase of the subcarrier 3, which are then demodulated in the two synchronous demodulators 4 and 5 in the manner known from color television technology into the red and blue difference signals /? - Kund B-Y . The black-and-white input signal BAS is also fed directly via line 6 to the color television picture tube in the form of the K signal.

To understand this process, it should be briefly explained that the signals usually coming from a color television camera, Red Ur. Green Uc and blue U _{B can be} combined anologously into a brightness signal Uy according to the following equation:

Uy = 030 · Ur + 0.59 ■ U _G + 0.11 · U _B

This equation, which is derived from colorimetry, already takes into account the spectral sensitivities of the decomposition filters in the camera and the properties of the phosphors in the display device. This luminance signal Uy can also be processed properly by a black and white television set (compatibility). In addition to this luminance signal, the color information must also be transmitted. From the above equation it can be seen that it is sufficient to additionally transmit two of the three color signals, so that the color difference signals

Ur- Uy = U _R -y = 0J χ Ur-059 χ Lfc-Ol 1 χ L / _B and Us- Uy = 1 / b- _v = 03x Ur-0.59 Lfe + 0.89 Ub

are formed.

These color difference signals are transmitted in a so-called quadrature modulation by the signal Ur _, a suitably selected color subcarrier is modulated. For modulation with _{Ue y} , the same color carrier is rotated by 9 (T in its ° hase). If these two modulation products are now added vectorially, the chrominance signal Ur. Is produced, which is shown in the so-called color wheel in FIG

The phase position, ie the size of the angle φ corresponds to the color ion and the amplitude, ie the length of the vector U / the color saturation, corresponds to this chrominance signal Ui. The color difference signals Ur , and Us-y are plotted as the coordinate and abscissa and it can be seen that, depending on the size of the angle q \, which is achieved as a function of the phase modulation of the reference color carrier 3 in the phase modulator 2, the color changes as a function of the Black and white signal Y changes. For orientation purposes, the diagram in FIG. 2 the '-'arbpunkte 7,8,9, 10, 11 and 12 known from the color hexagon are entered, where 7 is the color magenta. 8 red, 9 yellow, 10 green. 11 corresponds to cyan and 12 corresponds to the color blue. With a 360 ^c rotation of the phase of the reference color carrier 3, depending on the amplitude of the V signal (BAS), a specific chrominance signal Cf can be assigned to each brightness value, specifically over the entire color scale. This enables a black-and-white image to be finely divided into color tones, so that the black-and-white image converted into color can be easily recognized.

In FIG. 3 also shows a second phase modulator 13 which is not controlled by the signal V '. but can be adjusted manually using a potentiometer. This additional rotation of the phase for the synchronous modulators 4 and 5 can be the initial or. End point in the FIG. 2 move the harb circle shown as desired. This gives you the option of being able to optimally adapt the color of the image areas of interest to the eye of the beholder. Reference numeral 14 denotes a phase shift element which shifts the phase by 90 ° to obtain the signal ('/?,. The entire circuit shown in FIG. 3 is denoted by IiI and represents the phase modulation and dcmodulation device according to the present invention represent.

In FIG. 4, only one way is shown aufbe- the color television signal obtained with the arrangement of Fig. 1 or 3 to standardized signals ride to be able to which can be processed in commercially available devices. For this purpose , the signals R-Y, B- Y and Y taken from the phase modulator Hl are subjected to a PAL processing 15, then fed to a PAL modulator 16, which is preceded by a reference color carrier generator 17 with 4.43 MHz and which then complies with the standard The FBAS signal for monitors emits this via a video modulator 18 connected in parallel into the signals for channels 2 to 4 or 5 to H for standard color television receivers.

6c catcher is converted. This signal processing represents a favorable design option because it is then possible to be able to reproduce color images derived from black and white signals via commercially available television receivers.

* 5 In the fig. 5 shows the manner in which the phase position of the signal HF of the reference color carrier 3 can be changed as a function of the amplitude of the black-and-white signal BA (S) . Sent ahead

may be the well-known fact that there are bridges circuit consisting of three resistors and a capacitor, one of which is variable. can be used as a phase shifter. It is known that the diagonal between the one branch consisting of the two fixed resistors and the other branch with the variable resistance and the voltage tapped off the capacitor by one, depending on the size of the variable resistance certain phase angle is shifted with respect to the input voltage on the other diagonal the bridge rests. The partial stresses in one branch of the bridge with the variable resistance and the capacitor are always perpendicular to each other, because in the resistor current and voltage are in phase, im Capacitor, on the other hand, current and voltage are phase-shifted by 90 ° with respect to one another. So will the If the resistance changes, the point of intersection of the two partial voltages shifts to one Semicircle over the input voltage with simultaneous change of the phase angle on the diagonal tapped tension.

Starting from this known phase shifter, FIG. 5, a field effect transistor 19 is used as a variable resistor, in which the volume resistance between output 24 and emitter of transistor 20 changes with the amplitude of the voltage at the input. If the luminance signal BA (S) is applied to the input, which corresponds to the feed line 1 in FIG. 1, then the volume resistance of the field effect transistor 19 also changes depending on the signal frequency of this RAS or the V signal. The reference color carrier 3 is fed in at the input of a further transistor 20. It appears in the same phase position at the emitter and is phase shifted by 180 ° at the collector. If the resistors 21 and 22 are chosen to be of the same size, then both voltages are also of the same size and, based on the consideration of the known phase shifter, the phasor diagram shown in FIG. 5a applies. in which the partial voltages LV and LIr move with their point of intersection on a semicircle, the size of which is determined by the input voltage U _C e and in which the output voltage Ua. which is tapped at the diagonal of the bridge circuit from the resistors 21, 22 and from the field effect transistor 19 and the capacitor 23, remains unchanged in its amplitude, but is varied in its phase angle φ between zero and 180 ° depending on the change in resistance of the field effect transistor can. The phase modulator, designated as a whole by the reference symbol I, whose output voltage is tapped between points 24 and 25, where 25 denotes the connection to ground, is supplied with energy via line 26 and also has a further capacitor 27 and two resistors 28.

It has been shown that the achievable change in the phase angle g with that shown in FIG. 5 arrangement of the phase modulator I shown in practice is only sufficient to achieve a phase shift of about 120 '. Therefore, according to FIG. b provided, for the entire phase modulator 2. as it is used in FIG. 1, three phase modulators I according to FIG. 5 to be switched one behind the other, so that depending on the luminance signal t /, a phase shift of the input signal LJf of the reference color carrier connected at 3 between 0 and 360 ° is possible. The output voltage U _A can be tapped off at 29.

In order to achieve that only the brightness range of a sub-area of the viewing image entire color scale is assigned, according to FIG. 7 provided the phase diode IU of FIG Clamping circuit 30 to be connected upstream with a contrast enhancer 31. It is also possible, as shown in FIG. 7th is shown to connect a sync pulse separator 32 in parallel or the sync pulses from the outset to be forwarded separately if they are also supplied separately. It is then necessary, however, that the contrast amplifier 31 taken signal both the phase modulator III and a summing stage 33 so that it can be assigned to the black-and-white signal Y again at 34.

By switching the F i g. 7 it is achieved that the from F i g. 8 visible sub-area 35 of a black-and-white signal, which the area ;; includes, is faded out, and can be amplified over the entire color value scale from the original size b to the size a. In the black-and-white signal curve shown in FIGS. 8 and 9, the sync pulses are denoted by 36. The areas c of the original black and white signal are separated. This configuration makes it possible to pick out an interesting sub-area of an image and to assign the entire color scale to the gray tones prevailing there, so that a very fine distinction between black and white images is given. This method enables good diagnostics, particularly in X-ray technology. Since the V 'signal of the color television tube is also passed on, the resulting picture is not only characterized by the assignment of the entire color scale to the black-and-white values, but also by the fact that there are differences in brightness within the color values, which are easy to interpret and enable the color image obtained to be recognized.

For this purpose 2 sheets of drawings

Claims (3)

Claims: L) The invention relates to a method and a 1. A method for color reproduction of black-and-white images on color television picture tubes with television technology means, in which, depending on the amplitude of the black-and-white television signal, auxiliary signals for influencing at least one of the three color signals are formed, characterized in that the high-resolution send Representation of small differences in brightness the amplitude of the black-and-white television signal (Uy) directly as a control signal for rotating the phase of a reference color carrier (3) which determines a chrominance signal (Uf) ! Forms phase position in the color ice, which is then demodulated into the usual red and blue color difference signals (Ur->. Ue-y) and fed to the color television picture tube with the black-and-white television signal. 2. The method according to claim 1. characterized marked- * o that in addition a further phase modulation (13) of the reference support (3) is made, the choice of color is arbitrary can be adjusted. 3. The method according to claims 1 and 2, characterized in that before the phase modulation (111) of the reference color carrier (3) only a sub-area (35) of the black-and-white signal is separated and only these sub-values of the gray tone are separated from the entire area of the subsequent phase modulation as output values to serve.