Method and assembly for checking the operating mode of a screen

Abstract

A method for checking an operating mode of a display screen switchable between a free-viewing operating mode B1 and a restricted-viewing operating mode B2, comprising: in operating mode B2, determining a brightness value H of a surface and/or edge of a transparent light guide; then, depending on the brightness value H: i) unchanged use of operating mode B2 if the brightness value lies within a range of specified Hg values; ii) switching off operating mode B2 if the brightness value lies within a range of specified Hs values; or iii) changed use of operating mode B2 if the brightness value lies within a range of specified Hm values, with the control unit exerting an influence on the image content perceptible on the display screen by reducing the latter's brightness and/or contrast, with the range Hm lying between the ranges Hs and Hg, and with the ranges bordering on each other.

Claims

1. A method for checking an operating mode B2 of a display screen with a control unit for switching over the display screen between two operating modes, viz B1 for a free viewing mode and B2 for a restricted viewing mode, wherein the switching on of the operating mode B2 comprises the switching on of light sources if they are off in operating mode B1, and the switching off of the light sources if they are on in operating mode B1, and wherein the light generated by the light sources is fed into a transparent light guide, wherein for operating mode B1 the light guide radiates the light into a wide viewing space and for operating mode B2, when operating mode B2 comprises a switching off of light sources, the light guide minimizes a radiation of light into a wide angle and, when operating mode B2 comprises a switching on of light sources, light from the light guide is radiated sideways, but not in a frontal direction, so as to outshine the image sideways, the method comprising the following steps at a selectable point in time after the operating mode B2 has been switched on: A) Determining the brightness value H at least at one point P of at least one surface and/or edge of the transparent light guide, B) Prompting one of the following steps by the control unit, depending on the brightness value H determined: i) Unchanged use of the operating mode B2 of the display screen if the brightness value H lies within a range of specified Hg values, where Hg defines a required value range for which the quality of operating mode B2 is sufficient, so that no influence needs to be exerted, ii) switching the operating mode B2 of the display screen off if the brightness value H lies within a range of specified Hs values, where Hs defines a value range for which the quality of operating mode B2 is not sufficient, so operating mode B2 cannot be used or is not available, or iii) changed use of the operating mode B2 of the display screen if the brightness value H lies within a range of specified Hm values, wherein the control unit exerts an influence on the image content perceptible on the display screen by reducing its brightness and/or its contrast, with the range Hm lying between the ranges Hs and Hg, and the ranges bordering on each other.

2. The method as claimed in claim 1, wherein said brightness value H is measured by at least one light-sensitive sensor, preferably a photodiode.

3. The method as claimed in claim 2, wherein the at least one light-sensitive sensor corresponds to at least one light source or parts thereof, which is operated in a light-sensitive mode.

4. The method as claimed in claim 1, wherein the step A) is, at least at two defined points in time T1, T2, . . . after the step i), carried out at least twice in succession for the determining of brightness values H1, H2, . . . , wherein preferably the light sources (2), at the defined points in time T1, T2, . . . , radiate defined light intensity values L1, L2, . . . , which preferably differ from each other.

5. The method as claimed in claim 4, wherein all brightness values H1, H2, . . . are compared with ranges of specified values Hg1, Hg2, . . . , and the operating mode B2 continues to be used only when all brightness values H1, H2, . . . lie within the respective ranges of specified values Hg1, Hg2, . . . .

6. The method as claimed in claim 1, wherein the brightness and/or contrast of the display screen are reduced in a degree depending on the brightness value H.

7. A method for checking an operating mode of a display screen that can be operated in two operating modes, viz B1 for a free viewing mode, and B2 for a restricted viewing mode, wherein a switching over between the operating modes B1 and B2 comprises at least the switching on of light sources if they are off in operating mode B1, and comprises the switching off of the light sources if they are on in operating mode B1, and wherein the light generated by the light sources is fed into a transparent light guide, wherein for operating mode B1 the light guide radiates the light into a wide viewing space and for operating mode B2, when operating mode B2 comprises a switching off of light sources, the light guide minimizes a radiation of light into a wide angle and, when operating mode B2 comprises a switching on of light sources, light from the light guide is radiated sideways, but not in a frontal direction, so as to outshine the image sideways, the method comprising the following steps at a selectable point in time after the light sources have been switched on or off, respectively: A) Determining a brightness value H at least at one point P of at least one surface and/or edge of the transparent light guide by means of at least one light-sensitive sensor, wherein the said light-sensitive sensor corresponds to at least one light source, which, for this purpose, is operated as a light-sensitive sensor in a light sensitive mode, only for the duration of determining the brightness value H, B) Comparison of the brightness value H with a range of Hg values, wherein the operating mode B1 is active if the brightness value H lies outside the said range Hg, where the quality of operating mode B2 is not sufficient, so operating mode B2 cannot be used or is not available, and wherein the operating mode B2 is active if the brightness value H lies within the said range Hg, where the quality of operating mode B2 is sufficient, so that no influence needs to be exerted.

8. An arrangement comprising: a display screen that can be operated in two operating modes, viz B1 for a free viewing mode and B2 for a restricted viewing mode, with light sources the light of which is fed into a transparent light guide, with the switching on of the operating mode B2 comprising at least the switching on of the light sources if they are off in the operating mode B1, and comprising the switching off of the light sources if they are on in the operating mode B1, wherein for operating mode B1 the light guide radiates the light into a wide viewing space and for operating mode B2, when operating mode B2 comprises a switching off of light sources, the light guide minimizes a radiation of light into a wide angle and, when operating mode B2 comprises a switching on of light sources, light from the light guide is radiated sideways, but not in a frontal direction, so as to outshine the image sideways, a control unit that can switch over the display screen between the two operating modes B1 and B2, means for determining the brightness value H at least at one point P of at least one surface and/or edge of the transparent light guide, if the display screen is operating in operating mode B2, the control unit being configured in such a way that it can prompt one of the following steps depending on the brightness value H determined: i) Unchanged use of operating mode B2 of the display screen, if the brightness value H lies within a range of specified Hg values, where Hg defines a required value range for which the quality of operating mode B2 is sufficient, so that no influence needs to be exerted, ii) switching off the operating mode B2 of the display screen, if the brightness value H lies within a range of specified Hs values, where Hs defines a value range for which the quality of operating mode B2 is not sufficient, so operating mode B2 cannot be used or is not available, or iii) changed use of operating mode B2 of the display screen, if the brightness value H lies within a range of specified Hm values, wherein the control unit exerts an influence on the image content perceptible on the display screen by reducing its brightness and/or contrast, with the range Hm lying between the ranges Hs and Hg, and the ranges bordering on each other.

9. Use of arrangement as claimed in claim 8, in a device for handling payment-relevant processes and/or for cash depositing or withdrawal, or in a vehicle, with the said use in operating mode B2 being admitted only if the determined brightness values H in operating mode B2 lie in a predefined range Hg or Hm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention will be explained in more detail with reference to accompanying drawings, which also show features essential to the invention, and in which:

(2) FIG. 1 is a sketch illustrating the principle of the invented method applied to a display screen with a light guide arranged (in the viewing direction) behind a backlit image generator, with the display screen being operated in the free viewing mode B1,

(3) FIG. 2 is a sketch illustrating the principle of the invented method applied to a display screen with a light guide arranged (in the viewing direction) behind a backlit image generator, with the display screen being operated in the restricted viewing mode B2,

(4) FIG. 3 is a sketch illustrating the principle of the invented method applied to a display screen with a light guide arranged (in the viewing direction) in front of an image generator, with the display screen being operated in the restricted viewing mode B2, and

(5) FIG. 4 is a sketch illustrating the principle of the invented method applied to a display screen with a light guide arranged (in the viewing direction) in front of an image generator, with the display screen being operated in the free viewing mode B1.

(6) The drawings are not to scale and represent principles only.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 is a sketch illustrating the principle of the invented method applied to a display screen 1 with a light guide 3 arranged (in the viewing direction) behind a backlit image generator 5, with light sources 2 for the lateral coupling in of light, with the display screen 1 being operated in the free viewing mode B1. An exemplary first embodiment of such a display screen 1 or a backlight 6 switchable between two operating modes B1 and B2 can be derived in further details of the applicant's WO 2015/121398 A1. Other embodiments are also possible, of course.

(8) For the free viewing mode B1, the—directed—backlight 6 is switched off, whereas the light sources 2 are switched on, which feed light into the light guide 3, which, being decisive for switching between the operating modes B1 and B2, radiates the light by means of an image generator 5, e.g., an LCD panel, into a wide viewing space. At least one light-sensitive sensor 4, e.g., a photodiode, is then arranged at that edge of light guide 3 which is positioned opposite the coupling-in edge of the light guide 3 for the light sources 2, in order to detect a brightness value H at least at one point P of the light guide 3. Naturally, several light-sensitive sensors 4 can be provided as well.

(9) On account of the coupling of light from the light sources 2 into the light guide 3, which in operating mode B1 is desired, the determined value H will more likely be high here, possibly amounting to several hundred thousands or millions lm/m.sup.2 (equivalent to the quantity lx). Such a value would result, e.g., if 40 LEDs were each coupling 40 lm of light into a light guide 3 having a length of 120 mm, with the light guide being 2 mm thick, and with about 90% of the light being coupled out of the light guide 3 on account of outcoupling structures, while about 10% of the light coupled in will exit the light guide 3 at the edge situated opposite to the coupling-in side of the light guide 3.

(10) Thus, in operating mode B1, the (assumedly) determined value H mentioned above, amounting to several 100,000 lx, lies outside the ranges Hg and Hm; it will rather be found in range Hs. If such high values actually occurred in operating mode B2, the electronic control circuitry would switch the operating mode B2 off, which would be the case, e.g., due to an erratic behavior of the display screen 1, for instance if the display screen 1, when in operating mode B1, has failed to react to a command to switch over to operating mode B2.

(11) Contrary to this, FIG. 2 is a sketch illustrating the principle of the invented method applied to a display screen 1 with a light guide 3 arranged (in the viewing direction) behind a backlit image generator 5, with the display screen 1 being operated in the restricted viewing mode B2. The structure is thus the same as described above for FIG. 2, with the difference that, now, the light sources 2 are switched off, whereas the directed backlight 6 is switched on. Because of the directed backlight 6 and the transparent light guide 3, the restricted viewing mode B2 is reached. This, however, applies only if the least possible light is radiated by light guide 3 into a wide angle.

(12) Here, the invented method for checking an operating mode B2 of a display screen 1 with a control unit that can switch the display screen 1 between two operating modes, viz B1 for a free viewing mode and B2 for a restricted viewing mode—with the switching on of operating mode B2 comprising the switching on of the light sources 2 if in operating mode B1 the light sources 2 are off, and comprising the switching off of the light sources 2 if in operating mode B1 the light sources 2 are on, and wherein the light generated by the light sources 2 is fed into a transparent light guide 3—comprises the following steps executed at a selectable point in time after operating mode B2 has been switched on: A) Determining the brightness value H at least at one point P of at least one surface and/or edge of the transparent light guide 3, B) Prompting one of the following steps by the control unit, depending on the brightness value H determined: i) Unchanged use of operating mode B2 of the display screen 1, if the brightness value H lies within a range of specified Hg values, ii) switching the operating mode B2 of the display screen 1 off, if the brightness value H lies within a range of specified Hs values, iii) changed use of operating mode B2 of the display screen 1, if the brightness value H lies within a range of specified Hm values, wherein the control unit exerts an influence on the image content perceptible on the display screen 1 by reducing its brightness and/or contrast, optionally in a degree depending on the brightness value, with the range Hm lying between the ranges Hs and Hg, and the ranges bordering on each other.

(13) At least one light-sensitive sensor 4, e.g., a photodiode, is then arranged at that edge of the light guide 3 which is positioned opposite to the coupling-in edge of the light guide 3 for the light sources 2, in order to detect the brightness value H at least at one point P of the light guide 3.

(14) In this embodiment, an exemplary range of Hg values for the operating mode B2 will comprise low values, e.g., values smaller than 1.000 lx, as otherwise too much light from the light guide 3 is radiated in wide angles by means of the image generator 5. Here, an exemplary range Hm would comprise values between 1,000 lx and 10,000 lx. The closer the determined brightness value H is to the upper limit of the range Hm, the further down, in step iii), will the control unit reduce the brightness and/or the contrast of the image represented on the display screen 1. In the example described, the range Hs comprises brightness values greater than 10,000 lx.

(15) In a second embodiment of the display screen 1, which is illustrated in FIGS. 3 and 4, the light sources 2 are on for operating mode B2. An exemplary configuration for such a display screen 1 can be derived from WO 2017/097975 A1. This publication describes a display screen for a free and a restricted viewing mode wherein a light guide 3 for the restricted viewing mode receives light from lateral light sources. The light then is radiated from the light guide 3 primarily sideways, but not toward the front, so as to outshine the image sideways, whereas it is still perceptible from the front. Thus, protection against unwanted viewing, i.e., the operating mode B2 can be generated. FIG. 3 illustrates the principle of the invented method, applied to a display screen 1, with a light guide 3 arranged (in viewing direction) in front of an image generator 5, with the display screen 1 being operated in the restricted viewing mode B2. Here again, at least one light-sensitive sensor 4, e.g., a photodiode, is arranged at that edge of the light guide 3 which lies opposite to the coupling-in edge of the light guide 3 for the light sources 2, in order to detect the brightness value H at least at one point P of the light guide 3.

(16) According to the invention, now first the light sources 2 are switched on, the light of which is fed into a transparent light guide 3 in order to activate operating mode B2. Subsequently, the following steps are carried out: A) Determining the brightness value H at least at one point P of at least one surface and/or edge of the transparent light guide 3. B) Prompting one of the following steps by the control unit, depending on the brightness value H determined: i) Unchanged use of operating mode B2 of the display screen 1, if the brightness value H lies within a range of specified Hg values ii) switching the operating mode B2 of the display screen 1 off, if the brightness value H lies within a range of specified Hs values, iii) changed use of operating mode B2 of the display screen 1, if the brightness value H lies within a range of specified Hm values, wherein the control unit 1 exerts an influence on the image content perceptible on the display screen 1 by reducing its brightness and/or contrast, optionally in a degree depending on the brightness value.

(17) Here, the range of Hg values for the operating mode B2 will more likely comprise high values, e.g., with a lower limit of one hundred thousand lx or higher, or, alternatively, even of one or several million lx, because otherwise not enough light would be radiated from the light guide 3 above the image generator 5 into lateral angles (radiation into the frontal direction should be avoided, though) and, thus, the viewing restriction would be brought about in lateral directions due to cross fading. On account of the coupling of light from the light sources 2 into the light guide 3—which is desired for the operating mode B2—here the value H, in the configuration shown in FIG. 3 with the light sources 2 switched on, will actually lie in this range, provided that the light sources 2 are operating correctly; the value H may amount, e.g., to 500,000 lx (or, in the alternative case, 2,500,000 lx). It will thus lie within the range Hg suggested for this second embodiment, and the operating mode B2 will be used unchanged.

(18) In this case, the range Hm can comprise values between 70,000 lx and up to 100,000 lx. Therefore, according to the invention, the control unit would, in step iii), influence the image content displayed.

(19) The control unit would switch the operating mode B2 off only in case the determined brightness value H were located in range Hs, comprising values smaller than 70.000 lx.

(20) FIG. 4 is a sketch illustrating the invented method, applied to a display screen 1 with a light guide 3 arranged (in viewing direction) in front of an image generator 5, with the display screen 1 being operated in the free viewing mode B1. As the light sources 2 are switched off here, the sensor 4 determines a low value H, e.g., 500 lx or 2,000 lx, which results from residual light tolerances due to light captured by light guide 3. The light captured originates from the ambient light and from the image represented on the display screen 1, among other causes. Thus, H lies in range Hs, and the operating mode B2 cannot be used or is not available, respectively.

(21) As described above, the values specified for the brightness value H and the ranges Hg, Hm, Hs are examples only. Other values and ranges are possible, of course.

(22) Further embodiments are designed to allow dynamic variations of the ranges Hg, Hm, Hs or, if existing, the ranges Hg1, Hm1, Hs1, Hg2, Hm2, Hs2, . . . , for adaptation to different brightnesses of the display screen 1.

(23) As the above explanation of the invented method can be applied analogically to the invented arrangement, it is not repeated here for redundancy reasons.

(24) The display screen 1 may also correspond to a static image in some cases.

(25) The invented method and the invented arrangement can be used to advantage in a device for handling payment-relevant processes and/or for cash depositing or withdrawal, or in a vehicle.

(26) The display screen described above solves the problem of the invention: The above description covers a method and an arrangement for checking the quality of the operating mode of a display screen that can be operated in at least two operating modes, viz B1 for a free viewing mode and B2 for a restricted viewing mode, without the need of a user or operator being on the spot. Further, the invention occupies little space and needs no structural elements or components outside the volume of the respective display screen.