Glasses display system for displaying virtual images with improved efficiency

Abstract

The present disclosure relates to an eyeglass display system (1) for displaying a virtual image in a user's field of view, comprising: a screen unit (2) for emitting light (34) as computer-generated image information, the screen unit (2) having at least a first color line and a second color line, each color line having a different color (14, 11), each color having at least one row of color pixels extending along the color line; a scanning deflection unit (3) for scanning the screen unit (2) and for deflecting the computer-generated image information emitted from the scanned screen unit (2) into the user's eyes; wherein the electro-optical efficiency of the color pixels of the first color line is lower than the electro-optical efficiency of the color pixels of the second color line, and the first color line has at least one more row of color pixels than the second color line, so as to compensate for the difference in electro-optical efficiency, thereby providing an eyeglass display system (1) with improved efficiency.

Description

Technical Field

[0001] The present disclosure relates to an eyeglass display system for displaying a virtual image in a user's field of view, the eyeglass display system comprising: a screen unit for emitting light as computer-generated image information, the screen unit having at least a first color line and a second color line, each color line having a different color, each color line having at least one row of color pixels extending along the color line; and a scanning deflection unit for scanning the screen unit and deflecting the computer-generated image information emitted by the scanned screen unit to the user's eyes. Background Art

[0002] Color line displays, i.e. color line screen units, which may also be referred to as linear color displays or linear color screen units, can generate two-dimensional color images by a time multiplexing process and a one-dimensional scanning mirror unit in the imaging beam path, which is known in the prior art. To this end, the line display unit and the scanning mirror unit are controlled in a synchronized manner. Three basic or primary colors are used for color display, which span the color space. Usually red, green and blue.

[0003] A particularly advantageous technical implementation uses so-called μLEDs. These are advantageous because they can be used to achieve particularly fast switching times of display pixels, i.e. pixels perceived by the user in a two-dimensional or three-dimensional color image, and the light intensity is very high by comparison. For multicolor displays, light-emitting diodes with sizes in the μm range and three different center wavelengths in the blue, green and red range are used to obtain the desired colors by additive color mixing. Line scan screen or display technology is particularly suitable for head-mounted display systems, also known as virtual reality glasses or augmented reality glasses (VR glasses or AR glasses). This leads to specific requirements in terms of weight, power consumption and waste heat generation of the display unit. In particular, in augmented reality applications, the maximum achievable brightness is also critical, because in this application the virtual image is superimposed on the natural environment, and if the reflected virtual image is brighter than the light from the natural environment, the virtual image can only be seen by the user in front of the sometimes very bright environment. This is a particularly limiting boundary condition, especially in bright sunlight, for example when using augmented reality glasses outdoors.

[0004] WO 2021 / 206875 A1 describes a so-called three-line display that enables a two-dimensional image display when viewed through a synchronous scanning mirror. GaN μLEDs are integrated in rows on a CMOS carrier. In addition to the three RGB color lines, a further color line is proposed as an option, in particular an implementation with white LEDs as a further line.

[0005] US 7,771,098 B2 describes a display with four primary color emitters, whereby an additional yellow color is also proposed. The aim here is to expand the color space and increase the light intensity.

[0006] In principle, various methods are known for controlling screen units or displays with several primary emitters (i.e. more than three RGB emitters) that form display pixels using RGB video signals. The primary emitters then form corresponding sub-pixels or color pixels, which in turn form display pixels. For example, in the book "The Multi-Primary Advantage" by Michael E. Miller. Such an approach is proposed in the chapter "Color in Electronic Display Systems" published by Springer 2019, pages 183 to 209. Here, another primary color is used to save energy.

[0007] Another problem, namely the correction of chromatic aberrations, is dealt with in the publication “Practical Chromatical Apparation Correction in Virtual Reality Displays Enabled by Cost-Effective Ultra Broad Band Liquid Crystal Polymalenses” by Zhan Tao et al., which is published in Advanced Optical Materials 8.2 (2020): 1901360. Here, chromatic aberrations are optically corrected using diffractive liquid crystal lenses. Other methods are also known to solve this problem, but due to their technical limitations, these methods are very disadvantageous for eyeglass display systems because they require a large number of optical elements and therefore a large amount of installation space, as a result of which they have a high weight and have a negative overall impact on the design. As a result, in the known eyeglass display systems, chromatic aberrations are not adequately compensated, which are reflected in visible artifacts in the form of rainbow color fringes, especially in the case of high-contrast displays, such as black text on a white background.

[0008] In particular, the optics of AR or VR glasses as eyewear display systems are technically compromised with the total volume of the glasses and therefore with the weight of the glasses. Therefore, the optics must be as small and light as possible. This also applies to eyewear display systems that work on linear displays combined with one-dimensional scanners, and also to optics that map μLED pixels to infinity. Fresnel structures, microlenses or diffraction structures are used to make the optics as small as possible. For example, in the article “Augmented reality and Virtual reality displays: emerging technologies and future perspectives” written by Xiong, Jianghao et al., published in Light: Science & Applications 10.1 (2021): 1-30 and US10133076, it is described. With these types of optics, there is an additional problem, namely that visible, and in some cases only indirectly, artifacts reduce the image quality. These effects can be moiré effects, especially of Fresnel lenses, rainbow effects that occur with diffractive optics, and weaker effects such as stray light on the edges of Fresnel facets or between microlens arrays.

[0009] The task is therefore to overcome the known problems and to provide an eyeglass display system which exhibits an improved efficiency and which in particular overcomes several problems of the prior art which appear to exist independently of one another. Summary of the invention

[0010] This object is achieved by an eyeglass display system according to the independent patent claim. Advantageous embodiments are shown in the dependent patent claims, the description and the drawings.

[0011] One aspect relates to an eyewear display system, also referred to as VR goggles / glasses or AR goggles / glasses, for displaying a virtual image in a user's field of view, preferably superimposed with a real image from the user's physical environment. The eyewear display system has a screen unit for emitting light as computer-generated image information. The screen unit has at least a first color line and a second color line, each color line having a different color, each color line having at least one row of color pixels, which are assigned to the color line extending along the color line (i.e., along the main extension direction of the color line). Therefore, the color pixels of the color line (also referred to as sub-pixels corresponding to the main emitter) preferably have a single color, i.e., the color assigned to the color line. Therefore, each color line corresponds to a color channel and therefore preferably has only one main emitter of a specified color. The spatial extension of each row corresponds to the spatial extension of the image information in the direction of the row. Therefore, the spatial extension of the row is perpendicular to the scanning direction of the scanning deflection unit described below, and therefore corresponds to the first dimension of the computer-generated image information of the two-dimensional display. The row of each color line and preferably all rows extend in parallel. Besides the main emitting element, which may be or comprise individual LEDs, the display unit may also have one or more lens elements, which are designed to direct, in particular focus, the light generated by the main emitting element to the above-mentioned scanning deflection unit.

[0012] Therefore, the screen unit can also be called a linear screen unit or line screen unit because it is designed to display only one dimension of image information at a time. The second dimension required to display the two-dimensional image information is then accessed using the familiar line scanning technology.

[0013] Therefore, the glasses / glasses display system also has a scanning deflection unit, a scanner deflection unit or a scanner unit for scanning the screen unit and for deflecting the computer-generated image information emitted by the scanned screen unit into the eyes of the user, i.e. into at least one eye, i.e. into one or both eyes of the user. For this purpose, the scanning deflection unit can have a plurality of beam splitter elements, which are designed as scanning beam splitter elements. By means of a suitably designed control unit, which is designed to control the screen unit and the scanning deflection unit in a synchronized manner, a virtual two-dimensional image can be generated by using a time-division multiplexing process of the line screen units. As is known, in the time-division multiplexing method, the brightness of the line display units is synchronized with the corresponding scanning angles of the scanning deflection unit.

[0014] The electro-optical efficiency of the color pixels of the first color line is lower than the electro-optical efficiency of the color pixels of the second color line, and the first color line has at least one more row of color pixels than the second color line, so as to compensate for the different electro-optical efficiencies, so that the maximum producible brightness of the different color lines perceptible to the human user corresponds to the wavelength-related color perception of the human and matches each other. Therefore, the electro-optical efficiency can also be called the perceived electro-optical efficiency, whereby the human perception of brightness is quantitatively described by the V-lambda curve of DIN 5031 as effective when applied. This generally defined curve is also called the brightness sensitivity curve or relative spectral brightness sensitivity, and describes the nonlinear and wavelength-related color perception / perception of the human. The compensation here also includes incomplete compensation in the sense of adjusting or reducing the maximum brightness difference that can be produced by different color lines. Therefore, the number of rows that the first color line has more than the second color line can be the number with the smallest final brightness difference at the maximum brightness, which can be produced by the two color lines perceived by the human user. For example, the brightness of each display pixel can be considered.

[0015] This has the advantage of compensating for the reduced electro-optical conversion efficiency of the semiconductor materials used to manufacture the longer wavelength LEDs. Due to human color perception, at least three primary colors are required to span the color space. In order to achieve the largest possible color space, red LEDs with relatively long wavelengths, for example with a wavelength of 640 nm, must be used. For example, if only a wavelength of 600 nm is used, the color space is greatly reduced, which means that many red tones can no longer be displayed. Therefore, the lower electro-optical efficiency is compensated by one or more additional rows of color pixels, so that the required intensity can be achieved with a large color space despite the lower electro-optical efficiency. This is based on the recognition that, by appropriate control, the image information of the color pixels scanned continuously by the scanning deflection unit and thus the image information of the LEDs is accumulated in the user's eyes, and thereby the color pixels arranged at different positions of the continuous scanning are perceived as being at the same position as the same display pixel. At the same time, the greatly reduced sensitivity of the human eye to longer wavelengths in the red range can be compensated. Despite at least one additional row of color pixels, the described embodiments form the basis for the design of an eyeglass display system, the overall efficiency of which is improved despite the additional color pixels, as will also be explained below.

[0016] In an advantageous embodiment, it is provided that the color pixels are or include light-emitting diodes having an emission width of less than 50 μm and / or less than 0.003 mm. 2The light-emitting width can be understood as the width and / or length of the light-emitting surface of the light-emitting diode, the light-emitting surface, or in the case of a circular or elliptical light-emitting surface, the corresponding maximum diameter. Such an LED can be referred to as a μLED. The light-emitting diode is preferably based on GaN technology, i.e. has gallium nitride as the light-emitting material. The described embodiments are particularly advantageous for light-emitting diodes based on gallium nitride, since the conversion efficiency for longer wavelengths decreases particularly sharply with this semiconductor. With the small size of the μLED and the particularly fast switching times of the GaN main emitter, line display units can be realized in a particularly space-saving and efficient manner.

[0017] Non-square color pixels, i.e. color pixels with non-square emitting surfaces, i.e. circular or oval or rectangular emitting surfaces with different sides / side lengths, are particularly advantageous here. This allows color lines with corresponding rows to be advantageously arranged in the further scanning and superposition of multiple rows of color, so that a two-dimensional virtual image can be generated particularly efficiently.

[0018] In another advantageous embodiment, the color of the first color line is in the range of 560nm to 650nm, in particular in the range of 570nm to 590nm. Therefore, the color of the first color line or the first color is in the range of red-orange or orange. Since the electro-optical efficiency is particularly low in the red-orange range, it is advantageous to provide more rows of color pixels there. It is particularly advantageous to select the first color to be in the orange range, i.e. in the range of 570nm to 590nm, because white tones can be displayed in combination with other colors in a particularly energy-saving manner. By appropriately selecting the second color, i.e. the color of the second color line, for example in the range of 400nm to 495nm, preferably in the range of 440nm to 485nm, i.e. in the blue range, a large number of white tones can be displayed without activating the usual LEDs in the range of 600nm and larger. This is inefficient together with another green LED due to the poor perception of human beings to red tones and due to the poor electro-optical efficiency of the display. This means that not only one less color has to be generated for the white hue, i.e. two colors instead of three, but also the generation of red light in the range of 600 nm and above can be completely omitted, thereby significantly improving the energy efficiency. The resulting higher brightness with less heat is particularly advantageous for eyeglass display systems, whereby due to the improved energy efficiency, smaller batteries can be selected for the same operating time, i.e. eyeglass display systems with lower weight can be achieved for the same operating time.

[0019] Furthermore, there is the additional advantage of improved compensation of wavelength dependent chromatic aberrations, as explained in more detail below.It should be remembered here that chromatic aberrations arise due to the wavelength dependence of the refractive index when imaging a line display unit in the field of view of a human user using one or more lens elements.

[0020] As is known, in refractive optics, it is easiest if only one wavelength needs to be imaged, such as a spectrally narrowband laser. However, due to the color perception of human perception, several wavelengths or several emission spectra are required, especially in eyewear display systems, in order to be able to display a useful color space. Usually, the familiar three emission spectra are used, which have red, green and blue when viewed individually. For example, the wavelengths of the Fraunhofer lines F, d, C (486 nm, 588 nm, 656 nm) are used in optical simulations as a standard for the design of optics for the visible range. In the case of LED displays or μLED displays, the wavelength distribution resulting from these is known and is used for the optimization of the optics according to the corresponding emission spectra. The problem is that for the three main emitter elements of the red, green and blue main emitter elements, the three emission spectra are relatively far apart, so that the correction of chromatic aberrations is technically very demanding. Therefore, chromatic aberrations are most significant in high-contrast image content, especially in black and white image content, because all three primary colors are equally activated there.

[0021] However, since according to the approach presented here, the black and white image content depends on the existing design and the desired white tint (which can be one of many white tints at different color temperatures), only or mostly the color of the first color line and the color of the second color line are needed, and thus the optics of the eyewear display system must be optimized for only these two center wavelengths or emission spectra instead of three center wavelengths or emission spectra in a technical tradeoff, it is technically easy to achieve improved effective color correction in the approach described here. As a result, the described design enables better optical color correction of image content, where color artifacts in the form of rainbow color fringes are particularly visible in conventional approaches. In return, stronger color differences are accepted for color representation and image content, where the color differences are no longer strongly perceptible by human users.

[0022] Another advantage here is that the two colors, i.e. the dominant wavelengths for white display, are closer together than in the usual approach. This also distinguishes the approach described from solutions that propose a white LED as a fourth color. Of course, fewer color pixels must also be activated to display white, i.e. ideally only one additional white LED and no others. However, this is the case because the available white LEDs have a relatively broad spectral distribution, with the dominant wavelength being in the blue spectral range and in the region around 600 nm. Therefore, the use of a single white LED pixel requires that the lens system required for viewing must be optimized for a large number of widely spaced wavelengths, as in other conventional solutions, which, as described, is not necessary in the approach proposed here.

[0023] Therefore, in a further advantageous embodiment, it is provided that, in the CIE-1931-standard chromaticity diagram color space, the connecting line of the colors of the first and second color lines extends substantially parallel to a section of a blackbody curve, which includes the blackbody curve from the high temperature end (T=∞) to a height of at most a white point, in particular a temperature point of at most 2700K, preferably a temperature point of at most 1800K. The blackbody curve is also referred to as a blackbody curve. Here, by "substantially parallel", it is understood that the tangential course and / or course of the connecting line, wherein the maximum distance of the connecting line from the section of the blackbody curve does not exceed a specified maximum distance, for example, in the CIE-1931 standard chromaticity diagram color space, this maximum distance can be 0.05 or 0.01. The distance between the connecting line and the section of the blackbody curve is measured perpendicular to the connecting line. Therefore, it is the distance between two intersection points of a straight line perpendicular to the connecting line, wherein the first intersection point is the intersection point with the connecting line and the second intersection point is the intersection point with the section of the blackbody curve.

[0024] In a particularly advantageous embodiment, it is provided that the screen unit has exactly two color lines, namely a first and a second color line. This allows a particularly energy-saving image display system to be realized, which is particularly suitable for displaying black text on a white background or white text on a black background.

[0025] In an alternative embodiment to the last embodiment, the display unit has a third and a fourth color line in addition to the first and second color lines. The color of the third color line is in the green range, i.e. in the range of 500 nm to 550 nm, preferably in the range of 515 nm to 535 nm, and the color of the fourth color line is in the red range of 580 nm to 650 nm, preferably in the range of 590 nm to 640 nm. This has the advantage that the described benefits are achieved in the extended color space of a conventional full-color display and thus a full-color display with improved efficiency is provided.

[0026] It can be provided that the electro-optical efficiency of the color pixels of the third color line is between the electro-optical efficiency of the color pixels of the second color line and the first color line, and the third color line has at least one more row of color pixels than the second color line, and / or the first color line has at least one more row of color pixels than the third color line. Therefore, it can also be provided that the electro-optical efficiency of the color pixels of the fourth color line is lower than the electro-optical efficiency of the color pixels of the first color line, and the fourth color line has at least one more row of color pixels than the first color line. This has the advantage that the compensation of the electro-optical efficiency described at the beginning is further improved and is also achieved for other colors.

[0027] In a further advantageous embodiment, it is provided that the color lines, in particular each of the color lines, have at least two rows, preferably at least three rows of pixels of the corresponding color of the color line. This has the advantage that brightness fluctuations between successively scanned color pixels can be compensated, since the scanning deflection results in a temporal averaging over different rows. As a result, stripe-like artifacts, which frequently occur when the brightness of the μLED is not completely precisely controlled, are avoided.

[0028] Therefore, in another advantageous embodiment, it is provided that each color line has a reserved row of color pixels, and the display unit is designed to control, i.e. activate or deactivate, the corresponding color pixels of the reserved row to replace the corresponding color pixels of at least one regular row classified as non-functional, the two color pixels each having the same position in the relevant row. Therefore, if one of the other rows fails, the color pixels of the reserved row replace the color pixels in one of the other rows. The classification as non-functional can be carried out during the manufacturing process, which reduces the rejection of goods, or it can also be determined as part of the calibration process after commissioning. In both cases, the sustainability and therefore the efficiency of the display system are improved.

[0029] In a further advantageous embodiment, it is provided that, for at least one color line of a display unit having more than one row of color pixels, i.e. at least two rows or at least three rows of color pixels, at least one row of color pixels of at least one other color line is arranged between at least two rows of color pixels belonging to the respective color line. Preferably, this applies to several or all color lines having several rows of color pixels. The color pixel rows of different colors arranged in this way, whose color pixels are arranged one behind the other in the scanning direction of the scanning deflection unit, are each assigned to a logical pixel of the display unit and thus to a pixel of the image information generated by the computer, are thus arranged in a comb-like manner in the scanning direction. Different electro-optical efficiencies of the color pixels are a prerequisite for such a comb-like arrangement of the different rows.

[0030] The distance between color pixels of the same color whose light is superimposed in the optical system is thus increased. This has the advantage that, distributed in the optical system in the scanning direction, the viewing angle varies more compared to a conventional compact arrangement in which all rows of color pixels of the same color are arranged directly adjacent to each other. Therefore, when the color pixel rows are arranged in a comb-like arrangement, the beam path passes through the existing optical device at different points in the transverse direction, resulting in an averaging effect on the inhomogeneities of the optical device. Such inhomogeneities can be, for example, scratches and / or contamination of the lens. In particular, when using, for example, Fresnel lenses, side wall artifacts and / or moiré effects can be reduced ("averaged out"). Therefore, this effect is particularly advantageous when the comb-like device is used for a screen unit and / or a scanning deflection unit using a Fresnel structure or lens. Fresnel lenses with so-called "eccentric side walls" (compared to the more common "sinusoidal side walls") are particularly advantageous. Therein, the macroscopic structural discontinuities of the Fresnel side walls are described as "eccentric". According to the prior art, these are selected as concentric circles centered in the middle of the lens. For example, an eccentric structure deviates the center of the structure from the center. This generally represents a degree of freedom, whereby the side walls or discontinuities can be selected so as to maximize the averaging effect of the proposed comb-like color lines. Alternatively or additionally, diagonal extensions of the Fresnel lenses used and / or reflecting hybrid Fresnel lenses can be provided. The spatial averaging over the inhomogeneities can also be improved by an arrangement of the pixels which is adapted to the distortion of the lenses used and which therefore deviates from the usual rectangular grid.

[0031] It can be provided that the rows of color pixels of different color lines are arranged in such a way that the distance between the rows of at least one color line with more than one row of color pixels is maximized within the associated logical pixel of the display unit. Thus, this spacing can be used as a maximization criterion for the arrangement of the rows of different color pixels, for example using a linear or quadratic weighting of the spacing of the rows within a comb-shaped color line. This optimizes spatial averaging.

[0032] Another aspect relates to a screen unit for one of the described embodiments of the eyeglass display system. Advantages and advantageous embodiments of the screen unit correspond to the features and advantages thereof associated with the screen unit of the described embodiments of the eyeglass display system.

[0033] The features and combinations of features mentioned above in the description, also in the introductory part, and the features and combinations of features mentioned below in the description of the drawings and / or shown individually in the drawings can be used not only in the combination indicated in each case, but also in other combinations without leaving the scope of the invention. Therefore, embodiments which are not explicitly shown and explained in the drawings, but which can be produced from the explained implementation by individual combinations of features, are also considered to be included and disclosed by the invention. Therefore, embodiments and combinations of features are also considered to be disclosed which do not have all the features of the originally formulated independent claims. Furthermore, embodiments and combinations of features are to be considered to be disclosed, in particular by the explanations set out above, which go beyond or deviate from the combination of features set out in the references to the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A more advantageous embodiment is shown with reference to the following figures, which explain the object according to the invention in more detail, without wishing to limit it to the specific embodiment shown here.

[0035] In the accompanying drawings,

[0036] Figure 1 shows the CIE-1931 color space, on the basis of which an exemplary first embodiment of a screen unit for an eyeglass display system is explained;

[0037] Figure 2 An additional CIE-1931 color space is shown for explaining an alternative embodiment of a screen unit for an eyeglass display system;

[0038] Figure 3 shows that the reference Figure 1 or Figure 2 An exemplary eyeglass display system of the described screen unit;

[0039] Figure 4 a to 4c show exemplary embodiments of the screen unit;

[0040] Figure 5 Another exemplary eyewear display system is shown;

[0041] Figure 6 shows exemplary lens technology suitable for eyewear display systems; and

[0042] Figure 7 An exemplary embodiment of a display element having comb-like rows of color pixels is shown.

[0043] In the figures, identical or functionally identical elements are marked with the same reference symbols. DETAILED DESCRIPTION

[0044] Figure 1 A CIE-1931 color space 10 with coordinates x and y is shown. In this color space, a color subspace 16 is spanned by four primary colors 11, 12, 13 and 14. The color space 10 is bounded by a boundary line 101, which is given by a monochromatic emission spectrum. In the example shown, the primary color 11, which can be called the second color, is a blue spectrum with a central wavelength of 475 nm. The primary color 12 is a green spectrum with an exemplary central wavelength of 525 nm. The primary color 12 can be called a third color. The primary color 13 is a red spectrum with an exemplary central wavelength of 640 nm. This color can be called a fourth color. The primary color 14 is an orange spectrum with an exemplary central wavelength of 580 nm. The primary color 14 can be called a first color. These four colors divide the sub-color space 16 into two sub-sub-color spaces 161 and 162. In the sub-sub color space 161, a significantly higher electro-optical efficiency can be achieved than in the sub-color space 162, because in this sub-color space 162, colors can only be generated by the first, second and third colors 14, 11, 12, while in the sub-sub color space 162, colors are generated by the first, second and fourth colors 14, 11, 13. This is due to the fact that the emitter element (e.g. the corresponding μLED) assigned to the fourth color 13 does not have to be activated for the color in the first sub-sub color space 161. Due to the longer wavelength, this has a significantly worse electro-optical efficiency than the emitter element assigned to the first color 14.

[0045] Also shown is a series of white points 15, the so-called CIE standard illuminations, which lie on the blackbody curve 17. CIE standard illuminations E, D50, D55, D65, D75 and D93 are shown here. White point 15W with associated RGB video signal R=G=B is calibrated to one of the CIE standard illumination white points 15 or a similar white point, depending on the respective application scenario, and is the only point 15, 15W that does not lie on the blackbody curve 17. In the present case, therefore, an extended color space 16 is used by using more than three different primary colors, whereby the partial color space 16 can be divided again into color subspaces 161, 162, with a partial color subspace 161 having a higher electro-optical efficiency and a color subspace 162 having a lower electro-optical efficiency. It is particularly advantageous here that the more efficient color space 161 contains the white point 15, in particular the white point 15W. This allows a white hue corresponding to the white point 15 or the white point 15W to be displayed in a particularly energy-saving manner.

[0046] In a particularly advantageous embodiment, the line 18 separating the partial color subspaces 161 and 162, the connecting line 18 connecting the first color 14 and the second color 11, is located near the white point 15 or the white point 15W, in particular the white point 15 that is particularly relevant for the respective application scenario. Since the white points 15 are arranged on the black body curve 17 according to their respective assigned color temperatures, this advantageous design corresponds to a substantially parallel course of the connecting line 18 and the high temperature section of the black body curve 17, which extends from the high temperature end of the black body curve 17 to the white point 15, for example, in the white point 15 corresponding to the standard illuminance D50, a temperature of about 5,000 K can be assigned to the white point 15 on the black body curve 17.

[0047] This means that in order to produce white light, almost only or only the first color 14 and the second color 11 have to be produced with high intensity, i.e. only color pixels of two different colors have to be activated. As a result, when displaying white text on a black background, or conversely, when displaying black text on a white background, only two emission spectra are present in the light in a dominant manner. This is advantageous for the color correction of the optical device, since only two basic wavelengths or wavelength ranges need to be corrected, instead of three wavelengths or wavelength ranges as is usually the case. In addition, the two wavelengths of color 11 and color 14 are particularly close together, differing by only 105 nm in the example shown. However, without the first color 14, the optical device in the example shown would have to be corrected for wavelengths of 475 nm, 525 nm and 640 nm, i.e., a wavelength range exceeding 180 nm instead of 105 nm. The first orange color thus achieves a technically simple correction of the color difference for the relevant case of displaying black and white text, and at the same time also increases the electro-optical efficiency in the eyewear display system used, since GaN (μ) LEDs exhibit a sharp drop in electro-optical efficiency for longer wavelengths.

[0048] Figure 2An exemplary embodiment with exactly two colors 14, 11 is shown. The corresponding eyeglass display system thus realizes a black and white representation and a color representation of fewer colors located on the connecting line 18. Therefore, in this case, the lens element as part of the associated display unit only needs to be chromatically optimized for the two colors 14, 11. Ideally, the color pixels that produce the two colors 14, 11 then have a spectrally narrow spectrum, for example by being realized as μLED GaN technology. Ideally, the individual emitters are selected in such a way that the connecting line 18 extends substantially parallel to the high-temperature section of the black body curve 17. For example, the connecting line 18 can be closest to the black body curve 17, or even touch or intersect the black body curve 17 at a point corresponding to the white point 15 desired for the respective application scenario. This means that the distance between the connecting line 18 and the black body curve 17 is minimum for the point of the black body curve corresponding to the preferred desired white point 15. In practice, this means that small deviations between the desired white point and the white hue that can be achieved by the two colors can be tolerated. Therefore, the standard white light cannot be reduced, and the black and white images produced with such a screen unit will have a color cast. The greater the deviation here, the greater the color deviation, so that a maximum permissible deviation must be specifically defined for the respective usage scenario of the display unit.

[0049] In the example shown, several points T are marked on the bold curve 17. ∞ , T 5500 , T 3000 , T 2500 , which correspond to the temperatures of ∞, 5500K, 3000K and 2500K respectively. Connect line 18 to the corresponding point T ∞ , T 5500 , T 3000 and T 2500 The distance, that is, the distance d ∞ , d 5500 , d 3000 and d 2500 The normal line on the connecting line 18 passes through the corresponding point T ∞ , T 5500 , T 3000 and T 2500 Depending on the application, the colors 14, 11 and the route of the connecting line 18 can be selected so that the maximum distance of the desired portion (e.g., the high temperature section) of the black body curve 17 extending from point T. to a predetermined temperature point (e.g., T2500) reaches a maximum predetermined value. The connecting line 18 can also intersect the black body curve 17 once or twice. The connecting line 18 can also be positioned in such a way that, for example, the quadratic deviation from the connecting line 18 to the desired portion of the black body curve 17 is minimized, thereby, for example, minimizing the quadratic error.

[0050] exist Figure 3, an exemplary eyewear display system 1 is shown, which has a line display unit 2 and a scanning deflection unit 3, wherein the line display unit 2 is used to emit light 34 as computer-generated image information, and the scanning deflection unit 3 is used to scan the display unit 2 and to deflect the light 34 emitted by the scanned display unit 2 into the user's eye 392.

[0051] The screen unit 2 has a display element 30 and a lens element 31, which is arranged in the optical path between the display element 30 and the scanning deflection unit 3. The scanning deflection unit 3 has a series of scanning partially transparent mirror elements 32, which are arranged one above the other in the z direction. At a given time, light 34 with an intensity distribution predetermined by the screen element 30 in the y direction is deflected to the eye 392 at each beam splitter 32. Only part of the light 34 hits the pupil 391 of the eye 302 and is thus perceived.

[0052] In this case, the beam splitter element 32 is designed as a scanning or scanner beam splitter element 32 and therefore has a rotation axis 33 extending parallel to the y-axis with maximum deflections 323 and 322 and a nominal deflection 321. Thus, the light 34 can be directed to the eye 392 at all scanning angles 341 between the maximum deflections 323 and 322, which correspond to the associated maximum angles 343, 342. Thus, a virtual two-dimensional image can be generated with the linear screen element 30 by a time-division multiplexing process. As is known, the brightness of the linear screen element 30 is controlled synchronously with the corresponding scanning angle 341. The main extension direction of the linear screen element 30 extends parallel to the y-axis into the drawing plane. This is also the direction of the relevant color line, as described below.

[0053] Figure 4 Various views of an exemplary linear or line-shaped screen element 30 are shown. On a carrier 45 (e.g., a silicon substrate with integrated circuit electronics), a plurality of LEDs (here μLEDs) are arranged in corresponding color lines 411, 412, 413, and 414. Each color line 411, 412, 413, 414 comprises a corresponding row 411a, 412a, 412b, 413a, 413b, 413c, 414a, 414b, ..., 414g of color pixels 401. Here, the number of rows is selected as an example. Each color line 411, 412, 413, 414 corresponds to a color 11, 12, 13, 14. For example, color line 414 may correspond to a first color 14, color line 411 to a second color 11, color line 412 to a third color 12, and color line 414 to a fourth color 13. Thus, a four-color line display is achieved.

[0054] Each group may optionally contain a reserved row 411', 412', 413', 414' with a reserved color pixel 402. Thus, if a defective color pixel 403 is detected in a color line (e.g., color line 414) and is classified as non-functional, an assigned reserved color pixel 404 may be used in its place by means of software. In this case, the two color pixels 403, 404 are arranged in a corresponding row, here row 414, at the same position in the x-direction, and therefore in the scanning direction 46, i.e., in the same column, and therefore assigned to the same logical pixel of the screen unit. Since the screen elements are scanned in the scanning direction 46 perpendicular to the y-direction in the x-direction, these reserved color pixels 402 may be arranged at a distance from the regular rows 411a, 412a, 412b, 413a to 413c, 414a to 414g. Advantageously, the rows 411a, 411′, 412a, 412b, 412′, 413a to 413c, 413′, 414a to 414g, 414′ of color lines each have the same x spacing 426 in the scanning direction 46, and the color pixels 401 of the row have a uniform y spacing 421 in the y direction, wherein the y spacing 421 perpendicular to the scanning direction is ideally the same as the x spacing 426 in the scanning direction. By using deformable lens elements 31, this can in principle also be achieved technically at different distances. The color pixels 402 or their illumination areas can in principle be of any shape, for example circular, square or rectangular. However, a rectangular design is particularly advantageous because, in combination with a μ-lens 47, such as Figure 4 b and Figure 4 As shown in FIG. 3 , as part of the lens element 31 , different angular distributions 481 and 482 can be arranged in the main plane of the screen element 30 , which correspond to the geometrical dimensions 422 and 423 of the illumination area in the x and y directions.

[0055] The distance between the color lines 411, 412, 413, 414, 424 is preferably selected as a multiple of the x-pitch 426, since the brightness information must be forwarded from row to row in the scanning direction 46 synchronously with the scanning beam splitter element 32. For each color line 411 to 414, i.e. for each color 11 to 14, the number of rows in the scanning direction 46 can be freely selected to compensate for any perceived differences in brightness by multiple exposures. For this purpose, the brightness information of each color pixel 401, which is designed here as a row of μLEDs, is also shifted by one row after scanning to the next row and displayed again. This increases the brightness for the eye 392.

[0056] exist Figure 5, another exemplary eyewear display system 1 is shown, which has a line screen unit 2 and a scanning deflection unit 3, wherein the line screen unit 2 is used to emit light as computer-generated image information, and the scanning deflection unit 3 is used to scan the screen unit 2 and to deflect the light emitted by the scanned screen unit 2 into the user's eye 392.

[0057] The display unit 2 has a display element 30 and a lens element 31, which is arranged in the light path between the display element 30 and the scanning deflection unit 3. The lens element 31 has an exemplary inhomogeneity 31x. The scanning deflection unit 3 has a series of scanning partially transparent mirror elements 32, which are arranged one above the other in the z direction. One of these mirror elements is shown here.

[0058] In the present case, the mirror element 32 is shown with two deflections 321 and 321′. This means that light from different positions 151, 152 on the display element 30 is imaged onto the same beam path 120 according to the beam paths 121, 122. The beam path 120 hits the pupil 391 of the eye 392 and is therefore perceived at the same position in space. As a result, the pixel information, i.e. the intensity values ​​of the pixels at the positions 152 and 151, are added, resulting in a higher total intensity. In addition, the beam paths 121, 122 pass through the optical device, in this case the lens element 31, at different angles. Therefore, inhomogeneities 31x or local artifacts present on or in the optical device can be averaged out. Such local artifacts typically occur when Fresnel lenses are used, when diffractive optical surfaces are used, when dust is present on the lens or when other inhomogeneities such as inclusions or bubbles are present as specified in DIN 10110. In particular, if several Fresnel lenses are passed one after another, a significant moiré effect occurs, which can be averaged out by the comb-like arrangement of the color pixels of the color lines at positions 151, 152. Further inhomogeneities occur when the microlenses are arranged seamlessly next to each other (see Figure 6 ). In particular at the transition from one microlens to the next, there may be discontinuities in the optical image which lead to visible artifacts.

[0059] Figure 6a to 6e show exemplary lens technologies that lead to discontinuities or inhomogeneities 31x. These are linear lenses, which also extend linearly in the xy plane depending on the orientation of the linear screen unit 30. Preferably, the lenses 31 are at least 3 times longer than they are wide, preferably 5 or 10 times longer. For example, they can have a length of 30 mm to 60 mm and a width of 2 mm to 10 mm. This results in an aperture area of, for example, 6×60 mm. In the case of the eyeglass display system 1, it should be noted that the effective pupil of the human eye is typically only 2 mm-3 mm, so only a portion is averaged over the aperture of the lens 31. This means that inhomogeneities 31x on the lens surface become critical very quickly and cannot be ignored, in contrast to photography, where, for example, a small amount of dust on the lens can still be tolerated. In addition, for regular, i.e. regularly repeated structures, it must always be considered that the linear screen unit 30 also has regularly arranged pixels, so that a moiré effect can be formed.

[0060] Figure 6 a) shows a microlens as proposed, for example, in the publication (Ratcliff, Joshua et al. "Thinning: Heterogeneous Microlens Arrays for Compact 180 Degree FOV VR Near-Eye Displays". IEEE Transactions on Visualization and Computer Graphics 26.5 (2020): 1981-1990.) as an optic for an eyewear display system. The individual microlenses 61 are in mechanical contact with each other at certain locations 622. Depending on the configuration, larger optically invalid gaps 621 may also occur. This results in discontinuities or inhomogeneities 31x, which can lead to artifacts in the image display. A time-sequential multiplexing process with a one-dimensional scanning process in the scanning direction 46, preferably with comb-like color lines, is averaged over these areas and a more uniform image can be produced.

[0061] exist Figure 6 In 6b and 6c, the microlenses 61 are again arranged in a row, and in this embodiment there is no non-optical gap 621. Instead, the microlenses 61 are seamlessly connected together, thereby Figure 6 b), the transition 63 between two closest adjacent microlenses 61 extends parallel to the scanning direction 46, so that no averaging is possible over the optical inhomogeneities 31x produced there. In an advantageous embodiment, as shown in 6c), the transition region 63 is at a non-zero angle to the scanning direction 46, i.e. not parallel to the scanning direction 46. As a result, the averaging effect of a line display having a plurality of lines in the scanning direction 46 can be used in combination with a time division multiplexing method, preferably in combination with comb-shaped color lines.

[0062] Figure 6d) and 6e) show respectively a Fresnel lens 31 with a uniform area 64 and with jumps 65 marked as lines in the relief function of the lens 31. Even with the Fresnel lens d), the scanning in the direction 46 has an averaging effect across the jumps 65, especially in the central area. However, if the Fresnel lens becomes larger and larger, the concentrically arranged discontinuities or jumps 65 in the shown linear Fresnel lens 31 with "sinusoidal side walls" get closer and closer to parallel alignment towards the edge, and the averaging effect decreases towards the edge until it practically disappears. Figure 6 e) shows an alternative and advantageous embodiment, in which care is taken to ensure that the discontinuities or jumps 65 in the relief function do not extend towards the edge parallel to the scanning direction 46, even for large Fresnel lenses. This type of Fresnel lens 31 may be referred to as a Fresnel lens 31 with "eccentric side walls". This approach is based on the fact that for a Fresnel lens there is a degree of freedom to freely choose the jumps in the relief function without having to change the underlying optical surface.

[0063] Figure 7 An exemplary embodiment of a display element 30 is shown, in which rows 411a-411f, 412a-412d, 414a, 414b of color pixels 401 are arranged in a staggered or comb-like manner on a carrier 45. The color pixels 401 can, for example, be implemented as μLEDs of colors 11, 12, 14 associated with respective color lines 411, 412 and 414. In the present embodiment, the first color 14 is exemplarily selected as blue, the second color 11 is exemplarily selected as red, and the third color 12 is exemplarily selected as green.

[0064] For reasons of higher light intensity, not only one row 411a-411f, 412a-412d, 414a, 414b but several rows of color pixels 401 of the colors within the respective rows 414, 411, 412 are realized. Moreover, due to different electro-optical efficiencies, not the same number of pixel rows are provided, but rather several rows of colors with color pixels 401 of low efficiency are provided: two rows 414a, 414b for the first color 14, six rows 411a-411f for the second color 11, and four rows 412a-412d for the third color 12. This allows a white point to be achieved in combination. The different color pixels 401 arranged one behind the other in the scanning direction 46 are superimposed in the user's eye 392 by the eyeglass display system 1 and thus together form a logical pixel, i.e. a predetermined logical pixel of computer-generated image information for each predetermined scanning cycle.

[0065] Advantageously, the individual colors 11, 12, 14 or color lines 411, 412, 414 are now not realized compactly next to each other, but are combed into each other. Figure 7 As shown, the rows of pixels can be arranged at a greater distance from each other in the x-direction, or alternatively more densely. The increased distance results in larger different viewing angles of the rows of one color distributed in the x-direction. These pass through the lens element 31 and other optical devices at different points in the lateral direction, resulting in a larger averaging effect compared to the inhomogeneities of the lens element 31 or other optical devices.

Claims

1. An eyeglass display system (1) for displaying a virtual image in a user's field of view, comprising: A screen unit (2) for emitting light (34) as computer-generated image information, the screen unit (2) having at least a first color line and a second color line, each color line having a different color (14, 11), each color line having at least one row of color pixels extending along the color line; a scanning deflection unit (3) for scanning the screen unit (2) and for deflecting computer-generated image information emitted by the scanned screen unit (2) into the eyes of a user; It is characterized in that The electro-optical efficiency of the color pixels of the first color line is lower than that of the color pixels of the second color line, and the first color line has at least one more row of color pixels than the second color line to compensate for the different electro-optical efficiencies.

2. The eyeglass display system (1) according to claim 1, characterized in that: The color pixel is or includes a light emitting diode having Light width less than 50 μm and / or less than 0.003 mm 2 of light-emitting area, and is particularly based on GaN technology.

3. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: The color pixels are rectangles with different side lengths.

4. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: The color (14) of the first color line is in the range of 560 nm to 650 nm, in particular in the range of 570 nm to 590 nm.

5. The eyeglass display system (1) according to the preceding claim, characterized in that The color (11) of the second color line is in the range of 400 nm to 490 nm, in particular in the range of 440 nm to 480 nm.

6. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: In the color space (10) according to the CIE-1931 standard chromaticity diagram, the connecting line (18) of the colors (14, 11) of the first and second color lines is substantially parallel to a section of the black body curve (17), the section including the high temperature end (T ∞ ) to the white point (15W), in particular to a temperature point (T 2700 ), preferably at a temperature of at most 1800K (T 1800 ) of the height of the bold curve (17).

7. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: The screen unit (2) has exactly two color lines.

8. The eyeglass display system (1) according to any one of claims 1 to 6, characterized in that: In addition to the first and second color lines, the screen unit (2) also has third and fourth color lines, the color (12) of the third color line is in the range of 500nm to 550nm, in particular in the range of 515nm to 535nm, and the color (13) of the fourth color line is in the range of 580nm to 650nm, in particular in the range of 590nm to 640nm.

9. The eyeglass display system (1) according to the preceding claim, characterized in that The electro-optical efficiency of the color pixels of the third color line is between the electro-optical efficiencies of the color pixels of the second color line and the first color line, and the third color line has at least one more row of color pixels than the second color line, and the first color line has at least one more row of color pixels than the third color line.

10. Eyeglass display system (1) according to one of the two preceding claims, characterized in that The electro-optical efficiency of the color pixels of the fourth color line is lower than that of the color pixels of the first color line, and the fourth color line has at least one more row of color pixels than the first color line.

11. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: The color line comprises at least two rows, preferably at least three rows of color pixels of the respective color of the color line.

12. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: Each color line has a reserved row of color pixels, and the display unit (2) is configured to control corresponding color pixels of the reserved row instead of corresponding color pixels of at least one regular row classified as non-functional, the two color pixels each having the same position in the associated row.

13. The eyeglass display system (1) according to any one of the preceding claims, characterized in that: For at least one color line of a display unit having more than one row of color pixels, at least one row of color pixels of at least one other color line is arranged between at least two rows of color pixels belonging to the respective color line.

14. Eyeglass display system (1) according to the preceding claim, characterized in that The rows of color pixels of different color lines are arranged such that the distance between the rows of at least one color line having more than one row of color pixels is maximized.

15. A screen unit (2) for use in an eyeglass display system (1) according to any one of the preceding claims.

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