DE3627113A1 - DISPLAY DEVICE IN A VIEWFINDER - Google Patents

Description

The present invention relates to a display device, more specifically, a display device in a viewfinder to certain types of photographic information in the viewfinder one photographic device, for example a camera, and display a VCR.

A given photographic information in the viewfinder a photographic device, for example a camera, and a video recorder, LEDs and Liquid crystal elements outside an observation field arranged. With such a display mechanism, the However, users receive an alarm indicator regarding overexposure or miss an underexposure. Furthermore is it is impossible to find a focus area and display an optimal exposure range.

Although electronic cameras and VCRs, e.g. H. "Smart" devices that have been developed are hardly any new information display devices in viewfinders been proposed. There is therefore a need for on the development of "intelligent" display devices, that meet the needs of users.  

Taking into account the disadvantages of the conventionally trained Display devices in viewfinders beat that present invention a superimposed display arrangement in which a liquid crystal display element in one Field of view, d. H. the optical path from one to the other photographed object of reflected light, arranged is. For example, in Japanese Laid-Open Patent 52-1 10 626 a display device in one Viewfinder described by a TN (twisted nematic) - Makes use of liquid crystal display element. Because with this Display element usually a polarizing plate The maximum available Efficiency in terms of light utilization at 50%, so that the viewfinder darkens in an undesirable manner becomes. In Japanese Patent Application Laid-Open 58-62 626 a display device in a viewfinder is described that of a GH (guest-host) liquid crystal display element Makes use of. Although with this display element a polarizing plate can be dispensed with pigment molecules always absorb light. This leads to efficiency in terms of light utilization again like the Japanese one disclosed Patent application 52-1 10 626 reduced and thus the Viewfinder is darkened. A hologram Display device proposed. This display device is in the optical path of the an outgoing light to be photographed and is illuminated by an LED or similar. Through the hologram forms even if there is no display, a shadow. This hologram display device is therefore not suitable as a display device in a viewfinder.  

Furthermore, it is impossible to have a versatile display of any numerical values using to achieve so-called 7-segment display elements.

Thus, the conventionally designed display devices darken in seekers the same and form in it Shadows off, although such display devices in convenient way to display information in the field of view can be used.

The invention has for its object a display device to create in a viewfinder that makes the viewfinder bright holds and while avoiding the disadvantages of conventionally trained Display devices in viewfinders display an ad effected within the field of observation.

The above object is achieved by the invention solved a display device in a viewfinder that a Diffraction grating, the shape of which at an interface or Interface between a first and a second material is defined, with at least one material variable refractive index for to be photographed by one Object has reflected light, and a control device to change the refractive index of the first and / or second material, this control device causes the light emanating from the object in a first state the diffraction grating essentially happens and in a second state from the diffraction grating is partially bowed, so that a corresponding pattern is shown.

Although in the display device proposed according to the invention in the viewfinder, which has the properties described above  has a display element in the optical path the light from an object to be photographed, d. H. in the Observation field, the light passes through the Viewfinder almost completely in the display-free state, so that darkening of the viewfinder is prevented. Furthermore is the observation field in the viewfinder is essentially free of one caused by the presence of the display element Shadow formation.

The diffraction grating used can have any shape. A single diffraction grating or a multitude of superimposed ones Diffraction gratings are in the direction of propagation of light formed by the object or omitted, so that in this way a novel display device in a viewfinder is provided.

The invention is described below using exemplary embodiments explained in detail in connection with the drawing. Show it:

Fig. 1 is a view showing a basic arrangement of a display element in a display device in a viewfinder;

FIGS. 2A and 2B show different lattice shapes of the display element of FIG. 1;

Fig. 3 is a graph showing the spectral transmittances of triangular and rectangular lattices as a function of the wavelengths in the visible light transmittance and the shielding state of the light;

FIGS. 4A to 4D are views showing the individual steps for producing the display device using the display element shown in FIG. 1;

Fig. 5 is a schematic view of an inventive display device in a view finder;

Fig. 6 is a schematic view of a combination of an exposure or focus sensor and the display device in the viewfinder;

Figures 7A to 7F views of different display patterns in the display device in the viewfinder.

8A to 8C are views for illustrating the production steps of another display device in a view finder.

Figures 9A to 9B are views for illustrating a method for driving the display device of Figure 8A to 8C..;

Fig. 10 is a view for explaining another basic arrangement of a display element, which is in an inventive display device in the viewfinder use;

Figures 11A and 11B show other lattice shapes of the display element of Figure 10;

Figures 12A to 12F are views of other arrangements of the display element of Figure 10;

Figures 13A to 13D are views for explaining steps of manufacturing a display device, wherein the display element of Figure 10 is used..; and

Fig. 14 is a perspective view of a spacer used in the display element of Fig. 10.

Fig. 1 shows a basic arrangement of a display element, which takes place at an inventive display device in a viewfinder usage. The figure serves to explain the principle of operation of such a device. Materials 1 and 2 with variable refractive indices have an optically anisotropic material. The display element further comprises transparent electrodes 3 , between which the materials 1 and 2 are arranged, and transparent optical elements 4 , which are each formed on the transparent electrodes 3 .

Light 5 falls on the display element in a direction indicated by the thick arrow. Polarization components 6 and 6 ' are perpendicular to the direction of the incident light 5th

In the display element of FIG. 1, a triangular grid, for example a liquid crystal or a birefringent crystal, is formed by an interface between the anisotropic materials 1 and 2 . The optical axes of the anisotropic materials 1 and 2 run in the direction of the arrows shown, ie in the direction of the grooves of the grating (perpendicular to the surface of FIG. 1) and in the direction of the row arrangement of materials 1 and 2 (to the right in FIG. 1) and left). Therefore, these optical axes are perpendicular to each other. The grating layer is arranged between the two transparent optical elements 4 , which have the transparent electrodes 3 on their surfaces.

Light with random polarization properties can generally be divided into the two polarization components 6 and 6 ' , which are perpendicular to each other, as shown in Fig. 1. It is assumed that the display element of FIG. 1 is operated via an electric field. In a switched-off state in which there is no electric field at the transparent electrodes 3 , the direction of polarization of the polarization component 6 of the incident light 5 coincides with that of the optical axis of the anisotropic material 1 . The polarization component 6 is diffracted under an exceptional index n _{e of} the anisotropic material 1 . Since the direction of polarization of the polarization component 6 is perpendicular to the optical axis of the anisotropic material 2 , the polarization component 6 is diffracted under an ordinary index n ' _{o of} the anisotropic material 2 . Correspondingly, the polarization component 6 'of the incident light 5 is diffracted by the anisotropic materials 1 and 2 under ordinary and unusual indices n _o and n' _e . Therefore, a diffraction grating is formed for the polarization components 6 and 6 ' , which has the refractive indices n _e and n' _o and n _o and n ' _e . In a state in which an electric field is applied to the transparent electrodes 3 , the directions of the optical axes of the anisotropic materials 1 and 2 are changed by the electric field depending on its size. At the same time, the refractive indices for the polarization components 6 and 6 'of the incident light 5 are changed depending on the degree of modulation (phase difference of the diffraction grating) of the grating. A predetermined electric field is applied to the anisotropic materials 1 and 2 , so that their refractive indices for the polarization components 6 and 6 ' correspond to each other. In this case there is no phase diffraction grating for the incident light 5 . Therefore, the incident light 5 simply passes through the grating consisting of the anisotropic materials 1 and 2 .

For example, if a positive dielectric nematic liquid crystal is used as anisotropic materials 1 and 2 ( n _o = n ′ _o and n _e = n ′ _e ), the liquid crystal molecules are oriented in the direction of the electric field after its application. The direction of alignment of the liquid crystal coincides with the optical axes. The polarization components 6 and 6 'of the incident light 5 pass through the grating including the liquid crystal, while the components 6 and 6' are diffracted under the usual index n _o . In the switched-off state, when there is no electrical field on the display element, the liquid crystal molecules are aligned in the direction of the arrows. The polarization components 6 and 6 'of the incident light 5 are diffracted by the grating, which has the refractive indices n _e and n _o . The diffraction efficiency µ 0 of the transmitted light of the 0th order, which was diffracted by the triangular diffraction grating of the liquid crystal, can be determined approximately according to the following equation (1):

where mean
λ : The wavelength of the incident light 5
Δ n : The difference between the refractive indices of the anisotropic materials 1 and 2 of the liquid crystal
T : The thickness of the liquid crystal layer
(ie the height of the grid).

If Δ n max = n _e - n _o , Δ n min = 0 and Δ nT = m λ (where m = 1,2,3 ..), then µ 0 = 0.

In other words, the polarization components 6 and 6 'of the incident light are diffracted by the diffraction grating and emitted as a higher order diffracted light. There are no 0th order light components. If Δ n = 0, ie if the refractive indices of the anisotropic materials 1 and 2 are identical with respect to the polarization components 6 and 6 ' , the incident light 5 simply passes through the grating as if it did not exist. All components of the transmitted light then belong to the 0th order. Since the refractive index difference Δ n fluctuates depending on the size of the electric field applied to the opposite transparent electrodes 3 , the diffraction efficiency µ 0 represented by equation (1) changes when the size of the electric field is controlled.

As can be seen from the previous description, even if the light is natural Light or from the object to be photographed reflected light that has random polarization properties has a light modulation, d. H. a Permeability control of the polarization components perpendicular to each other. A light modulation can therefore be achieved without sacrificing efficiency in with respect to the use of light.

In FIGS. 2A and 2B, different lattice types of display element are shown. FIG. 2A shows a display element with a rectangular grid, while FIG. 2B shows a display element with a sinusoidal grid. The same reference numerals as in Fig. 1 denote like parts of Figs. 2A and 2B.

The display element can be manufactured independently of the grid shapes ( FIGS. 2A and 2B). If the grid shape changes, equation (1) must be modified. For a rectangular grating, the diffraction efficiency with respect to the transmitted 0th order light can be determined in the following approximate manner:

Equation (2) is used when the grating spacing P is significantly larger than the wavelength λ of the incident light 5 . However, if the grating pitch P is equal to or less than the wavelength λ , the equations (1) or (2) which result from a simple diffraction theory cannot be used. If λ is P , the exact diffraction efficiency must be determined from a complicated simulation, taking into account the vector properties of the light waves.

Spectral property differences between different ones Hereinafter, grid shapes are detailed described.

FIG. 3 shows the spectral transmittance properties of the display element at a wavelength range of visible light from 400 to 700 nm when triangular and rectangular gratings are used. The transmissivity µ 0 is plotted along the ordinate, while the wavelength λ is plotted along the abscissa. The characteristic curves 7 and 7 ' reflect the properties of the triangular and rectangular lattice when light passes through them. The characteristic curves 8 and 8 ' reflect the characteristic properties of the triangular and rectangular grids when light is shielded. As can be seen from FIG. 3, the rectangular grating has good wavelength selectivity, while the triangular grating has almost no wavelength selectivity. In the pattern shown by the display element of FIG. 1 with light from an object, for example with illumination, a substantially rectangular grid is preferably used for a colored display, while a substantially triangular or sinusoidal grid is preferably used for a monochromatic display.

The shape of the grid is dependent on the Feasibility, the application of the photographic Device, the peripheral system of the Display device and technical specifications selected.

For a colored display, the color properties of the 0 th order light are determined by the diffraction grating by a phase difference which is received by the light originating from the object to be photographed. In other words, by controlling the product " Δ nT " in equations (1) and (2), 0th order light can be emitted with a desired transmittance. For the manufacture of the display element, this means that after determining the material with a variable refractive index, the height T of the grating is changed and set to an optimal value, so that the desired product Δ nT is obtained. By applying / removing the electrical field, the display element is switched between the transparent state and the state with the colored pattern.

The materials with variable refractive index can be classified into isotropic and anisotropic materials depending on their optical properties. The anisotropic materials are in particular liquid crystals and electro-optical crystals. Examples of anionic materials are PLZT, LiNbO ₃ , LiTaO ₃ , TiO ₂ , PMMA, CCl ₄ , KDP, ADP, ZnO, BaTiO ₃ , Bi ₁₂ , SiO ₂₀ , Ba ₂ NaNb ₅ O ₁₅ , MnBi, EuO, CS ₂ , Gd ₂ (MoO ₄ ) ₃ , Bi ₄ Ti ₃ O ₁₂ , CuCl, GaAs, ZnTe, As ₂ Se ₃ , Se, AsGeSeS, DKDP, MNA, mNA, urea, a photoresist, the above described nematic liquid crystal, a cholesteric liquid crystal , a smectic liquid crystal and a ferrodielectric liquid crystal. Of these materials, liquid crystals are the most suitable materials because they are cheap and can be easily controlled.

The display device designed according to the invention after passing and shielding (diffraction)  of monochromatic light reflected from the object Patterns and color samples by utilizing the Spectral transmission properties of the diffraction grating Show.

The grating is made using photolithographic techniques a resist pattern, a combination of a photolithographic Process and a dry etching, impression technique with a thermoset or a UV-hardened Resin, cutting with a ruler or Embossing made.

The energy required to control the refractive index of a material with a variable refractive index from an electric field, an electric current, a Magnetic field, thermal energy, pressure and light depending of the special properties of the material with changeable Refractive index can be selected. The control device to control the refractive index can be dependent of the type of energy in connection with others Elements that make up the display element are selected will.

The manufacturing process for the display device, in which the display element of FIG. 1 is used, is described below.

FIGS. 4A to 4D show the individual steps of manufacturing the display element of Fig. 1. The same reference numerals as in Fig. 1 denote the same parts in FIGS. 4A to 4D. A positive dielectric nematic liquid crystal is used as the anisotropic material.

As shown in FIG. 4A, both major surfaces of a glass substrate 4 called Corning 7059 (trade name of Corning Glass Works, USA) with the dimensions of 37 mm × 26 mm × 1 mm were polished to produce transparent flat surfaces. A thousand Å thick ITO film was placed on the surface of the substrate 4 to form a transparent electrode 3 . Then, an SiO insulation film 11 was placed across the transparent electrode 3 to align the liquid crystal molecules in the direction of the arrow of FIG. 4A. An ITO film was used to form a patterned transparent electrode 3 ( FIG. 4C) on a glass substrate 4 that was identical to the substrate 4 described above. An SiO insulation film was formed across the patterned transparent electrode 3 to align the liquid crystal molecules in the direction of the arrow of FIG. 4C. A wave-shaped transparent spacer 9 was formed by rolling as shown in Fig. 4B. The height T of the transparent spacer 9 , ie the distance from the tip to tip, was 2.3 μm. The two glass substrates 4 were used to hold the transparent spacer 9 between them so that the transparent electrodes 3 faced each other. Positive dielectric nematic liquid crystals 10 and 10 ' were filled and sealed in the spaces between the upper and lower glass substrates 4 to manufacture the display device shown in Fig. 4D. In this case, the liquid crystal 10 was aligned in the direction of the grooves of the grid, while the liquid crystal 10 'was aligned in the direction of the grid alignment.

In the display elements of Fig. 1 and 2A and 2B, the materials were arranged alternately with optical anisotropy. However, optically isotropic materials can also be arranged alternately. More specifically, in the arrangement of FIG. 1 may o instead of the optically anisotropic material 1 and a transparent optical element in place of the optically anisotropic material 2, a transparent material with variable refractive index or a liquid. Ä. Are used with variable refractive index. The refractive index of the material with a variable refractive index is changed in order to carry out the corresponding switching process in relation to the diffraction. If an optically isotropic material is used as the material with a variable refractive index, the light modulation can be carried out essentially independently of the state of the polarization plane of the incident light.

Instead of the optically anisotropic material 1 , a transparent optical element can be used together with the optically anisotropic material 2 to form a display element. In this case, if the refractive index of the optically anisotropic material 2 of a liquid crystal or the like coincides with that of the transparent optical element, the light reflected by the object can pass the grating in a predetermined state. However, if the refractive index of the optically anisotropic material 2 differs from that of the transparent optical element, the diffraction grating acts to partially diffract the light reflected from the object to be photographed, thereby indicating a pattern of photographic information. With such an embodiment, a halftone display can be performed without considering the polarization properties of the object in the same manner as described above. In any case, the viewfinder can be kept bright.

Fig. 5 shows schematically an arrangement with the display device in the viewfinder. The arrangement comprises the display device 12 shown in FIG. 4D, a focusing element 13 with a Fresnel lens, a converging lens 14 , a pentaprism 15 , an eyepiece 16 and a reflection mirror 17 .

The light reflected by the object to be photographed, which is guided into the viewfinder by the reflection mirror 17 , passes through the display device 12 , the focusing element 13 with the Fresnel lens and the converging lens 14 and is imaged by the pentaprism 15 as an upright image. This upright image strikes the user's eye through the eyepiece 16 . When a square wave AC field is applied to the electrodes of the display device 12 , the display device 12 is kept in the translucent state through the field of view in the viewfinder. The user can clearly observe the object image through the eyepiece 16 . As a precautionary indicator for underexposure or an in-focus state, corresponding display patterns are de-energized depending on signals from an exposure sensor and an in-focus sensor. These display patterns are kept in the 0-order light-shielded state and therefore carry out a display.

In the viewfinder device of this embodiment, the positive dielectric nematic liquid crystal is used as the variable refractive index material in the same manner as shown in Figs. 4A to 4D. The display-free state is obtained by applying an electrical field, while the display state is achieved by de-energizing the electrical field (ie normally closed). However, when a negative dielectric nematic liquid crystal is used in the arrangement of Figs. 4A to 4D, the non-display state can be obtained by de-energizing the electric field, while the display state is achieved by the excitation of the electric field (ie, normally open). When a nematic liquid crystal with negative dielectric properties is used, the liquid crystal molecules align in a direction normal to the surface of the lattice. When an electric field is applied in a direction perpendicular to the surface of the grid, the liquid crystal molecules tilt in a direction perpendicular to the direction of the electric field (ie, the direction of the grooves of the grid).

It is also possible to use a material with variable Refractive index to use that in the above described is optically isotropic to this Way to reach the normally open state. In this case, the refractive index of the transparent falls optical element with that of the material  variable refractive index in the static state where no electric field applied to the display device is together.

Different display patterns will now be described in connection with FIGS. 6 and 7A to 7F. A transparent optical element 18 has a half mirror which is inclined at the center at an angle of 45 ° so that light is partially guided through the lens to an exposure or focusing detection light receiving element 21 . The arrangement of FIG. 6 also includes an exposure or focusing detector for receiving an output signal from the light receiving element 21 and for analyzing the F number and a drive variable for the lens. A voltage generator 23 receives a detection signal from the detector 22 and generates a predetermined voltage depending on this signal. An output signal of the voltage generator 23 is supplied to the display device 12 .

FIG. 7A shows an underexposure display, FIG. 7B shows an overexposure display, FIG. 7C shows a display for optimal exposure, FIG. 7D shows a display for focal point proximity, FIG. 7E shows a display for focal distance and FIG. 7F shows a focus display (in Focus). Different patterns can be displayed within the field of view with high contrast without darkening the image. If the display device is switched off, it does not affect the observation of the object to be photographed.

To display the light emanating from the object a predetermined pattern is described in the above To carry out embodiment, a grid can only be formed in the pattern section, or the electrode or similar is patterned along the display pattern in the grid area. In this case, a static pattern display optionally at a predetermined position within the Field of view.

To perform a dynamic display, i. H. one Matrix drive to achieve the same function as the normal liquid crystal display device becomes one Grid formed in the entire area of the observation field, and it can create a transparent X-Y matrix will. Alternatively, the luminous dots are through the display elements are formed and over a transparent X-Y matrix or a thin film transistor for example operated according to a time division scheme.

In the embodiment described above, the display device 12 is arranged between the converging lens 14 and the focusing element 13 . However, if a system is located within the viewfinder, the display device 12 may be located near the eyepiece 16 . If the legibility of the object image and the photographic information patterns, light signals (described below) and problems of the display device are taken into account, the display device 12 should preferably be arranged in the vicinity of the focusing element 13 . When the display device is used within the viewfinder of a single-lens reflex camera or the like, as shown in Fig. 5 or 6, it must be located close to the focusing element 13 or at a position conjugated to the position of the focusing element 13 in order to be able to do so Focusing element 13 (focusing screen) of being able to observe the focused object image and the displayed pattern without dioptical difference. However, when the display device 12 is used in the viewfinder of a video camera or the like, it can be arranged in a desired position by designing the viewfinder as an afocal system. Compared to the case where the display device of this embodiment is used in the viewfinder of the single-lens reflex camera, a certain flexibility in configuration can be achieved. The display device is preferably arranged between the focusing element 13 and the eyepiece 16 , the distance between the display device 12 and the focusing element 13 being 1 mm or less. In practice, if the distance exceeds 1 mm, either the object image or the display pattern is out of focus due to a dioptical difference.

Since the display device arranged in the viewfinder makes use of a diffraction phenomenon of the diffraction grating, a large number of higher-order light components which are generated at the time of the display become flare light. This light, which consists of the higher order components, can be eliminated if the grid spacing is reduced below a predetermined value in order to increase the separation angle between the components of higher and lower orders. This light therefore does not strike the pupil of the eyepiece 16 and is eliminated. Those higher order light components that are spaced from the pupil are normally absorbed in the inner surface of the viewfinder. In the viewfinder of the single-lens reflex camera of FIG. 5 or 6, however, a change in the aperture causes a change in the F number, so that the angle of incidence of the object light striking the display device 12 through the focusing element 13 is changed. If a large F number is selected, it can be assumed that most of the light components from the object to be photographed are incident perpendicularly on the display device 12 . Therefore, by defining the distance in the manner described above, the influence of the higher order light components can be reduced. However, if a small F number is chosen, it must be assumed that the majority of the light components from the object strikes the display device 12 obliquely, so that the direction of the higher order light components from the grating of the display device 12 is not simply due to the Distance can be defined. The inventors have made extensive studies on grating shapes to solve the above problem and found a desirable grating shape for use in a camera viewfinder. The rectangular grid of Fig. 2A has the high energy of ± 1 diffracted light components. If the display device is to be used in the camera viewfinder, the triangular or sinusoidal grating of FIG. 1 or 2B or a trapezoidal grating is preferred. In particular, the trapezoidal grid is particularly preferred in terms of feasibility and a colored display.

The characteristics of the arrangement described above also apply to the display device shown in FIGS . 10 to 12F.

When the display element or the display device of FIGS. 10 to 12 described above is installed in a viewfinder, the light from the object is preferably incident from the substrate side or the side of the display device with the low refractive index element. With this embodiment, a high contrast can always be maintained. It is further preferred to arrange the three-dimensional surface of the grating formed on the elements, for example a plurality of substrates, in one direction in order to improve the contrast. Therefore, it is preferred to have light from the object hit the flat surface of the grating element as shown in Figs. 12B, 12E and 12F.

An embodiment is described below in which a ferroelectric liquid crystal is used as the material with a variable refractive index ( FIG. 1).

FIGS. 8A to 8C are views for explaining the steps in manufacturing a display element using a ferrodielectric liquid crystal. The same reference numerals as in the previous embodiments denote the same parts of this embodiment. The steps for producing the display element for using the ferrodielectric liquid crystal are described below.

Using the same procedures as described in connection with FIG. 4, two Corning 7050 glass substrates each measuring 37 mm × 26 mm × 1 mm were produced. As shown in Fig. 8A, a 1000 Å transparent ITO electrode was formed on the entire surface of a glass substrate. 1000 Å thick ITO transparent electrodes 25 and 25 ' were interleaved in the pattern portion of the other glass substrate as shown in Fig. 8B. The electrode elements of the interdigitally arranged electrodes 25 and 25 ' were formed alternately, as shown in Fig. 8C. PVC (polyvinyl carbazole films) were formed on the two glass substrates 4 and rubbed to align the liquid crystal molecules to the direction of the interdigital electrodes 25 and 25 ' . As shown in Fig. 8C, the two glass substrates 4 were then used to place a spacer therebetween and glued thereto, so that the electrode 3 was opposite the electrodes 25 and 25 ' . A ferrodielectric liquid crystal MORA-8 was filled and sealed into the spaces between the glass substrates.

The operation of the display device manufactured in the manner described above will now be described in connection with FIGS. 8A to 8C and 9A and 9D.

If the display device is not actuated, there is neither a voltage on the transparent electrode 3 nor on the interdigitally arranged electrodes 25 and 25 ' . The optical axis of the ferroelectric liquid crystal 24 is kept unchanged as shown in Fig. 9A. The refractive index anisotropy is the same within a plane, so that the grating is overridden. In this case, the incident light simply passes through the grating. In display mode, however, voltages with the same absolute value, but different polarities, ie ± 5 V, are applied to the transparent electrode 3 and the electrodes 25 and 25 ' . In this case, the optical axes of the molecules of the ferroelectric liquid crystal 24 , which are arranged on the electrodes 25 and 25 ' corresponding positions, are alternately inclined in opposite directions, as shown in Fig. 9B. When the relationship between the thickness T of the liquid crystal layer, the refractive index difference Δ n 'and the wavelength of the incident light is controlled to satisfy Equation (2), light emanating from the object is partially shielded by the display pattern area. Therefore, a high contrast display can be performed within the observation field while keeping the whole image bright.

If a liquid crystal has a storage ability, as is the case with ferroelectric liquid crystal, the initial orientation is set immediately, after which the polarity of the electric field applied to one of the electrodes 25 and 25 'is changed in order to restore the initial state.

The display devices of those described above two embodiments have patterns that appear should be. However, the display device in the viewfinder can operated in matrix form. If a matrix operation  by combining the display device with different camera sensors, one can Focus indicator, an indicator related to one optimal exposure u. Ä. Realized so that different Display forms can be executed.

As described above, the display device external energy in the viewfinder, for example a electric field, on the control device on the Material with variable refractive index applied, to cause the diffraction grating to appear in the viewfinder or disappears from it. If the diffraction grating is off disappears from the viewfinder, the light passes from the object the viewfinder in a simple way so that it is kept bright becomes. If the diffraction grating according to a predetermined Pattern appears, that is through the pattern section Urgent light diffracted and partially diffracted Higher order light components converted so that Pattern with the light of the 0th order is displayed. If an ad by operating a matrix that consists of a large number of illuminated dots the diffraction grating appears depending on a control signal at a desired location within of the observation field.

Another embodiment of a display element that in a display device designed according to the invention used in the viewfinder is described below.

Fig. 10 shows the basic arrangement of the display element used in the display device in the viewfinder to explain the display principle in the same manner as in Fig. 1. The arrangement shown here has a transparent spacer 9 . The same reference numerals as in Fig. 1 denote the same parts in Fig. 9. The characteristic feature of the display element of this embodiment is that incident light 5 penetrates through a grating consisting of two layers. The first layer (seen from the incident side of the light 5 ) comprises a first grating which consists of a transparent optical element 4 with a refractive index n _g and an anisotropic material 1 . The second layer comprises a second grating, which consists of a transparent optical element 4 with a refractive index n _g and an anisotropic material 2 .

As shown in FIG. 10, the optical axis of the anisotropic material 1 of the first layer is aligned with the direction of the grooves of the grating (ie, a direction perpendicular to the surface of FIG. 10). The optical axis of the anisotropic material 2 of the second layer is aligned to align the grating (ie to the right and left in FIG. 10). The optical axes of the anisotropic materials 1 and 2 are changed by external energy, for example an electric field. The incident light 5 is diffracted under the diffraction indices of the anisotropic materials 1 and 2 . In the static state, in which no electrical field is present on the display element, a polarization component 6 of the light 5 falling on the first layer is diffracted under an exceptional index n _{e of} the anisotropic material 1 . A polarization component 6 ' is diffracted under an ordinary index n _{o of} the anisotropic material 1 .

In the second layer, the polarization component 6 of the incident light 5 is diffracted under an ordinary index n ' _{o of} the anisotropic material 2 , while the polarization component 6' is diffracted under an extraordinary index n ' _{e of} the anisotropic material 2 . The diffraction efficiency µ 01 of the 0th order diffracted light in the first layer and the diffraction efficiency µ 02 of the light in the second layer can be represented by the following equations (1) ′ and (1) ″:

where mean
n _g : The refractive index of the transparent optical element 2 , which forms the grating of the first layer
T : The height of the grid of the first layer
n ′ _g : the refractive index of the transparent optical element 2 , which forms the second layer of the grating
T ′: the height of the lattice of the second layer
λ : The wavelength of the incident light.

If n = 0, µ 01 = 1. However, if n ′ = 0, µ 02 ′ = 1. If Δ nT = m λ (where m = 1, 2, 3, ..), µ is 01 = 0. If Δ n′T ′ = m λ (where m = 1, 2, 3 ..), µ 02 ′ = 0. In other words, if the first layer equates n _o = ng or n _e = n ' _g - fulfilled, one of the polarization components 6 and 6' runs through the first layer. The other is modulated according to equation (1) '. If the second layer fulfills the equation n ′ ₀ = n ′ _g or n ′ _e = n ′ _g , one of the polarization components 6 and 6 ′ runs through the second layer. The other is modulated according to equation (1) ″.

When an electric field is applied to the anisotropic materials 1 and 2 , their optical axes are changed, and the refractive indices associated with the polarization components 6 and 6 'of the incident light 5 are changed accordingly. In other words, the incident light 5 is modulated by the first and second layers according to equations (1) 'and (1) ″ with changes in Δ n .

For example, if the anisotropic materials 1 and 2 consist of the same material, then n _e = n ' _e and n ₀ = n ' ₀ . If the initial conditions exist n _g = n ′ _g = -n _{0 ′} T = T ′ and n _e - n _g · T = m λ , the diffraction efficiency of the first and second layers for the 0th order diffracted light can be determined by equation (1) can be expressed. In this embodiment, it is assumed that the refractive index of the spacer 4 is essentially = n _g . In the static state, the polarization component 6 'of the incident light 5 penetrates the first layer. However, the polarization component 6 is diffracted according to equation (1), so that µ 0 = 0. The 0 th order light is not emitted from the first layer and becomes higher order light components. These components are released from the first layer as a diffracted component. In the second layer at the polarization component 6 ' according to equation (1) µ 0 = 0. Light of the 0th order is diffracted, and the diffracted components of the higher order are emitted by the second layer. The polarization component 6 penetrates the second layer. Therefore, zero-order light components are not output from the display element of this embodiment.

When a given electric field is applied to orient the optical axes (direction of orientation) of the liquid crystals 1 and 2 in a direction perpendicular to the grating surface, that is, in the direction of propagation of the incident light 5 , the polarization components 6 and 6 'of the incident light 5 are among the ordinary indices n _{0 of} the liquid crystals 1 and 2 diffracted in the first and second layers. The incident light 5 penetrates the display element and is emitted as a 0 th order light.

Modulation of the object light can be done by Removing the electric field without the Using polarizing plates or the like will.

In the display element shown in Fig. 10, the direction of alignment in the grids of the respective layers is the same. However, the alignment directions of the grids of the respective layers are not limited to one direction. Each grid has a triangular shape. As shown in Fig. 11, however, the grating can also have a rectangular or sinusoidal shape. The desired function can be achieved regardless of the grid shape. When the triangular shape of the grating is replaced by a rectangular shape, the diffraction efficiency represented by equation (1) is replaced by equation (2).

Furthermore, the corresponding grids can be different Own shapes. The lattice shape is regarding a simple feasibility, the technical specification u. Ä. determined.

FIGS. 12A to 12C show the basic arrangements of display elements that are controlled via an electric field. Two grids arranged one above the other are formed in each element. In the display element of FIG. 12A, transparent optical elements 4 each have triangular grids. The transparent optical elements 4 are spaced slightly apart from one another via a flat transparent spacer 9 . Anisotropic materials 1 and 2 are filled into the spaces between the transparent optical elements 4 . Transparent electrodes 3 for controlling the properties of the anisotropic materials 1 and 2 are formed along the grids of the transparent optical elements 4 .

In the display element of Fig. 12B, a grating is formed on the inner surface of one of the transparent optical elements 4, and a hole formed on a transparent spacer grid 9 faces the other transparent optical element 4 with respect to without grid. The anisotropic materials 1 and 2 filled between the transparent optical elements 4 are divided into upper and lower layers. The transparent electrodes 3 are each formed on the inner surfaces of the transparent optical elements 4 . In the display element of FIG. 12C, a pair of transparent optical elements 4 with flat transparent electrodes 3 are arranged on their inner surfaces at a distance from one another by a transparent spacer 9 , which has grids on both main surfaces. Anisotropic materials 1 and 2 are filled between the transparent optical elements 4 , between which the transparent spacer 9 is located.

FIGS. 12D and 12E show essentially the same basic arrangement as FIGS. 10 and 11. In the display element of FIG. 12D, a transparent heating element 90 is used instead of the spacer 9 in order to separate the anisotropic materials 1 and 2 into upper and lower layers to divide. In the display element of FIG. 12E, a transparent heating element 90 is used instead of the transparent electrodes 3 of FIG. 12B.

The embodiment of FIG. 12 consists of an upper and a lower display element, each of which is provided with an egg grid. Anisotropic materials 1 and 2 are filled into the upper and lower display elements and have different optical axes. The grids are each formed on the inner surfaces of the transparent optical elements 4 of the display element. An electric field is applied to the transparent electrodes 3 formed on the elements 4 so as to control the optical axes of the anisotropic materials 1 and 2 .

The operating principle of the display elements described above and a method for producing the display element of FIG. 12A are described below.

Fig. 13 shows steps in the manufacture of the display element of Fig. 12A. Liquid crystals 10 and 10 ' with different orientation directions are shown in Figs. 13A to 13D. The same reference numerals as in Fig. 1 denote the same parts in Figs. 13A to 13D.

Both main surfaces of a transparent substrate 4 made of PBMA resin (37 × 26 × 1 mm ³ and n _g = 1.56) were processed into transparent surfaces. A triangular lattice was completely embossed on one of the main surfaces of the substrate 4 with a lattice pitch of 3 µm and a depth of 2.4 mm, as shown in Fig. 13A. Thereafter, a 1000 Å ITO film 3 was formed on the entire surface of the lattice substrate 4 .

By performing the same operations as in Fig. 13A, another transparent PBMA substrate 4 was manufactured with the display pattern shown in Fig. 13B. A 5 µm thick Teflon spacer 9 with top and bottom surfaces rubbed in opposite directions ( Fig. 13C) was placed between the two transparent PBMA substrates 4 . Positive dielectric liquid crystal materials MBBA ( n ₀ = 1.56 and n _e = 1.786) 10 and 10 ' were in between the surface of the upper electrode 3 and the surface of the spacer 9 and between the surface of the lower electrode 3 and the lower surface of the Spacer 9 filled, whereby the display element shown in Fig. 13D was produced.

A method of manufacturing the display element of FIG. 12C is described below. Rectangular grids ( Fig. 14) with a grating spacing of 3 µm and a depth of 1.8 µm were formed in both surfaces of a transparent PMMA resin film 26 (which served as a spacer) by using a rectangular wave hot roller. The grids on the top and bottom surfaces of film 26 were perpendicular to each other.

Both surfaces of 2 PK7 substrates (37 × 26 × 1 mm ³ and n _g = 1.49) were polished to transparent, flat surfaces. ITO films 1000 Å thick were formed on the entire surface of one substrate and on the surface of the other substrate in the form of a pattern shown in Fig. 13B. The two PK7 substrates were then spaced apart so that the ITO films faced each other. Then a latticed film 26 was placed between the PK7 substrates. A positive dielectric liquid crystal ZLI-2141-000 (available from Merck & Co., Inc.) with n ₀ of 1.49 and n _e of 1.64 was placed between the top PK7 substrate and the grating of the film 26 and between the lower PK7 substrate and the grid were filled in, and the liquid crystal was oriented under pressure along the grooves of the grid. The axis of the upper liquid crystal layer was perpendicular to the axis of the lower liquid crystal layer.

The display elements of FIGS. 10 to 14 are for the display device in the seekers in accordance with FIGS. 5 and 6, suitable to cause an effective modulation of the object light and a monochromatic and color display with high contrast.

In the display elements shown in FIGS. 1 to 9 and FIGS. 10 to 14, the liquid crystal is preferably a material with a variable refractive index taking into account the difference between the unusual and ordinary index n _e and n ₀ and the drive energy level.

In the display elements shown in FIGS. 10 to 14, the anisotropic materials need not be arranged alternately. For example, the liquid crystals or the like do not have to be filled in alternately using a thin spacer. Rather, these display elements can be produced in a simple manner in comparison to the elements according to FIG. 1. Since the elements of Figs. 10 to 14 display using superimposed diffraction gratings, the patterns of the upper and lower diffraction gratings must be precisely aligned. If this is not the case, pattern errors occur. In particular, when a plurality of display elements are used, as shown in Fig. 12F, the diffraction gratings superimposed on each other must be arranged close to each other in view of a favorable energy consumption, for example an electric field. Even with the individual display elements each having a plurality of diffraction gratings, as shown in Figs. 12A to 12E, the distance between the diffraction gratings and the thickness of the spacer and the substrate must be kept to a minimum.

If the display elements of the above Embodiments with the liquid crystal as a material variable refractive index is used Orientation of the liquid crystal molecules of great importance. It is known that a liquid crystal (in particular a nematic liquid crystal) by a Micropattern, for example one designed according to the invention Grid, can be oriented. To different Specifications, for example the drive energy (i.e. an electric field) and the response time of the Element, the grid spacing of the the first and second materials that make up the grid, another lattice manufacturing process is used and / or a molecular orientation treatment, for example a rubbing process or a cross separation, carried out in this way an optimal To get orientation.  

If taking into account the orientation function the orientation of the top and lower liquid crystal layer perpendicular to each other the grooves of the grid are preferred arranged perpendicular to each other.

Since the display elements designed according to the invention in the viewfinders have no polarization properties, can polarization plates come to an end. In ad-free Condition can object light with high permeability penetrate every display element. However, if one photographic information is displayed, its Patterns are displayed in the viewfinder with high contrast. The appropriate precautionary samples and photographic information can be viewed at any time anywhere within and outside the scope of the Viewfinder appear while the size and brightness of the observation field is maintained.

Taking advantage of the wavelength selectivity of the grating, d. H. of the diffraction grating, a color display in the viewfinder can be realized without using a color filter or similar to have to.

Different display schemes can be used. Examples this is a scheme for displaying a given one Display pattern via a static drive, a Scheme for displaying a desired pattern on a anywhere via a matrix drive, for example the display of digits with 7-segment display elements, or similar  

According to the invention, a display device is thus in one Proposed viewfinder that includes a diffraction grating its shape at an interface between a first and a second material is determined. At least one material has a variable refractive index for the light reflected from an object to be photographed. The display device further comprises a control device to change the refractive index of the first and / or second material, the control device causing that the light from the object is the diffraction grating in a first Condition almost completely happened and from the diffraction grating partially bent in a second state.

Claims (38)

1. Display device in a viewfinder, characterized by : a diffraction grating which is arranged in an optical path of light ( 5 ) emanating from an object to be photographed, the shape of the diffraction grating being essentially determined by an interface between a first and a second material ( 1 , 2 ) is determined and at least one of these materials is a material with a variable refractive index, the refractive index of which is variable relative to the light ( 5 ) emanating from the object; and a control device for changing the refractive index of the material ( 1, 2 ) with a variable refractive index, which is able to change the refractive index of the corresponding material so that the light originating from the object ( 5 ) essentially changes the diffraction grating in a first state simply penetrates and part of the light emanating from the object is diffracted by the diffraction grating in a second state to display a pattern. 2. Device according to claim 1, characterized in that the diffraction grating is a phase Diffraction grating includes. 3. Device according to claim 2, characterized in that that the diffraction grating is rectangular Relief pattern includes. 4. The device according to claim 2, characterized in that the diffraction grating is a relief pattern embraced with inclination. 5. The device according to claim 1, characterized in that the diffraction grating at one point is arranged to an object image in the viewfinder or a focusing position of the object image optically is conjugated. 6. The device according to claim 5, characterized in that the diffraction grating is arranged in the vicinity of a focusing element ( 13 ). 7. The device according to claim 1, characterized in that the material ( 1, 2 ) with a variable refractive index comprises a liquid crystal. 8. The device according to claim 7, characterized in that that the liquid crystal is a nematic Liquid crystal with a positive dielectric property comprises and that the liquid crystal in one direction in substantially perpendicular to the direction of orientation of the  Diffraction grating in the first state and in one direction parallel to the direction of orientation of the diffraction grating is oriented in the second state. 9. The device according to claim 8, characterized in that the control device is a device to apply an electrical field to the Has liquid crystal. 10. The device according to claim 8, characterized in that that the liquid crystal towards the grooves of the diffraction grating in the second state is oriented. 11. The device according to claim 7, characterized in that that the liquid crystal is a nematic Liquid crystal with negative dielectric properties includes. 12. The apparatus according to claim 7, characterized in that the liquid crystal is a ferrodielectric Includes liquid crystal. 13. Display device in a viewfinder, characterized by: a diffraction grating which is arranged in an optical path of light ( 5 ) emanating from an object to be photographed and the shape of which is essentially defined by an interface between a first and second material ( 1, 2 ) is determined, the direction of the optical axes of the first and second material being variable; and control means for changing the direction of the optical axes of the first and second materials ( 1, 2 ), capable of changing the directions of the optical axes of the first and second materials ( 1, 2 ) so that that of the object outgoing light essentially passes the diffraction grating in a first state and part of the light from the object is diffracted by the diffraction grating in a second state to display a pattern. 14. The apparatus according to claim 13, characterized in that the optical axes of the first and second material ( 1, 2 ) oriented in one direction in the first state and are substantially perpendicular to each other in the second state. 15. The apparatus according to claim 14, characterized in that the first and second material comprises a liquid crystal ( 24 ). 16. The apparatus according to claim 13, characterized in that a transparent spacer ( 9 ) between the first and second material ( 1, 2 ) is arranged, which has a shape which corresponds to that of the diffraction grating. 17. A display device in a viewfinder, characterized by: first and second diffraction gratings, which are arranged one above the other in an optical path of light ( 5 ) emanating from an object to be photographed, and whose shape is essentially defined by interfaces between transparent elements ( 4 ) and materials ( 1, 2 ) is determined with a variable refractive index, wherein the material with a variable refractive index can be optically anisotropic; and control means for changing the refractive indices of the variable refractive index materials ( 1, 2 ) of the first and second refractive gratings and capable of controlling the refractive indices of the variable refractive index materials so that the light ( 5 ) emanating from the object is the first and second diffraction gratings pass in a first state essentially simply and part of the light from the object is diffracted by the first and second diffraction gratings in a second state to display a pattern. 18. The apparatus according to claim 17, characterized in that the first and second diffraction gratings are arranged in two different planes, which are arranged substantially perpendicular to the direction of propagation of the light emanating from the object ( 5 ). 19. The apparatus according to claim 18, characterized in that the first and second Diffraction gratings include phase diffraction gratings. 20. The apparatus according to claim 19, characterized in that the first and second Diffraction gratings include rectangular relief patterns.   21. The apparatus according to claim 19, characterized in that the diffraction grating relief pattern include, each having an inclination. 22. The apparatus according to claim 19, characterized in that the first and second Diffraction gratings have an identical groove alignment direction exhibit. 23. The device according to claim 19, characterized in that that the groove alignment directions of the first and second diffraction gratings run essentially perpendicular to each other. 24. The device according to claim 19, characterized in that protrusions of the first and second diffraction grating along one direction are oriented. 25. The device according to claim 19, characterized in that protrusions of the first and the second diffraction grating face each other. 26. The apparatus according to claim 17, characterized in that the materials with variable Refractive index a liquid crystal include. 27. The apparatus according to claim 26, characterized in that the liquid crystal a nematic liquid crystal with positive dielectric properties.   28. The device according to claim 26, characterized in that that the liquid crystal a nematic liquid crystal with negative dielectric properties. 29. The device according to claim 26, characterized in that that the liquid crystal a ferrodielectric liquid crystal. 30. The device according to claim 17, characterized in that that the control device the refractive indices of the materials with variable Refractive index of the first and second diffraction gratings controls independently. 31. The device according to claim 17, characterized in that that the control device the refractive indices of the materials with variable Refractive index of the first and second diffraction gratings controls at the same time. 32. Apparatus according to claim 31, characterized in that the control device has a pair of transparent electrodes ( 3 ) which are arranged such that they receive the first and second diffraction gratings between them. 33. Device according to claim 17, characterized in that the first and second Diffraction grating near a focused position of an object image or in optically conjugated with it Positions is arranged.   34. Apparatus according to claim 33, characterized in that the first and second diffraction gratings are arranged in the vicinity of a focusing diaphragm ( 13 ). 35. Display device in a viewfinder, characterized by: a diffraction grating which is arranged in an optical path of light ( 5 ) emanating from an object to be photographed and the shape of which is essentially defined by an interface between a transparent element ( 4 ) and a material ( 1, 2 ) is determined with a variable refractive index, the diffraction grating being provided with a region which corresponds to the shape of a pattern to be displayed; and a control device for changing the refractive index of the material ( 1, 2 ) with variable refractive index, which is able to control the refractive index of the material with variable refractive index so that the light emanating from the object ( 5 ) the diffraction grating in a first state happens essentially simply and that part of the light from the object is diffracted by the diffraction grating in a second state to display the pattern. 36. Display device in a viewfinder, characterized by: a diffraction grating which is arranged in an optical path of light ( 5 ) emanating from an object to be photographed and the shape of which is essentially defined by an interface between a transparent element ( 4 ) and a material ( 1, 2 ) is determined with a variable refractive index; and a control device for changing the refractive index of the material ( 1, 2 ) with a variable refractive index, which has a transparent electrode ( 3 ) of a predetermined pattern, which predetermined pattern can substantially match the shape of a pattern to be displayed, and which is capable is to change the electrical energy applied to the transparent electrode ( 3 ) so that the light emanating from the object passes the diffraction grating in a first state essentially simply and part of the object light is diffracted by the diffraction grating in a second state to display the predetermined pattern . 37. Display device in a viewfinder, characterized by: a phase diffraction grating which is arranged in an optical path of light ( 5 ) emanating from an object to be photographed; and a control device for controlling a phase difference imparted to the object light by the diffraction grating, which is able to set the phase difference in a first state essentially 0 and to diffract part of the object light in a second state by a predetermined phase difference, the diffraction of the object light is carried out in accordance with a predefined display pattern and the predefined display pattern is superimposed on an object image, so that an observer can visually observe the predefined display pattern and the object image together. 38. viewfinder, characterized by: a focusing element ( 13 ); a display device arranged in the vicinity of the focusing element ( 13 ), which has a diffraction grating and a control device, the shape of the diffraction grating being determined by an interface between a transparent element ( 4 ) and a material ( 1, 2 ) with a variable refractive index, and the Control device is able to change the refractive index of the material ( 1, 2 ) with a variable refractive index; an optical device for guiding light emanating from an object to be photographed in the direction of an eyepiece ( 16 ) via the focusing element ( 13 ) and the display device; the control device being able to change the refractive index of the material ( 1, 2 ) with a variable refractive index such that the object light essentially passes through the diffraction grating in a first state and part of the object light from the diffraction grating in a second state is bent to produce a predetermined pattern, so that in this way an observer can simultaneously visually observe the predetermined pattern and an object image projected through the eyepiece ( 16 ) onto the focusing element ( 13 ).