JPH0391730A - Display device in camera finder - Google Patents

Abstract

PURPOSE:To prevent the liquid crystal material of a liquid crystal display plate from being decomposed by ultraviolet rays arranging an optical element, which is formed by material added with ultraviolet absorber on an optical path from an objective lens to the liquid crystal display element. CONSTITUTION:Incident light passing through a photographing lens 1 is reflected by a quick returning mirrow 2 and forms an object image on a focusing plate 3. The light passing through the focusing plate 3 transmits theough an LCD 4, which displays a pattern that displays a range-finding area and a photometry area, passes through a pentaprism 5 and is made incidence on an eyepiece. Since most of the ultraviolet rays are made incident on the photographing lens 1, the influence of the ultraviolet rays on the liquid crystal display plate 3 can be effectively prevented by giving ultraviolet absorbing performance to the focusing plate 3. The prevention of the influence of the ultraviolet rays made incident on the eyepiece 6 is attained by constituting the eyepiece 6 by PMMA resin which has the ultraviolet absorber added similarly as the focus plate 3 and polycarbonate resin added with the ultraviolet absorber.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a camera fine display device that allows the background to be seen through and also allows a display pattern to be displayed superimposed on the background. [Prior Art] As shown in Fig. 6, the display section in the viewfinder of a camera displays a distance measurement area A, a photometry area B, and off-screen information C. A liquid crystal display element is placed inside the finder optical system. By the way, when liquid crystal materials are exposed to sunlight or other light sources for a long period of time, they are degraded by ultraviolet rays, resulting in a decrease in contrast and a decrease in response speed.
In addition, guest-host type liquid crystals do not use polarizing plates, so the finder image can be brightened, but the pigment used as a guest is also broken down by ultraviolet rays, which further reduces the contrast during display. . Therefore, when placing a liquid crystal display element with such properties in a camera's viewfinder optical system, the glass substrate of the liquid crystal display element must be protected from ultraviolet rays to prevent deterioration due to light incident from the objective lens side and eyepiece side. A UV cut filter was installed. [Problems to be Solved by the Invention] In order to display the distance measurement area etc. in the finder, a liquid crystal display element is provided near the focus plate where the subject image is formed.
The object image formed on the focus plate by the eyepiece and the distance measurement area mark displayed on the liquid crystal display element are observed simultaneously. Therefore, if scratches or bubbles are created in the process of attaching the LIV cut filter film to the liquid crystal display element, these scratches or bubbles will be magnified and easily observed by the eyepiece. Further, since the UV cut filter film has a thickness of 0.1 to 0.3 mm, the thickness of the liquid crystal display element becomes thicker, which becomes an obstacle when designing a smaller camera body.

[Means to solve the problem]

This invention solves the above-mentioned problems, and is provided in a camera finder display device in which a liquid crystal display element is arranged on the optical path of a finder optical system including an objective lens and an eyepiece. It is characterized by an optical element made of a material to which an ultraviolet absorber is added. Furthermore, an optical element made of a material to which an ultraviolet absorber is added may be disposed on the optical path from the liquid crystal display element to the eyepiece. A guest-host type liquid crystal material can be used for the liquid crystal display element. [Function] Optical elements placed on the optical path from the objective lens to the liquid crystal display panel, such as the focus plate, are made of a material added with an ultraviolet absorber, thereby blocking ultraviolet rays contained in the incident light, and The liquid crystal material of the display board is prevented from being decomposed by ultraviolet rays, and since no UV filter is attached to the liquid crystal display board, there is no risk of scratches or bubbles being attached to the liquid crystal display board. In addition, when optical elements disposed on the optical path from the liquid crystal display element to the eyepiece, such as the eyepiece element, are also made of a material containing an ultraviolet absorber, the liquid crystal material is damaged by the ultraviolet rays incident from the eyepiece side. It can prevent it from being decomposed. [Example 1 Examples of the present invention will be described below. FIG. 1 shows the optical system of a single-lens reflex camera to which the in-finder display device of the present invention is applied. In the figure, ■ is a photographing lens, 2 is a quick return mirror whose central portion is a semi-transparent mirror, and 3 is a focusing plate, which is provided at a position conjugate with the film plane F. 4 is a guest-host type cholesteric-nematic phase transition type liquid crystal display (LCD) having negative dielectric anisotropy, which will be described in detail later; 5
is a pentaprism, and 6 is an eyepiece. 7 is a mirror provided at the center of the back of the quick return mirror 2;
8 is an automatic focus detection (AF) light receiving element. Also, 9
1 is a lens for measuring subject brightness, and 10 is a light receiving element for photometry. 11 is a light emitting element, and 12 is a TN type liquid crystal display (LCD) that displays off-screen information such as shutter speed and aperture value.
, 13 is a light guide prism that guides the display contents of the LCD 12 into the finder via a pentaprism. The incident light that has passed through the photographic lens 1 is reflected by the quick return mirror 2 and forms a subject image on the focus plate 3. The light that has passed through the focusing plate 3 is transmitted through the LCD 4 that displays a pattern indicating the distance measurement area and the photometry area, and then is transmitted through the pentaprism 5.
It enters the eyepiece lens 6 through the . In addition, the LCD 12 that displays off-screen information is illuminated by a light emitting element 1l, and the L
The image of the CD 12 enters the eyepiece 6 via the light guiding prism l3 and the Vanta prism 5. Therefore, the distance measurement area pattern and photometry area pattern are superimposed on the subject image on the viewfinder display, and off-screen information is displayed outside the viewfinder frame. FIG. 2 shows the arrangement of display patterns on the finder display device. In the figure, 20 is a finder frame in which a subject image is displayed, and 21 is off-screen information displayed outside the finder frame 20, on which the image of the LCD 12 is projected. Areas 23, 24, and 25 indicated by dotted lines indicate the range of the distance area of the object, and bracket patterns 26, 27 are displayed on the LCD 4 to inform the photographer of this distance measurement area.
．． 28.29 are provided. Central ranging area 23
When selected, bracket patterns 27 and 28 are displayed, and bracket patterns 26 and 29 are erased, and when ranging areas 24 and 23.25 are selected at the same time, bracket patterns 26 and 29 are displayed, and bracket patterns 26 and 29 are erased. 27 and 28 are driven by a drive circuit described later so that they are erased. Areas 31, 32, and 33 indicated by dotted lines indicate the range of the photometry area of the subject, and in order to notify the photographer of this photometry area, the LCD 4 is provided with circular patterns 34, 35 and rectangular patterns 36. . The device is driven by a drive circuit, which will be described later, so that a corresponding pattern is displayed according to the selected photometry mode, and other patterns are erased. In the above configuration, the focusing plate 3 is made of a polymethyl methacrylate (PMMA) resin added with an ultraviolet absorber selected from salicylate, benzophenone, penzotriazole, and cyanoacrylate materials. Appropriate. Since most of the ultraviolet rays enter through the photographic lens l, by imparting ultraviolet absorbing performance to the focusing plate 3 as described above,
Although the influence of ultraviolet rays on the liquid crystal display panel 3 can be effectively prevented, in order to prevent the influence of ultraviolet rays that enter through the eyepiece lens 6, the eyepiece lens 6 should be coated with an ultraviolet absorber in the same way as the focusing plate 3 described above. This can be achieved by using PMMA resin added or polycarbonate resin added with an ultraviolet absorber. FIG. 3 is a partially enlarged cross-sectional view of a cholesteric-nematic phase transition type liquid crystal display (LCD) 4. In the figure, 4a and 4b are transparent glass substrates,
4c and 4d are transparent electrodes provided on glass substrates 4a and 4b;
4e is a dichroic dye orientation factor (dye molecule) with light absorption anisotropy; 4f is a cholesteric dye with negative dielectric anisotropy;
The orientation factors (liquid crystal molecules) of nematic phase transition type liquid crystals are shown. As shown in the figure, when no voltage is applied to the electrode 4c, the alignment factor of the liquid crystal is aligned perpendicular to the electrode surface (homeotropic alignment), so it is transparent and nothing is displayed. Here, in order to strengthen the homeotropic alignment, a surfactant or the like is added to the liquid, so the transparency in this state is high. When a voltage is applied to the electrode 4C, the alignment factor turns into a cholesteric phase, which is oriented in a spiral around an axis perpendicular to the electrode surface as a property of cholesteric liquid crystal. When the orientation factor 4f of the host liquid crystal becomes a cholesteric phase, the dichroic dye added as a guest and having light absorption anisotropy has its orientation factor (dye molecule) 4e also oriented in a helical shape like the host liquid crystal molecule. All dyes are oriented in all directions in a plane parallel to the electrode plane. Since the dye having positive light absorption anisotropy has the property of absorbing light in the same vibration direction as the orientation direction of the orientation factor 4e, it absorbs light in all vibration directions and blocks the light. This increases the contrast of the display section. In this embodiment, since the display section is positive (becomes opaque when the voltage is turned on), there is no need for transparent electrodes on the entire surface, and it is sufficient to provide electrodes only on the display pattern section, so that no leader lines are displayed. FIG. S is a block diagram of a driving circuit for a liquid crystal display panel. In the figure, the control circuit 43 is connected to the automatic focus detection light receiving element 8.
A distance signal obtained by processing the detection signal in the distance measurement circuit 41 and a subject brightness signal obtained by processing the detection signal of the photometry light receiving element 10 in the photometry circuit 42 are input, and a lens (not shown) is inputted.
It outputs control signals to drive mechanisms such as the diaphragm and shutter, and also outputs display signals such as distance measurement area, photometry area, shutter speed, aperture value, etc. to the liquid crystal display board drive circuit 44. The liquid crystal display panel driving circuit 44 includes a static driving section 44a and a 1/4 duty dynamic driving section 44b. The static drive unit 44a drives the LCD 4 that displays distance measurement area patterns, photometry area patterns, etc., and the dynamic drive unit 44b drives the LCD 12 that displays off-screen information such as shutter speed and aperture. When dynamically driving an LCD, the higher the number of time divisions (lower the duty ratio), the more display segments can be driven with fewer terminals, but low voltage is also applied to segments that are not displaying. There is. The higher the number of time divisions, the smaller the difference between the voltage applied when displaying and the voltage applied when not displaying. Therefore, to drive an LCD with dynamic drive with a high number of time divisions, the display can be turned ON/OFF reliably even if the difference between the voltage applied when displaying and the voltage applied when not displaying is small. It is necessary to use an LCD, making it difficult to create an LCD. In addition, generally TN
It is relatively easy to perform dynamic driving with a high number of time divisions in a type LCD, but it is difficult to perform dynamic driving in a guest-host type LCD. On the other hand, in the case of static driving, no voltage is applied to segments that are not displaying, making it easier to create an LCD. In the case of the display element of the embodiment of the present invention, the LCD l2 that displays off-screen information such as shutter speed and aperture requires a large number of segments to display numbers, whereas the screen for distance measurement area, photometry area, etc. The LCD 4 that displays internal information has fewer segments to display. Therefore, although the LCD 4 for displaying on-screen information is configured with a guest-host type LCD and is driven statically, the LCD 12 for displaying off-screen information
It is composed of a TN type LCD and is dynamically driven. Note that even in a guest-host type LCD, if the number of time divisions is low (the duty ratio is large, for example, 1/2), dynamic driving is also possible, and instead of the static drive unit 44a, 1/2
It can also be a duty dynamic drive. FIG. 5 shows a second embodiment of the present invention, which is an in-finder display device for a compact camera having a finder optical system separate from a photographic lens. In the figure, 51 is an objective lens, 52, 53, 54.5
Reference numeral 5 denotes a set of four boromirrors, which converts the fil image formed by the objective lens 51 into an erect image. 56
57 is an eyepiece lens, and 57 is a guest-host type liquid crystal display (LCD) disposed near the image forming position of the objective lens 51, which has the same configuration as that shown in the first embodiment and operates in the same manner. The distance measurement area pattern and photometry area pattern are displayed in the viewfinder. 58 is a condenser lens placed close to the liquid crystal display panel 57. Objective lens 51. Eyepiece lens 56, condenser lens 5
8 was made of a material in which a UV absorber selected from salicylate-based, benzophenone-based, penzotriazole-based, and cyanoacrylate-based materials was added to polyethyl methacrylate (PMMA) resin, polycarbonate (PC) resin, etc. things are appropriate. Furthermore, it is not necessary that all of the objective lens, eyepiece lens, and condenser lens be formed of a material containing an ultraviolet absorber, and only the most effective elements may be formed of the above-mentioned material. [Effects of the Invention] As explained above, according to the present invention, an appropriate optical element constituting the finder optical system absorbs ultraviolet rays.
Since it functions as a V-cut filter, there is no need to attach a UV-cut filter film to the surface of the liquid crystal display element, and there is no fear of scratches or bubbles, and the thickness of the liquid crystal display panel can be reduced.

[Brief explanation of drawings]

Fig. 1 is a first embodiment in which the in-finder display device of the present invention is applied, and is a diagram showing the optical system of an L-lens reflex camera, and Fig. 2 is a diagram showing the arrangement of display patterns of the in-finder display device in the first embodiment. FIG. 3 is a partially enlarged sectional view of a liquid crystal display board, FIG. 4 is a block diagram of a drive circuit for the liquid crystal display board, and FIG. 5 is a second embodiment to which the finder display device of the present invention is applied. FIG. 6 is a perspective view showing a real-image finder optical system for a compact camera, and FIG. 6 is an explanatory diagram of a display example of a conventional finder display device. 1,51: Objective lens, 3: Focus plate, 4.57: Liquid crystal display board, 6.56: Eyepiece lens・52,
53, 54, 55: Boro mirror, 58: Condenser lens.

Claims (3)

[Claims] (1) In a camera finder display device in which a liquid crystal display element is arranged on the optical path of the finder optical system including an objective lens and an eyepiece, an ultraviolet absorber is added to the optical path from the objective lens to the liquid crystal display element. A display device in a finder of a camera, characterized in that an optical system element made of a material is arranged. (2) In the camera finder display device according to claim 1, an optical element made of a material added with an ultraviolet absorber is further disposed on the optical path from the liquid crystal display element to the eyepiece. A distinctive feature is the display device in the camera's viewfinder. (3) The camera finder display device according to claim 1 or 2, wherein the liquid crystal display element is made of a guest-host type liquid crystal material.