JPS6215806Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a display illumination device having a display device that allows display light to enter a pentaprism of a camera.

<Prior Art> Various types of photographing information are displayed in cameras, such as shutter speed, aperture, photographing distance, depth of field, battery exhaustion warning, overexposure and underexposure warning, camera shake warning, and the like.

In recent years, display devices using liquid crystal cells have been proposed as these display devices. Liquid crystal cells have the advantage of having no mechanically moving parts and are less prone to failure, but since they do not themselves emit light, it is difficult to see the display in a dark place. Therefore, for cameras using conventional light-receiving display devices such as liquid light cells, LEDs, lamps, etc. are turned on as self-luminous light sources during preparation for shooting, so that the display is always illuminated, even in dark places. Proposals that enable visual recognition are known.

However, in the above-mentioned improved proposal, the self-luminous light source is turned on each time a photograph is taken, which consumes a lot of battery power, and when the subject brightness is high and the viewfinder is bright, the artificial self-luminous light source alone cannot be used. There is a problem that the display is dark and difficult to see.

Regarding the latter of the above problems, the present applicant proposed in Japanese Patent Laid-Open No. 51-37228 that as the subject brightness increases, the amount of light emitted is increased accordingly. Even with this method, there is a problem of battery consumption, and it is basically impossible to incorporate a self-luminous light source with the same level of brightness as outside light into the camera, so further improvements are desired.

<Purpose of the invention> The present invention was made to solve the above-mentioned conventional problems, and consists of placing a transmissive display for displaying photographic information near the pentaprism, and directing the display light into the pentaprism. In devices that emit light, the transmitted light for the display light of the display device is composed of two lines: external light and lighting light from a self-luminous light source, and when the external light is bright, only the external light is used as the transmitted light, and the display light is displayed in the viewfinder. It is possible to obtain the display light that is comparable to the brightness of the subject without draining power sources such as batteries, and on the other hand, when the outside light is dark, the self-luminous light source is automatically turned on and this lighting light is used as the display light. The self-luminous light source itself can be used as transmitted light to obtain display light that is visible under any external light conditions, and the self-luminous light source itself can block the external light and prevent the display light from being shaded. The light source is placed at a position different from the external light flux, and is guided to the display by a light guiding member, and furthermore, the brightness and darkness of the external light is determined by a photometric circuit originally configured in the camera. It is an object of the present invention to provide a display illumination device for a camera which has various advantages such as not having to configure a dedicated light receiving element because the photometry is performed at the detected photometric level.

<Example> FIG. 1 shows the configuration of a field effect type liquid crystal cell used in this example.

In the figure, 1 is a first polarizing plate, 2 is a first substrate, 3 is a resistance layer formed on the substrate 2, 4 is a space filled with a nematic liquid crystal exhibiting an electric field effect, and 6 is a second polarizing plate.
5 is a conductive layer or a resistive layer formed on the substrate 6, and 7 is a second polarizing plate.

The arrows on the polarizing plate 1 indicate the polarization direction of the polarizing plate, the dotted arrows on the resistive layer 3 indicate the orientation direction of liquid crystal molecules on the surface of the resistive layer, and the arrows on the resistive layer 5 indicate the direction of alignment of the liquid crystal molecules on the resistive layer 3. This indicates the alignment direction of the liquid crystal molecules on the surface, and the liquid crystal molecules filled between the planes form a gradually twisted arrangement within the angle formed by the two dotted arrows. The arrow on the polarizing plate 7 represents the polarization direction of the polarizing plate. This polarizing plate 7 detects the light emitted from the liquid crystal cell.

In FIG. 1, the orientation of the liquid crystal molecules is twisted by 90 degrees. Incident light from above in Figure 1
_I0 aligns the polarization plane according to the polarization plane of the polarizing plate 1, and rotates the polarization plane by an angle corresponding to the twisted orientation of the liquid crystal molecules when passing through the liquid crystal layer between the resistive layer 3 and the layer 5. The light is incident on the polarizing plate 7 of No. 2.

When the polarization plane at this moment and the polarization plane of the polarizing plate form an angle of 90 degrees, the incident light I ₀ is blocked here, and the observer at the bottom of the paper can perceive it in the dark.

When an electric field greater than a certain value is applied to a liquid crystal cell,
The liquid crystal molecules are aligned with their long axes perpendicular to the substrate surface, and at this time, since the liquid crystal is isotropic with respect to the incident light I ₀ , no rotation of the polarization plane of the incident light occurs. Therefore, if the polarization directions of the two polarizing plates are parallel, light will be transmitted when an electric field is applied, and it can be identified as a bright state compared to the above-mentioned state when no application is applied. Figure 2 shows this in terms of the relationship between voltage and amount of transmitted light.
Vth is the threshold. The negative/positive display is reversed depending on whether the polarization directions of the two polarizing plates are parallel or perpendicular.

A field-effect liquid crystal cell as described above requires a polarizing plate for both transmission type and inversion type display methods. However, polarizing plates greatly attenuate the amount of light. Therefore, when a liquid crystal cell display is incorporated into a camera that is normally used indoors or in a dark place, it may be difficult to read the display using only external light. Of course, not only field effect type liquid crystal cells but also dynamic scattering type liquid crystal cells are difficult to see in a dark place.

FIG. 3 is a circuit diagram of one embodiment. In the same figure, 1
1 is a power battery, 13 is a light receiving element using OdS,
Perform TTL open metering. 12 is a variable resistor for voltage division.
Reference numeral 14 denotes an operational amplifier, which applies unloaded feedback between its inverting input terminal and output terminal to form a buffer circuit. Reference numeral 15 denotes a lamp provided near the display means as a light emitting means. 16 is resistance,
Limiting the current flowing through the lamp. A transistor 17 is connected in series to the lamp 15 and constitutes a switching means. 25 is an operational amplifier, and resistor 19 and resistor 20 form a non-inverting amplifier. A transistor 18 is connected in parallel to the non-inverting input terminal of the operational amplifier 25.
A transformer 21 is connected to the output terminal of the operational amplifier 25. The circuit surrounded by the dotted line 23 is a DC-AC inverter based on Royer's circuit. 22 is a liquid crystal cell disposed near the pentaprism of the viewfinder optical system, which displays using external light or the lighting light of the lamp 15, in which the output voltage of the inverter 22 is applied to the resistor electrode between AB. At the same time, the output of the transformer 21 is applied to uniform electrodes facing each other across the liquid crystal, thereby forming a display means driven by the liquid crystal. Reference numeral 26 denotes open F value transmitting means that interlocks the variable resistor 12. In other words, the brightness level of the liquid crystal cell 22 when the lamp 15 is turned on changes depending on the aperture F value of the photographing lens, and this is corrected.

The circuit shown in FIG. 3 operates as follows.
A voltage corresponding to the amount of light received by the CdS 13 is generated at the output terminal of the arithmetic circuit 14, and an output voltage amplified by the ratio of resistors 20 and 19 is generated at the output terminal of the arithmetic circuit 25. On the other hand, another trap 24 is taken out from the output terminal of the DC-AC inverter 23, and the transistor 18 is turned on and off by the output voltage.
An AC voltage synchronized with the AC output voltage of OdS 13 is generated. This output voltage is applied to the C electrode of liquid crystal cell 22, and photometric information is displayed by said cell 22. When the brightness of the subject decreases and the resistance value of OdS 13 increases, the output voltage of operational amplifier 14 increases, and when this output voltage reaches a certain level or higher, transistor 17 turns on and lamp 15 lights up. Resistor 27 is adjusted so that this lighting start level coincides with the moment when it becomes difficult to see the display in the viewfinder due to external light.

Since it operates as described above, according to this embodiment, unlike a display device in which the information display in the viewfinder also becomes dark when the subject (i.e., outside light) becomes dark, the information display only becomes dark when the subject (i.e., outside light) becomes dark. The lamp automatically turns on to make the display easier to read, and the lamp consumes less power.

FIG. 4 is a perspective view showing an embodiment in which a liquid crystal cell and a lamp are installed in a single-lens reflex camera. In the figure, 31 is a pentaprism. 32 is a condenser lens. 33 is a focusing plate. 34 is a reflecting mirror that performs a quick return motion. A prism 35 guides information incident from a surface 36 into the finder.
22 is the liquid crystal cell. 15 is the lamp. 37 is a scattering plate that uniformizes the light from the lamp and connects it to the liquid crystal cell 22.
to illuminate. A driving circuit 40 drives the liquid crystal cell 22 and the lamp 15. Reference numeral 41 is a lighting window, and when the camera is in a bright atmosphere, external light entering from this window illuminates the liquid crystal cell 22.

As is clear from the figure, the characteristic feature here is that the lamp 15 is arranged at the scattering plate 37 of the external light beam entering from the lighting window 41 and the liquid crystal cell 22.
It is located at a position shifted downward in the figure from the optical axis toward. Therefore, when the lamp 15 is not lit and transmitted light is generated only by external light entering through the lighting window 41, the display light on the liquid crystal cell 22 is reduced because the lamp 15 does not block the external light. No shadow problem occurs. Furthermore, even if the lamp 15 is shifted downward in the figure as described above, the scattering plate 37
Since the lighting light is uniformly transmitted through the liquid crystal cell 22, the visibility of the display is not adversely affected.

FIG. 5 shows the pentaprism 31 shown in FIG.
This is a view of the prism 35 from the rear, and the information introduced from the surface 36 is reflected like an arrow and displayed in the viewfinder.

FIG. 6 is a perspective view showing another arrangement example of a liquid crystal cell and a lamp. Here, triangular prism 3
8 is provided, and a lamp 15 is placed at a shifted position next to it. Further, the upper surface 39 of the triangular prism 38 also serves as a lighting window to introduce outside light. Incidentally, the lighting light of the lamp 15 is reflected by the prism 38 and guided in the direction of the liquid crystal cell 22 as transmitted light.

In the embodiments shown in FIGS. 4 and 6 described above, the prism 35 guides the display light (transmitted light) that has passed through the liquid crystal cell 22 to a direction outside the field of view of the object in the viewfinder field of view by reflection at the pentaprism 31. A reflective member is configured to determine the direction of the display light, and specifically, a reflective surface is set so as to guide the display light into the pentaprism 31 by reflecting it twice. Yes (see Figure 5).

<Effects of the Invention> As explained above, the present invention has a transmissive display for displaying photographic information in the vicinity of the pentaprism, and the display light enters the pentaprism. The transmitted light for the display light of the device is composed of two lines: external light and the lighting light of the self-luminous light source, and when the external light is bright, only the external light is used as the transmitted light,
It is possible to obtain the display light that is comparable to the brightness of the subject in the viewfinder without draining power sources such as batteries, and on the other hand, when the outside light is dark, the self-luminous light source is automatically turned on and this lighting light is is used as transmitted light for the display light, it is possible to obtain display light that is visible under any external light condition, and the self-luminous light source itself blocks the external light and does not cause shading of the display light. The light source is placed at a position different from the external light beam so that it is guided to the display by a light guiding member, and furthermore, the brightness and darkness of the external light can be determined using the photometry originally configured in the camera. Since the measurement is performed using the photometric level detected by the circuit, there is no need to configure a dedicated light receiving element.
The self-luminous light source should be turned on based on the external light of the camera, but the brightness of the external light is determined by detecting the brightness level of the subject light that has passed through the photographic lens using the light receiving element. Shooting lens aperture F
In order to prevent the lighting start level of the light source from greatly varying due to the difference in values, in the present invention, the brightness level is corrected using the aperture F value information of the photographing lens. As a result, even if there is little subject light incident on the light-receiving element in the case of a particularly dark photographic lens, unnecessary lighting of the self-luminous light source can be prevented when the outside light is brighter than a certain level, reducing current consumption. Provided is a display illumination device for a camera that has various advantages such as great effects.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an example of a liquid crystal cell. FIG. 2 is a graph showing the relationship between voltage and amount of transmitted light of the liquid crystal cell shown in FIG. FIG. 3 is a circuit diagram of an embodiment of the present invention. FIG. 4 is a perspective view showing the arrangement of a liquid crystal cell and a lamp. FIG. 5 is a perspective view showing the optical path of information. FIG. 6 is a perspective view showing another arrangement of the liquid crystal cell and the lamp. 13...CdS light receiving element, 15...lamp, 22
...Liquid crystal cell, 31...Pentaprism, 35,
38... Prism, 37... Scattering plate, 40... Drive circuit, 41... Lighting window.

Claims (1)

[Scope of utility model registration request] A transmissive display consisting of a light-receiving electro-optical element such as a transmissive liquid crystal display is placed close to the pentaprism of the viewfinder optical system in order to enter display light for photographic information into the pentaprism. In a camera having a photometric circuit including a light receiving element for detecting the brightness level of a subject transmitted through a lens, there is provided a light receiving section for guiding external light to the display, and a light receiving section for guiding external light to the display device. It is determined that the output level from the light-receiving element in the photometric circuit and the self-luminous light source disposed at a position shifted from the light flux line directed toward the display device has become lower than a predetermined luminance level, and the self-luminous light source is a drive circuit that generates a lighting output; a brightness level correction circuit that corrects the predetermined brightness level as a reference for generating the lighting output in the drive circuit based on aperture F value information of a photographing lens; and a light guiding member disposed on the light incident surface of the display for guiding the emitted light to the display, and when the external light is at a predetermined brightness level or higher, The display light enters the pentaprism using only the light transmitted through the display, and when the external light falls below the predetermined brightness, the self-luminous light source is turned on to emit light from the display. A display illumination device for a camera, characterized in that display light enters a pentaprism using transmitted light.