JPS58107520A - Photometry device of camera - Google Patents

Abstract

PURPOSE:To obtain a photometry device which can always obtain the accurate photometric information, by performing the switching between the reference level of photometry obtained when a light shielding element is cut off and that obtained when the light shielding element is not cut off. CONSTITUTION:A pentaprism 5 is set above a focal plate 4, and an eyepiece 6 and a photometric lens 7 are provided at the right and above the prism 5 respectively. A photometric element SP is set at the right side of the lens 7, and the right face and the lower face of the prims 5 serve as a photometric mask 9 and a viewfield mask 10 respectively. An electro-optical light shielding member 11 is provided at the lower face side of the mask 10 and has contains a driving circuit 12. A 45 deg. reflector 13 set at the lower part of the plate 4 contains a half mirror at its center part. Thus a part of the luminous flux Lt of an object to be photographed that passes through a shooting lens 20 enters an upper finder optical system while another part of the flux Lt enters a lower automatic focal point AF optical system via a submirror 14 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a photometering device for a camera, in particular an electro-optical light shielding element disposed in a viewfinder optical path to regulate subject light and display information, and also to photometer the subject light. This invention relates to a camera photometry device that controls exposure.

Conventionally, cameras display information within the viewfinder field of view by placing an electro-optic light shielding element in the viewfinder optical path. This is because when an electro-optical light-shielding element is used, the amount of light received by the photometric element is different when information is displayed by the electro-optical light-shielding element and when no information is displayed. be. Therefore, in the past, the light beam was guided to the photometric element by the following method.

■ A half mirror is placed in front of the electro-optical light shielding element to guide the light beam to the photometric element.

■ A half mirror is arranged on the 45° reflection mirror, and the light is guided to the photometric element via the sub-mirror.

However, when configured in this way, the following drawbacks occur.

■ Since photometry cannot be performed after passing through an electro-optic light shielding element, there is little freedom in the placement of the photometric element, and photometry cannot be performed with a pentagonal optical system.

In particular, we introduced a focus detector into the camera, and autofocus (
For cameras that perform AF or focus display, the focusing detection element is often installed below the 45° reflection mirror, which places additional restrictions on the placement position of the photometric element.

■ The viewfinder is always dark because the light is guided to the photometric element before being guided to the finder optical system.

In addition, in order to eliminate the above-mentioned drawbacks, it is also possible to perform photometry and display in a time-sharing manner using timing signals, so that an electro-optic light-shielding element can be placed before the photometry element. However, in such a configuration, the liquid crystal (L
C) When using an electro-optical light shielding element with slow response such as an electrochromic cell (Ec), the disadvantage is that information is displayed in a blinking state, making it difficult to confirm the information. occurs.

The present invention has been made in order to eliminate the drawbacks of such conventional devices, and its purpose is to make the display by the light shielding element blink in a camera in which an electro-optical light shielding element is arranged in the front stage of the photometric element. The object of the present invention is to provide a photometry device for a camera that can always obtain accurate photometry information without being affected by the display state of a light shielding element.

Hereinafter, the present invention will be explained in detail based on the embodiment shown in the drawings.

The embodiment described here is related to a TTL type AF camera, and the first button of the release button, which is also the power switch,
In this step, photometry and distance measurement are performed, and the photographing lens is driven and controlled based on the distance measurement information to bring it into focus. The exposure information and distance measurement information at that time are displayed in the viewfinder.

First, FIGS. 1(a) and 1(b) show the inside of the finder at that time. FIG. 1(,) shows the out-of-focus state, and FIG. 1(b) shows the in-focus state. Figure 1(a) 1(b)
In the figure, 1 is a viewfinder field of view, 2 is an exposure display, 3 is a light-shielding part that indicates the distance measurement range and the in-focus state, and M is a mark that indicates the exposure display 2. In the first step of the release button (not shown), photometry and distance measurement are performed as described above, and the exposure display M is displayed in the viewfinder, and when the focus is out of focus due to distance measurement in the viewfinder field of view 1, electro-optical light is blocked. The distance measurement range is displayed by the element. Here, a positive type guest-host liquid crystal cell is used as an electro-optical light shielding element.

This guest-host liquid crystal cell (hereinafter abbreviated as GH-LC) does not use a polarizing plate, and since the liquid crystal light-shielding part 3 is not completely light-shielded (transmittance 0%), the light-shielding part 3
is in a dark or colored state, and the object can be seen through the object. When the photographic lens is driven and controlled based on the zero distance measurement information, the object becomes in focus (see Fig. 1). As shown in b), the liquid crystal cell (G)I-LC)
Figure 2 is a schematic diagram showing an embodiment of the finder optical system of a -eye reflex camera using the photometry method according to the present invention. In the figure, 4 is a focusing plate, 5 is a pentaprism above the focusing plate 4, 6 is an eyepiece on the right side of the prism 5,
7 is a photometric lens above the lens 6, SP is a photometric element on the right side of the lens 7, 9 is a photometric mask on the right surface of the prism 5, 10
11 is an electro-optical light shielding member such as a guest-host type liquid crystal, which is disposed near the bottom surface of the mask 10. 12 is a drive circuit for the light shielding member 11. In addition, in the arrangement configuration of the finder optical system described above, the focus plate 4
An electro-optical light shielding member 11 is placed between the Penck prism t5 and
Needless to say, it is also possible to arrange a focus plate t between the force ζ Penck prism 5 and the electro-optic light shielding member 11. Reference numeral 13 denotes a 45° reflection mirror below the focusing plate 4, and the central part is a half mirror, so that a part of the light flux Lt passing through the photographic lens 20 of the subject is sent to the finder optical system above, and a part is sent to the sub-mirror 14. It goes to the automatic focusing AF optical system below. 15 is a spectroscopic prism for AF below the mirror 13, and 16 is an AF sensor below the prism 15, in which a CCD (' is a charge-coupled element) sensor is used.1
7 is a circuit for AF calculation processing and control signals connected to the sensor 16; 18 is a circuit connected to the circuit 17, which receives control signals and drives and controls the driving motor 19 of the photographing lens 20;

Note that the light Ltl from the submirror 14 is divided into three parts by 15 AF spectroscopic prisms. front focus,
This is a focusing method that uses contrast detection to obtain in-focus and rear-focus signals. Here, since the AF is a known technology, details will be omitted. It goes without saying that the present invention is applicable to other focusing methods such as misalignment detection, ultrasonic detection, etc. Figure 3 is a circuit diagram showing the photometry method according to the present invention. 1(a), (b), and the embodiment of the camera using the camera shown in FIG. 2.

In the figure, OP2 to OP4 are operational amplifiers, BPI is a buffer amplifier, VR1 and VR2 are variable resistors for inputting photographic information, C1 is a storage capacitor, SP is a photoelectric conversion element for photometry, LD2 is a diode, FTI, FT2 ．． FT3 is an analog game), RGI, and RG2 are constant voltage power supplies for generating a reference voltage, and there are two types for adjusting the level of OP2. E is a battery power supply, and CKT is an exposure control circuit, which controls the shutter speed or aperture value.

IBI and IB2 are inverters, and LC is an electro-optical light-shielding element for display, which constitutes the light-shielding member 11, where display is performed by GH-LC. IDC is an alternating current pulse voltage generator for driving the LC display, and ICC is a display control circuit, which performs display by blocking light from the LC. When out of focus, the signal is "H", and when the light shielding is canceled and the display is turned off, that is, when in focus, the signal is "L". AFC is an AF arithmetic processing and control circuit 17, and transmits information on front focus, rear focus, and focus to the AF motor drive control circuit 18 of AFDC, and also transmits information on focus, - to ICC.
Conveys out-of-focus information. MO is the photographing lens drive motor 19 for AF, 0 AND 1, fan D2 is an AND gate, N0RI is a Noah gate, ORI is an OR gate, and FF 1 is a flip 70.
DTC1 and DTC2 are delay circuits for adjusting the timing by correcting the response speed of the LC.
2 is an on/off switch. this house,
8SWO is a power switch, which is closed by the first stage of a release button (not shown). SWI is a release switch that is turned on by pressing down the release button in the second step. Further, s'w2 is, for example, a timing switch that is turned off when the film is wound up and turned on when the trailing curtain running light is turned on. PUC is a single pulse generator that generates one short pulse when the SWO is turned on and the power is turned on to bring the FFI into a stable state.

Next, the constant voltage power supplies RGI and RG2f for generating the reference voltage will be explained. In the FIG. 1 (IL) (7;) state, that is, when the light is partially blocked by the LC and the display state is established (out of focus), RG 1 acts on OP2. To explain using the apex calculation value, the brightness information of the subject is BV
, let Ayo be the shooting lens open F value information, Aye be the bending information of the shooting lens, and Iv be the information on the amount of light blocked by the LC, then the output information of OP2 is ・(Bv-Avo
-Avc-Iv+ (RGI) ).

In addition, in the state shown in Fig. 1(b), that is, when partial light shielding is not performed from the LCE (in focus), OP2 is
works, so the output information of OP2 is (Btv -A
wa −AVc + (RG2)′). By establishing the relationship (RG2) = (RGI) - Iv between the constant voltage power supplies RGI and RG2 for generating the reference voltage, when measuring a diffused surface with the same brightness, the OP
0 The operation will be explained here. 0 When the camera's release button (not shown) is pressed, the power switch SWO is turned on in the first step and distance measurement and photometry are performed. , 0 when power supply to the display circuit is started, and 1 pulse is generated by the single pulse generator Puc, so the fourth
As shown in the figure, FFI via IBI and AUD 1
Since the R input of FFI becomes L level once, the Q output of FFI is held at H level. Therefore, at this time, the output of ORI becomes H level, and the output of analog game 1-FTI and AN
An H level signal is input to D2.

The distance measuring circuit also operates, and when the AFC 17 is activated and the focus is out of focus, the motor 19 for driving the photographic lens is driven in the focusing direction via the AFDC 1B (feedback control is performed). Since the information that the lens is out of focus is transmitted, the output of the IOC becomes H level. Therefore, when the output of OR1 becomes H level, the output of AND2 becomes H level, and I
An H level is input to the DC (1), the IDC is driven, an AC pulse for driving the LC is input to the LC, and a display as shown in FIG.

Further, the H output of AND2 turns on FT2 via the delay circuit of DTC1. FT3 is L to go through IB2
A level signal is input and the OFF state is 0, where DT
C1 and DTC2 are used for the purpose of synchronizing with LC because LC has a response delay. Furthermore, due to the characteristics of LC, the response speed changes depending on the temperature. Due to this temperature change, when the LC is shaded (in the display state) and when it is not shaded (in the non-display state), the O
Therefore, the DTC1 and DTC2 are configured to detect the temperature state and change the delay time based on the temperature number to achieve synchronization. In addition, RG is used for OP2 when out of focus.
A voltage of I is applied. Therefore, the output level of OF2 is F
Determined by LGl.

On the other hand, the light from the object inputted through the state of FIG.
The signal is logarithmically compressed and generated at the output of OF2, and is stored in the capacitor CIL via the analog gate FTa which is in the ON state. Since this stored information has the RGI voltage applied to 10P2, the output level is determined by RGI. (As mentioned above, due to the relationship between RG 1 and RG 2,
When photometrically measuring the same luminance diffusion surface, the output is at the same level even in the states shown in Figure 1 (a) and Figure 1 (b)) 0 Therefore, output level information is omitted and explained using Apex calculation values. Then it comes like greed.

The stored information includes subject brightness information By, aperture f-number information Avo of the attached lens, aperture bending information Av of the lens, etc.
The calculated information (By −Ayo −Aye) of c is stored. These information (Bv-Avo-A
Vc) via buffer amplifier BPI, resistor R4,
Enter into O20.

Also, setting the variable resistor VRI! From this, for example, Av.

Aye information is input and outputted via operational amplifier OP3.
The input of 00P4, which is input to F2, is input with the photographing information set in variable resistor VR2, such as shutter time information Tv and film sensitivity information Sv, and the output of OF2 is (By -Ayo -Aye) +Aye.
+ Ayo + Sy −Ty = Ay is obtained,
Figure 1(a).

It is displayed in the viewfinder by the exposure display meter M in (b), and is also input to the control circuit CRT.

- On the other hand, based on the operation of the ranging circuit, AFC17, AFD
At C18, the photographing lens is stopped at the in-focus position under the drive control of the drive motor 19.

At this time, since a focusing signal is input from the AFC 17 to the ICCG, the output of the ICC becomes L level. Therefore, the output of AND2 also becomes L level, and the input of IDC becomes L level, so the output of the AC pulse is stopped and the light shielding by LC is released. Therefore, the display in the viewfinder visual field 1 disappears, and the in-focus state can be visually confirmed. At this time, the input of FT2 is set to L level via the DTCI delay circuit, so FT2 is turned off. Further, since FT3 is connected to IB2, an H level signal is input thereto, and the FT3 is turned on, and the voltage level of OF2 is determined by RG2. Here, as mentioned above, if you switch between LC, FT2, and FT3, DTC1
, DTC'2.

As described above, the output of OF2 at this time is such that the light shielding part of the LC disappears and the amount of received light increases, but by changing the reference voltage of OF2 from RG1 to RG2, the output level of OF2 becomes the same. The following is the same as the situation in Figure 1 (,),
・Exposure calculation is performed.

Φ Next, by pressing the release button the second time, as shown in Fig. 4,
When SWl is turned on, the S input of FF1 becomes L level. At this time, since A2 remains OFF, the Q output of FFI is latched at L level. Therefore, the output of OR1 goes to the L level, FTl turns off, and the photometric information (BV -Avo -Aye
) is stored in memory. Also, at this time, the output of AND2 is held at L level by ICC, so TF
2. TF3 will never change. Photometric information (By
-Ays-, ^1we) is the buffer amplifier BP1
Ayo, AV by setting variable resistor VRI through %
OF2 information is inputted and passed through operational amplifier CP3.
is input. The input of the operational amplifier OP4 is inputted with the shooting information set by the variable resistor VR2f, such as shutter information TV and film sensitivity information, which is calculated by OF2, and as its output information (Bye
-Ayo -AQC) 10Aye +Ayo + Sy
-Ty = Av is obtained. Based on this output information Av, the control circuit CRT is controlled to achieve proper exposure.

A series of exposure controls are performed by C and KT, and when the shutter opening and closing operations are completed, SW2 is turned on.

Therefore, when the R input of FFI is at L level and SWI is OFF, its S input is at H level, so the Q output is at H level and the output of ORI is at H level. During this time, distance measurement and photometry as described above will be restarted. Also, when S%V1 is ON, the S input of FFI becomes L level, and FF1
is undefined, but because the output of ORI becomes H level due to NoR1, the same result as described above is obtained.

As described above, the present invention switches the photometric reference level according to the display state of information by the electro-optic light shielding element, so even if such information is displayed within the field of view of the viewfinder, accurate photometry can always be achieved. Information can be obtained and the exposure of the camera can be set appropriately. Further, according to the present invention, there is no need to perform the display in a blinking state, and furthermore, the photometric element can be placed at any position.

In this embodiment, a case has been described in which the focus of the TTL-AF camera is displayed using an electro-optic light shielding element. Of course, this is also a good thing.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are explanatory diagrams illustrating one embodiment of the present invention, respectively. The figure is an example of the same as above. Rough layout
Figure 3 is a block circuit diagram of the same embodiment as above; Figure 4 is a block diagram of the same embodiment.
The figure is a time chart explaining FIG. 11. LC: light shielding element, light shielding member 1: finder field of view 3: light shielding part for display SP: photometric element RGI, RG2: constant voltage power supply F'T2 at photometric reference level
．． FT3: Analog gate patent applicant Canon Corporation Figure 1 (a) 11111 Figure (b)

Claims (1)

[Scope of Claims] A camera that displays information by regulating subject light using an electro-optical light shielding element disposed in a finder optical path, and controls exposure by metering the subject light, comprising: 1. A photometric device for a camera, characterized in that a photometric reference level when an element is in a light-shielding state and a photometric reference level when the light-shielding element is in a non-light-shielding state are switched.