JP2000356737A - Focus detector for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect focus extending over a wider visual field by detecting phase difference obtained by reflecting subject luminous flux transmitted through a photographing lens by an optical path switching element arranged in front of an equivalent surface to a film and transmitting it through a main mirror and guiding it to a focus detection optical system. SOLUTION: This focus detector for camera is constituted so that one part of the subject luminous flux transmitted through the photographing lens 11 is reflected in a different direction from a film surface by the main mirror 12. The luminous flux reflected by the mirror 12 is further reflected by the optical path switching element 16 positioned in front of a focusing plate 17 being the surface equivalent to the film surface. Then, the luminous flux reflected by the element 16 is transmitted through the mirror 12 and received by the focus detection optical system 21. Thus, the focus is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device used for an optical device such as a camera, and more particularly, to a focus detection device.
The present invention relates to a focus detection device for a camera that performs focus detection using an optical element that can electrically switch optical paths.

[0002]

2. Description of the Related Art Conventionally, many focus detecting devices have been proposed. For example, JP-A-9-184965 discloses a camera that performs focus detection by a TTL phase difference detection method.

In the camera described in the above publication, an elliptical mirror is used as a sub-mirror for guiding a light beam transmitted through a main mirror to a focus detection unit. Thus, a wide range of light beams is guided to the focus detection optical system, and focus detection can be performed over a wide range.

[0004]

However, in order to perform focus detection over a wider range, it is necessary to increase the area of the sub-mirror. However, there is a problem that, when the sub-mirror is enlarged, it hits a shutter or the like arranged in the vicinity, so that there is a limit to widening the field of view.

Accordingly, the present invention has been made in view of the above situation, and an object of the present invention is to provide a focus detection device for a camera capable of detecting a focus in a wider field of view.

[0006]

That is, the present invention provides a first optical element which reflects a part of a subject light beam passing through a photographic lens in a direction different from the film surface, and further comprising a first optical element in front of a surface equivalent to the film surface. A second optical element that is located and further reflects the light beam reflected by the first optical element; and a focus detection unit that receives the light beam reflected by the second optical element and performs focus detection. It is characterized by.

In the camera focus detection device according to the present invention, a part of the subject light beam passing through the taking lens is reflected by the first optical element in a direction different from the film surface. The light beam reflected by the first optical element is further reflected by the second optical element positioned in front of a surface equivalent to the film surface. Then, the light beam reflected by the second optical element is received by the focus detection means, and focus detection is performed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described.

FIG. 1 shows an optical path diagram of an optical apparatus to which a camera focus detection device according to the present invention is applied.

In FIG. 1, a photographing light beam from a subject incident from the front of the photographing lens 11 is
Is guided to the main mirror 12 disposed on the optical axis O of the optical disk.
The main mirror 12 is constituted by a half mirror that transmits a part of the light beam. The photographing light beam transmitted through the main mirror 12 is imaged on a film 14 as an imaging surface via a shutter 13.

On the other hand, the photographing light flux reflected upward by the main mirror 12 in FIG. 1 is placed on the optical axis of the photographing lens 11 via an optical path switching element 16, a focus plate 17, and a pentaprism 18, and an eyepiece 19. Led to.

The optical path switching element 16 is disposed in front of the focus plate 17 and has a function of switching an optical path, so that the reflectance and the transmittance can be electrically controlled. Also,
On the focus plate 17, the subject image by the photographing lens 11 is
An image is formed via the main mirror 12 and the optical path switching element 16. Thereby, when observing the subject, the photographer can move the focus plate 17 through the pentaprism 18 and the eyepiece 19.
The upper subject image can be observed.

At the time of focus detection, the light path switching element 16 is set to a predetermined reflectance and transmittance, and the light beam passing through the photographing lens 11 is reflected by the main mirror 12 and then reflected by the light path switching element 16 in FIG. Is reflected downward at The reflected light flux is further transmitted through the main mirror 12 and guided to the focus detection optical system 21 at the bottom of the mirror box.

The focus detecting optical system 21 includes a pupil mask 22 and
And a re-imaging lens 23 for re-imaging the focus detection light beam on the area AF sensor 24.

When a subject image is photographed, the main mirror 12 is retracted to the position shown by the broken line in FIG. 1, the shutter 13 is opened, and the photographing light beam is guided to the film 14 to be exposed. I have.

The optical path switching element 16 is an element capable of adjusting the reflectance and transmittance of light by an electric signal. Such an element is described in "NATURE VOL.392 2 AP".
RIL 1998 ".

The optical path switching element 16 is capable of adjusting the rate at which light is electrically transmitted and the rate at which light is reflected on one of the surfaces formed of transparent resin. Further, the optical path switching element 16 is in a state of reflecting light when no voltage is applied, and can change light transmittance according to the applied voltage when voltage is applied.

Next, the focus detecting optical system will be described with reference to FIG.

FIG. 2 is a diagram showing the configuration of the focus detection optical system 21. The focus detection optical system 21 employs a known re-imaging phase difference detection method.

In FIG. 2, an exit pupil 11a of the photographing lens is arranged in front of the main mirror 12 on the optical axis of the photographing lens. Further, between the main mirror 12 and the area AF sensor 24, a pupil mask 22 having openings 22a and 22b arranged substantially symmetrically with respect to the optical axis of the photographing lens 11, and an opening of the pupil mask 22 Re-imaging lenses 23a, 23 arranged behind them corresponding to 22a, 22b
b is arranged.

Region H of exit pupil 11a of taking lens 11
A part of the light flux of the subject that has passed through a and Hb and is incident is reflected by the main mirror 12. Then, a part of the reflected light flux is reflected by the optical path switching element 16, and
Further, the light passes through the main mirror 12, passes through the openings 22a and 22b of the pupil mask 22, and passes through the re-imaging lenses 23a and 23a.
The image is re-formed on the area AF sensor 24 by b.

By detecting the interval between the two images re-formed in this manner, the in-focus state of the photographing lens 11 can be changed to the front focus,
It can be detected including the back pin. Specifically, 2
The light intensity distribution of the image is obtained from the pixel signal output of the area AF sensor 24, and the interval between the two images is measured.

FIG. 3 is a diagram showing an example of a photographing screen of the area AF 24 described above.

As described above, the focus can be detected by setting the wide area in the photographing screen 30 as the focus detection area 31.

FIG. 4 is a block diagram showing an electrical configuration of the camera according to the first embodiment.

Referring to FIG.
Is a control device of the camera system, and has a CPU inside.
(Central processing unit) 35a, ROM 35b, RAM 35
c, A / D converter (ADC) 35d and EEPROM
It is a controller having M35e. This camera is
A series of operations are performed according to a sequence program stored in the ROM 35b inside the microcomputer 35. Further, the EEPROM 35e stores correction data relating to focus adjustment, photometry / exposure calculation, and the like for each camera.

The microcomputer 35 includes, in addition to the area AF sensor 24, a photometry circuit 37, a lens drive circuit 38, a mirror drive circuit 39, and an aperture drive circuit 4.
0, a shutter driving circuit 41, and a film feeding section 42
, Display unit 43, optical path switching circuit 44, temperature measurement circuit 45
And are connected.

The photometric circuit 37 has a photometric element 46 and is controlled by the microcomputer 35 to perform a photometric operation and output a photometric signal. The photometric signal is supplied to the A / D converter 3 built in the microcomputer 35.
After being A / D converted by 5d, it is stored in the RAM 35c.

The lens driving circuit 38 drives the focusing optical system 11b in the taking lens 11 based on a command from the microcomputer 35.

The mirror drive circuit 39 is controlled by the microcomputer 35, and performs an up / down operation of the main mirror 12. Also, the aperture driving circuit 40
Drives an aperture mechanism (not shown) based on a command from the microcomputer 35.

The shutter drive circuit 41 is controlled by the microcomputer 35, and drives the shutter 13 to expose the film 14 to light. Further, the film feeding section 42 includes a microcomputer 35
The automatic loading after the film 14 is loaded into the camera, the winding after the shooting, and the rewinding operation after the completion of the shooting of all the frames are performed.

The display unit 43 is controlled by the microcomputer 35 and displays information such as the operation mode of the camera on a display element such as an LCD.

The optical path switching circuit 44 is controlled by the microcomputer 35, and drives the optical path switching element 16 to control the reflectance and the transmittance. This optical path switching circuit 4
Details of 4 will be described later.

The temperature measuring circuit 45 generates an analog voltage corresponding to the environmental temperature. And the microcomputer 3
Reference numeral 5 denotes an A / D converter 35
A / D converted by d and stored in the RAM 35c.

The microcomputer 35 has a power switch 50 for setting the camera operation / non-operation.
, A first release switch (1RSW) 51 and a second release switch (2RSW) 52 are connected.

The first release switch 51 and the second release switch 52 are switches linked to a release button (not shown). The first release switch 51 is turned on by pressing the release button in the first step, and the second release switch 52 is subsequently turned on by pressing the release button in the second step.

The microcomputer 35 performs photometry and AF operation when the first release switch 51 is turned on.
When the second release switch 52 is turned on, an exposure operation and a film winding operation are performed.

FIG. 5 is a diagram showing the configuration of the optical path switching circuit 44. It is assumed that the optical path switching circuit 44 partially includes the internal circuit of the microcomputer 35.

The optical path switching circuit 44 includes an optical path switching element driving circuit 55, a constant voltage circuit 63, and a DC / DC converter 6
7, a battery 68, a clock output circuit 71 and a D / A converter 72 which are part of the microcomputer 35.
And is configured.

The DC / DC converter 67 boosts the voltage V _CC of the supply battery 68 power to the entire camera system for generating a V _DCDC with. In order to drive the optical path switching element 16, the output voltage (V _DCDC ) of the DC / DC converter 67 is set to be about 100V. D
A control signal line for controlling the operation / non-operation of the C / DC converter 67 is connected to the I / O of the microcomputer 35.
It is connected to a terminal DCDCON which is an O port.

The constant voltage circuit 63 includes a transistor 64
, An operational amplifier 65, and a feedback resistor R _AAnd R_BAnd from
Is done. The constant voltage circuit 63 is connected to the DC / DC converter.
Optimal for driving the optical path switching element 16 from the output of the barter 67
Voltage V_LCDCreate

The driving voltage V _LCD of the optical path switching element 16 is set by the voltage input to the non-inverting terminal of the operational amplifier 65, and the D / A built in the microcomputer 35
The output voltage (V _DAC ) of the converter 72 is input. The driving voltage V _LCD can be obtained by the following equation (1). V _LCD = (R _A + R _B ) · V _DAC / R _B (1) The optical path switching element drive circuit 55 has four transistors 5
6, 57, 58, 59 and an inverter 60. The optical path switching element driving circuit 55 converts the DC voltage V _LCD output of the constant voltage circuit 63 into an AC voltage output of amplitude V _LCD and applies the converted voltage output to the optical path switching element 16.

A clock signal required to drive the optical path switching element driving circuit 55 is supplied from a clock output circuit 71 incorporated in the microcomputer 35.

Next, referring to the flowchart of FIG.
The operation of the microcomputer 35 will be described.

First, when the power switch 50, which is one of the operation switches, is turned on, the microcomputer 35
Operation is started. Then, in step S1, the system is initialized, and the I / O port, the memory, and the like in the microcomputer 35 are initialized.

Next, in step S2, the DC / DC converter 67 of the optical path switching circuit 44 is started. In step S3, the process waits for a stabilization time until the output of the DC / DC converter 67 is stabilized. In step S4, the clock output circuit 71 is set to output a clock signal to the optical path switching element driving circuit 55.

In step S5, a D / A converter 72 is read from the EEPROM 35e in the microcomputer 35.
(D _LCDON1 , D _LCDON2 ) and the standby time (T _W1 , T _W2 ) after the change of the driving voltage V _LCD are read out.

As shown in Table 1 below, the EEPROM 35e stores setting data of the D / A converter 72 in association with the environmental temperature Ta.

[0050]

[Table 1]

The optimum driving voltage V _LCD for maintaining the light path switching element 16 at a predetermined transmittance changes depending on the environmental temperature Ta.

The above Table 1 is stored in the RAM 35c as table data from the EEPROM 35e, and the environmental temperature T
a drive voltage V _LCD (setting data D _LCDON1 , D
_{LCDO N2} ) is selected. Here, the setting data is for setting the transmittance of the optical path switching element 16 to 50% and 10%, respectively. When the transmittance is 10%, the reflectance is 90%.

The EEPROM 35e has the following Table 2
As shown in ( ₂ ), standby times (T _W1 , T _W2 ) required until the image is stabilized after the transmittance is changed are stored in correspondence with the environmental temperature Ta. This is because the driving voltage V for changing the transmittance of the optical path switching element 16 depends on the environmental temperature Ta.
_This is because the time required for stabilizing the transmittance after changing the _LCD changes.

[0054]

[Table 2]

In this manner, the table data shown in Tables 1 and 2 is read from the EEPROM 35e and stored in the RAM 35c.

In step S6, temperature output data from the temperature measuring circuit 45 is input. Next, in step S7, the data (D _LCD1 ) serving as the driving voltage V _LCD for setting the optical path switching element 16 to the transmittance of 50% is set in the D / A converter 72.

Next, in step S8, the ambient temperature Ta
The waiting time T _W1 corresponding to the time T is selected from Table 2 above, and the time T
Wait for _W1 only. Further, in step S9, the luminance of the subject is measured by the photometric circuit 37, and photometric data is input. Then, photometric / exposure calculations are performed based on the photometric data, and a shutter speed and an aperture control value are calculated.

Here, since the photometric element 46 is disposed in the finder portion, it is affected by a change in the transmittance of the optical path switching element 16. For this reason, the correction value is
It is stored in the ROM 35e, and the correction is performed using this correction value.

Then, in step S10, the state of the first release switch 51 is detected. If the first release switch 51 is on, the process proceeds to step S13, and if it is off, the process proceeds to step S11.

In step S11, the power switch 50
Is detected. If the power switch 50 is off, the process proceeds to step S12, the microcomputer 35 enters the off mode, and the operation of the camera system is stopped. On the other hand, if the power switch 50 is on, the process proceeds to step S6 and the operation is continued.

As described above, the temperature measuring operation in step S6 is as follows.
It is periodically executed while the microcomputer 35 is operating. Therefore, as will be described later, even if the environmental temperature Ta changes, the optimum drive voltage V _LCD can always be applied to the optical path switching element 16 in accordance with the change, and an appropriate standby time T _W1 or the like is selected. be able to.

If the first release switch 51 has been turned on in step S10, the flow shifts to step S13, where it is determined whether the photometric value is smaller than a predetermined determination level _Bth . If the result of this determination is that the photometric value is smaller than the predetermined determination level _Bth , that is, if the luminance is low, the flow shifts to step S14, and
_Is changed to _DLCDON2 in Table 1 above.

As a result, the transmittance of the optical path switching element 16 is set to 10% and the reflectance is set to 90%, so that the amount of light guided to the focus detection optical system 21 increases. Therefore, the accumulation time of the area AF sensor 21 can be shortened even at low luminance, and the time lag of focus detection can be reduced.

In step S15, as the standby time after the transmittance is switched, the process waits for the standby time T _W2 shown in Table 2 above. Then, in step S16, the accumulation operation of the area AF sensor 24 and the reading operation of the pixel signal are performed, and the focus detection calculation is performed based on the pixel signal. Since the focus detection calculation is performed by a known phase difference detection method, a detailed description is omitted here.

Next, in step S17, as a result of the above-described focus detection calculation, it is determined whether or not the subject is in focus. Here, in the case of focusing, the process proceeds to step S19. On the other hand, if out of focus, the process moves to step S18, where the focus adjustment lens 11b is driven by the lens drive circuit 38 based on the result of the focus detection calculation to perform focus adjustment.

As described above, the above steps S16 to S18
Is repeatedly executed to obtain a focused state.

In step S19, the state of the second release switch 52 is detected. Here, if the second release switch 52 is on, the process proceeds to step S20.
The process proceeds to step S10 if the switch is off, and the above-described operation is repeatedly performed.

In step S20, the aperture drive circuit 40 is controlled, and an aperture mechanism (not shown) is stopped down to the aperture value for exposure. At the same time, the mirror driving circuit 39 is controlled to perform a mirror-up operation of the main mirror 12.

Subsequently, in step S21, the shutter drive circuit 41 is controlled at the shutter speed based on the exposure calculation, the shutter 13 is opened, and the film 14 is exposed.

Then, in step S22, the aperture driving circuit 40 is controlled, and an aperture mechanism (not shown) is opened. At the same time, the mirror driving circuit 39 is controlled to perform a mirror-down operation of the main mirror 12. Next, in step S23, the film feeding unit 42
Is controlled to perform a film winding operation.

A series of photographing operations is completed as described above, and the flow shifts to step S6 to repeat the same operation.

As described above, according to the first embodiment,
After the subject light beam having passed through the taking lens 11 is reflected by the main mirror 12, it is reflected by the optical path switching element 16 disposed in front of the film equivalent surface.
Is transmitted to the focus detection optical system 21 and the phase difference is detected, thereby enabling focus detection over a wider field of view.

Further, the light path switching element 1 according to the subject brightness
6, the focus detection time lag at the time of low luminance can be reduced.

The optical path switching element 16 may be a half mirror having a fixed transmittance.

Next, a second embodiment of the present invention will be described.

FIG. 7 shows a second embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a focus detection optical system 21.

[0077] As shown in FIG. 7, the difference from FIG. 2 of the first embodiment described above, the optical path switching device 16 is only the region 16 ₁ required for focus detection can control the transmittance, i.e. reflection And has a function of a so-called field mask that limits the range in which focus detection is performed. Region other than the region 16 ₁ is constituted by a transparent member 100% transmittance.

FIG. 8 shows a corresponding focus detection area 75 in the photographing screen 30 according to the second embodiment.

As described above, since the focus detection is performed with the focus detection field limited, it is possible to prevent harmful light rays from entering the focus detection optical system 21 and to improve the focus detection accuracy. .

FIGS. 9A and 9B show a modification of the second embodiment. FIG. 9A is a diagram showing a shooting screen 30 having a plurality of separated focus detection areas 75a, 75b, and 75c. FIG. 9 (b)
Are the focus detection areas 75a, 75b, 75 in FIG.
An example is shown in which the optical path switching element 16 can be switched to the reflection state for the portions 16a, 16b, and 16c corresponding to c.

Next, a third embodiment of the present invention will be described.

FIG. 10 is an optical path diagram of an optical apparatus to which the camera focus detection device according to the third embodiment is applied.

The difference from the first embodiment shown in FIG. 1 is that a concave optical path switching element 77 is provided in place of the optical path switching element 16.

The concave optical path switching element 77 has a light condensing property. The concave optical path switching element 77 has a focus detection light beam passing portion (not shown) of the exit pupil H of the photographing lens 11 and a pupil mask (not shown). ) Is set so as to function as a field mirror that makes a conjugate relationship with.

Therefore, the light amount of the focus detection light beam can be increased, and the focus detection accuracy and the low luminance detection limit can be improved.

The concave optical path switching element 77 may be a half mirror.

Next, a fourth embodiment of the present invention will be described.

FIG. 11 is an optical path diagram of an optical apparatus to which the camera focus detection device according to the fourth embodiment is applied.

The camera according to the fourth embodiment is an image pickup device for taking an image with an electronic image pickup device.

In the camera shown in FIG. 11, only parts different from those in FIG. 1 will be described.

The light beam passing through the photographing lens 11 is converted into an infrared light cut filter 79 for cutting infrared light components, and an optical LPF (low-pass filter) for reducing moiré and false colors.
The light passes through 80 and reaches the main mirror 12.

At the time of focus detection, the light beam reflected by the main mirror 12, which is a half mirror, is reflected by an optical path switching element 16 set to a predetermined reflectance.
Further, the light passes through the main mirror 12 and is guided to the focus detection optical system 21.

The light beam transmitted through the main mirror 12 is guided to the image sensor 81.

At the time of photographing, the main mirror 12 is retracted to the position shown by the broken line in FIG.

FIG. 12 is a block diagram showing an electrical configuration of a camera according to the fourth embodiment. FIG.
In FIG. 2, the same portions as those in FIG. 4 of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

The image pickup device (CCD) 81 is controlled by a CCD driving unit 83. Also, the CCD driving unit 83
Communicates with the microcomputer 35, and the operation timing and the like are controlled.

The video signal output from the image sensor 81 is
The image is processed by the video processing unit 84 and output to the recording unit 85. In the recording unit 85, the image signal processed by the video processing unit 84 is recorded in an internal recording device.

The image signal is supplied to a liquid crystal display section 43.
Can be displayed.

Next, with reference to the flowchart of FIG. 13, the microcomputer 3 according to the fourth embodiment will be described.
Operation 5 will be described.

The processing in steps S31 to S40, steps S41 to S46, and steps S58 and S59 in the flowchart of FIG. 13 is the same as that in the flowchart of FIG. 6 in the first embodiment described above.
1 to S10, steps S13 to S18 and step S1
1, since it is the same as S12, the description here is omitted.

If it is determined in step S45 that the subject is in focus, the flow shifts to step S47, where the image pickup device 81 is operated based on the exposure calculation.
Is performed, and the exposure is performed. Then
In step S48, an image signal is read from the image sensor 81. In step S49, signal processing is performed on the read image signal. Then, step S50
Then, an image is displayed by the display unit 43 on the processed image signal.

Next, in step S51, the state of the second release switch 52 is detected. If the second release switch 52 is on, the process proceeds to step S52, and if the second release switch 52 is off, the process proceeds to step S4.
After shifting to 0, the subsequent operations are repeatedly executed.

In step S52, the aperture drive circuit 40 is controlled, and the aperture mechanism (not shown) is stopped down to the aperture value for exposure. At the same time, the mirror driving circuit 39 is controlled to perform a mirror-up operation of the main mirror 12.

Thereafter, in step S53, the electronic shutter control of the image sensor 81 is performed at the shutter speed based on the exposure calculation, and the main exposure operation is performed. Next, in step S54, the aperture driving circuit 40 is controlled, and an aperture mechanism (not shown) is set in a light blocking state.

At step S55, an image signal is read from the image sensor 81. As described above, by reading the image signal in the light-shielded state, it is possible to prevent the occurrence of smear, which is a streak noise in the image.

In step S56, after the read image signal is subjected to signal processing, an image is recorded in the recording section 85. Further, the captured image is displayed on the display unit 43. Then, in step S57, the aperture driving circuit 40 is controlled, and the aperture mechanism (not shown) is opened. At the same time, the mirror driving circuit 39 is controlled,
The mirror down operation of the main mirror 12 is performed.

A series of photographing operations is completed as described above, and the flow shifts to step S36 to repeat the same operation.

If it is determined in steps S40 and S58 that the first release switch 51 is off and the power switch 50 is on, steps S60 to S6 are performed.
By 3, imaging and image display are performed. These steps S60 to S63 are the same as steps S47 to S5 described above.
Since the processing is the same as the processing of 0, the description is omitted.

As described above, even in cases other than the main exposure, the light beam transmitted through the main mirror 12, which is a half mirror, is picked up by the image pickup device 81 and is displayed as an image. In this mode, the luminous flux that has been wasted can be effectively used, and an image can be displayed at all times.

Next, a fifth embodiment of the present invention will be described.

FIG. 14 is a flowchart illustrating the operation of the microcomputer according to the fifth embodiment. In the fifth embodiment, other configurations are as follows.
This is the same as the first embodiment described above.

In the flow chart of FIG. 14, steps S71 to S88 are the same as the processing of steps S1 to S18 in the flow chart of the first embodiment, and a description thereof will be omitted.

If it is determined in step S87 that the subject is in focus, the flow shifts to step S89 to determine whether the AF mode is the single AF mode. Here, the single AF mode is a mode in which focus is locked once focus is achieved.

If it is determined in step S89 that the mode is not the single AF mode, the mode is the continuous AF mode. Therefore, the flow shifts to step S90 to detect the state of the second release switch 52. If it is determined in step S90 that the second release switch 52 is off, the process proceeds to step S80, and the focus detection is repeated. On the other hand, if the second release switch 52 is on, the process proceeds to step S95.

If it is determined in step S89 that the mode is the single AF mode, the flow shifts to step S91 to change the setting of the D / A converter 72, and the optical path switching element 16 transmits 100% transmittance (0% reflectance). (Table 1, D
_LCDON3 ). This eliminates the need for focus detection, and thus guides all light beams to the finder, making the finder brighter and easier to see.

Next, in step S92, as shown in Table 2, the process waits for the waiting time T _W3 .

Then, in step S93, the state of the second release switch 52 is determined. here,
If it is on, the flow shifts to the exposure sequence from step S95. On the other hand, if it is off, the process moves to step S94, and it is determined whether or not the first release switch 51 is on.

Here, the first release switch 51
Is ON, the flow shifts to step S93, where the state of the second release switch 52 is detected. On the other hand, if the first release switch 51 is off at step S94, the focus lock has been released, and the light path switching element 16 has the transmittance 50 at step S81 and thereafter.
% (Reflectance 50%), and the focus detection is restarted.

The exposure sequence of steps S95 to S98 is the same as that of the first embodiment described above with reference to FIG.
Are the same as steps S20 to S23 of the flowchart of FIG.

As described above, in the single AF mode, the optical path switching element 16 is set to have a transmittance of 100% after focusing, so that the finder can be more easily observed.

According to the above embodiment of the present invention,
The following configuration can be obtained.

(1) A first optical element that reflects a part of the subject light beam that has passed through the taking lens in a direction different from the film surface, and a first optical element that is located in front of a surface equivalent to the film surface. It reflects the luminous flux reflected by
A second optical element that can be set to a predetermined reflectance; and a focus detection unit that receives a light beam reflected by the second optical element and performs focus detection. A focus detection device for a camera, which can be switched between a reflection state and a transmission state, and is switched to a reflection state when performing a focus detection operation.

(2) The focus detection device for a camera according to the above (1), wherein the reflectance of the second optical element is set according to the luminance of the subject.

(3) A first optical element that reflects at least a part of the subject light beam that has passed through the photographing lens and can be retracted from the photographing optical path, and is disposed in front of the film transmitting surface and reflects the first optical element. A second optical element that reflects a light beam; and a focus detection unit that performs focus detection based on the light beam reflected by the second optical element. The light beam reflected by the second optical element is transmitted to the first optical element. A focus detection device, wherein the light is transmitted by an optical element and guided to the focus detection unit.

(4) The focus detection device according to (3), wherein the second optical element is capable of electrically controlling the reflectance and the transmittance.

(5) The focus detection device according to (3), wherein the second optical element is disposed in front of a focusing plate.

[0127]

As described above, the subject light beam that has passed through the taking lens is reflected by the optical path switching element disposed in front of the film equivalent surface, and then transmitted through the main mirror to the focus detection optical system. By detecting the phase difference, it is possible to provide a camera focus detection device capable of detecting a focus in a wider field of view.

[Brief description of the drawings]

FIG. 1 shows an optical path diagram of an optical apparatus to which a camera focus detection device according to the present invention is applied.

FIG. 2 is a diagram showing a configuration of a focus detection optical system 21 of FIG.

FIG. 3 is a diagram illustrating an example of a shooting screen of an area AF24.

FIG. 4 is a block diagram illustrating an electrical configuration of the camera according to the first embodiment.

FIG. 5 is a diagram showing a configuration of an optical path switching circuit 44 of FIG. 4;

FIG. 6 is a flowchart illustrating an operation of the microcomputer 35 according to the first embodiment.

FIG. 7 is a diagram showing a configuration of a focus detection optical system 21 according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a focus detection area 75 in a shooting screen 30 according to the second embodiment.

FIG. 9 shows a modification of the second embodiment,
(A) shows a plurality of separate focus detection areas 75a, 75
FIG. 3B shows the photographing screen 30 having the b and 75c, and FIG. 4B shows the light path switching element 16 in the reflection state for the portions 16a, 16b and 16c corresponding to the focus detection areas 75a, 75b and 75c in FIG. It is the figure which showed the example which made switching possible.

FIG. 10 is an optical path diagram of an optical device to which a camera focus detection device according to a third embodiment is applied.

FIG. 11 is an optical path diagram of an optical apparatus to which a focus detection device for a camera according to a fourth embodiment is applied.

FIG. 12 is a block diagram illustrating an electrical configuration of a camera according to a fourth embodiment.

FIG. 13 is a flowchart illustrating an operation of a microcomputer 35 according to the fourth embodiment.

FIG. 14 is a flowchart illustrating an operation of a microcomputer according to the fifth embodiment.

[Description of Signs] 11 shooting lens, 11a exit pupil, 12 main mirror, 13 shutter, 14 film, 16 optical path switching element, 17 focus plate, 18 pentaprism, 19 eyepiece, 21 focus detection optical system, 22 pupil mask, 22a, 22b aperture, 23, 23a, 23b re-imaging lens, 24 area AF sensor, 30 shooting screen, 31 focus detection area, 35 microcomputer, 35a CPU (central processing unit), 35b ROM, 35c RAM, 35d A / D converter (ADC), 35e EEPROM, 37 photometric circuit, 38 lens drive circuit, 39 mirror drive circuit, 40 aperture drive circuit, 41 shutter drive circuit, 42 film feeding section, 43 display section, 44 optical path switching circuit, 45 Temperature measurement circuit, 46 photometry elements, 50 power Switch, 51 a first release switch (1RSW), 52 second release switch (2RSW), 55 an optical path switching element driving circuit, 63 a constant voltage circuit, 67 DC / DC converter, 68 battery, 71 a clock output circuit, 72 D / A converter.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Maruyama 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (72) Inventor Toshiaki Ishimaru 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. F term (reference) 2H011 AA01 BA23 BB01 2H051 BA02 CB11 CB14 CB15 CB22 DA07

Claims (3)

[Claims] A first optical element that reflects a part of a subject light beam that has passed through a taking lens in a direction different from a film surface; and a first optical element that is located in front of a surface equivalent to the film surface. A focus detection device for a camera, comprising: a second optical element that further reflects the reflected light beam; and focus detection means that receives the light beam reflected by the second optical element and performs focus detection. . 2. The light beam reflected by the second optical element,
2. The focus detection device for a camera according to claim 1, wherein the light passes through the first optical element and reaches the light receiving unit. 3. The apparatus according to claim 1, wherein the second optical element is electrically switchable between a reflection state and a transmission state, and is switched to a reflection state when performing a focus detection operation.
3. A focus detection device for a camera according to claim 1.