JP2000329997A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the focus of a wider visual field range. SOLUTION: This focus detector is provided with a main mirror 3 consisting of a half mirror reflecting and transmitting objective luminous flux transmitting through a photographing optical system 1 toward a finder optical system side, an optical path switching element 4 which is arranged near the front surface of a film 2 and whose characteristics can be electrically switched to the reflecting mode and the transmitting mode and a focus detection optical system 10 and an AF sensor 11 disposed at the bottom part of a mirror box being the lower part of the mirror 3. To detect the focus, the characteristics of the element 4 is switched to the reflecting mode so that the luminous flux is reflected forward. Then, the luminous flux is reflected toward the optical system 10 and the sensor 11 besides by the mirror 3. When a photographing action is executed, the characteristics of the element 4 becomes the transmitting mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a focus detecting device, and more particularly, to a focus detecting device which performs focus detection using a subject light beam that has passed through a photographing optical system.

[0002]

2. Description of the Related Art There have been proposed many focus detecting devices used in optical apparatuses such as cameras.

As an example of such a camera, for example, Japanese Patent Application Laid-Open No. 9-184965 describes a camera that performs focus detection by a TTL phase difference detection method.

In the camera described in this publication, for example, a sub-mirror that guides a light beam transmitted through a main mirror to a focus detection unit is an elliptical mirror, thereby guiding a wide range of light beams to a focus detection optical system to cover a wide range. It is configured to enable cross focus detection.

[0005]

However, according to the technique described in Japanese Patent Application Laid-Open No. 9-184965, if the focus is to be detected over a wider range, the area of the sub-mirror must be changed according to the size of the range to be detected. Although it is necessary to increase the size of the sub-mirror, if the size of the sub-mirror is increased, the sub-mirror may come into contact with a member such as a shutter.

The present invention has been made in view of the above circumstances, and has as its object to provide a focus detection device capable of detecting a focus in a wider field of view.

[0007]

In order to achieve the above object, a focus detection apparatus according to a first aspect of the present invention includes a first optical element that transmits at least a part of a subject light beam that has passed through a photographing optical system, and a film. A second optical element that is disposed on the front surface of the first optical element and reflects a light beam transmitted through the first optical element when performing focus detection; 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 further reflected by the first optical element and guided to the focus detection unit.

[0008] Further, a focus detection device according to a second aspect of the present invention comprises:
A first optical element that transmits at least a part of the subject light beam that has passed through the photographing optical system, and a second optical element that is disposed on the front surface of the film and reflects the light beam that has passed through the first optical element when performing focus detection. A focus detection unit that performs focus detection based on the light beam reflected by the second optical element, and the second optical element is an optical path switching element that can electrically switch between reflection characteristics and transmission characteristics. .

Further, a focus detecting device according to a third aspect of the present invention is the focus detecting device according to the first aspect, wherein the second optical element is switched to a reflection characteristic at the time of focus detection and to a transmission characteristic at the time of photographing. .

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show a first embodiment of the present invention. FIG. 1 is a diagram showing an optical path of a camera to which a focus detection device is applied, and FIG. 2 is mainly a focus detection optical system including a photographing optical system. FIG. 3 is a perspective view showing a main part of the system, FIG. 3 is a diagram showing a focus detection area in a photographing screen, FIG. 4 is a block diagram mainly showing an electric configuration of the camera, and FIG. FIG. 6 is a flowchart showing the operation of the microcomputer.

The first embodiment is an example in which the focus detection device is applied to a silver halide camera as an optical device.

This camera comprises a photographing optical system 1 for forming a subject image, and a movable quick-disc disposed rearward on the optical axis O of the photographing optical system 1 and having a reflecting surface formed as a half mirror. A main mirror 3 serving as a first optical element including a return mirror and the like, and a reflection characteristic and a transmission characteristic arranged at a position further behind the main mirror 3 and near a front surface of a film 2 described later can be switched. An optical path switching element 4 as a second optical element, a shutter 8 disposed behind the optical path switching element 4, and a position behind the shutter 8 at a position to be a focal plane (imaging plane) of the photographing optical system 1. A film 2 serving as an image pickup means provided; a focus plate 5 provided at a position optically equivalent to the film 2 and configured to form an image of light reflected upward by the main mirror 3; Imaged A pentaprism 6 for inverting a subject image to an erect erect image, an eyepiece 7 for enlarging an image emitted from the pentaprism 6 and projecting the image to an observer's eye, and a lower side of the main mirror 3. The pupil mask 13 and the re-imaging lens 12 which are disposed at the bottom of the mirror box
And an AF sensor 11 that performs focus detection based on a subject image re-imaged by the focus detection optical system 10.

The symbol H of the photographing optical system 1 indicates an exit pupil, and the focus detecting section includes a focus detecting optical system 10 and an AF sensor 11.

The passage of light by the camera having such a configuration is performed as follows.

First, when observing a subject image, a light beam incident from the photographing optical system 1 is reflected upward by the main mirror 3 and forms an image on the focus plate 5 once. And projected to the observer's eye.

Next, when focus detection is performed by the AF sensor 11, the light beam incident from the photographing optical system 1 passes through the main mirror 3 and reaches the position of the optical path switching element 4. At this time, the light path switching element 4 is in a state of reflecting the light beam, and the light beam is reflected again to the main mirror 3 side. The light beam that has reached the main mirror 3 is reflected downward by the main mirror 3 this time, and the focus detection optical system 1
After being incident on 0, an image is formed on the AF sensor 11 as a focus detection light beam, and focus detection is performed.

Further, when the film 2 is exposed, the light beam incident from the photographing optical system 1 reaches the position of the main mirror 3, but at the time of exposure, the main mirror 3 is flipped up and retracted from the optical path. The light beam passes as it is and reaches the position of the optical path switching element 4. At this time, the light path switching element 4 is in a state of transmitting the light beam, and the subject light beam reaches the shutter 8 through the light path switching element 4. At the time of exposure, the shutter 8 is also opened to allow light to pass therethrough, so that the light beam is
And exposure is performed.

The optical path switching element 4 is, as described above,
It is arranged on the optical axis O of the photographing optical system 1 in front of the shutter 8 and controls a reflection characteristic and a transmission characteristic by an electric signal to select a state of reflecting light and a state of transmitting light. It is an element that can be. Such an element is described, for example, in "NATURE VOL. 3922 APRIL1998".

In this optical path switching element, one of the surfaces formed of a transparent resin can be controlled to be in a state of transmitting and reflecting electric light. The optical path switching element is configured to transmit light when a voltage is applied, and to reflect light when no voltage is applied.

Next, referring to FIG.
Will be described.

The focus detection optical system 10 employs a known re-imaging phase difference detection method.

That is, as shown in FIG. 2, the pupil mask 13 is formed by forming openings 13a and 13b formed of a pair of left and right circular holes in, for example, a rectangular plate-like member.
Further, the re-imaging lens 12 is provided with these openings 13
a pair of left and right lenses 12a, 12 corresponding to
b.

In such a configuration, the subject luminous flux entering through the areas Ha and Hb (which are substantially symmetric with respect to the optical axis O) of the exit pupil 1a of the photographing optical system 1 is
As described above, after being transmitted through the main mirror 3, the light is reflected by the optical path switching element 4, and further reflected on the back surface of the main mirror 3, and the openings 13 a and 13 b of the pupil mask 13 are formed.
Further, the light passes through the re-imaging lenses 12a and 12b, and is re-imaged on the AF sensor 11 which is an area sensor.

From the sensor data output of the AF sensor 11 thus re-imaged, the light intensity distribution of the two images is obtained.
By calculating the interval between the two images, the in-focus state of the photographing optical system 1 can be detected including the front focus and the rear focus.

The focus detection area 15a in the photographing screen 15 when such a focus detecting optical system 10 is used is as shown in FIG. 3 and is slightly smaller than the photographing screen 15, but has a wider focus. It is possible to perform detection.

Next, the mainly electrical configuration of such a camera will be described with reference to FIG.

This camera includes a photometric circuit 23 for performing photometric calculation based on subject light received by the photometric element 22 and outputting a photometric signal, and an AF for performing focus detection as described above.
The sensor 11, a lens driving circuit 25 for driving the focus adjustment optical system in the photographing optical system 1 to focus on the film 2, and the reflection path and the transmission state by driving the optical path switching element 4. An optical path switching element driving circuit 24 for switching, a temperature measuring circuit 26 for generating an analog voltage according to the environmental temperature where the camera is placed, a mirror driving circuit 27 for performing an up operation and a down operation of the main mirror 3, An aperture driving circuit 28 for adjusting the amount of incident light by driving an aperture (not shown) provided in the photographing optical system 1, a shutter driving circuit 29 for driving the shutter 8 to perform an opening and closing operation, and after loading the film 2 A film feeding unit 30 for performing auto-loading, winding operation after photographing, rewinding operation after photographing all frames, and a display mode such as an LCD. 1R to a display unit 31 for displaying the information, is turned on by depressing the first stage of the release button
SW (first release switch) 32 and 2RS which is turned on by depressing the release button in the second stage
W (second release switch) 33, a power SW 34 serving as a main power switch for setting the camera to an operating state or a non-operating state, and the entire camera including the respective circuits by detecting the states of the switches. And a microcomputer 21 that controls the entire system.

The microcomputer 21 includes a CPU (central processing unit) 21a for performing various calculations and processes, and a ROM 2 in which sequence programs and data common to cameras of the same model to be manufactured at the time of manufacturing are recorded.
1b, a RAM 21c serving as a memory space for work by the CPU 21a, an A / D converter (ADC) 21d for digitizing and capturing analog signals output from each circuit in the camera, and EEPROM 21 in which correction data and the like are recorded
e.

That is, the microcomputer 21
Performs a series of operations in accordance with a sequence program stored in the ROM 21b, and corrects operations and controls based on correction data related to focus adjustment, photometry and exposure calculation stored in the EEPROM 21e. It has become.

The A / D converter 21d converts, for example, an analog signal input from the photometry circuit 23 or the temperature measurement circuit 26 into a digital signal.
The converted photometry data and temperature measurement data are stored in the RAM, for example.
21c.

The microcomputer 21
According to the sequence program, the 1RSW
When the switch 32 is turned on, a photometric operation and an AF operation are performed, and when the 2RSW 33 is turned on, an exposure operation and a film winding operation are performed.

Next, the configuration of the optical path switching element driving circuit 24 including a part of the internal circuit of the microcomputer 21 will be described with reference to FIG.

As shown in FIG. 5, the microcomputer 21 further has a D / A converter 21f and a clock output circuit 21g, and has a terminal DCDCON as an I / O port.

The terminal DC of the microcomputer 21
A control signal line for controlling operation / non-operation of the DC / DC converter 36 is connected to DCON.
This DC / DC converter 36 is for generating a voltage VDCDC by boosting a voltage Vcc of a battery 37 which is a power supply for supplying power to the entire camera. The output voltage VDCDC of the DC / DC converter 36 is set to be about 100 V in order to drive the optical path switching element 4.

The above-mentioned D of the microcomputer 21
A constant voltage circuit 35 is connected to the / A converter 21f. The constant voltage circuit 35 has a transistor 35c, an operational amplifier 35d, and feedback resistors 35a and 35b (each resistance value is denoted by Ra and Rb). The optical path switching element 4 is connected to the output of the DC / DC converter 36.
A voltage VLCD optimum for driving the LCD is produced.

More specifically, the driving voltage VLCD of the optical path switching element 4 is set by the voltage input to the non-inverting terminal of the operational amplifier 35d. The output voltage VDAC of the / A converter 21f is input. At this time, the voltage V generated by the constant voltage circuit 35
LCD can be obtained by the following equation (1).

[0037]

VLCD = (Ra + Rb) .VDAC / Rb

The voltage VLCD thus generated is input to the optical path switching element driving circuit 24. The optical path switching element driving circuit 24 converts a DC output of a voltage VLCD into an AC output of an amplitude VLCD and applies the converted output to the optical path switching element 4, and includes transistors 24a, 24b, 24c, 24d and an inverter 24e. It is configured. A clock signal required to drive the optical path switching element drive circuit 24 is supplied from a clock output circuit 21g of the microcomputer 21 and is input to the inverter 24e.

Next, the operation of the microcomputer 21 will be described with reference to FIG.

When the power switch 34 is turned on, the microcomputer 21 starts operating, and first, the system is initialized (step S1). Here, the I / O port and the memory (RA
Initialization such as M21c) is performed.

Next, the DC / DC converter 36 is started to supply power to the optical path switching element driving circuit 24 (step S2).
6 waits for a predetermined time (stabilization time) until the output is stabilized (step S3).

In order to output a clock signal to the optical path switching element driving circuit 24, the clock output circuit 21
g is set (step S4).

Subsequently, data (D) for setting the D / A converter 21f is read from the EEPROM 21e.
LCDON) and a standby time (TW1, TW) described later after switching the optical path.
W2) is read (step S5).

The EEPROM 21e has a D / A converter 2 corresponding to the ambient temperature Ta as shown in Table 1.
1f setting data (DLCDON) is stored.

[0045]

[Table 1]

The optimum drive voltage VLCD for maintaining the light path switching element 4 in the transmission state changes depending on the environmental temperature Ta. Therefore, table data as shown in Table 1 above is stored in the RAM 21c from the EEPROM 21e, and the driving voltage VLCD (setting data DLC) corresponding to the environmental temperature Ta is stored.
DON).

Further, as shown in Table 2, standby times (TW1, TW2) required until the optical path is stabilized after the switching of the optical path are stored in the EEPROM 21e in correspondence with the environmental temperature Ta.

[0048]

[Table 2]

This is because the time required for the optical path switching element 4 to change from the transmission state to the reflection state or the time required for the optical path switching element 4 to change from the reflection state to the transmission state changes depending on the environmental temperature Ta. .

The table data as shown in Table 2 is also read from the EEPROM 21e and stored in the RAM 21c.

Subsequently, the temperature output data from the temperature measuring circuit 26 is inputted (step S6), the setting of the D / A converter 21f is cleared, the applied voltage of the optical path switching element 4 is set to 0, and the reflection state is set. It is set (step S7).

Thereafter, the standby time T corresponding to the environmental temperature Ta
W1 is selected from Table 2 above, and waits for this time TW1 (step S8).

Then, the luminance of the subject is measured by the photometric circuit 23.
And the measurement by the photometric element 22, input the photometric data, perform an exposure calculation based on the photometric data, and calculate the shutter speed and the aperture control value (step S).
9).

Next, the state of the 1RSW 32 is detected (step S10), and if the 1RSW 32 is on, the process proceeds to step S11 described later.

On the other hand, when the 1RSW 32 is off, the state of the power SW 34 is detected (step S2).
1) If the power switch 34 remains on, the operation returns to step S6 to continue the operation. If the power switch 34 is off, the microcomputer 21 enters the off mode and the camera system is turned off. The operation is stopped (step S22).

As described above, the temperature measurement operation in step S6 is periodically executed while the microcomputer 21 is operating. Therefore, as will be described later, even if the environmental temperature Ta changes, the optimum drive voltage VLCD can always be applied to the optical path switching element 4 in accordance with the change, and the appropriate standby times TW1 and TW2 can be selected. Can be.

In step S10, 1RSW3
When the switch 2 is turned on, the light beam reflected by the optical path switching element 4 is guided to the AF sensor 11 via the focus detection optical system 10, and the phase difference detection system output from the AF sensor 11 is used. A known focus detection calculation is performed based on the sensor data (step S11).

Then, it is determined whether or not the subject is in focus based on the result of the focus detection calculation (step S).
12) If not in focus, the lens drive circuit 25 executes lens drive based on the result of the focus detection calculation to adjust the focus (step S13), and then returns to step S11. Thus, step S
By repeatedly executing the steps 11 to S13, a focused state is finally attained.

If it is determined in step S12 that the object is in focus, then the 2RSW 33
Is checked (step S14), 2RSW 33
Is off, the process returns to step S10 to repeatedly execute the above-described operation.

On the other hand, in step S14, 2RSW
When the switch 33 is on, the RAM 21c is already turned on as described above in order to make the light path
Based on the table data (Table 1) stored in
Drive voltage data corresponding to the environmental temperature Ta is selected. Then, this drive voltage data (DLCDON) is set in the D / A converter 21f (step S15).

Thereafter, based on the table data (right column of Table 2) stored in the RAM 21c, a standby time TW2 corresponding to the environmental temperature Ta is selected, and the process waits for the standby time TW2 (step S16).

An exposure operation is performed in the subsequent steps S17 and subsequent steps.

That is, the aperture driving circuit 28 is controlled to reduce the aperture (not shown) to the aperture value for exposure, and at the same time, the mirror driving circuit 27 is controlled to perform the mirror-up operation of the main mirror 3 ( Step S1
7).

The shutter 8 is operated by controlling the shutter drive circuit 29 according to the shutter speed based on the exposure calculation, and the exposure operation for the film 2 is performed (step S).
18).

When the exposure is completed, the aperture drive circuit 28 is controlled to open the aperture (not shown), and at the same time, the mirror drive circuit 27 is controlled to perform the mirror-down operation of the main mirror 3 (step S19).

Then, the film feeding unit 30 is controlled to wind the film 3 by one frame (step S20).

With this operation, a series of photographing operations for one frame is completed, and the process returns to step S6 to repeat the same operation in preparation for photographing the next frame.

According to the first embodiment, after the subject light beam passing through the photographing optical system is reflected by the optical path switching element arranged on the front side of the film, it is further reflected by the main mirror and the focus detection unit. Since the phase difference is detected there, focus detection can be performed in a wider field of view. In addition, since the optical path switching element that can electrically switch between the reflection state and the transmission state is used, it is possible to secure a photographing optical path without using a movable member, and to reduce the size of the apparatus. In addition to this, there is an advantage that the time lag at the time of shooting does not become long.

FIGS. 7 and 8 show a second embodiment of the present invention. FIG. 7 is a perspective view mainly showing a main part of a focus detecting optical system including a photographing optical system, and FIG. FIG. 7 is a diagram showing a focus detection area in a shooting screen as a photographic image.

In the second embodiment, the first
The description of the same parts as those of the embodiment is omitted,
Only the differences will be mainly described.

In the above-described first embodiment, the optical path switching element 4 switches between the light reflection state and the light transmission state in almost the entire area. On the other hand, in the second embodiment, As shown in FIG. 7, the optical path switching element 4 is configured to switch between the light reflection state and the light transmission state only in the area 4a necessary for focus detection.

Thus, only the light in the area 4a can be reflected and reach the focus detection optical system 10 and the AF sensor 11 side, so that it has a so-called field mask function of limiting the range in which focus detection is performed. It has become.

FIG. 8 shows a modification in which the area of the optical path switching element is divided. The optical path switching element 4A as the second optical element shown in FIG. 8 is divided into a plurality, for example, four. Rectangular areas 4b, 4c, 4d, and 4e are provided.

These areas 4b, 4c, 4d, 4e are:
It corresponds to the focus detection area divided into a plurality of parts, and each can independently switch between the reflection state and the transmission state.

If the configuration as shown in FIG. 8 is used,
Focus detection can be performed for a desired area.

According to the second embodiment, the same effects as those of the first embodiment can be obtained, and the area of the optical path switching element can be reduced to restrict the field of view. Without providing a light source, it is possible to prevent a light beam that prevents accurate focus detection from being incident on the focus detection optical system, and it is possible to improve focus detection accuracy without increasing costs.

Further, by providing a plurality of areas of the optical path switching element and controlling them independently, a necessary area can be appropriately set as a distance measurement target.

FIG. 9 shows a third embodiment of the present invention, and is a diagram showing an optical path of a camera to which a focus detection device is applied.

In the third embodiment, the description of the same parts as those in the first and second embodiments will be omitted, and only different points will be mainly described.

In this embodiment, a concave total reflection mirror 41 is arranged as the second optical element instead of the optical path switching element 4 of the first embodiment.

That is, in this camera, when performing focus detection, as shown in FIG. 9, a concave total reflection mirror 41 is located on the front side of the shutter 8 and directs a light beam for focus detection to the main mirror 3. To reflect light.

The concave total reflection mirror 41 has a light condensing property, and makes the focus detection light beam passing portions Ha and Hb of the exit pupil H of the photographing optical system 1 and the pupil masks 13a and 13b conjugate. It functions as a field mirror.

The concave total reflection mirror 41 is provided so as to be movable by a driving mechanism (not shown).
When the main mirror 3 is exposed, the main mirror 3 is retracted from the photographing optical path in conjunction with the mirror-up operation.

After the exposure is completed, similarly,
The main mirror 3 is inserted at the position shown in FIG. 9 in the photographing optical path in conjunction with the mirror down operation.

A modification of the configuration shown in FIG. 9 is that, instead of the concave total reflection mirror 41, an optical path switching element similar to that of the above-described first embodiment is used. If an optical path switching element functioning as a concave surface is used, no moving mechanism is required, and cost reduction and space saving can be achieved.

According to the third embodiment, substantially the same effects as those of the first and second embodiments can be obtained, and by using a concave total reflection mirror, no additional optical system is required. And a part of the power of the focus detection optical system. Furthermore, if an optical path switching element is used, no moving mechanism or the like is required, so that cost reduction and space saving can be achieved.

FIGS. 10 to 12 show a fourth embodiment of the present invention. FIG. 10 is a diagram showing an optical path of an electronic camera to which a focus detection device is applied, and FIG. FIG. 12 is a flowchart showing the operation of the microcomputer.

In the fourth embodiment, the first
Therefore, description of the same parts as those of the third embodiment will be omitted, and only different points will be mainly described.

The fourth embodiment is an example in which the focus detection device is applied to an electronic camera as an optical device.

That is, in this electronic camera, as shown in FIG. 10, a light beam passing through the photographing optical system 1 reduces an infrared light cut filter 51 that cuts an infrared light component, and reduces moire, false colors, and the like. Optical LPF (Low Pass Filter) 5
2 and then enter the main mirror 3.

A CCD 53 as an image pickup device serving as an image pickup means is disposed behind the main mirror 3 on the optical axis O via the optical path switching element 4. In this electronic camera, since the optical path switching element 4 has a function of blocking light reaching the CCD 53,
The shutter 8 is provided between the optical path switching element 4 and the CCD 53.
Is not provided.

The other parts are the same as those shown in FIG.

In such an electronic camera, when performing focus detection, a light beam transmitted through the main mirror 3 which is a half mirror is reflected by the optical path switching element 4 set to the reflection state, and further reflected by the main mirror 3. The result is guided to the focus detection optical system 10 as in the first embodiment described above.

Next, when taking a picture, the main mirror 3 is moved up to retract from the photographing optical path.
The photographing light beam passes through the light path switching element 4 set in the transmission state, and is guided to the CCD 53 to form an image.

Next, the mainly electrical configuration of such an electronic camera will be described with reference to FIG.

The microcomputer 21 has a CCD
The CCD drive circuit 54 communicates with the drive circuit 54 to instruct operation timing and the like, and the CCD drive circuit 54 controls and drives the CCD 53 based on the command.

The CCD 53 photoelectrically converts the formed subject image and outputs the image signal as an image signal. The image signal is input to a video processing unit 55, where various processes are performed.

The signal processed by the video processing unit 55 is recorded by a recording unit 56 on an appropriate recording medium such as a flash memory.

The signal processed by the video processing section 55 can be displayed on the display element of the display section 31.

Since the electronic camera does not use a film, the film feed section 30 is naturally not provided, and the shutter drive circuit 29 is also provided since the shutter 8 is not provided as described above. Not been.

The other parts are almost the same as those shown in FIG. 4 of the first embodiment.

Next, the operation of the microcomputer 21 will be described with reference to FIG. This FIG.
In FIG. 7, the same parts as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be mainly described.

After the control of the aperture and the main mirror 3 is performed in step S17, the CCD 53 is driven by the CCD drive circuit 54 to perform electronic shutter control, and charges are accumulated for a predetermined time (step S3).
0).

Thereafter, post-processing of the aperture and the main mirror 3 is performed in step S19, and then the D / A
The converter 21f is cleared and the optical path switching element 4 is set to the reflection state (step S31). Therefore, at this time, the photographing light flux does not reach the CCD 53 and is in a light-shielded state.

Next, the standby time TW1 corresponding to the environmental temperature Ta
And waits for the standby time TW1 (step S
32) Thereafter, an image signal is read from the CCD 53 while keeping the CCD 53 in the light-shielded state (step S33). By reading the image signal in the light-shielded state in this way, it is possible to prevent the occurrence of smear, which is a streak noise that may occur in an image.

Then, after the read image signal is processed by the video processing unit 55, it is recorded on the recording medium by the recording unit 56 (step S34), and the process returns to step S6 to perform the next photographing.

According to the fourth embodiment, substantially the same effects as those of the first embodiment can be obtained in the electronic camera. Furthermore, since the image pickup element is shielded from light by using the optical path switching element, a dedicated light shielding member such as a shutter is not required, and a movable part for driving the light shielding member is not required. It is possible to simplify and reduce costs.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications and applications are possible without departing from the gist of the invention.

[Appendix] According to the embodiment of the present invention described in detail above, the following configuration can be obtained.

(1) A first optical element that transmits at least a part of the subject light beam that has passed through the photographing optical system, and a light beam that is arranged on the front surface of the imaging means and that has passed through the first optical element when performing focus detection. A second optical element that reflects light,
A focus detection unit that performs focus detection based on the light beam reflected by the optical element; and the light beam reflected by the second optical element is further reflected by the first optical element to the focus detection unit. A focus detection device, which is a guiding device.

(2) The focus detecting device according to (1), wherein the second optical element is an optical path switching element capable of electrically switching between reflection characteristics and transmission characteristics.

(3) The focus detection device according to (2), wherein the second optical element is switched to a reflection characteristic at the time of focus detection and a transmission characteristic at the time of photographing.

(4) The focus detection device according to (2), wherein the second optical element has a plurality of regions that can switch between reflection characteristics and transmission characteristics.

(5) The second optical element is capable of transitioning between a position where it is inserted into the photographing optical path from the photographing optical system to the image pickup means and a position where it is retracted from the photographing optical path. The focus detection device according to claim 1, characterized in that:

(6) The focus detecting device according to (5), wherein the second optical element comprises a total reflection mirror.

(7) The focus detecting device according to (6), wherein the second optical element has a reflecting surface formed as a concave surface.

(8) The focus detection device according to (1), wherein the imaging means is a silver halide film.

(9) The focus detecting device according to (1), wherein the imaging means is an imaging device.

(10) The supplementary note (9) is characterized in that the second optical element, when reading out an image signal from the image sensor, inhibits transmission of a subject light beam to the image sensor. The focus detection device according to any one of the preceding claims.

[0120]

As described above, according to the focus detection device of the present invention, it is possible to detect a focus in a wider field of view.

[Brief description of the drawings]

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

FIG. 2 is a perspective view mainly showing a main part of a focus detection optical system including a photographing optical system in the first embodiment.

FIG. 3 is a diagram showing a focus detection area in a shooting screen in the first embodiment.

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

FIG. 5 is a circuit diagram mainly showing a configuration of an optical path switching element drive circuit of the first embodiment.

FIG. 6 is a flowchart showing the operation of the microcomputer according to the first embodiment.

FIG. 7 is a perspective view mainly showing a main part of a focus detection optical system including a photographing optical system according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a focus detection area in a shooting screen as a modification in the second embodiment.

FIG. 9 is a diagram showing an optical path of a camera to which a focus detection device according to a third embodiment of the present invention is applied.

FIG. 10 is a diagram illustrating an optical path of an electronic camera to which a focus detection device according to a fourth embodiment of the present invention is applied.

FIG. 11 is a block diagram mainly showing an electrical configuration of the electronic camera according to the fourth embodiment.

FIG. 12 is a flowchart showing the operation of the microcomputer according to the fourth embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photographing optical system 2 film (imaging means) 3 main mirror (first optical element) 4, 4A optical path switching element (second optical element) 10 focus detection optical system (focus detection unit) 11 AF sensor (Focus detection unit) 41: concave total reflection mirror (second optical element) 53: CCD (imaging means, imaging element)

Continuation of the front page (72) Inventor Jun Maruyama 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Industrial Co., Ltd. (72) Inventor Toshiaki Ishimaru 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optics F term in Industrial Co., Ltd. (reference) 2H011 AA01 BA23 BB01 2H051 BA02 CB11 CB14 CB22 DA03 5C022 AA13 AB28 AB34 AC54 AC69 CA00

Claims (3)

[Claims] A first optical element that transmits at least a part of a subject light beam that has passed through an imaging optical system; and a first optical element that is disposed on a front surface of a film and reflects the light beam that has passed through the first optical element when performing focus detection. A second optical element, 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 further converted to the first optical element. A focus detection device, wherein the light is reflected by an element and guided to the focus detection unit. 2. A first optical element that transmits at least a part of a subject light beam that has passed through an imaging optical system; and a first optical element that is disposed on a front surface of a film and reflects the light beam that has passed through the first optical element when performing focus detection. A second optical element, and a focus detection unit that performs focus detection based on the light beam reflected by the second optical element. The second optical element electrically has a reflection characteristic and a transmission characteristic. A focus detection device comprising a switchable optical path switching element. 3. The focus detection device according to claim 1, wherein the second optical element is switched to a reflection characteristic at the time of focus detection and a transmission characteristic at the time of photographing.