JP3206122B2 - Focus detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for detecting a focus adjustment state of a photographic lens in a plurality of areas of a field.

[0002]

2. Description of the Related Art There is known a focus detection device for detecting a focus adjustment state of a photographing lens in a plurality of areas of a field. In this type of focus detection device, a plurality of focus detection areas are provided in a shooting screen set on a predetermined focus plane of a shooting lens equivalent to a film surface, and focus detection is performed by a focus detection optical system through the focus detection areas. The luminous flux is guided on a plurality of pairs of photoelectric converters, the image shift amount of the pair of subject images formed on each pair of the photoelectric converters is obtained, and the distance between the imaging plane of the imaging lens and the expected focal plane, that is, Defocus amount is detected.

Normally, when the focus of a photographing lens is adjusted in an automatic focus adjustment mode (hereinafter, referred to as an AF mode), a main subject is generally often located closest to the camera.
From the plurality of defocus amounts detected in the plurality of focus detection areas by the closest priority algorithm, the closest defocus amount is determined as the final defocus amount, and the photographing lens is driven according to the defocus amount. I have.

On the other hand, a manual focusing mode (hereinafter, referred to as a manual focusing mode)
When the focus of the photographing lens is adjusted in the MF mode), the closest defocus amount is determined as a final defocus amount from a plurality of defocus amounts by a closest priority algorithm, and the defocus amount is determined. The focusing of the taking lens is determined on the basis of the above, and if the final defocus amount is equal to or less than a predetermined value, the focusing display is performed on the display device.

[0005]

However, in the conventional focus detection device, even in the MF mode, the final defocus amount is determined based on the closest priority algorithm. In some cases, the image is clearly displayed on the screen, and the in-focus display is not displayed on the display device even though the photographing lens is focused on the main subject.

This will be described in more detail. FIG.
Shows an example of a subject displayed on a finder screen. There is a person 2 as a main subject almost at the center of the photographing screen 1, a tree 3 on the right front, a car 4 on the left front, and a mountain 5 on the rear. Four focus detection areas 6a to 6d are set in the center of the photographing screen 1 in the horizontal direction, and the focus detection area 6c captures the person 2 and the focus detection area 6c.
d captures the tree 3, and the focus detection area 6 a captures the mountain 5. Now, it is assumed that the focus of the photographing lens is adjusted for such a subject in the MF mode and the person 2 is focused. However, in the conventional focus detection device, although the photographing lens is almost focused on the person 2, the focus is determined based on the defocus amount of the focus detection area 6d indicating the closest distance. 3, the rear focus mark 7a of the display device 7 is turned on.

In the MF mode, the photographer adjusts the focus of the photographing lens while looking at the intended main subject on the viewfinder screen. Therefore, when the main subject image becomes clear on the viewfinder screen, the photographing lens is adjusted to the main subject. You are in focus or near focus. In order to determine whether or not the photographing lens is focused on the main subject, the determination should be made based on the defocus amount of the focus detection area 6c capturing the focused main subject person 2. . At this time, the defocus amount of the focus detection area 6c shows the smallest value as compared with other defocus amounts.

SUMMARY OF THE INVENTION It is an object of the present invention to perform focus detection for a main subject that is being focused when manually adjusting the focus of a taking lens while looking at a subject image on a finder screen.

[0009]

Means for Solving the Problems The present invention will be described with reference to FIG. 1 which is a claim correspondence diagram. According to the present invention, a plurality of photographic screens set on a predetermined focal plane of a photographic lens equivalent to a film surface are provided. A focus detection area 100 for detecting a defocus amount indicating a distance between an imaging plane of the photographing lens and the expected focal plane in each focus detection area, and setting for setting a manual focus adjustment mode. Means 101, a lens detecting means 102 for detecting the mounting of the auto-focus lens, and the setting of the manual focusing mode by the setting means 101, or the mounting of the auto-focus lens is not detected by the lens detecting means 102 In such a case, the smallest one of a plurality of defocus amounts detected by the focus detection unit 100 is displayed as a focused state. If the autofocus lens is detected by the lens detecting means 102 and the manual focus adjustment mode is not set by the setting means 101, the defocus amount is determined. A defocus amount determining means 103 for determining a final defocus amount from a plurality of defocus amounts detected by the method different from that at the time of setting the manual focus adjustment mode, and the defocus amount determining means 1
There is provided a determining unit 104 for determining the focus of the photographing lens based on the final defocus amount determined in 03, and a notifying unit 105 for notifying the determination result of the determining unit 104.

[0010]

[Function] When the manual focus adjustment mode is set,
Alternatively, if the attachment of the autofocus lens is not detected, the smallest one of the plurality of defocus amounts is determined as the final defocus amount for displaying the in-focus state, and the attachment of the autofocus lens is determined. Detected,
If the manual focus adjustment mode is not set, the final defocus amount is determined from a plurality of defocus amounts by a method different from that when the manual focus adjustment mode is set. Then, based on the final defocus amount, focus determination of the photographing lens is performed, and the determination result is notified. As a result, focus detection can be performed on the main subject on which the photographer is focusing.

[0011]

FIG. 2 shows an embodiment of the present invention. The luminous flux from the subject passes through the taking lens 10 and reaches the main mirror 11, a part of which is reflected by the main mirror 11 and guided to the finder screen 12, and the subject image is formed on the finder screen 12. This subject image is observed by the photographer via the pentaprism 13. Another part of the light beam from the subject that has reached the main mirror 11 is transmitted through the main mirror 11 and reflected by the sub-mirror 14, and guided to the charge storage type photoelectric converter 16 by the focus detection optical system 15.

FIG. 3 shows a configuration example of a focus detection optical system and a photoelectric converter. The focus detection optical system 15 includes a condenser lens 17, the most image forming lenses 18a and 18b, and the like.
A pair of light beams that have passed through different areas of the exit pupil plane 19 of the photographing lens 10 are guided to a pair of light receiving units 16 a and 16 b on the charge storage type photoelectric converter 16. Each of the light receiving sections 16a and 16b is composed of a plurality of photoelectric conversion elements as shown in FIG. 4, and each element outputs an electric signal corresponding to the light intensity of the subject image formed on each of the light receiving sections 16a and 16b. In this embodiment, as shown in FIG. 7, four focus detection areas 6a to 6d are set in the photographing screen 1, and a plurality of photoelectric conversion elements of each of the light receiving sections 16a and 16b are connected to each of the focus detection areas 6a to 6d. Grouping corresponding to 6d. The groups A1 and B1 are in the focus detection area 6a, and the groups A2 and B2 are in the focus detection area 6b.
The groups A3 and B3 correspond to the focus detection area 6c, and the groups A4 and B4 correspond to the focus detection area 6d.

A microcomputer (hereinafter referred to as a CPU) 20 includes peripheral components such as an AD converter and a memory.
Performs various calculations and sequence control of the camera. Lens C
The PU 21 is provided in the lens barrel of the taking lens 10,
Information about the photographing lens 10 such as whether or not it is an automatic focusing lens (hereinafter, referred to as an AF lens) is output to the CPU 20. The lens driving circuit 22 includes a lens motor 23 according to the lens driving amount and the driving direction calculated by the CPU 20.
Is driven to move the taking lens 10. Switch 24
Is a switch that opens and closes in conjunction with an AF / MF mode switching button (not shown), and closes when set to the MF mode. The display 7 displays the focus adjustment state of the photographing lens 10 based on the final defocus amount calculated by the CPU 20. The photographer may be notified of the focus adjustment state of the photographing lens 10 based on the final defocus amount by using a buzzer or a speaker.

FIGS. 5 and 6 are flowcharts showing examples of control programs executed by the CPU 20. The operation of the embodiment will be described with reference to these flowcharts. In step S1, the photoelectric converter 16 is made to perform charge accumulation for a predetermined time, and in step S2, a focus detection signal of the accumulation result is input from the photoelectric converter 16. In step S3, the photoelectric conversion element group A corresponding to each of the focus detection areas 6a to 6d
A known focus detection calculation is performed based on the focus detection signals of 1, B1 to A4, and B4 to calculate defocus amounts DEF1 to DEF4 of the focus detection areas 6a to 6d.

In step S4, the defocus amount DEF1
To DEF4, the minimum defocus amount and the closest defocus amount are detected and stored in the memory. In step S5, the state of the switch 24 is detected, and information on whether or not the lens is an AF lens is input from the lens CPU 21. In step S6, it is determined whether or not the mode is the manual focus adjustment mode. AF lens is attached and AF / M
If the AF mode is set by the F mode switch button, the process proceeds to step S14. If the AF mode is not set, or if the MF mode is set by the AF / MF mode switch button even when the AF lens is attached, step S7. Proceed to.

In the case of the MF mode, the smallest one of the defocus amounts DEF1 to DEF4 is determined as the final defocus amount in step S7. On the other hand, in the case of the AF mode, it is determined in step S14 whether or not the lens is driven for the first time. If it is the first time, the process proceeds to step S16, and if not, the process proceeds to step S15. In step S15, it is determined whether or not the lens was focused in the previous lens driving. If the lens is focused, the process proceeds to step S7; otherwise, the process proceeds to step S7.
Proceed to 16. In step S16, the defocus amount DEF
A value indicating the closest distance from 1 to DEF4 is determined as the final defocus amount. In the AF mode, the main subject is often at the closest position when driving the lens for the first time, so the first lens driving is performed based on the closest defocus amount. However, after focusing, the main subject is often located in the focus detection area showing the minimum defocus amount at the lens position, and therefore the lens is driven based on the minimum defocus amount.

Next, the process proceeds to step S8 in FIG. 6 to determine whether or not the determined final defocus amount is 50 μm or less.
If it is 0 μm or less, the process proceeds to step S9; otherwise, the process proceeds to step S10. In step S9, the display device 7
A focus signal is output to turn on the focus mark 7b. On the other hand, in step S10, a front focus signal or a rear focus signal is output to the display device 7 according to the sign of the final defocus amount, and the front focus mark 7c or the rear focus mark 7a is lit. In step S11, the switch 24 and the lens CP
Based on the information from U21, it is determined whether or not the mode is the MF mode as described above.
Returning to step 1, otherwise proceed to step S12. In step S12, the lens driving amount and the driving direction are calculated based on the final defocus amount, and the subsequent step S13
Control the lens drive circuit 22 to move the taking lens 10.

As described above, when the MF mode is set or when the mounting of the AF lens is not detected, the smallest one of the plurality of defocus amounts detected in the plurality of focus detection areas is determined as the final defocus amount. Since the focus amount is determined, the focus can be detected for the main subject being focused when adjusting the focus of the shooting lens manually while looking at the subject image on the viewfinder screen. The focus adjustment state of the photographing lens for the main subject intended by the photographer is displayed.

The number and arrangement of the focus detection areas are not limited to those in the above embodiment. Further, in the above embodiment, the focus is determined when the final defocus amount is 50 μm or less, but the focus determination criterion is not limited to the above embodiment.

In the configuration of the above embodiment, the focus detecting optical system 15, the photoelectric converter 16, and the CPU 20 function as focus detecting means, the AF / MF mode switching button and the switch 24 function as setting means, and the lens CPU 21 functions as lens detecting means. The CPU 20 constitutes a defocus amount determining means and a determining means, and the display 7 constitutes a notifying means.

[0021]

As described above, according to the present invention, when the manual focus adjustment mode is set or when the mounting of the autofocus lens is not detected,
The smallest one of the plurality of defocus amounts is determined as the final defocus amount for displaying the focused state,
When the mounting of the autofocus lens is detected and the manual focus adjustment mode is not set, the final defocus amount is determined from a plurality of defocus amounts by a method different from that when the manual focus adjustment mode is set. Therefore, in both the manual focus adjustment mode and the auto focus mode, the defocus amount that accurately represents the focus adjustment state of the taking lens with respect to the main subject intended by the photographer can be selected. The focus adjustment state of the taking lens with respect to the intended main subject can be accurately displayed.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims.

FIG. 2 is a block diagram showing a configuration of one embodiment.

FIG. 3 is a diagram showing a focus detection optical system and a photoelectric converter.

FIG. 4 is a diagram showing an element arrangement of a photoelectric converter.

FIG. 5 is a flowchart showing an example of a control program of the microcomputer.

FIG. 6 is a flowchart showing an example of a control program of the microcomputer.

FIG. 7 is a view showing a subject image on a finder screen and a display device.

[Explanation of symbols]

 Reference Signs List 1 shooting screen 6a-6d focus detection area 7 display device 7a rear focus mark 7b focus mark 7c front focus mark 10 shooting lens 12 finder screen 15 focus detection optical system 16 photoelectric converter 16a, 16b light receiving unit 17 condenser lens 18a, 18b Re-imaging lens 20 Microcomputer (CPU) 21 Lens CPU 22 Lens drive circuit 23 Lens motor 24 Switch 100 Focus detection unit 101 Setting unit 102 Lens detection unit 103 Defocus amount determination unit 104 Judgment unit 105 Notification unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-425 (JP, A) JP-A-1-287512 (JP, A) JP-A-4-9932 (JP, A) JP-A-5-99 5829 (JP, A) JP-A-63-193133 (JP, A) JP-A-63-256933 (JP, A) JP-A-2-74934 (JP, A) JP-A-3-212605 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/40 G03B 3/00-3/12 G03B 17/18-17/20

Claims (1)

(57) [Claims] 1. A plurality of focus detection areas are provided in a photographing screen set on a predetermined focal plane of a photographing lens equivalent to a film surface, and an image forming plane of the photographing lens and the predetermined focal plane are provided in each focus detection area. Focus detection means for detecting a defocus amount indicating a distance to the camera; setting means for setting a manual focus adjustment mode; lens detection means for detecting attachment of an autofocus lens; and manual focus adjustment mode set by the setting means. If the focus detection unit detects that the mounting of the autofocus lens is not detected, or if the lens detection unit does not detect the attachment of the autofocus lens, the smallest one of the plurality of defocus amounts detected by the focus detection unit is displayed to indicate the in-focus state. Is determined as the final defocus amount, and the lens detection means performs autofocus.
Installation of the lens is detected, and manual
If the focus adjustment mode is not set, the focus
From among a plurality of defocus amounts detected by the detection means,
Note that the final setting is different from the manual focusing mode setting.
Specific and the defocus amount determination means for determining a defocus amount, the final differential determined by the defocus amount determining means
Determining the focus of the taking lens based on the amount of focus
And determination means, the determination means determines the result of focus detection apparatus characterized by comprising an informing means for informing.