JP2986803B2 - Auto focus camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus camera having a function of automatically performing focus adjustment for driving a photographing lens to a focus position.

2. Description of the Related Art Conventionally, an autofocus camera uses an object lens (photographing lens) using a subject image formed on a predetermined focal plane of an objective lens on which a film is located, that is, a partial focus detection area at the center of the film plane. Is calculated, and the objective lens is driven based on the calculation result to create a focused state in which a sharp image of the subject is formed on the film surface.

Also, on the surface equivalent to the film surface in the viewfinder, a detection frame is provided as a mark indicating the detection area of the film surface,
By placing the subject to be photographed in the detection frame, the objective lens is focused on the intended subject.

In recent years, a plurality of focus detection areas are provided, a focus adjustment state is calculated in each focus detection area, an object satisfying a predetermined condition is selected from a plurality of calculation results, and an objective lens is driven. There is also known an apparatus that averages some of a plurality of calculation results and drives the objective lens based on the average value.

[Problems to be Solved by the Invention] By the way, it is easy to put a subject in a focus detection frame in a viewfinder, as long as the subject is still in a normal commemorative shooting mode. When the subject moves violently and the movement cannot be predicted, it is very difficult to put the subject in the focus detection frame, and the subject often comes off the detection frame.

For example, as shown in FIG.
In the state in which the object 50 is in focus and the object lens is focused on the object 50, when the object 50 suddenly moves sideways and comes out of the focus detection frame 40 as shown in FIG. The signboard as the background 60 enters the focus detection frame 40, and the objective lens is driven to the focused state of the background 60.

Therefore, every time the subject goes out of the focus detection frame, the objective lens is driven so as to focus on the background 60, so it feels very troublesome. Since the camera is at the in-focus position, it takes time to focus on the subject 50 again, and a shutter chance is often missed.

Further, if the shutter is released immediately after the subject 50 comes out of the detection frame 40, there is a problem that a photograph in which the subject 50 is out of focus due to focusing on the background 60 is taken.

Further, when performing similar shooting, in an autofocus camera provided with a plurality of focus detection areas, a background 60 enters a certain detection area, and a background 60 enters when a subject 50 enters a certain detection area. There is a possibility that a calculation result in a certain detection area may be selected.

The present invention has been made in view of such a conventional problem, and even when a subject moves and deviates from a focus detection area, an autofocus camera that can take a focused photograph without unnecessary lens driving is performed. The purpose is to provide.

Means for Solving the Problems The present invention calculates a defocus amount of an objective lens by using a pair of subject images formed on a predetermined focal plane of the objective lens by a focus detection optical system, and calculates the defocus amount. In the autofocus camera that drives the objective lens to the in-focus position obtained from and adjusts the focus, the in-focus position at which the objective lens focuses on an object that does not need to be focused is set based on a set operation. Storage means for storing and holding; if the planned driving position of the objective lens based on the defocus amount is within a predetermined range with respect to the focus position stored by the storage means, the defocus calculated at that time Command means for commanding the focus adjustment to be invalidated by the amount.

[Operation] According to the autofocus camera of the present invention having such a configuration, when photographing a subject 50 having a strong movement and an unpredictable movement as shown in FIG. Focus the objective lens in the detection frame 40,
The drive position of the objective lens based on the defocus amount at that time is stored as a set position. Next, the subject 50 is detected
Take a picture so that it is within 40. At this time the subject
If 50 goes out of focus detection frame 40 and background 60 enters,
Since the defocus amount for focusing on the background 60 is calculated, the difference between the stored set position and the expected driving position with the initial position calculated is calculated, and the objective lens may be driven near the set position. If expected, lens driving is prohibited.

Therefore, every time the subject 50 moves out of the detection frame 40, the background 60
Since the object lens is driven so as to focus on the object 50, and the object lens is stopped in a state where the object 50 is almost in focus, if the object 50 is re-entered in the detection frame 40, the object 50 is immediately focused. So you never miss a photo opportunity.

Even if the shutter is released immediately after the subject 50 comes out of the focus detection frame 40, the objective lens is not driven, so that the subject 60 is not focused on the background 60, and the subject can be focused and a focused photograph can be taken.

Further, in an autofocus camera having a plurality of focus detection areas, if the position of the objective lens focused on the background 60 is set as the initial set position, defocusing such that the background 60 enters the focus detection area 40 and focuses. Since the amount is ignored and the defocus amount for driving the objective lens is selected from other defocus amounts, the objective lens is not driven to focus on the background 60.

[Embodiment] FIG. 1 shows a first embodiment of the present invention, which is not an embodiment.

In FIG. 1, reference numeral 1 denotes an objective lens, 2 denotes a focus detection optical system, 3 denotes a pair of image sensor arrays, 4 an operation unit which takes in data of the image sensor array and performs a focus detection operation, and 5 denotes an operation unit 4. A drive control unit that drives the motor 6 based on the calculated operation result, 7 is an encoder that monitors the amount of rotation of the motor 6, 8 is a counter that counts the number of pulses output from the encoder 7 in one lens drive, and 9 is A total drive amount counting unit that counts the total number of pulses output from the encoder 7 in several lens driving operations, 10 is a reset unit that resets the count value of the total drive amount counter 9 to 0, and 11 is a total drive amount counter. A comparison unit for comparing the counted value of 9 with the calculation result of the calculation unit 4;
Is a prohibition unit for invalidating the operation of the comparison unit.

Next, the principle of focus detection in an autofocus camera will be described using a focus detection optical system shown in FIG.

In FIG. 2, the field mask 200 is located near the film surface, and the opening of the field mask 200 is a detection area. The light beam incident through the region 101 of the objective lens 1 passes through the field mask 200, the field lens 300, the aperture opening 401, and the re-imaging lens 501 to form an image on the image sensor array A. Similarly, the light beam incident through the area 102 of the objective lens 1 forms an image on the image sensor array B through the field mask 200, the field lens 300, the aperture opening 402, and the re-imaging lens 502.

A pair of subject images formed on the image sensor arrays A and B move away from each other in a so-called front focus state in which the objective lens 1 forms a sharp image of the subject before the planned focal plane, and conversely, a subject behind the planned focal plane. In the so-called back focus state, which forms a sharp image of the subject, they approach each other, and when the so-called in-focus state forms a sharp image of the subject on the predetermined focal plane, the image sensor arrays A, B
The upper subject images are relatively consistent.

Therefore, a pair of copy body images is converted to image sensor array A,
By subjecting the objective lens 1 to photoelectric conversion on B and calculating the electric signal and the subsequent arithmetic processing to determine the relative position of a pair of subject images,
In the focus adjustment state, that is, the defocus amount and the direction as the amount deviated from the in-focus state.

Next, a method of calculating the defocus amount from the outputs of the image sensor arrays A and B will be described.

As shown in FIG. 2, each of the image sensor arrays A and B is composed of a plurality of photoelectric conversion elements, and converts each photoelectric conversion output into a photoelectric conversion output as shown in FIGS. 3 (a) and 3 (b).
a1 ... an, b1 ... bn.

The correlation operation is performed while the two data strings output from the image center arrays A and B are relatively shifted by a predetermined data amount L.

 Specifically, the correlation amount C (L) is calculated by the following equation.

Here, 1 and L are integers corresponding to the shift amount of the data string, and the first term k and the last term r may be changed depending on the shift amount L.

As a result, the correlation amount C (L) shown in FIG. 3 (c) is calculated, and the focus detection optical system shown in FIG. The defocus amount is obtained by multiplying a constant determined by the system and the pitch width of the photoelectric conversion elements of the image sensor arrays A and B.

However, the correlation amount C (L) is a discrete value as shown in FIG. 3C, and the minimum unit of the detectable defocus amount is limited by the pitch width of the photoelectric conversion elements of the image sensor arrays A and B. Will be done. Therefore, a method of calculating a minimum value Cex anew by performing an interpolation operation from the discrete correlation amount C (L) and performing detailed focus detection is disclosed by the present applicant in Japanese Patent Application Laid-Open No. 60-37513.

This interpolation calculation is a method of calculating the correlation amount C1 which is the minimum value and the correlation amounts C1 and C-1 of the shift amounts on both sides thereof as shown in FIG. 3 (d), and the shift amount Fm which gives the minimum value Cex.
And the defocus amount DF are determined by the following equation.

DF−Kf × Fm Fm = L + DL / E DL = (C−1−C1) / 2 Cex = C0− | DL | E = MAX {C1−C0, C−1−C0} Equation (2) where MAX {Ca, Cb} means selecting the larger one of Ca and Cb, and Kf is determined by the focus detection optical system and the pitch width of the photoelectric conversion elements of the image sensor arrays A and B shown in FIG. Is a constant.

It is necessary to determine whether the obtained defocus amount truly indicates the defocus amount or whether the defocus amount is due to fluctuation of the correlation amount due to noise or the like. When the following condition is satisfied, the defocus amount is reliable. And

E> E1 and Cex / E> G1 (E1, G1 is a certain predetermined value) ... Condition (1) Here, E is a value depending on the contrast of the subject, and the larger the value, the higher the contrast and the higher the reliability. , And Cex / E mainly depends on the noise component, and the closer to 0, the higher the reliability.

If the condition (1) is satisfied, the defocus amount DF
Indicates the defocus amount, and when the objective lens 1 is driven by the defocus amount DF in the optical axis direction, a focused state is obtained.

By the way, as described later, as the drive control of the objective lens 1, the rotation speed of the motor 6 for driving the objective lens 1 is monitored by the encoder 7, and the encoder 7 is controlled.
Is stopped when the number of pulses output by the controller reaches a predetermined amount corresponding to the defocus amount DF. Therefore, it is necessary to convert the data amount DF into the pulse number PC of the encoder 7.

 This conversion is performed by the following equation.

PC = DF / LP Expression (3) Here, LP is the amount of movement of the objective lens 1 per unit pulse, and the value of LP differs depending on the objective lens 1 used. Here, the driving direction of the objective lens 1 is indicated by ± signs. For example, it is assumed that the value of LP is represented by minus when the front lens is driven, that is, when the objective lens 1 is driven in the film surface direction, and the value of LP is represented by plus when the objective lens 1 is driven toward the subject by the rear focus. Of course, the above processing operations are performed by the arithmetic unit 4 in FIG.

 Next, drive control of the objective lens 1 will be described.

The drive control unit 5 in FIG. 1 receives the pulse number PC calculated by the calculation unit 4, resets the count value of the counter 8 to 0, and rotates the motor 6 in the direction indicated by the sign of the pulse number PC. Each time the motor 6 rotates by a predetermined angle, the encoder 7 inputs one pulse, and the counter 8 counts the output pulses of the encoder 7. The drive control unit 5 compares the number of pulses counted by the counter 8 with the number of operation pulses PC, and stops the motor 6 when they match.

Next, the operation of the total drive amount counting section 9 in FIG. 1 will be described. The count value of the total drive amount counting section 9 is reset to 0 by reset means 10, and counts the number of pulses output from the encoder 7 during the lens drive after the reset. At this time, the lens driving direction, that is, the sign of the pulse number PC is input from the drive control unit 5, and if the sign is negative, the pulse number is added to the count value, and if the sign is positive, the pulse number is subtracted from the count value. Addition / subtraction control is performed.

The count value of the total drive amount counting unit 9 is different from that in which the count value of the counter 8 is reset to 0 every time the lens is driven. 7, the total number of pulses output, that is, the total driving amount of the objective lens 1 is counted.
Therefore, by looking at the count value of the total drive amount counting section 9, the current position of the objective lens 1 when the objective lens 1 is reset by the reset means 10, that is, in what direction and how far from the initial set position, is. I understand.

For example, after resetting, first drive 100 pulses in the plus direction and then drive 40 pulses in the minus direction.
The count value of the total drive amount counting unit 9 is -60 pulses, which means that the objective lens 1 is currently located at a position shifted by 60 pulses from the initial set position toward the subject.

Next, the operation of the comparison unit 11 will be described. The comparison unit 11 is an operation unit 4
When the objective lens 1 is driven by the pulse number PC and the count value of the total drive amount counting unit 9 and the absolute value of the difference is within a predetermined value, that is, when the objective lens 1 is driven by the calculated pulse number PC. When the position 1 becomes close to the initial set position, the drive control unit 5 sends a prohibition signal for prohibiting the drive of the objective lens 1 based on the pulse number PC calculated by the calculation unit 4.
Send to

For example, it is assumed that the count value of the total drive amount counting unit 9 is +500 pulses, the pulse number PC calculated by the calculation unit 4 is +502 pulses, and the predetermined value for determining the absolute value of the difference is 5 pulses. The count value of the total drive amount counting unit 9 is the current objective lens 1
Is located at a position shifted by 500 pulses from the set position to the film surface direction.
Instructs the objective lens 1 to be driven 502 pulses in the direction of the subject, so that when the objective lens 1 is driven based on the pulse number PC, the count value of the total drive amount counting unit 9 becomes 500−502 = −2 pulses. Becomes Therefore, the absolute value of the difference is within the predetermined value of 5 pulses, which means that the objective lens 1 is driven to the substantially initial set position.
Prohibit driving based on PC.

The operation of the comparison unit 11 is performed when the prohibition unit 12 is in the OFF state. When the prohibition unit 12 is in the ON state, the difference between the pulse number PC and the count value from the total drive amount counting unit 9 is calculated. Even when the absolute value is within a predetermined value, the drive is performed based on the pulse number PC by the drive control unit 5, and in this case, the operation is the same as that of the conventional autofocus camera.

Next, the operation of the autofocus camera of the first embodiment shown in FIG. 1 will be described.

For example, in shooting in which the movement of the subject 50 is severe and movement cannot be predicted as shown in FIG.
Is turned on, the background 60 is put in the focus detection area 40, and the objective lens 1 is focused. In this state, the reset means 10 is operated to store the position of the objective lens 1 focused on the background 60 as an initial set position.

When the storage setting of the initial set position is completed in this way, the prohibiting means 12 is returned to the OFF state, and thereafter, photographing is performed while the subject 50 is in the focus detection frame 40 as in the related art.

At this time, if the subject 50 moves unexpectedly and the focus detection frame 40
Even if the background 60 enters the background 60 and the number of pulses PC such that the objective lens 1 is focused on the background 60 is calculated by the calculation unit 4, the drive control unit 5 is controlled by the total drive amount counting unit 9 and the comparison unit 11.
The driving of the objective lens 1 by the above is prohibited.

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

In the second embodiment, a plurality of focus detection areas are formed by providing a plurality of focus detection optical systems 2 and a pair of image sensor arrays 3 described in the first embodiment, or a pair of image detection systems in the first embodiment. For example, as shown in FIG. 6, the sensor arrays A and B are divided into three blocks 1AB, 2AB, 3AB and 1BB, 2
BB, 3BB divided into each, a pair of corresponding blocks
By performing the focus detection calculation on the data of 1AB and 1BB, 2AB and 2BB, and 3AB and 3BB, as shown in FIG.
Is divided into a plurality of blocks 1B, 2B, and 3B to form a plurality of focus detection areas.

FIG. 5 is an embodiment configuration diagram showing a second embodiment of the present invention.

In FIG. 5, 1 is an objective lens, 2 is a focus detection optical system, and has the configuration shown in FIG. Reference numeral 3 denotes an image sensor array, 4 denotes a calculation unit which takes in data of the image sensor array and performs focus detection calculation for each of a plurality of focus detection areas, and 13 satisfies predetermined conditions from a plurality of calculation results calculated by the calculation unit. Or a drive control unit for driving the motor 6 based on the calculation result selected by the selection unit 13, and a motor control unit 7 for averaging some calculation results among a plurality of calculation results. An encoder for monitoring the amount of rotation of the lens, 8 is a counter for counting the number of pulses output from the encoder 7 in one lens drive, and 9 is a total drive amount for counting the total number of pulses output from the encoder 7 in several lens drives. The counting unit 10 is reset means for resetting the count value of the total drive amount counting unit 9 to 0, and the reference numeral 14 is the value counted by the total drive amount counting unit 9 and the calculation unit 4. Determination unit for comparing the calculated results, 12 the determination unit
This is a prohibition means for invalidating the operation of No. 14.

Here, the drive control unit 5, the motor 6, the encoder 7,
The counter 8, the total drive amount counting section 9, the reset means 10, and the prohibiting means 12 are almost the same as those in the first embodiment shown in FIG.

The method of forming the plurality of one focus detection areas is not particularly limited, and it is assumed that N focus detection areas are formed. As a result, the calculation unit 4 calculates at most N calculation results, that is, the number of pulses PC1, PC2,..., PCN for driving the objective lens to the in-focus position. Then, the selecting unit 13 performs a process of selecting a result satisfying a predetermined condition from a maximum of N operation results.

Here, the selection condition of the selection unit 13 may be the one that indicates the closest distance, the one that has the highest reliability (the one with the large value of E), or the like. The selecting unit 13 does not select one of the results of the plurality of calculation results, but averages the ones having similar values, and selects the one that satisfies a predetermined condition from the plurality of averaged values. You may.

Next, the operation of the determination unit 14 will be described. The determination unit 14 is the arithmetic unit 4
Are compared with the count values from the total drive amount counting unit 9 respectively. In this comparison processing, when the absolute value of the difference between the value of the arbitrary pulse number PCi (i = 1 to N) and the count value of the total drive amount counting unit 9 is within a predetermined value, that is, the objective lens 1 has the pulse number PCi. If the position of the objective lens 1 becomes close to the initial set position when is driven, the pulse number PCi is invalidated so as not to be used in the selection unit 13.

For this reason, the selection unit 13 selects a pulse number excluding the pulse number that drives the objective lens to the reset position and satisfies a predetermined condition, and drives the objective lens 1 to the initial set position. It will not be done.

The operation of the determination unit 14 is performed when the prohibiting unit 12 is in the OFF state. When the prohibiting unit 12 is in the ON state, the absolute value of the difference between the pulse number PCi and the count value from the total drive amount counting unit 9 is obtained. Is within a predetermined value, the pulse number PCi is effectively handled by the selection unit 13, and the operation is the same as that of the conventional autofocus camera.

The drive controller 5 drives the objective lens 1 based on the number of pulses selected by the selector 13.

In the first and second embodiments, if a plurality of sets of the total drive amount counting section 9 and the reset means 10 are provided, a plurality of initial reset positions can be set, and the objective lens focuses on a part other than the intended subject. Lens driving can be further reduced.

The means for storing and holding the position of the objective lens at the time of focusing on an object other than the focus adjustment target as the set position provided in the first and second embodiments is stored and held when the reset operation is performed. Is canceled, and the camera can be used as a normal autofocus camera.

In the above embodiment, the focus detection device of the phase difference detection method has been described. However, the present invention is not limited to this. For example, an active focus detection device of a triangulation method may be used. Specifically, after the focus detection by near-infrared ray projection is performed by the reset means 10, the detection result is stored and held, and the next focus detection result falls within a predetermined range near the stored focus position of the objective lens 10. The comparison unit 11 detects whether or not the focus detection signal is within a predetermined range, and controls the drive control unit 5 to prohibit the focus adjustment based on the focus detection signal.

[Effects of the Invention] As described above, according to the present invention, when a subject moves violently as in sports, the subject unexpectedly moves sideways, deviates from the focus detection frame, and the background enters. However, the objective lens is not driven so as to focus on the background, and the subject is immediately focused when the subject is again put into the focus detection frame, so that a photo opportunity is not missed.

In addition, even if the shutter is released immediately after the subject goes out of the focus detection frame, the subject is not focused on the background, so that it is possible to reliably prevent a photograph in which the subject is out of focus.

Further, according to the embodiment, in an autofocus camera provided with a plurality of focus detection areas, when a background enters one focus detection area and a subject enters another focus detection area, focus detection including the background is performed. By setting the calculation result of the area to the initial set position, there is no possibility that the calculation result of the focus detection area including the background is selected.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment showing a first embodiment of the present invention; FIG. 2 is an explanatory diagram showing a focus detection optical system used in the present invention; FIG. FIG. 4 is an explanatory diagram showing an example of a finder visual field at the time of sports photography; FIG. 5 is a diagram showing an embodiment showing a second embodiment of the present invention; FIG. 6 is a second embodiment. FIG. 7 is an explanatory diagram showing a plurality of focus detection frames provided in a viewfinder corresponding to the block division of the image sensor array; FIG. 1: Objective lens 2: Focus detection optical system 3: Image sensor array 4: Operation unit 5: Drive control unit 6: Motor 7: Encoder 8: Counter 9: Total drive amount counting unit 10: Reset means 11: Comparison unit 12: Prohibition unit 13: Selection unit 14: Judgment unit

Claims (4)

(57) [Claims] 1. A defocus amount of an objective lens is calculated by a focus detection optical system using a pair of subject images formed on a predetermined focal plane of the objective lens, and a focus position obtained from the defocus amount is calculated. In an autofocus camera that performs focus adjustment by driving the objective lens, a storage unit that stores and holds a focus position where the objective lens focuses on a subject that does not need to be focused, based on a set operation; If the planned driving position of the objective lens based on the defocus amount is within a predetermined range with respect to the in-focus position stored by the storage unit, disabling the focus adjustment based on the defocus amount calculated at that time. And an instructing means for instructing an autofocus camera. 2. The auto-focus camera according to claim 1, further comprising a prohibition unit for prohibiting a command for invalidating a focus adjustment by said command unit. 3. A focus detecting means for detecting a focus state of the objective lens and outputting a focus detection signal, and calculating a defocus amount of the objective lens based on the focus detection signal, and calculating the defocus amount from the defocus amount. In an autofocus camera having a focus adjustment driving unit that drives the objective lens at a focus position, a focus position at which the objective lens focuses on a subject not requiring focus is stored and held based on a set operation. A storage unit, wherein the focus detection signal output from the focus detection unit after storage by the storage unit drives the objective lens within a predetermined range near the in-focus position stored by the storage unit. Command means for invalidating the focus adjustment based on the focus detection signal when the focus detection signal is detected. Sukamera. 4. A focus detection means for detecting a focus state of a photographing lens for a plurality of portions of a photographing screen and outputting a focus detection signal, and determining a final focus state based on the plurality of focus detection signals. Means for calculating a defocus amount of the objective lens based on the final focus adjustment state, and driving the objective lens to a focus position determined from the defocus amount. In a focus camera, storage means for storing and holding a focus position at which the objective lens focuses on an object that does not need to be focused, based on a set operation; and a plurality of output from the focus detection means after storage and storage by the storage means Focus detection signals for driving the objective lens to focus within a predetermined range near the set position stored by the storage means. Is
An autofocus camera, comprising: a command unit that invalidates the determination unit.