JP2770450B2 - camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a camera having an automatic focus adjustment function, and more particularly, to a focus detection means for detecting a deviation of a photographic lens from an in-focus position with respect to a subject. A focus determining means for determining that the focus is obtained when the absolute value of the detection deviation by the focus detection means is equal to or smaller than a set value; and The present invention relates to a camera provided with a focus adjusting unit that moves toward a focus position by a driving amount.

[Conventional technology]

In the conventional camera, until the start of the release operation is started, the detection of the deviation from the in-focus position of the photographing lens with respect to the subject by the focus detection unit is repeatedly performed,
By always operating the focus adjustment means based on the detected deviation, the focus can be adjusted with good tracking even for a moving object, and further, the speed of the object is detected from a plurality of detected deviations, and the detection is performed. 2. Description of the Related Art There has been known an image processing apparatus that is capable of taking a photograph with little out-of-focus by performing a focus adjustment by predicting a movement of a subject using a speed.

[Problems to be solved by the invention]

However, the conventional camera described above has the following problem.

In other words, the detection of the deviation of the taking lens from the in-focus position of the photographic lens by the focus detecting means is usually performed using light from the photographic subject, and therefore, in an environment where the brightness is not sufficient, such as at dawn or at dusk or indoors. For a subject with low luminance, the accuracy of deviation detection is not high, and conversely, noise light may be mixed. In the above-described conventional camera, since the focus adjustment operation is always performed based on the detection deviation by the focus detection unit, in the case of the above-described low-luminance subject, the focus adjustment is performed due to the mixed noise light, or In some cases, focus adjustment is performed by predicting the movement of the subject using data of not so high accuracy, and as a result, the photograph may deviate from the in-focus state and may be an out-of-focus photograph. .

Furthermore, in the case where the focus adjustment is performed even after the start of the release operation in order to perform the focus adjustment with a higher tracking ability, it is necessary to detect the deviation with higher accuracy. growing.

An object of the present invention is to provide a camera capable of performing a focus adjustment on a low-luminance subject without inadvertent defocusing in view of the above situation.

[Means for solving the problem]

The camera according to the present invention is characterized in that, in a camera that performs focus adjustment after the start of the release operation and before the start of the operation of the shutter, a subject luminance detecting means for detecting the luminance of the subject, and a subject luminance detected by the subject luminance detecting means. When the brightness is equal to or less than the set luminance, the operation of the focus adjustment unit after the focus determination unit determines that the focus is achieved and the operation of the focus adjustment unit from the start of the release operation to the start of the operation of the shutter are prohibited. That is, the control means is provided.

[Action]

In other words, when the brightness of the subject is low, once focus is achieved, the movement of the taking lens due to the operation of the focus adjustment means is prohibited and the state is maintained. In this case, an unexpected focus adjustment operation is not performed, and it is possible to avoid erroneous prediction of the movement of the subject using data with not so high accuracy.

Moreover, in this type of camera, detecting the brightness of the subject is usually performed to determine the aperture and shutter speed at the time of exposure. For example, based on the detection result, the electronic flash is used at low brightness. In many cases, a display or the like is performed in order to inquire about the use of the apparatus. Therefore, if the function is used, it is only necessary to change a simple control form that prohibits the operation of the focus adjustment unit after focusing at low luminance.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram of the entire camera.

(ΜC) is a microcomputer (hereinafter, referred to as a microcomputer) which performs sequence control of the entire camera and calculation for exposure and focus detection. (LEC) is a lens circuit of a photographing lens detachably attached to a camera body (not shown), and transmits information (for example, an open F value and a focal length) unique to the photographing lens to the camera body.

(AFS) is a focus detection circuit for inputting image information obtained by forming an image of light passing through the photographing lens through a focus detection optical system (AO) and converting the information into an analog electric signal. This focus detection circuit (AFS) consists of a light receiving circuit (CCD) consisting of a CCD type light receiving element array, a monitoring light receiving element (MC) used for controlling the integration time, and a monitoring light receiving element (MC). An integration circuit (IT) that integrates and outputs the current of
A comparator (COM) that compares the output of the integration circuit (IT) with a predetermined value, an amplification circuit (AGC) that amplifies an analog signal from the light receiving circuit (CCD) according to the output from the integration circuit (IT), and the like. It is composed of

The operation of the focus detection circuit (AFS) will be briefly described. When the microcomputer (μC) outputs an integration start signal (ST), the light receiving circuit (CCD) and the integration circuit (IT) are reset, and the integration is performed. To start. When the integration output of the integration circuit (IT) becomes a predetermined value and the output of the comparator (COM) is inverted, or when the integration timer measured in the microcomputer (μC) becomes a constant value, the microcomputer (μ)
C) outputs an integration end signal (SP). As a result, the integrated output in the light receiving circuit (CCD) is sent to the transfer register, and sequentially passes through the amplifier circuit (AGC) to the microcomputer (μC).
Is forwarded to.

The microcomputer (μC) operates the focus detection circuit (AF
Based on the output from S), it is configured to calculate the deviation of the taking lens from the in-focus position with respect to the subject. That is, the focus detection means is constituted by the focus detection optical system (AO), the focus detection circuit (AFS), and the microcomputer (μC).

On the other hand, the integration circuit (IT) receives the integration end signal (SP) and holds the integration output. Amplifier circuit (AG
C) The light receiving circuit (CCD) up to 8 times according to this output
And amplifies the analog signal from the microcomputer and outputs it to the microcomputer (μC). The microcomputer (μC) has a built-in digital converter (A / D) for converting the analog data into digital data. The gain data from the amplifying circuit (AGC) is also output to the microcomputer (μC).

(LMC) is a photometric circuit which is a subject luminance detecting means for measuring the light passing through the taking lens and detecting the brightness of the subject, and converts an apex digital signal [Bv ₀ ] corresponding to the brightness of the subject into a microcomputer ( μC). (ISO)
Is a film sensitivity reading circuit that converts an apex digital signal [Sv] corresponding to the film sensitivity to a microcomputer (μC)
Output to (DISP) is a display circuit for displaying the focus state of the taking lens and the like.

(ENC) is an encoder which detects the amount of rotation of a motor for focus adjustment (hereinafter abbreviated as AF motor) (M) and sends a pulse (motor (M)) to a lens control circuit (LECON) to be described later.
Is output as a pulse) signal output for a predetermined amount of rotation. The lens control circuit (LECON) uses a microcomputer (μ
C), the signal of the motor rotation amount (number) and the motor control (speed and direction) signal are input, and based on this, the AF motor (M) is driven and the encoder (ENC)
And detects whether the AF motor (M) has rotated by a predetermined amount (motor rotation amount), and also performs stop control of the AF motor (M). The microcomputer (μC) has a counter for knowing the lens position inside, and in accordance with an internal command, counts up or down the counter according to the input of a pulse signal from the encoder (ENC). Do.

That is, the microcomputer (μC) and the lens driving circuit (LECO
N) and the AF motor (M) constitute a focus adjusting means for moving the taking lens to a focus position on the subject based on the deviation detected by the focus detecting means.

(ASL) is an auxiliary light circuit that emits auxiliary light toward the subject when focus detection is not possible and the image is dark. (CD)
An external switch switching information is sent from a memory in the card to a microcomputer (μC) by a card circuit of an IC card (not shown). For example, the switch switching information may include only one-shot AF (automatic focus adjustment state in which no lens is driven after focusing), only spot AF (focus detection state using a narrow area), auxiliary light AF (focus detection by emitting the auxiliary light) is prohibited. (BAT) is a power supply battery that supplies power to all circuits.

(SM) is operated by a main switch (not shown).
A switch that is opened and closed. (S1) is a photometric switch that is closed by pressing the release button (not shown) at the first stage. When the photometric switch (S1) is closed,
A photometric operation and an automatic focusing operation are performed. (S2)
A release switch that is closed by a second-stage pressing operation following the first-stage pressing operation on the release button,
The photographing operation is performed by closing the release switch (S2). (Ss / w) includes spot AF (a focus detection state using a narrow area only at the center of three focus detection areas described later) and wide AF (a focus detection area using all three focus detection areas described later). This is an AF area changeover switch for switching between (a focus detection state).

(E ² PROM) is built in the microcomputer (μC).
Alternatively, it is an external memory IC. This memory IC (E
² PROM) is an electrically erasable memory that retains its contents without power. The memory IC (E ² PROM) can store camera adjustment data, camera mode switching data, and the like. This makes it possible to easily set the camera specifications according to the level and needs of the photographer.

Next, the focus detection optical system (A
FIG. 2 is an exploded perspective view of the schematic configuration around O).

In FIG. 2, (TL ₁ ) and (TL ₂ ) are lenses constituting the taking lens, and both lenses (TL ₁ ) and (TL ₂ )
Are respectively provided at positions (Pz ₁ ), (Pz ₂ ), and (Pz ₁ <Pz ₂ ) from the film plane (FP), which is the planned image formation plane (hereinafter, this distance is referred to as an emission distance). ing. A field mask (FM) is provided near the planned image plane (FP). The field mask (FM) is provided with a horizontally elongated first rectangular opening (Eo) at the center thereof, while a pair of vertically elongated second rectangular openings (Eo ₁ ) and a third rectangular opening (Eo ₁ ) are provided on both sides. E
o ₂ ). The light beam from the subject passing through each of the rectangular openings (Eo), (Eo ₁ ), and (Eo ₂ ) of the field mask (FM) is converted into a separate condenser lens (Lo), (Lo ₁ ),
(Lo ₂ ) (Hereafter, the rectangular opening (E
o), (Eo ₁ ), and (Eo ₂ ), corresponding to the first condenser lens (Lo), the second condenser lens (Lo ₁ ), and the third condenser lens (Lo ₂ ). ) To be focused.

The above condenser lenses (Lo), (Lo ₁ ), (Lo ₂ )
Behind the aperture mask (AM) and the re-imaging lens plate (L)
And are arranged. The re-imaging lens plate (L) includes a pair of re-imaging lenses (L ₁ ) arranged in the center in the horizontal direction.
(L ₂ ) and one pair of re-imaging lenses (L ₃ ), (L ₄ ) and (L ₅ ),
(L ₆ ). Each of these re-imaging lenses (L ₁ )
(L ₆ ) are all composed of plano-convex lenses having the same radius of curvature. (Hereinafter, corresponding to the rectangular apertures (Eo), (Eo ₁ ), and (Eo ₂ ) of the field mask (FM), the central re-imaging lens pair (L ₁ ) and (L ₂ ) are placed in the first position. Re-imaging lens pair, re-imaging lens pairs on both sides (L ₃ ), (L ₄ ) and (L ₅ ),
(L ₆ ) is referred to as a second re-imaging lens pair and a third re-imaging lens pair, respectively. The aperture mask (AM) has aperture openings (A) at positions corresponding to the re-imaging lenses (L ₁ ) to (L ₆ ).
₁ ) to (A ₆ ) are provided. The aperture mask (AM) is disposed immediately before the re-imaging lens plate (L), and is in close contact with the flat portion of the re-imaging lens plate (L).

Behind the re-imaging lens plate (L), three
A substrate (P) including CCD line sensors (Po), (Po ₁ ), and (Po ₂ ) is provided. Center CCD line sensor (P
o) is horizontally arranged at the center of the substrate (P), and the CCD line sensors (Po ₁ ) and (Po ₂ ) on both sides are vertically arranged on both sides of the substrate (P), The installation direction of each re-imaging lens pair on the re-imaging lens plate (L) and the installation direction of each of the CCD line sensors (Po), (Po ₁ ), and (Po ₂ ) are the same. It is arranged. Each of the CCD line sensors (Po), (Po ₁ ), and (Po ₂ ) has first and second two light receiving element arrays, and is re-imaged on the CCD line sensor by the re-imaging lens pair. The two formed images are configured to be photoelectrically converted separately. (Less than,
The above CCD line sensors (Po), (Po ₁ ), (Po ₂ )
Rectangular openings (Eo), (Eo ₁ ),
(Eo ₂ ), the first CCD line sensor (Po), the second CC
These are referred to as a D line sensor (Po ₁ ) and a third CCD line sensor (Po ₂ ). The block (AFMO) enclosed by a dotted line in the figure is integrally assembled to form an AF (autofocus) sensor module. The focus detection optical system (AO) is composed of the field mask (FM), condenser lenses (Lo), (Lo ₁ ), (Lo ₂ ), aperture mask (AM), and re-imaging lens plate (L). doing.

The focus detection device (X) is configured to detect a focus position as follows using an image obtained by the focus detection optical system (AO) having the above configuration.

The optical axis (O) of the photographing lens including the principal rays (l ₃ ) and (l ₄ )
p) An off-axis distance measuring light beam from an object outside the area is incident on the field mask (FM) at a predetermined angle with respect to the optical axis (Op) and away from the optical axis (Op). passes through the second rectangular openings thereof (Eo ₁₎ Te, incident on the second condenser lens (Lo _1). This light beam for off-axis distance measurement is
It is bent toward the optical axis (Op) side by the condenser lens (Lo ₁ ) and is focused, and passes through the second aperture openings (A ₃ ) and (A ₄ ) of the aperture mask (AM) to re-image the lens plate (L). )
(L ₃ ), (L ₄ ).
The second re-imaging lens pair (L _3), the light off-axis distance measuring light beam which is incident on the (L _4), the second re-imaging lens pair (L _3), first the (L ₄₎ 2CCD line sensor (Po ₁₎
Focused on this second CCD line sensor (Po ₁ )
A pair of images are re-imaged in the vertical direction.

Similarly, the beam bundle for off-axis ranging including the principal rays (l ₅ ) and (l ₆ ) is incident on the field mask (FM) so as to be away from the optical axis (Op) at the above-mentioned predetermined angle, The third rectangular aperture (Eo ₂ ), the third condenser lens (Lo ₂ ), the third aperture openings (A ₅ ) and (A ₆ ) of the aperture mask (AM), and the third re-imaging lens pair (L) ₅ ) and (L ₆ ), the light is focused on the third CCD line sensor (Po ₂ ), and the third CCD line sensor (P
o ₂ ) Above, a pair of images are re-imaged in the vertical direction.

On the other hand, a beam bundle for off-axis distance measurement from a subject in a region including the principal rays (l ₁ ) and (l ₂ ) and including the optical axis (Op) of the photographing lens is converted into an optical axis ( Op), a first rectangular aperture (Eo), a first condenser lens (Lo), a first aperture aperture (A ₁ ) on the optical axis (Op) of the aperture mask (AM),
(A ₂ ) and the first re-imaging lens pair (L ₁ ),
After (L ₂ ), the light is focused on the first CCD line sensor (Po), and a pair of images is re-formed in the left-right direction on the first CCD line sensor (Po).

Then, the CCD line sensors (Po), (Po ₁ ), (Po
₂ ) The focal position of the taking lens (2) with respect to the subject is detected by obtaining the positions of the images forming the above three pairs of re-imaging pairs formed above.

To describe in correspondence with the finder visual field diagram shown in Figure 3, to the 1CCD line sensor (Po) on the optical axis focus detection area (IS1), the 2CCD line sensor (Po ₁₎ the right side of the optical axis out of focus The third CCD line sensor (Po ₂ ) corresponds to the detection area (IS2) and the left off-axis focus detection area (IS3). Then, three focus detection areas (IS1), (IS2), and (IS
3) (Hereinafter, when it is necessary to distinguish between them, the first island (IS1), the second island (IS2),
It is configured such that focus detection can be performed on a subject located in a third island (IS3). The rectangular frame (AF) indicated by the dotted line in the figure
Is displayed to show the photographer the photographing area for which focus detection is being performed. The display section (Dfa) shown outside the photographing screen (S) indicates the focus detection state. The display section (Dfa) lights green when in focus and turns red when focus detection is impossible. (Dfb) is an LCD for displaying a moving object when a moving object is detected.

Next, the sequence of the operation of the camera will be described with reference to the flowchart of FIG.

This flow starts when the main switch (SM) is turned on. First, in <# 400>, the metering switch (S1)
It is determined whether or not is closed, and <# 400, # 405> is looped until the photometric switch (S1) is closed. <# 40
In 5>, it is determined whether or not the main switch (SM) is opened. If the main switch (SM) is opened, the microcomputer (μC) enters the stop mode.

If it is determined in <# 400> that the photometric switch (S1) is closed, lens data specific to the taking lens is input from the lens circuit (LEC) in <# 410>. The lens data includes focal length data [f], a conversion coefficient [K] between a defocus amount and a lens driving amount, and an opening F value (Av
Value) [Avo], etc.

In <# 415>, IS0 setting data [Sv] of the film is input from the film sensitivity reading circuit (IS0), and photometric operation is performed in <# 420>, and photometric data [Bv] is input from the photometric circuit (LMC). In <# 425>, a subroutine << AF >> for performing an automatic focus adjustment operation is called, and details will be described later. <# 43
At 0>, an exposure calculation is performed to calculate a shutter speed [Tv] to be subjected to exposure control and an aperture value [Av].

Next, it is determined whether or not the release switch (S2) has been closed in <# 435>.
Then, the release permission is determined using the release permission flag described later. If the release is permitted, proceed to <# 450>
In order to compensate for the focus shift occurring during the release time lag-the time delay from the closing of the release switch (S2) to the exposure-the subroutine "LNS" for calculating the drive amount of the taking lens and controlling the lens drive is called. However, details will be described later.

If the release switch (S2) is not closed in <# 435>, or if the release is not permitted in <# 440>, it is determined in <# 445> whether the photometry switch (S1) is open. If it is open, it loops to <# 400>, while if it is closed, it loops to the next photometry and ranging in <# 410>.

On the other hand, after performing focus compensation in <# 450>, <# 4
A subroutine << exposure control >> for performing exposure control based on the shutter speed [Tv] and the aperture value [Av] obtained in <30> is called in <# 455>, the details of which will be described later. afterwards,
At <# 460>, a film winding operation for one frame is performed, and at <# 465>, it is determined whether or not the photometry switch (S1) is in an open state. If the photometry switch (S1) is open, the process loops to <# 400>.

FIG. 5 shows a subroutine << A called at <# 425>.
F >> shows a schematic flow.

When this subroutine is called, first, <# 50
In <0>, integration by the light receiving circuit (CCD) of the focus detection circuit (AFS) is performed, and in <# 502>, the pixel data is AD-converted and input. Using this pixel data, the amount of defocus (the amount of defocus) is determined in <# 504>. In <# 502>, card information from the card circuit (CD) is also input, and continuous AF (automatic focus adjustment state in which the lens is driven even after focusing) or one-shot AF is performed according to the card information.
It can also be seen that (automatic focus adjustment state in which lens driving is not performed after focusing) has been set. That is, a forced one-shot flag or a continuous flag for forcibly performing one-shot AF (hereinafter, referred to as a card one-shot) is sent from the IC card.

In <# 506>, the <moving object mode> is determined. As will be described later, the moving object mode flag is set when it is determined that the subject is a moving object. If the subject is a moving object based on the determination of the flag, the flow branches to the moving object processing flow from <# 544>. In the first loop distance measurement,
Since it cannot be determined whether or not the subject is a moving object, the process always proceeds to <# 508>. Here, it is determined whether or not continuous AF is performed. Whether continuous AF was set forcibly by the card information from the IC card entered in <# 502>
Alternatively, it is either because of a continuous flag set through <# 552> to be described later.

Subsequently, in <# 510>, it is determined whether or not the image is in focus by using an after-focus flag described later. This is <# 524> after focusing
This is for branching to the flow of the moving object determination from. <#
In 512>, it is determined whether the lens is being driven. If the next focus determination and moving object determination are performed while the lens is being driven, the accuracy is poor. In <# 514>, it is determined whether or not the taking lens is in the focusing zone. If it is within the focusing zone, set the in-focus flag (used in <# 510>) with <# 520>, and display the in-focus display (green display on the display unit (Dfa) shown in FIG. 3) with <# 522>. At the same time, a release permission flag (used in FIG. 4 <# 440>) is set.

On the other hand, if it is not within the focusing zone in <# 514>, <# 51
In 6>, it is determined whether or not the lens has been driven three times or more. If it is three or more, the moving object determination is performed using the past three defocus amounts in <# 518>. If it is determined in <# 518> that the object is not a moving object, and if it is determined in <# 516> that it has not been driven three or more times, the lens for focus adjustment is driven in <# 540> and the main routine is executed. And return to the next <#
Loop to distance measurement from 500>.

If it is determined in <# 510> that the post-focus flag is set, the process proceeds to <# 524>, and it is determined whether the distance measurement has been repeated four times. It returns to the main routine and loops to the next distance measurement from <# 500>.

When the four distance measurements are completed, the average of the four defocus amounts obtained as the results of the four distance measurements is obtained in <# 526> to obtain an average defocus amount [DFx]. Then, in <# 528>, it is determined whether or not the subject is moving away from the past two average defocus amounts [DFx]. If so, the process proceeds to <# 542> to set the AF lock flag. . In the first loop, two average defocus amounts [DFx]
Since there is no data for, use the same value.

If it is not far from the subject in <# 528>, <# 5
At 30>, it is determined whether or not the average defocus amount [DFx] is four or more. This is because, in the moving object determination of the next <# 532>, the determination is performed only when the four average defocus amounts [DFx] are aligned. If the four average defocus amounts [DFx] are not aligned, the process returns to the main routine and loops to the next distance measurement from <# 500>.

If the average defocus amount [DFx] is four, <# 532>
Then, the moving object determination is performed using the four average defocus amounts [DFx]. If it is determined in <# 532> that it is a moving object,
The process proceeds to <# 534>, and also proceeds to <# 534> when it is determined that the object is a moving object in <# 518>.

In other words, there are two ways to determine the subject as a moving object. If the moving speed of the subject is relatively fast, the determination is made in <# 518>. On the other hand, if the moving speed of the subject is relatively slow, <# 532>. In the determination in <>, it is determined that each is a moving object, and <# 5
34>. Hereinafter, these are referred to as “moving object determination type.
I "," moving object determination type II ". If it is determined that the object is a moving object, the moving object mode flag (used in <# 506>) is set in <# 534>, and the moving object correction is calculated in <# 536>. To calculate the lens drive amount by adding the predicted amount of defocus generated due to the moving object to the normal defocus amount.

Thereafter, the moving object is displayed in <# 538> (LCD (Df shown in FIG. 3)
b) is displayed), and the lens is driven in <# 540>. Hereinafter, the operation mode in which the above-described moving object correction and lens driving are performed is referred to as “moving object mode”.

After entering the <moving object mode>, the lens drive is performed, the process returns to the main routine, and loops back to <# 500>. This time, the process proceeds from <# 506> to <# 544> to calculate the moving object correction. However, the moving object correction calculation in <# 544> is different from the moving object correction calculation for driving the lens in <# 536>. In <# 536>, the correction is performed with the target of terminating the next distance measurement. On the other hand, correction is performed with the aim of ending the current distance measurement.

In <# 546>, the in-focus state is determined based on the corrected value. If the in-focus state is achieved, in-focus display and release permission are performed in <# 548>. Subsequently, in <# 550>, it is determined whether or not the direction of movement of the subject has been reversed during the <moving object mode>. If so, set the continuous flag in <# 552> and set it to <Continuous Mode>, then set <# 554>
Use to clear the motion mode.

In other words, if the correction is made in spite of the fact that the moving direction of the subject is reversed, there is a time delay due to the integration time of the CCD line sensor when detecting the movement of the subject, and the delay in the moving body correction itself is delayed. Because it occurs, it may be corrected in the opposite direction to the front and back movement of the moving object, and if the subject moves randomly back and forth, simple continuous AF will follow better It is.

FIG. 6 shows “moving object judgment type I” and “moving object judgment type II”.
FIG. A relatively fast type of subject, that is, [approximately 1.3 mm /
s], a subject having a speed higher than that can be detected as “moving object determination type I”.

The lens is driven by the first and second distance measurement <A> and <B>, and the moving object detection is started after the focus confirmation distance measurement <C>. The reason for this is
In the distance measurement of <A> and <B>, when the backlash of the lens drive is included, when the distance from the in-focus position is large and the accuracy of focus detection is low, the defocus amount and the lens drive amount Because of the error of the conversion coefficient [K] of
This is because, in the distance measurement of <B>, there are many cases where the user has not yet entered the focusing zone. If the subject is in a stationary state, it should be in focus in the distance measurement of <C> with few errors as described above, but it is not in focus even in the distance measurement <C>. It is nothing but that. Therefore, after the lens is driven based on the result of the distance measurement of <C>, if the distance measurement of <D> is out of focus and the distance measurement of <E> is also out of focus, the camera enters the "moving object mode" for the first time. . Then, moving object correction is performed using the detected defocus amounts obtained by the three distance measurements <C>, <D>, and <E>. That is, <C>
The moving body speed is calculated by averaging the two speeds, that is, the speed calculation using the detected defocus amount by <D> and <D> and the speed calculation using the detected defocus amount by <D> and <E>.

Until the distance measurement of <C>, the focusing zone is a narrow zone of [80 μm]. This is based on the assumption that the subject is in a stationary state, and the size is such that the focus is guaranteed within this zone. Once in this zone, subsequent lens drive is not required. After the distance measurement of <D>, the focusing zone is changed to [20
0 μm]. This is based on the assumption that a moving subject is moving. In the lens driving cycle based on the result of one distance measurement, a subject that moves [200 μm] or more is determined by “moving object measurement type I” and the operation mode is set to “ It switches to "Moving body mode".

When the focusing is performed on the [200 μm] focusing zone, the moving object detection shifts to “moving object detection type II” thereafter. Further, if an interruption due to the closing of the release switch (S2) is input before shifting to the "moving object detection type II", the driving of the photographing lens during the release (FIG. 4 <#
450〉). Further, when focusing is achieved in the distance measurement of <C>, the moving object is detected as “moving object detection type II”.

In the “moving object detection type II”, after focusing is achieved by the confirmation distance measurement <C>, the distance measurement is repeated four times continuously with the taking lens stopped. As shown in FIG.
1>, <D2>, <D3>, <D4> are continuously measured four times, and the defocus amount obtained by each distance measurement is averaged to obtain an average defocus amount [DFx]. Repeat distance measurement four times. And <E1> to <E4>, <F1> to <F4>, <G
When the average defocus amount [DFx] is obtained in each of the four distance measurements 1> to <G4>, the moving object is determined using the four average defocus amounts [DFx]. The speed of a subject that can be detected by the “moving object detection type II” is a speed of [0.25 mm / s] or more in terms of a film surface. If the subject is detected as a moving object in the “moving object detection type II”, the operation mode is set to the “moving object mode”, and the moving object correction and the moving object display are performed.

FIGS. 7 and 8 specifically show the flow of moving object detection by "moving object detection type I" and "moving object detection type II". According to the flowchart of FIG. 5, <#
516> and <# 518> are based on "moving object detection type I", and <# 524> to <# 532> are based on "moving object detection type II".

In the "moving object detection type I" shown in FIG.
0>, it is determined whether or not [LCNT] is “3” or more. [LCNT] is a drive counter that counts how many times the lens drive of <# 540> has been performed by the number of lens drives. By clearing this drive counter when the photometric switch (S1) is closed,
This drive counter is counted up each time <# 750> is passed, and is used as a counter for starting moving object determination. The drive counter is determined in <# 710>, and if the lens has been driven for the third time or more, the object speed is obtained in <# 715> (distance measurement of <C> and <D> in FIG. 6). continue,
If the drive counter is "3" in <# 720>, then go to <# 750>. If the drive counter is "4" in <# 720> (the ranging of <D> and <E> in FIG. 6), the moving object determination is performed.

Subsequently, each condition for moving body determination is checked. That is, in <# 725>, it is determined that the camera is not in the <auxiliary light AF mode> using the auxiliary light circuit (ASL). In <# 730>, it is determined that the subject is not dark. This is a focus detection circuit (AF
If the gain of the amplifier circuit (AGC) in S) is less than four times, it is determined that the image is not dark. In <# 735>, it is determined that the subject magnification is not high. This is because if the magnification is high, the variation in the distance measurement is large and the detection error is large.
In <# 745>, the object speed detected in <# 715> is the last two times (<C> and <D> in FIG. 6).
Is determined in the same direction as that obtained from the result of the distance measurement of <D> and <E>. When the above-described conditions are satisfied, <# 74
In 5>, the past two subject speeds are averaged to obtain subject speeds to be used in <# 534> and below.

Here, there is another condition that the moving object determination based on the “moving object determination type I” does not enter the focusing zone. However, a detailed flow of the focusing zone determination performed in <# 514> Will be described with reference to FIG.

In this flow, first, the drive counter is checked in <# 910>, and if it is "3" or more, the focusing zone is set to [200 μm] in <# 920>. > To set the focusing zone to [80 μm] (<A> in FIG. 6,
[80 μm] for <B>, <C> distance measurement, [200 μm] for <D>, <E> distance measurement). Therefore, in the case of continuous AF, the focusing zone is usually [200 μm]. Then, in <# 940>, the defocus amount [DF], which is the result of distance measurement, is compared with the focusing zone set in <# 920> or <# 930>. If out of focus, proceed to <# 516>.

FIG. 8 shows “moving object determination type II”. First, the defocus amount [DF] by closing the photometric switch (S1)
It is assumed that the sum memory [DF (sum)] is cleared.
Then, as a result of the determination of <# 510>, when the flow after focusing (<# 524>-) is entered, the defocus amounts [DF (now)] obtained by the current distance measurement in <# 800> and [ DF (sum)] and save to [DF (sum)]. In <# 805>, it is determined whether four distance measurements have been performed consecutively. If four distance measurements have not been performed, the process proceeds to <# 807> and the first determination counter [m] is counted. And returns to the main routine (<# 590>).

Next, in <# 810>, a second determination counter [l] for determining how many times the four consecutive distance measurements have been performed is counted up. Note that these two counters [l] and [m]
It is assumed that the photometry switch (S1) has been cleared when it is closed. In <# 815>, only the first determination counter [m] is cleared.

In <# 820>, the sum of the four defocus amounts [DF
(Sum)] divided by 4 and the average defocus amount [DF
(Flat)]. In <# 825>, it will be described later whether or not the first value after focusing of the average defocus amount [DF (flat)] (hereinafter referred to as a base defocus amount) [DF ₀ ] is stored. The determination is made using the memory flag. If the base defocus amount [DF ₀ ] exists in the memory, the process proceeds to <# 840>, and if not, the first average defocus amount [DF (flat)] is changed to the base defocus amount [DF ₀ ] in <# 830>. ], And a memory flag (used in <# 825>) is set in <# 835>.

In <# 840>, as well as store the average defocus amount obtained in <# 820> [DF (flat) in the memory [DF _4], 4 a memory _{[DF 4], [DF 3} ], [DF 2 ], [DF ₁ ]
Are sequentially shifted. Therefore, the latest average defocus amount [DF (flat)] is always stored in the memory [DF ₄ ].

In <# 845>, <# 850>, and <# 855>, a determination is made to escape from the moving object determination state and lock the AF. First, <#
845>, it is determined that the subject is dark, that is, when the gain of the amplification circuit (AGC) of the focus detection circuit (AFS) is determined to be four times or eight times, and the distance is measured by <# 850>. When the calculation result is a magnification larger than the magnification [1/15] at which the variation starts, the latest average defocus amount [DF ₄ ] and the base defocus amount [DF ₀ ] are further compared in <# 855>. If the distance changes by more than [300 μm], the AF lock flag is set in <# 865> and the process returns to the main routine (<# 590>).

If the AF lock flag is not set, <# 86
0>, if it is determined that the latest average defocus amount [DF ₄ ] has moved by [400 μm] or more toward the approaching object, the subsequent moving object determination flow is not performed, and the subject speed [V] is determined in <# 890>.
Is set to [0.25 mm / s], which is the minimum speed for maintaining the “moving object mode”, and proceed to <# 534>.

On the other hand, in other cases <# 864> and <# 866>, the focal length of the photographing lens is determined, and the moving object determination level from <# 875> is switched. If the focal length [f] is determined to be smaller than [50 mm] in <# 864>, the determination level [Cn] is set to [100 μm] in <# 867>, and the focal length [f] is set to [100m] in <# 866>. 200mm], it is determined that <# 86
If it is determined in 8> that the determination level [Cn] exceeds [150 μm] and the focal length [f] exceeds [200 mm], then <# 869>
To set the judgment level [Cn] to [200 μm]. This determination level [Cn] is determined by the average defocus amount [DF
(Flat)] to determine the difference between the two values.

Note that the switching of the moving object determination level [Cn] executed in <# 864> to <# 869> can be performed by another method. An example is shown in FIG. In this example, the switching of the moving object determination level [Cn] is performed based on the product [f · β] of the focal length [f] corresponding to the defocus amount on the film and the imaging magnification [β]. .

That is, as a result of the determination in <# 864 '> and <# 866'>,
If the product [f · β] is smaller than “5”, the moving object determination level [Cn] is set to [100 μm] <# 867 ′>, and if the product [f · β] is equal to or larger than “5” and smaller than “20”. Moving object judgment level [C
n] to [150 μm] <# 868 '> and product [f · β] is “20”
If so, the moving object determination level [Cn] is set to [200 μm] <# 869 ′>, and then the process proceeds to <# 870>.

In <# 870>, it is determined how many times four consecutive distance measurements have been performed, that is, whether the average defocus amount [DF (flat)] obtained for each four consecutive distance measurements has become four. Then 4
If it is more than one, the moving object determination from <# 875> is performed. The moving object determination is with that are met both the three conditions and [DF ₃ -DF ₁ ≧ Cn] and [DF ₄ -DF ₂ ≧ Cn] and _{[DF 4 -DF 1 ≧ 1.5 ·} Cn] body Is determined. Here, the reason why the judgment level is [1.5 · Cn] with respect to the last condition is that the span is 1.5 times that in the other cases.

Next, in <# 895>, two average defocus amounts [D
The subject speed [V ₁ ] is obtained using F ₃ ], [DF ₁ ] and the time between these two distance measurements, and similarly in <# 897>, the two average defocus amounts [DF ₄ ], [DF ₄ ], [DF ₄ ] DF ₂ ] and the time between the two distance measurements are used to determine the subject speed [V ₂ ]. <# 899> These two subject speeds [V ₁ ],
After performing an average calculation of [V ₂ ] (V = (V ₁ + V ₂ ) / 2) to obtain an average subject speed [V], the process proceeds to <# 534>.

Hereinafter, in the moving object correction, the average subject speed [V]
Is used to predict the defocus amount at the end of the next distance measurement, the lens drive amount with the added defocus amount is calculated, and the focus adjustment operation is repeated. When focus is achieved, a release operation is performed. In the release operation, the release switch (S2) may be closed after focusing, or the release switch (S2) may be closed before focusing. Exposure control is performed by closing the release switch (S2). During the exposure control, light is prevented from entering the focus detection optical system (AO).

Explaining the moving object correction with reference to FIG. 10, the light beam that has passed through the taking lens (TL) that forms the light beam from the subject on the film (F) is reflected by the finder optical system (FI). Anti-transmission main mirror (MM),
When the light reaches the focus detection optical system (AO) through the total reflection sub-mirror (SM), the light is reflected to other parts when the mirror-up starts under the exposure control. At this time, if the subject is a moving object, a focus shift occurs during the mirror-up. In order to correct the focus shift during the release time lag (hereinafter, this operation is referred to as focus compensation), the shortage of the moving amount of the photographing lens during the release time lag is determined by driving the lens during the mirror up (hereinafter, this is referred to as mirror (Referred to as driving during up). In the figure, the focus shift of the moving distance (DF) of the subject is corrected by the above-described mirror-up drive.

FIGS. 11 to 13 show driving during mirror-up for focus compensation. The horizontal axis is time, and the vertical axis is an axis related to the position of the image plane.

FIG. 11 shows the case of “moving object determination type II”, where <X> indicates integration timing, and <Y> indicates calculation timing.
The curve (O) shows the movement of the subject, and the straight line (L) shows the movement of the taking lens. The speed of the subject shown in FIG. 11 is quite slow, and also includes a subject that has started moving from a stopped state.

Focusing is achieved as a result of distance measurement <C>, and the subject is determined to be a moving object by the following four consecutive distance measurements <D>, <E>, <F>, and <G>, and the timing of <T> To enter "Moving mode". When entering the “moving object mode”, each computation end time <t
_{11>, <t 12>,} <t 13>, for controlling the movement of the taking lens such that the defocus amount is "0" in <t _14>. Then, for example, when the timing and <t _13> timing and contains the interruption by closing the release switch (S2) between the <t _14>, the mirror-up begins with the following focusing timing <t _14>. Then, the defocus amount deviating during the mirror-up is corrected by the drive during the mirror-up, and at the exposure timing <S>, the photographing lens is moved so that the defocus amount becomes “0”.

FIG. 12 shows the case of “moving object determination type I”, in which the distance measuring switch (S1) and the release switch (S2) are closed from the beginning. Release switch (S2)
Is the same operation as shown in the figure, no matter what timing occurs until the ranging of <F> starts. In the case of “moving object determination type I”, a subject with a high speed
In <E>, focusing is not achieved. Therefore, as described in FIG. 6, the camera enters the <moving object mode> at the timing of <T> after the lens is driven four times, focuses on the distance measurement of <F>, and performs the release operation. Also in this case, the drive during mirror up is performed, and the photographing lens is moved so that the defocus amount becomes “0” at the exposure timing <S>.

FIG. 13 shows a case where the same subject as in FIG. 12 is brought into focus by the distance measurement of <D> at which the focus zone is expanded. In this case, the player does not enter the “moving object mode”. However, considering the range of [200 μm] of the expanded focusing zone, a deviation of at least [200 μm] may occur at the time of exposure. Therefore, in order to compensate for this defocus, <D>
The defocus amount (defocus amount up to P) obtained by the distance measurement is corrected by driving during mirror-up.

With this method, even if the subject is not in the “moving object mode”, it is possible to prevent the shutter from being released due to out of focus without missing a photo opportunity. In other words, the camera is released with the focus zone expanded,
Defocusing that may occur due to the widening of the focusing zone is reduced by driving the lens during mirror up.

Table 1 on the next page summarizes this mirror-up driving.

Driving is not always performed during the mirror-up operation, but is performed depending on the automatic focus adjustment mode.

If you want to fix the focusing with the intention of the photographer who shakes the camera (<# 855>), if the accuracy of moving object detection seems to be low like when the subject is dark or the magnification is large (<# 845>) , <# 850>), and in the case of a slow moving subject that does not require the <moving object mode>(<#855>), the AF lock is applied. Do not drive while the mirror is up since driving while the mirror is up during this AF lock will result in a rather bad picture.

On the other hand, a moving object approaching or a fast moving object enters the <moving object mode> as described above, so that the driving is performed during the mirror-up, and the calculation of the moving object correction is performed so that focus is achieved at the time of exposure. However, since the mirror-up time is a finite time of [about 70 ms], the driving amount during the mirror-up is limited. The drive during this [70 ms] can be performed while braking because the photographing lens must be stopped during actual exposure, so the lens drive is less than the normal full drive. Is [40 pulses] as the pulse count. This value indicates that if the taking lens has a longer focal length than the standard lens [50 / 1.7], the lens movement will be more than [200 µm], so even if the taking lens is stopped at the end of the focusing zone [200 µm] Only the value can be driven by the lens.

If the required lens drive amount exceeds this [40 pulses], the mirror-up start is delayed by [40 ms], and the lens is driven during this time. The drive amount during lens drive before this release is also restricted so that the release time lag is not lengthened (increase only [40ms]), and unlike the mirror up drive, full drive is possible, so the drive amount To [70
Pulses], and the lens can be driven for a total of [110 pulses]. Thus, a lens movement amount of [2000 μm] can be secured when the conversion coefficient [K] of the defocus amount and the lens driving amount is small, and a lens movement amount of about [100 μm] is obtained even when the front-back conversion coefficient [K] is large. Since it can be secured, it can be said that it is a sufficient value for focus correction.

Next, in the case of the non-moving object mode, in this mode, if the release switch (S2) is closed before focusing and the subject has a considerably slow moving speed, the "moving object mode" The release operation can be performed immediately before entering (see FIG. 13). In this case and in the case of the continuous AF, the drive during the mirror up is performed without performing the moving object correction (not necessary in the method of the present embodiment). The drive amount at this time is calculated from the result of the distance measurement just before the mirror up. On the other hand, in the case of a stationary subject or a subject with a slow moving speed, the moving object determination is repeated after focusing.
If an interrupt due to the closing of the release switch (S2) occurs during this time, the drive is performed during mirror up without moving object correction. At this time, it cannot be determined whether the photographer is trying to take a still subject or a subject with a slow moving speed. For example, if you want to lock the AF, if you drive while the mirror is up, you will get a picture contrary to your intention.

Therefore, if the subject is in the focusing zone, drive during mirror up is not performed.If the camera is shaken, drive during mirror up is not performed.If the subject is in focus, the moving speed is slow. So, assuming that, move the shooting lens a little while driving the mirror up 3
As a control method that satisfies the two phenomena, a method of performing driving during mirror-up only when the defocus amount is [70 to 200 μm] is adopted. That is, if the defocus amount is [70
μm] or less, the camera is in the focusing zone. If the defocus amount is [200 μm] or more, the camera is shaken. If the defocus amount is [70 to 200 μm], it is determined that the subject has moved. is there.

Next, the drive amount will be described with reference to FIG.

Since focusing was performed in the distance measurement of <C>, the accuracy of the distance measurement of <D>, which is averaged, is better in consideration of variations in distance measurement. Therefore, the drive amount is determined based on the average defocus amount in the mirror-up drive during the moving object determination. First, assuming a moving subject << Moving object mode >>
If the release switch (S2) is closed before entering, the defocus amount obtained from the latest distance measurement result (in FIG. 14, the defocus amount is obtained from the <I> distance measurement result). It is preferable to drive during mirror up using (average defocus amount) [DFi] (line (i) in FIG. 14). Also, assuming a still subject, the point of focus is visible in the viewfinder, so the defocus amount obtained from the distance measurement result immediately after focusing (from the result of the <D> distance measurement in FIG. 14) The calculated average defocus amount) [DF
It is preferable to drive during mirror up using d] (line (iii) in FIG. 14). Furthermore, if it is assumed that the camera is slightly shaken with the AF lock, (<# 85
5) The amount of defocus determined from the result of distance measurement after about [0.8 seconds] after confirming the focus after confirming the focus (in Fig. 14, the distance measurement of <G> It is preferable to drive during mirror up using the average defocus amount [DFg] obtained from the result (line (ii) in FIG. 14).

Note that the word "premise" here means a camera that emphasizes it. In other words, it is possible to set in advance which of the distance measurement results should be used during the mirror-up operation in accordance with the assumed user of the camera.

For more fine-grained control, it is necessary to switch which mirror is used during mirror-up by using the defocus amount obtained from which distance measurement result according to the time from focusing to closing of the release switch (S2). preferable. The time to shake the camera after focusing as mentioned earlier is [0.
8 seconds] to [1 second], so that the release switch is turned on at the timing of <t ₄₁ > in FIG. 14 until the distance measurement of <G> performed at the timing 0.8 seconds after focusing. When an interruption due to the closing of (S2) occurs, the mirror is driven up using the average defocus amount [DFe] obtained from the latest <E> distance measurement result at that time, and after focusing, After the distance measurement of <G> performed at the timing of [0.8 seconds], if an interrupt by closing the release switch (S2) is received at the timing of <t ₄₂ > in FIG. 14, the measurement of <D> is performed. Average defocus amount obtained from distance results [DFd]
To drive during mirror up.

In this way, it is possible to take a picture that is in focus even when the camera is shaken for AF lock and a release operation that meets the photographer's intention is performed only after a lapse of [0.8 seconds] or more.

FIG. 15 shows a schematic flow of a subroutine << LNS >> for driving the lens during mirror up which is called in <# 450> of the main routine of FIG.

When this subroutine is called, first <# 1500>
Then, the card one-shot flag input in <# 502> of FIG. 5 is determined, and if there is a card one-shot flag, the process proceeds to <# 1538> without driving during mirror-up.
In <# 1538>, the drive pulse counter [ECNT] for driving the lens is set to "0", and the process returns to the main routine. Similarly, if <auxiliary light AF mode> in <# 1502>, the process proceeds to <# 1538> without driving while the mirror is up.

The switching between the "assistant light AF mode" and the "assist light AF mode" is performed according to the flow shown in FIG. The flow shown in FIG.
In the flow between <# 514> and <# 516> in FIG.
If the camera is out of focus in the determination at <# 514>, this flow is performed.

In this flow, first, in <# 1900>, it is determined whether or not the subject is low-confidence, that is, the reliability of the focus detection result is determined.
If the reliability is low, it is then determined in <# 1902> whether or not the subject is dark. This judgment is made by the focus detection circuit (AFS)
Is determined to be dark when the gain of the amplifier circuit (AGC) is twice. This corresponds to [-1] when corresponding to the apex digital signal [Bv]. If it is determined in <# 1902> that the subject is dark,
After setting the auxiliary light flag in 1904>, the process returns to the main routine (<# 590>). If it is determined in <# 1902> that the subject is not dark, the process returns to the main routine without setting the auxiliary light flag (<# 590>). And
If this auxiliary light flag is set at the next distance measurement, <# 50
During the integration of the step <0>, auxiliary light is projected from the auxiliary light circuit (ASL) to the subject.

Returning to FIG. 15, the description will be continued. Next, it is determined in <# 1504> whether or not the <moving object mode> is set. If it is not the <moving object mode>, then the AF lock flag is determined in <# 1506>. If the AF is locked, the process proceeds to <# 1538> without performing the drive during the mirror up as shown in Table 1.

If the AF is not locked, it is next determined in <# 1508> whether or not the continuous AF is performed. If it is determined that the continuous AF has been exited from the "moving object mode" or the continuous AF flag has been sent from the card circuit (CD), the process proceeds to <# 1514>. Set the defocus amount [DF (now)] that you have in the mirror-up drive memory [DFm]. This defocus amount [DF (now)] is the defocus amount at the time of in-focus determination before coming to this flow, and is not the average defocus amount.

If it is determined in <# 1508> that it is not continuous AF, then in <# 1510>, the base defocus amount [DF
_[0 ] is stored. If the base defocus amount [DF ₀ ] is not stored, the process also proceeds to <# 1514>. An example of this is a case where the photometry switch (S1) and the release switch (S2) are both closed before focusing (hereinafter, this is referred to as a start of focusing before focusing). Since it does not pass the determination routine, it does not have the base defocus amount [DF ₀ ]. That is, even when the pre-focus release is started, the drive is performed during the mirror-up using the defocus amount [DF (now)] at the time of focus determination. Even in the moving object determination routine, if the first average defocus amount cannot be calculated, the process also proceeds to <# 1514> in the determination of <# 1510>.

On the other hand, if there is an interruption due to the closing of the release switch (S2) during the moving object determination, the process proceeds to <# 1512>. For <# 1512>, the average defocus amount [DF (flat)]
To the drive memory [DFm] during mirror up.
This <# 1512> step depends on what kind of shooting situation the camera attaches importance,
There are various embodiments. 16 (a) to 16 (e) show some embodiments.

FIG. 16 (a) shows the case of a camera on the premise of a still subject, in which the base defocus amount [DF ₀ ] is set in the driving memory [DFm]. FIG. 16 (b) shows the case of a camera assuming a moving subject. The latest average defocus amount [DF ₄ ] is set in the drive memory [DFm].

FIG. 16 (c) shows the case of a camera assuming a portrait, and <G> when [0.8 seconds] have elapsed since focusing.
Average defocus amount [DF
G] in the drive memory [DFm]. In the case of this flow, the average defocus amount after focusing [DFG] should be set by placing the flow shown in FIG. 20 between <# 870> and <# 875> in FIG. is required. That is, if the second determination counter [l] is “4”, it means that there are four average defocus amounts [DFx],
Since it is determined that [0.8 seconds] have passed just after focusing, the average defocus amount [DF ₄ ] at this point is set as the average defocus amount [DFG] after focusing.

FIG. 16 (d) shows a case in which an all-purpose camera or a beginner's camera is assumed, and the time from focusing to the present time, that is, the closing timing of the release switch (S2) is measured in <# 1610>. [T ₃ ], it is determined in <# 1612> whether this time [t ₃ ] is less than [1 second], and [1]
If it is less than [sec], it is determined that the camera has not been shaken, and in <# 1614>, the latest average defocus amount [DF ₄ ] is set in the drive memory [DFm], while [1 sec] or more If there is, it is determined that the camera is being shaken on the way and <# 161
In 6>, the base defocus amount [DF ₀ ] is set in the driving memory [DFm]. This is for stationary subjects
This is to prevent a change in the defocus amount caused by shaking the camera from being mistaken for a movement of the subject.

In other words, for a subject having a considerably slow moving speed that is not determined as a moving object in the moving object determination flow, it is better to drive the lens using the latest average defocus amount to achieve better focusing accuracy. However, if the lens is driven using the latest average defocus amount, if the camera is shaken slowly against a stationary subject, the AF lock
Without being determined to be locked, the focus will be completely different. In order to prevent such a situation, the value set in the drive memory [DFm] is switched according to the time from when focusing is achieved until the release switch (S2) is closed.

FIG. 16 (e) is a modification of FIG. 16 (d), in which the determination of the time from focusing to the occurrence of an interrupt due to the closing of the release switch (S2) stores the average defocus amount [DFG] after focusing. It is substituted by the judgment of whether or not it has been performed. If the average defocus amount [DFG] after focusing is stored,
The base defocus amount [DF ₀ ] is set in the drive memory [DFm] in <# 1622> assuming that [0.8 seconds] or more have elapsed after focusing, while the average defocus amount [DFG] after focusing is stored. If not, for one-shot AF, or
As the focus compensation for the moving subject, the latest average defocus amount [DF ₄ ] is stored in the driving memory [DF] in <# 1620>.
m].

By the way, these are all described as different embodiments, but all the flows are provided in the program of the microcomputer (μC), and the card circuit (CD) and the memory IC (E
^{2 The} above five flows (No. 16
By switching between FIGS. (A) to (E)), one camera can be set to different operating states.

For example, when the camera is assembled, the flow shown in FIG. 16 if written, "1" at a predetermined address of the memory IC (E ² PROM) (b) are also Figure 16 if written, "2" ( What is necessary is just to make each flow shown in b) select.
Similarly, by changing the IC card, the card circuit (CD)
If an IC card with "1" written at a predetermined address is attached, the flow shown in FIG.
If a card is attached, the flow shown in FIG. 16 (b) may be selected.

Returning to FIG. 15, the description of the driving memory [DF
m] is set to any of the average defocus amounts described above, in <# 1516> and <# 1518>, mirror-up driving can be performed using lens driving amount data in the driving memory [DFm]. If a zone is determined to be impossible and the lens drive amount is [70 μm ≦ DFm <200 μm], the process proceeds to <# 1520> to perform drive during mirror up.

If it is determined in <# 1516> that the lens drive amount is less than [70 μm], the process returns to the main routine without performing the drive during mirror up. That is, it is considered that the case of coming to the step of <# 1516> is often the case of a still subject, and in this case, the drive during the mirror-up is unnecessary in the focusing zone. There is also a meaning that the feeling during the mirror-up is not deteriorated.

If it is determined in <# 1518> that the lens drive amount is equal to or more than [200 μm], the process returns to the main routine without performing the drive during mirror up similarly. In other words, if the subject is fast moving, go to <# 1540> or <# 1514>, so only the slow moving subject may pass through <# 1518>. Since the moving speed is slow, the maximum drive by the mirror up drive This is because an amount less than [200 μm] is sufficient. Conversely, if the lens drive amount exceeds [200 μm], there is a possibility that the camera is shaken but the AF lock is not achieved.

On the other hand, if the process branches to <# 1514>, it is completely unknown whether the subject is a stationary subject or a moving subject, so the process proceeds to <# 1520> on the assumption that the mirror is being driven up.

If it is determined in <# 1504> that the mode is the "moving object mode", the process proceeds to <# 1540>, where the integration of the currently held defocus amount [DF (now)] by the light receiving circuit (CCD) is started. The current time, that is, the time until the closing timing of the release switch (S2) is measured and set as [t ₁ ]. <# 154
In 2>, add [70 ms] of the mirror-up time lag to this time [t ₁ ] to obtain [t ₂ ], and in <# 1544>, the moving object speed [V] calculated during << Moving object mode >> and this By multiplying by the time [t ₂ ], an out-of-focus amount [ΔDF] due to the movement of the subject during the time lag from the integration to the exposure is obtained. ] Is referred to as a moving body correction amount).

Subsequently, in <# 1546>, the sign of the moving object speed [V] is determined. This determination means that if [V> 0], the defocus has increased in the later focusing direction.
It is determined that the subject has approached the camera.

If it is determined that the subject is approaching the camera, <#
The process proceeds to 1550>, and the moving body correction amount [ΔDF] is multiplied by a coefficient of [1/4] and added. The reason for this is that even if the subject approaches the camera at a constant speed, the change in the defocus amount on the image plane does not become a constant speed, but is a function of the reciprocal of that speed. This is to prevent the situation. Therefore, [1 + 1 / X] is considered as a correction coefficient. In consideration of the assumed moving speed of the subject, the result that the variable [x] is preferably in the range of [3 to 5] is obtained as an experimental value, and the speed of calculation by the microcomputer (μC) is taken into consideration. The variable [x] is set to [4], and the moving object correction amount [ΔDF] is multiplied by a coefficient of [1 + 1/4]. Conversely, if it is determined that the subject moves away from the camera,
Proceed to <# 1548> and set the moving object correction amount [ΔDF] to [1-1 / 4]
Multiply by

Thereafter, in <# 1552>, a K value correction is applied to the moving object correction amount [ΔDF] in consideration of an error of the conversion coefficient [K] between the defocus amount and the lens driving amount in the photographing lens. This K
More specifically, as shown in FIG. 18, the error in the conversion coefficient [K] is large because the open F-number [AV
o], the F-number [AVo] is larger than the predetermined value [J1], that is, if the taking lens is dark, the moving object correction amount [ΔDF] is multiplied by [1.2] in <# 1802>. When the value of the conversion coefficient [K] is small, the error of the conversion coefficient [K] becomes large because the lens movement amount per count for driving the lens is large. In [# 1806], the moving object correction amount [ΔDF] is set to [1.2]
By multiplying by the coefficient, the shortage of the correction amount is compensated.

After performing the K value correction, in <# 1554>, the moving object correction amount [ΔDF] is added to the current defocus amount [DF (now)] and stored in the driving memory [DFm]. 152
Go to <0>.

In <# 1520>, which respectively proceeds from <# 1524>, <# 1518>, and <# 1554>, the lens drive amount to be driven during mirror-up stored in the drive memory [DFm] is set to the shooting lens. Is multiplied by the conversion coefficient [K], and set in a drive pulse counter [ECNT] for driving the lens. <# 15
In 22>, it is checked whether or not the value of the drive pulse counter [ECNT] is larger than "40" which is the maximum number of pulses that can be driven in a limited time during mirror-up.
If it is determined that it is smaller than "40", the process proceeds to <# 1536> to start lens driving, and returns to the main routine.

On the other hand, if it is determined in <# 1522> that the value of the drive pulse counter [ECNT] is equal to or greater than “40”, the lens drive is performed before starting the exposure control, but the drive amount is also limited. Is to be attached. That is, <# 1524>
Then, it is determined whether or not the value of the drive pulse counter [ECNT] is larger than "110" which is the sum of the maximum pulse number "70" of the pre-release drive and the maximum pulse number "40" of the mirror-up drive. I do. If it is determined that it is “110” or more,
In order to perform the drive before release for the maximum [70 pulses],
<# 1528> for pre-release drive pulse counter [EECNT]
To “70”. If it is determined in <# 1524> that the value of the driving pulse counter [ECNT] is smaller than "110", the value obtained by subtracting "40" from the value of the driving pulse counter [ECNT] in <# 1526>. Drive counter before release [EECNT]
Set to.

Subsequently, the lens drive before release is started in <# 1530>, and the drive pulse counter [EECN before release] is started in <# 1532>.
Wait until T] becomes “0”. The maximum driving time of this pre-release lens driving is [about 40 ms], and the time lag is not greatly increased. In <# 1534>, the drive pulse counter [ECNT] is set to "40" so that the remaining lens drive is performed during the mirror-up, and lens drive is started in <# 1536>, and the process returns to the main routine.

After returning from the subroutine << LNS >>, the main routine calls the subroutine << exposure control >> in <# 455>. FIG. 17 shows a schematic flow of this subroutine << exposure control >>.

When this subroutine is called, first <# 1724>
To start the mirror up, and to start the aperture operation of the taking lens in <# 1726>. After that, in “Moving object mode” etc., the lens drive while the mirror is up has started.
At 1728>, the process waits until the value of the drive pulse counter [ECNT] becomes “0”. If the lens is not driven while the mirror is up, this drive pulse counter [ECNT]
Is initially set to “0”, so that <# 1728> passes immediately. Then, after completely stopping the taking lens in <# 1730>, [70ms] from the start of mirror up in <# 1732>
Wait until elapses. That is, the mirror up and the operation of the aperture stop in [70 ms]. When the mirror-up, the lens drive during the mirror-up, and the operation of the aperture are all completed, the exposure operation starts from <# 1734>.
The first curtain of the shutter curtain is run in <# 1734>, and <# 1736>
Then, the CPU waits for the exposure time obtained by the calculation of <# 430> in the main routine, and then drives the rear curtain of the shutter in <# 1738> to complete the exposure. Then, the process returns to the main routine.

The sequence of the camera operation has been described above. The microcomputer (μC) performing these operations determines focus when the absolute value of the deviation detected by the focus detection unit is equal to or smaller than a set value. The microcomputer (μC) controls the operation of the focus adjustment unit after the in-focus determination unit determines that the subject is in focus when the subject brightness detected by the subject brightness detection unit is equal to or less than the set brightness. This constitutes a focus adjustment control unit that is prohibited.

(Another embodiment)

Hereinafter, other embodiments other than those described in the previous embodiment will be listed.

<1> The reference values for various determinations performed to determine the state of the subject and the intention of the photographer can be arbitrarily changed.

<2> For stationary objects that prohibit driving during mirror-up if it is determined that the subject is dark, the shooting magnification is determined to be large, or the subject is determined to be slow and away from the camera. The focus adjustment state does not have to be set, and a focus adjustment state for a moving object that allows driving during mirror-up may be used.

<3> In the above embodiment, when it is determined that the subject is moving at a high speed, the drive amount correction in the mirror-up drive may be omitted.

<4> In the above embodiment, the taking lens is configured to be detachable from the camera body as an example, and lens information unique to the taking lens is input from a lens circuit (LEC) attached to the taking lens. In the above, the present invention can be applied to a camera in which the taking lens is fixed.

<5> In the above embodiment, a configuration in which three focus detection areas are provided has been described. Alternatively, a plurality of other focus detection areas may be provided, or one focus detection area may be provided. May be provided.

〔The invention's effect〕

As described above, the camera according to the present invention can perform the focus adjustment after the release operation is started until the start of the shutter operation, and when the brightness of the subject is low, the accuracy of the detection deviation is very high. In consideration of the fact that the noise light is not so high and the adverse effect of noise light is rather large, the focus adjustment operation after focusing and the focus adjustment operation between the start of the release operation and the start of the shutter operation are prohibited at low luminance. It is possible to prevent inadvertent departure from the in-focus state due to noise light or the like after focusing, and to perform a highly-adjustable focusing operation for a moving subject by a subsequent focusing operation after focusing. Even in such a case, it has become possible to take a photograph with less out-of-focus with respect to a subject at low luminance.

[Brief description of the drawings]

1 shows an embodiment of a camera according to the present invention, FIG. 1 is a circuit block diagram, FIG. 2 is a perspective view around a focus detection optical system, FIG. 3 is a view of the viewfinder, FIG. 5 ・
Fig. 7 to Fig. 9, Fig. 15, Fig. 16 (a) to (e)
17 to 21 are flowcharts showing the operation of the camera, FIGS. 6 (a) and 6 (b) are schematic diagrams showing the sequence of the focus detection operation, and FIGS. 10 (a) to 10 (c) are the movements of the subject. And FIG. 11 to FIG. 14 are schematic diagrams showing the relationship between the operation of the camera and the operation of the camera. (TL)… photographic lens,

──────────────────────────────────────────────────続 き Continued on the front page Examiner Toshiyasu Kimura (56) References JP-A-62-269936 (JP, A) JP-A-61-165716 (JP, A) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) G02B 7/11

Claims (1)

(57) [Claims] A focus detecting means for calculating a deviation of the photographic lens from a focus position with respect to a subject; a focus adjusting means for moving the photographic lens to a focus position based on a deviation detected by the focus detection means; Focus determining means for determining that focus has been achieved when the absolute value of the deviation detected by the focus detecting means is equal to or less than a set value; first operating means for activating the focus detecting means and focus adjusting means; A second operating means for activating the operation; and activating the focus detecting means and the focus adjusting means in response to the operation of the first operating means, and then activating the release operation when the second operating means is operated. A first control unit for operating the focus adjustment unit before the start of operation of a shutter using a detection deviation of the focus detection unit; When the brightness detecting means, it detects the subject luminance according to the subject brightness detecting means is below a predetermined value, operation of the focus adjusting means after being determined to be focused by the focusing determination unit, and the first
And a second control means for prohibiting the operation of the focus adjusting means from the start of the release operation by the control means to the start of the operation of the shutter.