JPH0277047A - Camera - Google Patents

Abstract

PURPOSE:To perform focusing without carelessly causing the deviation of focus of a low-luminance object by inhibiting the actuation of a focusing means after discriminating that focusing is attained when the detected luminance of the object is equal to or under set luminance. CONSTITUTION:A focus detection means is constituted of an optical system for detecting focus AO, a focus detection circuit AFS and a microcomputer muC and the focusing means for moving a photographic lens to a focusing position for the object based on detected deviation by the focus detection means is constituted of the microcomputer muC, a lens driving circuit LECON and an AF motor M. A photometry circuit LMC which is an object luminance detection means for detecting the brightness of the object outputs a digital signal in an apex system corresponding to the luminance of the object to the microcomputer muC. Namely, when the luminance of the object is low, the movement of the photographic lens by actuating the focusing means is inhibited and such a state is kept once focusing is attained. Thus, a photograph in which the deviation of focus of the object in the case of low luminance is little can be taken.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a camera having an automatic focus adjustment function,
Specifically, it includes a focus detection means for detecting a deviation from the in-focus position of a photographic lens for a subject, and a focus determination means for determining that focus is achieved when the absolute value of the detected deviation by the focus detection means is less than or equal to a set value. The present invention relates to a camera comprising a focus adjusting means for moving the photographing lens toward a focus position by a driving amount based on a detected deviation by the detecting means until the shutter starts operating.

[Conventional technology]

Conventionally, in the above-mentioned camera, until the release operation is started, the focus detection means repeatedly detects the deviation from the in-focus position of the photographing lens with respect to the subject, and the focus adjustment means is always operated based on the detected deviation. This allows you to adjust the focus with good tracking ability even for moving subjects, and even detect the speed of the subject from multiple detection deviations and use the detected speed to predict the subject's movement and adjust the focus. There are known devices that allow you to take photos with less out-of-focus by making adjustments.

[Problem to be solved by the invention]

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

In other words, since the focus detection means detects the deviation from the in-focus position of the photographic lens on the subject, it is usually done using light from the subject, so it is difficult to detect deviations from the focus position of the photographic lens using the light from the subject. For objects with low brightness, the deviation detection accuracy is not high, and there is a risk that noise light may be mixed in. In the conventional camera described above, the focus adjustment operation is always performed based on the detection deviation by the focus detection means, so in the case of the above-mentioned low-brightness subject, the focus adjustment may be performed due to mixed noise light, or , the focus was adjusted by predicting the movement of the subject using less accurate data, which sometimes resulted in the camera deviating from the focus state and resulting in an out-of-focus photo. .

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a camera that can adjust the focus of a low-luminance object without causing an inadvertent focus shift.

[Means to solve the problem]

The camera according to the present invention has a characteristic configuration including an object brightness detection means for detecting the brightness of the object, and when the object brightness detected by the object brightness detection means is less than a set brightness, the focus determination means determines that the object is in focus. The present invention is further provided with a focus adjustment control means for prohibiting the operation of the focus adjustment means after the focus adjustment means is activated.

[For production]

In other words, if the brightness of the subject is low, once the subject is in focus, the movement of the photographic lens by the focus adjustment means is prohibited and that state is maintained, so noise light may be mixed in after the subject is in focus. Even if you do this, an unexpected focus adjustment operation will not be performed, and it is possible to avoid incorrectly predicting the movement of the subject using data that is not very accurate.

Moreover, in this type of camera, the brightness of the subject is normally detected in order to determine the aperture and shutter speed during exposure. Since there are many displays etc. to ask the user to use the device, if you use this function,
All that is required is a simple change in the control form, such as prohibiting the operation of the focus adjustment means after focusing when the brightness is low.

〔Example〕

Hereinafter, the present invention will be described in detail based on the drawings.

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

(μC) is a microcomputer (μC) that performs sequence control of the entire camera and calculations for exposure and focus detection.
(hereinafter referred to as a microcomputer). (LEC) is a lens circuit for a photographic lens that is detachably attached to a camera body (not shown), and transmits information specific to the photographic lens (for example, open F-number, focal length, etc.) to the camera body.

(AFS) is a focus detection circuit that inputs image information obtained by forming an image of light that has passed through the photographing lens through a focus detection optical system (AO) and converts it into an analog electrical 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 light receiving element (MC) for monitoring. an integrating circuit (IT) that integrates and outputs the current, a comparator (COM) that compares the output of this integrating circuit (IT) with a predetermined value, and a light receiving circuit (CC).
It is composed of an amplifier circuit (AGC), etc., which amplifies the analog signal from D) according to the output from the integrating circuit (IT).

To briefly explain the operation of this focus detection circuit (AFS), when the microcomputer (μC) outputs an integration start signal (ST), the light receiving circuit (CCD) and the integration circuit (IT) are reset, and each integrates Start. This integrating circuit (I
When the integral output of T) becomes a predetermined value, the comparator (C
When the output of the microcomputer (μC) is inverted, or when the integral timer measured within the microcomputer (μC) reaches a constant value, the microcomputer (μC) 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 then transferred to the microcomputer (μC) via the amplifier circuit (AGC).

The microcomputer (μC) then controls this focus detection circuit (AF
Based on the output from S), the deviation from the in-focus position of the photographing lens with respect to the subject is calculated. That is, a focus detection means is constituted by a focus detection optical system (AO), a focus detection circuit (AFS), and a microcomputer (μC).

On the other hand, the integration circuit (IT) receives the integration end signal (SP).
Input and hold the integral output.

The amplifier circuit (AGC) amplifies the analog signal from the light receiving circuit (CCD) up to eight times according to this output and outputs it to the microcomputer (μC). The microcomputer (μC) has a built-in digital converter (A/D) that converts this analog data into digital data. The above amplifier circuit (
Gain data from the AGC) is also output to the microcomputer (μC).

(LMC) is a photometry circuit that measures the light passing through the photographic lens and detects the brightness of the subject. μC). (I
SO) is a film sensitivity reading circuit that outputs an apex-based digital signal [Sv] according to the film sensitivity to a microcomputer (μC). (DISP) is a display circuit that displays the focus state of the photographing lens, etc.

(ENC) is an encoder that detects the rotation amount of the focus adjustment motor (hereinafter abbreviated as AF motor) (M),
It is output as a pulse (pulse output for a predetermined amount of rotation of the motor (M)) signal to a lens control circuit (LECON), which will be described later. The lens control circuit (LECON) inputs the motor rotation amount (number) signal and motor control (speed and direction) signal from the microcomputer (μC), and based on this, drives the AF motor (M), The pulse signal from the encoder (ENC) is input, and it detects whether the AF motor (M) has rotated by a predetermined amount (motor rotation amount), and also controls the stop of the AF motor (M). ) has a counter inside to know the lens position, and the encoder (B
The counter performs a count-up or count-down operation in response to input of a pulse signal from an NC.

In other words, a microcomputer (μC) and a lens drive circuit (LEC)
ON) and the AF motor (M) constitute a focus adjustment means that moves the photographing lens to a focus position for the subject based on the detected deviation by the focus detection means.

(ASL) is an auxiliary light circuit that emits auxiliary light toward the subject when focus cannot be detected and it is dark. (CD) uses the card circuit of an IC card (not shown) to transfer switch switching information from the outside from the memory inside the card to a microcontroller (μC).
). For example, the switch switching information may include whether only one-shot AF (automatic focus adjustment state in which the lens is not driven after focusing), only spot AF (focus detection state using a narrow area), or whether auxiliary light is available. There is a prohibition of AF (focus detection by emitting the auxiliary light described above). (
DAT) is the power battery and supplies power to all circuits.

(SM) is activated by operating the main switch (not shown).
It is a switch that is opened and closed. (St) is a photometry switch that is closed by pressing the first step of the release button (not shown). Closing this photometry switch (Sl) performs photometry operation and automatic focus adjustment operation. . (SP
) is a release switch that is closed by a second pressing operation subsequent to the first pressing operation on the release button, and a photographing operation is performed by closing this release switch (SP). (Ss/w) is a spot AF (a focus detection state that uses only a narrow area in the center of the three focus detection areas described below) and a wide AF (a focus detection state that uses all of the three focus detection areas that will be described later). This is an AF area changeover switch that changes the focus detection state.

(E”FROM) is a memory IC built into the microcontroller (μC) or externally attached.
C (82FROM) is an electrically erasable memory that retains its contents even without power supply. This memory IC (B''FROM) can store camera adjustment data, camera mode switching data, and the like.

This allows you to easily set the camera specifications to match the level and needs of the photographer.

Next, the focus detection optical system (AO
) is shown in FIG. 2.

In Fig. 2, ('rt, 1) and (TLz) are the lenses that constitute the photographic lens, and both of these lenses (
TL, ), ・(TL2) are the distances (PZI) from the film plane (FP), which is the planned imaging plane, respectively.
(PZI), (PZI<PZI) (hereinafter, this distance will be referred to as the injection distance). and,
A field mask (FM) is disposed near the predetermined imaging plane (FP). This field mask (FM) is provided with a horizontally long first rectangular opening (Eo) in its center, and a pair of vertically long second rectangular openings (Eot) and a third rectangular opening (Eo) on both sides. Eot) is provided. The above field of view mask (
FM), each rectangular opening (Eo), (IEot), (
The light beams from the subject that have passed through Eo2) are sent to separate condenser lenses (Lo).

(Log), (Lot) (hereinafter, the first condenser lens (Lo) and the second condenser lens (Lo r ), third condenser lens (Lo
t). ), respectively, and are focused.

The above-mentioned condenser lens (Lo), (Log),
Behind (La2), an aperture mask (AM) and a re-imaging lens plate (L) are arranged. The reimaging lens plate (
L) is a re-imaging lens pair (
Ll)-(Ll), and pairs of re-imaging lenses (Ll), (L4) and (Ll,), (Ll) arranged vertically on both sides. The re-imaging lenses (L,) to (Ll) are all plano-convex lenses with the same radius of curvature. (Hereinafter, the field of view mask (
FM) rectangular opening (Eo), (Hot), (Eoz
), the central reimaging lens pair (Ll), (Lt
) is the first re-imaging lens pair, and both re-imaging lens pairs (La
).

(L4), (Ll), and (Ll) are respectively referred to as a second re-imaging lens pair and a third re-imaging lens pair. ) Also, the aperture mask (AM) includes each of the re-imaging lenses (Ll
) ~ (Ll), the diaphragm opening (A, ) ~
(A,) is provided. This aperture mask CAM) is disposed just in front of the re-imaging lens plate (L), and is in close contact with the flat portion of the re-imaging lens plate (L).

Further behind the re-imaging lens plate (L), there are three C
CD line sensor (Po) = (Pot) - (Pot)
A substrate (P) is provided. The central CCD line sensor (Po) is arranged horizontally in the center of the board (P), and the CCD line sensors (Pot) on both sides
, (Po2) are arranged vertically on both sides of the substrate (P), and are aligned with the installation direction of each re-imaging lens pair on the re-imaging lens plate (L) and each CCD line sensor (Po2). )
, (POI), and (PO2) are arranged in the same direction. Above CCD line sensor (Po)
, (Pot), (Pot) are the first . second 2
It has two light-receiving element rows, and is configured to separately photoelectrically convert two images re-formed on the CCD line sensor by the re-imaging lens pair. (Hereinafter, each of the above CCD line sensors (Po), (Pot), (P
O2) in the rectangular opening (Eo) of the field mask (FM).
), (Hot).

(In response to EO, the first COD line sensor (PO)
, a second COD line sensor (POl), and a third COD line sensor (Po□). ) The blocks (AFMO) surrounded by dotted lines in the figure are assembled together to form an AF (autofocus) sensor module. and field mask (FM)
- Condenser lens (Lo), (Lot).

(LO, aperture mask (AM), re-imaging lens plate (L)
This constitutes a focus detection optical system (AO).

The focus detection device (X) is configured to detect the focus position in the following manner using an image obtained by the focus detection optical system (AO) configured as described above.

A beam of light for optical axis distance measurement from a subject located in an area outside the optical axis (Op) of the photographic lens, including principal rays (j73) and (i'4), is at a predetermined angle with respect to the optical axis (Op). Optical axis (Op)
The light enters the field mask (FM) so as to move away from the field mask, passes through its second rectangular opening (Eo+), and enters the second condenser lens (Lot). This optical axis distance measuring light beam is bent and focused by the second condenser lens (Lo I) towards the optical axis (Op) side, and is focused through the second aperture aperture (A3), ( A4) to the second re-imaging lens pair (La) of the re-imaging lens plate (L)
, (L4). Second re-imaging lens pair (Ls
)=(L4) The optical axis distance measuring light beam is focused on the second CCD line sensor (Pot) by this second re-imaging lens pair (La), (L4), and A pair of images is re-imaged in the vertical direction on the 2CCD line sensor (Pa I).

Similarly, the optical axis ranging ray bundle including the chief ray (j's), C1g) enters the field mask (FM) so as to leave the optical axis (Op) at the above-described predetermined angle. Third rectangular aperture (Eoz), third condenser lens (Log)
, the third aperture aperture (As) of the aperture mask CAM).

(A,) and the third reimaging lens pair (La), (La)
The light is then focused onto the third CCD line sensor (PO2), and a pair of images is re-formed in the vertical direction on this third CCD line sensor (PO2).

On the other hand, the optical axis ranging ray flux from the subject in the area including the chief rays C1+) and (j' t) and the optical axis (Op) of the photographic lens is directed towards the optical axis (Op) of the field mask (FM). ), the first rectangular opening (Eo) on the first condenser lens (L
o), through the first aperture aperture (A1), (At) on the optical axis (Op) of the aperture mask (AM), and the first re-imaging lens pair (Lt) = (Lx), the first COD The light is focused onto the line sensor (Po), and a pair of images are re-imaged in the left and right direction on this first CCD line sensor (Po).

And the above CCD line sensor (Po), (Pop
).

(PO2) The focal position of the photographing lens (2) with respect to the subject is detected by determining the positions of the three pairs of re-imaged images formed above.

To explain in correspondence with the viewfinder field diagram shown in Fig. 3, the first CCD line sensor (Pa) is located in the on-axis focus detection area (ISI), and the second COD line sensor (Pop) is located in the on-axis focus detection area (ISI).
The third CCD is located in the optical axis focus detection area (132) on the right side.
The line sensor (Pot) is located on the left optical axis focus detection area (
IS3). Then, the shooting screen (
Three focus detection areas (ISI) shown by solid lines in the center of the screen for S).

(IS2), (133) (Hereinafter, when it is necessary to distinguish between them, the first island (ISI),
2nd island (IS2), 3rd island (IS3)
The camera is configured so that focus detection can be performed on a subject located at In the figure, a rectangular frame (AP) indicated by a dotted line is displayed to indicate to the photographer the photographing area in which focus detection is being performed. In addition, the display section shown outside the shooting screen (S) (
Dfa) indicates the focus detection state, and lights up in green when in focus, and lights up in red when focus cannot be detected. (Dfb) is an LCD for displaying a moving object when a moving object is detected.

Next, the sea fence of camera operation will be explained using the flowchart of FIG.

This flow starts when the main switch (SM) is turned on. First, press the photometry switch (3) with <#400>.
1) is closed, and the sound measurement switch (S
l) is closed <#400. #405> is looped. In <#405>, it is determined whether the main switch (SM) is opened, and if the main switch (SM) is opened, the microcomputer (μC) enters the stop mode.

If it is determined in <#400> that the photometry switch (SL) is closed, lens data unique to the photographing lens is input from the lens circuit (LEC) in <#410>.

This lens data includes focal length data [f], a conversion coefficient [K] between the amount of defocus and the amount of lens drive, and the open F value (Av value) [Avo] of the photographing lens.

In <1415>, input the film ISO setting data [Sv] from the film sensitivity reading circuit (ISO), and
20>, a photometric operation is performed and photometric data [Bv] is input from the photometric circuit (LMC). At <#425>, a subroutine (AP) for performing an automatic focus adjustment operation is called, the details of which will be described later. Perform exposure calculation in <#430> and determine the shutter speed [Tv] and aperture value [A] for which exposure should be controlled.
v] is calculated.

Next, it is determined in <#435> whether the release switch (S2) is closed, and if it is closed, <#44
0>, a release permission flag, which will be described later, is used to determine release permission. If the release is permitted, proceed to <#450> and release time lag - release switch (S2
), a subroutine (LNS) is called to calculate the drive amount of the photographic lens and control the lens drive in order to compensate for the shift in focus that occurs during the time delay between the closing of .

If the release switch (S2) is not closed in <#435>, and if the release is not permitted in <1440>, it is determined in <#445> whether the photometry switch (S1) is open, and it is opened. If the condition is 〈#400〉,
On the other hand, if the tail is closed, the next photometry of <#410>
Loop to distance measurement.

On the other hand, after performing focus compensation with <#450>,
430>, the shutter speed [Tv] and aperture value [
A subrune (exposure control) that performs exposure control based on [Av] is called at <#455>, the details of which will be described later.

After that, the film is advanced by one frame in <#460>, and it is determined in <#465> whether the photometry switch (Sl) is in the open state, and if it is, it is
>Helube.

Figure 5 shows the subroutine (
AP).

When this subroutine is called, first
Integration is performed by the light receiving circuit (CCD) of the focus detection circuit (AFS') at >, and the pixel data is AD at <#502>.
Convert and input. Using this pixel data, <1504
> to find the amount of focus shift (defocus amount). Also,
In <#502>, card information from the card circuit (CD) is also input, and Continuous AF is activated depending on the card information.
It can also be seen that (an automatic focus adjustment state in which the lens is driven even after focusing) or one-shot AF (an automatic focus adjustment state in which the lens is not driven after focusing) has been set. In other words, I
A forced one-shot flag and continuous flag (hereinafter referred to as card one-shot) for forcing one-shot AF are sent from the C card.

In <#506>, the (moving object mode) is determined, which will be explained later, but when the subject is determined to be a moving object, the moving object mode flag is set.
This is because in the subsequent loop, if the subject is a moving object by determining this flag, the process branches to the moving object processing flow from i: <#544>. In distance measurement in the first loop, it cannot be determined whether the subject is a moving object, so the process always moves to <#508>. Here, continuous A
It is determined whether it is F or not.

The I input in <#502> is continuous.
Continuous AF was forcibly set using the card information from the C card, or <#55 (described later)
2> is either due to the continuous flag being set.

Next, in <#510>, it is determined whether or not focus has been achieved using an after-focus flag, which will be described later. This is after focusing <#524
) to branch to the moving object determination flow. <
In #512>, it is determined whether the lens is being driven. Then, if the lens is being driven, the next focus determination and moving object determination will be performed with poor precision, so they are skipped. <#514>
Now, it is determined whether the photographing lens is within the in-focus zone. If it is within the focus zone, set the after-focus flag (used in <#510>) with <#520>, and <#522>
> to display the focus (line display on the display section (Dfa) shown in Fig. 3) and release permission flag (Fig. 4 <144).
0>) is set.

On the other hand, if it is not within the focus zone in <#514>, <#5
16>, determine whether the lens is driven 3 times or more, and
If the amount of defocus is greater than or equal to the amount of defocus, the moving object is determined 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 returns. return to,
Loop to the next distance measurement from <#500>.

If it is determined in <#510> that the after-focus flag is set, the process proceeds to <#524>, where it is determined whether distance measurement has been repeated four times, and if distance measurement has not been repeated four times consecutively, Return to the main routine and loop to the next distance measurement from <#500>. - After completing four distance measurements, <
#526>, the four defocus amounts that are the results of these four distance measurements are averaged to obtain an average defocus amount [DFxl]. Then, in <#528>, it is determined whether the subject is moving away using the past two average defocus amounts [DFxl, and if it is moving away, <#542>
Proceed to and set the AF floc flag.

Note that in the first loop, two average defocus amounts [D
Since there is no Fxl data, use the same value.

If the subject is not far away in <#528>, <#5
30>, it is determined whether the average defocus amount [DFxl is 4 or more. This is the following <#53
In the moving object determination of 2>, this average defocus amount [DFx
This is because the method makes a determination only when four l's are present. Then, if the average defocus amount [DFxl is not 4, the process returns to the main routine and the next <
Loop to distance measurement from #500>.

Average defocus amount [If you have 4 DFxl, <#53
2>, a moving object is determined using the four average defocus amounts [DFX]. If it is determined that the object is a moving object in <#532>, the process proceeds to <#534>. Also, if it is determined that the object is a moving object in <#51B), the process proceeds to <#534>.

In other words, there are two ways to determine that a subject is a moving object: if the subject is moving at a relatively fast speed, <1518> is used; on the other hand, if the subject is moving at a relatively slow speed, <1518> is used.
In the judgment at #532, each object was determined to be a moving object.<#
534>.

Hereinafter, these will be referred to as "moving object determination type I" and "moving object determination type ■." Then, if it is determined to be a moving object, <#
Set the moving object mode flag (used in <#506>) in <#534>, calculate the moving object correction in <#536>, and add the predicted amount of defocus that will occur due to the moving object to the normal amount of defocus. to find the lens drive amount.

After that, <#538> displays the moving object (L C shown in Figure 3).
D (display Dfb)) and drive the lens with <#540>. Hereinafter, the operation mode in which the above-mentioned moving object correction and lens driving are performed will be referred to as (moving object mode).

After entering (moving object mode) in this way, after driving the lens,
The program returns to the main routine and loops back to <1500>. This time, proceed from <#506> to <#544> to calculate the moving object correction.

However, the moving object correction calculation of this <#544> is
＞Unlike the moving object correction calculation for lens drive, ＜153
In 6>, correction is performed with the goal of completing the next distance measurement, whereas correction is performed with the goal of completing the current distance measurement.

In <#546>, focus is determined based on the corrected value, and if in focus, in-focus display and release permission are performed in <#548>. Subsequently, in <#550>, it is determined whether the direction of movement of the subject has been reversed during (moving object mode). If it is reversed, set the continuous flag (continuous mode) with <#552>, and press <
Clear the moving object mode with #554>.

In other words, if correction is performed even though the moving direction of the subject is reversed, there will be a time delay due to the integration time of the CCD line sensor when detecting the movement of the subject, and there will be a delay in the motion correction itself. This is because the correction may be made in the opposite direction for the back and forth movement of a moving object, and if the subject moves randomly back and forth, simple continuous AF has better tracking performance. .

Figure 6 shows “Moving object detection type I” and “Moving object detection type ■”
This is a sea fence diagram. A relatively fast-moving subject, i.e. approximately 1.3m in film surface terms.
[m/s] or more can be detected as "moving object determination type I."

1. Drive the lens with the second distance measurement <A> and <B>,
After focus confirmation distance measurement <C>, moving object detection begins. The reason for this is that in the distance measurement of <A> and <8>.

If there is backlash from the lens drive, or if the focus is far away from the focus position and the focus detection accuracy is low,
Also, the conversion coefficient between defocus amount and lens drive amount [
This is because due to the error in distance measurement <8>, it is often the case that the object is not within the in-focus zone. If the subject is stationary, it should be in focus with <C> distance measurement, which has fewer causes of error as described above, but the distance measurement <C>
>But the fact that it's not in focus means that the subject is a moving object. Therefore, after driving the lens based on the distance measurement result of <C>, if the distance measurement of <D> is out of focus, and the distance measurement of <E> is also out of focus, enter (moving object mode) for the first time. . And <C>, <D>, <E
＞The amount of detected defocus obtained from the three distance measurements is used to correct the moving object. In other words, the moving object speed is calculated by averaging two speeds: the speed calculation using the detected defocus amount by <C> and <D>, and the speed calculation using the detected defocus amount by <D> and <E>. That's what I do.

Until distance measurement <C>, the focusing zone is a narrow zone of [80 μm]. This is based on the assumption that the subject is stationary, and is a size that guarantees focus within this zone. Once within this zone, there is no need to drive the lens thereafter. After the distance measurement of <D>, the focusing zone is set to [2].
00 μm]. This is based on the assumption that the subject is moving, and if the subject moves more than [200 μm] in the lens driving cycle based on the result of one distance measurement, it is determined by the "moving object measurement type" and the operation mode is set to ( This means switching to moving object mode).

When the object is in focus with respect to the [200 μm] focusing zone, moving object detection thereafter shifts to detection using "moving object detection type (■)". In addition, if an interrupt occurs due to the closing of the release switch (S2) before shifting to "Moving object detection type ■", the drive for the photographing lens during release (Fig. 4<#
450> ). Furthermore, when the focus is achieved by distance measurement of <C>, the moving object is detected as "moving object detection type (■)".

In "Moving Object Detection Type ■", after focus is achieved with confirmation distance measurement <C>, distance measurement is repeated four times in a row with the photographic lens stopped. As shown in Figure 6 (b), <01>
, <02>, <03>, and <04> were carried out four times in a row, and the defocus amounts obtained in each distance measurement were averaged to obtain the average defocus amount [DFx].
Repeat distance measurement one time at a time. And <El> ~ <E4>
, <Fl>~<F4>.

When the average defocus amount [DFx] is determined in each of the four distance measurements from <G1> to <G4>, a moving object determination is performed using these four average defocus amounts [DFx]. The speed of the object that can be detected with this "moving object detection type (■)" is a speed of 0.25 mm/s1 or more in terms of film surface. If the subject is detected as a moving object using this “Moving Object Detection Type■”, the operation mode will be set to (Moving Object Mode).
and performs moving object correction and moving object display.

FIG. 7 and FIG. 8 specifically show the flow of moving object detection using "moving object detection type ■" and "moving object detection type ■". Corresponding to the flowchart in Figure 5 above, <#5
16> and <#518> are based on "moving object detection type I", and <#524> to <#532> are based on "moving object detection type ■".

In the “motion detection type ■” shown in Figure 7, first <#71
0>, it is determined whether [LCNT] is "3" or more.

[LCNT] is a drive counter that counts how many times <#540> lens drive has been performed. By clearing this drive counter when the photometry switch (SL) is closed, this drive counter is incremented each time <#750> is passed, and is used as a counter for entering moving object determination. Check the driving counter in <#710>, and if the lens is driven for the third time or more, <#7
15> to find the subject speed (<C> and < in Figure 6)
D> distance measurement). Subsequently, if the drive counter is "3" in <#720>, the process exits to <#750>. If the drive counter is "4" in <#720> (distance measurement of <D> and <E> in FIG. 6), a moving object determination is performed.

Next, each condition for moving object determination is checked. In other words, <1725> used an auxiliary light circuit (ASL) (
(auxiliary light AF mode). <#730
> to determine that the subject is not dark. It is determined that the image is not dark if the gain of the amplifier circuit (AGC) in the focus detection circuit (AFS) is less than 4 times. <#
735>, it is determined that the subject magnification is not high. This is because when the magnification is high, the variation in distance measurement is large and the detection error is large. And in <1745>, <171
5) The subject speed detected in the past two times (6th
It is determined that the directions (obtained from the distance measurement results of <C> and <D> in the figure and those obtained from the distance measurement results of <D> and <E>) are in the same direction. Then, when each of the above-mentioned conditions is satisfied, in <#745>, the past two subject speeds are averaged to obtain the subject speed to be used in <#534> and below.

Here, in order to perform the moving object determination using this "moving object detection type test", there is another condition that it does not enter the in-focus zone, but the detailed flow of this in-focus zone determination performed in <#514> is as follows. This will be explained using FIG. 9.

In this flow, first, check the drive counter in <#910>, and if it is greater than or equal to "3", set the focusing zone to [200 μm] in <#920>, and if it is less than "3", set the focus zone to [200 μm]. 930>, set the focusing zone to [80μm] (
In the distance measurement of <A>, <B>, and <C> in Fig. 6, [8
0μm], <D>, <E> [200μm]
). Therefore, in continuous AF, the focus zone is usually [200 μm]. And <
#940> compares the defocus amount [DF], which is the distance measurement result, with the focus zone set in <#920> or <#930>, and if the focus is in focus, proceed to <#520> and out of focus. If so, proceed to <#516>.

FIG. 8 shows "moving object determination type (■)". first,
Defocus amount [DF] by closing the photometry switch (Sl)
It is assumed that the sum memory [DF(sum)] has been cleared. Then, as a result of the judgment in <#510>, when the flow after focusing (<#524>~) is entered, the defocus amount [OF (current)] and [DF (sum)] and save to [DF(sum)]. <#80
5>, it is determined whether or not the distance measurement has been performed four times in a row. If the distance measurement has not been performed four times, the process proceeds to <1807> and the first determination counter [m] is counted up. ,
Return to main routine (<#590>')
.

Next, in <#810>, a second determination counter [l] that determines how many times the four consecutive distance measurements have been performed is counted up. Note that both these counters [l] and [m] are
It is assumed that the value is cleared when the photometry switch (Sl) is closed. Further, in <#815>, only the first determination counter [m] is cleared.

<1820>, the sum of the four defocus amounts [DF(
sum)] is divided by 4 to obtain the average defocus amount [DF (average)]. In <#825>, it will be described later whether or not the first value of this average defocus amount [DF (flat)] after focusing (hereinafter referred to as the base defocus amount), cDFo:] is stored in memory. Determine using memory flag. If the base defocus amount [DF,] is in the memory, proceed to <#840>, otherwise <#830>
Then, set the first average defocus amount [DF (flat)] as the base defocus amount [opoco], and
#835> sets the memory flag (used in <#825>).

In <#840>, the average defocus amount [DF (average)] obtained in <#820> is stored in the memory [DF, ], and the four memories [DP4] and [DF3] are stored.
.

Shift the data in [DF2] and [DF,] in order.

Therefore, the latest average defocus amount [DF (average)] is always stored in the memory [DF4].

In <#845>, <#850>, and <#855>, determination is made to escape from the moving object determination state and perform AF focus.

First, if the subject is determined to be dark in <#845>,
In other words, the amplifier circuit (AGC) of the focus detection circuit (AFS)
) is determined to be 4 times or 8 times,
<#850> The magnification [1
/15], in addition, <#85
If the latest average defocus amount [DF,] and base defocus amount [DFo] change in the direction of distance by [300 μm] or more at
65> sets the AF flock flag and returns to the main routine (<#590>).

If the AF flock flag is not set, <#86
0>, if it is determined that the latest average defocus amount [:DF,] has moved closer (towards [400 μm] or more, the object speed [V ] to [0.25mm/s], which is the minimum speed for maintaining (moving object mode), and <#53
Proceed to 4>.

On the other hand, in other cases, the focal length of the photographing lens is determined in <#864> and <#866>, and the moving object determination level from <#875> is switched. If it is determined in <#864> that the focal length [f] is smaller than 150 mm,
Set the judgment level [Cn] to [:lOOμm] with <#867>.
Then, with <#866>, the focal length [f] is [200 mm
If it is determined that it is smaller than C, the determination level [Cnl] is set to [150 μm] and the focal length [f] is set to [2
00mm], the determination level [Cnl is set to [200u, m] in <1869>. This determination level [Cn] is for determining the difference between two values of the average defocus amount [DF (average)].

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

That is, as a result of the determination of <#864°> and <#866'), if the product [f・β] is smaller than "5", the moving object determination level [Cnl is set to [100 μm]<#867'
>If the product [f・β] is “5” or more and less than “20”, set the moving object detection level [Cn] to [150 μm]<#86
8”>, if the product [r・β] is “20” or more, set the moving object determination level [Cn] to [200 μm l<#869'>,
After setting each, proceed to <#870>.

In <#870>, it is determined how many times the four consecutive distance measurements have been performed, that is, whether the average defocus amount [DF (flat)] obtained for each of the four consecutive distance measurements has reached four. death,
If there are four or more, moving object determination is performed from <#875>. This moving object determination is based on [DF, -DF, ≧Cnl and [DF
, -DF2≧Cn] and [DF4-DF,≧1.5・Cn
] The object is determined to be a moving object if all three conditions are satisfied. Here, the reason why the determination level is [1,5·Cn] for the last condition is that the span is 1.5 times that in other cases.

Next, in <#895>, calculate the two average defocus amounts [DF
! ], [DF,] and the time between these two distance measurements to find the subject speed [■,], and ＜#897
> Similarly, the two average defocus amounts [DF4],
Obtain the subject speed [v2] using [Dp2] and the time between these two distance measurements, and <#899> calculate the subject speed [vico].

[V! ] is calculated (■·(V, +V2)/2) to obtain the average subject speed [V], and then the process proceeds to <#534>.

Below, in the moving object correction, the average subject speed [V] is used to predict the amount of defocus at the end of the next distance measurement,
The focus adjustment operation is repeated by calculating the lens drive amount in addition to this amount. When the image is focused, 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), but during exposure control, the focus detection optical system (AO)
It is constructed in such a way that no light can enter.

To explain moving object correction using Figure 1O, film (F
) is a photographic lens (TL
), the ray flux passes through the finder optical system (F
I) anti-transmissive main mirror (MM) for reflection;
The light that passes through the total reflection sub-mirror (SM) and reaches the focus detection optical system (AO) is reflected elsewhere when the mirror-up is started under exposure control. At this time, if the subject is a moving object, a shift in focus will occur during the mirror-up. In order to correct the focus shift during this release time lag (hereinafter this operation is referred to as focus compensation), the shortfall in the amount of movement of the photographing lens during the release time lag is compensated for by driving the lens during mirror up (hereinafter this operation is referred to as focus compensation). (referred to as "drive during up"). In the figure, the out-of-focus amount due to the distance (leaf) that the subject has moved is corrected by the above-mentioned 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.

Figure 11 shows the case of "moving object detection type ■", where <X> represents the integration timing, <y> represents the calculation timing, and (
The curve 0) represents the movement of the subject, and the straight line (L) represents the movement of the photographic lens. The speed of the objects shown in FIG. 11 is quite slow, and the objects shown in FIG. 11 also include objects that have started moving from a stopped state.

As a result of distance measurement <C>, the camera is in focus, and the following four consecutive distance measurements <D>, <8>, <F>, <G> determine that the subject is a moving object, and the timing of <T> Enter (moving object mode). When entering the (moving object mode), the respective calculation end times <tIl> and <t12>.

The defocus amount is “0” at <t+s> and <t+4>
Control the movement of the photographic lens so that For example, if an interruption occurs between timing <tts> and timing <j+4> due to closing of the release switch (S2), mirror-up will start at the next focusing timing <j+4>. Then, the amount of defocus that deviates during mirror up is corrected by driving during mirror up, and at exposure timing <S>, the photographing lens is moved so that the amount of defocus becomes "O#".

Figure 12 shows the case of "Moving Object Detection Type I", in which the photometry switch (Sl) and release switch (Sl) are used from the beginning.
2) is a closed state. Note that the closing of the release switch (S2) is the same operation as shown in the figure, regardless of the timing, until distance measurement of <F> begins. When using “Moving Object Detection Type I”, when shooting a fast-moving subject, distance measurement <
A> to <E> are not in focus. Therefore, as explained in FIG. 6, the camera enters (moving object mode) at timing <T> after driving the lens four times, focuses on distance at <F>, and performs a release operation.

In this case as well, driving is performed during mirror up, and the photographing lens is moved so that the defocus amount becomes "0" at exposure timing <S>.

FIG. 13 shows a case in which the same subject as in FIG. 12 is brought into focus at distance measurement <D>, which begins to widen the in-focus zone. In this case, (moving object mode) cannot be entered.

However, considering the range of [200 μm] in the widened focusing zone, a deviation of at least [200 μm] may occur during exposure. Therefore, in order to compensate for this focus shift, <
The amount of defocus (the amount of defocus up to P) determined by the distance measurement of D> is corrected by driving while the mirror is up.

This method makes it possible to eliminate release lag due to out-of-focus without missing a photo opportunity, even if the subject is too small to enter (moving object mode). That is, although the camera is released with the focal zone widened, the out-of-focus caused by widening the focal zone is reduced by driving the lens while the mirror is up.

Table 1 on the next page summarizes this drive during mirror up.

Mirror-up drive does not always occur, but can be switched depending on the autofocus mode.

If you want to fix the focusing because the photographer intended to shake the camera (<#855>), or if the accuracy of motion detection seems to be low, such as when the subject is dark or the magnification is high (<#845> , <#850> ), for slow moving subjects that do not require (moving object mode) (
<#855>) Both are AF flocks. Driving while the mirror is up during this AF lock will result in a poor photograph, so the driving is not performed while the mirror is up.

On the other hand, when a moving object approaches or moves quickly, the camera enters the (moving object mode) as described above, so the mirror is driven while it is up, and moving object correction is calculated to ensure that it is in focus at the time of exposure. However, since the mirror-up time is a finite time of about 70 m5, there is a limit to the amount of drive during the mirror-up. The amount of time that can be driven during this [70m5l] is less than normal full drive because the photographing lens needs to be stopped during actual exposure, so it is driven while braking. The pulse count is [40 pulses].

If this value is a shooting lens with a longer focal length than a standard lens [50/1.7], the lens will move more than [200μm], so if the shooting lens is stopped at the edge of the focusing zone [200μm]. Only this value can drive the lens.

If the required lens driving amount exceeds this [40 pulses], the start of mirror up is delayed by [40 m5] and the lens is driven during this time. We also put a limit on the amount of lens drive before the release, so as not to lengthen the release time lag (only an increase of [40m5]).
Unlike the mirror-up drive, full drive is possible, so the drive amount is secured for [70 pulses], making a total of [110 pulses].
This makes it possible to drive the lens accordingly. This results in
If the conversion coefficient [K] between the defocus amount and the lens drive amount is small, a lens movement amount of [2000 μm] can be secured, and even if the front-rear conversion coefficient [K] is large, it is possible to secure a lens movement amount of [100 μm].
Since it is possible to secure a certain amount of lens movement, this value can be said to be sufficient for focus correction.

Next, in the case of non-moving object mode, in this mode,
If the release switch (s2) is closed before focusing, and if the subject is moving and moving slowly, you can immediately perform the release operation without entering (moving object mode). (See Figure 13). In this case and in the case of continuous AF, driving is performed during mirror up without performing moving object correction (unnecessary in the method of this embodiment). The amount of drive at this time is calculated from the result of distance measurement just before the mirror is raised. On the other hand, in the case of a stationary subject or a slow-moving subject, the moving object determination is repeated after focusing.

During this time, if an interruption occurs due to closing of the release switch (S2), the mirror is driven while the mirror is up without moving object correction. At this time, it is impossible to determine whether the photographer is trying to photograph a stationary subject or a slow-moving subject.

For example, if you want to focus on AF, if you drive while the mirror is up, the picture will be unintended.

Therefore, if the subject is in the in-focus zone, the drive will not be performed while the mirror is up, and if the camera has been shaken, the drive will not be performed while the mirror is up. Since it is slow, I assumed that it would be slow and moved the photographic lens slightly by driving while the mirror was up.3.
As a control method that satisfies two phenomena, the amount of defocus [
70 to 200 μm], a method is adopted in which driving is performed during mirror up. In other words, the amount of defocus is [
If the amount of defocus is less than [70μm], it is within the focus zone, and if the amount of defocus is more than [200μm], the camera will be shaken,
If the defocus amount is [70 to 200 μm], it is determined that there is movement of the subject.

Next, the driving amount will be explained with reference to FIG. 14.

Since focus was achieved during distance measurement <C>, considering the dispersion in distance measurement, distance measurement <D>, which is averaged, is more accurate. Therefore, during mirror-up driving during moving object determination, the driving amount is determined based on the average defocus amount. First, if the release switch (S2) is closed before entering (moving object mode) assuming that the subject is moving, then the amount of defocus (in Fig. 14) determined from the latest distance measurement results is It is preferable to drive the mirror while it is up using the average defocus amount (DFi) obtained from the results of distance measurement in (1) (line (i) in FIG. 14). Also, assuming that the subject is still, the point of focus can be seen in the viewfinder, so the amount of defocus (<D in Figure 14) determined from the distance measurement results immediately after focus is
> average defocus amount obtained from the distance measurement results)
It is better to use [DFd] to drive while the mirror is up (
(line (ii) in FIG. 14). Furthermore, if the AF is focused and the camera is shaken slightly (a shake of the camera that cannot be detected with <#855>), the measurement will be performed after [about 0.8 seconds] have passed after confirming focus. Defocus amount determined from the distance result (<G> in Fig. 14)
The average differential gear loss amount [DF
g] ) to drive the mirror during mirror up (line (ii) in FIG. 14).

Note that the word "premise" here means a camera that emphasizes this. In other words, it is possible to set in advance which distance measurement result to use to drive the mirror while it is up, depending on the intended user of the camera.

For even more detailed control, it is possible to switch which distance measurement result to use to drive the mirror while it is up, depending on the time from focusing to closing the release switch (s2). preferable. As mentioned earlier, the time it takes to shake the camera after focusing is [0
, 8 seconds or [1 second], and by the time the distance measurement of <G> is carried out at the timing of [0.8 seconds] after focusing, <j41> in Fig. 14. If an interrupt is generated by closing the release switch (S2) at the timing, the mirror is driven up using the average defocus amount [DFe] obtained from the latest distance measurement result of <E> at that time.
<1< in Fig. 14 after the distance measurement of <C> which is performed at a timing of [0.8 seconds] after focusing. If an interrupt is generated by closing the release switch (S2) at the timing of <D>, the average defocus amount [DFd] obtained from the distance measurement result of <D> is used to drive the mirror up.

By doing this, it is possible to take a photograph that is in focus even when the camera is shaken for AF focus and the release operation that matches the photographer's intention is performed only after a period of [0.8 seconds] or more has elapsed.

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

When this subroutine is called, first <#1500
>, 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 performing mirror-up driving. In <#1538>, the drive pulse counter [ECNT] for driving the lens is set to "0', and then the process returns to the main routine. Similarly, in <#1502>, (auxiliary light A
F mode), the process proceeds to <#1.538> without driving the mirror up.

This (auxiliary light AF mode) is switched according to the flow shown in FIG. The flow shown in Fig. 19 is a flow that is inserted between <#514> and <#516> in Fig. 5, and this flow is passed when the judgment in <#514> is out of focus. It has become.

In this flow, first, in <#1900>, it is determined whether the subject has low confidence, that is, the reliability of the focus detection result, and if it is low confidence, that is, if the reliability is low, then in <#1902> to determine whether the subject is dark. This judgment is performed by the focus detection circuit (
It is determined that it is dark when the gain of the amplifier circuit (AGC) of the AFS is twice. If this corresponds to the Apex digital signal [Bv], it becomes [-1]
corresponds to If it is determined in <11902> that the subject is dark, the auxiliary light flag is set in <#1904> and then 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>').

Then, if this auxiliary light flag is set at the next distance measurement,
When integrating the step <#500>, the auxiliary optical circuit (AS
The auxiliary light is projected onto the subject from L).

Returning to Fig. 15 and continuing the explanation, next, <#1504
> to determine whether it is in (moving object mode). If it is not (moving object mode), then the AF flock flag is determined in <#1506>.

If the AF lock is activated, the process proceeds to <#1538> without driving the mirror up as shown in Table 1.

If AF rotation is not in progress, it is then determined in <#1508> whether or not continuous AF is in progress.

If it is determined to be continuous AF based on the determination of the continuous AF that exited from (moving object mode) or the continuous AF flag sent from the card circuit (CD), the process advances to <#1514> and the current Set the current defocus amount in the mirror-up drive memory [DFm]. This defocus amount [DF
(Now) is the defocus amount at the time when focus was determined before entering this flow, and is not the average defocus amount.

If it is determined in <#1508> that continuous AF is not used, then in <#1510> it is determined whether the base defocus amount [DF,] is stored. If the base defocus amount [DFo] is not stored, the process also proceeds to <#1514>. An example of this is
Before focusing, press the metering switch (Sl) and release switch (
S2) are both closed (hereinafter referred to as release start before focusing), and the moving object determination routine of FIG. 8 is not passed, so the pace defocus amount [DFo
]. That is, even when the release is started before focusing, the defocus amount [DF (now)] at the time of focusing judgment is used to drive the mirror while it is up. Also, even during the moving object determination routine, if the initial average defocus amount cannot be calculated, the <#1510> determination will be made in the same manner.
514>.

On the other hand, if an interruption due to closing of the release switch (S2) occurs during the moving object determination, the process proceeds to <#1512>. In <#1512>, the average defocus amount [Ko (flat)] is set in the memory for driving during mirror up [DFml]. There are various embodiments of this step <#1512> depending on what kind of shooting situation the camera emphasizes, that is, the premise of the camera. Figure 16 (a)
Some examples are shown in (e) and (e).

FIG. 16(a) shows the case of a camera that assumes a stationary subject, and the base defocus amount [DF,] is set in the drive memory [DFml]. Figure 16 (b) shows the case of a camera that assumes a moving subject, and the latest average defocus amount [DF,] is stored in the driving memory [DFml].
Set to .

Figure 16 (c) shows the case of a camera designed for portrait photography, and when [0.8 seconds] have elapsed since focus, <G
The focusing average defocus amount [D
Drive memo I) [Set F pull to DFml. Note that when using this flow, the flow shown in Figure 20 should be placed between <#870> and <#875> in Figure 8 to set the average defocus amount [DFG] after focusing. is necessary.

In other words, if the second judgment counter [n] is "4", it means that there are four average defocus amounts [DFx], and it is determined that exactly [0.8 seconds] have passed since in-focus. Therefore, the flow is to set the average defocus amount [DF,] at this point as the in-focus year average focus 31 [DFG].

FIG. 16(d) is a case where a versatile camera or a beginner's camera is used, and the time from focusing to the current timing, that is, the opening timing of the release switch (S2), is measured in <#1610>. t3] and <#1612
> determines whether this time [t,] is less than [1 second], and if it is less than [1 second], it is determined that the camera is not shaken, and <#1614> determines the latest average defocus. amount[
While setting the drive memory [DF,] to the drive memory [DFml,
If it is longer than [1 second], it is determined that the camera is being swung midway, and in <#1616>, the base defocus amount [DF
,] is set in the drive memory [DFml.

This is to prevent a change in defocus amount caused by shaking the camera with respect to a stationary subject from being mistaken for a movement of the subject.

In other words, if the object moves so slowly that it is not determined as a moving object in the moving object determination flow, the focusing accuracy will be better if the lens is driven using the latest average defocus amount. However, if the lens is driven using the latest average defocus amount, if the camera is gently swung toward a stationary subject, the AF focus judgment will be A.
Instead of being judged as an F focus, the focus will be on a completely different area. In order to prevent such a situation, the value set in the drive memory [DFml] is changed depending on the time from when the camera is in focus until the release switch (S2) is closed.

Fig. 16 (e) is a modification of Fig. 16 (d), in which the average defocus amount [DFG] after focusing is stored to determine the time from in-focus to the occurrence of an interrupt due to closing of the release switch (S2). This is used as a substitute for determining whether or not the If the average defocus amount after focusing [DFG] is stored, it is assumed that more than [0.8 seconds] have passed after focusing.
1622>, the base defocus amount [DFO] is set in the drive memory [DFml], and if the average defocus amount after focus [DFG] is not stored, it is used for one-shot AF or for a moving subject. As focus compensation, the latest average defocus amount [DF,] is set in the drive memory [DFml] at <11620>.

By the way, these were all explained as different embodiments, but
All these flows are included in the microcomputer (μC) program, and the card circuit (CD) and memory IC (E
The above five flows (
By switching between (a) and (e) in FIG. 16, one camera can be set to different operating states.

For example, when assembling the camera, write memo - January C (E"FROM).
) If you write "l" in the specified address, the flow shown in Figure 16 (a) will be executed, and if you write "2" in the first address
Each of the flows shown in FIG. 6 (b) may be selected. Similarly, when replacing an IC card, if an IC card written as "l" is attached to a predetermined address of the card circuit (CD), the flow shown in Figure 16 (a) will be changed. The flow shown in FIG. 16(B) may be selected when the IC card is installed.

Returning to FIG. 15 and continuing the explanation, the drive memory [DF
After any of the average defocus amounts described above is set in <#1516> and <#1518>, the lens drive amount data in the drive memory [DFm] is used to determine whether the mirror up drive is possible. - Make a zone determination of impossibility, and if the lens driving amount is [70 μm≦lens m<200 μm], proceed to <#1520> to perform mirror-up driving.

If it is determined in <#151.6> that the lens drive amount is less than [70 μm], the mirror-up drive is not performed and the process returns to the main routine. That is, this <#151
It is thought that step 6> is often taken when the subject is still, and in this case, there is no need to drive the mirror up while it is within the in-focus zone.

be. It also has the meaning of not making the feel worse when the mirror is up.

Also, with <#1518>, the lens drive amount is [200μm]
If it is determined that the above is the case, the mirror-up drive is not performed and the process returns to the main routine. That is,
If the subject is moving fast, use <#1540> or <#15>
Go to <14> (so only subjects with slow moving speed are
1518> and the movement speed is slow, the maximum amount of drive during mirror up is [200μ
This is because less than m] is sufficient. Conversely, if the lens drive amount exceeds [200 μm], there is a possibility that the camera was shaken but the AF did not work.

On the other hand, when branching to <#1514>, since it is completely unclear whether the subject is a stationary object or a moving object, the process proceeds to <#1520> on the premise that the mirror is being driven while the mirror is up.

If it is determined in <#1504> that the mode is (moving object mode), the process proceeds to <#1540> and starts from the time when the light receiving circuit (CCD) starts integrating the current defocus amount [DF (now)]. Currently, the release switch (S
2) The time until the closing timing is measured and set as [t,]. In <#1542>, add the mirror-up time lag [70m5] to this time [t1] and get [ttl
Then, multiply the moving object speed [V] calculated during (moving object mode) in <#1544> by this time [t2] to find the amount of focus deviation [ΔDF] due to the movement of the subject during the time lag from integration to exposure. (Hereinafter, since moving object correction is performed using this amount of focus deviation [ΔDF], this amount of focus deviation [ΔDF] will be referred to as a moving object correction amount).

Subsequently, in <#1546>, the sign of the moving object speed [V] is determined. In this determination, if [V>Ol, it means that the defocus has increased in the direction of focus, and it is determined that the subject has approached the camera.

If it is determined that the subject is approaching the camera, <11
550>, the moving object 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 amount of defocus on the image plane does not change at a constant speed, but is a reciprocal function of the speed, and if it is approximated by a straight line, there will be insufficient correction. This is to prevent this from happening. Therefore, as a correction coefficient [1+1/X]
think of. Considering the assumed moving speed of the subject, the above variable [x] is set as an experimental value of [3 to 5].
The results show that the range of .
), 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 is moving away from the camera, <#
1548> and set the motion correction amount [ΔKanoko [1-1/4
] Multiply by the coefficient.

After that, in <#1552>, value correction is applied to the moving object correction amount [ΔDF] in consideration of the error in the conversion coefficient [K] between the defocus amount and the lens drive amount in the photographing lens. To specifically illustrate this value correction, as shown in Figure 18,
The error in the conversion coefficient [K] is large when the shooting lens is open to F.
Since it tends to depend on the value [AVo], the open F value [A
If Vo] is larger than the predetermined value [Jl], that is, if the photographic lens is dark, the moving object correction amount [ΔD
F] is multiplied by [1,2] times the coefficient, and then the conversion coefficient [
If the value of [K] is small, the amount of lens movement per one count for lens driving is large, so the conversion coefficient [K
] error becomes large, so in <#1806> the moving object correction 1 [ΔDF] is multiplied by a coefficient of [1, 2] to compensate for the lack of correction amount.

After performing the K value correction, <#1554> adds the moving object correction amount [ΔDF] to the current defocus amount [DF (current)].
] is added and stored in the drive memory [DFm], and then the process proceeds to <#1520>.

<#1524>, <#1518>, <#155
In <#1520>, which proceed from 4>, the conversion coefficient [[
K] and the drive pulse counter for lens drive [E
CNT]. <#1522), the value of the drive pulse counter IJCNT is "4", which is the maximum number of pulses that can be driven in a limited time while the mirror is up.
Checks whether it is larger than "0". If it is determined that it is smaller than "40", the process proceeds to <#1536>, starts lens driving, and returns to the main routine.

On the other hand, at <#1522>, the drive pulse counter [ECN
If it is determined that the value of T] is equal to or greater than 40, the lens is driven before starting exposure control, but the amount of drive is also limited. That is, <
#1524>, the drive pulse counter [ECNT]
It is determined whether the value of is larger than "110", which is the sum of "70", the maximum number of pulses for the pre-release drive, and "40", the maximum number of pulses for the drive during mirror-up. “110
``If it is determined that the pre-release drive pulse counter [EECNT] is set to ``70#'' in <#1528> in order to perform the pre-release drive for the maximum number of [70 pulses]. Furthermore, if it is determined in <11524> that the value of the drive pulse counter [ECNT] is smaller than "110", the value of the drive pulse counter [ECNT] is determined in <11526>.
The value obtained by subtracting "40" from the value of T] is set in the pre-release drive counter [EECNT].

Next, at <#1530>, the pre-release lens drive is started, and at <#1532>, the pre-release drive pulse counter [
EECNT] waits until it becomes "0". The maximum driving time of this pre-release lens driving is [approximately 40 m5], and the time lag does not increase significantly. <#1534
At <11536>, the drive pulse counter [ECNT] is set to "40" so that the remaining lens driving is performed during mirror up, and at <11536>, lens driving is started and the process returns to the main routine.

After returning from the subroutine (LNS>>, the main routine calls the subroutine (exposure control) at <#455>. Figure 17 shows this subroutine (exposure control).
This shows the general flow of the process.

When this subroutine is called, first <#1724
> to start the mirror up, and <#1726> to start the aperture operation of the photographic lens. Then (moving body mode)
etc., the lens drive has started during mirror up, so the drive pulse counter [ECNT
] Waits until the value becomes "0". Note that if the lens is not driven during mirror up, the drive pulse counter [ECNT] is initially set to "0", so <#1728> passes through immediately. And <#17
After completely stopping the photographic lens at <#173>
2>, wait until [70m5] has elapsed from the start of mirror up. That is, the operation of the mirror aperture and the diaphragm ends at [70 m5]. After all lens drive and aperture operations are completed during the mirror aperture, the exposure operation begins from <#1734>.The front curtain of the shutter curtain is run at <91734>,
At <#1736>, wait for the exposure time determined by the calculation at <#430> in the main routine, and at <#1738> run the rear curtain of the shutter to complete the exposure. Return to routine.

Above, I have explained the basics of camera operation (1), but the microcomputer (μC) that performs these operations is
When the absolute value of the detection deviation by the focus detection means is less than or equal to the set value, it constitutes a focus determination means that determines that the focus is half 1153 + 1. A focus adjustment control means is configured to prohibit the operation of the focus adjustment means after the focus determination means determines that the object is in focus when the subject brightness is lower than the set brightness.

[Another example]

Other embodiments other than those described in the previous embodiments will be listed below.

<1> The reference values for various judgments that have been made to judge the condition of the subject and the intention of the photographer can be changed arbitrarily.

<2> For static objects, if the subject is judged to be dark, the shooting magnification is large, or the subject is slow and moving away from the camera, driving during mirror up is always prohibited. It is not necessary to set the focus adjustment state, but it may be a moving object focus adjustment state that allows driving while the mirror is up.

<3> In the previous embodiment, if it is determined that the subject is moving at a high speed, the drive amount correction during mirror-up driving may be omitted.

4) In the previous embodiment, an example is taken in which the photographic lens is configured to be detachable from the camera body, and lens information specific to the photographic lens is obtained from the lens circuit (LEC) attached to the photographic lens. Although the description has been given of a camera configured to allow input, the present invention can also be applied to a camera in which the photographing lens is provided in a fixed state.

5) In the previous embodiment, a configuration in which three focus detection areas were provided was described, but instead, a plurality of other focus detection areas may be provided, or one focus detection area may be provided. You may also provide only

〔Effect of the invention〕

As described above, in the camera according to the present invention, when the brightness of the subject is low, the accuracy of the detection deviation is not so high and the negative effect of noise light is large. Since the focus adjustment operation is prohibited, it is possible to prevent inadvertent deviation from the focus state due to noise light etc. after focusing, and it is possible to prevent moving subjects from being inadvertently deviated from the focus state by the subsequent focus adjustment operation after focusing. Even when a focus adjustment operation with high tracking performance is enabled, it is now possible to take photos with less out-of-focus for subjects at low brightness.

[Brief explanation of the drawing]

The drawings show an embodiment of the camera according to the present invention, in which Fig. 1 is a circuit block diagram, Fig. 2 is a perspective view of the periphery of the focus detection optical system, Fig. 3 is a field view of the finder, and Figs. Figure 5・
Figures 7 to 9, Figure 15, Figures 16 (a) to (e), and Figures 17 to 21 are flowcharts showing camera operations, and Figures 6 (a) and (b) are focus A schematic diagram showing the sea fence of the detection operation, Figures 1O (a) to c) are schematic diagrams showing the relationship between the movement of the subject and the camera operation, and Figures 11 to 14 are time charts of the focus adjustment operation, respectively. It is. (TL)・・・Photography lens,

Claims (1)

[Scope of Claims] 1. Focus detection means for detecting deviation from the in-focus position of the photographing lens with respect to the subject, and determining that focus is achieved when the absolute value of the detected deviation by the focus detection means is less than or equal to a set value. In a camera equipped with a focus determination means and a focus adjustment means for moving the photographing lens toward the in-focus position by a driving amount based on a detection deviation by the detection means until the shutter starts operating, the brightness of the subject is a subject brightness detecting means for detecting the object brightness, and prohibiting the operation of the focus adjusting means after the focus determining means determines that the focus is in focus when the subject brightness detected by the subject brightness detecting means is less than a set brightness. A camera equipped with focus adjustment control means. 2. The focus adjustment control means adjusts the focus within the release time lag period after the focus determination means determines that the object is in focus when the detected object brightness by the object brightness detection means is less than or equal to the set brightness. 2. A camera according to claim 1, wherein the adjustment means is inhibited from operating.