JPH0220976A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent an image plane from becoming hard to see owing to unnecessary automatic focusing operation by controlling the focusing operation of a focus control means when brightness levels of plural areas set by dividing the image pickup image plane vary with time in the same direction. CONSTITUTION:The image plane is divided into the areas A1-A6, means 16-21 which detect the brightness levels of image pickup video signals of the respective areas A1-A6 are provided, and external light and the variation of a stop are discriminated from the relation of time variation among the brightness levels of the respective areas A1-A6; when the external light and stop variation are present, the focusing operation in this period is restricted. Therefore, even if a focus evaluated value is varied owing to the brightness variation of the whole image plane due to the external light and stop variation, the focusing operation is inhibited to prevent, an image plane which is hard to see owing to the unnecessary driving of a focus actor is prevented from being projected.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an autofocus device that automatically aligns the focus, and an optical diaphragm mechanism that adjusts the amount of light incident on an image sensor to obtain the optimum amount of light. Relating to an imaging device such as a video camera, which is equipped with an exposure!l!I device that controls the exposure.

(b) Conventional technology In the autofocus device of a video camera, the method of using the video signal itself from the image sensor to evaluate the focus control state is essentially It has many excellent points, such as being able to focus accurately even when the depth of field is shallow or when photographing distant subjects.Moreover, there is no need for a special sensor for autofocus, and the mechanism is extremely simple. Japanese Unexamined Patent Publication No. 105978/1983 (
HD4N5/232) discloses an example of the above-mentioned autofocus device.

In the conventional technology, the high-frequency component level of the captured video signal is set at the center C of the screen: A within the set focus area.
/D conversion, this converted data is integrated for each field using an integration circuit, this digital data for one field is held as a focus evaluation value, and compared with the evaluation value of one field before, the focus is always determined. The direction in which the evaluation value is the maximum τ (drive control of the Nifocus hair).

(c) Problems to be Solved by the Invention In the autofocus operation according to the prior art C2, the lens position is always controlled so that the focal point value is maximized based on the high-frequency component level of the luminance signal of the imaged video signal (2). However, the absolute value of the high-frequency component level in the captured video signal changes even if the deviation of the point i from the in-focus point (i.e., the change in the brightness level of the subject) changes.

Therefore, the distance c from the lens to the subject = no change (
= Nevertheless, if the brightness level of the subject changes due to changes in external light or the automatic exposure adjustment mechanism that controls the aperture of the lens, C2 is also worth focusing! = changes occur, unnecessary autofocus operations are performed, and the screen becomes unsightly.

2) Means for solving the problem Is the present invention a screen? divided into a plurality of areas, provided with means for detecting the brightness level of the imaged video signal in each area 1:, and identifying fluctuations in external light and aperture from the relationship of temporal changes in the brightness level of each area; When it is identified that these external light or aperture fluctuations are occurring, the focusing operation during this period is regulated. Aperture variation (
Focus evaluation value (even if a change occurs, unnecessary auto 7 orcus operation is prevented.

(F) Embodiment Hereinafter, two embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit block diagram of this embodiment. (1) is the video camera section with Jb 7% focus lens + 21'
A focus motor (4) that drives the focus ring (3J?) that supports it and moves it forward and backward in the optical axis direction, an optical aperture V mechanism (6) that controls exposure, and an iris motor (7) that moves this aperture mechanism (61vm). An image pickup circuit (8) having a solid-state image pickup device (aCD) y that converts a subject's light, sound, and image signals into two signals is disposed.

The luminance signal in the captured video signal obtained by the imaging circuit (8) is processed by a bypass filter (Hpp) t9), a low pass filter (LPF) (111 and a sync separation circuit 11).
2+ += sent.

A vertical synchronization signal (VD) and a horizontal synchronization signal (BD) which are separated from the luminance signal by a synchronization separation circuit 0 are supplied to a switching control circuit (13i) which sets the sampling area.

Switching control circuit (13 is vertical and horizontal synchronization signal (VD)
) ID) and Ij which becomes the clock that causes 0OLJn#1AiltlI! Based on the oscillator output of 11 feet, Figure 2C
2 As shown, there is a rectangular first sampling area (A1) in the center of the screen, and a second sampling area (A2) in the area (A1) surrounding this area (AI).
And in order to set the surrounding area (A2) C2 and the sixth sampling area (Al) (A4) (A5) (A6), the switching circuit α1 is supplied with the switching signal (82)'& ( 2. Hp F (9) Gate signal (3) that allows the output to pass through the sampling area (A1)
1) '& Gate circuit 041 + = Supply O The gate circuit 1141 receives the gate signal (81) 'i' and passes only the high frequency component of the imaged video signal within the first sampling area (A1) as described above. , subsequent integration circuit-C: Output.

The switching circuit cl() receives the switching signal (S2) and switches the LPF
(Ill output is input to the template area (=accordingly, the subsequent integration circuit - an c selective C: input. That is, the first
Sampling area (AI) (:, LPF (lυ
Specific output integration circuit assignment: r regarding the second to sixth sampling areas (A2) (AS)...(A6) below,
pF (111 outputs are integrated circuits itηαa・−aυ
Output to.

The integration circuit α9 is composed of an A/D converter, an adder@, and a memory circuit r24[:, and the A/D converter is a selection circuit α!
91: The outputs of each filter passing through are sequentially A/D converted, and the adder c! The 0 adder (to) that outputs 3+= forms a digital integrator together with the A/D converter at the previous stage @ the memory circuit Q4 of the induction stage, and the output of the memory circuit C241 and the A/D converter The outputs are added and the addition result is supplied again to the memory circuit R24 (2.Memory circuit C24).
) is reset for each field, and the output of the adder (to), that is, the HPF (9) is converted into the first sampling area (A1) of the digital conversion value of the level of the luminance signal (one field of two To hold C: become 〇 integration circuit (
1119tiηαS-a! υ(: Even if the integration circuit a
It has exactly the same configuration as 9, and each of the integrating circuits ζ:
Built-in memory circuit C: stores the current field [2] and selected LPFC for each sampling area.
One field (two integrated values) of nine luminance signal levels are held when LII passes through.

The integrated values of each of these memory circuits are collectively stored in the subsequent memory circuit. The cutoff frequency of LPF (ill is 0 to 2.4M).
H! It is set to allow the passage of the following bands. Furthermore, 2
．． 4Muz is an extremely high frequency that has no direct relation to the luminance signal, and its value (: It has no meaning, HP F
(9) only needs to be able to produce a band of 200KHz or more,
L P F (11+ is substantial [: is omitted, LPF
When nυ is selected, the imaging brightness signal is directly transferred to the switching circuit II.
may be supplied to

Therefore, either t of aplF(91 and LPF(lυ)
The high-frequency and low-frequency components of the passed luminance signal are integrated for one field (digital) and stored in the memory circuit (C) as the evaluation value of the current field for each sampling area. Then, it becomes C; Here, memory circuit (c) C= Among the stored integral values, Lpyau
The integral value of the low frequency component at 9 o'clock is calculated per unit area (: normalized and used as the exposure evaluation value for exposure control.
The integrated value of the high-frequency component at 9 o'clock is calculated by a microcomputer at the subsequent stage as a focus evaluation value for focus control.

These evaluation values are calculated by software using microcontroller 4.
Based on the processing results, the focus motor control circuit (27) issues a l=command, and the focus motor (
4) to advance and retreat the focus lens (2),
Execute the autofocus operation so that the focus evaluation value is maximum (-), issue a command to the iris motor control circuit @1, drive the iris motor (7), and operate the optical diaphragm mechanism (6).
) to enable automatic exposure adjustment so that the exposure evaluation value becomes a predetermined value.

Next, refer to the flowchart of the main routine in Figure 3 of C2.

When the video camera enters the operating state (:), the microcontroller @ executes the main routine shown in Figure 3 for each field. First, the 5TEP (3Q1; The integral value for one pulse is read into the microcomputer (to).

Next csrgPcl old: The integral value obtained by the integration circuit 19 (:) is defined as the focus evaluation value (Xn), and the focus evaluation value χ0(n-1) at 1: previous field; 2 is defined.

Also 8 T E P # J7 JI” knee integration circuit +16
1 (17)...Divide the integral value obtained by dividing the area of the corresponding sampling area by 2 (the value normalized by 2, that is, the integral value of the unit area of each area) is the exposure evaluation value of each area Y(j) (j −1 to 6
) A focusing operation is performed in the AF routine (to) using the focus evaluation value (xn) calculated as described above.

This AF routine C33) is mainly composed of five core routines as shown in FIG. So, this AP routine (to explain in detail in two ways, as mentioned above)
The AF routine consists of five routines: the evaluation value stability confirmation routine (see), the direction determination routine (005), the mountain climbing routine (47), the apex return routine (4), and the evaluation value fluctuation monitoring routine (47). H depending on
Operation mode code (MODI) 7g at +mp (44)
I: o ~ 4 (= specifying (2), usually the evaluation value stability confirmation routine, the one-way discrimination routine y (461→
Yamato Sirchin (4η-Vertex Return Routine)-Evaluation Value Fluctuation Monitoring Routine (C2 is executed in the order of 49).

Next (: These five routines (two) will be briefly explained.

Evaluation value stability confirmation routine (a is the operation mode code (M
When the power is turned on, OD B) becomes °0°! 47 Moaning during the meeting
- In the first sampling area (A1) designated as the focus area, the focus evaluation values (Cn and Xn-1) of the current field and the previous field are compared, and the difference is within the allowable range C: If the object is within the allowable range for a predetermined period (for example, 3 fields), it is recognized that the subject is stable, and the operation mode code (MOD E) is set to "1-1". = set,
The direction determination routine is executed from the next field. Therefore, while the subject is moving and is not stable, this evaluation value stability confirmation routine continues, effectively confirming that no two-focusing operation is being performed. and the operation mode code (MODE) is a1''' (
2, the direction determination routine (-1E9) which is recognized and executed in STEP (44)C, first operates the focus motor (4) in advance to move the focus lens (2) in a predetermined direction (e.g. ω point direction) and initialize it, and then compare the focus evaluation values Xn and Xn-1 of the current field and the previous field over a predetermined period of time. 1: The focus evaluation value Xn tends to increase. If it is confirmed that there is an increasing trend, the direction of rotation of the focus motor (4), that is, the direction of movement of the focus lens (2), is changed to the initial setting direction C;
If it is confirmed that there is a decreasing trend, then the rotation of the focus motor (4) is increased (reversed) to determine the direction. When this direction determination is completed, the operation mode code is (MODIB) is changed to 2° and the υ mountain climbing routine (4η) is executed in the next field.

In this mountain climbing routine (4η), the focus motor (4) is rotated in the direction C determined in the direction determination routine described above, and the focus evaluation value of the current field and the previous field is Xn%.
Comparing Xn-1'2, the C two focusing positions as shown by the arrows in Figure 4:; is the slope of the mountain peaking? While climbing (-i.e., the focus evaluation value xn of the current field is the focus evaluation value of the previous field)
(While it is larger than n-1, the rotation direction of the focus motor (4) continues to change, and the focus evaluation value exceeds the reference value (
When it is confirmed that the focus evaluation value Xn in the second field has fallen by more than Δ
Change D E) to "6-ζ; and execute the apex return routine (decoy) in the next field. By the way, this mountain climbing jill-chin α7) C; rotates the focus motor (4), which is a stepping motor. The amount is set for 10 steps per field.

In the above-mentioned mountain climbing routine, the focus evaluation value Xn of the current field C is the focus evaluation value of the previous field) (n-1
Each time the focus evaluation value becomes larger, the current focus evaluation value Xng is held as the maximum evaluation value 1 to 6), and then store the lens position at which this maximum evaluation value (XuAz) occurs as the focus position.The focus position is stored as follows:
A position that is reset every time the maximum evaluation value (XMAX) is updated, and is an UP/DOWN counter that always counts the rotational step amount of the focus motor (4), and for example, adds in the ω point direction and subtracts in the periapsis direction. Memory (ME) is used. Therefore, after reaching the top of the mountain (= 2 fields later C2) When the fall amount reaches the reference value (ΔX) (= (2 is position memory (ME) The steps will be memorized.

Vertex return routine (in 48, focus lens (2)
The focus motor (4
) to return to the top of the mountain. Specifically, it reverses the focus motor (4) and when the position memory (MP) reaches zero (:), the focus motor ( When 4) is stopped, the focus lens (2) returns to the focal position C:1;
Become. At this point, the operating mode code (MODI) is °4.
-, and the focusing operation from the evaluation value stability confirmation routine to the apex return routine is completed. After this, the evaluation value fluctuation monitoring operation is performed in the next field.
Niza#'Lro.

When the operation mode code (MOD E) is specified as °4 (:), the direction detection routine 15GC for exposure evaluation value changes is performed from the next field and the brightness changes for the entire screen (: 9, whether it is 9 or not). and when it is recognized that a brightness change has occurred:
: is detected whether it has changed in the direction of becoming brighter (2) or in the direction of becoming darker.Here, this directionality detection routine ω will be described in detail with reference to the flowchart in Figure 5. Describe.

First, make initial settings for each part using sTgp (51) (:), and
TRP (52) (53) l 2nd first sampling area (A1) The value Y violet (11 is compared with YM (1) C tolerance value (
If the exposure evaluation value Y(1) is larger than the value obtained by adding C:, then the exposure evaluation value Y( i) (1-2 to 6) is the standard exposure evaluation value Yl(
it(i~2~6)τ: Determine whether or not the value is greater than the sum of the allowable value (#), and accumulate the number of areas determined to be greater than srgp(55)C2.

This series of judgment operations is performed in the sixth sampling area (A, 6
), the direction flag (Fl) is set to 5TEP.
(56) Set C (in Fig. 4, it is written to substitute Fll:°1.).

Standard exposure evaluation value of Madai 1 sampling area Y M
Exposure evaluation value Y by subtracting the tolerance value (6) from (1) and 900 million
For example, if (1) is small, the exposure evaluation value of each area is Y (4) (1-2 to 6) even if there are two areas after the second sampling area (A2).
is the standard exposure evaluation value YM (L-2 to 6) l2 tolerance value (a
) and determine whether it is smaller than the next rank, S'rgp
The number of areas determined to be small in (58) is totaled. This series of detection operations is performed in the sixth sampling area (
Ad) When executed at t, the direction flag (F 1) is set to f9
'rEP (59)l': Reset (F in Figure 4)
1 j; “Write C2 to substitute 0°).

In addition, the above-mentioned tolerance value (6) is based on each standard exposure evaluation value [; relative to the exposure evaluation value of each area, taking into account the influence of noise etc. Change and nine! &! ! ! It is a position set so that it can be recognized.

Next at C19'I'EP (60) Y (83> Y M
(J) + Conditions for g: Four or more areas (two of the second to sixth sampling areas, i.e., five or more areas including the first sampling area) (if two are satisfied, or If the condition of > Y M o)-g is satisfied for 5 or more areas including the first sampling area [Secondly, assuming that a change in brightness occurs in almost the entire screen, 7'?, 5TEP ( 61) 1: Set the change detection flag (F2) 0 Thus, the change detection flag (Fl) and direction flag (F2) are set according to the brightness change C: of the entire screen. After being set or reset (:, the evaluation value fluctuation monitoring routine (49) is executed.0 Here, this evaluation value fluctuation monitoring routine (4!1111
:Refer to the flowchart shown in FA6! First of all, let me explain in detail: Does the difference between the maximum evaluation value (X-seni^I) at the time of completing the apex return routine ■ and the focus evaluation value () (n) in the current field exceed a predetermined value (r)? It takes 5TEP to decide whether or not to
0) 1m, if it does not exceed 8TEP (71) +
:The operation mode code (MOD B) is held at 4°C2, and if the subject does not move or change, it is determined that the object is 9, and the focus motor (4) is maintained in a stopped state while This evaluation value fluctuation monitoring routine is executed even if the field (= is set. Also, if the difference exceeds a predetermined value (γ), C2 is set to 8Tgp (72) and the change detection flag (F2) is set (= is 0 to judge whether or not
The more this change detection flag (F2) exceeds the reset state C: (- means focus evaluation value C2 is a predetermined value) I:
A change has occurred I: Despite this, no clear change in brightness can be recognized over the entire screen (= C2) The change in focus evaluation value is not due to a change in brightness of the screen, but is due to movement or change in the subject itself. 1: Assuming that 5TEP (
74) 2 kakunta (MO)'& increment (1
). In sTgp (75), this kakunta (
Until it is determined that the count value of MO) has exceeded 3 degrees, the operation mode code (MODE) is maintained and the focus motor (4) is kept in the stopped state, and this state is the 4 field If continued (: is the operating mode code (MODE) i8Tmp (76)l2°1-
, and the direction determination routine (,1
The series of focusing operations after 119 are restarted. Furthermore, s'rg
In (75), it is determined whether the above-mentioned state continues for 4 fields or not based on noise, etc. In order to prevent two fields from restarting the focusing operation, two fields are executed and four fields are merely an example.

On the other hand, when the change detection flag (F2) is in the set state, sTmp (73)l:l- and the focus evaluation value (Xn
) is the maximum evaluation value (XMA ri (= tendency to increase compared to t'-
h v and the direction flag (Fl) are set in state C; the exposure evaluation value is determined to have an increasing tendency C2, or Focus evaluation value (X
n) tends to decrease compared to the maximum evaluation value (XMAX) (:
(and direction) 2g (71) is in the reset state,
The exposure evaluation value tends to decrease in most areas of the screen. is irrelevant and the operating mode code (M
ODI) is kept at 14. C: The focusing operation is not restarted in the next field.

Maku8TEI) (73) (77) l: does not satisfy any of the conditions. In other words, if the focus evaluation value is on an increasing trend but the exposure evaluation value is on a decreasing trend, or vice versa, if the focus evaluation value is on a decreasing trend but the exposure evaluation value is on an increasing trend, the focus evaluation value The change in screen brightness C: is unrelated, and as mentioned above, the operation below 5TIP (75) is executed, and this state continues for 4 fields, and 9 o'clock C: is 5
Focusing operation resumes from the field position. In addition, 5 TEP
(72) 1: When checking the change in the focus evaluation value C: The predetermined value (γ) used should be changed reliably, taking into account the influence of noise etc. This is set as the threshold for recognition as 90%. When any of the above-mentioned routines is executed and the AF routine is completed, the next A11li routine (80) for adjusting exposure is executed.

Next (A based on the exposure evaluation value C calculated as described above)
The exposure adjustment operation performed by the Ie routine will be described in detail. This AE routine is as shown in FIG.
gp(81)+: Initial setting of each variable is done and after 9 (:
, the exposure meter value y(j)(j−1
~6) are preset nine standard values? ) and sTgp (82
)l"- and if the difference between the two is within the allowable range (M), s'rgp (83) (84)l: total evaluation value (Yl) (=added, number of areas (1) This series of operations is performed for all the exposure evaluation values (two, and ends at 611, and the exposure evaluation value Y (9) and STgp (85)C of the sixth sampling area (A6) are added. When it is determined, sTgp (86)
is calculated as total evaluation value (Yt)/number of areas (t).

Differences from the above series of operations (sampling area C where abnormal brightness areas such as high brightness areas such as secondary light sources and low brightness areas such as deep green areas exist: the reference value of the exposure evaluation value?) 0-order C:5TEP (87) (88) where this abnormal brightness part is outside the allowable range (87) (88)
I: is compared with the target value (Q) that provides the optimum exposure, and based on this comparison result C: the iris motor control circuit @c command is issued. Iris motor (7) at 8TEP (89)
If the command is issued and the average value (YAP) is larger than the target value (Q), then BTEP (90)l
Second, a command is issued to rotate the iris motor (7) in the direction of closing the optical diaphragm mechanism (6) because of overexposure, and the reverse C2 average value (YAv) is lower than the target value (Q). If the iris motor (7) is small, s'rgp (91) 1: indicates insufficient exposure, and the iris motor (7) is moved to the optical aperture mechanism (6).
) Opening direction C- Rotation direction I: Command is issued.

Like this (multiple areas on two screens! Divide into two and partially (
: If there is an abnormal brightness area (2), remove it from the calculation of the exposure evaluation value? average value (YAv) of the area where this abnormal brightness area exists (from 2), the abnormal brightness area of the entire screen ≦ It becomes possible to suppress the influence on

As mentioned above, this embodiment 1: Once the focus is reached, 3: Focus evaluation value (if two changes occur, f2, if the subject moves or changes, the focus motor (4) is restarted. ζ At the same time, the brightness level of the captured video signal changes across the entire screen, and the direction of change is the same as the direction of change of the focus evaluation value. In the case (:, the change in the focus evaluation value is not due to the movement or change of the subject, but is due to a change in the brightness of the entire screen. While this state continues, focusing operations are prohibited, and unnecessary focus motor Driving C in (4): The occurrence of an unsightly screen is well prevented. In the first embodiment described above, when it is determined that a change in the focus evaluation value is caused by a change in the brightness of the entire screen, is the operation mode code (Mong) Y”4@C: The focus operation is completely restarted while the object remains fixed. In other words, the predetermined value (γ) is changed to γ++1 (
+1>O) C is increased to prevent resumption of the focusing operation until it is recognized that the focus evaluation value has changed extremely significantly, and the focusing operation is restarted (:<It is also possible to As shown in the second embodiment shown in FIG. S' to judge whether or not
Insert l'1l (200), if it is large, 5TEp
(74) Execute the ninth process of restarting the focusing operation below, and if it is not larger than 5TEP (71) l: set the operation mode code (MODE), 14: fix it and set it to the next field C:. The configuration may be such that the focusing operation is not restarted. In addition, in the flowchart 1 of Figure 2, the 6th
Components that are the same as those in the flowchart in the figure are given the same reference numerals and explanations will be omitted.

By the way, in both of the above-mentioned embodiments, the focus operation is determined by the change in the focus evaluation value accompanying the change in the exposure evaluation value. Regarding the prohibited points, only when the operation mode code (MODE) is "4", that is, the routine up to the apex return routine every t field l: Execute C2, υ, - once in focus state (focus after two consecutive When there is a change in the evaluation value and it is decided to restart the focusing operation, the operation mode code (MODE) is "0° to °3" (if there is, that is, the evaluation value During either the stability confirmation routine or the apex return routine (C: while the focus motor (4) is being driven and the focusing operation is being performed), the exposure evaluation value changes C:
:If the focus evaluation value changes in conjunction, the focusing operation at this point becomes meaningless. Therefore, as a fifth example, the focus evaluation value changes due to the brightness change of the entire screen, and at 9 o'clock, all five routines χ forming the core of the AP screen are skipped and only the Am routine is executed. This will be explained using Figure 8. Incidentally, in FIG. 8, the same parts as those in the above-mentioned embodiment are given the same reference numerals, and the explanation thereof will be omitted.

The exposure evaluation value change direction detection routine (150) is similar to the direction detection routine 61 in FIG. 5, as shown in FIG.
(154) (157) - 2, the subject to which the exposure evaluation value in the current field of each area is compared is the reference exposure evaluation value of each area Exposure evaluation value Yn-1 (1) is used. That is, in 8TRP (152), the exposure evaluation value Y(1) in the current field of the first sampling area (A1) is
is the exposure evaluation value Y n −1(1)(
': It is determined whether the value is greater than the value obtained by adding the allowable value (f), and in sTgp (154), the same comparison is made for the second to m6 sampling areas. Mana, 5TEp
In (153), it is determined whether the exposure evaluation value Y(1) is smaller than the value obtained by subtracting the tolerance value (#) from the exposure evaluation value Yn -1(il) in the previous field, and sTgp (157
), similar comparisons are made for the second to sixth sampling areas C:. This C: The exposure evaluation value in the current field tends to increase from the previous field C: If there is, 5 TEP
The direction flag (F 1) is set at (156),
Decreasing trend C: If there is 5TEP (159)C, the direction flag (Fl is attached and reset.)
P(161)! 2, the change detection flag (F2') is set for most of the screen (in case C: the same tendency occurs in both areas).The exposure evaluation value yn-1 of the previous field in each area is set. (j) (↓-1 to 6) are stored simultaneously when calculating the exposure evaluation value at 5TEPI33.

Next, the direction flag (21') at 5TEEF (100),
Based on the set state C of the change detection flag (F2'), it is determined whether the brightness change of the entire screen is the same as the change direction of the focus evaluation value. The specific C; is as shown in Figure 10 (2) ζ25TEP (172)l: Change detection flag (F2')
When it is determined that the camera is in the reset state, the AP screen is executed as if no brightness change occurred over the entire screen, and even if the change detection flag CF2' is set, the focus evaluation When the value and the exposure meter value are both C: increasing tendency 99 and not recognizing that it is decreasing, the AP screen is executed as the change in the focus evaluation value is not due to the brightness change ζ2. . On the other hand, in case C: there is an increasing trend or a decreasing trend, the change in the focus evaluation value is due to a brightness change ≦ 2 and is not due to movement or change of the subject, and the AF routine (133) is skipped. , AE series is executed.

The AF routine (133) is the AF routine (to) in Figure 3.
It consists of five core routines. However, the evaluation value fluctuation monitoring routine (149) is executed as shown in FIG. When C2 only, the operating mode code (MODE) is 0.
1.C: Action to change? It is configured to do this.

In the above-mentioned embodiment, when the brightness level of the imaged video signal increases, the high-frequency component level also increases accordingly. : When the brightness level is high [= means that if the brightness level increases, the high frequency component level may decrease. At this time, [: means ÷ S ÷ S, gp (73) (17
3) - Not necessarily Xn>XMAX and F1=1, F
Although the condition j′=1 is not satisfied, the focusing operation must be regulated.

Therefore, when the brightness level of the C2 imaged video signal is high enough to cause this saturation, C: does not satisfy the above conditions and the single C
As soon as F2-1-1 is judged as F2=1 (=5rEp (71) in the first embodiment, 5rEp in the second embodiment)
TEP (200), 5TEP (30
) is configured to execute. By the way, the ninth step in detecting that the brightness level is high enough to cause bright spots is when calculating the exposure meter value (: Add up the exposure evaluation values of all areas and check that it is higher than the preset threshold level. (g) Effect of the invention Since the present invention is configured as described above, fluctuations in external light and aperture τ
= Focus evaluation value 1 due to the brightness change of the entire screen caused by
: Even if a change occurs, the focusing operation is prohibited, and unnecessary focus motor drive (unsightly screen projection due to unnecessary focus motor drive) is prevented.

Orcus motor control circuit (focus control means), α6
1αη·-can... Integration circuit (luminance level detection means).

Claims (1)

[Claims] (1) a focus evaluation value detection means for outputting a high-frequency component level of a captured video signal obtained from an image sensor as a focus evaluation value at regular intervals; A focus control unit that executes a focusing operation to control the distance to the image sensor; and a brightness level detection unit that detects the brightness level of the captured video signal in a plurality of areas set by dividing the imaging screen, An imaging apparatus characterized in that when temporal changes in brightness levels of the respective areas have the same directionality, the focusing operation by the focus control means is restricted.