JP2006064855A - Automatic focusing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing device capable of adjusting a focusing position at a high speed while keeping certain precision. <P>SOLUTION: The automatic focusing device is equipped with a line exposure type imaging element (CMOS image sensor) which converts an optical image formed through a focus lens into an image signal, a lens drive section which moves the focus lens along the optical axis, an AF detection section which calculates an AF evaluated value based upon an image signal of an evaluation region previously set in an imaging region obtained by the imaging element, an exposure time calculating means of calculating the shortest exposure time T<SB>exp</SB>such that an exposure period of the evaluation region does not overlap a drive period of the focus lens based upon a time corresponding to the vertical width of the evaluation region and a drive time T<SB>m</SB>of the focus lens needed for one frame of the imaging region, and a control section which controls the imaging element and lens drive section according to the calculated shortest exposure time T<SB>exp</SB>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an automatic focus adjustment apparatus in an imaging apparatus that images a subject and outputs an image signal.

  In recent years, imaging apparatuses such as digital cameras and digital video cameras using an imaging element have been widely used. Along with this, multi-functionalization has progressed, and there are imaging devices equipped with automatic focus adjustment devices.

  In general, the focus adjustment by the automatic focus adjustment device is performed as follows. First, an imaging lens is moved, an image signal output from a charge storage type image sensor is acquired, and an automatic focus adjustment evaluation value (hereinafter, referred to as “detection”) obtained by detecting contrast (or high frequency component) from the obtained image signal. AF (Auto Focus) evaluation value) is calculated. Then, an appropriate lens position (focus position) is derived based on the calculated AF evaluation value, and the photographing lens is moved to that lens position to adjust the focus.

  As an example of such an automatic focus adjustment device, conventionally, the photographing lens is moved for each exposure field, and based on the detection of exceeding the peak of the focus degree information extracted from the video output signal of the image sensor for each field period. An automatic focusing device is disclosed that calculates a target value corresponding to a focal position and performs focusing driving based on the target value (see Patent Document 1).

However, since the adjustment operation of the in-focus position is a loop control, there is a disadvantage that the follow-up speed is slow. Therefore, as an automatic focus adjustment device that detects the in-focus position early, while moving the lens continuously in one direction between the infinity end and the closest end, in the lens movement range corresponding to the set exposure time An automatic focus adjustment device that detects the maximum value of sharpness output for each scanning line and moves the lens with the lens position of the peak value of the obtained maximum value as the focus position is disclosed (Patent Document 2). reference.)
Japanese Patent No. 3103579 Japanese Patent No. 3232566

  At present, CCD (Charge Coupled Devices) image sensors are widely used as image sensors used in image pickup devices. However, in recent years, various circuits such as noise removal circuits of CMOS (Complementary Metal Oxide Semiconductor) image sensors have been improved. As the sensitivity increases, CMOS image sensors that are advantageous in terms of low power consumption, small size, light weight, and system-on-chip are beginning to be adopted.

  The CCD image sensor is a global exposure that maintains the synchronism of storing signal charges by photoelectrically converting all the pixels in the imaging region during the same period. Therefore, when adjusting the in-focus position using the CCD image sensor, the entire CCD image sensor is exposed at the same time, and then the exposure is completed at the same time. At the end of the exposure, the charge accumulated in each pixel is read out. Therefore, the exposure periods of the frames do not overlap, and it is easy to perform AF evaluation separately for driving of the taking lens and exposure.

  On the other hand, in the COMS image sensor, since the accumulation period of the pixel column for each scanning line is synchronized with the signal output timing, the exposure start time is shifted for each scanning line, and the signal charge accumulation can be maintained simultaneously. Line exposure (rolling shutter) is not possible. Therefore, when adjusting the in-focus position using the COMS image sensor, a difference occurs in the exposure start time for each scanning line. When the exposure time is long, the exposure period overlaps between the previous and subsequent frames. End up.

  When Patent Document 1 is applied to an imaging apparatus using a CMOS image sensor, if the exposure time is long, the exposure period of each frame overlaps, and the AF evaluation is performed separately for the movement of the photographing lens and the exposure. I can't. In the case of Patent Document 2, since the lens is moved from the infinite end to the closest end during one frame and the AF evaluation is performed for each scanning line, the AF evaluation is performed when the image stored in one frame is not uniform. This is not possible and cannot be applied when there are a plurality of subjects in one screen such as outdoors, so that it is difficult to put it into practical use.

  Therefore, the adjustment of the in-focus position using the COMS image sensor is performed by alternately moving the photographic lens and exposing every other frame (two frame periods), and exposing the image signal while the movement of the photographic lens is stopped. It is conceivable to adjust the in-focus position where AF evaluation is performed using. However, since AF evaluation is performed in a cycle of two frames, there is a problem that a processing time required to complete the adjustment of the in-focus position becomes long and a photo opportunity is missed.

  An object of the present invention is to realize an automatic focus adjustment device capable of adjusting a focus position at high speed while maintaining a certain accuracy.

  The invention according to claim 1 is provided so as to be movable in the direction of the optical axis, and optical means for forming an optical image of a subject, and an optical image formed through the optical means is converted into an image signal. Line exposure type imaging means, driving means for moving the optical means in the optical axis direction, and based on image signals in the evaluation area preset in the imaging area obtained by the imaging means, the optical means Evaluation value calculation means for calculating an automatic focus adjustment evaluation value for evaluating the position in the optical axis direction, time corresponding to the vertical width of the evaluation area, and driving time of the optical means required for one frame of the imaging area An exposure time calculation means for calculating a minimum exposure time in which an exposure period in the evaluation region and a drive period of the optical means do not overlap, and the imaging means and the drive means based on the calculated minimum exposure time It is characterized in that an automatic focusing device and a control means for controlling.

  According to a second aspect of the present invention, in the automatic focus adjustment apparatus according to the first aspect, when the calculated minimum exposure time is underexposure, the amplification unit performs amplification adjustment of the image signal output from the imaging unit. It is characterized by having.

  According to a third aspect of the present invention, there is provided the automatic focus adjustment apparatus according to the first or second aspect, further comprising a light amount adjusting means for adjusting a light flux amount when the calculated minimum exposure time is insufficient. It is a feature.

  The invention according to claim 4 is provided so as to be movable in the direction of the optical axis, and optical means for forming an optical image of a subject, and an optical image formed through the optical means is converted into an image signal. Line exposure type imaging means, driving means for moving the optical means in the optical axis direction, and based on image signals in the evaluation area preset in the imaging area obtained by the imaging means, the optical means Evaluation value calculation means for calculating an automatic focus adjustment evaluation value for evaluating the position in the optical axis direction, and automatic focus adjustment calculated from the calculation means while moving the optical means at a constant speed in one direction in the optical axis direction A first evaluation operation for detecting the maximum value of the evaluation value, and a second evaluation operation for adjusting the in-focus position based on the maximum value of the automatic focus adjustment evaluation value detected from the first evaluation operation. Control means to perform, It is characterized in that an automatic focusing device was e.

  According to a fifth aspect of the present invention, in the automatic focus adjustment apparatus according to the fourth aspect, the control unit performs the first evaluation operation with respect to a maximum value of the detected automatic focus adjustment evaluation value. It is characterized in that the position of the optical means at the exposure start time of the upper limit scanning line in the automatic focus adjustment evaluation region and the position of the optical means at the exposure end time of the lower limit scanning line are detected and stored.

  According to a sixth aspect of the present invention, in the automatic focus adjustment apparatus according to the fifth aspect, the control unit performs the second evaluation operation with respect to a maximum value of the detected automatic focus adjustment evaluation value. A first distance is calculated as a distance from the position of the optical means at the exposure start time of the upper limit scanning line of the automatic focus adjustment evaluation area to the position of the optical means at the exposure end time of the lower limit scanning line, and the first distance is calculated. If it is within the depth of focus, the position of the optical means with respect to the maximum value of the automatic focus adjustment evaluation value calculated in the first evaluation operation is adjusted as a focus position.

  According to a seventh aspect of the present invention, in the automatic focus adjustment apparatus according to the sixth aspect, when the control unit performs the second evaluation operation, if the first distance is not within the depth of focus, the optical unit Is moved at intervals of two frame periods in the opposite direction to the first evaluation operation, and the automatic focus adjustment evaluation value calculated from the calculation means is the value of the automatic focus adjustment evaluation value calculated from the first evaluation operation. It is characterized in that a position that is equal to or greater than a target value calculated based on the maximum value is adjusted as a focus position.

  According to the first aspect of the present invention, by calculating and setting the minimum exposure time, the exposure time of the evaluation frame in the evaluation region does not overlap with the exposure time of the evaluation frame in the previous and subsequent frames. Since a period for moving the optical means can be provided between the exposure period of the adjustment value area, an image signal can be obtained without any movement of the optical means during the exposure period of the evaluation area, and a certain accuracy can be obtained. The focus position can be adjusted at high speed while maintaining the above.

  According to the second or third aspect of the invention, the same effect as that of the first aspect can be obtained, but also the underexposure can be solved with an easy configuration, and the contrast of the obtained image signal is lowered. Can be reduced.

  According to the invention described in claim 4, by performing the first evaluation operation and the second evaluation operation, it is possible to detect the in-focus position standard, and the optical means based on the in-focus position standard. Therefore, the processing time required to complete the adjustment of the in-focus position can be shortened, and the in-focus position can be adjusted at high speed while maintaining a certain accuracy.

  According to the fifth aspect of the invention, the same effect as in the fourth aspect can be obtained, and the position of the optical means with respect to the maximum value of the automatic focus adjustment evaluation value can be easily calculated.

  According to the sixth aspect of the invention, it is possible to obtain the same effect as that of the fifth aspect. In addition, when the first distance is within the depth of focus, the optical means detects the automatic focus instantaneously. The position of the optical means can be adjusted with respect to the maximum value of the adjustment evaluation value.

  According to the seventh aspect of the invention, it is possible to obtain the same effect as that of the sixth aspect. In addition, the focus position is adjusted based on the image signal in a state where there is no movement of the optical means during the exposure period. And the accuracy of adjusting the in-focus position can be improved.

[Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to the drawings.
First, the configuration will be described.
FIG. 1 shows a block diagram of a schematic configuration of the automatic focusing apparatus A according to the first embodiment.

  The automatic focusing apparatus A includes an imaging optical system 1, an aperture 2, an imaging device 10 as an imaging unit, a timing signal generation unit 20, an A / D conversion / amplification unit 30, an AF detection unit 40 as an evaluation value calculation unit, an aperture A drive unit 50, a lens position detection unit 60, a lens drive unit 70 as a drive unit, and a control unit 100 as a control unit are provided.

  The imaging optical system 1 is provided so as to be movable in the optical axis direction, and includes a focus lens 1a as an optical unit for forming an optical image of a subject.

  The diaphragm 2 is a light amount adjusting unit that adjusts the amount of the light beam transmitted through the imaging optical system 1.

The image sensor 10 is a line exposure type (rolling shutter) CMOS image sensor, which converts an optical image of a subject formed on the light receiving surface by the imaging optical system 1 into an electrical signal, and converts the converted analog image. The signal is output to the A / D converter / amplifier 30.
The image sensor 10 will be described with reference to FIGS.

In FIG. 2, the schematic block diagram of the image pick-up element 10 is shown.
As shown in FIG. 2, the image sensor 10 includes a photoelectric conversion unit 11, a readout vertical shift register 12, a reset vertical shift register 13, a horizontal shift register 14, and an output amplifier 15.

  The read shift register 12 performs address designation for reading the signal charges photoelectrically converted by the photoelectric conversion unit 11 for each horizontal pixel column (scanning line). The reset serial shift register 13 performs addressing for resetting signal charges accumulated in each pixel for each horizontal pixel column (scanning line). The horizontal shift register 14 horizontally transfers the signal charges photoelectrically converted by the photoelectric conversion unit 11 for each horizontal pixel column.

FIG. 3 shows a partially enlarged view of the image sensor 10.
The photoelectric conversion unit 11 is connected to a plurality of unit pixel circuits 80 arranged two-dimensionally, a plurality of vertical scanning lines 81 connected to the readout vertical shift register 12, and a reset vertical shift register 13. a plurality of reset scan line 82, and a vertical signal line 83 are connected to the horizontal shift register 14 and the output signal line 84 via the horizontal switch transistor M _L.

Each unit pixel circuit 80 includes a photodiode PD, an amplifier M _A , a selection transistor M _S connected to the vertical scanning line 81 and the vertical signal line 83, a reset transistor M _R connected to the reset scanning line 82, and the like. .

The signal charges photoelectrically converted by the photodiode PD is replaced with the voltage change of the photodiode PD, it is amplified by an amplifier M _A. When a selection pulse is sequentially applied from the readout vertical shift register 12 to the vertical scanning line 81, the selection transistor M _S connected to the vertical scanning line 81 to which the selection pulse is applied is turned ON, and the amplifier M _A The amplified signal charge is read out to the vertical signal line 83 through the selection transistor M _S. Then, when sequentially selecting pulse from the horizontal shift register 14 to the horizontal switch transistor M _L is printed, the signal charges on the vertical signal line 83 is read out sequentially the output signal line 84.
Further, when the reset pulse from the reset vertical shift register 13 is applied to the reset scan line 82, the reset transistor M _R is ON, the signal charge of the photodiode PD is reset.

The timing signal generator 20 drives various readout vertical shift registers 12, reset vertical shift registers 13, and horizontal shift registers 14 of the image sensor 10 based on an exposure time instruction signal S _Texp input from the controller 100. A timing signal is generated and output to the image sensor 10. In addition, a read timing signal S _V used to distinguish the image signals of each frame is output to the control unit 100.

The A / D conversion / amplification unit 30 performs A / D conversion means for converting an analog image signal input from the image sensor 10 into a digital image signal, and performs amplification adjustment (gain increase) on the converted image signal S _i. Amplifying means. The analog image signal input from the image sensor 10 may be amplified and adjusted and then converted to a digital signal.

The AF detection unit 40 calculates an AF evaluation value (automatic focus adjustment evaluation value) from an AF evaluation region, which will be described later, based on the image signal S _i obtained by the image sensor 10 and input from the A / D conversion / amplification unit 30. When the calculation of the AF evaluation value is completed for each frame, the AF detection processing completion signal is output to the control unit 100. Further, on the basis of the AF evaluation value signal read from the control unit 100 outputs an AF evaluation value signal S _AF indicating the calculated AF evaluation value to the control unit 100.

The AF detection unit 40 includes a gate circuit unit 41, a BPF (Band Pass Filter) 42, and an integration unit 42. The gate circuit 41, the region becomes an AF evaluation target from the image signals S _i (AF evaluation area as an evaluation region) is set based on the AF evaluation area indication signal S _w which is input from the control unit 100. The BPF 42 extracts a signal component in a predetermined frequency band in the high frequency region. The integrating unit 43 integrates the signal input from the BPF 42 and calculates an AF evaluation value.

  The aperture driving unit 50 drives the aperture 2 based on a signal from the control unit 100.

The lens position detection unit 60 detects the position of the focus lens 1 a and outputs the detected lens position signal _SP to the control unit 100.

The lens driving unit 70 outputs a lens driving signal S _m for driving a lens driving motor (not shown) based on the lens driving instruction signal S _m0 input from the control unit 100, and moves the focus lens 1a in the optical axis direction. Move.

The lens driving unit 70 moves the focus lens in units of the minimum moving distance (hereinafter referred to as “one step movement”). For example, the lens driving unit 70 moves the focus lens 1a by several steps based on the lens drive instruction signal S _m0 .
As the lens driving motor, it is preferable to use a motor with high positioning accuracy such as a stepping motor or a DC motor.

  The control unit 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU reads out the program and data stored in the ROM and executes the program and data on the RAM. Thus, the overall operation of the automatic focus adjustment apparatus A is comprehensively controlled.

The control unit 100 according to the first embodiment performs each frame based on the frame period T _f , the AF evaluation area W _AF , the driving time of the focus lens 1 a required for one frame (lens driving time T _m ), and the readout timing signal S _V. A timer for measuring the exposure start time of the AF upper limit scanning line and the exposure end time of the AF lower limit scanning line, which will be described later, and the minimum exposure time T so as not to overlap the exposure period of the AF evaluation area W _AF and the driving period of the focus lens 1a. has an exposure time calculation means for calculating _exp, after the minimum exposure time T _exp calculated outputs the exposure time indication signal S _Texp instructing the timing signal generating circuit 20, an image signal of the AF evaluation area W in _{the AF} A program and various data for performing AF evaluation and adjusting the in-focus position are preset and stored in the ROM. In addition, when the exposure amount is insufficient for the calculated minimum exposure time T _exp , the control unit 100 instructs the aperture driving unit 50 to operate the aperture 2 to the open side, or performs A / D conversion / amplification. Instructing the image signal amplification adjustment (gain increase) in the unit 30.

FIG. 4 shows an example of the AF evaluation area _WAF .
In general, the idea that the subject the user wants take is near the center of the frame area W _F as an imaging area, AF evaluation area W _AF is set in the center of the frame area W _F.
Frame area W _F is a region surrounded by the scanning lines of the m columns of the uppermost scanning line (first scanning line L _W1) from the bottom of the scanning line (the m scanning lines L _Wm).

AF evaluation area W _AF, relative to a plurality of scan lines columns that are arranged in the vertical direction of the frame area W _F, s-th from the first scan line L _W1 of the s scanning lines (AF upper scanning line) L _Ws and vertical ranging e th e scan lines (AF lower scanning lines) L _We from the first scan line L _W1 from to a plurality of pixels that are arranged in the water direction of the frame area W _F This is a two-dimensional region consisting of a horizontal range from, for example, the nth pixel to the xth pixel at one end in the horizontal direction.

The control unit 100 calculates the vertical width (number of vertical scanning lines) L _AF of the AF evaluation area W _AF from the difference between the AF lower limit scanning line L _We and the AF upper limit scanning line L _Ws using, for example, the following (Formula 1). To do.

L _AF = L _We -L _Ws (Formula 1)

Control unit 100, required for the preset frame period T _f, AF evaluation area W _AF vertical width L _AF, vertical scan line the total number m, 1 frame frame area W _F calculated from the AF evaluation area W _AF From the lens driving time T _m , the minimum exposure time _Texp is calculated using the following (Formula 2).

(1- _LAF / m) * _Tf - _Tm > _Texp (Formula 2)

FIG. 5 shows the relationship between the position of the focus lens 1a and the AF evaluation value.
When the focus lens 1a is sequentially moved to the lens positions P ₁ , P ₂ ,... P _m in the direction from the infinite end to the closest end (positive direction), _AF from the AF evaluation area WAF at each lens position evaluation image F _1, F ₂ ···· F _m is obtained, AF evaluation values V _1, V ₂ ···· V _m is calculated for each lens position. When the position of the focus lens 1a is taken on the horizontal axis and the AF evaluation value is taken on the vertical axis, the shape becomes a mountain shape. The calculated AF evaluation value increases as the obtained image is clearer (the degree of focus is higher). For example, the calculated AF evaluation value is calculated when the AF evaluation image for the lens position _Pn is the clearest image. The AF evaluation value V _n is a numerical value larger than other AF evaluation values.

  The control unit 100 detects the maximum value (peak AF evaluation value) from the AF evaluation values calculated for each of a plurality of lens positions, and focuses on the lens position with respect to the target value (target AF evaluation value) based on the peak AF evaluation value. The focus position is adjusted by adjusting the lens 1a.

Control unit 100, when detecting a peak AF evaluation value, for example, the focus lens 1a in one direction (e.g., positive direction) is moved at a time M steps between each frame, the lens from the AF evaluation value V _n of the lens position P _n When the value obtained by subtracting the AF evaluation value V _{n + 1} when the position is P _{n + 1} becomes larger than a predetermined threshold value, it is determined that the peak AF evaluation value is detected. Then, the focus lens 1a is moved in the reverse direction (for example, the direction from the closest end to the infinite end (negative direction)) by N steps between frames from the lens position at which the peak AF evaluation value is determined to be detected. When the AF evaluation value thus obtained is equal to or greater than the target AF evaluation value, the focus lens 1a is adjusted to the lens position with respect to the detected AF evaluation value.

  The target AF evaluation value is calculated based on the detected peak AF evaluation value and the depth of focus after the peak AF evaluation value is detected.

  The number of drive steps N of the focus lens 1a after the peak AF evaluation value is detected is smaller than the number of drive steps M before the maximum AF evaluation value is detected. The focus position adjustment accuracy is improved.

  The lens position of the focus lens 1a adjusted in this way is within the focal depth of the lens position with respect to the AF evaluation value determined to be the peak AF evaluation value, and a certain accuracy can be ensured.

  Although the control unit 100 is described as a control unit unique to the automatic focus adjustment apparatus A, when the automatic focus adjustment apparatus A is provided in an imaging apparatus or the like, the control unit 100 is included in the control unit that controls the entire imaging apparatus. May be.

Next, the operation of the first embodiment will be described.
The operation described below is executed by the control unit 100 which is the control means of the present invention.

FIG. 6 shows an operation flow for setting the minimum exposure time T _{exp in} the first embodiment.
Control unit 100, if the instruction to perform automatic focus adjustment is input, sets the AF evaluation area W _AF gate circuit 41 (step S1).

Control unit 100, after setting the AF evaluation area W _AF gate circuit 41, calculates the minimum exposure time T _exp (step S2).

After calculating the minimum exposure time T _exp , the control unit 100 _measures the brightness of the subject (step S3) and calculates the appropriate exposure time T _exp0 (step S4).

The control unit 100 determines whether or not the appropriate exposure time T _exp0 is equal to or shorter than the minimum exposure time T _exp (step S5). When it is determined that the minimum exposure time T _exp is longer than the appropriate exposure time T _exp0 (step S5; No), it is determined that the light flux amount is insufficient, and a gain increase amount for eliminating the under exposure is calculated. (Step S6).

When determining that the appropriate exposure time T _exp0 is equal to or shorter than the minimum exposure time T _exp (step S5; Yes), the control unit 100 sets the gain increase amount to “0” (no amplification adjustment) (step S7).

The control unit 100 outputs a gain adjustment instruction signal _SG to the A / D conversion / amplification unit 30 based on the calculated gain increase amount (step S8).

Control unit 100 outputs an exposure time indication signal S _Texp instructing minimum exposure time T _exp calculated for the timing signal generator 20, to set the minimum exposure time T _exp (step S9).

  Although the method for adjusting the gain increase amount has been described as a measure for eliminating the underexposure, the underexposure may be resolved by adjusting the aperture amount of the aperture 2, and the gain increase amount and the aperture amount are adjusted. May be.

FIG. 7 shows a flow for adjusting the in-focus position according to the first embodiment.
After the setting operation of the minimum exposure time T _exp shown in FIG. 6 is completed, the control unit 100 initializes the peak AF evaluation value (step S11) and sets the moving direction of the focus lens 1a to the positive direction (step S12).

The control unit 100 determines whether or not the exposure of the AF lower limit scanning line L _We has been completed by measuring the timer based on the read timing signal S _V (step S13), and the exposure of the AF lower limit scanning line L _We is completed. (Step S13; No).

When the control unit 100 determines that the exposure of the AF lower limit scanning line L _We has been completed (step S13; Yes), the control unit 100 moves the focus lens 1a by M steps (step S14).

  In order to determine whether or not the AF detection processing of the AF detection unit 40 is completed, the control unit 100 determines whether or not an AF detection processing completion signal is input from the AF detection unit 40 (step S15), and AF detection is performed. Wait until a processing completion signal is input (step S15; No).

  When it is determined that the AF detection processing completion signal is input (AF detection processing completion) (step S15; Yes), the control unit 100 reads the AF evaluation value from the AF detection unit 40 and acquires the AF evaluation value (step S16). ).

  The control unit 100 determines whether or not the acquired AF evaluation value is larger than the peak AF evaluation value (step S17). When it is determined that the acquired AF evaluation value is larger than the peak AF evaluation value (step S17; Yes), the acquired AF evaluation value is updated to the peak AF evaluation value, and the peak AF evaluation value is updated (step S18). ).

  When it is determined that the acquired AF evaluation value is equal to or less than the peak AF evaluation value (step S17; No) or after the update process of the peak AF evaluation value is completed (after step S18), the control unit 100 determines that the acquired AF evaluation value is In order to determine whether or not the peak AF evaluation value has dropped significantly, it is determined whether or not a value obtained by subtracting the AF evaluation value from the peak AF evaluation value is greater than a preset threshold value (step S19).

  When the control unit 100 determines that the value obtained by subtracting the AF evaluation value from the peak AF evaluation value is equal to or less than a preset threshold value (step S19; No), the control unit 100 returns to step S13.

  When the controller 100 determines that the value obtained by subtracting the AF evaluation value from the peak AF evaluation value is larger than a preset threshold value (step S19; Yes), the control unit 100 sets the moving direction of the focus lens 1a to the negative direction. (Step S20).

The control unit 100 determines whether or not the exposure of the AF lower limit scanning line L _We has ended by counting the timer based on the read timing signal S _V (step S21). Wait until the exposure of the AF lower limit scanning line L _We is completed (step S21; No).

When the control unit 100 determines that the exposure of the AF lower limit scanning line L _We has been completed (step S21; Yes), the control unit 100 moves the focus lens 1a by N steps (step S22).

  In order to determine whether or not the AF detection processing of the AF detection unit 40 is completed, the control unit 100 determines whether or not an AF detection processing completion signal is input from the AF detection unit 40 (step S23), and AF detection is performed. Wait until a processing completion signal is input (step S23; No).

  When determining that the AF detection processing completion signal has been input (AF detection processing completed) (step S23; Yes), the control unit 100 reads the AF evaluation value from the AF detection unit 40 and acquires the AF evaluation value (step S24). ).

  The control unit 100 determines whether or not the acquired AF evaluation value is greater than or equal to the target AF evaluation value (step S25). When it is determined that the acquired AF evaluation value is not equal to or higher than the target AF evaluation value (step S25; No), the process returns to step S21.

  When it is determined that the acquired AF evaluation value is equal to or greater than the target AF evaluation value (step S25; Yes), the control unit 100 ends the focus position adjustment operation.

FIG. 8 shows an example of a timing chart of the first embodiment.
The frame period T _f is a period from the falling time of the readout timing signal S _V to the next falling time, and the lens driving signal S _m , the charge accumulation signal of each scanning line, the image signal S _i , and the AF evaluation. The value signal _SAF is schematically shown.

At time t1, the exposure of the AF lower limit scanning line L _We with respect to the initial lens position P ₀ is completed, and from time t1 to time t2, the focus lens 1a is moved M steps by the lens drive signal S _m (for example, focus) lens 1a is moved from the initial lens position P ₀ to the lens position P _a moved M step.).
At time t2, the exposure of the AF upper scanning line L _Ws to the lens position P _a is started.

Further, after the focus lens 1a is started M step movement (after time t1), is obtained AF evaluation value V ₀ is the initial lens position P _0, the peak AF evaluation value based on the AF evaluation value V ₀ obtained Detection operation is performed.

Time Time t3 to t2, the lens position P _a AF evaluation area W AF lower scanning lines from AF upper scanning line L _Ws of _AF L _We respect is exposed.

When the time t3, the exposure of the AF lower scanning line L _We with respect to the lens position P _a is terminated, from time t3 to time t4, the focus lens 1a is moved M-step by the lens driving signal S _m (e.g., focus lens 1a is It is moved from the lens position P _a to the lens position P _{b that} has been moved M steps).

Further, after the focus lens 1a is started M step movement (after time t3), it is acquired AF evaluation value V _a of the lens position P _a is the peak AF evaluation value based on the obtained AF evaluation value V _a A detection operation is performed.
Thus, the peak AF evaluation value detection operation is performed while repeating the above operation.

At time t11, the exposure of the AF lower limit scanning line L _{We to} the lens position P _nM is finished, and from time t11 to time t12, the focus lens 1a is moved M steps by the lens drive signal S _m (for example, the focus lens). 1a is moved to the lens position P _{n which} has moved M steps from the lens position P _nM .)
At time t12, exposure of the AF upper limit scanning line L _Ws with respect to the lens position P _n is started.

After the focus lens 1a is started M step movement (after time t11), the acquired AF evaluation value V _nM at the lens position P _nM, detection operation of the peak AF evaluation value based on the obtained AF evaluation value V _nM Is done.

From time t12 to time t13, the AF lower limit scanning line L _We is exposed from the AF upper limit scanning line L _Ws of the AF evaluation area W _{AF with} respect to the lens position P _n .

At time t13, the exposure of the AF lower limit scanning line L _We with respect to the lens position P _n is completed, and the focus lens 1a is moved M steps by the lens drive signal S _m from time t13 to time t14 (for example, the focus lens 1a is moved). is moved from the lens position P _n in the M-step movement and lens position P _{n + M.).}

Further, after the focus lens 1a is started M step movement (time after t13), the acquired AF evaluation value V _n at the lens position P _n, the peak AF evaluation value based on the obtained AF evaluation value V _n A detection operation is performed. When the acquired AF evaluation value V _n is determined to be the peak AF evaluation value, the lens moving direction is set to the negative direction.

  After the lens movement direction is set to the negative direction, the focus lens 1a is moved N steps in the negative direction, and when the detected AF evaluation value is equal to or greater than the target AF evaluation value, the lens corresponding to the detected AF evaluation value The timing chart is omitted because it is substantially the same except that the focus lens 1a is adjusted to the position.

Thus, by setting calculates the minimum exposure time T _exp, during the exposure period of the AF evaluation area W _AF does not overlap with the AF evaluation area W exposure period of _AF before and after the frame, the front and rear frame AF it is possible to provide a period for moving the lens between the exposure period evaluation region W _AF, during the exposure period of the AF evaluation area W _AF can obtain an image signal in a state the mobile is not the focus lens 1a The focus position can be adjusted at high speed while maintaining a certain accuracy.

[Embodiment 2]
Hereinafter, the second embodiment of the present invention will be described in detail with reference to the drawings.
First, the configuration will be described.
FIG. 9 is a block diagram showing a schematic configuration of the automatic focusing apparatus B according to the second embodiment.
In the configuration of the automatic focus adjustment apparatus B according to the second embodiment, the same reference numerals are given to the same portions as those in the first embodiment, and detailed description will be omitted, and only different portions will be described. Specifically, the control unit 100 in the first embodiment is the control unit 200.

  The control unit 200 includes a CPU, a ROM, a RAM, and the like, and the CPU reads out programs and data stored in the ROM, develops them in the RAM, and executes them, whereby the overall operation of the automatic focus adjustment device B is comprehensively performed. Control.

The control unit 200 according to the second embodiment performs exposure start time and AF lower limit of the AF upper limit scanning line L _Ws of each frame based on the frame period T _f , the AF evaluation area W _AF as the evaluation area, and the readout timing signal S _V. A timer for measuring the exposure end time of the scanning line L _We , a first evaluation operation for detecting the peak AF evaluation value as the maximum value of the automatic focus adjustment evaluation value while moving the focus lens 1a at a constant speed in one direction And a program and various data for performing the second evaluation operation for adjusting the lens position (focus position) of the focus lens 1a based on the peak AF evaluation value detected from the first evaluation operation are preset. Stored in the ROM.

In the first evaluation operation, the focus lens 1a is moved in one direction (for example, the positive direction) between the infinite end and the close end at a constant speed while acquiring image signals of a plurality of frames. An AF evaluation value is calculated for the AF evaluation area W _AF , and the focus lens 1a is moved until a peak AF evaluation value is detected from the calculated plurality of AF evaluation values.

In the first evaluation operation, the lens position (upper limit lens position) of the focus lens 1a and the exposure end time of the AF lower limit scanning line L _We at the exposure start time of the AF upper limit scanning line L _Ws in the AF evaluation area W _AF of each frame. The lens position (lower limit lens position) of the focus lens 1a is detected and stored, and the focus lens 1a is detected at the exposure start time of the AF upper limit scanning line L _Ws of the AF evaluation area W _{AF with} respect to the detected peak AF evaluation value. The lens position (peak upper limit lens position) and the lens position (peak lower limit lens position) of the focus lens 1a at the exposure end time of the AF lower limit scanning line L _We are stored.

In the first evaluation operation, since the focus lens 1a is moved during the exposure period of each frame, the lens position is different between the AF upper limit scanning line L _Ws and the AF lower limit scanning line L _{We in the} AF evaluation area W _AF . The lens position for each AF evaluation value calculated in the first evaluation operation can be approximated to an intermediate position between the upper limit lens position and the lower limit lens position of the calculated AF evaluation value.

  The second evaluation operation is performed when the first distance as the distance from the peak upper limit lens position to the peak lower limit lens position of the peak AF evaluation value detected from the first evaluation operation is within the depth of focus. The focus lens 1a is adjusted to the lens position (peak lens position) with respect to the peak AF evaluation value detected from the operation.

Further, in the second evaluation operation, when the first distance is not within the depth of focus, the first evaluation operation starts in the reverse direction (for example, the negative direction) from the time when the focus lens 1a is stopped in the first evaluation operation. the focus lens 1a of the acquired image signals by moving N step by step at intervals of two frame periods, the target AF evaluation value or more as the AF evaluation area W has been AF evaluation value is the target value obtained for _AF of each frame In this case, the focus lens 1a is adjusted to the lens position with respect to the acquired AF evaluation value.

  The target AF evaluation value is calculated based on the peak AF evaluation value and the depth of focus detected from the first evaluation operation.

  The lens position of the focus lens 1a adjusted in this way is within the focal depth of the lens position with respect to the peak AF evaluation value detected from the first evaluation operation, and a certain accuracy can be ensured.

Since the concept of the AF evaluation area W _AF and the relationship between the position of the focus lens 1a and the AF evaluation value are the same as those in the first embodiment, illustration and description are omitted.

  The control unit 200 will be described as a control unit unique to the automatic focus adjustment device B. However, when the automatic focus adjustment device B is provided in an imaging device or the like, the control unit 200 is included in the control unit that controls the entire imaging device. May be.

Next, the operation of the second embodiment will be described.
The operation described below is executed by the control unit 200 which is the control means of the present invention.

FIG. 10 shows an operation flow of the first evaluation operation in the second embodiment.
When instructed to perform automatic focus adjustment, the control unit 200 initializes the peak AF evaluation value, the peak upper limit lens position, and the peak lower limit lens position (step S31), and moves the focus lens 1a in one direction (for example, normal The lens driving instruction signal S _m0 is output to the lens driving unit 70 so as to move at a constant speed in the direction (step S32).

The control unit 200 detects the upper limit lens position and the lower limit lens position of each frame and stores them in the RAM (step S33).
Note that step S33 is processed by an interrupt process or the like.

  The control unit 200 determines whether or not an AF detection processing completion signal is input from the AF detection unit 40 in order to determine whether or not the AF detection processing of the AF detection unit 40 is completed (step S34), and AF detection is performed. Wait until a processing completion signal is input (step S34; No).

Control unit 200, AF detection processing completion signal is inputted when it is determined that (AF detection processing completed) (step S34; Yes), the AF evaluation value from the AF evaluation value signal S _AF inputted from the AF detection unit 40 Obtain (step S35).

  The control unit 200 determines whether or not the acquired AF evaluation value is larger than the peak AF evaluation value (step S36). When it is determined that the acquired AF evaluation value is larger than the peak AF evaluation value (step S36; Yes), the acquired AF evaluation value is updated to the peak AF evaluation value, and the upper limit lens position and the lower limit lens with respect to the acquired AF evaluation value Update processing for updating the position as the peak upper limit lens position and the peak lower limit lens position is performed (step S37).

  When it is determined that the acquired AF evaluation value is equal to or less than the peak AF evaluation value (step S36; No), the control unit 200 completes the update processing of the peak AF evaluation value, the peak upper limit lens position, and the peak lower limit lens position (step S36). After S37), whether or not the value obtained by subtracting the AF evaluation value from the peak AF evaluation value is greater than a preset threshold value in order to determine whether or not the acquired AF evaluation value has fallen greatly than the peak AF evaluation value It is determined whether or not (step S38).

  When it is determined that the value obtained by subtracting the AF evaluation value from the peak AF evaluation value is equal to or less than a preset threshold value (step S38; No), the control unit 200 returns to step S33.

  If the control unit 200 determines that the value obtained by subtracting the AF evaluation value from the peak AF evaluation value is larger than a preset threshold value (step S38; Yes), the control unit 200 stops the movement of the focus lens 1a (step S39). Then, the first evaluation operation is terminated.

FIG. 11 shows an operation flow of the second evaluation operation in the second embodiment.
The control unit 200 reads the peak upper limit lens position and the peak lower limit lens position detected from the first evaluation operation (step S41).

  The control unit 200 calculates the first distance from the read peak upper limit lens position and peak lower limit lens position (step S42).

  The control unit 200 determines whether or not the calculated first distance is within the depth of focus (step S43).

  When the control unit 200 determines that the first distance is within the depth of focus (step S43; Yes), the peak AF detected from the first evaluation operation from the read peak upper limit lens position and peak lower limit lens position. The peak lens position of the evaluation value is calculated (step S44), the focus lens 1a is moved to the calculated peak lens position (step S45), and the adjustment of the focus position is ended.

  When the control unit 200 determines that the first distance is not within the depth of focus (step S43; No), the moving direction of the focus lens 1a is set in a direction opposite to the first evaluation operation (for example, a negative direction). (Step S46).

The controller 200 determines whether or not the read timing signal S _V has fallen (step S47), and waits until the read timing signal S _V falls (step S47; No).

When the control unit 200 determines that the readout timing signal S _V has fallen (step S47; Yes), the lens driving instruction signal S _m0 is output to the lens driving unit 70 so that the focus lens 1a is moved N steps in the negative direction. (Step S48).

Thereafter, the control unit 200 again determines whether fall of the read timing signal S _V (step S49), and waits until the read timing signal falls (Step S49; No).

When the control unit 200 determines that the read timing signal _SV has fallen (step S49; Yes), the AF detection unit 40 performs AF detection to determine whether or not the AF detection processing of the AF detection unit 40 has been completed. It is determined whether or not a processing completion signal has been input (step S50), and the system waits for an AF detection processing completion signal to be input (step S50; No).

Control unit 200, AF detection processing completion signal is inputted when it is determined that (AF detection processing completed) (step S50; Yes), the AF evaluation value from the AF evaluation value signal S _AF inputted from the AF detection unit 40 Obtain (step S51).

  The control unit 200 determines whether or not the acquired AF evaluation value is greater than or equal to the target AF evaluation value (step S52). When it is determined that the acquired AF evaluation value is not equal to or higher than the target AF evaluation value (step S52; No), the process returns to step S47.

  When it is determined that the acquired AF evaluation value is equal to or greater than the target AF evaluation value (step S52; Yes), the control unit 200 ends the focus position adjustment operation.

  As described above, the peak AF evaluation value for the optical image is detected by acquiring the image signals of a plurality of frames while moving the focus lens 1a in the first evaluation operation, and the peak AF evaluation detected in the second evaluation operation is detected. The position of the focus lens 1a is adjusted based on the value.

FIG. 12 shows an example of a timing chart of the first evaluation operation of the second embodiment.
The frame period T _f is a period from the falling time of the readout timing signal S _V to the next falling time, and the lens driving signal S _m , the charge accumulation signal of each scanning line, the image signal S _i , and the AF evaluation. The value signal _SAF is schematically shown.

At time t21, the focus lens 1a on the basis of the lens driving signal S _m is in one direction (e.g., positive direction.) Begins moving at a constant speed. The read timing signal S _V falls, counting the exposure start time and the AF lower scanning line L _We exposure end time of AF upper scanning line L _Ws is started.

At time t22, exposure of the AF upper limit scanning line L _Ws is started, and the upper limit lens position is detected and stored.

At time t24, the exposure of the AF lower scanning line L _We are terminated, detecting and storing processing of the lower lens position is performed.

When the period of one frame period T _f from time t21 to time t23 is the first frame period, the AF evaluation value for the first frame period is V ₁ shown in FIG.

At time t25, the AF evaluation value V ₁ is acquired from the AF detector 40. Thus, the AF evaluation value of each frame is calculated while the focus lens 1a is moved in one direction at a constant speed, and the peak AF evaluation value is detected.

At time t31, the read timing signal S _V falls, counting the exposure start time and the AF lower scanning line L _We exposure end time of AF upper scanning line L _Ws is started.

At time t32, exposure of the AF upper limit scanning line L _Ws is started, and the upper limit lens position is detected and stored.

At time t35, the exposure of the AF lower scanning line L _We are terminated, detecting and storing processing of the lower lens position is performed.

If the period of one frame cycle T _f of the time t33 from the time t31 to the n-th frame period, AF evaluation values with respect to the n-th frame period becomes V _n shown in FIG. 12.
At time t36, the AF evaluation value V _n is acquired from the AF detector 40.

For example, when the AF evaluation value V _n is larger than the peak AF evaluation value, the AF evaluation value V _n is updated to the peak AF evaluation value, and the upper limit lens position and the lower limit lens position with respect to the AF evaluation value V _n are the peak upper limit lens position and the peak. Updated as the lower limit lens position.
A value obtained by subtracting the AF evaluation value V _n from the peak AF evaluation value subjected to the update process is “0”, which is equal to or less than a preset threshold value. Therefore, the peak AF evaluation value in the next frame (n + 1 frame) Detection operation is performed.

At time t37, the AF evaluation value V _{n + 1} for the (n + 1) th frame period is acquired.

At time t38, it is determined that a value obtained by subtracting the AF evaluation value V _{n + 1} from the peak AF evaluation value is larger than a preset threshold, and the movement of the focus lens 1a is stopped. The evaluation operation is terminated.

In the first evaluation operation, the AF evaluation value V _{n is} detected as the peak AF evaluation value, the position of the focus lens 1a with respect to time t32 as the peak upper limit lens position, and the position of the focus lens 1a with respect to time t35 as the peak lower limit lens position.
At this time, the first distance can be calculated as the moving distance of the focus lens 1a from time t32 to time t35. Further, the peak lens position can be approximated as a lens position with respect to an intermediate time t34 between time t32 and time t35.

  In the second evaluation operation, when the calculated first distance is within the focal depth, the focus lens 1a is moved to the lens position with respect to time t34 as the peak lens position.

FIG. 13 shows an example of a timing chart of the second evaluation operation of the second embodiment.
The timing chart shown in FIG. 13 is an example of a timing chart of operations performed when the calculated first distance is larger than the focal depth.
In addition, the lens position where the focus lens 1a is stopped in the first evaluation operation is set as _PA0 .

The frame period T _f is a period from the falling time of the readout timing signal S _V to the next falling time, and the lens driving signal S _m , the charge accumulation signal of each scanning line, the image signal S _i , and the AF evaluation. The value signal _SAF is schematically shown.

At time t41, the readout timing signal S _V falls, and the focus lens 1a starts to move N steps from the lens position P _{A0 in the} negative direction by the lens driving signal S _m .

At time t42, the movement of the focus lens 1a is terminated by a lens drive signal S _m (e.g., moved focus lens 1a from the lens position P _A0 to the lens position P _A1 moved N steps.).

At time t43, the read timing signal S _V falls. At this time, the focus lens 1a is not moved and is stopped at the lens position _PA1 .

After the read timing signal S _V drops falling (after time t43), at time t44, the AF evaluation value V _A1 of the lens position P _A1 is obtained, and the AF evaluation value V _A1 acquired the target AF evaluation value The comparison operation is performed.

For example, if the AF evaluation value V _A1 is not the target AF evaluation value or more, to wait for the read timing signal S _V falls.

At time t45, the read timing signal S _V falls, the focus lens 1a by the lens driving signal S _m is initiated N step movement from the lens position P _b in the negative direction.

At time t46, the movement of the focus lens 1a is terminated by a lens drive signal S _m (e.g., moved focus lens 1a from the lens position P _A1 to the lens position P _A2 has moved N steps.).

  From time t45 to time t46, the focus lens 1a is moved during the exposure period.

The period from time t41 to time t45 corresponds to two periods of the frame period _Tf , and the AF evaluation value V _A1 for the lens position P _A1 can be acquired twice. From time t45 to time t46, Since the focus lens 1a is moved during the exposure period, the AF evaluation value for the latter frame period _Tf has a low evaluation accuracy. Therefore, only the AF evaluation value calculated from the effective image signal at the lens position P _A1 based on the charge accumulation signal of the first half frame period surrounded by the one-dot chain line is an effective value for AF evaluation, and the charge accumulation signal of the second half frame period The AF evaluation value calculated from the invalid image signal at the lens position P _A1 based on is not acquired. Accordingly, an AF evaluation value is acquired every two frame periods.

At time t47, the read timing signal S _V falls. At this time, the focus lens 1a is not moved and is stopped at the lens position _PA2 .

After the read timing signal S _V drops falling (after time t47), at time t48, is obtained AF evaluation value V _A2 of the lens position P _A2 has the acquired AF evaluation value V _A2 and the target AF evaluation value The comparison operation is performed.

For example, when the AF evaluation value V _A2 is equal to or greater than the target AF evaluation value, the focus position adjustment operation is terminated. That is, the focus lens 1a is adjusted to the lens position P _A2 with respect to the AF evaluation value V _A2 .

As described above, in the first evaluation operation, the standard of the focus position can be set by detecting the peak AF evaluation value.
In the second evaluation operation, based on the peak AF evaluation value detected from the first evaluation operation, when the first distance is within the focal depth, the peak with respect to the peak AF evaluation value detected instantaneously When the focus lens 1a can be adjusted to the lens position and the first distance is larger than the depth of focus, the focus lens 1a is moved in a two-frame cycle, and the AF evaluation value detected every two frame cycles is the target. Since the focus lens 1a is adjusted to a lens position that is equal to or higher than the AF evaluation value, the focus position can be adjusted based on an image signal in a state where the focus lens 1a does not move during the exposure period.

  Therefore, by performing the first evaluation operation and the second evaluation operation, the position of the focus lens 1a is adjusted based on the focus position guideline, so the processing time required to complete the adjustment of the focus position is shortened. The focus position can be adjusted at high speed while maintaining a certain accuracy.

  Further, the present invention is not limited to the contents of the above embodiment, and can be appropriately changed without departing from the gist of the present invention.

1 is a block diagram of a schematic configuration of an automatic focus adjustment apparatus A according to Embodiment 1. FIG. 1 is a schematic configuration diagram of an image sensor 10. 1 is a partially enlarged view of an image sensor 10. It is an example of AF evaluation area | region _WAF . FIG. 6 is a relationship diagram between a position of a focus lens 1a and an AF evaluation value. FIG. 10 is a flow chart for adjusting the exposure time T _{exp in} the first embodiment. FIG. 6 is a flowchart of a focus adjustment operation according to the first embodiment. 3 is an example of a timing chart of the first embodiment. FIG. 6 is a block diagram of a schematic configuration of an automatic focus adjustment apparatus B in the second embodiment. It is an operation | movement flowchart of the 1st evaluation operation | movement in this Embodiment 2. FIG. It is an operation | movement flowchart of the 2nd evaluation operation | movement in this Embodiment 2. FIG. It is an example of the timing chart of the 1st evaluation operation | movement of this Embodiment 2. FIG. It is an example of the timing chart of the 2nd evaluation operation | movement of this Embodiment 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pick-up optical system 1a Focus lens 2 Aperture 10 Image pick-up element 11 Photoelectric conversion part 12 Reading vertical shift register 13 Reset vertical shift register 14 Horizontal shift register 15 Output amplifier 20 Timing signal generation circuit part 30 A / D conversion and amplification part 40 AF detector 41 Gate circuit 42 BPF
43 Accumulating unit 50 Aperture driving unit 60 Lens position detecting unit 70 Lens driving unit 80 Unit pixel circuit 81 Vertical scanning line 82 Reset scanning line 83 Vertical signal line 84 Output signal line 100, 200 Control unit A, B Automatic focus adjustment device L _AF AF evaluation area W _AF vertical width (number of vertical scanning lines)
L _W1 first scan line L _We AF lower scanning line L _Wm first m scanning lines L _Ws total scanning lines of the AF upper scanning line m frame area W _{F M A} amplifier _{M L} horizontal switch transistor _{M R} reset transistor _{M S} selection transistor PD Photodiode S _AF AF evaluation value signal S _G gain adjustment instruction signal S _i image signal S _m lens drive signal S _m0 lens drive instruction signal S _P lens position signal S _V readout timing signal S _W AF evaluation area instruction signal T _exp minimum exposure Time T _exp0 Proper exposure time T _m Lens drive time T _f Frame period W _AF AF evaluation area W _F frame area

Claims (7)

Optical means provided so as to be movable in the direction of the optical axis, and for forming an optical image of a subject;
A line exposure type imaging means for converting an optical image formed through the optical means into an image signal;
Drive means for moving the optical means in the direction of the optical axis;
Evaluation value calculation means for calculating an automatic focus adjustment evaluation value for evaluating the position in the optical axis direction of the optical means based on an image signal in an evaluation area set in advance in the imaging area obtained by the imaging means;
Based on the time corresponding to the vertical width of the evaluation area and the driving time of the optical means required for one frame of the imaging area, the minimum exposure in which the exposure period in the evaluation area and the driving period of the optical means do not overlap Exposure time calculating means for calculating time;
Control means for controlling the imaging means and drive means based on the calculated minimum exposure time;
An automatic focusing apparatus characterized by comprising: The automatic focusing apparatus according to claim 1, wherein
An amplifying unit that adjusts the amplification of the image signal output from the imaging unit when the calculated minimum exposure time is underexposure;
Automatic focusing device characterized by. The automatic focusing apparatus according to claim 1 or 2,
A light amount adjusting means for adjusting the amount of light flux when the calculated minimum exposure time is insufficient for exposure;
Automatic focusing device characterized by. Optical means provided so as to be movable in the direction of the optical axis, and for forming an optical image of a subject;
Line exposure type imaging means for converting an optical image formed through the optical means into an image signal;
Driving means for moving the optical means in the optical axis direction;
Evaluation value calculation means for calculating an automatic focus adjustment evaluation value for evaluating the position in the optical axis direction of the optical means based on an image signal in an evaluation area set in advance in the imaging area obtained by the imaging means;
A first evaluation operation for detecting the maximum value of the automatic focus adjustment evaluation value calculated from the calculation means while moving the optical means at a constant speed in one direction in the optical axis direction, and detection from the first evaluation operation. Control means for performing a second evaluation operation for adjusting the in-focus position based on the maximum value of the automatic focus adjustment evaluation value,
Having
Automatic focusing device characterized by. The automatic focusing apparatus according to claim 4, wherein
When the control means performs the first evaluation operation,
The position of the optical means at the exposure start time of the upper limit scanning line of the automatic focus adjustment evaluation area with respect to the detected maximum value of the automatic focus adjustment evaluation value, and the position of the optical means at the exposure end time of the lower limit scan line. Detecting and memorizing,
Automatic focusing device characterized by. The automatic focusing apparatus according to claim 5, wherein
When the control means performs the second evaluation operation,
The distance from the position of the optical means at the exposure start time of the upper limit scanning line of the automatic focus adjustment evaluation area to the position of the optical means at the exposure end time of the lower limit scanning line with respect to the detected maximum value of the automatic focus adjustment evaluation value When the first distance is calculated and the first distance is within the depth of focus, the position of the optical means with respect to the maximum value of the automatic focus adjustment evaluation value calculated in the first evaluation operation is set as the in-focus position. Adjusting,
Automatic focusing device characterized by. The automatic focusing apparatus according to claim 6, wherein
When the control means performs the second evaluation operation,
If the first distance is not within the depth of focus, the optical means is moved in the opposite direction to the first evaluation operation at intervals of two frame periods, and the automatic focus adjustment evaluation value calculated from the calculation means is Adjusting a position that is equal to or greater than a target value calculated based on the maximum value of the automatic focus adjustment evaluation value calculated from the evaluation operation of 1 as a focus position;
Automatic focusing device characterized by.