JPH04328509A - Focus adjustment device - Google Patents

Abstract

PURPOSE:To shorten the time of navigation-point detecting operation in search operation and to prevent electric power from being consumed unnecessarily. CONSTITUTION:This focus adjustment device is provided with a decision means PRS which decides whether or not the operation of a search operation indicating means is stopped according to the signal VB from a maximum signal detecting means and the signal VB from a minimum signal detecting circuit and this decision means decides whether the search operation is ended or continued according to whether or not the difference between the signal from the maximum signal detecting means and the signal from the minimum detecting means reaches a specific level.

Description

[Detailed description of the invention]

0001

FIELD OF APPLICATION OF THE INVENTION The present invention is based on the maximum signal detection means for detecting the largest output signal from the photoelectric conversion means, the minimum signal detection means for detecting the smallest output signal, and the output from the focus detection means. A lens driving means for driving the imaging lens and an output from the photoelectric conversion means determine whether or not focus detection is possible, and when focus cannot be detected, the imaging lens is driven regardless of the detection result of the focus detection means. The present invention relates to an improvement in a focus adjustment device including a search operation instruction means for causing the lens driving means to perform a search operation.

0002

2. Description of the Related Art Conventionally, one type of focus detection device for a camera divides the exit pupil of a photographic lens and observes the relative positional displacement of two images formed by light beams passing through each pupil area. There are known methods for determining the state of focus. For example, an aerial image formed on a predetermined focal plane (plane equivalent to a film plane) by two parallel imaging optical systems is guided to two sensor surfaces, and the displacement of the relative position of the two images is detected. A secondary imaging method is disclosed in Japanese Patent Laid-Open Nos. 55-118019 and 1987-155331.

FIG. 7 shows an outline of the secondary imaging type focus detection device.

Photographic lens 1 and optical axis 2 whose focus is to be detected
Similarly, a field lens 3 is arranged. Two secondary imaging lenses 4a and 4b are arranged behind it at symmetrical positions with respect to the optical axis 2. Furthermore, sensor rows 5a and 5b are arranged behind it. Apertures 6a and 6b are provided near the secondary imaging lenses 4a and 4b. The field lens 3 connects the exit pupil of the photographing lens 1 with two secondary imaging lenses 4.
The images are almost formed on the pupil planes a and 4b. As a result, the beams of light incident on the secondary imaging lenses 4a, 4b are arranged on the exit pupil plane of the photographing lens 1 on the respective secondary imaging lenses 4a, 4b.
are emitted from areas of equal area that do not overlap with each other. When the aerial image formed near the field lens 3 is re-imaged onto the surfaces of the sensor arrays 5a and 5b by the secondary imaging lenses 4a and 4b, based on the displacement of the aerial image position in the optical axis direction, The two images on the sensor arrays 5a and 5b change their positions.

FIG. 8 shows this situation, and FIG. 8(A)
As shown in FIG.
When the rear focus is shown in FIG. 8(B), the two images move away from the optical axis 2, and as shown in FIG. 8(C), the two images move away from the optical axis 2. The image moves in a direction approaching the optical axis 2. The focal state of the photographic lens 1 can be detected by photoelectrically converting this image intensity distribution and detecting the displacement (shift) of the relative positions of the two images through electrical signal processing.

A method for processing the photoelectric conversion signals outputted from the sensor arrays 5a and 5b is disclosed in Japanese Patent Laid-Open No. 58-14
No. 2306, US Pat. No. 4,333,007, and the like are disclosed. Specifically, the sensor row 5a or 5b
The number of photoelectric conversion elements (pixel number) constituting is N, and the image signals from the i-th (i = 0, ..., N-1) sensor rows 5a and 5b are A(i) and B(i) Then, the following equation is calculated for k1≦k≦k2. Sho M is (M
=N-|k|-1). A(
i)□B(j) is an operator for A(i), B(j), for example, the following calculation expressions can be considered, and equation (2) is A(i), B(j)
Equation (3) expresses the absolute value of the difference, Equation (4) expresses the greater of A(i) and B(j), (5) (5)
The expressions each represent the extraction of a small thing. According to the above definition, V1 (k) and V2 (k) can be regarded as correlation quantities in a broad sense. Furthermore, V1 (k) is (
1) According to the formula, in reality, the correlation amount according to the above definition at the displacement of (k-1), similarly, V2 (k) is (k+1)
) respectively mean the amount of correlation in the displacement. Therefore, the evaluation amount V(k), which is the difference between V1 (k) and V2 (k), is the image signal A(i) and B at the relative displacement amount k.
It represents the change in the amount of correlation in (i). Since the amount of change in the amount of correlation becomes "0" at its peak, V(k)・V(k+1)<0

(6) Considering that the peak of the correlation amount exists in the interval [k, k+1], the values of V(k) and V(k+1) are interpolated, and the image signals A(i) and B(i ) can be found.

FIG. 9 shows two image signals A(i) and B(i) when the number of pixels is 16 (N=16). In this case, there is a deviation amount of P.

In FIG. 10, the relative displacement amount k is expressed as “-N/2≦k
≦N/2'' represents the evaluation amount V(k) according to the above equation (2) when changed within the calculation range. As mentioned above, “V(k
)・V(k+1) <0'' V(k), V(k+1)
The deviation amount P can be obtained by linearly interpolating the value of .

Furthermore, in FIG. 11, the relative displacement amount k is
Each evaluation amount V(k) when changed in the calculation range of 3≦k≦3”
The correspondence between image signals A(i) and B(i) when calculating is diagrammatically shown, and the shaded area is the photoelectric conversion element to be subjected to the correlation calculation.

[0010] Normally, when calculating the amount of deviation P, the contrast of the two images is also calculated, and if the contrast is lower than a predetermined value, it is determined that the reliability of the amount of deviation P obtained is poor. Therefore, the focus cannot be detected. The focus detection failure operation is performed by moving the photographing lens a predetermined amount or continuously in the hope that the contrast will increase.
There is a "ch action".

[0011]

[Problems to be Solved by the Invention] However, if the image sensor consisting of the sensor arrays 5a and 5b accumulates and reads image signals and calculates the contrast of the two read images in parallel with lens driving, the lens driving When the speed is high, the image sensor passes through the in-focus position during a series of drives and image signal processing, leading to erroneous judgments such as not being able to detect focus even though focus can be detected, and errors in lens drive direction. A phenomenon in which it takes a long time to focus due to the reversal of the images frequently occurs. This results in a significant decrease in reliability and discomfort for the user, as well as an increase in battery consumption due to unnecessary lens driving, image sensor driving, and information processing.

[0012] From the above, the current practice is to set the lens drive speed within a range that does not cause these problems during a search operation, and to perform lens drive with good responsiveness and high precision focus adjustment. The device has not yet been realized.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide a focus adjustment device that can shorten the time required for focus detection operation during a search operation and eliminate unnecessary power consumption. It is.

[0014]

[Means for Solving the Problems] The present invention provides determination means for determining whether or not to stop the operation of search operation instruction means based on a signal from a maximum signal detection means and a signal from a minimum signal detection means. has been established.

[0015]

[Operation] The determination means terminates or continues the search operation based on the signal from the maximum signal detection means and the signal from the minimum signal detection means, that is, based on whether the difference between these signals is at a predetermined level. The decision is being made as to whether or not to do so.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a camera including a focus adjustment device which is an embodiment of the present invention.

In FIG. 1, PRS is a camera control circuit that includes, for example, a CPU (central processing unit), RAM,
It is a one-chip microcomputer in which a ROM, an EEPROM (electrically erasable programmable ROM), an input/output port, etc. are arranged;
A series of camera control software and parameters including AF control are stored in M. DBUS is data
tabus, SHT is the control signal CS from the control circuit PRS.
The APR is a shutter control circuit that receives data input via the data bus DBUS while the HT is input, and controls the running of the shutter front curtain and rear curtain (not shown) based on the data. While the signal CAPR is input, data input via the data bus DBUS is accepted, and the data is
The diaphragm control circuit, DSP, which controls the diaphragm mechanism (not shown) based on the data, receives data input via the data bus DBUS while the control signal CDSP is input.
A display circuit that displays various shooting information based on data, SWS
is a group of switches (not shown) such as a release switch, a continuous shooting mode switch, and switches for setting various information.

SPC is a photometric circuit, and its output analog photometric signal SSPC is sent to the control circuit PRS, where it is A/D converted and sent to the shutter control circuit SHT and aperture control circuit APR. It is used as photometric data for control. LCOM is control signal C
This is a lens communication circuit that accepts data input via the data bus DBUS while LCOM is input, and performs serial communication with the lens unit described later based on the data, in synchronization with the clock signal LCK. Data for lens drive
The data DCL is transmitted to an in-lens control circuit to be described later, and at the same time, lens information DLC such as the maximum defocus amount of the photographing lens (to be described later) is serially input from the in-lens control circuit. BSY is a signal to notify the camera side that a focusing lens, which will be described later, is moving, and when this signal is generated, the serial communication is not performed.

LNSU is a lens unit, and LPRS is an in-lens control circuit that drives the motor MTR based on serially input data DCL to move the photographing lens LNF. It has a ROM that stores information such as the amount of waste MD, focal length, and aperture F value. ENC is, for example, the photographing lens LN.
an encoder that detects a pulse signal generated as the lens barrel holding the lens F moves, and outputs an encoder pulse signal EPL to the in-lens control circuit LPRS as the current position information of the photographing lens LNF; The circuit SDR is a sensor drive circuit that controls an image sensor SNS as described later, which has two sensor arrays SAA and SAB according to each signal inputted from the control circuit PRS.

The above-mentioned image sensor SNS in this embodiment is disclosed in Japanese Patent Application Laid-open No. 12579/1982 and Japanese Patent Laid-open No. 60-1
It is composed of an accumulation type sensor array consisting of a phototransistor array, as disclosed in Japanese Patent No. 2765. This sensor array is different from known CCD sensors and MOS sensors,
A charge proportional to the incident light is accumulated in the base portion of the transistor, and during readout, a signal corresponding to the amount of accumulated charge is output for each sensor column. Since the operation of the photoelectric conversion element alone is disclosed in the above-mentioned publications, etc., the details thereof will be omitted.

FIG. 4 is a circuit diagram showing the overall configuration of the image sensor SNS, and FIG. 5 is a circuit diagram corresponding to one pixel thereof. In addition to the light receiving section and the signal readout system, a maximum signal output circuit and a minimum signal output circuit are added to these figures.

In these figures, the bipolar transistor TR1 is a photoelectric conversion element, and when a plurality of bipolar transistors TR1 are collected, it becomes an image signal detection sensor array block SNSPX shown by a dashed line in FIG.

Block DRCKT is a control and readout circuit for bipolar transistor TR1, which is a photoelectric conversion element, and includes a plurality of MOS transistors 5, 8, 10, 1.
1, 12, 13, 14, 151 (denoted as MOS5 in the drawing, the same applies to the others), capacitors CTn, CTs, and a differential output amplifier SNSAMP.

The block BDET is a minimum signal detection circuit that detects the smallest signal of the output obtained by photoelectrically converting the luminous flux incident on the sensor array, and the block BDET is a minimum signal detection circuit that detects the smallest signal of the output obtained by photoelectrically converting the luminous flux incident on the sensor array.
2. MOS transistor 6 and several MOs shown in the diagram
It is composed of S transistors.

The block PDET is a maximum signal detection circuit that detects the largest signal of the output obtained by photoelectrically converting the luminous flux incident on the sensor array, and the block PDET is a maximum signal detection circuit that detects the largest signal of the output obtained by photoelectrically converting the luminous flux incident on the sensor array.
3. MOS transistor 7 and several MOs shown in the diagram
It is composed of S transistors.

The gates of the P-channel MOS transistors 5 connected to the base of the bipolar transistor TR1, which is a photoelectric conversion element, are connected in common, and a sensor reset clock φRES is inputted thereto. The sources of the MOS transistors 5 are also connected in common and supplied with a constant potential VBG. The gates of the MOS transistors 8 connected to the emitter of the transistor TR1 are connected in common, and a reset clock φVRS is input thereto. Further, the emitter of the transistor TR1 is connected to a capacitor CTn via a MOS transistor 10 and a capacitor CTs via a MOS transistor 11, and the charges of each capacitor CTn and CTs are output as differential outputs via MOS transistors 12 and 13, respectively. Amplifier SNSAMP
is input. Further, MOS transistors 12 and 13 are sequentially turned on by shift register SNSSR. The shift register SNSSR receives the input read clock φ
The configuration is such that the signal end that becomes "H" is sequentially shifted by SH.

The gates of the MOS transistors 10 are commonly connected and receive an accumulation start clock φTn. The gates of the MOS transistors 11 are connected in common, and an accumulation completion clock φTs is input thereto. In addition, the inputs VoutN and Vout of the output amplifier SNSAMP
S is connected to G via MOS transistors 14 and 15, respectively.
Connected to ND. MOS transistors 14, 15
A read clock φHRS is input to the gate of the gate.

The emitter of bipolar transistor TR1, which is a photoelectric conversion element, is also connected to the gate of N-channel MOS transistor 6 and the gate of P-channel MOS transistor 6, and the sensor output is determined by the accumulation time. The signal is constantly supplied to the maximum signal detection circuit PDET and the minimum signal detection circuit BDET.

The maximum signal detection circuit PDET and the minimum signal detection circuit BDET have mutually complementary differential amplifier configurations, and the output stages include an NPN transistor and a PN transistor, respectively.
It takes the form of a P transistor emitter follower,
They are output to terminals Vmax and Vmin, respectively.

As mentioned earlier, FIG. 4 shows a sensor array formed by arranging a plurality of the circuits shown in FIG.
ax and Vmin are each commonly connected.

The emitter output of the bipolar transistor TR1 is at various levels depending on the illuminance of the light beam irradiated to each photoelectric conversion element, and the minimum signal detection circuit BDET connected to the emitter that is not at the minimum level is a comparator. In order to operate, all of the bipolar transistors TR2 are cut off, and only the minimum signal detection circuit BDET connected to the emitter at the minimum level operates as a voltage follower. The output Vmin' of the bipolar transistor TR2 outputs a value equal to the potential input to the gate of the MOS transistor 6, and is outputted via the constant current load ILmin and the buffer amplifier VBAMP.

Furthermore, since the maximum signal detection circuit PDET connected to the emitter which is not at the maximum level performs a comparator operation, all of the bipolar transistors TR3 are cut off and connected to the emitter which is not at the maximum level. Only the maximum signal detection circuit PDET, which is currently in operation, operates as a voltage follower. Output Vm of bipolar transistor TR3
ax outputs a value equal to the potential input to the gate of MOS transistor 7, and is outputted via constant current load ILmax and buffer amplifier VBAMP.

The output VP of the buffer amplifier VPAMP and the output VB of the buffer amplifier VBAMP are connected to the control circuit P in FIG.
The signals are input to the storage control circuit and AGC circuit built into the RS and the sensor drive circuit SDR, respectively.

Next, the image sensor (sensor array) S
The operation of the NS will be explained based on the timing chart of FIG.

In the figure, SCLK, SO, and BTIME are control signals input from the control circuit PRS to the sensor drive circuit SDR, and φRES, φVRS, φTn, φTs,
φSH and φHRS are clock signals input from the sensor drive circuit SDR to the image sensor SNS.

By setting the clock signal φRES to "L", all the P-channel MOS transistors 5 are turned on, and the potential VBR is applied to the base of each transistor TR1. As a result, if the residual potential at the base of the transistor TR1 is greater than VBG, the excess charges are recombined, and finally the charges whose base potential is VBG are held at the base.

Furthermore, since the clock signals φTn and φTs are also at "H" between time t1 and time t2, the charges in the capacitors CTn and CTs are also cleared via the MOS transistor 8.

Next, after the clock signal φRES goes to "H" at time t4, φVRS goes to "H" at time t5, so the charges held in the base gradually recombine and disappear. . Since the base of each transistor TR1 held a charge whose base potential was VBG at time t4, the amount of charge remaining at the base at time t6 was held before time t3. Regardless of the amount of charge, it is equal in all transistors TR1.

[0039] When φVRS becomes “L” at time t6, M
OS transistors 8 and 11 are turned off, and from this point on, the charges generated by photoexcitation are transferred to the base of transistor TR1.
It is accumulated in the The period from time t1 to time t6 is the sensor reset operation.

After a predetermined accumulation time has elapsed, the MOS transistor 11 is turned on for a time corresponding to the pulse width by the "H" clock signal φTs from time t9 to time t10, and the amount of charge accumulated in the base of the transistor TR1 is reduced. A signal corresponding to the voltage is transferred to the capacitor CTs by transistor operation. Therefore, the charges accumulated in the base at this time do not decrease, and the photo-excited charges continue to accumulate in the base of the transistor TR1.

After this, first, the clock signal φHRS becomes "H" for a predetermined time from time t1 to time T11, so that
The MOS transistor 14 is turned on during that time, and the charge remaining in the stray capacitance of the read lines RDLN and RDLS is transferred to G.
Since it is flowing to ND, " from time t12 to time t13"
Shift register SN is activated by clock signal φSH of “H”.
Scanning of each NOS transistor 12 and 13 by SSR is started. When the MOS transistors 12 and 13 are turned on, the signals held in the capacitors CTn and CTs pass through the read lines RDLN and RDLS, and the differential output SNSS is outputted to the sensor drive circuit SDR via the differential output amplifier SNSAMP.

By repeating the above operations, time t
The signals photoelectrically converted during the accumulation time from time 6 to time t9 can be sequentially read out.

In this way, all transistors TR
When the reading of the signal 1 is completed, the reset operation from time t1 to time t6 is performed again, and the next accumulation operation is started.

The above is an explanation of the operation of the image signal detection system.

Next, the operation of the control circuit PRS of FIG. 1 will be explained with reference to the flowchart of FIG. Note that the operations of the shutter control circuit SHT, aperture control circuit APR, display circuit DSP, and photometry circuit SPC are not directly related to the present invention, and will therefore be omitted here. [Step 1] Drive the image sensor SNS via the sensor drive circuit SDR, and drive the sensor drive circuit SD in synchronization with the clock SCLK output from the control circuit PRS.
A/D convert the analog image signal SDRS, which is obtained by amplifying the sensor image signal SNSS by a predetermined amplification degree using R, and store it at a predetermined address in the RAM as two image signals A(i) and B(i). do.

The operations of the control circuit PRS, sensor drive circuit SDR, and image sensor SNS at this time have already been described, so they will be omitted here. [Step 2] Check the status of the continuous shooting mode switch in the switch group SWS, and if it is in continuous shooting mode, proceed to step 1.
3, otherwise go to step 3. [Step 3] Communicate with the lens unit LNSU via the lens communication circuit LCOM and send lens information DLC.
Then, obtain the maximum defocus amount MD of the currently attached photographic lens LNF, and according to this value, set the relative displacement amount k as "-".
In the calculation range of MD≦k≦MD, that is, “k1 = −
MD” and “k2 = MD”. [Step 4] For example, a correlation calculation such as the above-mentioned equations (1) to (5) is performed to obtain focus detection information, that is, the amount of shift P between the two images at this time. [Step 5] Even if the shift amount P can be detected, if the contrast of the signal is low and the reliability of the result is poor, the focus cannot be detected. In such a case, go to step 10; if the focus can be detected, proceed to Move to step 6. [Step 6] Compare the absolute value of the amount of deviation P with a predetermined value, and if the amount of deviation P is smaller than the predetermined value, that is, the amount of change that can be considered to be in focus, proceed to step 9; otherwise, proceed to step 9. moves to step 7. [Step 7] It is determined whether the subject is in front or rear focus based on the sign (positive or negative) of the shift amount P, and the data is sent to the display circuit DSP to display the focus state at that time. [Step 8] Calculate the amount of movement of the photographing lens LNF based on the shift amount P obtained in Step 4, and send the data to the in-lens control circuit L via the lens communication circuit LCOM.
Output to PRS. To briefly explain the operation on the lens unit LNSU side at this time, the in-lens control circuit LPR
S drives the motor MTR to move the photographic lens LNF to a position corresponding to the data, that is, until the number of encoder pulse signals EPL input from the encoder circuit ENC matches the data. move it. [Step 9] Data indicating that the focus is in focus is sent to the display circuit DSP, and the data is displayed. [Step 10] It is determined that the focus cannot be detected in step 5, and the maximum defocus amount MD obtained in step 3 is compared with the constant defocus amount MS, and "MD
>MS”, the process proceeds to step 12; if “MD≦MS”, the process proceeds to step 11. [Step 11] If "MD≦MS", it means that the maximum defocus value of the currently attached photographic lens LNF is relatively small. - Even if the focus is detected again after performing the
Since D is small, no increase in contrast can be expected, and as a result, the probability that focus will be detected next time is low. Therefore, in such a case, the search operation is not performed, and data indicating that the focus cannot be detected is output to the display circuit DSP, and the data is displayed. After that, the process moves to step 1 again. [Step 12] If “MD>MS”, “MD≦
Contrary to the case of "MS", there is a high probability that the focus can be detected by the search operation, so the search operation is performed. [Step 13] In continuous shooting mode, focus detection must be performed in a shorter time than in single shooting mode, and it is expected that the defocus of the subject will not change much during continuous shooting. Since this is possible, a relatively small predetermined relative displacement kc is set, that is, relative displacement k1 = -kc,k
2=kc to speed up the calculation. [Step 14] Correlation calculation is performed to obtain focus detection information within the calculation range set in step 13. [Step 15] As in step 5, it is determined whether focus detection is possible or not. If focus detection is not possible, performing a search operation during continuous shooting is not suitable for quick shooting. Since it is not preferable because of the surface, etc., proceed to step 11 to display an impossible display, and if the focus can be detected, proceed to step 6.
The camera then moves to determine focus. Thereafter, the process moves to step 9 or step 7→step 8, as described above.

Next, the search operation in step 12 will be outlined with reference to the flowchart of FIG. [Step 21] A signal is issued from the control circuit PRS via the sensor drive circuit SDR to reset the image sensor SNS, and the maximum signal output VP and minimum signal output VB are set to predetermined reference values. [Step 22] Data for driving the lens at a predetermined speed in a predetermined direction is communicated from the control circuit PRS to the in-lens control circuit LPRS, and lens driving is started. [Step 23] Input image sensor SNS
The maximum signal output VP and minimum signal output VB are A/D converted and taken into the control circuit PRS as outputs DP and DB, respectively. [Step 24] Difference value DPB between the outputs DP and DB
is calculated, and the difference value DPB is calculated as the characteristic difference in the dark obtained in a predetermined accumulation time in the dark of each photoelectric conversion unit constituting the sensor arrays SAA and SAB, that is, the difference between the maximum signal and the minimum signal. When the determination threshold value Dref having a predetermined value larger than the value obtained as the difference value DPB converted into a digital value is satisfied, it is determined that focus detection is possible and the process proceeds to the image signal detection operation shown in FIG. 2. If so, return to step 21.

According to this embodiment, determination of whether or not focus detection is possible during a search operation is made based on A of the maximum signal output VP from the maximum signal detection circuit and the minimum signal output VB from the minimum output detection circuit.
Since this is done using the difference value DPB of /D conversion values, that is,
During the search operation, contrast judgment is performed using the A/D conversion calculation value DPB while moving the photographic lens by a predetermined amount continuously or continuously, so that the image sensor's accumulation and signal readout and the contrast from the readout signal are Judgment is no longer necessary, focus detection time during search is shortened, and power is not wasted.

[0049]

[Effects of the Invention] As explained above, according to the present invention,
A determination means is provided for determining whether or not to stop the operation of the search operation instruction means based on the signal from the maximum signal detection means and the signal from the minimum signal detection means. It is determined whether the search operation should be terminated or continued based on whether the difference between the signals from the detection means is at a predetermined level. Therefore, the time required for the focus detection operation during the search operation can be shortened, and a focus adjustment device with good responsiveness can be provided. Moreover, this makes it possible to eliminate unnecessary consumption of power.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a camera including one embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the control circuit of FIG. 1;

[Fig. 3] Flowchart showing the operation in step 12 of Fig. 2.
It is a chart.

FIG. 4 is a circuit diagram showing the overall configuration of the image sensor of FIG. 1;

FIG. 5 is a circuit diagram corresponding to one pixel in FIG. 4;

FIG. 6 is a timing chart for explaining the operation of the image sensor of FIG. 4;

FIG. 7 is a layout diagram showing an optical system of a general secondary imaging type focus detection device.

FIG. 8 is a diagram showing the relationship between the focus detection state and image shift in the method of FIG. 7;

9 is a diagram showing an example of image signals output from two sensor arrays in the method of FIG. 7. FIG.

FIG. 10 is a diagram showing changes in evaluation amounts in the method of FIG. 7;

FIG. 11 is a diagram showing a correspondence relationship between two images during focus detection calculation in the method of FIG. 7;

[Explanation of sign]

PRS control circuit SDR sensor drive circuit SNS Image sensor PDET Maximum signal detection circuit BDET minimum signal detection circuit LNSU lens unit

Claims (1)

[Claims] 1. A photoelectric conversion means for receiving a luminous flux from a focus detection target, a focus detection means for detecting a focus state based on an output from the photoelectric conversion means, and a focus detecting means for detecting the largest output signal from the photoelectric conversion means. a maximum signal detection means for detecting, a minimum signal detection means for detecting the smallest output signal from the photoelectric conversion means, a lens driving means for driving an imaging lens based on the output from the focus detection means, and a lens driving means for driving the imaging lens based on the output from the focus detection means; It is determined from the output from the conversion means whether or not the focus can be detected, and when the focus cannot be detected, the lens driving means is provided with a search operation for driving the imaging lens regardless of the detection result of the focus detection means. In the focus adjustment device, the search operation is instructed based on a signal from the maximum signal detection means and a signal from the minimum signal detection means during the search operation. 1. A focus adjustment device comprising a determining means for determining whether or not to stop the operation of the focusing device.