JPH01288813A - Multipoint distance measuring instrument - Google Patents

Abstract

PURPOSE:To prevent focusing to a close distance object which is not intended by a photographer by executing the focusing at a value of the second closest distance measuring point, when a detection value of the closest distance measuring point in plural distance measuring points is smaller than a prescribed threshold. CONSTITUTION:In a control circuit PRS, a prescribed threshold calculated from a focal distance, etc., of a photographic lens is set separately to many distance measuring areas. In this state, when an accumulation start signal STR is sent to a sensor driving circuit SDR from the control circuit PRS, photoelectric conversion signals of sensor trains SAA, SAB1-SAA3, SAB3 of a line sensor SNS' of each distance measuring area are read in. Subsequently, when a detection value of the closest distance in the distance measurement is smaller than said threshold, the second closest point is selected and the focusing operation is executed, therefore, intended photographing can be executed without selecting a close distance object which is not intended by a photographer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a multi-point distance measuring device that measures a plurality of different distance measuring points within a photographic screen and performs a focus adjustment operation based on the distance measuring results. It is related to.

[Conventional technology]

Conventionally, one type of camera focus detection device divides the exit pupil of a photographic lens and determines the in-focus state by observing the relative positional displacement of two images formed by the light flux that passes through each pupil area. something is known. 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. The secondary imaging method is
JP-A-55-118019, JP-A-55-155
It is disclosed in Publication No. 331 and the like.

FIG. 4 schematically shows a focus detection device for the secondary imaging method. A field lens 43 is arranged with the same optical axis 42 as the photographing lens 41 whose focus is to be detected. Behind it, two secondary imaging lenses 44a and 44b are arranged at symmetrical positions with respect to the optical axis 42.

Furthermore, photoelectric conversion element rows 45a and 45b are arranged behind it. The field lens 43 forms an image of the exit pupil of the photographic lens 41 approximately on the pupil plane of the two secondary imaging lenses 44a and 44b. When the aerial image formed in the vicinity of the field lens 43 is re-imaged onto the planes of the photoelectric conversion element arrays 45a and 45b by the secondary imaging lenses 44a and 44b, based on the displacement of the aerial image position in the optical axis direction, , photoelectric conversion element array 4
The two images on 5a and 45b change their positions. FIG. 5 shows this situation. As shown in FIG. 5(A), when focusing, the two images are located at the center of the photoelectric conversion element arrays 45a and 45b, and as shown in FIG. 5(B). As shown, during rear focus, the second image moves away from the optical axis 2, and the fifth image moves away from the optical axis 2.
As shown in Figure (C), when the front is in focus, the two images move in a direction approaching the optical axis 2. The focal state of the photographic lens 41 can be detected by photoelectrically converting the light intensity distribution of the two images and detecting the displacement (shift) of the relative positions of the two images through electrical signal processing.

A method for processing photoelectric conversion signals output from the front light distribution electric conversion element rows 45a and 45b is disclosed in Japanese Patent Application Laid-Open No. 58-14230.
6, US Pat. No. 4,333,007, and the like.

Further, Japanese Patent Application No. 62-279835 discloses a focus detection device which is designed to be able to perform focus detection at locations other than the center of the distance measuring screen by using a plurality of the above-mentioned focus detection devices.

FIG. 7 is a perspective view showing the optical system of the latter focus detection device. 71 is a photographing lens, and 72 is a visual field mask. The light flux that has passed through the exit pupil 71a of the photographic lens 71 has its field of view restricted by a field mask 72, and passes through separate locations 73a to 73e of the divided field lens 73, respectively.

These light fluxes are imaged onto a line sensor 75 by separate secondary optical systems 74, respectively. Image data photoelectrically converted by the line sensor 75 is calculated using a known method to detect a focus.

FIG. 8 shows a focus detection device which is designed to be able to perform focus detection at a plurality of points using another optical system.

80 is a photographing lens, and 81 is a visual field mask. The light flux that has passed through the exit pupil 80a of the photographic lens 80 passes through the field mask 8.
Field lenses 8 each having a field of view limited by 1 and identical to each other.
2, the reimaging lens 83. 84
Accordingly, separate sensor rows 5AAI and 5ABI N
The image is formed on 5AA3 and 5AB3.

The sensor rows 5AAI, 5ABI to 5AA3, 5AB3
The image formed is photoelectrically converted, and focus detection of a plurality of distance measuring points corresponding to each sensor pair is performed by calculation using a known method.

[Problem to be solved by the invention] When performing focus detection at multiple distance measuring points on the screen as described above, it is not possible to automatically determine which distance measuring point should be used for focus adjustment based on the distance measuring results. It is important to be able to choose between Taking this point into consideration, a method has been proposed as one method for selecting an optimal distance measurement point, in which focus adjustment is performed based on a sensor output whose distance measurement result indicates the closest distance. However, in boat fishing, there are many cases where the closest subject is not the subject that the photographer wants to photograph. In a multi-point distance measuring device, which has a focus detection means capable of performing focus detection on a large number of distance measuring points, and performs focus adjustment based on the focus detection result of each of the distance measuring points, If the detection result of the AF point that detected the closest distance is closer than the set threshold, focus detection is performed using the second closest AF point, so the subject matches the photographer's intention. However, it becomes possible to automatically adjust the focus.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a multi-point distance measuring device to which the present invention is applied will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram showing an example of a camera focus detection device suitable for implementing the present invention. PRS is a camera control circuit, for example, there is a CPU (central processing unit) inside.
, RAM, ROM, EEPROM (electrically erasable programmable ROM), input/output ports, etc.
It is a chip microcomputer, and a series of camera control software and parameters including various correction data are stored in the ROM and EEPROM.

DBUS is a data bus, and SHT receives data input via the data bus DBUS while the control signal C3HT is input from the control circuit PR5, and runs the front and rear curtains of the shutter (not shown) based on the data. A shutter control circuit APR that performs control receives data input via a data bus DBUS while a control signal CAPR is input, and an aperture control circuit DSP controls an aperture mechanism (not shown) based on the data. sws is a display circuit that accepts data input via the data bus DBUS while the control signal CD5P is input, and displays various shooting information based on the data; sws is a release switch (not shown), and a continuous shooting mode switch It is also a group of switches such as switches for setting various information.

SPC is a photometric circuit, and its output analog photometric signal 5spc is sent to the control circuit PRS, and the circuit PRS
The data is A/D converted in R5 and used as photometric data for controlling the shutter control circuit APR.

While the control signal CLCOM is input, LCOM accepts data input via the data bus DBUS,
A lens communication circuit that performs serial communication with the lens control circuit LNSU based on the data transmits lens drive data DCL to the lens control circuit in synchronization with the clock signal LCK, and at the same time serially inputs lens information DLC. BSY is a signal to notify the camera side that a focusing lens (not shown) is moving, and the serial communication is not performed while this signal is being generated.

SDR is a sensor drive circuit that drives three pairs of sensor arrays SAA according to each signal input from the control circuit PRS.

SAB, ~SAA 3. Has SAB 3. For example, a line sensor SNS such as a CCD is controlled.

When the control circuit PRS sends the accumulation start signal STR to the sensor drive circuit SDR, the sensor drive circuit SDR sends the clear signal C
L is output to the line sensor SNS, and the sensor array SAA, S
The charges of all photoelectric conversion parts AB, -3AA3, and 5AB3 are cleared once. Then, the line sensor SNS is detected by the secondary imaging lens (not shown in Fig. 3, but arranged at 74° in Fig. 7 and 83.84 in Fig. 8) arranged at the front stage. Sensor array SAA,,SAB
1 to SAA 3°SAB 3 Starts photoelectric conversion of the optical image formed on 3 and charge storage operation. The storage time of the sensor is controlled by the sensor drive circuit SDR, and when the sensor storage is completed, the sensor drive circuit SDR outputs a transfer signal SH to the line sensor SNS for the sensor for which the storage has been completed. The charges accumulated in the photoelectric conversion section of the line sensor SNS are transferred to the CCD section by the transfer signal SH. At the same time, the sensor drive circuit SOR outputs an accumulation end signal END and an identification signal ss of the sensor whose accumulation has been completed to the control circuit PR3.
It waits for the CCD drive clock CK to be input from the control circuit PR3. When the CCD drive clock CK is input, the sensor drive circuit SDR outputs the CCD drive signal φ1. φ2 is generated and the signal is output to the line sensor SNS. CCD drive signal φ1. When φ2 is input, the line sensor SNS sends the analog image signal 5SNS to the control circuit P according to this signal.
Output to RS. As a result, the control circuit PR5 outputs the analog image signal 5SNS in synchronization with the CCD drive clock CK.
/D conversion, and the paired image signals are stored at a predetermined address in the RAM.

FIG. 2 is a diagram showing distance measurement positions in the finder, and the light flux passing through the distance measurement area l in the screen is imaged on the sensor SAA, , SAB by the optical system shown in FIG.

Similarly for distance measurement area 2.3, 5AA2, 5AB2
The image is formed at 5AA3 and 5AB3, and the focus state at each location is detected.

FIG. 1 is a flowchart for explaining the operation of this embodiment. AF is a subroutine, and control is started by a subroutine call from the camera's main routine.

(Sl) It is determined here whether this is the first distance measurement calculation.

In the case of the first distance measurement calculation (S2); otherwise (S
Branch to 4).

(S2) Communicates with the lens and inputs lens information into the microcomputer. Reads information such as focal length, close distance, sensitivity coefficient, comb pitch, etc. from the lens.

(S3) Based on the information read in S2, calculate the closest threshold for each ranging area (TH(1), TH(2)).

TH(3)).

This threshold value is set to a different value depending on the distance measurement point.

For example, the threshold values for the left and right focusing points are TH(1) = TH(3) = 2 using the focal length f of the lens.
Set Off. The threshold value for the center is closer than the threshold values for the left and right focusing points (for example, TH(2) = 1
Set it to Off. This is done in consideration of the fact that it is unlikely that something unintended by the photographer will appear in the center of the screen or at a close distance. Further, if it is assumed that the camera is in a close-up state such as with a microlens, the threshold value is lowered by multiplying this threshold value by a constant magnification (less than l).

(S4) Read the current absolute lens position from the lens If the lens does not have absolute position information, place the lens once at the infinite end at an appropriate time such as when the power is turned on, and then store the movement of the lens in a specified memory. (By this, the current lens position can be determined.

(S5) Clear the status flag of the ranging point array and perform initial settings. Accumulation completion flag II+ I2+ '3 and reading completion flag RI for three ranging points 1, 2, and 3.
+ R21R3, calculation end flag CI, C2+ C
There are 3.

(S6) Send a control signal to the distance measuring sensor to start sensor accumulation.

When the storage of the sensor is completed, the sensor driving circuit SDR applies an interrelated signal and performs interrelated processing. When interrelated is applied, it corresponds to the sensor for which storage has been completed. The accumulation completion flag I is set to indicate that accumulation has ended.

(S8) Check whether there is a distance measurement area that has not been read since sensor storage has been completed.

If the sensor storage has been completed and there is a distance measurement area that has not yet been read, the process branches to S9; if the conditions are not met, the process branches to SIO.

(S9) Read the sensor output. A read clock is sent to the sensor, A/D conversion is performed sequentially, and the data is read. A/D converted data undergoes correction calculations and is stored in a predetermined RAM.

A reading end flag R corresponding to the distance measuring point for which data reading has been completed is set, and the process returns to S7.

(SIO) Check if there are any sensor readings that have been completed and correlation calculations have not been performed.

If reading has been completed and there is data for which correlation calculation has not been performed, the process branches to Sll; otherwise, the process returns to S7.

(Sll) Correlation calculation is performed to calculate the image shift amount predeinction value on the sensor. The amount of image shift is calculated using a known method, and the calculated results are stored in a predetermined RAM.

When the correlation calculation is completed, a calculation completion flag is set according to the distance measurement point.

(S12) It is determined whether calculations for all distance measurement points have been completed. If all calculation completion flags are set,
Since the calculations for the three distance measurement points have been completed, the process branches to ■.

If there is a distance measurement point for which calculation has not been completed, the process returns to S27.

(S13) The defocus amount of the lens is determined from the prediction value determined by Sll. The relationship between the prediction value and the defocus amount is determined by the optical parameters of the secondary optical system for focus detection and the photographing lens. Range measurement point 1.2
．． The defocus amount corresponding to 3 is DF (1), DF
(2).

DF (3).

(S14) Defocus amount DF (1) obtained in S13
~DF (3) From the lens position memorized in 84, AD the absolute distance at which the focus of each distance measurement point is being detected (1) ~AD
Find (3).

(S15) Compare AD (1) to AD (3) and rank them in order of distance. Nl12AD (1) ~AD
Enter the distance measuring point number of the closest distance in (3), the distance measuring point number of the second distance to N2, and the distance measuring point number of the farthest distance to N312.

(S16) The closest distance among the measured points is compared with the threshold value. In S15, enter the distance measuring point number of the closest distance (
Since the purpose is to find the distance measurement point N1, the distance measurement distance of the distance measurement point N1 and the threshold values AD (Nl) and TH (Nl) are compared. If the measured distance AD (Nl) is smaller than the threshold value TH (Nl), the process branches to S17.

If it is larger, the process branches to S20.

(S20) It is determined whether the measured distance is continuously increasing. Since the distance measuring points are numbered in order from the left, if N1 to N3 are arranged in order of decreasing distance or increasing distance, it can be determined that the distance measuring ability is continuously increasing.

If it is continuously moving away, the process branches to 318, otherwise the process branches to S19.

(S17) Since the closest point is smaller than the threshold value, the second closest point is selected. The distance measuring point number N2 for the second distance is stored.

(318) If the objects are lined up consecutively, set the focus point to the center (focus point number 2). Selected AF point number 2
remember.

(S19) S16. If there is no branching as determined in S20, the closest distance point is measured.

(S21) When the selection of the selection point is completed, it is determined whether or not the selected distance measurement point is in focus. When in focus, the process branches to S22, and if not in focus, the process branches to S23.

(S22) Displays focus and branches to a post-focus sequence (not shown).

(S23) Drive the lens. Calculates the amount of lens drive, performs lens communication, and performs lens drive control.

After sending the drive signal to the lens, the process returns to the main routine of the camera (not shown).

In the main routine of the camera, after predetermined control is performed, the AF routine is called again.

In this way, selection of the distance measurement position of the multi-point distance measurement device can be realized.

FIG. 6 shows a flowchart of another embodiment of the present invention. The difference between this embodiment and the first embodiment is that a common value is used instead of providing a near point threshold for each distance measurement point.

Furthermore, the central feature is that no threshold value judgment is performed. Steps 81 to S15 are the same as in FIG. 1 except that only one type of threshold value is set in step S3' for setting the threshold value. That is, from 5l to N5, the state of each distance measuring point, the position of the photographing lens, etc. are stored and initial settings are made. S6-S12
performs sensor accumulation, readout, and prediction calculation, and in steps 313 to S15, the defocus amount and distance are determined from the prediction value and order calculations are performed.

(R1) Determine whether the closest point is the center.

If it is in the center, the process branches to R4 and no threshold value judgment is performed. If it is not in the center, branch to R2.

(R2) Compare the L threshold and the closest point. If it is closer than the threshold, it branches to R6, and if it is further away, it branches to R3.

(R3) Similar to S20, it is determined whether the measured distance is continuously increasing. In other words, if AF point 2 (center) is farther than AF point L (left AF point) and AF point 3 (right AF point) is further away, conversely, AF point 3 (Right AF point) is the closest, then AF point 2 (center), and farthest is AF point L (left AF point).
When the conditions are met, the process branches to R4, and when the conditions are not satisfied, the process branches to R5.

(R4) The distance measuring point is determined to be the center (focusing point 2).

(R5) The distance measurement point is determined to be the distance measurement point set at the closest distance.

(S21) to (S23) Similar to FIG. 1, it is determined whether the determined distance measurement point is in focus, and if it is in focus, a display is made, and if it is out of focus, the lens is driven to adjust the focus.

FIG. 9 is a flowchart of another embodiment of the present invention. The difference between this embodiment, the first embodiment, and the second embodiment is that when the distance is closer than the threshold value in the near point threshold judgment,
The focus is adjusted using the central distance measuring point. 5L-31
TH(1) because there is no need to set a threshold for the center in 5S3'.

It is the same as FIG. 1 except that only TH(3) is set. To briefly explain, in S1 to S4, the state of the distance measuring point and the position of the photographic lens are set. In steps 86 to S12, sensor accumulation, data reading, and prediction calculation are performed.

In steps 313 to S15, the amount of defocus of the lens and the distance of each distance measurement point are calculated and compared.

(tl) Determine whether the closest point is at the center Even if the closest point is at the center, the distance measurement point is selected at the center, so if the closest point is at the center, the process branches to (t4).

If one type of periapsis threshold is common, 11 steps are not necessary.

(t2) Compare with the periapsis threshold. If the closest point to the distance-measuring point is closer than a threshold value determined individually for each distance-measuring point, the process branches to t4.

(t3) Same as S20 and R3, it is determined whether the measured distance is continuously moving away, and in such a case, the process branches to t4.

(t4) Select the center as the distance measurement point.

(t5) Select the distance measurement point that measured the closest distance.

(S21) to (S23) Similar to FIG. 1, it is determined whether the determined distance measurement point is in focus, and control is performed for in-focus and out-of-focus states.

〔Effect of the invention〕

As explained above, according to the present invention, as a method of selecting one of the many AF points, a close distance prohibition threshold is provided to select a subject at a close distance that is not intended by the photographer. At the same time, by changing the judgment criteria depending on the position of each AF point and determining the continuity of the detected AF distance, the AF point for the subject that matches the photographer's intention is automatically selected. It is a choice.

[Brief explanation of the drawing]

Fig. 1 is a flowchart of the first embodiment of the present invention, Fig. 2 is a distance measuring point position on the finder, Fig. 3 is a block diagram of a camera for implementing the present invention, Figs. 4 and 5 are A diagram explaining the principle of focus detection, FIG. 6 is a flowchart of the second embodiment of the present invention, FIGS. 7 and 8 are schematic diagrams of an optical system for performing multi-point focus detection, and FIG. 9 is a flowchart of the second embodiment of the present invention. It is a flow chart of an example. In the figure, 41.71 is a photographing lens, 43.73 is a field lens, 44.74 is a secondary optical system, 45 is a photoelectric conversion element array 72.81 is a field mask, PR5 is a microcomputer, spc is a photometry circuit, and SDR is A sensor drive circuit, APR is an aperture control circuit, LCOM is a lens communication circuit, SNS is a line sensor, SHT is a shutter control circuit, and DSP is a display circuit.

Claims (5)

[Claims] (1) In a multi-point distance measuring device that has a focus detection means that can perform focus detection for a large number of distance measurement points in a shooting screen, and adjusts the focus based on the focus detection result of each distance measurement point, If the detection result of the distance measurement point that detected the closest distance among the many distance measurement points is closer than the set threshold,
A multi-point distance measuring device characterized by performing focus detection at the second closest distance measuring point. (2) In a multi-point distance measuring device that has a focus detection means that can perform focus detection for a large number of distance measurement points in a shooting screen, and adjusts the focus based on the focus detection result of each distance measurement point. , when the detection result of the distance measuring point that has detected the closest distance among the plurality of distance measuring points is closer than a set threshold value, the focus is adjusted at the distance measuring point near the center of the screen. Point ranging device. (3) The multi-point measurement according to claims 1 and 2, characterized in that the threshold value is set individually for each distance measurement point position based on the focal length and close range of the photographic lens. range device. (4) In a multi-point distance measuring device that has a focus detection means that can perform focus detection for a large number of distance measurement points in a shooting screen, and adjusts the focus based on the focus detection result of each distance measurement point. , when it is determined that the detection results of the large number of distance measuring points are changing continuously from the edge of the screen, the focus is adjusted at a distance measuring point near the center of the screen. Device. (5) In a multi-point distance measuring device that has a focus detection means that can perform focus detection for a large number of distance measurement points in a shooting screen, and adjusts the focus based on the focus detection result of each distance measurement point. . A multi-point distance measuring device, characterized in that when the focus detection result of the distance measuring point near the center of the screen is the closest distance, the focus is adjusted at the distance measuring point.