JP3187033B2 - Camera auto focus device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus adjusting device for a camera, and more particularly, to an automatic focus adjusting device for a photographing lens such as a camera. The present invention relates to an automatic focusing device for a lens in which the amount and the driving amount of a driving member for a focusing operation have a non-linear relationship.

2. Description of the Related Art As a lens having a non-linear relationship between the amount of extension of the focus group in the optical axis direction and the amount of drive of a driving member for driving the focus group, for example, a lens of the focus group corresponding to the same subject distance is used. The extension amount in the optical axis direction from the infinity position is
There is a zoom lens having a varifocal optical system that differs depending on a set focal length.

In such an optical system, for the same subject distance,
The focal plane moves as the focal length changes due to zooming. In order to correct this focus shift, the amount of extension of the focus group in the optical axis direction must be changed to an appropriate amount with zooming. Then, as a driving method of the optical system in which the focus movement due to such zooming is corrected, a necessary extension amount in the optical axis direction of a focus group different depending on a focal length is approximated by one function,
A distance ring has been proposed in which the range of use of this function is changed according to the focal length.

However, it is difficult to directly obtain such a lens driving amount from a focus shift. That is, when focusing is performed using the distance cam, the rotation angle of the distance ring and the amount of movement of the focus group in the optical axis direction do not have a proportional relationship.
The defocus is a rotation amount of the distance ring, that is, a drive amount for adjusting the focus of the focus group, but could not be converted to that angle. Furthermore, the range of use of the function varies depending on the amount of lens extension or zooming, so that it is increasingly difficult to convert the focus shift into the focus group drive amount for focus adjustment.

Therefore, in order to eliminate such a defect, the driving amount for the focus adjustment necessary for focusing is stored as a data table in the storage unit based on the respective focal length information, the respective extension amounts, and the information on the defocus (a defocus amount). Japanese Patent Application Laid-Open No. 64-59311 proposes a method in which the focus can be adjusted by storing the drive amount and setting the drive amount according to each detection amount.

[Problems to be Solved by the Invention] However, the method disclosed in Japanese Patent Application Laid-Open No. 64-59311 requires a storage unit having a huge storage capacity, and is difficult to realize at present.

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide an optical system having a non-linear relationship between the drive amount of a focus group and the extension amount of the focus group in the optical axis direction. It is an object of the present invention to provide an automatic focusing device for a camera which can be converted into a camera.

[Means and Actions for Solving the Problems] FIGS. 1A to 1C show the concept of the present invention. The automatic focus adjusting device of the camera of the present invention has a basic configuration, as shown in FIG.1A, a non-linear photographing lens in which the relationship between the extension amount of the focus group and the drive amount of the drive member that drives the focus group is nonlinear, Detecting the direction and amount of deviation between the imaging plane of this taking lens and the predetermined imaging plane of the camera,
Displacement information detecting means for outputting them as displacement information,
A focus group shift information determining means for determining a feed direction and a feed amount for moving the focus group to a focus position based on the shift information; and a feed amount for detecting a feed amount of the focus group from a reference position. A predetermined calculation is performed based on a detection unit, an output of the focus group shift information determination unit, an output of the feeding amount detection unit, and a predetermined calculation expression, and the focus group is moved to a focus position. Operating means for determining the amount of driving of the driving member.

[Operation] In this automatic focusing apparatus, the output signal of the shift information detecting means 1 for detecting the shift direction and shift amount of the subject light passing through the photographing lens 5 between the imaging surface and the film surface in the optical axis direction is
On the basis of this output signal, the focus group information determining means 2 which calculates and determines the deviation between the focus position of the focus group of the photographing lens 5 in the optical axis direction and the current position, determines the optical axis of the focus group. The signal is converted into a signal indicating the direction and amount of deviation of the direction. Further, the focus group drive amount calculating means 3 for determining the drive amount of the focus group necessary for focusing from the current extension position of the focus group and information on the shift direction and shift amount of the focus group in the optical axis direction. Then, the focus group driving amount is output. That is, when converting the focus shift into the drive amount of the focus group, first, information on the shift in the optical axis direction of the focal point of the focus group is obtained.
The drive amount of the focus group is obtained.

Further, in a zoom lens having a varifocal optical system in which the amount of extension of the focus group corresponding to the same object distance from the infinity position from the infinity position differs depending on the set focal length, in the optical axis direction of the focus group For a lens or the like that changes the range of use of this function according to the focal length, approximating the required extension amount in the optical axis direction of the focus group that differs depending on the focal length to correct the extension amount according to the focal length, As shown in FIG. 1B, a focal length information detecting means 6 for detecting information from the focal length adjusting optical system 5a.
And based on the set focal length information that is the output,
The focus group shift information determining means 2 converts the output signal of the shift information detecting means 1 into a signal indicating the shift direction and shift amount of the focus group in the optical axis direction according to the set focal length information.

In addition, in the case of the above-described zoom lens, as shown in FIG. 1C, a focal length information detecting means 6 is provided as in FIG. A signal indicating the direction and amount of shift of the focus group in the optical axis direction in accordance with the set focal length information and the current feed position signal of the focus group from the feed amount detection means 4 in the drive amount calculation means 3. Is converted into the focus group drive amount.

Furthermore, as for the equation (function) that determines the shape of the distance cam of the zoom lens as described above, the relationship between the distance of the subject and the amount of extension of the focus group in the optical axis direction with respect to the distance can be well approximated to a first-order hyperbolic function. The error is smaller when the function is set to a hyperbolic function. In particular, the formula of the distance cam is as follows: θ = 0 at the wide end of the lens, θ
Z = B ₀ / (A ₀ + θ) or Z = B ₀ / (A ₀ + θ) −B ₀ / A where Z is the lift amount of the cam, Z is the constant of the distance cam type, and A ₀ · B ₀ is the constant of the distance cam type. _By setting the _value to ₀ , the calculation by the focus group drive amount calculation means 3 can be easily and accurately obtained.

[Embodiment] An embodiment in which the present invention is applied to an interchangeable lens camera having an AF function will be described below.

FIG. 2 is an overall block diagram mainly showing power supply of a camera system to which the present invention is applied. The voltage V _CC of the power battery 11 is boosted by the DC / DC converter 13 when the power switch 12 is closed, and the voltage between the lines l ₀ and l ₁ is made constant at the voltage V _DD . The main CPU14 between line l _0, l _1, bipolar II circuit 15, bipolar I circuit 16, a strobe of control circuit 1
7, lens specific data circuit 18a, lens fixed data circuit 18b,
The power supply control of the bipolar II circuit 15 is performed by a signal from the power control circuit of the main CPU, and the power supply control of the bipolar I circuit 16 to the data back circuit 19 is controlled by the bipolar II circuit 15.
This is performed by a power control signal from the controller.

AF consisting of focus sensor 20, A / D converter 21, and AF CPU 22
The block is connected via the power control transistor 23
l _0, which is connected between l _1, on of the transistor 23 the power supply control for the AF block by the signal from the AF power control circuit of the main CPU 14, is performed by the off control. The AF CPU 22 is a circuit for performing an algorithm operation for AF, and displays in-focus and out-of-focus.
The AF display circuit 24 is connected. The main CPU 14 is wound up,
A circuit for controlling the sequence of the entire camera, such as a rewinding and exposure sequence, is connected to a display circuit 25 for performing a display other than the in-focus display. Bipolar II circuit
Reference numeral 15 denotes a circuit including various drivers necessary for a camera sequence, such as a motor control for winding and rewinding, lens driving and shutter control, and the like.
Etc. are connected. The bipolar I circuit 16 is a circuit mainly responsible for photometry, and has a photometric element 28.
The flash control circuit 17 controls the light emission of a built-in or external flash 29. The lens-specific data circuit 18a is different for each interchangeable lens, AF,
This is a circuit that stores unique lens data necessary for photometry and other camera control. This lens specific data circuit 18
Among the lens data contained in a, the data necessary for AF include lens zooming coefficient (optimal AF coefficient), macro identification signal, absolute distance coefficient a, b, power focus duty coefficient, magnification coefficient, AF accuracy threshold ETh , Lens moving direction, open F value, and the like. For these data, the storage unit to be read is changed according to the information on the set focal length, and the data is switched as needed. The lens fixed data circuit 18b is a circuit that stores data necessary for a fixed operation that does not differ for each interchangeable lens. The data of the lens specific data circuit 18a and the data of the lens fixed data circuit 18b may be stored in a memory such as the main CPU 14 or the AF CPU 22 in the camera.

The bipolar II circuit 15 monitors the state of the power supply voltage V _DD , and sends a system reset signal to the main CPU 14 when the power supply voltage falls below a specified voltage, and
The circuit 15 to the power supply of the data back circuit 19, and the AF including the focus sensor 20, the A / D converter 21 and the AF CPU 22
The power supply of the block is cut off. Main CPU1
Power supply to 4 is performed even at a specified voltage or less.

FIG. 3 is a system diagram showing transmission and reception of signals centering on the AF block. The CPU 22 for AF and the main CPU 14 exchange data through a serial communication line, and the communication direction is controlled by a serial control line.
The contents of the communication include unique lens data in the lens unique data circuit 18a and absolute distance information. Further, the information of the camera mode (AF single mode / AF sequence mode / power focus (hereinafter abbreviated as PF) mode / other modes) is decoded from the main CPU 14 to the AF CPU 22 through the mode line. In addition, the AFENA (AF
The enable) signal controls the start and stop of each mode of AF and PF, and the EOFAF (end of AF) signal from the AF CPU 22 to the main CPU 14 is AF and PF.
This signal is issued at the end of the operation in the mode and permits the shift to the exposure sequence.

Further, the bipolar II circuit 15 decodes the signal of the AF motor control line from the AF CPU 22 and drives the AF motor drive circuit 26. When the AF motor (lens drive motor) 31 rotates by the output of the AF motor drive circuit 26, the slits 32 provided at equal intervals in the rotating member of the lens barrel rotate, and the light emitting unit 33a sandwiches the passage of the slit 32. The photointerrupter 33 in which the light-receiving unit 33b and the light-receiving unit 33b are opposed to each other counts the slit 32. That is, the slit 32 and the photo interrupter 33 constitute a lens movement amount detection unit 34, and the address signal (the count signal of the slit 32) emitted from the movement amount detection unit 34 is shaped into a waveform, and the AF CPU 22
It is taken in.

The sub lamp (hereinafter abbreviated as S lamp) signal sent from the AF CPU 22 to the bipolar II circuit 15 is an AF auxiliary light circuit.
The S lamp 27a is turned on when the subject is low light (low brightness) and low contrast.

The AF display circuit 24 connected to the AF CPU 22 has an in-focus indication LED (light emitting diode) 24a that lights up when focusing and an in-focus indication LED 24b that lights up when focusing is impossible. A clock oscillator 35 and a reset capacitor 36 are connected to the AF CPU 22.

The AF CPU 22 and the A / D converter 21 exchange data via a bus line, and the transmission direction is controlled by a bus line control signal. And AF CP
A sensor switching signal and a system clock signal are sent from the U22 to the A / D converter 21. And A / D
For example, the converter 21 sends a CCD drive clock signal and a CCD control signal to a focus sensor 20 composed of a CCD, reads a CCD output from the focus sensor 20, converts the read analog output of the CCD output into a digital signal, and performs AF conversion. Send to CPU22.

Next, the taking lens optical system attached to the camera having the automatic focusing device of the present invention will be described with reference to FIG. This taking lens optical system may be fixed to the camera body or may be replaceable. Further, the optical system is not limited to the one described in the present embodiment, and may be any lens as long as it is a lens for photographing a camera.

In this photographing lens optical system, the extension amount of the focus group corresponding to the same subject distance from the infinity position in the optical axis direction is
The zoom lens includes five groups that are different depending on the set focal length. That is, the lenses L _{1 to} L ₃
The first group consisting of, a second group consisting of L ₄ ~L _7, a third group consisting of L ₈ ~L _10, the fifth group consisting of the fourth group and consisting of _{L 11 ~L 14 L 15, L} 16 It is composed of a lens optical system, and the state shown in FIG. 11 shows the state at the telephoto end having the maximum focal length.

This zoom lens has a focal length of 131.5044 mm on the tele side and 36.2932 mm on the wide side.

The following Table 2 shows data on the focal length, principal point position, and group thickness of each lens group.

In this zoom lens optical system, the position of the first group lens to the fourth group lens is changed by the zooming operation, and the fifth group lens is fixed so as not to move. Further, the change in the interval between the lens groups is not constant, and the interval at which the change occurs is represented by D1 and D2, as shown in FIG.
The third group interval is D2, the third to fourth group interval is D3, the fourth to fifth
Table 3 shows the interval data of each group for each focal length, with the group interval being D4.

Table 3 also shows data on the amount of zoom operation. The zoom operation amount is an operation amount (rotation amount) of a zoom ring for zooming the lens. The total operation amount of the zoom ring from the wide state to the telephoto state of the zoom lens is 73.5 degrees. The zoom operation amounts in Table 3 are based on the wide. The position of the optical system is changed by operating the zoom ring, and the focal lengths shown in the table are obtained. This focal length is at infinity.

The focus adjustment of this lens is performed by moving the first and second units by the same amount along the optical axis. Table 4 shows the amount of extension of the focus group for each focal length shown in Table 3 according to the subject distance.

As shown in Table 4, the subject distance is from infinity to 1.
2m. In the case of the nearest 1.2m, the extension amount of 0.58934mm in wide, whereas the extension amount of 2.66037mm in tele is necessary.

That is, in this zoom lens, the amount of extension of the focus group corresponding to the same subject distance in the optical axis direction differs depending on the focal length changed by the zooming operation. Then, a zooming focus movement also occurs. For this reason, the amount of feeding different depending on the focal length is approximated by one function, and the zooming focus movement is corrected by changing the use range of this function according to the set focal length. The distance cam function used for this extension is as follows: θ = 0 at the wide end of the lens, θ is plus in the closest direction / telescopic direction, A ₀
If B ₀ is a constant of the distance cam function, the function value Z (θ) at θ is: Z (θ) = B ₀ / (A ₀ + θ) −B ₀ / A ₀ (1) And the constants A ₀ and B ₀ are optimized so as to eliminate the zooming focus movement. For optimization, the focus group extension amount according to the subject distance (1.2 m) for each focal length, and the use range change amount (7
3.5 degrees) and the use range (36.75 degrees) of the function according to the subject distance. In other words, θ corresponding to wide infinity is 0 degree, and 36.75 at the nearest 1.2 m.
Degrees, θ corresponding to tele infinity is 73.5 degrees, close to tele 1.
At 2 m, θ becomes 110.25 degrees. At this time, the optimized constant of the distance cam function is A ₀ = −160.877879 (angle unit system) and B ₀ = −320.240186 (angle unit system). FIG. 12 shows a shape based on this distance cam function. The line drawn by the solid curve is the shape of the distance cam. The circles on the line indicate the extended positions at the nearest 1.2 m at each focal length. XA in the figure is a ₀ value is the distance the cam constant A ₀ and B, shown in XB. Also, S, Are the sum of squares of the error and the average value of the error, respectively. As described above, according to the distance cam determined by the above method, the shift of the focus group extension amount due to zooming when the subject distance is 1.2 m is about 0.00001 mm on average.

The drive pulse actually used for driving this lens system is set to 1406.4 pulses for an angle of 36.75 degrees of the distance cam. In the unit system using this pulse, the constants A ₀ and B ₀ of the optimized distance cam function are as follows: A ₀ = −6156.698050 (drive pulse unit system) B ₀ = −12255.396077 (drive pulse unit system) Become.

Next, each focal length (36.2932 to 13
Table 5 below shows a list of defocus data according to the subject distance in 1.5044) as a defocus table. The subject distance is infinity (indicated by 99999.99mm in the table), 8000mm, 6000mm, 4000mm, 3000mm, 2000
mm, 1600 mm and 1200 mm. The abscissa represents the extension position of the lens corresponding to each subject distance, and the ordinate represents the distance of the subject glaring at the lens.

In FIGS. 13 and 14, the defocusing shown in Table 5 above and the defocusing (d) occurred in wide (focal length 36.293 mm) and tele (focal length 131.504 mm), respectively. 7 shows a graph of a focus group extension amount (L) necessary for occasionally moving a focus group and focusing.
In this graph, the circles indicate the data of the focus shift shown in Table 5 and the amount of extension of the focus group necessary for focusing. The solid line indicates the relationship between the focus shift (d) and the amount of focus group extension (L) required for focusing by the least squares method using the data of (d) and (L). Using the AF coefficients A, B, and C, L = {B} − {A · B / (A + d)} + {C · d}
.. (2). The error between this approximation formula and the actually required feeding amount is 0.0001 mm or less for both wide and excessive. In the tele, it is about 0.001mm for both over and under. Table 6 shows the optimized AF coefficients A, B, and C optimized for each focal length.

Next, an algorithm for converting a focus shift into a drive amount for focusing the focus group will be described with reference to FIG.

This part corresponds to the focus group shift information determination means 2 and the focus group drive amount calculation means 3 in FIG.

First, the focus error information (d) from the shift information detecting means 1 for detecting the shift direction and the shift amount of the focus is converted into the focal point detected by the focal length detecting means 9 in the optimum AF calculating section 7 (focus group shift information determining section). Using the optimum AF coefficients A, B, and C in the lens-specific data storage circuit section 18a suitable for the distance information, the data is converted into the movement amount (L) in the optical axis direction necessary for focusing of the focus group. Defocus information (d) unit [m
m], and if the unit of the required movement amount of the focus group is [mm], (L) can be obtained by using the coefficients in Table 6 and Expression (2).

Thereafter, the distance ring rotation amount calculation unit (focus group drive amount calculation means) 8 stores the information of the movement amount L in the optical axis direction necessary for focusing of the focus group in the unique data storage circuit unit 18a of the lens. Alternatively, the distance cam function is converted from the constants A ₀ and B ₀ of the distance cam function written as an immediate value in the calculation program and the distance cam function into the rotation amount (focus group drive amount) of the distance ring for AF. The arithmetic expression at this time is as shown in FIG. 16, where S1: the amount of rotation of the distance cam due to zooming S2: the amount of distance cam used for extending the lens during distance measurement P: the distance ring for AF Rotation amount L: Movement amount in the optical axis direction necessary for focusing of focus group x0: Total lift amount of distance cam at expected focus position x1: Lift amount of distance cam by S1 x2: Lift amount of distance cam by S2 When, L = x0- (x1 + x2 ) a distance cam function expression from _{(1), x0 = B 0} / (a 0 + S1 + S2 + P) -B 0 / a 0 x1 = B 0 / (a 0 + S1) -B 0 _{/ A 0 x2 + x1 = B} 0 / (A 0 + S1 + S2) -B 0 / A 0 ∴L = B 0 / (A 0 + S1 + S2 + P) -B 0 / (A 0 + S1 + S2) ∴P = B 0 / (L + (B 0 / (A ₀ + S 1 + S 2)) − (A ₀ + S 1 + S 2), an arithmetic expression for obtaining the amount of rotation of the distance ring necessary for focusing for AF is derived.

Similar results can be obtained by using Z (θ) = B ₀ / (A ₀ + θ) instead of the above equation (1).

The rotation amount of the distance cam due to the zooming in the above (S1) is the zoom operation amount shown in FIG. This may be extracted from the unique data storage unit of the lens according to the focal length information as shown in FIG. 15, or if the detected focal length information is based on the rotation amount of the distance cam, It may be obtained as it is or by calculation. In order to express the angle in a pulse unit system indicating the position of the focus group, the data in Table 3 may be multiplied by the number of pulses per unit rotation angle (1406.4 pulses / 36.75 degrees in this embodiment).

Since the optical system of this embodiment is a zoom lens, focal length information is required for calculation. In particular, this is a zoom lens in which the extension amount of the focus group according to the subject at the same distance differs depending on the focal length, and a mechanism for correcting this characteristic is incorporated. Therefore, a value corresponding to the focal length and the amount of extension of the focus group is required. As described above, the calculation of this part may be set in accordance with the characteristics of each lens. The point is that the calculation of the drive amount of the focus group necessary for focusing on the information of the focus shift is performed.

Next, an algorithm for calculating the absolute distance of the subject to be focused will be described.

First, from the signal from the above-described focus group drive amount calculation means and the signal of the extension position at which the focus group is currently stopped, the extension amount (x) from the reference position of the focus group at which an ideal focusing state is obtained. Ask.

As described above, in the present embodiment, the signal from the focus group drive amount calculating means as the shift between the focus extension position of the focus group and the current extension position and the reference position at which the focus group is currently stopped (this embodiment) (Infinity position at infinity) is used to predict and calculate the amount of focus from the reference position of the focus group that is ideally focused on the subject, and the value is used to determine the absolute distance of the subject.

Next, a description will be given of a flowchart of a program operation of the microcomputer centering on the AF block shown in FIG. 3 of the camera having the automatic focusing apparatus of the present invention. The AF block is, as shown in FIG.
By turning on the AF power control circuit 4, the transistor 23 is turned on to supply the power supply voltage V _DD , thereby starting the execution of the power-on reset routine shown in FIG.

When this power-on reset routine starts,
First, the drive circuit of the AF block is initialized in the <I / O Initialize> subroutine. Specifically, the AF display circuit 24, the AF motor drive circuit 26, the AF auxiliary light circuit 27, etc. are turned off, and the serial communication line with the main CPU 14 is initialized.

Next, in the <mode read> subroutine,
After reading out the mode line signal (mode signal) from the CPU 14 and determining which lens drive mode to execute, a certain period of time is passed in the <timer> routine, and the mode is read again through the <mode read> routine. The switching point is read. Then, the process returns to the first <mode read> until the mode switching is completed. The reason why the <mode read> subroutine is passed twice with the <timer> interposed is to prevent erroneous reading at the time of mode switching.

When the mode switching is securely performed and the mode before and after the switching becomes the same, the mode after the switching is read and the process proceeds to the subroutine of each mode. That is, the lens driving modes include <lens reset>, <PF
(Power Focus)>, <AFSIN (AF Single)>,
There are <AFSEQ (AF sequence)> modes, and when one of these modes is selected, the subroutine of the selected mode is executed, and then the routine returns to the <I / O initialize> routine. <Lens reset>, <PF
When none of the modes>, <AFSIN>, and <AFSEQ> is selected, and when the <other> mode is selected, this is regarded as mere noise, and a certain time elapses in the <timer> routine. Then, the process returns to <I / O Initialize>.

Here, in the operation of the <lens reset> mode, the lens is forcibly moved to the position at infinity (∞), whereby the relative distance signal, that is, the distance measurement output signal output from the focus sensor 20 is output. This is an initialization operation for converting the number of pulse movements from the position at infinity (∞) to an absolute distance signal, that is, an operation for clearing an absolute distance counter. If <lens reset> is selected,
After clearing the absolute distance counter, for example, after 5 ms, the process returns to the I / O initializing operation. In the <PF> mode, the distance ring of the lens is driven not by the manual operation but by the lens driving motor 31, and the focusing operation of the lens is performed by using the manual focusing or the focus aid. More specifically,
It described later PFUP (up) for operating switch SW _1, PFDN (down) for operating switch SW ₂ on, feeding of the lens by off, so that the renormalization is performed. Also, <
The operation in the mode AFSIN> is a one-shot AF operation in which focus is locked after an AF operation is performed on a subject. Further, the <AFSEQ> mode is continuous AF, and in this mode, the AF operation is continuously performed as long as the first step of the release button is continuously operated.

Meanwhile, as the operation switch for each mode of the lens driving, as shown in Table 1 below, four operation switches SW ₁ to SW ₄ is used.

The first and second operation switches SW ₁ and SW ₂ shown in Table ₁ are A
Are those commonly used in the F mode and the PF mode, the third operation switch SW ₃ is AF mode when off, is PF mode when on is selected. In the AF mode, when both the first and second operation switches SW ₁ and SW ₂ are off, the lens reset mode is set.
Operation switch SW ₁ is turned off, the second operation switch SW ₂ is AFSIN mode when on the. When the first and second operation switches SW ₁ and SW ₂ are both off or both on in the PF mode, the stop mode is set. When the first operation switch SW ₁ is on, the distance ring is moved by the motor to a short distance. rotate the side becomes PFUP (up) mode for feeding the lens, the second operation switch SW ₂ is renormalize the lens by rotating the distance ring far side when on PFDN (down) mode. The fourth operating switch SW ₄ of, on in any mode of the AF mode, in any off, also there on, any off at the stop mode of the PF mode There is no change, but when the PF mode is on, the HI (high-speed) mode is set and the lens drive motor
31 rotates at high speed and coarse movement of the distance ring is performed.
In the (low speed) mode, the motor 31 (see FIG. 3) rotates at a low speed to perform fine movement of the distance ring.

Next, the operation of each lens drive mode will be described with reference to the flowcharts of FIGS.

When the mode of <AFSIN> is selected, the routine of <AFSIN> shown in FIG.
Detects whether the AFENA signal is at "H" level (active). AFENA with the first operation of the release button
The signal becomes active, AF operation starts, and <AFSIN2
> Subroutine is called. However, the operation of the second stage of the release button is accepted when the AF operation is completed, a focused state is obtained, and the exposure sequence is started. In <AFSIN2>, as described later, the focus sensor 20
CCD integration, distance measurement output calculation, lens driving, and the like are performed. After the operation of <AFSIN2>, the AF status flag is monitored after the operation of <AFSIN2>. The AF status flag is a low contrast flag (a flag that is set to “1” when the subject has low contrast; hereinafter, abbreviated as an LC flag), a movement flag (a flag that is set to “1” when the subject is moving, , M flag) and the closest flag (a flag that is set to “1” when the lens is extended more than the closest distance, hereinafter abbreviated as N flag). Focusing is possible when any of the flags is “0”, and focusing is not possible if any of the above flags is set. Therefore, as a result of monitoring the AF status flag, the AF status flag is “0”. If there is, the indication of in-focus OK is displayed by the LED 24a of the AF display circuit 24.
If the AF status flag is not "0", the LED 24b indicates that focusing is impossible. And
If it is not in focus, it waits until the AFENA signal goes to "L" level, and returns when it goes to "L" level. If the camera is in focus, an EOFAF signal is issued, the AF operation ends, and the main CPU
At 14, the operation of the second stage of the release button, that is, the start of the exposure sequence is awaited. Then, the AFENA signal is checked. In other words, once focusing is completed,
Even if the AFENA signal is active, the subsequent lens operation is prohibited and the in-focus indication LED 24a remains lit, resulting in a focus locked state. A from main CPU 14
When the FENA signal becomes "L" level (inactive), the process returns to the initial operation of the power-on reset flow shown in FIG.

During the operation of the <AFSIN> mode, the program operation of the <AFSIN2> subroutine is performed as shown in FIG. First, the previous distance calculation value (the previous focus sensor
The RETRY (retry) flag is cleared for comparison with the current distance calculation value (the current output pulse of the focus sensor 20) and the current distance calculation value (the output pulse of 20).
The maximum number of times of distance measurement in the operation is set. after this,
The maximum value of the CCD integration time is set in the ITIME register to ensure that the CCD integration is performed above a certain brightness. Then, the AF status flag is cleared, and the S lamp flag is also cleared. AF with the operation up to this point
The initialization operation before starting is completed. After this,
The routine of <lens read> is called, and after reading out each data in the lens in the lens specific data circuit 18a, the routine of <AF> for distance measurement is called. In the subroutine of <AF>, it is determined whether or not the S lamp 27a needs to be turned on at the time of the CCD integration. If the S lamp 27a needs to be turned on, the S lamp flag is set. You. Also, a low light flag (a flag set to “1” when the subject is low light, hereinafter abbreviated as an LL flag) and an LC flag are set or cleared.

If both the LL flag and the LC flag are cleared after the distance measurement operation of <AF>, the routine of <pulse> is called to calculate the lens drive amount.

In this <pulse> routine, as shown in FIGS. 7A and 7B, the AF (ranging) calculation output value obtained in the <AF> routine is converted into a focus group drive amount for each photographing lens. For this purpose, necessary data specific to the lens (information on the optimum AF coefficients A, B, C and the rotation amount of the distance cam corresponding to the focal length) is read out from the specific data circuit 18a according to the focal length set. Next, based on the read optimal AF coefficient and the AF calculation output value, information on the drive amount in the optical axis direction of the focus group from the current focus group position to the in-focus position is calculated. After that, based on the amount of rotation of the distance cam according to the set focal length, information on the current position of the focus group, and information on the amount of movement of the focus group in the optical axis direction, focus taking into account the shape of the non-linear distance cam The number of pulses (address signals) (LPLS) corresponding to the drive amount of the group is calculated.

Next, in the <Pulse> subroutine, the number of pulses (LPLS) corresponding to the amount of movement from the current position to the planned in-focus position
Is obtained, and before the lens is driven into the in-focus state, a subroutine of <OBJDATA> for obtaining the absolute distance and the photographing magnification of the subject is executed.

FIG. 8 is a flowchart of the subroutine <OBJDATA>. In the figure, it is checked whether or not the direction in which the photographing lens is moved is from the infinity end to the closest end. If <extending direction>, the number of pulses (DISCNT) from the infinity end at the current position of the focus group of the photographing lens set in the absolute distance counter,
The number of pulses (LPL) corresponding to the amount of movement from the current position obtained in the <pulse> routine to the in-focus
S) is added, and the result is stored as the number of pulses (OBJPLS) from the infinity end of the expected in-focus position of the subject. If it is not <extending direction>, that is, if it is the extending direction, subtract the number of pulses (LPLS) corresponding to the moving amount from the current position to the expected focusing position from the number of pulses from the infinity end at the current position (DISCNT). The result of this subtraction is stored as the number of pulses (OBJPLS) from the infinity end of the expected focusing position. The result of this subtraction is negative,
In other words, if <Borrow> appears, the in-focus position will be closer to infinity than at infinity, but since this is not corrected again, <OBJPLS ← 0>, ie, the infinity end of the in-focus position Set the number of pulses from (OBJPLS) to 0. In this case, the distance measurement accuracy can be improved.

The number of pulses (OBJPLS) from the end at infinity at the expected in-focus position obtained by adding or subtracting according to the extension direction and the extension direction as described above is obtained by reading <absolute distance coefficients a, b and magnification coefficient>. Routine-specific lens data circuit
The object distance (OBJDIST) is calculated by the routine of <OBJDIST ← OBJPLS, absolute distance coefficient> using the absolute distance coefficients a and b corresponding to the set focal length read from 18a.
Is required. In addition, the number of pulses (OBJPLS) from the infinity end at the above-mentioned in-focus position is calculated by the above <absolute distance coefficient
a, b, and magnification factor read> in the routine of <OBJMUL ← OBJPLS, magnification coefficient> are calculated by the magnification coefficient corresponding to the set focal length read from the lens-specific data circuit 18a in the routine of Magnification (OBJMU
L) is required. By the way, the above <absolute distance coefficients a, b,
Read magnification factor> in the routine of lens specific data circuit 18.
The absolute distance coefficients a and b and the magnification coefficient read out from a can be selected or corrected and used in the focal length and the macro range in accordance with them. Then, these object distance (OBJDIST) and photographing magnification (OBJMUL) are <OBJDIST, O
BJMUL communication> is transmitted to the main CPU 14 in the routine.

The main CPU 14 uses the object distance (OBJDIST) and the magnification (OBJMUL) received in <OBJDIST, OBJMUL reception> to <
It is determined whether strobe parallax correction> or <auto zoom> is necessary. If necessary, zooming calculation for <strobe parallax correction> or <auto zoom drive> is performed. The CPU 14 drives an actuator for parallax correction and a zoom actuator based on the calculation result in parallel with lens driving for focus adjustment described later.

As described above, according to the present invention, the lens extension position that would be in an ideal in-focus state is obtained from the lens drive amount until focusing and the current lens extension amount, and the subject is focused before the lens is driven. Calculate the absolute distance and shooting magnification when focusing.

Thereafter, the AF calculation output value (ERROR) and the AF accuracy threshold E read out from the lens-specific data circuit 18a are obtained.
If the AF operation output value (ERROR) is larger than the AF accuracy threshold ETh, the process proceeds to step S <b> 3 to determine the RETRY flag. In the first AF operation, since the RETRY flag is set to "0", the drive pulse number is saved after the RETRY flag is set. And
Since the RETRY flag is set in the second and subsequent AF operations, the number of current driving pulses is compared with the number of previous driving pulses. At this time, if the current pulse number is smaller by the moving amount than the previous pulse number, it means that the lens is closer to the focal point by driving the lens, so that in the next lens driving, it is even closer. Therefore, the current pulse is saved instead of the previous pulse, and the <MDRIVAF> routine is called to drive the lens. The number of drive pulses from the infinity (∞) position of the distance ring is set in the absolute distance counter.

The purpose of comparing the previous pulse and this pulse is AF
The purpose is to prevent the diverging operation of the entire sequence. As a way of comparing the two, (current pulse number): (previous pulse number × 0.5) or (current pulse number): (previous pulse number × 1.5) can be considered. If the AF sequence system is likely to be in a divergent state, the AF operation may be performed while the subject is moving. In this case, stop the lens drive immediately and use the M flag to prevent waste of the AF operation. Set and return.

After the lens is driven by the above <MDRIVAF>, 1 is subtracted from the number of times of distance measurement of the AF operation set in the AF loop counter. As a result, if the value of the AF loop counter is not 0, the integration time is set in the ITIME register, and the AFENA signal is activated (that is, the operation of the first stage of the release button is turned on). , Return to for the next AF operation. In this way, the value of the AF loop counter is decreased by one each time the AF operation between-is repeated, so that
When the AF calculation output value (ERROR) does not become smaller than the AF accuracy threshold ETh even if the value of the AF loop counter becomes 0, the M flag is set as being impossible to focus. Will be done.

As a result of the AF operation between-, when ERROR <ETh,
That is, when the AF calculation output value (ERROR) falls within the focus error range, the AF status flag is cleared, indicating that the camera has come into focus, and the routine returns.

Here, after the operation of <AF>, if the LL flag or
If the LC flag is set, the state of the S ramp flag is tested. At this time, if the S ramp flag has been set to “1” in advance, during the integration operation for AF, S
Low light, despite lamp 27a being on,
In this case, the LC flag is tested again.In this case, only in the case of low contrast, the <lens NF (unfocusable)> routine is called, and an aggressive display indicating that focus is not possible is performed. Do. That is, in this <lens NF> routine, first, the lens is first extended to the closest position, then extended to the infinity (位置) position, and a large movement of the lens actively disables focusing. Notify the user. It should be noted that the lens operation indicating the inability to focus may be an operation of extending from the infinity (遠) position to the closest position. In addition, in this <lens NF>, an absolute distance counter for saving the number of drive pulses (number of moving address signals) from the infinity (∞) position of the lens distance ring by hitting the lens at infinity (∞) position. Is initialized. If the contrast is not low, it means that the AF operation has been performed while the light is low, and in this case, the process returns to.

When the S lamp flag has been cleared in advance, the S lamp 27a has been turned off before. Therefore, if the LL flag or the LC flag is set, the S lamp flag is set. Proceed to. Therefore,
The S lamp 27a is turned on in the second and subsequent AF operations.

Also, if the subject is moving, that is, if it is a moving object, it is also possible to obtain the speed of the subject's movement by measuring the subject distance multiple times, taking into account the amount of movement of the subject during AF driving, AF that follows the moving object becomes possible. The multiple AF operations may be performed with the AF drive interposed. It is also possible to predict the movement of the moving body, predict a time delay such as a mirror-up, and set a predicted driving amount when performing AF driving.

FIG. 9 is a flowchart of a subroutine <AFSIN2A> for tracking and AF of such a moving object. Only routines related to moving object tracking in the flowchart of the subroutine <AFSIN2> shown in FIG. 6 are extracted. It is shown. In the figure, the description of the routine already described with reference to FIG. 6 is omitted, and only the description of the change routine will be made.

In FIG. 9, <AF>, <pulse>, <OBJDIST>
The information of the subject distance (OBJDIST) and the photographing magnification (OBJMUL) obtained by performing signal processing in the subroutine is determined in the <focus determination> routine to determine whether or not the subject is in focus.
If the information is in the in-focus state, the flow shown in FIG. 5 <AFSIN>
Subroutine (AFSIN2) is followed by <Return>. If out of focus, the routine proceeds to a routine to determine whether or not <First AF>. If it is the first AF, then go to <MDRIVAF>.
Not, that is, if AF has been performed multiple times,
JDIST-this time OBJDIST> is obtained and the routine proceeds to a routine for determining its size. If the difference between the previous information and the current information of the subject distance information (OBJDIST) obtained by the routine of <previous OBJDIST-current OBJDIST> is large, <pulse correction> is performed, and if it is sufficiently small, <MDRIVAF> To the routine. Next, the routine proceeds to a routine for determining whether or not <predictive AF>, and the purpose of moving object tracking is to track the moving object to obtain a subject distance and to move the moving object between the end of AF and the actual shooting. In the case of the predictive AF that predicts a position that will be present and focuses on the predicted position, it is useless to perform any further AF. Therefore, after the subroutine <AFSIN2> in the flow of <AFSIN> shown in FIG. <Return> to the routine. If it is not <Predictive AF>, <Last OBJD
Proceeding to the routine of IST ← OBJDIST>, the information of the subject distance (OBJDIST) obtained this time is stored in the memory area for storing the previously obtained subject distance (OBJDIST) information, and then the subroutine of <AF> above And the above operation is repeated until the focus is determined.

In the above-described embodiment, lens-specific data necessary for calculation, such as absolute distance coefficients a and b and a magnification coefficient, are stored in the lens-specific data circuit 18a and read and used. In a camera or the like in which the lens is fixed, if the data unique to the lens is written as an immediate value in a program, it goes without saying that the storage circuit can be omitted.

In the above-described embodiment, the absolute distance and the photographing magnification of the subject are obtained before the AF focus determination. However, as shown in FIG. 10, the <OBJDATA> routine is executed only after the focus determination. Even in such a case, the absolute distance and the photographing magnification of the subject corresponding to the ideal focusing position can be obtained.

[Effects of the Invention] As described above, according to the present invention, in a photographing lens in which the amount of extension of the focus group and the amount of drive of the drive member that drives the focus group are nonlinear, the amount of defocus on the film surface is reduced. , The amount of focus group extended from the reference position,
Since the zooming position is obtained as necessary, a predetermined calculation is executed based on these, and the driving amount of the driving member for driving the focus group is directly obtained, so that the focusing accuracy can be improved by a simple configuration. Can provide an automatic focusing device for a camera that is easy to use.

[Brief description of the drawings]

1A to 1C are conceptual diagrams of an automatic focusing device for a camera of the present invention, FIG. 2 is a block diagram of an electric circuit mainly for power supply of a camera system to which the present invention is applied, and FIG. 4 is a block diagram showing the transmission and reception of signals centered on the AF block in FIG. 2. FIGS. 4 to 10 show program operations centered on the AF CPU shown in FIG. FIG. 11 is a configuration diagram of a photographing optical system including a zoom lens used in an embodiment of the present invention. FIG. 12 is a diagram illustrating a relationship between a distance cam function and a cam lift amount. Fig. 13 and Fig. 14 are graphs showing the relationship between the amount of focus and the amount of defocus required for focusing in wide and telephoto, respectively. Fig. 15 shows the focus shift and the focus group. Block diagram for explaining an algorithm for converting into a drive amount for causing The lift amount of distance the cam and the distance the rotation of the cam is a graph showing the relationship between the rotation amount of the distance ring. DESCRIPTION OF REFERENCE NUMERALS 1: shift information detecting means 2: focus lens group shift information determining means 3: focus lens group drive amount calculating means 4 ... extension amount detecting means 5: photographing lens

Claims (3)

(57) [Claims] 1. A photographing lens in which the relationship between the amount of extension of a focus group and the amount of driving of a driving member for driving the focus group is nonlinear, and a shift between an image plane formed by the photographing lens and a predetermined image plane of the camera. A shift information detecting means for detecting a direction and a shift amount, and outputting them as shift information; and a focus group for determining a feed direction and a feed amount for moving the focus group to a focus position based on the shift information. A shift information determining unit, a feed amount detecting unit that detects a feed amount of the focus group from a reference position, an output of the focus group shift information determining unit, an output of the feed amount detecting unit, and a predetermined arithmetic expression. Calculating means for executing a predetermined calculation based on the above, and determining a drive amount of the drive member for moving the focus group to a focus position. Automatic focusing device of La. 2. A photographic lens including a variable power system and a focus group, wherein the relationship between the amount of extension of the focus group and the amount of drive of a drive member for driving the focus group is non-linear, and an image plane formed by the photographic lens. A shift information detecting means for detecting a shift direction and a shift amount between the focus group and a predetermined imaging plane of the camera, and outputting them as shift information; and for moving the focus group to a focus position based on the shift information. A focus group shift information determining means for determining a feeding direction and a feeding amount; a feeding amount detecting means for detecting a feeding amount of the focus group from a reference position; and detecting a focal length information according to a position of the zoom system. A focal length information detecting unit, an output of the focus group shift information determining unit, an output of the feeding amount detecting unit, an output of the focal length information detecting unit, and a predetermined arithmetic expression. Run the constant of the operation,
Calculating means for determining a drive amount of the drive member for moving the focus group to a focus position. 3. The automatic focus adjusting device for a camera according to claim 2, wherein the photographing lens adjusts a focal length in cooperation with the focus group and the variable power system.