JPH03150536A - Lens driving device for optical equipment - Google Patents

Abstract

PURPOSE:To shorten a focusing time without wasting a time for lens driving by deciding whether or not backlash removal is necessary and inhibiting a backlash removing means from operating when it is decided that the backlash removal is unnecessary. CONSTITUTION:A microcomputer PRS carries out a series of operations of a camera such as an automatic exposure control function, an automatic focus detecting function, and film winding according to the sequence program of the camera stored in a ROM. The microcomputer PRS makes communications with the peripheral circuit of a camera main body and a lens by using synchronous communication signals SO, SI, and SCLK and communication select signals CLCM, CSDR, and CDDR to control the operations of respective circuits and the lens. The lens FLNS receives driving instructions, a defocusing quantity, and the number of driving pulses from the camera, calculates a backlash quantity on a focus plane, and compares it with focusing width to decide whether or not the backlash removing operation of a gear train (GTR) needs to be performed. When the removing operation is not necessary, normal lens driving is performed immediately. Consequently, the focusing time can be shortened without wasting the time for the lens driving.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a lens of an optical device such as a camera that detects the amount of defocus and drives a focus lens with a motor based on the detection signal to move it to the in-focus position. This relates to a drive device.

(Background of the Invention) In an autofocus camera, in order to stop the focus lens within the focusing width, if the amount of defocus on the focus plane (hereinafter referred to as defocus amount) is small, the lens is moved at a low speed. When the amount of defocus is large, the lens is driven at high speed until a predetermined amount before the in-focus point, and then driven at a low speed to accurately stop the focus lens at the in-focus point. The device is JP-A-56-94334 and JP-A-58-18.
No. 60, Japanese Unexamined Patent Publication No. 59-26709, and many others.

In addition, in order to eliminate backlash in the driving force transmission mechanism, that is, the gear train, etc., the present applicant disclosed Japanese Patent Application Laid-Open No. 63-17
No. 2240 is proposed.

The outline of the automatic focus adjustment method in these applications is as follows.

]) Defocus amount DEF is detected by a focus detection device.

2) Convert the defocus amount DEF to the focus lens drive amount DL using the sensitivity S determined by (defocus amount/focus lens extension amount). The conversion formula at this time is DL=DEF/S. Sensitivity S is S for a single lens with full extension.
It can be considered to be constant at cape 1, but in the case of a zoom lens, it changes depending on zooming, that is, the focal length, and in the case of an inner focus type lens, it also changes depending on focusing.

3) Converting the focus lens driving amount DL to the rotation amount of the lens driving actuator. The amount of rotation in this case is usually expressed by the number of output pulses FP of an encoder that monitors the amount of rotation of the actuator, and FP=DL/PTH. PTH is a coefficient of "focus lens drive amount versus number of pulses" determined by the lead of the helicoid screw of the focus lens and the gear ratio of the gear train of the drive force transmission system.

4) According to the calculated value of the number of pulses FP, the focus actuator is driven according to a predetermined acceleration/deceleration pattern, and the focus lens reaches the expected focus position.

5) Perform the focus detection in 1) again, and if the defocus amount is within the predetermined focusing width, it is determined that the focus is in focus and the series of focusing operations is aborted; if it is outside the predetermined focusing width, the focus detection described in 2) above is performed. Continue the following sequence.

By the way, in such a method, the sensitivity S is used when determining the focus lens drive amount DL from the defocus amount DEF, but when driving the focus lens, the drive pattern is determined only by rDLJ or "FP". It is unrelated to the sensitivity S. This situation can be seen at 35-105mm/F.
4, a lens with P T H = 0.01 will be explained as an example.

Generally, in a zoom lens, the sensitivity S changes in proportion to the square of the focal length f. That is, when f=35mm, S=0.
5, when f = 105mm, S = 4
．． 5, which is a very high sensitivity. On the other hand, the focusing width is determined by the F number, but in the lens of this example, it is constant over the entire area, so the focusing width does not depend on the focusing distance and is constant. Here, the focusing width is ±0.1 mm (on the focal plane). Then, the value of the ratio of "r focusing width to the amount of focus movement per pulse" is the smallest at the telephoto end (f = 105 mm1), so it depends on the resolution of the encoder, the gear ratio of the gear train, and the speed when driving the focus lens, that is, the acceleration. The deceleration pattern and the like are set so that a predetermined lens stopping accuracy can be obtained at the telephoto end.

Under these properties, DE at f = 105 mm
DEF=1 when F=9mm and when f=35mm
Let's compare it with the case of mm. In this case, the driving amount of the focus lens is the same in both cases as DL=2 mm, and the number of driving pulses is also the same as F P =200 pulses. Therefore, in both cases, since the motor is driven with the same acceleration/deceleration pattern, the driving time T and the stopping precision δFP are also the same. Here, it is assumed that T2O is 2 seconds and δFP=±1 pulse. Then, the stopping accuracy δ on the focus plane is f = 10
When it is 5mm, δ=±45μm and the focusing width is ±0.1m.
Although this is an appropriate value for m, when f = 35 mm, the accuracy is δ = ±5.0 μm, which can be said to be a little excessive. The acceleration/deceleration pattern at this time will be explained with reference to FIGS. 9 and 10.

In FIG. 9, the horizontal axis is the number of driving pulses, and the linear axis is the driving speed. And the required drive amount FP is FP.

The acceleration/deceleration curves A1 to A8 are shown at the time of . First, the maximum speed ω1 is reached when the FP is first accelerated and pulse driven. reach. Then, it enters deceleration at a point before the FP pulse from the target stop point, is then driven at a constant speed ω1゜1, and is braked at a point before the FPc pulse from the target stop point to overrun by a predetermined amount and reach the target point. Stop.

B+, Ba to B6 are cases in which the required drive amount F P 2 is smaller than FPI, in which case the motor is decelerated before reaching the maximum speed ωl1laX, and after driving at ω1°, the brake is applied to stop the motor.

The curve shown by Cr, C4, and Cs is the drive amount FP3
is even smaller and is less than or equal to FPb.

FIG. 10 shows the relationship between time and speed, where the horizontal axis is the time from the start of lens driving, and the vertical axis is the driving speed. And curves D1 to D in the figure.

are curves A1 to As in Fig. 9, El and E3 to E6 are B.
1. B3 to B5, F+, F4. Fs is C+, C4
, Cs.

First, to explain Do-Ds, which corresponds to F P + pulse drive, a minute voltage is applied to the focus lens drive motor in the section where gear train backlash removal (backlash removal) is performed until time to. Eliminates gear backlash between the motor and helicoid. Therefore, during this period, pulses may be input sporadically to the pulse encoder, but since the driving force is small, the focus lens is not moving, and therefore the pulses during this period are not counted. After that, acceleration, maximum speed ω□8 drive, deceleration, constant speed ω
After passing through the 1°1 drive region, the brakes are applied and the vehicle comes to a stop. Also, the curve corresponding to FP2 pulse drive is Do
, El, Ea to Ea, the curve corresponding to FP3 pulse drive is Do+D+.

F4. FB, and their total driving time is T'+
, Tx, T3. These drive patterns are determined only by the required drive amount FP, regardless of the sensitivity S of the focus lens.

What is characteristic here is that the backlash removal, constant speed ω1°, and drive region occupy a very large proportion of the entire drive time. That is, the backlash removal operation, which does not actually contribute to lens driving, and the constant speed control operation, which accounts for a small proportion of the total driving amount, occupy a considerably large proportion of time. Therefore, if both of these times can be shortened, the driving time can be considerably shortened. However, since the constant speed control operation is necessary to ensure the accuracy of stopping the lens, it cannot be abolished easily. However, when considering the necessity of backlash removal, the following can be said.

1) When the sensitivity is small In this case, as explained earlier, the amount of image plane movement on the focal plane per pulse is small, so the amount of backlash is determined by the amount of image plane movement on the focal plane. As long as the converted value is sufficiently smaller than the in-focus width, there is no harm even if backlash removal is not performed.

2) When the required amount of lens drive is large This is when the amount of defocus is large, but in general, the accuracy of focus detection becomes worse as the amount of defocus increases. Therefore, when the focus detection accuracy is greater than the driving error on the focal plane due to not performing backlash removal, it is useless to perform backlash removal.

That is, in the cases 1) and 2) above, it is meaningless to perform the backlash removal operation.

However, in the conventional example described above, the backlash removal operation is performed in any case, so the lens driving time is extended by the time required for this operation, resulting in a problem that the focusing time becomes longer than necessary. was there.

(Objective of the Invention) An object of the present invention is to provide a lens driving device for an optical device that can solve the above-mentioned problems and shorten the focusing time without wasting time on unnecessary lens driving. be.

(Features of the Invention) In order to achieve the above object, the present invention determines whether or not it is necessary to perform backlash removal, and if it is determined that it is unnecessary, prohibits the operation of the backlash removal means. A control means is provided so that, for example, when the calculated amount of backlash is smaller than a value corresponding to a width that can be considered as in-focus, the backlash removal operation is not performed and the operation immediately proceeds to the next operation. It is characterized by what it did.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 3 shows a focus lens drive control pattern in the first embodiment of the present invention. In this figure, the horizontal axis is time and the vertical axis is focus lens drive speed, which corresponds to the conventional example shown in FIG. 10 described above. It is something. In this first embodiment, it is determined whether or not backlash removal is necessary depending on the magnitude of the sensitivity S, and FIG. 3 is a drive pattern diagram when backlash removal is not required. That is, before driving the lens, it is determined whether the sensitivity is large or small, and when the sensitivity is high, it is necessary to remove backlash, so the same driving as in FIG. 10 is performed, and when the sensitivity is low, the same drive as shown in FIG. It is designed to be driven. On the other hand, the relationship between the number of drive pulses and the drive speed in FIG. 9 is the same between the conventional example and this embodiment.

Note that a detailed explanation will be given with reference to flowcharts shown in FIGS. 1 and 2, which will be described later.

FIG. 4 is a diagram showing a camera and lens equipped with an automatic focusing device according to the first embodiment of the present invention, which drives the lens shown in FIG. 3 above.

In FIG. 4, PR3 is a camera control device (hereinafter referred to as a microcomputer), which is, for example, a one-chip microcomputer that internally has a CPU (central processing unit), ROM, RAM, and A/D conversion function. The microcomputer PR3 performs a series of camera operations such as an automatic exposure control function, an automatic focus detection function, and film winding according to a camera sequence program stored in the ROM. Therefore, the microcomputer PR3 uses the synchronous communication signals So, SI, and SCL and the communication selection signals CLCM, C3DR, and CDOR to communicate with the peripheral circuits and lenses within the camera body, and controls the operation of each circuit and lens. Control.

The aforementioned communication signal SO is a data signal output from the microcomputer PR3, SI is a data signal input to the microcomputer PR3, and SC[, is a synchronization clock of the signals so and sr.

LCM is a lens communication buffer circuit, which supplies power to the lens power supply terminal when the camera is in operation, and connects the camera and lens when the selection signal CLCM from the microcomputer PR3 is at a high potential level (hereinafter referred to as °H°). Serves as an inter-communication buffer.

When the microcomputer PR3 sets CLCM to H and sends out predetermined data as the signal SO in synchronization with 5CLK, the LC
M is SCLM, So
The respective buffer signals LCK and DCL are output to the lens. At the same time, the buffer signal of the signal DLC from the lens is output as the signal SI, and the microcomputer PR3 outputs the 5CLK signal.
The lens data is inputted to the signal Sl in synchronization with .

The SDR is a drive circuit for the z-line sensor device SNS for focus detection, which is composed of a COD, etc., and the signal C3D
It is selected when R is H' and is controlled by the microcomputer PR3 using signals SO, SI, and SCL.

The signal CK is the COD drive clock φ1. The signal INTEND is a clock for generating φ2, and the signal INTEND is a signal that notifies the microcomputer PR5 that the accumulation operation has ended.

The output signal O8 of the line sensor device SNS is the clock φ1
．． It is a time-series image signal synchronized with φ2, and the drive circuit SD
After being amplified by the amplifier circuit in R, it is output to the microcomputer PR3 as a signal AO3. The microcomputer PR3 receives the signal A
Input O3 from the analog input terminal, synchronize with GK,
After A/D conversion by an internal A/D conversion function, the data is sequentially stored at a predetermined address in RAM.

5AG which is also the output signal of the line sensor device SNS
C is AGC (automatic gain control: Au
This is the output of the sensor for Ga1n Control), is input to the drive circuit SDR, and is used for the horizontal storage control of the device SNS.

SPC is a photometric sensor for exposure control that receives light from a subject through a photographic lens, and its output signal is 5spc.
is input to the analog input terminal of microcomputer PR5, and A/
After D conversion, automatic exposure control (A
E).

DDR is a switch detection and display circuit, and the signal CD
Selected when DR is H°, the signal 5O1S I,
It is controlled by the microcomputer PR3 using the SCL. In other words, the display on the camera's display member DSP can be switched based on the data sent from the microcomputer PR3, and the on/off status of various camera operating members can be controlled by the microcomputer P through communication.
Notify R5.

SWI and SW2 are switches linked to a release button (not shown); when the release button is pressed to the first stage, the switch SWI is turned on, and when the release button is pressed to the second stage, the switch SW2 is turned on. As will be described later, the microcomputer PR3 performs photometry and automatic focus adjustment when the switch SWI is turned on, and performs exposure control and film winding when the switch SW2 is turned on as a trigger. In addition, switch SW2
is connected to the "interrupt input terminal" of the microcomputer PRS, and even if the program is being executed when the switch SWI is on, an interrupt is generated when the switch SW2 is turned on, so that the microcomputer PR5 can immediately shift to a predetermined interrupt program.

MTRI is for film feeding, MTR2 is for mirror up/
This is a motor for down and shutter spring charging, and forward and reverse rotation is controlled by respective drive circuits MDRI and MDR2. Motor MDRI M from microcomputer PR3
[Signals MIF, MIR, M2 input to 1I12
F and M2R are signals for motor control.

MGI and MG2 are magnets for starting the movement of the front and rear shutter curtains, respectively, and are energized by signals SMGI, 5MG2 and amplification transistors TRI and TR2, and shutter control is performed by a microcomputer PR3.

In addition, switch detection and display circuit DDR.

Since the motor drive circuits MDRI, MDR2 and shutter control are not directly related to the present invention, detailed explanations thereof will be omitted.

There is a lens drive control circuit LCNT in the lens FLNS, and the circuit LCNT has a microcomputer LPR3.
R3 exchanges various signals and performs various controls.

The signal DCL input to the Myjin LPR3 in synchronization with the signal LCK is data of a command from the camera to the lens FLNS, and the operation of the lens in response to the command is determined in advance.

The microcomputer LPR3 analyzes the command according to a predetermined procedure, performs focus adjustment and aperture control operations, and outputs the signal DLC.
various operating conditions of the lens (how much the focusing optical system has worked, how many steps the aperture is stopped down, etc.) and parameters (open F number, focal length, coefficient of defocus amount vs. extension amount, etc.) Outputs.

This embodiment shows an example of a zoom lens, and when a focus adjustment command is sent from a camera, the focus adjustment motor LMTR is activated according to the driving amount and direction sent at the same time.
is driven by signals LMF and LMR to move the optical system in the optical axis direction via gear train GTR to perform focus adjustment. The amount of movement of the optical system is monitored by the pulse signal 5ENCP of the encoder circuit ENCP, and the lens drive control circuit L
Counting is performed by a counter in CNT, and when a predetermined movement is completed, the circuit LCNT itself outputs signals LMF and LMR.
The motor LMTR is controlled by controlling the motor LMTR. In addition, the circuit L
The structure of CNT will be explained in detail later.

Therefore, once the focus adjustment command is sent from the camera, the microcomputer PRS, which is the control device inside the camera,
There is no need to be involved in driving the lens at all until the driving of the lens is completed. Furthermore, the configuration is such that it is possible to send the contents of the counter to the camera if necessary.

When an aperture control command is sent from the camera, a stepping motor DMTR, which is known for driving an aperture, is driven in accordance with the number of aperture stages sent at the same time.

ENCZ is an encoder circuit attached to the zoom optical system, and the microcomputer LPR3 receives a signal 5ENCZ from the encoder circuit ENCZ to detect the zoom position.

ENCF is an encoder circuit attached to the focusing optical system, and the microcomputer LPR3 is the encoder circuit ENC.
The focus lens position is detected by inputting the signal 5ENCF from F.

Lens parameters at each zoom position and focus lens position are stored in the microcomputer LPR3, and when a request is made from the camera side microcomputer PR3, the parameters corresponding to each current position are sent to the camera. do.

FIG. 5 is a diagram showing in detail the lens drive control circuit LCNT, etc. included in the lens FLNS shown in FIG. 4.

1 is a control device consisting of a microcomputer, which corresponds to the microcomputer LPR3 in FIG.
Similarly, there is a CPU and ROM inside.

It has RAM, A/D and D/A conversion circuits, etc. And the control device 1 (hereinafter the microcomputer LPR as shown in FIG. 3)
S) controls the drive of a focus lens drive motor 1MTR1 and an aperture drive stepping motor DMTR in accordance with a sequence program stored in the ROM.

Further, the lens drive amount calculated by the in-camera microcomputer PR8 is input to the microcomputer LPR3 via a buffer circuit LCM, and a motor drive circuit 7. A motor drive signal and speed data are output to the constant speed control circuit 8.

2 is an encoder circuit attached to the zoom optical system, which corresponds to ENCZ in Fig. 4, and the zoom state is changed to 4bi by moving the brush linked to the zoom optical system over the pattern.
It is output to the microcomputer LPR3 as information on t.

3 is an encoder circuit attached to the focusing optical system, which corresponds to ENCF in Fig. 4. As the brush linked to the focus lens moves on the pattern, information regarding the position of the focus lens is sent to the microcomputer LPR3 as 4-bit information. Output.

7 is a motor LMTR (30) for driving the focus lens
8 is a constant speed control circuit that drives motor LMTR at a constant speed; 10 is motor LMTR;
A pulse detection circuit 9 (corresponding to the encoder circuit ENCP in FIG. 4) that outputs a pulse with a frequency proportional to the rotation speed of the pulse detection circuit 10 is an f/v conversion circuit that outputs a voltage corresponding to the frequency of the pulse from the pulse detection circuit 10. It is. 6 is a down counter, which is set to a predetermined value (the number of lens drive pulses corresponding to the defocus amount calculated by PR3 in the camera) from the microcomputer LPR3, and
When a pulse signal is input, the counter value is counted down and the counter value, that is, how far the focus lens has moved in the optical axis direction (how much movement remains to reach the target position) is sent to the microcomputer LPR3. Output at any time.

Further, the motor drive circuit 7 has second to fifth input terminals 7b, 7c, 7d, and 7e connected to the microcomputer LPR3, and "H" is applied to these input terminals 7b, 7c, 7d, and 7e.
By inputting the L' digital signal, the motor LMT
The output voltage of the constant speed control circuit 8 is input to the first input terminal 7a, and a voltage approximately equal to the input voltage is applied to the motor LMTR. is applied to start and stop the motor LMTR in a predetermined direction according to the input states of the second to fifth input terminals.

Next, the configuration of each circuit block will be explained according to FIG.

In the motor drive circuit 7, as shown in FIG. 5, first to fourth transistors 21, 22, 23, 24 constitute a transistor bridge, and are connected to the motor LMTR. The bases of the first and third transistors 21 and 23 have a first
and second buffers 19 and 20 are connected, and the input terminals of the first and second buffers 19 and 20 are connected to a resistor 17, respectively.
．． It is connected to the output terminal 8c of the constant speed control circuit 8 via 18. In addition, the first and second buffers 19, 20
The input terminals of are connected to the third and fourth buffers 11 and 14, respectively.
It is connected to microcomputer LPR3 via. 3rd and 4th
Since the output stage of the buffers 11 and 14 is an oven collector, when the level of the second input terminal 7e of the motor drive circuit 7 connected to the third buffer 11 becomes H, the first buffer 19 The voltage output to the output terminal 8C of the constant speed control circuit 8 is directly applied to the input terminal of the constant speed control circuit 8. Similarly, when the level of the fifth input terminal 7b of the motor drive circuit 7 connected to the fourth buffer 14 becomes H', the constant speed control circuit 8 is connected to the input terminal of the second buffer 20. The voltage to be output is applied to the output terminal 8C of. Further, the second to fifth input terminals 7b of the motor drive circuit 7
For states 7e to 7e, combinations other than those shown in the table below are prohibited.
In each state, the motor LMTR is in the state shown in the table below.

Table Here, when the motor LMTR is in the forward or reverse rotation state, the output voltage of the substantially constant speed control circuit 8 is applied between the terminals of the motor LMTR. Note that 25 to 27 are diodes.

In the constant speed control circuit 8, 29 is a differential amplifier, and the voltage input to the first input terminal 8a and the second input terminal 8b are
Outputs the difference between the input voltages. 48 is an operational amplifier, which connects the voltage input to the first input terminal 8a to resistors 31 to 34.
Amplify and output at a magnification determined by . The output of the differential amplifier 29 is input to the buffer 36 via the resistor 47, and the output of the operational amplifier 48 is input to the buffer 36 via the resistor 35.

With the above configuration, the constant speed control circuit 8 is controlled by the microcomputer L.
The voltage corresponding to the motor rotation speed specified by PR3 (this is a signal converted to an analog value by D/A conversion in the microcomputer LPR3) multiplied by a predetermined coefficient by the difference between the specified speed and the actual speed. The voltage obtained by superimposing the voltages is output to the output terminal 8c.

The f/v conversion circuit 9 is a monostable multi-bi break 3
7, a filter circuit consisting of resistors 38 and 39, and a capacitor 40, and a buffer 41, which are well-known circuits, output a voltage approximately proportional to the frequency of the pulse input to the monostable multi-vibration break 37 to the output terminal 9b.

The pulse detection circuit 10 (ENCP) is a well-known pulse detection circuit consisting of a photoreflector and a pulse plate. The pulse plate 44 has reflective and non-reflective surfaces alternately provided on its surface, and rotates in synchronization with the rotation of the motor LMTR. The light emitting diode 42 is driven by a constant current circuit 43. The collector of the phototransistor 46 is connected to a power supply via a resistor 45 and to an input terminal of a Schmitt trigger circuit 49 . When the light from the light emitting diode 42 is reflected on the reflective surface of the pulse plate 44 and input to the phototransistor 46, the output level of the pulse detection circuit 10 becomes H°, and the light from the light emitting diode 42 is absorbed by the non-reflective surface of the pulse plate 44. When the pulse plate 44 rotates in synchronization with the rotation of the motor LMTR, the pulse detection circuit IO generates a pulse with a frequency proportional to the rotation speed of the motor LMTR. Output.

The lens drive control device LCNT configured in this manner controls the rotation of the motor LMTR to move the focus lens along the optical axis direction, as shown in FIG. 9 or FIG. 3.

Next, the focus detection and lens driving operations according to this embodiment will be explained with reference to the flowcharts of FIGS. 1 and 2.

Figure 2 is a flowchart showing a series of camera operations.
When a power switch (not shown) is turned on, power supply to the microcomputer PR3 is started, and the microcomputer PR3 starts executing the sequence program stored in the ROM.

First, when the execution of the program is started by the above operation (power switch on), the state of the switch SWI, which is turned on by pressing the release button in the first step, is detected in step (001) and step (002).
When the WI is off, the process moves to step (003), where all control flags and variables set in the RAM in the microcomputer PRS are cleared and initialized. Above step (0
Steps 02) to (003) are repeatedly executed until the SWI is turned on or the power switch is turned off.

Step (002) is started by turning on the switch SWI.
) to step (004).

In step (004), first, communication is performed with the microcomputer LPR3 in the lens FLNS, and the microcomputer LPR3
Receives lens information necessary for focus detection and photometry stored in the ROM.

In step (005), a "photometering" subroutine for exposure control is executed. The microcomputer PR3 inputs the output signal 5spc of the photometry sensor SPC shown in Fig. 4 to the analog input terminal, performs A/D conversion, and calculates the optimal shutter control value and aperture control value from the digital photometry value. Then, each of them is stored at a predetermined address of the microcomputer PR3. During the release operation, the shutter and aperture are controlled based on these values.

Subsequently, in step (006), the "image signal manual input" subroutine is executed.

7 In the next step (007), the defocus amount DEF of the photographic lens is calculated based on the manually generated image signal.

Note that the subroutines of steps (005) to (007) are well known, and detailed explanations thereof will be omitted.

The next step (008) is as explained in the background of the invention. D L = D E F/5 FP=DL/PTH The number of lens drive pulses FP is calculated according to the formula.

In step (009), a lens drive start command is sent, and the defocus amount DEF and the number of pulses FP are also sent. Then, the lens FLNS controls the drive of the focus lens by FP pulses in accordance with a predetermined program built into the microcomputer LPR3, and then transmits a drive completion signal to the camera side.

In step (010), this drive completion signal is received.

8 One cycle of focus adjustment operation is completed through the flow of these steps (004) to (010), and after that, the process returns to step (002) and moves on to the next focus adjustment operation again.

Next, the above steps (006) to (01
0) A case where a release interrupt occurs due to switch SW2 being turned on during execution will be explained.

As explained earlier, the switch SW2 is connected to the interrupt input terminal of the microcomputer PR3, and is configured so that when the switch SW2 is turned on, the interrupt function immediately moves to step (011) even if any step is being executed. ing.

Step (011) while executing the step surrounded by a broken line
When the "rSW2 interrupt" is input, if the focus is being detected, the operation is immediately stopped, and if the lens is being driven, a signal is sent to the lens FLNS to forcibly stop the lens in step (012).

Next, a release operation is performed in steps (013) to (017).

First, in step (013), the quick return mirror of the camera is raised. This is executed by controlling the motor MTR2 via the drive circuit MDR2 using the motor control signals M2F and M2R shown in FIG.

In the next step (014), the aperture control value already stored in the "photometering" subroutine of the previous step (O05) is sent to the lens FLNS, and the lens FLNS is caused to perform aperture control.

In step (015), the shutter is controlled using the shutter control value already stored in the "photometering" subroutine of the previous step (005), and the film is exposed.

When the shutter control described above is completed, the next step (01
In step 6), a command is sent to the lens FLNS to open the aperture, and then in step (017) the mirror is lowered. Similar to mirror up, mirror down uses motor control signals M2F and M2R to control motor MTR.
This is executed by controlling 2.

Now that the release operation has been completed, step (018)
), the film is wound up and the process returns to step (002).

Next, the operation during lens drive control will be explained with reference to FIG.

The flowchart shown in FIG. 1 is the flow within the lens FLNS in the portions shown in steps (009) and (010) of the flow in FIG.

First, in step (102), along with a drive start command from the camera, the defocus amount DEF and the number of drive pulses F
Enter P.

In the next step (103), R in the microcomputer LPR3
The sensitivity S data stored in the OM is read out as follows.

First, the microcomputer LPR5 detects the state of the zoom encoder ENCZ(2) in FIG. 4.5, and outputs the zoom signal 5.
Input ENCZ, then detect the state of focus lens encoder ENCF (3) and output focus signal 5EN.
Enter CF. Then, since the sensitivity S is stored in the ROM as a matrix state S = S (5ENCZ, 5ENCF) with these signals 5ENCZ and 5ENCF as parameters, the current signals 5ENCZ,
The value of sensitivity S corresponding to 5ENCF is read and used.

At the next step (104), the previous step (103)
Using the sensitivity S read out, the backlash data FPex (pulse) of the gear train GTR built in the ROM, and the PTH mentioned above, δ=S*DL =S*PTH*FPaK On the focus plane by backlash FPBX Calculate the amount of image movement (backlash amount) δ at .

The next step (105) is to determine the size of the movement amount δ,
This is a step of determining whether or not to perform backlash removal. Here, W is a focusing width, and kl is a certain constant coefficient, both of which are values stored in the ROM of the LPR 3 within the lens. For example, W=±0.1mm, k+=0
．． 2, kl-W=20 μm, so if the backlash amount δ calculated in step (104) is 6220 μm, perform the backlash removal operation from step (106) onwards, and δ
<If it is 20 μm, proceed to step (111) and do not perform the backlash removal operation.

In step (106), the counter 6 and the microcomputer LPR
Clear the value of the built-in timer in 3.

The next steps (107) to (110) are the flow of backlash removal.

First, in step (107), an extremely low speed signal ωBK for backlash removal is stored in the set speed ω, and in step (108), the motor is started. In the following explanation, the set speed ω (analog value) is transmitted from the microcomputer LPR3 to the terminal 8 of the constant speed control circuit 8 in FIG.
It is assumed that this signal is input to a and becomes the speed command signal.

At this time, if there is backlash in the gear train GTR, the counter 6 subtracts the counter content from "0". Then, when the backlash is removed and the pulse is no longer output, the output 9b from the f/v conversion circuit 9 becomes "
0'', so the constant speed control circuit 8 is (difference between 8a and 8b) x
(constant magnification), that is, output (8a x constant magnification) to terminal 8
Take it out from c. Here, the signal to terminal 8a is ω□,
Since this is a fairly small value, the signal from the terminal 8c is also small, and therefore, the setting is such that the rotation of the motor by the voltage from the terminal 8c can only remove backlash, but cannot drive the focus lens. In addition, the upper limit of the amount of backlash is almost determined by the configuration of the gear train GTR, so in this flow, when the amount of pulse generation during backlash removal exceeds the upper limit FP, it is possible to immediately proceed to the next step. It is configured.

Since backlash removal has started in step (108), the contents of counter 6 are checked in the next step (109). Since the counter 6 is a down counter, the contents of the counter are negative during backlash removal. Therefore, in step (109), if 1 counter content 1≧FPeK, it means that the backlash has been completely removed, so the process moves to step (111). 1 If the counter content I becomes FPB, step (
110).

Step (110) is a step for regulating the upper limit time for backlash removal, and is a set time t, which is the elapsed time from step (106). If not, the process returns to step (109) to continue the backlash removal operation. When the timer≧to, the backlash removal operation is shifted to the next regular lens drive operation.

The steps after step (111) are the normal lens drive flow.
First, in step (111), the number FP of lens drive pulses is stored in the counter 6.

Next, in step (112), it is determined whether the number of drive pulses is large or small. The counter contents are the deceleration section F P shown in Figure 9.
If it is more than b, high-speed driving is performed, so step (1, 13)
Store ``ωmay J'' in the set speed ω at .Then, ω
Since the D/A conversion value of is inputted manually to the terminal 8a in FIG. 5, the motor LMTR accelerates to drive at the maximum speed ωmmN,
When the maximum speed reaches ωmax, driving continues at that speed.

If the counter content becomes <FPゎ from the above state, or if the initial drive amount FP is FP<FP, the process moves from step (112) to step (114), where ω is set to ``ω1゜1. ” is stored.

The next step (115) is to judge whether the counter contents have become less than or equal to the set overrun amount FP,v.If the counter contents≦FP,v, the next step (
116), the motor LMTR is braked, and the lens overruns by a predetermined amount and stops exactly at the target position. Note that FP, . . . is also data stored in the ROM.

In step (117), the completion of lens driving is communicated to the camera side, and this completes a series of lens driving operations.

Rereading the above flow, in Figures 1, 9, 10, and 3, the lens FLNS first receives a drive command, defocus amount, and number of drive pulses from the camera in step (102). It takes 3 days. Then, in (103) to (105), the amount of backlash δ on the focus plane is calculated and this is compared with the in-focus width to determine whether or not a backlash removal operation is necessary.

If the removal operation is unnecessary, normal lens driving is immediately performed from step (111), and if the removal operation is necessary, backlash removal is performed at steps (106) to (110).

Subsequently, regular lens driving is performed in steps (111) to (116), and lens driving is completed in step (117).

As a result, when backlash removal is performed, the driving pattern becomes as shown in Figure 10, while when it is not performed, the driving pattern becomes as shown in Figure 3. In this case, the driving time, that is, the focusing time, is shortened. be done.

In the first embodiment, the determination of whether backlash has been removed or not is made by comparing the backlash conversion amount on the focus plane with the in-focus width. A second embodiment will be described below.

It was explained earlier that the number of lens driving pulses FP is calculated in the camera using the following formula. Here, the sensitivity S is originally a value that changes steplessly according to the zoom and focus lens positions, but in reality, it is a discrete value stored in the ROM corresponding to the divided areas of the zoom and focus lenses. This value has a certain degree of error from the true value. For example, this error is 2 months%, or 2%.
= 0.01, if k2・FP>FP□,
The drive error due to calculation error is larger than the drive error due to backlash. Therefore, in this case, backlash removal has no effect.

FIG. 7 is a diagram showing the drive pattern of this embodiment, and
, E3 to Es are F+, F4 in case of FP2 pulse drive
, Fs is in the case of FP3 pulse drive, k2・FPz,
Both 2 and FP are smaller than FPBK, indicating that backlash is removed. On the other hand, G, ~G6
is FP, pulse drive, k il+ F P +
> Since it is F P 8, backlash removal is not performed.

FIG. 6 shows the flow of this embodiment. This flow corresponds to steps (103) to (015) of the first embodiment in FIG.
) is simply replaced with step (201), only the changed part will be explained, other identical parts will be indicated by the same step numbers, and redundant explanation will be omitted.

In step (102), the defocus amount DE is determined from the camera.
When F and FP are input, it is determined in step (201) whether backlash removal is to be performed. And k
If 2.FP≧FPBK, backlash removal has no effect, so proceed to step (111) and k2.FP
<FPBK, the process advances to step (106) to remove backlash. From this point on, the operation is the same as in the first embodiment.

Note that when it is determined in step (201) that 2.FP≧FPa, it is a case where the amount of driving error is expected to be large, so in such a case, regardless of the presence or absence of backlash removal. Generally, the object does not come into focus with the first AF operation, but focuses with the second AP operation.

Therefore, if the backlash removal operation can be omitted in the first AF operation as in this embodiment, the total focusing time can be shortened accordingly.

Next, a third embodiment of the present invention will be described.

In general, focus detection accuracy decreases depending on the magnitude of the defocus amount DEF. The cause is ■) Aberration of the focus detection optical system.

2) At the time of large defocus, the image on the focus detection sensor becomes blurred and the contrast decreases.

Due to etc. If this focus detection error is larger than the drive error due to backlash, the backlash removal operation becomes meaningless. Therefore, FIG. 8 shows a lens drive control flow in such a case.

In step (102), rDEFJrFPJ is read from the camera, and in steps (103) and (1n04), the value δ, which is the backlash amount F P s converted to the focal plane, is calculated as δ=S'kPTH*FPex. . This part is the same as the first embodiment.

In the next steps (301) and (302), the backlash amount δ on the focus plane and the focus detection error amount D
E F err is compared and it is determined whether backlash removal is to be performed or not. Here, the error amount D E F
Although err depends on various factors such as the characteristics of the subject, the characteristics of the photographing lens, and the characteristics of the focus detection optical system, it can be roughly considered that it is proportional to the defocus amount DEF. Therefore, in this embodiment, D E F err = k s * D E F. Here, 3 is a constant determined mainly by the characteristics of the focus detection device. Then, in step 301, the focus detection error amount is calculated according to the above formula.

In the next step 302, if δ≧D E F err, it is determined that backlash removal is necessary, and step (
Backlash removal is performed in steps 106) to (110),
If δ<D E F err, it is determined that backlash removal is unnecessary, and the lens is driven from step (111) onwards.

According to this embodiment, it is determined whether or not the backlash removal operation of the gear train GTR is necessary (step (1) in FIG. 1).
05), Figure 6 step (201), Figure 8 Step (
302)) However, if the backlash removal operation is not necessary, the operation is not performed.
As can be seen from the figure, the lens driving time, that is, the focusing time can be shortened.

(Correspondence between the invention and the embodiment) In this embodiment, the gear train GTR is used as the transmission means of the present invention in steps (105) and (2) of the microcomputer LPR5.
01) or the part that performs the operation of step (302) corresponds to the operation control means, and the part that performs the operation of steps (106) to (109) corresponds to the backlash removal means.

(Effects of the Invention) As explained above, according to the present invention, it is determined whether or not it is necessary to perform backlash removal, and when it is determined that it is unnecessary, the operation of prohibiting the operation of the backlash removal means is performed. A control means is provided so that, for example, when the calculated amount of backlash is smaller than a value corresponding to a width that can be considered as in-focus, the backlash removal operation is not performed and the operation immediately proceeds to the next operation. This makes it possible to shorten focusing time without wasting time on unnecessary lens driving.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation in an embodiment of the present invention, FIG. 2 is a flowchart showing the operation during lens drive control, FIG. 3 is a diagram showing the relationship between time and lens drive speed, and FIG. The figure is a circuit diagram showing a camera and lens according to each embodiment of the present invention, FIG. 5 is a detailed circuit diagram inside the lens shown in FIG. 4, and FIG. 6 is a circuit diagram showing the operation in the second embodiment of the present invention. Flow chart, FIG. 7 is a diagram showing the relationship between time 3 and lens driving speed, FIG. 8 is a flow chart showing the operation in the third embodiment of the present invention, and FIG.
The figure shows the relationship between the lens drive amount and the drive speed according to the conventional example and the present invention when backlash removal operation is required.
FIG. 10 is a diagram similarly showing the relationship between time and lens drive speed. PR3...In-camera microcomputer, GTR...
...Gear train, LCNS...Buffer circuit for lens communication, FLNS...Lens, LCNT
...Lens drive control circuit, LPR3 (1)...
...Microcomputer in the lens, ENCZ (2). ENCF (3), ENCP (10)...
・Encoder circuit, 6... Counter, 7...
...Motor drive circuit, 8...Constant speed control circuit,
9...Speed detection circuit.

Claims (1)

[Scope of Claims] (1) A focus lens, a drive means for driving the focus lens, a transmission means for transmitting the driving force of the drive means to the focus lens, and a backlash for removing backlash of the transmission means. In a lens driving device for an optical device, which includes a removing means and a calculating means for calculating the amount of backlash to be removed by the backlash removing means, it is determined whether or not it is necessary to perform backlash removal, and if it is unnecessary. A lens driving device for an optical device, characterized in that an operation control means for prohibiting the operation of the backlash removal means when a determination is made is provided. (2) The operation control means is provided with a determination means for determining whether backlash removal is necessary by comparing the amount of backlash calculated by the calculation means with a value corresponding to a width that can be considered to be in focus. A lens driving device for an optical device according to claim 1, characterized in that: (3) A claim characterized in that the operation control means includes a determination means for determining whether or not backlash removal is necessary by comparing the amount of backlash calculated by the calculation means with the amount of defocus. 1. A lens driving device for an optical device according to 1. (4) A determining means in the operation control means for determining whether backlash removal is necessary by comparing the amount of lens driving required to remove the amount of backlash possessed by the transmission means and the planned driving amount of the focus lens. 2. A lens driving device for an optical device according to claim 1, further comprising: