JPH0233125B2 - JIDOSHOTENKENSHUTSUSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an automatic focus detection device that automatically detects the focus of an imaging optical system.

Conventionally, as an automatic focus detection device for an imaging optical system, as shown in Fig. 1, a light projecting spot image is projected from a light projecting element LT toward an object OB, and the reflected light is divided into two photosensitive areas PA and PB. There is a device that receives the light with a light receiving element PD and detects the distance from the light receiving position to the object OB, or detects the focus adjustment state of the imaging optical system.

That is, in FIG. 1, when the object OB ₁ is at the position S ₁ , the projected spot image projected from the light projecting element LT toward the object OB ₁ hits the object OB ₁ and is reflected. The reflected light spot image is detected by the light receiving element.
Assume that the photosensitive areas PA and PB of the PD are formed at a midpoint position. Then, for the object OB ₂ located at a position S ₂ that is further away from the position S ₁ , the reflected light from the projected spot image is reflected from the photosensitive area of the photodetector PD as the distance between the positions S ₁ and S ₂ increases. It is formed in a state closer to the PA side (in the upward direction of arrow A in FIG. 1). On the other hand, the object at position S ₃ is closer than position S ₁ .
For OB ₃ , the reflected light of the projected spot image is
The larger the distance between S ₁ and position S ₃ , the closer it is to the photosensitive area PB of the photodetector PD (indicated by arrow A in Figure 1).
(downward). Therefore, the above light receiving element
By detecting the position of the reflected light projection spot image formed on the PD, it is possible to know the current distance state of the object. in particular,
By comparing the outputs of the photosensitive areas PA and PB of the photodetector PD, the photosensitive areas PA and PB output an output of a size corresponding to the amount of light received, so the position where the reflected light projection spot image is formed can be determined. Furthermore, as shown in Fig. 1, if the imaging optical system L is equipped to form an image of the object on the predetermined focal plane FM, if the distance state of the object is known as described above, the Since the focus of the imaging optical system can be adjusted by
Move the PD to the larger output of the photosensitive areas PA and PB as shown by arrow A, and the reflected light projection spot image will be the light receiving element.
When the photosensitive areas PA and PB of the PD reach an intermediate position, the imaging optical system L is moved in conjunction with the movement of the light receiving element PD to adjust the focus so that the imaging optical system L is in focus. By moving the lens in the direction of arrow B, that is, in the direction of the optical axis X, the focus of the imaging optical system L can be adjusted. In other words, if the difference in output between the photosensitive areas PA and PB of the photodetector PD is zero, it is in focus, and the output from the photosensitive area PB is higher than the output from the photosensitive area PA.
If the output of the photosensitive area PA is greater than the output of the photosensitive area PB, the front focus is placed (the focus position of the imaging optical system is in front of the planned focal plane), and if the output of the photosensitive area PA is larger than the output of the photosensitive area PB, the rear focus is placed (the focused position of the imaging optical system is in front of the planned focal plane). In the case of front focus, the image forming optical system L is moved toward the planned focal plane FM (to the right of arrow B), and the rear focus is In this case, the imaging optical system can be brought into focus by manually or automatically moving the imaging optical system L in the direction opposite to the intended focal plane FM (to the left of arrow B).

By the way, in the above-mentioned device that determines front focus, focus, and rear focus based on the output state of the light receiving element, the above-mentioned focus detection is generally performed unless the integrated value of the output of the optical element reaches a certain level. It is generally known that this cannot be done with high accuracy. Taking the above device as an example, this means that the light emitting spot image is the light receiving element PD.
At the moment of impact, the outputs of the photosensitive parts PA and PB are both close to the noise level, and it is unclear where on the light receiving element PD the projected light spot image is formed. By integrating the output of the photodetector PD, the signal level increases, and the ratio S/N of the signal level S to the noise level N increases, so the photosensitive element
It is now possible to compare the output levels of PA and PB,
Only in this way can the focal position be detected with high precision. In other words, focus detection, which is performed in accordance with the output of the light receiving element PD as described above, cannot be performed with high accuracy unless the projected light spot image is continuously projected onto the light receiving element PD for a certain period of time and the light reception signal is integrated.

For this reason, conventional automatic focus detection devices of this type generally continue to project the above-mentioned projected spot image for a predetermined period of time, integrate the amount of received light, and then compare the outputs to perform focus detection.

However, the intensity of the light from the projected spot image that enters the light-receiving element varies greatly depending on the distance and reflectance of the object, so if the projection time of the projected spot image is constant as described above, Even though the integrated value of the output of the element has reached a level that allows focus detection, the projected spot image continues to be projected for the predetermined period of time.

Therefore, a large amount of wasted power is consumed, the time required for focus detection becomes longer, and for miniaturization only a small capacity power supply can be incorporated, and furthermore, it is difficult to follow instantaneous shutter movements. This has been a very serious problem in devices such as cameras, where improvements in focus detection speed are required.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an automatic focus detection device that is efficient in power consumption and has a high detection speed.

Its characteristic feature is that a spot light beam is projected onto an object, and an image of the object is created based on the magnitude relationship between the integrated values of the outputs of at least two light receiving elements, which vary depending on the receiving position of the reflected light. in an automatic focus adjustment device for an imaging optical system that forms an image on a predetermined imaging plane, a first detection circuit 107 that detects that the difference between the respective integral values has reached a first level (V _D ); A second detection circuit 109 detects that the sum of the integral values has reached a second level _VH , and when either of the first and second detection circuits first detects the level. , a determination circuit 11 that determines the focus adjustment state of the imaging optical system depending on which of the first and second optical systems is detected.
1, or by further providing a third detection circuit for detecting that the projection time of the spot light has reached a predetermined time, and one of the first, second, and third detection circuits. When first detects the level or the predetermined time,
Depending on which one of the first, second, and third detection circuits detects, whether the imaging optical system is in an out-of-focus state or in a focused state, or the output of each of the light-receiving elements. a discriminating circuit for determining whether or not the spot light is in a low level state; and a circuit for prohibiting projection of the spot light when the first, second, and third detection circuits first detect the level or the predetermined time. By providing this, focus determination can be made quickly, thereby saving power consumption and improving focus detection speed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 schematically shows the overall configuration of an automatic focus detection device (hereinafter referred to as an AF device). 1 in the figure is a photographing lens as an imaging optical system,
The imaging lens group 2, which is involved in the focusing operation, is the imaging surface of the imaging device, and here the imaging surface of the imaging tube is shown, but it may also be the imaging surface of a solid-state imaging device or the film surface. It's okay. Reference numeral 3 denotes a light projecting element for projecting a light beam onto the field of view (generally the area to be measured), and is composed of a laser diode, an infrared light emitting diode, or the like. Reference numeral 4 denotes a light projecting lens which forms a light projected spot image of the light projecting element 3 on a subject 5 (generally an object to be measured). 6 is a light receiving element, which has two photosensitive areas 6A and 6B.
The region 6A is arranged on the light projecting element 3 side, and the region 6B is arranged on the opposite side. The light receiving element 6 is composed of, for example, a two-region PIN photodiode or a charge-coupled device. FL is a visible light cut filter that allows as much light as possible from the infrared light emitting diode 3 to pass through and suppresses external light components. Reference numeral 7 denotes a light-receiving lens, which forms a projected spot image on the subject 5 onto the light-receiving element 6. 8
is a motor for driving the photographing optical system, and is linked to the lens group 1, the light projecting element 3, and the light receiving element 6 via a cam or the like. 9 is an automatic focus detection circuit (hereinafter referred to as AF
motor 7 according to the output of the light receiving element.
is moved to move the lens group 1 to the in-focus position.

Next, to explain the operation of the apparatus shown in Fig. 2, when the subject 5 is at a distance l ₂ from the image plane, Fig. 3 a
Assume that the reflected light of the projected spot image P is received by the two areas 6A and 6B on the optical sensor in an equal amount of light. In this case, in the light receiving element 6, the difference v _{A -} v B between the integral value v _A of the output from the region 6A and the integral value v _B of the output from the region 6B becomes 0. In terms of the optical path, the light emitted from the light projecting element 3 passes through the optical path _b1 , hits the subject, and is diffusely reflected.
Further, it passes through the optical path b ₂ and forms an image on the light receiving element 6 .
Therefore, assume that the lens group 1 is at the in-focus position at this time and the subject 5 has moved to a distance of _l1 . Then, as a matter of course, the focus position of lens group 1 shifts to the rear, resulting in a rear focus state. On the other hand, the light projecting element 3
Assuming that the light receiving element 6 remains in the same position, the optical path hits the subject from _b1 and is diffusely reflected,
The image is formed on the light receiving element 6 through the optical path a′ ₂ , but the third
As shown in FIG. b, the imaging position is largely shifted toward the area 6B, and the above-mentioned v _A - v _B does not become zero.

Therefore, this amount of shift is calculated as the amount of movement of the subject 5, that is, l ₂
The lens group 1 is moved to the in-focus position in accordance with −l ₁ . That is, the AF circuit 9 controls the motor 8 according to the sign (including its magnitude in some cases) of v _A - v _B.
is rotated forward or backward, thereby moving the light emitting element 3, light receiving element 6, and lens group 1 in conjunction with a cam, etc., so that v _A - v _B = 0, that is, the light emitting spot image is located in the area on the light receiving element 6. When it comes to the middle position between 6A and 6B, l ₁
An image of a subject at a distance of 2 is formed sharply on an imaging plane 2. As a result, the light projecting element 3 moves to the position 3', the light receiving element 6 moves the boundary line between the areas 5A and 5B to the position 6', and the lens group 1 moves to the position 1'. In this case, the projection optical path b ₁ and the reflected optical path are indicated by a ₂ ′. On the other hand, when the subject 5 moves to the position _l3 , the lens group 1 etc. move in the opposite direction to the above and perform a focusing operation so that v _A - v _B =0. In this case, the projection optical path is c ₁ ,
The reflected optical path is denoted by _c2 .

4 to 7 show other embodiments of an automatic focus detection device that performs distance measurement based on the same principle as the device shown in FIG. It's different. Hereinafter, the same members as those in the apparatus shown in FIG. 2 will be given the same numbers and will be briefly described.

Figure 4 shows a so-called half-light system in which a light spot image is projected from a light projecting element through a photographing lens, and the light is received by a light receiving element provided outside the camera.
It is a type of TTL distance measurement. Reference numeral 10 denotes a half mirror having a reflective surface 10a configured as a cold mirror, and is disposed between the image forming surface 2 and the lens group 1 of the photographing lens, which moves particularly for focus adjustment. 4' is a light projecting lens, and 3 is a light projecting element. It is desirable that the light projecting element 3 is arranged at a position that is optically conjugate with the imaging plane 2. The movement of the photographic lens 1 is performed in mechanical conjunction with the light receiving element 6.

FIG. 5 shows a so-called TTL distance measuring type automatic focus detection device in which light is emitted from a light emitting element and light is received by a light receiving element through a photographing lens. 10' is a half mirror placed at the same position as 10 in FIG. The projected spot image is configured to pass near the outer periphery of the pupil of the photographing lens 1. 7' is a light-receiving lens; 6 is a light-receiving element arranged at a position optically conjugate with the imaging plane 2 of the photographic lens 1; its light flux is near the outer periphery of the pupil of the photographic lens 1; It is designed to pass through isolated locations. Note that the light projecting element 3 and the light receiving element 6 are fixedly installed, and are not mechanically interlocked with the photographing lens.

FIG. 6 is a modification of FIG. 5, in which the projected light beam is aligned with the photographing optical axis.

Figure 7 shows an automatic focus detection device that uses the same light projection system as in Figure 4 and uses the image sensor 13 provided on the focal plane as a light receiving element for focus adjustment and imaging. It is. and image sensor 1
The image signal received by the sensor 3 is divided by the distribution circuit 11 to the AF circuit 7 and the imaging circuit 12.

FIG. 8 shows the photosensitive surface of the image sensor 13 of the device shown in FIG. send to Further, in the case of the one shown in FIG. 7, it is necessary to devise a method to allow infrared light to pass through the image pickup element 13 during distance measurement, and to remove the infrared light during image capture.

By the way, among the above embodiments, in the type shown in FIG. 2, the light projecting lens 4 and the light receiving lens 7 are located outside the photographing lens 1, so it is possible to increase the size of the projecting and light receiving lenses 4 and 7. This is advantageous in terms of reach, but on the other hand, it has the disadvantage that the whole system cannot be organized compactly. On the other hand, the type shown in Figure 4 has the opposite advantages to the type shown in Figure 2.
Has disadvantages. Furthermore, since there is no need for mechanical interlocking between the imaging lens 1 and the projection/reception system, which requires precision, there is also the advantage that the structure is simple.
The type shown in FIG. 4 has properties intermediate between those shown in FIGS. 2 and 5.

The type shown in Figure 5 is different from that shown in Figure 4.
Although the baseline length of the light emitting/receiving system is shortened, which is disadvantageous in terms of distance measurement accuracy, it has the advantage, like the one shown in FIG. 3, that the emitted light beam remains at the center of the viewfinder even when out of focus. Incidentally, in all of the above-mentioned types, the light projected spot image formed on the subject 5 by the light projecting element 3 is formed on the optical axis of the photographing lens when in focus. That is, in any of the above devices, the distance measurement zone is located at the center of the viewfinder, and the device becomes an automatic focus detection device without parallax.

In addition, in the device shown in FIG. 7, the light-receiving aperture of the light-receiving element 13 is approximately equal to the F number of the photographing lens, so compared to other types of devices, the area of the light-receiving aperture can generally be made larger, and the distance of the object can be improved. It is advantageous. Further, in the device shown in FIG. 6, the signal from the image sensor 13 is sent to the AF circuit 9 and the image sensor 12
However, since it is practical to distribute this time-divisionally, this type of system is suitable for systems such as still video cameras that complete distance measurement prior to shooting.

Next, the configuration of the electric circuit in the above device is explained in the ninth section.
This will be explained based on the diagram. As described above, the reflected light projected spot image received by each region 6A, 6B of the light receiving element 6 is transmitted to the amplifier circuit 10 as photoelectrically converted optical information.
1a and 101b and is sufficiently amplified. At this time, the amplifiers 101a and 101b have sufficient amplification for the modulation frequency of the infrared light that becomes the projected spot image, and have a sufficient amplification for the frequency of modulated light from unnecessary sunlight or commercial power. It is desirable to use an amplifier circuit with frequency characteristics that are as suppressed as possible. The output of this amplifier is applied to synchronous detection circuits 102a and 102b for synchronous detection. At this time, the synchronization signal has the same frequency as the light emission drive signal of the light projecting element 3, and maintains a constant phase relationship. The output of this synchronous detection circuit is integrated by integrating circuits 103a and 103b, and increases moment by moment at an increasing rate proportional to the signal intensity of the reflected light projection spot image. The integrated voltages v _A and v _B obtained independently from the integrating circuits 103a and 103b through the above signal processing are processed and determined by the arithmetic circuit described below and converted into several bits of digital information.

That is, the integrated voltages v _A and v _B are
gives a difference signal v _A − v _B , and on the other hand, the adder 10
5, the sum signal becomes v _A + v _B. The difference signal v _A −v _B is applied to an absolute value circuit 106 to obtain |v _A −v _B |. This value |v _A −v _B | is compared with a comparison value V _D in a comparator 107 serving as a comparing means, and the magnitude relationship thereof is output. On the other hand, the sum signal v _A +v _B is compared with comparison values v _L and v _H , respectively, in comparators 108 and 109 as level detecting means, and the magnitude relationship of each is outputted. Further, in the comparator 110, the integrated voltages _vA and _vB are directly compared in terms of magnitude.
The four digital information obtained from the above, namely:
The outputs of the comparators 107, 108, 109, and 110 are applied to a sequence control circuit 111 as a determining means, and the operation of the entire system is determined.

112 is a light emission drive circuit, and a control circuit 111
A current is supplied to the light projecting element 3 in synchronization with a synchronization signal from the light projecting element 2 to control the light emission of the light projecting element 2.

113 is a motor drive circuit, and the control circuit 11
The photographing optical system drive motor 8 is driven by the signal from 1.
control the direction and speed of rotation.

FIG. 10 shows a further embodiment of the circuit configuration shown in FIG. 9.

FIG. 10 shows the part (A) of the circuit in FIG. 9, in which low-noise operational amplifiers 201a and 201b are used in the first stage of amplifiers 101a and 101b, and high-pass characteristics are achieved by setting the feedback circuits 202a and 202b. It is made to have. In the energy of the infrared light actually projected from the light projecting element 3, the external light component can have a considerably large value compared to the energy returned to the light receiving element 6. The visible light cut filter FL and this circuit have the effect of relatively suppressing external light components, and depending on the settings, can be used for most subject conditions. Furthermore, capacitor 203
Direct current components such as sunlight are almost completely cut out by a and 203b. AC amplifiers 204a and 204b sufficiently amplify components near the modulation frequency and then supply the signals to the next-stage synchronous detection circuit.

Synchronous detection circuits 102a and 102b shown in FIG.
is composed of inverters 205a, 205b and analog switches 206a, 206b and 207a, 207b.
This is realized by switching 6b, 207a, and 207b using a synchronizing signal SYNC, and alternately selecting a non-inverted signal and an inverted signal.

Further, as another embodiment, there is a method of calculating the product of the input signal and the alternating current component of the synchronization signal SYNC using a four-phenomenal analog multiplier (not shown).

The synchronously detected signal becomes a direct current (pulsating current) component and is supplied to the next stage integration circuits 103a and 103b. These integrating circuits 103a, 103b include operational amplifiers 208a, 208b, resistors 209a, 20
9b, and capacitors 210a and 210b. Then, a current proportional to the synchronous detection output voltage flows from the synchronous detection circuits 102a and 102b to the capacitors 210a and 210b through the resistors 209a and 209b, respectively, and is accumulated.
The integrated voltage becomes operational amplifiers 208a and 208b.
is output from. These voltages are v _A and v _B , respectively. In addition, 211a and 211b are capacitors 210
This is an analog switch for initializing the charges accumulated in capacitors 210a and 210b.
The charges accumulated in 10b are cleared by the CLR signal from control circuit 111 in preparation for the next accumulation.

FIG. 11 shows part (B) of the circuit of FIG. 9 which creates |v _A −v _B | from the integrated voltages v _A and v _B and compares this with a comparison voltage v _D. Integrating circuit 103a,
The integrated voltages v _A and v _B outputted from 103b are applied to the operational amplifier 212 and the resistors 213 to 2 with the same resistance value R.
16 to obtain -v _A +v _B. This value is added to the absolute value circuit 106 at the next stage. The absolute value circuit 106 includes an operational amplifier 217, diodes 218, 219,
It is composed of resistors 220 to 222 with a resistance value of 2R and a resistor 223 with a resistance value of R. Operational amplifier 2
17, diodes 218, 219, resistor 220,
Due to the configuration of the diode 221, the cathode of the diode 219 has a high impedance when the input is negative, and has a potential -1 times the input voltage when the input is positive. As a result, a voltage of −0.5|v _A −v _B | is applied to the negative input of comparator 224. By applying a voltage of −0.5v _D to this positive input, |v _A −v _B | and v _D can be compared. Let this comparison value be DD.

Moreover, FIG. 12 shows the (C) part of the circuit of FIG. 9, where v _A and v _B are added by the resistors 225 and 226 of resistance value R, and 0.5 (v _A + v _B ) is added to the comparator 22.
7,228 positive inputs. 0.5v _L and 0.5v _H are applied to the negative inputs of each comparator, and a comparison of (v _A + v _B ): v _L and (v _A + v _B ): v _H is performed, and the comparison values LL, Output HH.

Further, FIG. 13 shows the circuit (D) portion of FIG. 9, where v _A and v _B are directly compared by a comparator 229, and a comparison value AB is output.

FIG. 13 shows another embodiment for obtaining the comparison value DD from v _A and v _B. v _A and v _B are comparator 23
0,231 positive inputs. It is also applied to the negative input via resistors 232 and 233 having a resistance value of R. In addition, a constant current source 23 is connected to the negative input.
4,235 is also connected, and as a result, voltages of v _B +iR and v _A +iR are applied to the negative input. However, i
is the current value of 234,235, comparator 230
The outputs of 231 and 231 are added to an OR circuit 236,
Output DD is obtained. The output DD becomes true logic when v _A − v _B > iR = v _D or v _B − v _A > iR = v _D , and | v _A − v _B
|＞v Represents the logic of _D.

FIG. 15 shows a part of the sequence control circuit 111 implemented in hardware. The clock C determines the minimum cycle of the sequential control circuit 111, and controls the light emission modulation of the light projecting element 4 and the synchronous detection circuits 102a, 102.
This is the source of the synchronization signal SYNC for b. 236 is an n counter, and the period of this output Cn is the period of distance measurement,
and determine the maximum integration time. Flip-flops 237 and 238 are set by signals DD and HH, respectively, and reset every ranging period by signal Cn. The outputs DDQ and HHQ of the flip-flops 237 and 238 are integral abort signals, which are sent to the flip-flop 2 via an OR circuit 239.
40 and is held at the period of the signal Cu. The inverted output of flip-flop 240 is an infinite signal
Becomes FAR. Signals FAR and DDQ are OR circuit 241
The flip-flop 242 is set via the motor to output the motor rotation signal MO. This flip-flop 242 is also reset by the focus signal HHQ signal, inhibits the output of the motor rotation signal MO during focusing, and stops the motor 8. The signal AB is updated in the flip-flop 243 by a signal DDQ representing out-of-focus to become ABQ. Here, when the front pin is present, that is, v _A > v _B , the logic is true. The signal ABQ and the signal FAR pass through an OR circuit 244 and become a signal FN representing the rotational direction of the motor. Final motor drive signal FF (towards infinity),
NN (towards the nearest direction) is the output of the AND circuit 245 which inputs the signal FN and the signal MO, or the signal FN is NOT
The selection is made by the output of an AND circuit 247 which receives the output obtained through the circuit 246 and the signal MO.

The synchronization signal SYNC is output from the OR circuit 239 when the signal DDQ and the signal HHQ are both pseudo-logic.
By being input to the AND circuit 249 via the circuit 248, the signal is input to the AND circuit 249.
It is output in synchronization with the output CLK of clock C.
Integral initialization signal output from OR circuit 250
CLR is the OR circuit 2 input to the OR circuit 250
After determining the end of the integration based on the output of 39 and the signal _Co , the logic remains true until the start of the next integration.

FIG. 16 shows waveforms observed as each signal in FIG. 15 when the state changes from front focus to back focus to focus to infinity.

At the front pin, DD rises first, and AB is at a high level at this time. At the rear pin, DD rises first, but AB is at a low level. HH rises when in focus. At infinite time, the maximum integration time is reached before any rise occurs.

FIG. 17 shows a part of the apparatus in which a microcomputer is used as the sequence control circuit 111 and the apparatus is controlled by software. In this figure, the light emitting drive circuit 112 of the light projecting element 3
An example of the motor drive circuit 113 is also shown. 251 is a microcomputer (for example, it has an internal structure as shown in FIG. 18),
The input terminals are connected to the aforementioned signals DD, AB, LL, HH.
is input, and each of the above-mentioned signals is also output from the output terminal.
SYNC, CLR, FF, and NN are output. Also,
It is also easy to add a signal such as LOW to control the rotational speed of the motor.

The current flowing through the light emitting element 2 is transmitted through the transistor 25.
2,253 by the signal SYNC.

The current flowing to the motor 8 is the transistor 254~
257 by the signal FF and signal NN, and flows in the forward or reverse direction.
Transistors 258, 259, diode 260
The circuit configuration is a voltage control circuit, and the voltage applied to the motor is switched between two levels depending on the LOW signal. 261 and 262 are a close-range switch and an infinity switch, respectively, and the photographing optical system is at the close-range end,
It closes when it hits the infinite end, preventing it from driving beyond its limit.

FIG. 19 shows electrical signal waveforms at various parts of the circuit shown in FIG. The synchronization signal SYNC is the synchronization detection circuit 102
a, 102b, but is also used to drive the light projecting element 3, and the light emission output IRED is obtained.
The electrical signals obtained from the light-receiving elements 6a and 6b are obtained by superimposing the reflected light component of the projected infrared light and the external light component of the sun or artificial light, and have a waveform like the signal SPC. This signal is passed through an amplifier 10 with high-pass characteristics.
The signal obtained by applying 1a and 101b is the signal Amp
It is. When the CLR signal is released almost simultaneously with the start of light emission, the synchronous detection circuits 102a and 102
The output of b is integrated, and the integration circuits 103a, 103
An integral waveform like the signal Int appears at the output of b.
This integral waveform increase rate is proportional to the amount of emitted light component of the emitted infrared light. Even for extremely weak inputs, a large SN ratio can be obtained by integrating a sufficient number of times (time).

Next, the operation of this apparatus will be explained based on FIG. 9 and in accordance with the flowchart numbers shown in FIGS. 20 to 24. Here, it is assumed that a microcomputer (hereinafter referred to as microcomputer) 251 is used as the control circuit 111.

When an AF operation switch (not shown) is closed, the control circuit 111 starts operating.

First, it is determined whether the SENS input terminal of the control circuit 111 is at a high level.
When the SENS input terminal is at a high level, the system operates in the adjustment mode shown in Figure 23, and distance measurement is not performed. In the adjustment mode, the ON-OFF of the infrared light emitting diode 3 and the output of the light receiving element 6 are integrated for _T0 time, and the offset adjustment amplifier circuit 101a of the IC,
101b, synchronous detection circuits 102a, 102b,
The positional relationship of the infrared light emitting diode 3 or the light projecting lens 4, the light receiving element 6, the light receiving lens 7, etc. is adjusted by adjusting the integrating circuits 103a and 103b or by an adjustment mechanism (not shown). Therefore, the SENS input terminal of the control circuit 111 is normally at a low level, and when the AF operation switch is closed,
This device first operates in the following normal ranging mode.

When entering the normal distance measurement mode, first the ∞ flag as a prohibition means is reset. Furthermore, this ∞
The contents of the flag will be described later. Also, this ∞
Microcomputer 251 is used as memory for flags.
Assume that memory M(1) in the RAM area is used.

After this, the control circuit 111 starts the distance measuring operation. That is, the control circuit 111 first controls the light emission drive circuit 112 and the synchronous detection circuits 102a and 10.
2b is driven in synchronization with the synchronizing signal SYNC, and the clear state of the integrating circuits 103a and 103b is released. As a result, a spot image of infrared light is projected from the light projecting element 3 toward the object field in synchronization with the synchronizing signal SYNC, and the reflected light is detected by the light receiving element 6. In the light receiving element 6, an electric signal corresponding to the amount of light received is output from the two light sensitive areas 6A and 6B according to the light receiving position of the reflected light projection spot image, and this is outputted to the amplifiers 101a and 101.
b amplified by the synchronous detection circuit 102a,
102b performs synchronous detection. The optical information obtained in this way is then sent to an integrating circuit 103.
The voltages a and 103b are sequentially integrated, and the outputs thereof become integrated voltages v _A and v _B. As described above, these integrated voltages v _A and v _B are processed into four pieces of digital information shown below and input to the control circuit 111 . That is, the subtracter 104 generates a difference signal v _A - v _B , which is added to the absolute value circuit 106, and the comparator 107 compares the magnitude relationship between the absolute value |v _A - v _B | and the comparison value v _D. Digital output from DD adder 105 sum signal v _A + v _B and comparison value
Digital output from comparator 108 that compares the magnitude relationship with v _L , LL sum signal v _A + v _B and comparison value from adder 105
Digital output from comparator 109 that compares the magnitude relationship with v _H (v _H > v _L ), HH Comparator 1 that compares the magnitude relationship between signals v _A and v _B
On the other hand, in the control circuit 111, the digital output from the integrating circuits 103a, 1 is detected by the time detection means in the microcomputer.
The integration time of the signal at 03b, that is, the projection time of the light projecting element is measured, and if this is t, the magnitude relationship with the maximum integration time T ₀ (for example, 28 msec) is compared. Therefore, when these pieces of information are given, the control circuit 111 changes the signal to |v _A −v _B |≧
It is determined whether v _D or v _A + v _B ≧v _H or t≧T ₀ . When any one of these three conditions is met, the control circuit 1
11, it is determined that distance measurement has been completed. Fig. 25 shows the state of the reflected light projected spot image P and the integral signals v _A and v _B when in focus.As shown in Fig. 25, in the focused state, the reflected light projected spot image P is Since the photosensitive areas 6A and 6B of the light receiving element 6 are formed at a substantially intermediate position between the photosensitive areas 6A and 6B of the light receiving element 6, outputs of substantially the same large value can be obtained from the photosensitive areas 6A and 6B of the light receiving element 6. Therefore, the values of the integral signals v _A and v _B rapidly increase while they are both substantially equal, as shown in FIG. Therefore, as shown in FIG. 25, the signal v _A
+v _B also increases rapidly with time t, while the signal |v _A −v _B | hardly increases as shown in FIG. Therefore, for the comparison values v _H , v _D and the maximum integration time T ₀ , if v _A +v _B ≧v _H , |v _A −v _B |<v _D and t<T ₀ , the state is in focus. It is determined that On the other hand, Fig. 26 shows the reflected light projected spot image and the state of the integral signals v _A and v _B when out of focus. When the lens group 1 is in the front focus or rear focused state, the reflected light projected spot image P is shown. As shown in FIG. 26, since the signal is biased toward either the photosensitive area 6A or 6B of the photodetector 6, the output signal from the photosensitive area 6A or 6B of the photodetector 6 generally has a larger value. Therefore, as shown in FIG. 26, one of the integral signals v _A and v _B increases rapidly with time t, but the other integral value hardly increases. Therefore, as shown in Figure 26, the signal
Until v _A + v _B becomes larger than the comparison value v _H ,
Until the integration time t reaches the maximum integration time T ₀ , the signal |v _A −v _B | becomes |v _A −v _B |≧v _D. Therefore, |v _A −v _B |≧v _D is detected, and v _A +v _B <v _H and t
If <T ₀ , it is determined that the front pin or rear pin state is present. FIG. 27 shows the state of the reflected light spot image P and the integral signals v _A and v _B when the subject 5 is far away or the reflectance of the subject 5 is extremely low. In this case, the reflected light spot image P is not formed on the light receiving element 6, or even if it is formed, the amount of light received is extremely weak. Therefore, the output signals of the photosensitive areas 6A and 6B of the light receiving element 6 both have small values, and the second
As shown in FIG. 7, both the integral signals v _A and v _B do not increase much. Therefore, even if the integration time t reaches the maximum integration time T ₀ , the signals v _A +v _B and |v _A −v _B | are both v _A +v _B ≧v _H |v _A −v _B as shown in FIG. ｜
≧v _D does not hold. Therefore, t≧T ₀ , v _A +v _B <
If v _H | v _A − v _B | < v _D , it is determined that the subject 5 is far away or in a state where distance measurement is difficult.

As above, v _A +v _B ≧v _H or |v _A −v _B |≧v _D
Alternatively, by setting t≧T ₀ as the determination condition for distance measurement completion, when the values of the integral signals v _A and v _B reach a level that allows distance measurement, automatic focus detection operation can be started immediately. Wasteful consumption of charge is prevented. In particular, as will be described later, in this device, if the distance measurement is completed within the maximum integration time T ₀ , in order to keep the time of one distance measurement cycle constant, the microcontroller internally processes the distance measurement until the maximum integration time T ₀ is reached. Since the time is counted and the next distance measurement cycle is started to measure the distance again after T ₀ time has elapsed, there is no wasted charge consumption from the completion of distance measurement until the elapse of T ₀ time, which is a power saving feature. is extremely effective.

FIG. 24 specifically shows the contents as a subroutine. A step-by-step explanation will be given below.

B. The light emitting element 3 and other distance measuring circuits start operating as described above.

○B Release the clear state of the integrating circuits 103a and 103b.

○C The light emitting element 3 emits light.

○D Thereafter, the synchronization signal SYNC is stopped to stop the light emission drive circuit 112, and therefore the light emission of the light projecting element 3 is stopped. At the same time, the driving of the synchronous detection circuits 102a and 102b is also stopped.

○E It is determined whether distance measurement is completed according to the distance measurement completion determination conditions described above.

○F When the above conditions for completion of distance measurement are not met, the light emitting element 3 emits light again and distance measurement is repeated.

○G When the conditions for distance measurement completion are met, the signal is
DD, AB, LL, HH (i.e. comparators 107, 1
08, 109, 110 output) is the microcontroller's output
It is stored in memory M(O) in the RAM area.
Thereafter, by stopping the synchronization signal SYNC, the light emitting drive circuit 112 is stopped, and therefore the light emitting element 3 stops emitting light. At the same time, the driving of the synchronous detection circuits 102a and 102b is also stopped.

○chi Then, by setting the CLEAR output of the control circuit 111 to a high level, the integration circuit 103
a and 103b are set in a clear state to prepare for the next distance measurement operation. After performing the above series of controls, the 4-bit data stored in the memory M(O) is used to perform an automatic focus detection operation and move to another distance measurement mode to be described later. The subroutine shown in FIG. 24 is also used in other distance measurement modes to be described later by changing the condition for determining completion of distance measurement in ◯◯.

Returning to FIG. 20 again, when v _A +v _B ≧v _H is detected, as described above, it is determined that the object is in focus.

When the focus is determined, a stop signal (FF=NN=0) is supplied from the control circuit 111 to the motor drive circuit 113 to stop the motor 8.

After the integration time t reaches the maximum integration time T ₀ , a transition is made to a normal focus distance measurement mode suitable for normal focusing, which will be described later, and distance measurement is performed again.

On the other hand, when v _A + v _B ≧ v _H , it means that the object is out of focus or the values of the integral signals v _A and v _B are small, and it is determined here whether this is the case. ｜v _A −v _B ｜
When ≧v _D is not, distance measurement is completed at t≧T ₀ , so as mentioned above, in this case, the integral signal v _A ,
Since the level of v _B is low, distance measurement suitable for the low level integrated signals v _A and v _B is performed. Transition to low level distance measurement mode, which will be described later.

When v _A − v _B |≧v _D , it is determined that the lens group 1 is in an out-of-focus state, and then a determination is made as to whether the focus is from the front or the rear. When v _A > v _B , it is determined that the rear focus is present, and that it is necessary to drive the motor 8 to move the lens group 1 to the nearest side.

Next, the speed at which the motor 8 should be driven is determined. In this embodiment, the motor speed is controlled in two steps, and by switching the speed to a low speed when approaching the in-focus state from the out-of-focus state, the lens group 1 can overrun the in-focus position. It is designed to prevent this and stop smoothly. Note that this motor speed may be switched to any number of speeds as required. Here, the level of the comparison value v _L is used as a determination criterion to determine whether the focus is close to the in-focus state or whether it is significantly out of focus. When out of focus, when distance measurement is completed, that is, |v _A −v _B |=
At the point when v _D is reached, the signal v _A + v _B becomes v _A + v _B ≧
In principle, when v _L , the speed is low, and when v _A + v _B < v _L , the speed is high. This situation is shown in FIGS. 26 and 28, with FIG. 26 showing the high speed and FIG. 28 showing the low speed. As can be seen from FIGS. 26 and 28, the closer the focused state is, the closer the reflected light projection spot image P approaches the intermediate position between the photosensitive areas 6A and 6B of the light receiving element 6, so the integral signals v _A and v _B The difference in level will become smaller. Therefore, the closer the lens group 1 is to the in-focus position, the longer the time t until |v _A −v _B |≧v _D becomes true, and v _A +v _B increases by that length.
becomes larger. Therefore, the degree of out-of-focus can be determined by the magnitude of v _A + v _B.

FIG. 29 shows the relationship between the speed control of the motor 8 and the position of the reflected light projection spot image P on the light receiving element 6 as described above. As a result, the reflected light projection image P moves from position P ₁ (rear focus) to P ₂ (coupling focus).
The magnitude of the amount of light received by the photosensitive areas 6A and 6B when moving to the position _P3 (front focus) can be seen. The portion L in FIG. 29 is within the low speed range and is expressed as |v _A −v _B |/v _A +v _B ≦k ₀ . The value of k ₀ is set to an appropriate value depending on conditions such as the speed of the motor and the inertia of the system. As a result, |v _A −v _B |/v _A +v _B ≦k ₀ v _A +v _B ≧|v _A −v _B |/k ₀ =v _L.

Here, in this device, it is determined that distance measurement is complete when out of focus when |v _A − v _B | = v _D = constant voltage, and it is set as v _D /k ₀ = v _L ′. Speed control is performed by In the embodiment of this application, v _L = v _L ′,
Other values may be set.

Now, we return to the flowchart of FIG. 20 again. After being out of focus and determined to be in focus v _A +v _B ≧v _L
Make a judgment.

When v _A + v _B ≧ v _L , the control circuit 111 outputs a signal to drive the motor 8 at low speed as described above, and the lens group 1 is controlled to the close side.

After the time elapses until t=T ₀ is reached, the process returns and distance measurement is performed again in the normal distance measurement mode.

On the other hand, in Fig. 20, when v _A + v _B < v _L , the motor 8 should be rotated at high speed in principle as described above, but it should also be driven to the close side at this high speed. It is determined whether the determination has been made n ₂ times in succession while the normal distance measurement mode is repeated n ₂ times. n If it is less than ₂ times, move to
The motor 8 is driven at low speed to the close side.

n When it is determined that the motor 8 should be driven toward the closest side at high speed _two or more times in succession, the motor 8 is thereafter driven toward the closest side at high speed. On the other hand, if the decision to drive toward the closest position at high speed is not made n ₂ times in a row, for example, if a judgment such as focusing is made in the middle, the decision to drive toward the close range at high speed is made again n _times in a row. The motor 8 will not reach high speed until the

As mentioned above, the reason for controlling the speed of the motor 8 is to make sure that the motor 8 moves at a low speed when starting, which improves the feel at the time of starting and improves the integral signal.
Due to the noise added to v _A and v _B , lens group 1
This is to reduce the occurrence of hunting and other movements.

The operations of ~ are exactly the same as ~ except that the driving direction of the motor 8 is reversed, so the explanation will be omitted.

Next, the normal focus distance measurement mode will be explained.

It is determined that the camera is in focus,
When the integration time t reaches the maximum integration time T ₀ , distance measurement is performed again in the normal focus distance measurement mode suitable for distance measurement from a focused state. This is because, even after focusing, the distance of the subject may change moment by moment, so distance measurement is re-measured at fixed intervals (maximum integration time T ₀ in this case) to ensure that lens group 1 is in focus. This is because it is necessary to check whether the In the normal focus distance measurement mode, the condition for determining the focus state is v _A in the normal distance measurement mode.
It changes from +v _B ≧v _H to v _A +v _B ≧v _L (v _L < v _H ).
In this way, the condition for determining distance measurement completion is set from v _A + v _B ≧ v _H.
The reason for changing v _A + v _B ≧ v _L is to widen the range that is determined to be in focus. In other words, the so-called dead zone, which is the range in which it cannot be determined to be out of focus, is widened, and the lens group 1 is made difficult to move from the position where it was previously determined to be in focus. For example, if you set v _L = 1/2v _H, as shown in Figure 30, the comparison value will actually be
It is possible to obtain the same effect as when v _D is doubled, and it becomes difficult to judge |v _A −v _B |≧v _D.
It is difficult to get out of focus. Therefore, it is possible to reduce malfunctions caused by noise superimposed on the integral signals v _A and v _B. Also, by lowering the comparison value, the integration time, that is, the time during which the light emitting element 3 emits light, can be shortened, and as in this device,
Needless to say, it is advantageous in terms of power consumption when one distance measurement cycle takes a certain period of time.

Note that other conditions for determining completion of distance measurement are the same as in the normal distance measurement mode, and subsequent operations proceed in the same manner as in the normal distance measurement mode. In other words, start distance measurement, |v _A −v _B |≧v _D or v _A +v _B ≧
When one of the three conditions v _L or t≧T ₀ is satisfied, the control circuit 111 completes distance measurement, and the comparison signals DD, AB, LL, HH at that time are stored again in the memory M(O). do.

Here, based on the data stored in memory M(O), whether |v _A −v _B |≧v _D ,
In other words, it is determined whether or not the object is out of focus. ｜v _A −
If it is determined that v _B |≧v _D , it means that the focus is out of focus, and distance measurement is performed again in the normal distance measurement mode.

When ｜v _A −v _B ｜≧v _D is not the case, a sufficient signal cannot be obtained because the object is in focus or the object is far away or the reflectance of the object is low, and v _A + v _B ≧ v _L. The level state of the integral signals v _A and v _B is determined depending on whether the focus is on or not, and whether or not focus is achieved is determined based on that state. When v _A + v _B ≧ v _L , distance measurement is completed at t≧T ₀ , and since the integral signals v _A and v _B are extremely low, the object is far away or the reflectance of the object is low. It determines that this is the case, moves to low level distance measurement mode, and performs distance measurement again.

On the other hand, when v _A +v _B ≧v _L , it is determined that the camera is in focus, and then counts up to the maximum integration time T ₀ in the same way as described below.

〓〓 Next, it is determined how many times the normal focus and distance measurement mode has been repeated. When the number of repetitions is n<n ₀ , the mode returns to the normal focus distance measurement mode, and n=n _0.
Distance measurement is performed in the normal focus distance measurement mode until reaching or or when switching to another distance measurement mode. The normal focus distance measurement mode is repeated n ₀ times, and when n = n ₀ , it returns to the normal distance measurement mode again, and the next distance measurement is performed in the normal distance measurement mode, that is, in the regular dead zone. .

As described above, by returning the dead zone to its normal state every _n0th time, it is possible to prevent a decrease in distance measurement accuracy. As mentioned above, by widening the dead zone, stability is increased, but as a reaction, the accuracy of distance measurement is reduced. Therefore, by returning to the normal distance measurement mode every _n0th time, in-focus/out-of-focus is determined using the regular dead zone, thereby compensating for the decrease in distance measurement accuracy. Therefore, by doing this, it is possible to achieve both stability during focusing and distance measurement accuracy. Note that n ₀ and v _L need to be set to appropriate values for the above purpose.

Next, the operation in the low level ranging mode will be described based on FIG.

As mentioned above, in the normal ranging mode or normal focused ranging mode, both the integral signals v _A and v _B are determined to be at a low level, or in the ∞ time ranging mode described later, the integral signal v When it is determined that the levels of _A and v _B have risen to a certain level and distance measurement is possible, distance measurement is performed in the low level ranging mode, which is suitable for distance measurement when the level of the integral signals v _A and v _B is low. will be carried out. In the low level ranging mode, when the integral signals v _A and v _B are obtained in the same manner as in the normal ranging mode, completion of ranging is determined based on v _A +v _B ≧v _H or t≧T ₀ . Note that v _A −v _B ≧v _H is excluded here as a condition for determining completion of distance measurement, unlike in the normal distance measurement mode. This is because in the low level distance measurement mode, the level of the signal detected on the light receiving element 6 is low because the subject 5 is far away or the reflectance of the subject 5 is low. The S/N of signals v _A and v _B is not very good,
For example, the magnitude relationship between the levels of the integral signals v _A and v _B may be opposite to the original values, and this is to prevent erroneous distance measurement from occurring. In other words, if signals in the near direction and infinity direction are repeatedly output, if these are detected as they are, out-of-focus signals in different directions will be output alternately, leading to unstable operation. . FIG. 31 is an example of such an integral signal with a poor S/N ratio. As shown in FIG. 31, the v _A signal and the v _B signal are alternately exchanged, so the ( ), if |v _A −v _B |≧v _D and v _B > v _A , it is determined that the front pin state is present, and the control circuit 111 sends a control signal to drive the motor 8 in an infinite direction. Output. Also, by chance (probabilistically)
At point (), v _B > v _A , but if |v _A −v _B | < v _D as shown in ()′, then ()
The distance measurement is not determined at the point (), and the distance measurement is not determined at the point ().
A determination will be made that v _A > v _B , |v _A −v _B | > v _D . This results in outputting an out-of-focus signal to the motor 8 in a direction completely opposite to that in the above case. In order to reduce the instability mentioned above as much as possible, in low-level distance measurement mode, |v _A −v _B |≧v _D is not used as the condition for determining distance measurement completion, and v _A +v _B ≧v _H is not determined. After continuing the integration until t=T ₀ |
It is decided that v _A − v _B | ≧ v _D. By switching between multiple modes in this way,
It is possible to achieve both the advantages of the normal ranging mode (power saving, etc.) and the stability of the low level ranging mode.

〓〓 Returning again to the flowchart of the low-level distance measurement mode in FIG. 21, when the distance measurement is completed, it is then determined whether the distance measurement has been completed based on v _A +v _B ≧v _H. When v _A + v _B ≧ v _H , it means that the signals v _A and v _B are sufficiently large, and it is determined that there is no longer a need to perform distance measurement in low level distance measurement mode, and the mode is switched to normal distance measurement mode. return. Figure 32 shows the signal when returning from low level mode to normal ranging mode.
The states of v _A , signal v _B , signal v _A +v _B , and signal |v _A −v _B | are shown. As shown in the figure, even if |v _A −v _B |>v _D , distance measurement is not completed and continues. As shown in the figure, when the conditions t<T ₀ and v _A +v _B ≧v _H are satisfied, distance measurement is completed and the mode returns to the normal distance measurement mode.

〓〓 If v _A + v _B ≧ v _H , distance measurement is completed at t =
This means that it was carried out under the condition of T ₀ . Subsequently, the level of v _A + v _B is determined, and it is determined whether it should be determined that it is infinite or whether it is a range measurable area within a finite distance. When v _A + v _B ≧ v _L (v _L < v _H ), the levels of the integral signals v _A and v _B are extremely low, so it is determined that the object is in an infinite state, and the subsequent distance measurement will be explained later. This is done in infinite ranging mode. FIG. 33 is a diagram showing the states of the signals v _A , v _B and the signal v _A +v _B when entering the infinite distance measurement mode. As a result of distance measurement up to t=T ₀ , v _A + v _B < v _L , since the values of the integral signals v _A and v _B are both extremely low, it is determined that the object is in an infinite state. Also, in that case |v _A −
The value of v _B | is |v _A −v _B |≧v _D even if |v _A −v _B
Even if |<v _D , this fact is ignored.
Note that even when the object is not far away and the reflectance of the object is low, the light-receiving element 6 cannot receive sufficient reflected light, so this situation also occurs in this case. In systems that measure distance, it is very difficult to distinguish whether an object is far away or has low reflectance.
Therefore, assuming that the former is the case, the control circuit 111 sends a control signal (FF=1, NN=0) to the motor drive circuit 113 in order to drive the motor 8 in the infinite direction.
Output to. Naturally, if another distance measurement signal is obtained before the photographic lens 1 reaches the ∞ end, a stop or reversal signal is applied to the motor drive circuit 113 at that point.

〓〓 When v _A + v _B ≧ v _L , that is, when the v _A + v _B signal after integrating for T ₀ time is v _L ≦ v _A + v _B < v _H , then |
Determine whether v _A −v _B |≧v _D , |v _A −
When v _B | < v _D , in principle, it is determined that the focus is at a low level. As shown in Figure 34, |v _A −v _B |≧v _D
When this happens, it is determined that the focus is out of focus at a low level, and the motor is, in principle, rotated at a low speed in the direction of focus.

〓〓 Now, as mentioned above, when |v _A +v _B |≦v _D , the motor stop signal is output from the control circuit 111 as low level focusing, but as an exception, when the ∞ flag = 1, this Does not output a stop signal. The ∞ flag is set to 1 when shifting to the ∞ hour distance measurement mode, and is reset to 0 in the normal distance measurement mode as described above. When the ∞ flag is set to 1, the control circuit 111 sends the same control signal as before to the motor drive circuit 11.
Output to 3. If the ∞ flag is set to 1 in the low level ranging mode, this is only when the ∞ mode is transitioned to the low level ranging mode. When shifting to the mode, a signal to drive the motor in the infinite direction is output as will be described later. Therefore, when the ∞ flag=1, the motor 8 continues to move the lens group 1 in the infinity direction even if it is determined that focusing is at a low level.

The reason for creating this exception for the ∞ flag = 1 is that when focusing on a subject that is far away or has a reflectance that is such that a low-level focus signal is output, the focus may deviate greatly from the in-focus state to the close side. It has been experimentally confirmed that when distance measurement is started from a position, a focus signal is output due to the influence of leakage current of the light receiving element 6 while the object is still in the out-of-focus process. For this reason, if the motor 8 is stopped with such a false focus signal, it will stop in a state where it is largely out of focus. Therefore, the ∞ flag is used to identify false focusing signals, and as described above, if the ∞ flag = 1, the control circuit 111 outputs the infinite direction signal and continues distance measurement in the low-level distance measurement mode. There is.

〓〓 When the ∞ flag = 0, a motor stop signal is output from the control circuit 111 as in principle, and the motor 8 is stopped.

〓〓 On the other hand, when |v _A −v _B |≧v _D in 〓〓, it is determined that the object is out of focus at a low level. At this time, after it is determined that the focus is out of focus at a low level, the direction of focus deviation is determined, that is, it is determined whether v _A > v _B.

When v _A > v _B , it is the rear pin state, and the control circuit 1
11, it is determined that it is necessary to drive the motor 8 in order to extend the lens group 1 to the nearest side. In the low level ranging mode, the motor rotates at a low speed in principle. The reason is that in low-level ranging mode, the values of the integral signals v _A and v _B are both small, so the S/N is low and a sufficiently reliable direction signal cannot be obtained, so lens group 1 is affected by hunting, etc. This is to reduce unstable operation.

Next, it is determined whether the out-of-focus state at a low level has been determined n ₄ times in a row.
n When a constant direction signal is obtained _four times in a row, it is determined that the S/N of the signals v _A and v _B has become sufficiently high, and the mode returns to the normal ranging mode. In this way, power saving in normal ranging mode (｜v _A −v _B ｜≧v _D
This makes it possible to achieve both the stability of the distance measurement mode at low levels _{(determination is made after integrating up to T 0 )} .

Returning to 〓〓 again, when v _A - v _B is not satisfied, that is, when the front focus is on, it is determined whether the ∞ flag = 1 as in the case of low level focusing described above.

〓〓 When the ∞ flag = 1, the motor 8 is rotated at high speed in order to move the lens group 1 to the close side. The reason for this high speed is to prevent the motor 8 from temporarily slowing down in the vicinity of the false focus signal due to a false focus signal even though it is in an out-of-focus state, as with low-level focusing. It is for this purpose.

〓〓 On the other hand, when the ∞ flag = 0, the motor 7 is driven at a low speed according to the principle described above.

〓〓 For the same reason as below, if the direction signal is outputted more than n ₅ times in a row, it returns to normal distance measurement, otherwise it performs distance measurement again in the low level distance measurement mode.

〓〓 On the other hand, when the focusing state at a low level is determined in 〓〓 and a signal to stop the rotation of the motor 8 is output, the mode shifts to the low level focus distance measurement mode and distance measurement is performed again. . In the focus distance measurement mode at low level, the condition for determining distance measurement completion is v _A + v _B ≧ v _L (v _L
<v _H ) or t≧T ₁ (T ₁ <T ₀ , e.g. T ₁ =1.76 m
sec), which is different from the condition for determining distance measurement completion in the low-level distance measurement mode v _A +v _B ≧v _H or t≧T ₀ . This is similar to the normal focusing distance measurement mode explained in Fig. 20, by making T ₁ shorter than T ₀ , the dead zone is widened as shown in Fig. 35, and lens group 1 is determined to be in focus. This allows the device to be stably stopped at a certain position and to reduce power consumption. In particular, in a low-level focused state, the levels of the signals v _A and v _B are low and the S/N is poor, so stabilizing the focused state by widening the dead zone is extremely effective. Furthermore, v _A + v _B ≧
The reason for setting v _L (v _L < v _H ) is to enable focus determination even in the normal ranging mode in correspondence with the maximum integration time T ₁ .

〓〓 When distance measurement is completed, first, it is determined that v _A + v _B ≧ v _L. When v _A + v _B ≧ v _L , the integrated signal is above the predetermined level even though the integration time has become shorter, so it is determined that the signal has become large enough to enable distance measurement in normal distance measurement mode. , return to normal distance measurement mode and perform distance measurement.

〓〓 When v _A + v _B ≧v _L , it is determined whether |v _A −v _B |≧v _D. When ｜v _A −v _B ｜≧v _D , it is determined that the signal has become sufficiently large, similar to 〓〓, and the mode returns to normal ranging mode.

〓〓 When v _A + v _B < v _L and | v _A − v _B | < v _D , it is determined that the focus is in focus, and the count is continued until t=T ₀ is reached.

〓〓 Determine whether distance measurement in focus distance measurement mode at low level has been repeated n ₃ times, if n ₃ times, return to low level distance measurement mode, if less than n ₃ times, return to low level distance measurement mode. Repeat focus and distance measurement mode. This is the same as the normal focus distance measurement mode, which returns to the low level distance measurement mode every n _third time, and sets the condition for determining distance measurement completion to be v _A + v _B ≧ v _H or t ≧ T ₀ . Therefore, the dead zone is returned to its original state, and a decrease in distance measurement accuracy is prevented. As described above, by changing the distance measurement mode from the low-level focus distance measurement mode to the low-level distance measurement mode, it is possible to simultaneously ensure focusing stability, power saving, and maintenance of accuracy at low levels. becomes possible.

Next, the ∞ hour mode will be explained with reference to FIG. 22. To switch to ∞ hour distance measurement mode,
As mentioned above, this is the case where it is determined that v _A + v _B < v _L in FIG. That is, Fig. 20, 2nd
As explained in the flowchart in Figure 1, if the integrated signals v _A and v _B are both extremely low as a result of distance measurement, it is determined that the distance is ∞, and the ∞ time distance measurement is suitable for distance measurement when the subject 5 is in an infinite state. I'm in the mode.

In the ∞ hour distance measurement mode, it has already been determined that there are an infinite number of ∞ objects 5, so first the motor 8 is driven in the infinity direction at high speed.

〓 Subsequently, the ∞ flag is set to 1 to indicate that an infinite signal has been generated. As explained above with reference to the flowcharts of FIGS. 20 and 21, the ∞ flag is used to distinguish false focus signals, and is reset to 0 in the normal distance measurement mode.

〓 Next, M(6) is stored from the RAM area in the microcontroller as a counter for counting the predetermined number of times n ₆ times.
Set n ₆ to use .

〓〓 In ∞ hour ranging mode, v _A + v _B ≧ v _H or t = T ₂
Completion of distance measurement is determined by . Here, one of the conditions for determining distance measurement completion in normal distance measurement mode |v _A −
The absence of v _B | ≧ v _D is the integral signal in the ∞ time ranging mode as well as in the low level ranging mode.
Since v _A and v _B are both extremely low values | v _A − v _B
This is because the value of | cannot be trusted. Furthermore, ∞
Maximum distance measurement time T ₂ (T ₂ <
T ₀ , for example, T ₂ = 19.3 msec) _, the maximum integration time is shorter than that in the ranging mode at low level because _{v A} + v _B = v _L as the boundary, as described later _.
Then, the direction is determined based on the magnitude relationship of v _A and v _B , and if _{v A} + v _B < v _L , it is determined that the direction is infinite regardless of the magnitude relationship of v A and v _B. Therefore, v _A + v _B ≒
This is to prevent hunting from occurring due to the influence of noise superimposed on the signals v _A and v _B at the time of v _L due to the completely opposite direction determination. In this device, the same effect is obtained by changing the integration time T ₀ to T ₂ instead of changing the value of v _L as shown in FIG.

〓〓 When v _A + v _B ≧ v _H , it is determined that distance measurement is possible in normal distance measurement mode, and distance measurement is performed in normal distance measurement mode.

〓〓 When v _A + v _B ≧ v _H , the distance measurement is completed at t=T ₂ , so the time T ₀ −T ₂ is counted.

〓〓 Determine whether v _A +v _B ≧v _L. v _A + v _B
When ≧v _L , distance measurement should be performed in the low level distance measurement mode as described in FIG. 21, so the system returns to the low level distance measurement mode and enters the next distance measurement cycle.

〓〓 Here, it is determined whether n ₆ consecutive times have passed since the ∞ hour distance measurement mode started. n If it has not reached _{the 6th} time, return to 〓〓 again and set the maximum integration time T ₂
Perform distance measurement. In other words, this is the predetermined time (predetermined number of times n ₆ times) after starting distance measurement in ∞ mode.
The maximum integration time is changed to T ₂ (T ₂ <T ₀ ), but not changed to T ₃ (T ₃ <T ₂ <T ₀ ) as described later.

The reason for this is that, as mentioned above, the signal is small because the object is actually far away or the reflectance is low, so it is okay to judge it as infinity. One is that the reflectance is unavoidable, and the other is that the object is at a distance that can be measured, but because the size of the object is finite, the distance of the object and the current position of the distance measurement system are greatly different, so it is difficult to spot. The image P or the light-receiving element 6 is separated from the subject 5, and at first it is driven in the infinite direction due to the infinity determination, and when the reflected light spot image P begins to form correctly on the light-receiving element 6, distance measurement becomes possible, and v This is a case where the focus position is driven by the magnitude relationship of the _A and _vB signals.

In such a case, the maximum integration time is T ₃ (T ₃ < T ₂
< T ₀ ), the dead zone will widen,
The response is delayed, and as a result, the correct control of the motor 8 is delayed, resulting in an overrun of the in-focus position. In order to eliminate such drawbacks, the maximum integration is performed for n ₆ times in order to distinguish between a true infinite state and a short-term infinite state during the focusing process, as just described. The distance measurement is performed without changing the time to T ₃ and keeping it at T ₂ (T ₂ < T ₀ ). Note that as long as distance measurement is performed in the ∞ time distance measurement mode, the control circuit 111 always outputs a signal to drive the motor 8 in the infinite direction. However, when the lens 1 reaches the infinite end, the infinity switch 262 is turned on and the motor 8 is stopped.

〓〓 n After _{the 6th} time, the maximum integration time T ₃ (T ₃ < T ₂ ,
For example, distance measurement is performed at T ₃ =1.76 msec). Completion of distance measurement is determined by v _A +v _B ≧v _L or t≧T ₃ . Similar to the low-level focus distance measurement mode described above, this widens the dead zone by setting the maximum integration time to T ₃ (T ₃ <T ₂ ), thereby achieving both stability and power saving.

〓 If v _A + v _B ≧ v _L , the maximum integration time T ₃ (T ₃ <
Since the comparison value v _L is reached even though T ₂ ) is shortened, it is determined that the signals v _A and v _B are large enough to enable distance measurement even in the normal distance measurement mode, and the mode returns to the normal distance measurement mode.

〓 When v _A + v _B < v _L , the distance measurement result is the integral signal v _A , v _B
Since the level of is still extremely low, it is determined that the subject 5 is again in an infinite state, and T ₀ -T ₃ time is counted.

〓〓 Next, it is determined whether distance measurement has been performed n ₇ times at the maximum integration time _T3 , and if it has not reached n ₇ times, the process returns to 〓〓 again.

〓 n When _{the seventh} distance measurement is completed, the maximum integration time is set to T ₂ and the distance measurement is performed once again.

Here, every _7th predetermined number n, the integration time is
The purpose of returning to T ₂ is to prevent a decrease in distance measurement accuracy, similar to the above-mentioned low-level focus distance measurement mode. In addition, at 〓, the maximum integration time is n ₆ times in a row.
In order to measure the distance at T ₂ , we set M(6) = n ₆ , but
Here, since it is only done once, M(6)=1.

With the above, Figure 20 mainly describes the five distance measurement modes: 1 Normal distance measurement mode 2 Normal focus distance measurement mode 3 Low level distance measurement mode 4 Low level focus distance measurement mode 5 ∞ time distance measurement mode ~Second
A detailed explanation has been provided based on the flowchart in Figure 2. As is clear from this explanation, the automatic focus detection device according to the present invention obtains highly reliable and stable operation by appropriately switching the distance measurement modes 1 to 5 above to perform distance measurement. This also made it possible to achieve both power savings.

In the above embodiment, in-focus or out-of-focus is determined based on the magnitude relationship of the absolute value of the difference |v _A −v _B | between the integral signals v _A and v _B indicating the light receiving position of the projected spot image P. However, it goes without saying that this can also be determined from a ratio such as v _A /v _B. That is, the present invention can be applied to anything as long as the magnitude relationship between the signals v _A and v _B is known. Further, instead of determining the signal level from v _A +v _B as in the above embodiment, the signal level may be determined from either v _A or v _B. That is, the present invention can be applied to any device as long as the level states of the signals v _A and v _B can be known. moreover,
It goes without saying that the present invention is applicable even if the light receiving element has three or more photosensitive areas.

As described above, according to the present invention, the image of the object is determined from the integral value of the output of the light receiving element which receives the reflected light of the projected spot image projected onto the object and outputs a signal according to the light receiving position. An automatic focus detection device for an imaging optical system that forms an image on a predetermined focal plane, the device comprising: a time detection means for detecting that the projection time of the projected spot image has reached a predetermined time; and an output of the light receiving element. level detection means for detecting that the integral value of the light receiving element has reached a predetermined level; and determining means for determining the focusing state of the imaging optical system based on the integral value of the output of the light receiving element, so that the focal position can be detected from the integral value of the output of the light receiving element. When the focus position is reached, the focus position is detected immediately, so that there is no waste in power consumption and focus detection time, and an automatic focus detection device with high power saving effect and high detection speed can be provided. Therefore, the present invention is particularly suitable for automatic focus detection devices such as cameras, which cannot incorporate a large-capacity power supply due to miniaturization, and in which the quality of focus detection speed may cause a momentary shutter movement to be missed. It is extremely effective.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional example, FIGS. 2 to 8 are schematic diagrams showing an optical system of an automatic focus detection device according to the present invention, and FIGS. 9 to 19 are automatic focus detection according to the present invention. Explanatory diagram of the electric circuit of the device, Figures 20 to 2
FIG. 4 is an operation flowchart of the automatic focus detection device according to the present invention, and FIGS. 25 to 36 are supplementary explanatory diagrams of the operation flowcharts shown in FIGS. 20 to 24. 1...Photographing lens, 2...Planned focal plane, 3...
Light projecting element, 4... Light projecting lens, 5... Subject, 6
... Light receiving element, 7 ... Light receiving lens, 8 ... Motor, 9 ... AF circuit.

Claims (1)

[Scope of Claims] 1. Projecting spot light onto a target object, and forming an image of the target object based on the magnitude relationship between the integral values of the outputs of at least two light-receiving elements that change depending on the receiving position of the reflected light. In an automatic focusing device for an imaging optical system that forms an image on a predetermined imaging plane, a first detection circuit detects that the difference between the respective integral values has reached a first level, and a sum of the respective integral values. a second detection circuit that detects that the level has reached a second level, and when either of the first and second detection circuits first detects the level, An automatic focus adjustment device comprising: a determination circuit that determines a focus adjustment state of the imaging optical system depending on whether the image forming optical system is detected. 2. Claim 1, characterized in that when the first detection circuit first detects the first level, the determination circuit determines that the imaging optical system is in an out-of-focus state. focusing device. 3. The method according to claim 2, wherein when the second detection circuit first detects the second level, the determination circuit determines that the imaging optical system is in focus. Automatic focus adjustment device. 4. Projecting a spot light beam onto the target object, and forming an image of the target object on a predetermined imaging plane based on the magnitude relationship between the integral values of the outputs of at least two light-receiving elements that change depending on the receiving position of the reflected light. In an automatic focus adjustment device of an imaging optical system for forming an image, a first detection circuit detects that the difference between the respective integral values has reached a first level, and the sum of the respective integral values has reached a second level. a second detection circuit that detects that the spot light has become hot; a third detection circuit that detects that the projection time of the spot light has reached a predetermined time; and one of the first, second, and third detection circuits. When first detects the level or the predetermined time, the imaging optical system is in an out-of-focus state depending on which one of the first, second, and third detection circuits detects the level or the predetermined time. A discriminating circuit that determines whether the light is in focus, in focus, or whether the output of each light receiving element is at a low level, and the first, second, and third detection circuits first detect the level or the predetermined time. An automatic focus adjustment device comprising a circuit that prohibits projection of the spot light when the spot light is detected.