JPS6049309A - Focus information detector - Google Patents

Abstract

PURPOSE:To obtain a small-sized, high-performance device which employs not a triangulation method, but an active system by oscillating a lens in the optical- axis direction, and photodetecting reflected luminous flux from a subject by a photosensor and obtaining focus information corresponding to subject distance from the timing of the maximum value of the output of the photosensor. CONSTITUTION:A light emitting element 14 emits light toward the subject 1, and an optical system 15 for convergence converges the light emitted by the light emitting element 14; and convergence state varying means 20 and 21 vary the distance position of which the light is converged by the optical system 15 by varying the distance between said light emitting element and optical system 15 to vary the state of convergence on the subject 1. Further, the photosensor 16 photodetects the luminous flux reflected by the subject 1 and generates a photoelectric conversion output corresponding to the quantity of light projected upon the photodetection surface, and focus information signal detecting means 27 and 28 detect the maximum value from the photoelectric conversion output of the photosensor 16 to calculate the timing of the maximum value, and obtain a focus information signal S6 corresponding to the distance position of the subject from the timing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a focus information detection device, and more particularly to a device for detecting focus information used in film cameras, video cameras, and the like.

(Prior Art) Conventionally, some autofocus mechanisms of video cameras and the like employ an active type focus information detection device using triangulation. The principle of this conventional focus information detection device is explained first.
To explain with a diagram, a light emitting element 4 and a condensing lens 5 are respectively arranged on the left and right sides of the video camera body with a photographing lens 2 and an image pickup tube 3 in between. When the beam is irradiated, this infrared beam is reflected by the subject 1 and then passes through the lens 5.
This allows the light to be focused and received by the optical sensor 6 located behind it. The optical sensor 6 has a light receiving section 6 divided into two parts.
a and 6b, and is movable in the direction indicated by the arrow X, which is perpendicular to the optical axis direction indicated by the arrow y of the photographic lens 2 and image pickup tube 3 of the video camera. When the infrared beam reflected from the subject 1 is incident on the optical sensor 6, the optical sensor 6 moves so that the amount of light at the two light receiving sections 6a and 6b becomes equal. Since the angle θ at which the light emitting element 4 and the lens 5 view the subject 1 changes depending on the subject distance, the subject distance is calculated from the position of the optical sensor 6. Therefore, by linking the movement of the optical sensor 6 and the extension of the photographic lens 2, the motor can move the photographic lens 2 in the direction of the optical axis indicated by the arrow y to perform a focusing operation.

However, since the conventional focus information detection device described above uses triangulation, a certain distance 1 is naturally required between the light emitting element 4 and the lens 5, and in order to improve focusing accuracy, , the distance viewing must be increased to some extent. Therefore, there is a limit to the miniaturization of video cameras equipped with the above-mentioned focus information detection device.

(Objective) An object of the present invention is to provide a compact and high-performance focus information detection device that takes advantage of the above points and adopts an active method that does not rely on triangulation.

(Summary) The focus information detection device of the present invention focuses light from a light emitting element using an S light lens and projects it onto a subject, and also vibrates this lens in the optical axis direction to vary the distance from the light emitting element. The light beam reflected from the object is received by the optical sensor, and focus information corresponding to the object distance is obtained from the timing of the maximum value of the output of the optical sensor.

(Example) Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 2 is a block diagram of a schematic configuration of a focus information detection device showing an embodiment of the present invention. This focal information signal system [1
1 is provided in the video camera body, and its main components are a light emitting element 14 that emits infrared light, and the light emitting element 1.
40, a modulator 17 for modulating the amount of infrared light emitted at a constant frequency, a focusing lens 15 for focusing the infrared light emitted by the light emitting element 14, and an insulating bobbin 18 holding the lens 15. and a moving coil 21 and a drive detection coil 22 wound around the outer periphery of the bobbin 18,
Magnets 31 and 52 arranged around the outer periphery of these coils 21 and 22 and an oscillator 1 that emits a constant vibration frequency signal for vibrating the condensing lens 15 in the optical axis direction.
9 and the output of the oscillator 19 is amplified and guided to the moving coil A/21, and the lens 15 and bobbin 18 are vibrated in the optical axis direction by the electromagnetic action of the moving coil 21 and the magnet 31, and the output is directed toward the subject 1. A moving coil drive circuit 20 for varying the condensing state, a voltage amplifier 23 for detecting vibrations of the lens 15 and bobbin 18 using a drive detection coil 22 and amplifying the detected vibrations, and a voltage amplifier 23 for amplifying the vibrations of the lens 15 and the bobbin 18, which are reflected by the subject 1, and moving the photographing lens 12. Among the transmitted light, an infrared light reflecting mirror 24 guides visible light to the image pickup tube 13 and reflects only infrared light, and a photoelectric conversion surface 1 of the image pickup tube 13.
Infrared light reflecting mirror 2 located at a position optically equivalent to 5a.
an optical sensor 16 that receives the infrared light reflected by the sensor 16; and a bandpass filter (hereinafter referred to as BPF) 2 that detects only the vibrational component of the infrared light from the photoelectric conversion output of the sensor 16.
5, an envelope detector 26 that detects the envelope of the output waveform of this B P F 25, a peak value detector 27 that detects the maximum value of the envelope waveform, and a vibration waveform from the voltage amplifier 26 that detects the peak value. The sampling and holding circuit 28 samples at the timing of the maximum value from the device 27 and holds the same sampling level as a focus information signal.

The light emitting element 14 is fixed to a stationary member, one lead terminal thereof is connected to the output end of the modulator 17, and the other lead terminal is grounded. Therefore, the amount of infrared light emitted by the light emitting element 14 is modulated at a modulation frequency of 100 KHz, for example. Light emitting element 14
The condensing lens 15 is located at the front position of the insulating bobbin 18.
The main plane of the bobbin 18 is held by the upper and lower damper members 29a and 29b, and the bobbin 18 is supported by an immovable member. Therefore, the lens 15 and the bobbin 1 holding it
8 can move back and forth in the optical axis direction indicated by arrow Y. A moving coil 21 is wound around the front outer periphery of the bobbin 18, and a drive detection coil 22 is wound around the rear outer periphery. Then, the outer circumferential position of the moving coil 21 and the outer circumferential position KFi of the drive detection coil 22 are respectively,
Ring-shaped magnets 31 and 32 fixed to a stationary member (not shown) are provided. This magnet) 31.
32 is a magnet in which half-ring-shaped magnets with opposite north and south poles are butted against each other from above and below to form one ring.

When the moving coil 21 is energized, the magnetic field generated in the coil 21 and the magnetic field generated by the magnet 31 interact to cause the bobbin 18 to move.
is made to vibrate in the optical axis direction of the lens 15. Moving coil A/21 for vibrating this bobbin 18
The current flowing through the butterfly oscillator 19 is provided by a moving drive circuit 20, and the output of the butterfly oscillator 19 is guided to the moving drive circuit 20. The oscillator 19 oscillates a frequency signal of, for example, 10 Hz. When the bobbin 18 vibrates due to the moving coil 21 being energized, the drive detection coil 22 fluctuates in response to the magnetic field of the magnet 52, and an induced current is generated in the detection coil 22. A corresponding vibrational electromotive force is generated. This electromotive force is amplified by a voltage amplifier 25, and then further led to a sampling and holding circuit 28K.

The optical sensor 16 has a sufficiently high light-receiving sensitivity for infrared light, and of the reflected light from the subject 1, only the infrared light is diverted by 90 degrees by the infrared light reflecting mirror 24 and reaches the light-receiving surface. When the light is incident, it emits a photoelectric conversion signal according to the amount of light received. When this photoelectric conversion signal is guided to BPF25,
The center frequency of the BPF 25 is 100) G(z), and therefore the modulated infrared light vibrated at the frequency of 100 KHz is demodulated.The output of the BPF 25 is guided to an envelope detector 26 and - After wave detection is performed, the signal is guided to the peak value detector 27, and the timing of the maximum value of the output of the envelope detector 26 is detected as a pulse.

The output pulse of the peak value detector 27 is guided to the sampling hold circuit 28, and the level of the output waveform of the voltage amplifier 23 at the point corresponding to the output pulse of the peak value detector 27 is determined by the sampling hold circuit 28.
It starts to be output from 8 onwards. The output of this sampling and holding circuit 2B becomes a focus information signal.

Further, among the reflected light from the subject 1, the visible light that has passed through the infrared light reflecting mirror 24 is t! & When the light is received by the photoelectric conversion surface 15a of the picture tube 13, the electric signal photoelectrically converted by the photoelectric conversion surface 13a is amplified by the voltage amplifier 35, and then converted to NT by the well-known video processor 36.
It is converted into an SC video signal.

Furthermore, the lens position of the m shadow lens 12 is detected by a photographing lens position detection mechanism 37 (described later), and when the focus information signal is obtained, the in-focus position is calculated from the parfocal information signal. , the photographing lens 12 is driven by a motor to the in-focus position.

The focus information detection apparatus shown in FIG. 2 is roughly constructed as described above. below.

Furthermore, the detailed configuration and operation of the focus information detection device (2) will be explained.

When the video camera is pointed at the subject 1 and a power switch (not shown) is turned on, the oscillation frequency signal of 10 Hz from the oscillator 19 is amplified by the moving coil drive circuit 20 and supplied to the moving coil 21 . The condenser lens 15 held in the center vibrates in the optical axis direction Y, but since the light emitting element 14 is fixed at this time, when the condenser lens 15 torsionally vibrates in the optical axis direction YK, the light emitting element 14 and the condenser vibrate. The distance from the optical lens 15 will change. To explain this with reference to FIG. 3, assuming that the distance between the light emitting element 14 and the condensing lens 15 is a certain distance, this distance 1 changes due to the vibration of the condensing lens 15. Therefore, at this time, the position at which the condensing lens 15 converges the light from the light emitting element 14 varies from the distance 1a from the condensing lens 15 to the distance corresponding to the vibration period of the condensing lens 15. do. In other words, for example 1,6a=1m
,, If #=10m, then 10 from the 1m distance position Pa
The focal point of the light from the light emitting element 14 by the lens 15 oscillates up to the distance position Pb of m. If position P
Assuming that a subject exists at a certain position Px between a and Pb (subject distance/X), when the light flux emitted from the light emitting element 14 is focused on the subject at this position Px, the same subject A clear minimum spot light area 41 is formed above, and when the focus is shifted from the subject, the distance is 1iP.
An unclear and large light area 42 is formed on the object x.

Since the position where the irradiated light from the light emitting element 14 is focused by the lens 15 (hereinafter referred to as the condensing position) is reciprocating between the positions Pa and Pb at a frequency of 10 Hz, the position Px is now When focusing on the subject, the size of the spot light on the subject changes at a frequency of 20 Hz, which is twice the vibration frequency of 10 Hz of the condensing lens 15. That is, the condensing lens 15 is the light emitting element 1.
4 while the light focusing position moves from position Pa to pb, and while the focusing lens 15 approaches the light emitting element 14 and the light focusing position moves from position @pb to position @Pa. Therefore, since the light emitted from the light emitting element 14 is focused on the subject at the same position 1iPx to obtain the minimum spot light area 41, the frequency of the signal is doubled to 20 Hz. .

Here, paying attention to the light receiving surface of the optical sensor 16, the reflected light beam from the subject 1 is focused on the light receiving surface by the photographing lens 12, but at this time, even if the photographing lens 12 is not in the in-focus position, When the minimum spot light area 41 is formed on the subject, the same spot light area 41 is received as a clear and small spot light area 43 on the light receiving surface of the optical sensor 16 as shown in FIG. , large light area 4 on the subject
2 is formed, same party area 42it light sensor 16
As shown in FIG. 4 (CB), the light is received as an indistinct and relatively large light area 44 on the light receiving surface. That is, as shown in FIG. 4(A), a clear and small spot light area 4
When the light of No. 3 is received by the optical sensor 16, the amount of light to the optical sensor 16 increases, and as shown in FIG. When the light is received by the optical sensor 16, the amount of light directed to the sensor 16 decreases.

As a result, as the output of the optical sensor 16, the above 1001
An electrical signal in which a QOHz frequency signal is superimposed on a 1z frequency signal is obtained. This is shown in Figure 5 (A)-(
According to the theory IJII-j according to the time chart shown in F), the condensing lens 15 is the same lens, and the condensing position P by 15 is
When vibrating between a and Pb (see Fig. 5 (A)), at this time, the optical sensor 16 receives reflected infrared light from the subject 1 at the distance @Px, so the output of the optical sensor 16 SI is that the frequency signal of 100KH2 is at the distance position P.
It is superimposed on the 20Hz frequency signal that has the maximum value at x,
Moreover, this superimposed frequency signal component of 100 Kl'lz becomes a waveform signal that exhibits the maximum amplitude M at the waveform position corresponding to the above position Px (see Figure 5 CB))
. When the output S of the optical sensor 16 is guided to the BPF 25, only the modulation component of 100 KHz is separated and extracted (2) (see Fig. 5 (C)).

The amplitude of the output S of the B P F 25 changes depending on the convergence state on the subject at position Px, and shows the maximum amplitude at the timing corresponding to the 10th position of the subject 1i1Px. When the output S2 of the BPF 25 is guided to the envelope loop detector 26, the BPF 25
The envelope of the output waveform is the output S3 of this detector 26.
(See FIG. 5(D)). Then, when the envelope waveform output S3 detected by the envelope detector 26 is guided to the peak value detector 27, the maximum value of the envelope waveform output S3 becomes the timing pulse S4.
(See FIG. 5(E)).

The peak value detector 270 circuit is configured as shown in FIG. 6, for example, and the circuit configuration and operation of the detector 27 will be explained with reference to the time charts of FIGS. 7(A) to (G). The output S of the envelope detector 26, (
(See FIG. 7(A)) and clock signal 5 (IFi sampling hold circuit 51 has an equal power of 5, and the same sampling hold is applied.

It is sampled in circuit 51 by clock signal S0. The digital signal SO is a constant frequency signal, and in this embodiment, the envelope detector 26 is generated by a signal So of 10 times the vibration frequency 10ax of the condensing lens 15. The output S3□ (see FIG. 7(B)) of the sampling and hold circuit 51 obtained by sampling the output of Output waveform 812 (Fig. 7(C)
) is a differential pulse waveform that is separated into a positive pulse and a negative pulse with the maximum value of the envelope soap waveform output S as a boundary, so when this differential pulse waveform Ss2 is then guided to the level sensors 55 and 56, respectively. , each level sensor 55,56 has a threshold potential 55.
a, 56a is set, and the level sensor 55
, 56 output S381 SH changes from the "H" level to the 1L" level at the point corresponding to the differential pulse waveform S3□ exceeding each threshold hold potential 55a, 56B (see FIG. 7CD), (E) ).

The output terminal of the level sensor 55 is connected to the set input terminal of the R-87 lip flop 59 consisting of 57 and 58, and the output terminal of the level sensor 56 is connected to the reset input terminal of the R-87 lip flop 59. Since it is connected, the output S of the envelope detector 26
When the waveform No. 3 has an upward slope, when the output Ss3 from the level sensor 55 is guided to the R-8 tree 70 tube 59 as a preset input, the output S of the R-8 tree 70 tube 59 becomes 'H' level. After this, when the waveform of the output S8 of the envelope detector 26 becomes downward slope from the maximum point, the output 834 of the level sensor 56 is guided to the 4-piece 59 of the 7-S flip 7 as a reset input. The output S of the knob 59 becomes the "L" level when the output S84 of the level sensor 56 first changes to the "L" level (see FIG. 7(F)). The output "'ss" of this flip-flop 59 is led to a pulse generator 60, and the pulse generator 60 changes the output "Sas" from the 7-rip-punch loop 59 from the 1" level to 6L.
Triggered when the level changes, one pulse S
4 (see FIG. 7<a) p0C (7) Output pulse from the pulse generator 60, that is, the peak value detector 27
As mentioned above, the timing of the output pulse S4 coincides with the timing at which the output waveform of the envelope detector 26 reaches its maximum (strictly speaking, it is slightly shifted from 5 as shown in FIG. 7 above, but this (The amount of deviation is so small that it can be virtually ignored).

When the output pulse S4 of the peak value detector 27 is guided as a sampling pulse to the sampling and hold circuit 28 as shown in FIG. and the timing pulse S4 having the maximum value are matched by temperature in the sampling and hold circuit 2B, and the output S of the voltage amplifier 26 is sampled and held at the timing of the pulse S4 (see FIG. 5 CF)). The output voltage S6 of the sampling hold circuit 28 is equal to the output Sl of the voltage amplifier 23.
This is the voltage at a point in l that coincides with the timing of the pulse S4.

That is, the timing of the pulse S4 corresponding to the peak value of the infrared light detected by the optical sensor 16 is shifted by 1itK of the object, and the output voltage S6 of the sampling and hold circuit 28 is changed according to the timing shift of the pulse S4. changes. Therefore, this output voltage S6 becomes a focus information signal whose voltage level changes depending on the distance position of the subject.

Although this focus information signal S6 can be used as it is for distance display, the photographing lens 12 can be automatically moved to the in-focus position based on the value of this focus information signal S.

Next, an automatic focusing device that automatically moves the photographing lens /I'12 to the in-focus position based on the focus information signal S6 obtained as described above will be described.

In order to control the photographic lens 12 to the in-focus position, a mechanism m67 for detecting the position of the photographic lens 12 is required, and the mechanism 371i is constructed as shown in FIGS. 8 and 9. In FIG. 8, a gear 63a is formed on the outer periphery of a rotating barrel 61 for moving the photographic lens 12, and the gear 61a is integrated with the rotating shaft of a motor 62 driven based on the focus information signal S. The gear 63 meshes with the gear 64 via a gear 64. Therefore, when the motor 62 rotates, the rotary barrel 61 rotates, thereby causing the photographing lens 12 to move in the optical axis direction. A long hole 66 parallel to the lens optical axis 0 is formed in the fixed frame 65 at the rear of the rotating barrel 61, and a support member 67 that moves integrally with the photographing lens 12 projects from the long hole 66. A light emitting element 68 is provided at the tip of the support member 67, and a collimator lens 69 disposed below the light emitting element 68 is also integrally supported by the support member 67. A semi-transparent mirror 70 is placed below the collimator lens 69 at a 45° angle.
(see FIG. 9), and at the same height as the semi-transparent mirror 70 is a correction optical sensor 71 that receives light from the light emitting element 68 reflected by the mirror 70.
is located. A spatial filter 72 is arranged horizontally below the semi-transparent filter 70. This spatial filter 72 is formed by punching out the inside of an opaque rectangular member whose longitudinal direction coincides with the direction of the optical axis 0 of the photographing lens 12 into a triangular shape having sloped sides in the longitudinal direction.
The light from the light emitting element 68 that has passed through the semi-transparent mirror 70 passes through the triangular window 72a of the filter 72. A condenser lens 73 is arranged below the spatial filter 72, and this condenser lens 7
A lens position detection optical sensor 74 is arranged below the lens 73 to receive the light condensed by the lens 73.

Note that the semi-transparent mirror 70, the spatial filter 72. The condenser lens 73 and the optical sensors 71, 74 are fixedly attached to a fixed member (not shown).

Regarding the operation of this photographic lens position detection mechanism 37, the light from the light emitting element 68 is converted into a substantially parallel beam by the collimator lens 69, and a part of this parallel beam is reflected by the semi-transparent mirror 70 for correction. The light enters the optical sensor 71. The remaining part of the parallel light beam from the collimator lens 69 passes through a semi-transparent mirror 70 and passes through a spatial filter 72.
Since the light beam passes through the triangular window 72a, part of the light beam is blocked by the triangular window 72a, and the light beam passes through the atocondenser lens 7.
3, the light is focused by the optical sensor 74 for lens position detection.
incident on .

The parallel light beam transmitted through the semi-transparent mirror 70 is enlarged in FIG. 10, and as shown in FIG. The amount of light passing through the window 72a is determined by the movement position of the light area 75 shown in the arrow C direction, that is, the light emitting element 6
8 changes depending on the position of the photographing lens 12 along the direction of the optical axis O. Therefore, the optical sensor 740
The photoelectric conversion output also changes accordingly. In other words, the position on the optical axis 0 of the photographing lens 120 corresponds to the photoelectric conversion output of the optical sensor 740, and if the photographing lens 12 is in the extended position so as to focus on a subject at a short distance, then at this time , the amount of light passing through the triangular window 72a increases and the light sensor
The photoelectric conversion output of 74 also increases, and on the contrary, the shooting ν
When the lens 12 is in a retracted position so as to focus on a distant object, the amount of light passing through the triangular window 72a decreases, and the photoelectric conversion output of the optical sensor 740 decreases. Therefore, the position of the photographing lens 12 can be detected from the photoelectric conversion output of the optical sensor 74. That is, the photoelectric conversion output of this optical sensor 74 becomes a signal of photographing lens position information.

Incidentally, since the output of the light emitting element 68 may decrease due to aging, the correction optical sensor 71 is used to eliminate the influence of fluctuations in the output of the light emitting element 68. That is, the ratio between the photoelectric conversion output of the optical sensor 71 and the photoelectric conversion output of the optical sensor 74 is determined by a division circuit (not shown), and the output of this division circuit is proportional to the position of the photographing lens 12. You can get the signal. Note that when the light emitting element <58 is one that has very little change over time, the semi-transparent mirror 70
It is a matter of course that there is no need to use the degree correction optical sensor 71 and a division circuit (not shown).

Furthermore, instead of the photographing lens position detecting mechanism 37, a photographing lens position detecting mechanism 37A having a simplified structure as shown in FIG. 11 may be used.

In this photographic lens position detection mechanism 37A, a conductive member 81 protrudes from the eldest L66 of the fixed frame 65 of the lens barrel of the photographic lens 12, and the tip of the conductive member 81 remains immovable parallel to the optical axis of the photographic lens 120. It is designed to come into sliding contact with a resistor 82 fixedly disposed on the member. and,
A constant DC voltage is applied between both ends 82a and 82b of this resistor 82 by a DC power source (not shown), so that a voltage corresponding to the position of the photographic lens 120 is detected from the conductive member 81 on Saturdays and Sundays. It has become. That is,
When the photographic lens 12 is extended forward, the conductive member 81
slides on the resistor 82 in the direction approaching the front end 82a, so the voltage between the conductive member 81 and the rear end 82b of the resistor 82 increases, and on the contrary, the photographing lens 12+! l''- When the conductive member 81 is retracted backward, the conductive member 81 slides on the resistor 82 toward the rear end 82b, and the voltage between the conductive member 81 and the rear end 82b of the resistor 82 decreases. Since the position of the photographing lens 12 can be detected from the voltage between the conductive member 81 and the rear end 82b of the resistor 82, this voltage becomes the photographing lens position information signal.

FIG. 12 is a block diagram of an automatic focusing device that moves the photographing lens 12 to a focusing position based on the focus information signal (S,) and the photographing lens position information signal. The focus information signal and the photographing lens position information signal are sent to the A/
After converting into digital values by inputting them to D converters 91 and 92, the digital values of the focus information signal and the photographing lens position information signal are sent to the microcomputer 93.
The amount of movement of the photographing lens 12 to the in-focus position is calculated by guiding the image to the focal point and performing arithmetic processing. The amount of lens movement determined by the microcomputer 93 is determined by the D/A converter 9.
4 is converted into an analog quantity again, and this analog quantity is supplied to the lens drive motor 62 to be connected to the rotary cylinder 61 (8th, 11th
(see figure) rotates and the photographing lens 12 moves to the in-focus position.

A flowchart of the instruction execution procedure of the microcomputer 93 in the automatic focusing device shown in FIG. 12 is shown in FIG. 13. That is, the A/D converter 91
The focus information value converted into a digital value is temporarily stored in the memory, and the focus position of the photographing lens 12 is calculated based on the stored focus information value, and the requested focus position value is stored in the memory. Ru. Next, the above A/D
The photographic lens position information converted into a digital value by the converter 92 is taken in, and the information value is normalized and stored in a memory so that it can be compared with the focus information value. Thereafter, the photographing lens focusing position value read from the memory is subtracted from the photographing lens position information value read from the memory to calculate the driving amount of the photographing lens, and this driving amount is output. After outputting the driving amount of the photographic lens, the A/D-converted focus information value is again taken in and stored, and the above operation is repeated thereafter.

Based on the flowchart shown in FIG. 13 above, if the signal processing system in the microcomputer 93 is further summarized by component, the automatic focusing device shown in FIG. I can do it.

As mentioned above, the focal point information detected by vibrating the focusing position of the irradiated light of the light emitting element 14 by the focusing lens 15 is converted into a micro-combination tool 93 after A/D conversion.
The focal information storage means (memory) 93a
This stored focus information value is then led to the photographing lens focus position calculation means 93b, where the focus position of the photographic lens 120 is calculated based on the focus information value, for example, by a method described later. Ru. The focus position determined by this calculation is guided to the photographing lens position calculation means 93C. This photographic lens position calculation means 93c takes in the photographic lens position information detected by the photographic lens position detection mechanism 37 (57A) described in detail, and performs normalization calculation so that it can be compared with the above-mentioned in-focus position. The photographing lens position information and focus position information from the photographing lens position calculating means 93c are led to the photographing lens driving amount calculating means 93d, and the amount by which the photographing lens 12 is driven to the focusing position is multiplied by 11. The determined driving amount is supplied to the photographing lens driving motor 62, whereby the photographing lens 12 is actually driven to the in-focus position.

Here, it will be described that the focusing position calculation means 93b of the photographing lens in the microcomputer 93 calculates the focal position of the photographing lens based on the focus information value. As shown in FIG. 15, the distance from the light emitting element 14 to the condensing lens 15! 8. Assuming that the distance from the condensing lens 15 to the subject 1 is Noe, and the focal length of the condensing lens 15 is fl, the condensing lens 15 is focused and the infrared light from the light emitting element 14 is directed onto the subject 1. When focused on , the well-known lens formula holds true. Further, from the optical sensor 16 to the photographing lens 12
If the distance from the photographing lens 12 to the subject 1 is 10, the distance from the photographing lens 12 to the subject 1 is f2, and the focal length of the photographing lens 12 is f2, then the photographing lens 12 reaches the in-focus position and the image of the subject 1 is captured by the optical sensor 16. When connected to the light receiving surface of (1) above,
Similarly to the formula, from the well-known lens formula, the following holds true. The distance 'x, px from the condensing lens 15 or photographing lens 12 to the subject 1 is the above-mentioned distance! Since it is sufficiently large compared to 1°-13o, -13, #43. ' can be approximated as Therefore, from the above equations (1) and (2), 0=□...(3) 1 1 1 f, -f, -11? .

The focal length f, , f is the photographing lens 12. Since it is constant due to the condensing lens 15, the distance! , if you know the distance from the above equation (6)! 0 is the photographing lens 1
It is clear that two in-focus positions can be achieved.

By the way, as explained in connection with the focus information detection device shown in FIG. By matching the converging lens 1
This is because the voltage level can be obtained according to the distance from 5 to subject 1.

From the focus information signal obtained at this voltage level, it is possible to know the distance between the light emitting element 14 and the condensing lens 15 at this time. In order to focus, the optical sensor of the same lens 12
The payout distance from 16 is -13o. Note that, as is clear from the above equation (5), when the focal length f of the condensing lens 15 is equal to the focal length f2 of the photographing lens 12, the distance obtained from the focus information signal! , becomes the distance 4o as it is, and it becomes possible to omit the focusing position calculation means 93b of the photographing lens in the microcomputer 93 shown in FIG. 14 above.

In the focus information detection device U of the above embodiment, the focusing lens 15 is vibrated in order to vary the focusing position of the light emitted from the light emitting element 14, but the focusing lens 15 is fixed. Instead, it goes without saying that the light emitting element 14 may be configured to vibrate in the optical axis direction by a similar electromagnetic effect or the like.

Further, in the above focus information detection device, the light emitted from the light emitting element 14, reflected by the subject 1, and received by the optical sensor 16 is made to pass through the photographing lens 12.
Since the optical sensor 16 only needs to be able to receive the focused state of the light for detecting focus information projected onto the subject 1, the light for detecting focus information does not necessarily need to pass through the photographing lens 12.

Furthermore, in the focus information detection device, the focus information signal is generated by matching the timing of the maximum value of the photoelectric conversion output detected by the optical sensor 16 with the vibration waveform of the condensing lens 15 in the sampling hold circuit 28. 5 is taken out as a signal with a level corresponding to the subject distance, but even without comparing it with the vibration waveform mentioned above, it is possible to estimate the timing of two adjacent maximum values from the output waveform detected by the optical sensor 16. , a focus information signal corresponding to the subject distance may be obtained from the duty ratio.

(Effects) As described above, according to the present invention, since an active method that does not rely on triangulation is adopted, the light emitting element and the optical sensor can be installed close to each other, resulting in a compact structure. At the same time, it is possible to obtain a highly accurate focus information signal.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of an example of a conventional focus information detection device, FIG. 2 is a block diagram of a focus information detection device showing an embodiment of the present invention, and FIG. 3 is a collection of the components in FIG. Figures 4 (A) and 4 (B) illustrate the variable range of the focusing position of light from the light emitting element due to the vibration of the optical lens. 5(A) to (F) are time charts representing signal waveforms of each part in the focus information detection device shown in FIG. 2 above; FIG. 6 fi is a focus point shown in FIG. 2 above; A block diagram of the peak value detector in the information detection device; FIGS. 7(A) to (G) are time charts representing signal waveforms of each part in the peak value detector shown in FIG. 6; FIG. FIG. 9 is a side view of the main part of the photographing lens position detection mechanism shown in FIG. 8, and FIG. 10 is a perspective view showing an example of the photographing lens position detection mechanism shown in FIG. 9 is an enlarged plan view of the spatial filter, FIG. 11 is a perspective view showing another example of the photographing lens position detection mechanism, and FIG. 12 is an enlarged plan view of the spatial filter in FIG. A block diagram of an automatic focusing device that controls the focusing position of a photographic lens. FIG. 13 is a flowchart showing the instruction execution procedure of the microcomputer in FIG. 12, and FIG. FIG. 15 is a block diagram of the automatic focusing device showing the inside of the microphone computer by component based on the chart. It is a figure for explaining. 1...Subject 4.14...Light emitting element ■...Focus information detection device 5.15...Lens for condensing light (optical system for condensing light) 6.16
@... Optical sensor patent applicant Olympus Optical Industry Co., Ltd. Agent Fuji
Kawa Shichibema 13th ward%14 map

Claims (1)

[Claims] A light-emitting element that emits light toward a subject, a condensing optical system that focuses the light emitted by the light-emitting element, and a distance between the light-emitting element and the condensing optical system that is variable. A light focusing state variable means for changing the focusing state on a subject by varying the distance position at which light is focused by the light focusing optical system; A light sensor emits a photoelectric conversion output corresponding to the amount of light, and a maximum value is detected from the photoelectric conversion output of this optical sensor, the timing of the same maximum value is determined, and from this timing, the focus is adjusted according to the distance RK of the subject. A focus information detection device comprising: focus information signal detection means for obtaining an information signal.