JPH0577049B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention measures the distance to a subject by projecting infrared light onto the subject and detecting the intensity of the reflected light. The present invention relates to an autofocus camera equipped with an autofocus device that performs automatic focus adjustment.

Prior Art Various distance measuring devices have been proposed in the past that project infrared light onto a subject and use the received intensity of the reflected light to obtain distance information to the subject. No. 224757 proposes a distance measuring method and a distance measuring device using a received light intensity detection method.

The ranging method and ranging device in this proposal continuously change the projection frequency of infrared light projected onto a target object within a predetermined frequency band, and
A light-receiving signal of the light-receiving section corresponding to the reflected light from the target object is detected through tuning means having a resonance frequency that is a frequency included in the predetermined frequency band. Therefore, it is possible to detect the received light signal by using resonance operation without performing complicated frequency matching between the light emitting side and the light receiving side, and as a result, the light emitting energy on the light emitting side is reduced. for example
This means that even if it is as small as an LED, it can be expected to have the effect of being able to accurately measure distances over long distances.

On the other hand, if we consider the case where the method and device proposed above are applied to a photographic camera,
Since the distance information to the target object is obtained by the above proposal, it is sufficient to match the photographing position of the photographing lens of the camera to be applied with the above distance information. All you have to do is control it. Considering that various means are known for controlling the position of the photographing lens using arbitrary distance information, there is no need to describe it in detail. An autofocus camera that automatically focuses based on this distance information can be easily realized.

Problems to be Solved by the Invention As described above, an autofocus camera equipped with a distance measurement system based on the received light intensity detection method can be easily put into practical use. There is a possibility that the following disadvantages may occur.

In other words, the autofocus camera described above is a system that once obtains distance information and then controls the position of the photographing lens, so it takes time to obtain distance information and time to move the photographic lens to the in-focus position. , is required from the activation of the autofocus system to the start of exposure to the film.

Therefore, if the autofocus system is configured to be activated by operating the shutter release button, which controls the film exposure operation, as in a normal autofocus camera, the two types of times mentioned above will be different. This will act as a delay between the actual exposure start point and the point at which the Tallerise button is operated, and especially in the case of a moving subject as mentioned above, there is a high probability that it will be difficult to perform the exposure operation at the intended timing. This means that you will have fear.

Note that cameras equipped with other distance measurement methods have the above-mentioned delay, but the period is short and it is considered that there is almost no risk of the above-mentioned disadvantages occurring.

However, the distance measurement method proposed earlier is characterized by varying the projection frequency within a predetermined range, which inevitably requires time to obtain the distance information mentioned above. Since there is a risk of causing inconvenience to the subject, improvements are desired.

The present invention has been made in consideration of the above-mentioned disadvantages, and is intended to be used in a camera that obtains distance information using a received light intensity detection method characterized by varying the light projection frequency and automatically performs focusing. Auto has made it possible to extremely shorten the period from the activation of the focus system until the photographic lens moves to the in-focus position, in other words, from the start of the photographing start operation to the start of the actual photographing operation. The purpose is to provide a focus camera.

Means for Solving the Problems The autofocus camera according to the present invention includes a moving ring that rotates to move the photographic lens in the optical axis direction, and a rotating direction that moves the photographic lens from the near point side to the far point side. a biasing means for always biasing the moving ring; a first locking means for locking the movable ring in a state where the photographic lens is positioned at the closest point side against the biasing means; a light projection source that projects infrared light toward the camera; and an oscillation circuit that generates an output signal whose oscillation frequency changes within a predetermined frequency band in response to the movement of the photographic lens; a light projection frequency variable means for controlling the supply of light projection energy to the light source and controlling the light projection frequency of the light projection source according to the movement of the photographing lens; and a light projection frequency variable means that is operated by the first locking means. photographing start means for releasing the locking operation and starting movement of the movable ring by the urging means and operation of the oscillation circuit; light receiving means for receiving reflected light of the infrared light from the target object; a tuning means having an arbitrary frequency included in the predetermined frequency band as a tuning frequency and receiving a light reception signal from the light reception means and amplifying the light reception signal; and a light reception signal level amplified by the said tuning means. a comparison means for performing a reversal operation by comparing the comparison with an arbitrary reference level; a second locking means for locking movement of the movable ring by the urging means in response to the reversal operation of the comparison means; a photographing means that performs a series of photographing operations such as aperture setting and shutter driving in response to the reversing operation of the means; and a photographing means that operates in response to the completion of the operation of the photographing means to move the movable ring against the biasing force of the biasing means. It is configured to include a return means for returning to the locked position by the first locking means and simultaneously releasing the locking by the second locking means.

Effect Since the autofocus camera according to the present invention has the above-mentioned configuration, the photographing lens starts to move from the near point side to the far point side by the shooting start operation, and on the other hand, when it stops, the photographic lens starts moving from the near point side to the far point side. This is carried out when the light reception signal level of the reflected light from the target object exceeds an arbitrary reference level based on the infrared light projection operation whose projection frequency is varied according to the movement. Therefore, the time from the time of operation to start photographing to the time when photographing is actually performed is extremely short.

In addition, regarding the movement stop operation of the photographing lens described above, as will be explained in detail later, the light projection frequency by the light projection means is varied within a predetermined frequency band, and the tuning means is included in the above predetermined frequency band. Since the frequency is the resonant frequency, the level of the received light signal obtained through the light receiving means and the tuning means will vary in its fluctuation characteristics, for example, the rising characteristic or the peak level, depending on the distance to the target object. Then, distance information to the target object can be obtained from the time from the start of light emission until the received light signal level reaches a predetermined level, the period during which the received light signal level exceeds a predetermined level, or the maximum level value of the received light signal level. Therefore, needless to say, the operation corresponds to the distance to the target object, that is, the operation to position the photographing lens at the in-focus position.

Embodiment FIG. 1 is a schematic front view showing the main part of an embodiment of an autofocus camera according to the present invention, that is, the vicinity of the photographing lens. As shown in the schematic top view, it has a cam protrusion 3, and a spring 5 is activated by rotating based on the relationship between the cam protrusion 3 and the control protrusion 4 provided on the photographing lens 1 that is in contact with the cam protrusion 3. A moving ring is provided which moves the photographing lens 1, which is always biased in the direction of arrow A, which is the direction of the photographing position on the nearest point side, against the biasing force of the spring 5, in the direction of the photographing position on the far point side, along the optical axis. It shows.

6 is provided between the protrusion 7 of the movable ring 2 and the camera body (not shown), and the movable ring 2 is always guided by the arrow B.
A spring 8, which is a biasing means for biasing the movable ring 2 in the direction, is normally in a state where it can attract the suction piece 9 provided on the protrusion 7, and by suctioning the movable ring 2, the movable ring 2 is moved against the biasing force of the spring 6. This figure shows an electromagnetic magnet, which is the first locking means, which is locked in the illustrated position and released from the attractable state by being energized.

Reference numeral 10 is provided on the movable ring 2 and constitutes a second locking means together with a spring 12, an electromagnetic magnet 13, and a locking claw 11 whose operation is controlled by these; that is, by engaging with the locking claw 11, A tooth-shaped protrusion that locks the rotation of the movable ring 2 due to the biasing force of the spring 6 is shown.

Note that the electromagnet 13 is normally attached to the locking claw 1.
As shown in the figure, the locking pawl 11 and the toothed protrusion 10 are attracted to each other so as not to engage with the toothed protrusion 10 against the biasing force of a spring 12, and when energized, the above-mentioned attraction is released and the locking pawl 11 and the toothed protrusion 10 are disengaged. Needless to say, it operates so as to cause the engagement to occur.

Reference numeral 14 indicates a regulating protrusion for regulating the maximum amount of rotation of the movable ring 2 by coming into contact with the above-mentioned protruding part 7.

15 is a sliding contact piece that is provided on the movable ring 2 and moves with the rotation of the movable ring 2; 16 is in contact with the sliding contact piece 15 and is connected to the terminal by the movement of the sliding contact piece 15 due to the rotation of the movable ring 2; It goes without saying that the sliding contact piece 15 and the resistor 16 respond to the rotation of the movable ring 2, that is, the resistance increases as the photographing lens 1 moves. It forms a variable resistor VR whose value can be varied.

17 is a gear train provided in the moving ring 2, and 18 is a motor 2 that is driven after a series of photographic operations are completed.
0 through a one-way and slip clutch mechanism 19, and is driven in the direction of arrow D and is fitted with the gear train 17, and is rotated while being fitted with the gear train 17. to move the movable ring 2 against the biasing force of the spring 6 in the direction of arrow C.
It shows a gear that rotates in the direction.

In the following, an electrical circuit for measuring the distance to the target object and controlling the operation of the electromagnetic magnets 8, 13 and the motor 20 will be illustrated, regarding the operation of the main parts of the autofocus camera according to the present invention having the above-described configuration. This will be explained with reference to FIG.

In addition, in FIG. 3, the drawing number 21 is the target object 25.
A light projection source 22 emits infrared light Oscillation circuit 2 that includes VR and controls the operation of the switch element 23
4 shows a light projection frequency variable means for varying the light projection frequency of the light projection source 21. Incidentally, since the movement range of the photographic lens 1 is limited to a predetermined range, needless to say in detail, the above-mentioned variation of the light projection frequency can be done within a desired frequency band by appropriately designing the above-mentioned variable resistor VR. it is obvious.

Reference numeral 27 denotes a switch 28 that is turned on in response to a shooting start operation, for example, a shutter button press operation.
and a switch element 29 that conducts when this switch 28 is turned on and energizes the electromagnetic magnet 8.
30 is a power switch that is turned on when the lens cover is opened, and 31 is a power source.

32 receives the reflected light Y from the target object 25;
A light receiving means outputs a photocurrent corresponding to the received light intensity as a light receiving signal, and a tuning section 34 has a tuning frequency at an arbitrary frequency within a desired frequency band set by the above-mentioned light projection frequency variable means 22. A tuning means is shown which includes an amplification section 35 for amplifying the received light signal obtained via the tuning section 34.

36 is a reference level generating circuit 37 which generates a reference level to be compared with the received light signal level obtained through the tuning means 33, and which compares both levels and lowers its output when the received light signal level exceeds the reference level. A comparator 38 is shown which performs an inversion operation from high level to high level.

Numeral 39 is a switch element which is turned on by the reversal operation of the comparison means 36 and energizes the electromagnetic magnet 13. Numeral 40 similarly starts operation by the reversal operation of the comparison means 36, and performs a series of photographing operations such as setting the aperture and driving the shutter. It shows the means of photography to be carried out.

Reference numeral 41 indicates a switch element which is turned on for a predetermined period of time in the photographing means 40 to energize the motor 20 after a series of photographing operations by the photographing means 40 is completed.

Now, regarding the operation of the schematic configuration shown in FIG. 1 etc., in the case of the autofocus camera according to the present invention, the state shown in FIGS. 1 and 2 is the steady state, that is, the state in which photography can be performed. Needless to say, it is assumed that a photographing operation, that is, a pressing operation of a shutter button (not shown) is performed in the state shown in FIG. 1. At this time, it is assumed that the power switch 30 in FIG. 3 is of course in the on state.

When the shutter button is pressed,
Switch 28 of the photographing start means 27 in FIG.
is turned on and the switch element 29 is turned on, so that the electromagnetic magnet 8 is energized.

Therefore, the suction piece 9 provided on the protrusion 7 of the moving ring 2
The suction operation of is released, and the movable ring 2 begins to rotate in the direction of arrow B due to the biasing force of the spring 6.

When the moving ring 2 begins to rotate, the relationship between the cam protrusion 3 and the control protrusion 4 causes the photographic lens 1 to begin to move from the nearest photographing position to the far photographing position shown in FIG. Together with the sliding contact piece 15 and the resistor 1
The resistance value of the variable resistor VR consisting of 6 is changed.

Therefore, the oscillation circuit 2 of the light projection frequency variable means 22
The oscillation frequency of 4 changes in accordance with the movement of the photographing lens 1, and in response to this change, the switch element 23
As a result, the supply of the constant current source 26 to the light source 21 is controlled, and the light source 21 emits infrared light X modulated onto the target object 25.
will be emitted.

On the other hand, the light receiving means 32 receives the reflected light Y from the target object 25 of the infrared light projection X, outputs a photocurrent proportional to the received light intensity, and supplies it as a light reception signal to the tuning section 34 of the tuning means 33. do.

Therefore, when considering the level of the output signal obtained by the tuning section 34, that is, the received light signal, the modulation frequency of the received light signal increases as it approaches the tuning frequency of the tuning section 34, and becomes the tuning frequency. It has a characteristic that it reaches its maximum level when the frequency is lower than the tuning frequency, and becomes smaller as it moves further away from the tuning frequency.

The light reception signal outputted from the tuning section 34 is then amplified by the amplification section 35 to a level sufficient for signal processing, and is supplied to the next-stage comparison means 36.

Now, let us consider in more detail the light-receiving signal obtained by the amplifying section 35.

The characteristics of the light receiving signal are those obtained by amplifying the light receiving signal output from the tuning section 34, so that the light emitting source 21
Assuming that the light emission frequency of is varied within a predetermined range, the level will decrease after reaching the tuning frequency of the tuning section 34, as described above.For example, if the tuning frequency of the tuning section 34 is F _M , then any distance O
The characteristics for a target object at can be shown as shown in FIG. 4 O'. In Fig. 4, the vertical axis shows the relative intensity of the received light signal level, and the horizontal axis shows time and light emission frequency. Therefore, at time _t0 , the above-mentioned switch 28 is turned on and the light emission frequency starts to be varied. indicates the point in time.

Next, considering the case where the distance to the target object is a distance P that is closer or a distance Q that is greater than the above arbitrary distance O, the characteristics of the above-mentioned light reception signal are shown in Fig. 4, respectively.
The characteristics are as shown by P' and Q'.

From the characteristics shown in FIG. 4, as briefly mentioned above, the light reception signal output by the amplifying section 35 is variable in light projection frequency centered around its peak level or an arbitrary level shown by Z in FIG. The period from the start time t ₀ to the time t ₁ , t ₂ , t ₃ when the above arbitrary level Z is reached, that is, between t ₀ - _{t 1} , t ₀ - t ₂ , t ₀ - t ₃ and the above arbitrary level Z. The period exceeding, i.e., t ₁ ~ t ₆ , t ₂ ~
The characteristics between t ₅ , t ₃ and _{t 4} are the distance to the target object O,
It is clear that this corresponds to P and Q.

Now, in the autofocus camera according to the present invention, as described above, the light reception signal having the above characteristics is supplied to the comparison means 36, and the comparator 38 compares it with an arbitrary reference level output from the reference level generation circuit 37. Therefore, when the received light signal level exceeds the reference level, the comparator 38 performs an inversion operation to change its output terminal from a low level to a high level, and the switch element 39 is turned on to turn on the electromagnetic signal. magnet 1
3 is energized, and the photographing means 40 starts operating.

Incidentally, during the period from when the switch 28 of the photographing start means 27 is turned on until the reversal operation of the comparator 38 is performed, if the above-mentioned reference level is assumed to be the arbitrary level Z explained in FIG. This corresponds to the distance of

Therefore, considering that the fluctuation in the light reception signal level is obtained in response to the movement of the photographic lens 1 as described above, it is necessary to determine in advance the amount of movement of the photographic lens 1, the level fluctuation characteristics of the light reception signal, and the inversion operation of the comparator 38. If the relationship with the level is set appropriately, the taking lens 1 can be positioned at the in-focus position for the target object 25 by stopping the taking lens 1 when the comparator 38 corresponding to the distance is inverted. The autofocus camera according to the present invention is also configured in this way.

That is, when the electromagnetic magnet 13 is energized, the first locking pawl 11 is moved by the magnet 13.
The suction operation that maintains the state shown in the figure is released, and the locking pawl 11 engages with the toothed protrusion 10 provided on the movable ring 2 by the urging force of the spring 12.
Therefore, the movement of the movable ring 2 due to the biasing force of the spring 6 is stopped, and of course the movement of the photographing lens 1, which had been moved by the movement of the movable ring 2, is also stopped.

In other words, the photographing lens 1 in the autofocus camera according to the present invention starts to move from the nearest photographing position to the far photographing position by energizing the electromagnetic magnet 8 based on the photographing start operation, and in response to the movement, The movement is stopped by energizing the electromagnetic magnet 13 based on the light projection/reception operation via the target object to obtain distance information of the infrared light whose projection frequency changes.

Although it was not mentioned in the previous explanation, the reason why the photographing lens 1 is moved from the closest point side photographing position to the far point side photographing position is that in the present invention, the level of the light reception signal as shown in FIG. Of the various distance information obtained from the characteristics, the time signal which becomes longer as the distance from the target object goes from near to far is utilized, and the purpose of this is to move the photographing lens 1 while this time signal is being formed. Nor.

Furthermore, considering the operation of the autofocus camera according to the present invention as described above, the level characteristics of the received light signal, which is the output of the tuning means 33 shown in FIG. Needless to say, since the movement of the photographing lens 1 is stopped and the variation of the light projection frequency is stopped, the light emission frequency remains constant at the above-mentioned predetermined level, and it has a characteristic that it decreases in response to the operation of returning to the initial position after the photographing operation is completed. .

On the other hand, when the photographing lens 1 stops moving, the photographing means 40 also starts operating at the same time, so that a series of photographing operations such as shutter driving are performed.

That is, the photographing operation is performed in synchronization with the stoppage of movement of the photographing lens 1. It goes without saying that the shutter driving operation in the above series of photographing operations is performed after the photographic lens 1 stops moving.

When the series of photographing operations by the photographing means 40 is completed, the photographing means 40 turns on the switch element 41 for a predetermined period of time, energizing the motor 20, and the motor 20 is rotated in a predetermined direction. .

The driving force accompanying the rotation of the motor 20 is transmitted to the gear 18 via the one-way and slip clutch mechanism 19, and attempts to rotate the gear 18 in the direction of arrow D.

The gear 18 is fitted with a gear train 17 provided on the movable ring 2, and therefore the driving force of the motor 20 is further transmitted to the movable ring 2. As a result, the gear 18 and the movable ring 2 are connected to the spring 6, etc. They will rotate in the directions of arrows D and C, respectively, against the biasing force.

When the movable ring 2 rotates in the direction of arrow C, the pressing action of the control protrusion 4 by the cam protrusion 3 disappears, and the photographing lens 1 is moved in the direction of arrow A by the spring 5, and the protrusion 7 is pressed against the electromagnetic magnet 8. The adhesion contact piece 9 is attracted to the electromagnetic magnet 8,
Furthermore, the locking pawl 11 approaches the electromagnetic magnet 13 against the biasing force of the spring 12 due to the peak portion of the tooth-like protrusion 10, and is attracted to this magnet 13.

That is, all the members are returned to the steady state shown in FIG. 1, and the aforementioned switch element 41, motor 20, gear train 17, gear 18,
The clutch mechanism 19 and the peaks of the toothed protrusions 10 can be considered as means for returning each member, and a state ready for the next photographing operation is established.

Note that the electromagnetic magnet 8 is used to attract the attraction piece 9, but as is clear from the previous explanation, it cannot be attracted if the switch 28 is turned on. Needless to say, the motor 20 must be driven when the switch 28 is off.

Similarly, the electromagnetic magnet 13 cannot attract the locking pawl 11 if the switch element 39 is in the ON state, but as the movable ring 2 moves in the direction of arrow C, the received light signal level naturally decreases and the comparator Since the output terminal 38 is at a low level, the switch element 39 is turned off without special consideration, and no particular problem occurs.

The above-mentioned operation is one shooting operation of the autofocus camera according to the present invention, and if we look at the delay period mentioned at the beginning from when the shooting start operation is performed until the actual shooting operation starts. It is clear that this is the period from when the switch 28 of the photographing start means 27 is turned on until the photographing means 40 starts operating, and the light reception obtained by varying the light emission frequency once over a predetermined range. This is an extremely short period of time compared to a method in which the photographing operation is performed after moving the photographing lens based on the peak level of the signal.

Effects of the Invention The autofocus camera according to the present invention has an arbitrary level of a light reception signal based on the intensity of reflected light from a target object from the start of infrared light projection whose light projection frequency is variable within a predetermined frequency band. Taking advantage of the fact that the period until the level is reached corresponds to the distance to the target object, the photographing lens is moved from the nearest shooting position to the farthest shooting position at the start of the shooting operation, and in response to this movement. The light emission frequency of the infrared light emission is varied, and the point in time when the light reception signal level based on the intensity of reflected light from the target object reaches a desired level is detected, and the movement of the photographing lens is stopped, and a series of shutter drive etc. Since the shooting operation is performed, the period from the start of the shooting operation to the start of the actual shooting operation can be extremely shortened, making it possible to shoot at the intended timing even for moving subjects. It has the effect that it can be carried out.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of the vicinity of the photographing lens, which is the main part of an embodiment of an autofocus camera according to the present invention, FIG. 2 is a partial schematic top view of the configuration shown in FIG. 1, and FIG. 1 is an electric circuit diagram for controlling the configuration shown in FIG. 1, and FIG. 4 is a waveform diagram for explaining a light reception signal outputted by the tuning means indicated by number 33 in FIG. 3. 1... Shooting lens, 2... Moving ring, 3... Cam protrusion, 4... Control protrusion, 5, 6, 12... Spring,
7...Protrusion, 8...Electromagnetic magnet, 9...Adsorption piece, 10...Tooth-shaped protrusion, 11...Latching claw, 13...
...Electromagnetic magnet, 14...Regulating protrusion, 15...
Sliding contact piece, 16...Resistor, 17...Gear train, 1
8... Gear, 19... Clutch mechanism, 20... Motor, 21... Light projecting means, 22... Light projecting frequency variable means, 22, 29, 39, 41... Switch element, 24... Oscillation circuit, 25...Target object, 26
...constant current source, 27...imaging start means, 28...
Switch, 30... Power switch, 31... Power supply, 32... Light receiving means, 33... Tuning means, 34
... Tuning section, 35 ... Amplification section, 36 ... Comparison means, 37 ... Reference level generation circuit, 40 ... Photographing means.

Claims (1)

[Claims] 1. A moving ring that rotates to move the photographing lens in the optical axis direction; and urging means that constantly urges the moving ring in the rotational direction that moves the photographing lens from the near point side to the far point side. , a first locking means for locking the movable ring in a state in which the photographing lens is located at the closest photographing position against the urging means; and a light projection source for projecting infrared light toward a target object. and a variable light projection frequency including an oscillation circuit whose oscillation frequency changes within a predetermined frequency band according to the movement of the photographic lens, and which varies the light projection frequency of the light projection source in response to an output signal of the oscillation circuit. means, photographing start means for releasing the locking operation by the first locking means and starting the movement of the movable ring and the frequency variable operation of the oscillation circuit; The light receiving means receives reflected light from a target object and outputs a photocurrent corresponding to the received light intensity as a light receiving signal, and a tuning section having an arbitrary frequency included in the predetermined frequency band as a tuning frequency. tuning means for receiving a signal and amplifying the received light signal; comparison means for comparing the level of the received light signal amplified by the tuning means with an arbitrary reference level and performing an inversion operation; and response to the inversion operation. a second locking means for locking the movement of the movable ring by the urging means; a photographing means for performing a series of photographing operations such as setting an aperture and driving a shutter in response to the reversing operation; operating in response to the completion of the operation of the means to return the movable ring to the locking position by the first locking means against the urging force of the urging means, and at the same time the locking operation by the second locking means; An autofocus camera comprising a return means for releasing the