JP2741971B2 - Electronic still camera ranging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for an electronic still camera, and more particularly to an improvement in a distance measuring device for an active electronic still camera which projects distance measuring light.

[0002]

2. Description of the Related Art In an electronic still camera, a subject image formed by an image pickup lens is converted into an electric signal by a solid-state image pickup device such as a CCD and recorded on a video floppy or the like. Such an electronic still camera has a built-in autofocus device, and can perform in-focus imaging. The autofocus device emits distance measuring light to the subject, receives the reflected light with the light receiving element, and determines the lens setting position based on the principle of triangulation. There is a focus detection method in which focusing is performed using natural light passing through an imaging lens, such as a phase difference method.

In this projection type triangulation method, the distance to the subject can be known, and the focusing can be performed quickly, and the focusing can be performed on a low-contrast subject and a low-luminance subject. This is the main focus of the autofocus device. By the way, in the projection type triangulation method, since the light receiving element receives reflected light through a lens different from the imaging lens, an error due to parallax occurs in focusing on a short-distance subject. was there. In order to solve such a drawback, an imaging CCD is used for the light receiving element,
The present applicant has proposed an electronic still camera capable of performing highly accurate focusing even on a subject at a short distance. This electronic still camera is disclosed in Japanese Patent Application No. 2-23.
As described in the specification of US Pat. No. 8001, the distance measuring light is projected toward the subject at the time of distance measurement, and the reflected light is used for imaging C.
The light is received by the CD, and the imaging lens is moved to the in-focus position at high speed based on the subject distance calculated from the light receiving position.

[0004]

In the above-mentioned electronic still camera, the distance measuring light is emitted once when measuring the distance, and the light emitting time is equal to the field period of the video signal as shown in FIG. At the same time. By the way, this light emission time is the same as the above C
Since the distance does not coincide with the charge storage time of the CD, an unnecessary distance measuring light is projected by the difference, and there is a problem that the battery is consumed quickly. By the way, if the light projection time is shortened as shown in FIG. 9 in order to solve this problem, a new problem that the S / N ratio is lowered occurs. SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable distance measuring device for an electronic still camera with low power consumption and improved S / N ratio.

[0005]

In order to achieve the above object, in a distance measuring apparatus for an electronic still camera according to the present invention, a drive control unit for arbitrarily controlling a charge accumulation time of a solid-state image pickup device for imaging a subject; A light emission control unit that drives a light emitting unit that emits distance measuring light toward a subject in accordance with the charge accumulation time, a detection circuit that detects a light receiving position of the distance measuring light from the electric signal, and the light receiving position And a calculation unit for calculating the subject distance based on In another aspect of the present invention, in the above configuration, when the detection circuit cannot detect the light receiving position or when the charge level at the detected light receiving position does not reach a certain value, the charge accumulation time is extended to perform distance measurement again. It is.

According to another aspect of the invention, a light projecting unit that emits distance measuring light intermittently toward a subject, and a charge corresponding to an optical image formed by an imaging lens are stored in a storage unit, and a transfer unit is provided. A solid-state imaging device that outputs an electric signal from the light emitting unit, and discharges unnecessary charges accumulated in the accumulation unit when the light emitting unit is turned off, and charges accumulated in the accumulation unit when the light emitting unit emits light. A drive control unit of the solid-state imaging device, which adds each signal component and reads out the added charge after the light emission ends as the electric signal, and a detection circuit that detects a light receiving position of the ranging light from the electric signal, A calculating unit for calculating a subject distance based on the light receiving position.

[0007]

FIG. 5 shows an electronic still camera incorporating a distance measuring apparatus according to the present invention. A camera body 2 has an imaging lens 3, a light emitting window 4 for projecting near-infrared light, and a strobe light. A light emitting section 5, a release button 6, and a liquid crystal panel 7 are provided. A loading port 8 is formed in the front side surface of the camera body 2, and a memory cartridge 9 for recording a video signal is loaded into the loading port 8 from the direction of the arrow in FIG.

As shown in FIG. 2, a light projecting lens 15, a regulating plate 16, and a light emitting diode 17 for emitting near-infrared light are provided behind the light projecting window 4. The near-infrared light from the light emitting diode 17 is shaped into a spot by the regulating plate 16 and then emitted by the light emitting lens 15. This floodlight lens 15
When the spot light is projected on the subject 18a three meters ahead of the lens 3, the optical axis 15a of the optical axis 15a is incident on a point A (reference point) at the center of the solid-state imaging device shown in FIG. Is tilted. For this reason, when this spot light is projected on a subject different from the subject 18a, for example, the subject 18b 3 meters ahead, the spot light is incident on a point B different from the point A. 2 and 3, the base distance between the optical axis 3a and the light emitting diode 17 is H, the distance between the subject 18b and the lens 3 (subject distance) is L, the distance between the reference point A and the point B is Δ, Assuming that the focal length of the lens 3 is f, L = 3 · H · f / (H ·
f−3Δ) holds.

FIG. 4 shows an electrical configuration of the electronic still camera. A half mirror 20 is provided behind the lens 3 at an angle of 45 degrees. Lens 3
The light from the subject 18 that has passed through is divided into two by a half mirror 20, and half of the light is transmitted and imaged on the CCD 19 behind. The CCD 19 converts a subject image into an electric signal and outputs the electric signal. On the front surface of the CCD 19, a filter 22 which is inserted on the optical axis 3a at the time of photographing and cuts infrared light passing through the lens 3 is provided so as to freely enter and exit.
When retreating from the optical axis 3a, it is confirmed by the reflection type position sensor 22a. The half mirror 20
The light reflected by is focused on a focus glass 24 provided on the lower surface of the pentaprism 23. The optical image formed on the focus glass 24 is
Is observed through.

A video signal processing circuit 31 is connected to the CCD 19 via an amplifier 30. The electric signal amplified by the amplifier 30 is converted into a video signal by the video signal processing circuit 31. The video signal processing circuit 31 includes a recording unit 32
And a detection circuit 33 for detecting a light receiving area of the spot light from the video signal. The recording unit 32 is connected to a microcomputer 34 which will be described in detail later. When a write signal is sent, a video signal is written to the memory cartridge 9.

In this light receiving area, more charges are accumulated than in the surroundings due to the spot light reflected by the subject, so that a high charge area protrudes in a rod shape in the video signal as shown in the video signal of FIG. . The detection circuit 33 detects the position of the point B from the position of the high charge area to obtain the distance Δ, and sends distance data corresponding to the distance Δ to the arithmetic unit 35. The calculation unit 35 calculates the subject distance L based on the distance data from the above equation L = 3 · H · f / (H · f−3Δ). Arithmetic unit 35
Is connected to the microcomputer 34, and the subject distance L is sent to the microcomputer 34 as subject distance data.

The microcomputer 34 has a release button 6
, The signal generator 6a for outputting the ranging start signal, the half-press signal and the release signal, respectively, and the driver 40
A drive control unit 41 for controlling the drive of the CCD 19 through the
A light emission control unit 43 for controlling light emission of the light emitting diode 17 via a driver 42, a driver 45 for driving a motor 44 for moving the filter 22 in and out, and a lens drive control for driving a motor 46 for moving the lens 3 via a driver 47. The part 48 and the position sensor 22a are connected to each other.

When a finger or the like touches the release button 6 during the vertical synchronization period T ₀ , a built-in touch sensor (not shown)
Works, and the distance measurement start signal is sent to the microcomputer 34 from the signal generator 6a. The microcomputer 34 sends the distance measurement start signal to the drive control unit 41 and the light emission control unit 43. Drive control unit 4
1, as shown in FIG. 1, the fall of the vertical synchronization period T ₁ of the vertical synchronizing signal of the time width S ₂ unnecessary charge discharging signal CC
Send to D19. While the unnecessary charge discharging signal is being output, vertical removal is performed in which the charge to be photoelectrically converted is discarded from the storage unit to a drain or the like without using a transfer path. For this reason, CC
Charge storage time S ₃ of the vertical synchronization period T ₁ of the D19 becomes from the fall of the unnecessary charge discharging signal until the rise of the vertical synchronizing signal. These charges are transferred to the transfer path to the rise of the vertical synchronizing signal, a read signal is sent to the fall of the vertical synchronizing signal from the drive controller 41, the next vertical synchronization period T ₂ to the amplifier 30 into an electric signal Sent as Moreover, CCD light emission control unit 43 of the vertical synchronization period T ₁
The light emitting diode 17 emits light for S ₃ hours corresponding to the charge accumulation time of 19.

When the object distance data is sent from the calculation unit 35, the microcomputer 34 sends a distance measurement signal corresponding to the data to the lens drive control unit 48, and moves the lens 3 to the in-focus position via the lens drive control unit 48. Move fast. When a release signal is sent from the signal generator 6a in this state, the microcomputer 3
4 performs a well-known high-speed sweeping operation in the immediately following vertical synchronization period via the drive control unit 41, and in the vertical synchronization period after the high-speed sweeping operation, causes the accumulation unit to accumulate charge for imaging in an appropriate exposure time corresponding to the subject luminance. Then, an electric signal is output from the CCD 19. Thereafter, the microcomputer 34 sends an imaging completion signal to the microcomputer 34 by the lens drive control unit 48, and moves the lens 3 to infinity at the initial position. Also, the microcomputer 34 confirms that the filter 22 has been retracted when the power is turned on, and if this has not been retracted,
The motor 44 is driven via the driver 45 and the
2 to the retreat position.

The operation of the electronic still camera configured as described above will be described. When the distance measuring start signal is output from the signal generator 6a in the vertical synchronizing period T _0, the microcomputer 34 sends a drive control unit 41 to the emission of light control unit 43.
Drive control unit 41 CCD19 unnecessary charge discharging signal time width S ₂ with the fall of the vertical synchronization period T ₁ of the vertical synchronizing signal
Sent to, after the vertical vent of the storage section, to accumulate S ₃ hours charge. Further, the light emission control unit 43 of the vertical synchronization period T ₁ C
The light emitting diode 1 corresponds to the charge storage time of CD19.
7 is allowed to emit light for ₃ hours.

When the spot light is projected on the subject 18b shown in FIG. 2, the spot light reflected by the subject 18b becomes
CCD during charge storage drive via lens 3 at infinity
It is incident on point B at 19. The electric signal output from the CCD 19 during the vertical synchronizing period T ₂ is converted to a video signal by the video signal processing circuit 31 and then sent to the detection circuit 33. By the way, in this video signal, the light emission time of the light emitting diode 17 is shortened and the charge accumulation time of the CCD 19 is correspondingly shortened, so that the ratio of the accumulated charge in the spot light receiving area to the surrounding accumulated charge is reduced. Can be kept constant without changing from the conventional one. Therefore, since the accumulated charges in the light receiving region are not buried in the surrounding accumulated charges, the detection circuit 33 can reliably detect the position of the point B of the CCD 19 from the video signal.

When receiving the distance data from the detection circuit 33, the calculation unit 35 calculates the subject distance L corresponding to the distance Δ, and sends the subject distance data to the microcomputer 34. The microcomputer 34 sends a distance measurement signal to the lens drive control unit 48, rotates the motor 46 at high speed, and moves the lens 3 to the in-focus position. Note that while the half-press signal is being output from the signal generator 6a, focus lock is performed, and the lens 3 at the in-focus position is not moved.

Thereafter, the microcomputer 34 drives the motor 44 via the driver 45, and inserts the filter 22 on the optical axis to complete the preparation for imaging. Then, when the release button 6 is pressed and a release signal is output from the signal generator 6a, the microcomputer 34 does not cause the light emitting diode 17 to emit light, and via the drive control unit 41, a well-known High-speed sweeping is performed, and imaging charges are accumulated during the vertical synchronization period after the high-speed sweeping. The charge for imaging is sent as an electric signal to the video signal processing circuit 31 via the amplifier 30 and is converted into a video signal. This video signal is digitized by the recording unit 32 and written into the memory cartridge 9. When the photographing is completed, the microcomputer 34 drives the motor 44 to move the filter 22 to the retracted position, and sends an imaging completion signal to the lens drive control unit 48 to drive the motor 46 to move the lens 3 to the initial position. I do.

In the above embodiment, the lens 3 is moved to infinity at the start of the distance measurement, and the lens 3 is moved out of the lens. The set position of the lens 3 is such that the spot light reflected by the object at the object distance of 3 meters is connected to the reference point A. It may be a position where an image is formed. In this case, when the subject distance is longer than 3 meters, the lens 3 is moved to the infinity side, and when the subject distance is less than 3 meters, the lens 3 is moved to the close distance side.
By doing so, the moving distance of the lens 3 can be reduced,
The time required for focus adjustment can be reduced.

FIG. 6 is a timing chart of an electronic still camera incorporating a distance measuring apparatus according to a second embodiment of the present invention. A vertical synchronization period T ₁ of the immediately after the ranging start signal is generated, the microcomputer 34 causes the light emitting diode 17 to S ₃ hours, and CCD19 on to accumulate charge in response thereto. Electrical signal output to the vertical synchronization period T ₂ from the CCD19 is converted into a video signal by the video signal processing circuit 31. In this video signal, the detection circuit 33
There if the level of stored charge in the light receiving region to be detected does not reach the predetermined value, the light emitting diode 17 in the vertical synchronizing period T ₅
Is emitted for S ₅ hours longer than the S ₃ hours,
The charge in CCD19 by the S ₅ hours storage, and to perform the distance measurement again by increasing the level of accumulated charges in the light receiving region. Therefore, in this embodiment, the detection accuracy of the light receiving region can be improved.

FIG. 7 is a timing chart of an electronic still camera incorporating a distance measuring apparatus according to a third embodiment of the present invention. Light emission control unit 43 in this embodiment is a light emitting diode 17 is intermittently emit light three times and the drive control unit 41 outputs the unnecessary charge discharging signals for three times in the vertical synchronization period T ₁ to intermittently CCD19 Then, the charges accumulated in the accumulation section are vertically removed. Therefore, the storage unit of the CCD19 is intermittently 3 times charges in the vertical synchronizing period T ₁ is accumulated.
These charges are transferred to the transfer unit at the rise of the unnecessary charge discharge signal and at the fall of the vertical synchronization signal. Each charge is added in the transfer unit by a read signal of a vertical synchronization period T _2, is output as an electric signal to the amplifier 30. This electric signal is converted into a video signal by the video signal processing circuit 31 and then used by the detection circuit 33 to detect a light receiving area.

[0022]

As described above in detail, the distance measuring device of the electronic still camera according to the present invention emits distance measuring light without waste according to the charge accumulation time of the solid-state imaging device.
Power consumption at the time of ranging can be saved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a time chart of a distance measuring apparatus of the present invention.

FIG. 2 is an explanatory diagram of triangular ranging performed by an electronic still camera incorporating the ranging device of the present invention.

FIG. 3 is an explanatory diagram showing a light receiving position of distance measuring light incident on a CCD.

FIG. 4 is a diagram showing an electrical configuration of an electronic still camera incorporating the distance measuring device of the present invention.

FIG. 5 is a perspective view showing the appearance of an electronic still camera incorporating the distance measuring device of the present invention.

FIG. 6 is a diagram showing a time chart of the distance measuring apparatus of the second invention.

FIG. 7 is a diagram showing a time chart of the distance measuring apparatus of the third invention.

FIG. 8 is a diagram showing a time chart of a conventional distance measuring apparatus in which the field time and the light projection time are the same.

FIG. 9 is a diagram showing a time chart of a conventional distance measuring device in which the light projection time is shorter than the charge accumulation time.

[Explanation of symbols]

 2 Camera main body 3 Lens 17 Light emitting diode 18, 18a, 18b Subject 19 CCD 34 Microcomputer 33 Detection circuit 35 Operation unit 41 Drive control unit 43 Light emission control unit

Claims (3)

(57) [Claims] 1. A solid-state imaging device for accumulating electric charge corresponding to an optical image formed by an imaging lens and outputting it as an electric signal, and a drive control unit for arbitrarily controlling the electric charge accumulation time of the solid-state imaging device. A light emission control unit that drives a light projection unit that projects distance measurement light toward a subject in accordance with the charge accumulation time;
A detection circuit for detecting a light receiving position of the distance measuring light from the electric signal; and a calculating unit for calculating distance measuring data corresponding to a subject distance based on the light receiving position. Distance device. 2. A solid-state imaging device for accumulating electric charge corresponding to an optical image formed by an imaging lens and outputting it as an electric signal, and a drive control unit for arbitrarily controlling the electric charge accumulation time of the solid-state imaging device. A light emission control unit that drives a light projection unit that projects distance measurement light toward a subject in accordance with the charge accumulation time;
A detecting circuit for detecting a light receiving position of the distance measuring light from the electric signal; and a calculating unit for calculating distance measuring data corresponding to a subject distance based on the light receiving position, wherein the detecting circuit cannot detect the light receiving position In the case where the charge level at the detected light receiving position does not reach a predetermined value, the charge accumulation time is extended and the distance is measured again. 3. A projecting unit for intermittently emitting distance measuring light toward a subject, and accumulating electric charges in an accumulating unit corresponding to an optical image formed by an image pickup lens. The solid-state imaging device to output, and when the light emitting unit is turned off, discharges unnecessary charges accumulated in the accumulation unit, and charges accumulated in the accumulation unit when the light emitting unit emits light are transferred by the transfer unit for each signal component. A drive control unit of the solid-state imaging device configured to read out the added charge as the electric signal after the light emission ends, a detection circuit that detects a light receiving position of the ranging light from the electric signal, A distance calculating device for calculating distance measurement data corresponding to a subject distance based on the distance.