JP3253757B2 - 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 camera distance measuring device, and more particularly to a camera distance measuring device using an active infrared light system.

[0002]

2. Description of the Related Art Conventionally, automatic focusing systems such as cameras are
Broadly speaking, two systems are employed. One is a passive method that measures a distance based on luminance distribution information of a subject, and the other is a method that projects a beam of infrared light, ultrasonic waves, or the like to the subject and measures the distance based on a reflected signal. This is an active method for performing

[0003] Among them, infrared light is projected toward a subject through a light projecting lens, and the semiconductor position detecting device is transmitted from the subject to a semiconductor position detecting device via a light receiving lens provided at a predetermined distance from the light projecting lens, that is, a base line length. An autofocus (hereinafter referred to as A) based on a so-called infrared projection active triangulation method in which reflected light is received and a subject distance is measured based on the incident position.
Since the device can be realized with a simple configuration,
Used in many products.

[0004] However, when taking a picture by this method,
If the main subject does not exist in the projected direction, the AF apparatus focuses on another subject or background, that is, infinity (∞). For this reason, the main subject is out of focus (out-of-focus) photograph (hereinafter, this will be referred to as a hollow hole).

[0005] Therefore, depending on the composition, a subject is put in advance in a distance measuring frame provided in the viewfinder, which indicates the direction of projection of infrared light, and distance measurement is performed. An operation called focus lock was required.

Therefore, a plurality of light emitting signals for distance measurement are used,
Wide-field AF that measures the distance at multiple ranging positions in the viewfinder
Alternatively, a photographic technique called multipoint ranging has been proposed.
As a result, attempts have been made to eliminate complicated operations such as focus lock.

[0007]

However, in the case of an AF camera incorporating an AF device based on an infrared projection active triangulation method using such a multipoint distance measurement technique, the following problems are involved.
Some finite distance measurement time is always required for each distance measurement. Therefore, as the number of the distance measurement points increases for a plurality of distance measurement positions in the image frame, the time required for the distance measurement becomes longer.

Further, the method of projecting infrared light can be relatively easily realized, but has a problem that the accuracy becomes worse as the distance becomes longer due to the S / N relationship between the reflected light and the stationary light. I have. Therefore, it has been considered to increase the number of integration operations performed in synchronization with the pulse emission of infrared light or to increase the integration time to cancel noise components and improve the distance measurement accuracy. However, this also has a problem that the distance measurement time becomes longer accordingly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a camera distance measuring apparatus capable of preventing a distance measuring time from being lengthened and capable of measuring distance with an emphasis on accuracy. With the goal.

[0010]

That is, the present invention provides a light projecting means capable of projecting a pulse light toward a plurality of points within a photographic angle of view , and a light emitted from the light projecting means and reflected by an object. Photoelectric conversion means for receiving the light, and performing photoelectric conversion,
Calculating means for calculating the distance to the object based on the signal obtained by integrating the photoelectric conversion signal from the photoelectric conversion means; and projecting light toward a plurality of points within the shooting angle of view to measure the distance to the object A first distance measurement mode, and a second distance measurement mode for projecting light toward a single point within the shooting angle of view to measure a distance to an object.
Setting means for selecting a distance measurement mode, the setting unit when the second distance measurement mode is selected, the integration time of the number and the arithmetic means of the pulsed light which the light projecting means emits
Number and integration of pulse light in the first ranging mode
And control means for increasing than during, characterized by including the.

[0011]

In the camera distance measuring apparatus according to the present invention, a first distance measuring mode for projecting light toward a plurality of points within a shooting angle of view and measuring a distance to an object is provided. There are two types of distance measurement modes of a second distance measurement mode for projecting light toward a single point and measuring a distance to an object. Then, when pulse light is projected from the light projecting means toward the object toward a plurality of points in the photographing image frame, the light reflected by the object is received by the photoelectric conversion means and photoelectrically converted. Is performed. Based on the signal obtained by integrating the photoelectric conversion signal from the photoelectric conversion means, the distance to the object is calculated by the calculation means. The selection of the first distance measurement mode and the second distance measurement mode is made by the setting means. When the second distance measurement mode is selected, the number of pulsed lights emitted by the light projecting means is determined. And the number of pulsed lights in the first ranging mode and
Than the integration time integration time of said arithmetic means Ru is increased by the control means.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a description will be given of a technique as a premise of a camera distance measuring apparatus according to the present invention. An AF device based on an active triangulation method applied to a compact camera or the like is configured based on a distance measurement principle as shown in FIG. That is, a light projecting lens 1 and a light receiving lens 2 having optical axes parallel to each other are located apart from each other by a base length S, and a near infrared light emitting LED (IRED) is provided on the optical axis of the light projecting lens 1.
3 and a position detecting element (PS) having a length b having an end face at a position shifted by a in the figure on the optical axis of the light receiving lens 2.
D) 4 are arranged respectively. And IRED3
Is reflected by the subject 5 at a distance L through the light projecting lens 1, and is imaged on the PSD 4 through the light receiving lens 2.

The PSD 4 has two output terminals 1ch and 2ch.
When a stationary photocurrent component such as sunlight is removed, the relationship expressed by equation (1) is obtained between the output currents i ₁ and i ₂ and the incident position x of the reflected spot light. To establish. i ₂ / (i ₁ + i ₂ ) = (x + a) / b (1) Then, assuming that the focal length of the light receiving lens 2 is f _j , the incident position x is obtained by Expression (2). x = S · f _j / L (2) Further, Expression (3) is obtained from Expressions (1) and (2).

[0014]

(Equation 1)

Therefore, the reciprocal of the subject distance L can be obtained by obtaining i ₂ / (i ₁ + i ₂ ). FIG. 6 is a main part circuit diagram of a basic distance measuring apparatus based on the active triangulation method. IRED not shown
Before the device emits light, the operational signal A1
1, analog switch AS arranged on the output side of A12
11, AS12 is on. Therefore, due to the negative feedback of the amplifiers A11 and A12, all the stationary photocurrent flowing through the PSD4 flows through the transistors Q11 and Q12. The base potential required for this is charged in the capacitors C11 and C12.

Immediately before the IRED emits light, the analog switch AS1 on the output side of the operational amplifiers A11 and A12.
1. When the AS 12 is turned off, the potentials required for flowing the steady photocurrent are stored in the capacitors C11 and C12.

Next, the increments i ₁ and i ₂ of the photocurrent caused by the reflected light from the object due to the IRED projection flow into the bases of the amplification transistors Q13 and Q14. Now, assuming that the DC current gain of the transistors Q13 and Q14 is β,
β _i1 and β _i2 flow through logarithmic compression diodes Q15 and Q16. The cathode of the logarithmic compression diodes Q15, Q16 is input to the base of the transistor Q19, Q20 constituting the differential amplifier circuit of the constant current I _0.

The collector currents i ₁ 'and i ₂ ' of the transistors Q19 and Q20 and the logarithmic compression diode Q1
Assuming that the reverse saturation current of the transistors Q5 and Q16 and the transistors Q19 and Q20 is I _S and the thermal voltage is V _T , the following relational expressions are established for these transistor diodes.

[0019]

(Equation 2) Therefore, i ₁ × i ₁ ′ = i ₂ × i ₂ ′ (5) By substituting equation (5) into equation (6), equation (7) is established. i ₁ + i ₂ ′ = I ₀ (6)

[0020]

(Equation 3)

On the other hand, the current I _INT for integrating the integration capacitor C13 is equal to i ₁ . Therefore, as shown in FIG. 7, the I _INT by a double integration method charges the capacitor C13 over a given time t _1, then, in the opposite direction constant current I _G
In discharging, when measuring the time t ₂ to return to the original voltage is obtained (8). t ₁ × I _INT = t ₂ × I _G (8) Further, from the above equations (7) and (8), the relation of equation (9) is obtained. i ₂ / (i ₁ + i ₂ ) = ( _IG / I ₀ ) × (t ₂ / t ₁ ) (9) Therefore, the relationship of the expression (10) is established from the expressions (3) and (9). Therefore, the subject distance L can be obtained by measuring t ₂ .

[0022]

(Equation 4) Therefore, an error Δ1 / L of the distance measurement data 1 / L output from the AF circuit generally has a relationship represented by Expression (11).

[0023]

(Equation 5) In the equation (11), n represents the same number of light emission of the IRED, and t _INT represents a signal current integration time of the circuit per one time.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a camera distance measuring apparatus according to the present invention. In the figure, an IRED 12 and a PSD 13 are connected to an AF circuit 11. At a position facing the IRED 12 and the PSD 13, a light projecting lens 14 and a light receiving lens 15 are provided.
They are arranged on parallel optical axes separated by a predetermined base length (S). Note that reference numeral 16 denotes a subject to be measured.

On the other hand, the AF circuit 11 is connected to a control unit 18 together with an adjustment value storage unit 17. This control unit 1
A selection switch (M / S switch) 19 for switching between the multipoint ranging mode and the one-point ranging mode is also connected to the switch 8.

In this configuration, when the pulse light is emitted from the IRED 12, it is projected on the subject 16 via the light projecting lens 14, and the reflected light from the subject 16 reaches the PSD 13 through the light receiving lens 15. This PSD13
Depending on where the reflected light returns, the AF circuit 11 calculates the distance measurement information 1 / L, and outputs it to the control unit 18.

At this time, the ranging accuracy is determined by the I shown in FIG.
The AF accuracy can be improved by increasing the number of times of light emission n of the RED 12 and the value of the integration time t _INT . However, the release time lag becomes longer with this, and this has been a cause of missing a shutter chance.
Therefore, when the M / S switch 19 is turned on and the multi-point ranging mode is selected, the number of times of light emission n and the integration time t are smaller than when the one-point ranging mode is selected.
The value of _INT is read from the adjustment value storage unit 17 and the control unit 1
8 and output to the AF circuit 11.

Next, the specific operation of the above embodiment will be described with reference to the flowcharts of FIGS.
First, a first operation example of the embodiment will be described with reference to a flowchart of FIG.

First, at step S1, it is detected whether or not the M / S switch 19 has been switched to the multipoint ranging mode, that is, whether or not it has been turned on. If the M / S switch 19 is turned on, the process proceeds to step S2, where the integration time T _{INT · M of the} multipoint ranging mode stored in advance in the adjustment value storage unit 17 is equal to the integration time. It is set to _tINT . Then, at step S3, the number of light emissions N _M of the multi-point distance measuring mode is set to the number of emissions n. Thereafter, in step S4, a multi-point AF operation is performed.

On the other hand, if the M / S switch 19 is turned off in step S1, that is, if the one- point distance measurement mode is selected, the process proceeds to step S5, where the adjustment value storage unit 1 is set in advance.
Integration time _{TINT · S of} one-point ranging mode stored in 7
Is set to the integration time t _INT . Then, step S
At 6, the light emitting number N _S of 1 point ranging mode is set to the number of emissions n. Thereafter, in step S7, a one-point AF operation is performed.

When the multi-point or one-point AF operation is completed in steps S4 and S7, the flow advances to step S8 to calculate distance measurement information 1 / L. Next, after the lens is extended in step S9, a shutter operation is performed in step S10. Thus, all the operations are completed.

As described above, according to the first operation example, it is possible to set an independent integration time and the number of times of light emission for each of the multi-point ranging mode and the one-point ranging mode. Next, a second operation example of the embodiment will be described with reference to the flowchart of FIG.

In step S11, first, it is detected whether or not the M / S switch 19 is turned on, that is, whether or not the M / S switch 19 has been switched to the multi-point distance measuring mode. here,
If the M / S switch 19 is turned on, that is, if the multipoint ranging mode is selected, the process proceeds to step S12, where the coefficient m
Is set to “1”. On the other hand, when the M / S switch 19 is off, that is, when the one-point distance measurement mode is selected, the process proceeds to step S13, where the coefficient m is set to "2".

Next, in step S14, the integration time t _INT is set by the following equation. t _INT = m · T _INT (12) The number of times of light emission n is also set in step S15 by the following equation. n = m · N (13) Note that T _INT and N are constants stored in the adjustment value storage unit 17 in advance.

Then, in step S16, the coefficient m
Is set to “1”. Here, if the coefficient m is set to "1", the process proceeds to step S17, where the multipoint AF operation is performed. On the other hand, if the coefficient m is set to "2", the process proceeds to step S18.
The one-point AF operation is performed.

Thereafter, the flow advances to step S19 to calculate distance measurement information 1 / L. Next, after the lens is extended in step S20, a shutter operation is performed in step S21. Thus, all the operations are completed.

As described above, according to the second operation example, the integration time and the light emission time of the one-point distance measurement mode are automatically determined only by setting the integration time and the number of times of light emission only in the multi-point distance measurement mode. it is as possible out to be.

As described above, in the distance measuring apparatus according to the embodiment, when shooting in the one-point ranging mode, the distance measuring accuracy is higher due to a longer integration time or a larger number of flashes than in the multi-point ranging mode. A ranging output can be obtained. In addition, when shooting in the multi-point ranging mode, it is possible to obtain a ranging output with a shorter integration time or a shorter ranging time with a smaller number of flashes than in the one-point ranging mode.

[0039]

As described above, according to the present invention, it is possible to obtain a distance measurement output emphasizing distance measurement accuracy when photographing in the one-point distance measurement mode. In this case, a distance measurement output emphasizing the distance measurement time can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a camera distance measuring apparatus according to the present invention.

FIG. 2 is a time chart showing a light emitting state of pulse light generated from an IRED 12 of FIG.

FIG. 3 is a flowchart illustrating a first operation example of the range finder of the camera in FIG. 1;

4 is a flowchart illustrating a second operation example of the range finder of the camera in FIG. 1;

FIG. 5 is a diagram illustrating a principle of distance measurement of an AF device based on an active triangulation method.

FIG. 6 is a main part circuit diagram of a basic distance measuring device based on an active triangulation method.

FIG. 7 shows the integration time of the double integration method and the capacitor C1.
3 is a diagram showing a relationship between charge and discharge of No. 3. FIG.

[Explanation of symbols]

11: AF (auto focus) circuit, 12: near infrared light emitting LED (IRED), 13: position detecting element (PS)
D), 14: light projecting lens, 15: light receiving lens, 16: subject, 17: adjustment value storage unit, 18: control unit, 19: selection switch (M / S switch).

Continuation of front page (56) References JP-A-61-272725 (JP, A) JP-A-2-158705 (JP, A) JP-A-62-238509 (JP, A) JP-A-62-5112 (JP) JP-A-4-216406 (JP, A) JP-A-4-149530 (JP, A) JP-A-5-52557 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G01C 3/00-3/32 G02B 7/11

Claims (1)

(57) [Claims] 1. A light projecting means capable of projecting pulsed light toward a plurality of points within a shooting angle of view , and a light emitted from the light projecting means and reflected by an object is received to perform photoelectric conversion. Photoelectric conversion means for performing, a calculation means for calculating a distance to the object based on a signal obtained by integrating a photoelectric conversion signal from the photoelectric conversion means, and projecting light toward a plurality of points within the shooting angle of view. Setting means for selecting a first distance measurement mode for performing distance measurement on an object and a second distance measurement mode for projecting light toward a single point within the shooting angle of view and measuring the distance to the object; When, by the setting means when the second distance measurement mode is selected, the light projecting means emits pulsed light number and said arithmetic means in pulsed light integration time to the first distance measurement mode of
Control means for increasing the number of times and the integration time .