JPH0476507A - Camera with automatic zooming function - Google Patents

Abstract

PURPOSE:To take a photograph without causing the ratio of a subject in a picture plane to deviate from a set value by predicting the distance to the subject at the time of exposure by measuring the distance to the subject and also detecting the speed of the subject. CONSTITUTION:The camera is provided with a photographic lens (zoom lens) 101, a range finding means 102 which measures the distance to the subject, a speed detecting means 103 which detects the speed of the subject, a focal length varying means 104 which controls the focal length of the lens 101, and a focal length control means 105. Then the distance to the subject at the time of photography is calculated by using the subject distance measured by the means 102 and the speed of the subject detected by the means 103, the focal length with which the ratio of the subject in the picture plane equals the set value is calculated by using the calculated distance to the subject at the time of the exposure, and the means 104 is so controlled that the focal length of the lens 101 reaches the calculation result.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a camera having an auto-zoom function that automatically sets the proportion of a subject in the screen.

[Prior Art] The applicant has already proposed a camera in which the ratio of the subject to the screen is set in advance and the focal length of the zoom lens is automatically set to obtain the set ratio. (Refer to Japanese Patent Application Laid-Open No. 63-220118). This camera calculates the focal length using the calculation means in the camera using the ratio of the subject in the screen input by the photographer using the ratio setting means and the distance to the subject detected by the distance measuring means. The zoom lens is automatically controlled so that the focal length calculated by this calculation is obtained.

FIGS. 9(a) to 9(d) are diagrams for explaining the principle of such a camera. In each figure, 901 is a camera body, 902 is a zoom lens, 903 is a person as a subject, and 904 is a photographic film. Figure 9(a)
- In Figure 9 (C), the distance to the subject is different, but the ratio of the subject to the screen is 7... (1) γ'''', Q
It is expressed as tanθ. Further, as can be seen from FIG. 9(d), when the focal length of the taking lens is fT, the angle of view θ is expressed as tanθ−fT (2). Therefore, by changing the focal length fT, it is possible to keep the ratio γ of the subject within the screen constant. In other words, since d and w can be considered constant, fT can be found by using the measured value of p and the set value of γ to perform the calculation of f・-1−d°7 (3). , the zoom lens should be automatically controlled so that the focal length becomes fT.

According to such a camera, the photographer does not need to perform a zoom operation when photographing, and only needs to track the subject.

[Problems to be Solved by the Invention] However, in the conventional camera having an auto zoom function as described above, if the subject is moving, that is, if the subject is moving between the time when distance measurement is performed and the time when exposure is started, When the distance to the subject changes, there is a problem in that due to this change in distance, the subject is photographed at a ratio different from the preset ratio of the subject in the screen.

FIG. 10(a) is a graph showing an example of a temporal change in the distance to a subject when the subject is moving toward the camera. In FIG. 10(a), the timing when the photographer releases the camera (timing when setting the ratio γ of the subject in the frame) is set to to, and the camera measures distance (
The timing for measuring the distance g to the subject is tl.
, when the timing of exposure is t2, the value of the distance g to the subject changes from 1o to 12 from the time γ is set until the exposure is performed. here,
If the ratio of the subject set by the photographer in the screen is 70, and the ratio of the subject at the time of exposure to the screen is 72, then the following equation is obtained. This γ. A comparison of γ2 and γ2 is shown in FIGS. 10(b) and 10(c). Applying specific values, Δt and +Δt2 are 500 msec.

If the moving speed of the subject is 4 m/sec and flo is 4 m, l12 will be 2 m, and therefore γ2-2γo1
That is, the ratio of the subject in the screen in the photographed photograph (see FIG. 10(b)) is twice the ratio (set value) intended by the photographer (see FIG. 10(c)).

Such a problem becomes noticeable when the moving speed of the subject is high or when the time difference between the time when distance measurement is performed and the time when exposure is started is large.

One possible method for solving this problem is to reduce the time difference between the time when distance measurement is performed and the time when exposure is started. However, there is a limit to reducing the time required to execute the distance measurement sequence and the time required to calculate the focal length, and the time required to extend the zoom lens is generally limited by controlling the amount of extension with high precision. The more you try to do this, the longer it will take. Therefore, it is difficult to reduce the time difference between the time when distance measurement is performed and the time when exposure is started.

The present invention was tried in view of the problems of the prior art as explained above, and even if the distance to the subject changes between the time when distance measurement is performed and the time when exposure is started, An object of the present invention is to provide a camera having an auto-zoom function, which allows the proportion of the image to be occupied within the screen to match a set value.

[Means for Solving the Problems] A camera having an auto zoom function of the present invention includes a distance measuring means for measuring the distance to a subject, a speed detecting means for detecting the speed of the subject, and a focal length of a photographing lens. a focal length variable means for changing the focal length, and a means for predicting the subject distance at a predetermined time based on the subject distance and the speed of the subject, and adjusting the subject so that the proportion of the subject in the screen becomes a predetermined value based on the predicted subject distance. and a focal length control means for controlling a focal length variable means of the photographing lens.

[Operation] The camera with the auto-zoom function of the present invention measures the distance to the subject and detects the velocity of the subject, and this enables the camera to measure the distance to the subject and detect the velocity of the subject. Since we decided to predict the distance to the subject and use this distance to calculate the focal length, the distance to the subject changed between the time when distance measurement was performed and the time when exposure started. Even in the case where the subject occupies the screen, it is possible to maintain the ratio that the subject occupies within the screen as the set value.

[Example 1] First, the configuration of a camera having an auto-zoom function according to the present invention will be schematically explained using FIG.

In Figure 1, 101 is a photographing lens (zoom lens)
, 102 is a distance measuring means for measuring the distance to the subject, 10
Reference numeral 3 indicates a speed detection means for detecting the speed of the subject, and reference numeral 104 indicates a focal length variable means for controlling the focal length of the photographic lens 101. Further, 105 is a focal length control means, and the object distance measured by the distance measuring means 102 and the speed detecting means 103
Calculate the distance to the subject at the time of exposure using the speed of the subject detected by The focal length variable means 1
04.

Next, one embodiment of the camera having an auto-zoom function shown in FIG. 1 will be described.

FIG. 2 is a block diagram schematically showing the configuration of a camera having an auto-zoom function according to this embodiment.

In the figure, 201 is a zoom lens, and there is a lens drive motor (not shown) inside to drive each lens.
have. Further, 202 is a distance measuring section, and 203 is a speed detecting section, which correspond to the distance measuring means 102 and the speed detecting means 103 in FIG. 1, respectively. 204 is focal length variable means 1
04, which drives the lens drive motor. 205 is a CPU as the focal length control means 105, and 206 is a release switch.

In this embodiment, the ratio of the subject to the screen is set by the photographer using the release switch 206. That is, it is assumed that the ratio that the subject occupies within the screen when the photographer turns on the release switch 206 is the set value of this ratio.

Hereinafter, the main components of the camera having an auto-zoom function according to this embodiment will be explained in detail.

First, the CPU 205 will be explained.

In this embodiment, the CPU 205 first calculates the distance Do to the object when setting the ratio of the object to the screen and the distance 12 to the object during exposure, and then calculates the calculated distances 11o and 12. Use this to calculate the focal length.

In order to make the ratio of the subject occupying the screen at the time of shooting as set by the photographer, f in the above equation (5) should be changed to f
What is necessary is to replace it with T2 and set this fT2 so that it holds true. Here, from this equation (6), the following relationship holds true. Therefore, Ilo and 12 must be determined in order to set the proportion of the subject within the screen as set by the photographer. However, what is measured by the distance measuring unit 202 is the distance g1 to the subject at time t1 shown in FIG. 10(a). Therefore, CPU205
Using the moving speed V of the subject detected by the speed detection unit 203, Ro”11+V・Δt1−(8)1
2-11-v-Δt2-(9) is performed to find Do and p2.

Next, the CPU 205 executes fT, which has been set in advance.
By substituting and Do-12 into the above (7), the focal length setting value fT2 is obtained.

Thereafter, the CPU 205 controls the motor drive circuit 204 to set the focal length of the zoom lens 201 to fT2.

FIG. 3 shows the processing algorithm of the CPU 205.

First, it is checked whether the release switch 206 is turned on (5T301), and when the release switch 206 is turned on, the value of the timer in the CPU 205 is set to "0" (ST302), and time counting is started (S7303).
).

Next, distance measurement is performed by the distance measurement unit 202 (ST304).
, the timer value at this time is taken in as the above-mentioned Δt1 (ST305).

Next, the current focal length fT is detected (5T306), and then the moving speed V of the subject is detected (ST307). After that, calculate the distance 11° and 12 to the subject.5T3
08,5T309), and further calculates the focal length fT2 (ST310).

Next, the motor drive circuit 204 is controlled to set the focal length of the zoom lens 210 to fT2.

First, compare the focal length f(2) with the limit fTT on the telephoto side of the focal length that the zoom lens 201 can set.5T311
), if fT2>fTT, set the focal length to f
TT (ST312) and a warning is issued to the photographer (ST313). On the other hand, if fT2≦fTT, the focal length fT2 is compared with the wide-angle limit fTW of the focal length that can be set by the zoom lens 201 (ST31
4). At this time, if ft2<fTw, the set value of the focal length is set to fTW (ST315), and a warning is issued to the photographer (ST316). Next, the motor drive circuit 204 is controlled to perform zooming of the zoom lens 201 (ST317), and to perform a focusing operation in consideration of the movement of the focus position due to the zooming (ST318). Here, the time lag from distance measurement to exposure differs depending on the amount of lens extension when performing the focusing operation, so this time lag is Δt2
(that is, the value indicated by the timer is Δt1+
After waiting (until Δt2) (ST319), exposure is performed (ST320).

Next, the distance measuring section 202 will be explained.

In this embodiment, a so-called active triangulation method was used as the distance measurement method. FIG. 4 is a schematic diagram showing the configuration of the nJ distance section 202. In the figure, 401 is a light projecting lens, 402 is a light receiving lens, 403 is an infrared light emitting diode (IRED), and 404 is a light receiving element (PSD). Note that the light-receiving lens 402 and the light-receiving element 404 are arranged such that the distance therebetween matches the focal length of the light-receiving lens 402. 405 and 405' are objects for distance measurement.

A part of the light emitted by the infrared light emitting diode 403 is projected onto the subject via the light projection lens 401 and onto the subject 405 . A part of the light projected onto the subject 405 is reflected by the subject 405 and is reflected by the light receiving lens 402.
An image is formed on the surface of the light receiving element 404. Here, subject 4
Considering the distance g to 05, the image formation position on the surface of the light receiving element 404 is
Since the distance between principal points (baseline length) of 02 is S, and the focal length of the light receiving lens 402 is f, the following holds true. Note that, as shown in FIG. 4, the starting point of the imaging position This is the intersection of the straight line and the light receiving element 404.

Further, the current 1°/2 outputted by the light receiving element 404 can be expressed as a function of the imaging position X by the following equation.

a+X 11- Ipφ...(1
1) tpIFφ Note that t= is the total signal photocurrent, tp is the total length of the light receiving element 404, and a is the distance between the starting point of the imaging position X and the end of the light receiving element 404 on the infrared light emitting diode 403 side.

Here, from equations (10) to (12), 11a + x 11+12 tp holds true. By using this equation (13), the current 1. , I2 to the subject 305 can be determined.

Next, the speed detection section 203 will be explained.

In this embodiment, the speed is detected using the amount of change in the distance to the subject measured by the distance measuring section 202.

FIG. 5(a) is a graph showing an example of a temporal change in the distance to a moving subject. In the figure, the vertical axis indicates the distance g to the subject, and the horizontal axis indicates the time t. Also, the fifth
Figure (b) shows the distance measurement unit 202 (and speed detection unit 203)
This is a time chart showing the operation timing of the horizontal axis t.
corresponds to the horizontal axis t in FIG. 5(a). Figure 5(a)
As can be seen from FIG. 5(b), distance measurement is performed multiple times at every minute time Δt. The speed detection unit 203 is
This distance measurement result is input and integration is performed over a minute time τ. The result of such integration is shown in FIG. 5(c). As shown in FIG. 5(c), this integration is performed in the positive direction during odd-numbered integrations, and in the negative direction during even-numbered integrations. Therefore, each integral value corresponds to the difference between the distance to the subject during the previous integration and the distance to the subject during the current integration, that is, the movement amount Δp of the subject. Here, the time interval between the previous integration and the current integration is Δ
t, so if the moving speed of the subject is V, the moving amount of the subject is given by Δl-v·Δt (14).

Since Δt is a constant, the velocity can be obtained from each of the above integral values.

FIG. 6 shows an example of a specific configuration of the speed detection section 203.

The current 11 input from the distance measuring section 202 is sent to the preamplifier 60.
1 and compressed by a compression diode 603. Further, the compressed voltage ■A obtained by the compression diode 603 is guided to the differential arithmetic circuit 607 by the buffer 605. Similarly, the current 12 input from the distance measuring section 202
is amplified by a preamplifier 602 and then compressed by a compression diode 60.
The compressed voltage VB obtained by this compression diode 602 is guided to a differential calculation circuit 607 by a buffer 606.

The differential calculation circuit 607 includes a transistor 607a.

607b and a current source 607c. The following relationship holds between the compressed voltage VA, v8 and the currents 1a, Ib guided to the differential arithmetic circuit 607.

Note that s is the reverse saturation current of the compression diodes 601, 601 and the transistors 607a, 607b, and VT is the thermal voltage.

Here, Iφ1-1a + Ib
-(17), so from this and the above equations (15) and (16), it becomes. Substituting the above equation (13) into this equation (18) gives the following equation (19), and it can be seen that the current Ia is proportional to the reciprocal of the distance g to the subject.

Moreover, the current Ic is Ic ---Iφl+Id
...(20) Since it is given by P, the current XX flowing through the compression diode 608 is 1x-1a-1c Since the compression diode generates a voltage based on the power supply side reference, d 11'''' Ix + Id ■φ2 Given. It is given by this formula (22) % formula % (22) and the above formula (17).

On the other hand, a current 1d is passed through the compression diode 611 by a current source 612.

The compressed voltages obtained by compression diodes 608 and 611 are guided to differential arithmetic circuit 614 by buffers 610 and 613, respectively.

The differential arithmetic circuit 614 has the same configuration as the above-described differential arithmetic circuit 607, and includes a transistor 614a.

614b and a current source 614C. The output current 1j of the differential calculation circuit 614 is as follows, and it can be seen that the current 11 is proportional to the distance g to the subject.

Regarding this current 11, as shown in FIG. 5C, the integration is performed in the positive direction during the odd-numbered integration, and the integration is performed in the negative direction during the even-numbered integration. This switching of the integration direction is done by turning on/off the integration switches SWI and SW2.
This is done by switching off.

Switching of the integration switches SWI and SW2 is performed in synchronization with the light emission of the infrared light emitting diode 303. In addition, this switching is such that when the infrared light emitting diode 303 emits an odd number of times (that is, during an odd number of integrations), SWl is on and SW2 is off, and when the infrared light emitting diode 303 emits an even number of times, SWl is off and SW2 is off.
Do this so that W2 is turned on. That is, prior to distance measurement, the reset circuit 618 performs a reset, and first the SW
Infrared light emitting diode 30 with I on and SW2 off
3 to emit light, current l# flows into capacitor 617, and the output voltage at output terminal 619 increases. Next, S
Infrared light emitting diode 3 with WI off and SW2 on
When 03 emits light, transistors 615 and 616
Due to the function of the current mirror circuit composed of
Current 11 flows out of capacitor 617 and flows to output terminal 61
9's output voltage decreases. After that, in the same way, SWI and S
Infrared light emitting diode 30 while switching on/off of W2
By causing the light to emit light, an integral result as shown in FIG. 5(c) described above can be obtained.

Here, the moving speed of the subject is v, the distance to the subject at mll standby is 91, and the distance to the subject at time t is D.
(t), then 11(t)-v-t+471...(2
4). Also, according to the above equation (23), the current II is proportional to the distance g to the subject, so if A is a constant, If-Ai(t) = A (jJ I V-t) = 125>
It can be expressed as

Further, if the above-mentioned positive direction integral value is Voutl and the negative direction integral value is V out2, the output voltage V out of the output terminal 619 with respect to the reference voltage V ref' is V □
ut-V □utl -V out2 -
(2G), and Voutl and Vout2 are given by A 1 τ= where the capacitance of the capacitor 617 is C.
[Jl'+t vt” ko.

C2 = (N 1 τ−□■ τ2 )...
(27) C2 = (ilt(τ + Δ t)−−V (τ+Δ t)2 t1 Δt +vΔt2) ...(28) is given.

Therefore, formula (27) and formula (28) can be transformed into formula (26)
By substituting into the expression (29), the following can be obtained: (D: constant).

In this way, the moving speed (2) of the subject can be easily determined from the output voltage v out of the output terminal 619. Note that the calculation of equation (30) above may be performed within the CPU 205. Also, the distance to the subject is the current 11 described above.
Of course, it can also be obtained by converting into voltage and then A/D conversion.

In this way, with the camera having the auto zoom function of this embodiment, even if the subject is moving, the proportion of the subject within the screen can be maintained at the set value. This effect is particularly effective when distance measurement requires a long time.

Note that in this embodiment, the photographer presses the release switch 206.
Although the setting value of this ratio is the ratio of the subject occupying the screen when the button is turned on, the method of setting the ratio is not limited to this.

For example, the ratio may be set in advance with the first release, and then the exposure etc. may be performed with the second release.

Next, a second embodiment of the camera having an auto-zoom function shown in FIG. 1 will be described.

FIG. 7 is a block diagram schematically showing the configuration of a camera having an auto-zoom function according to this embodiment.

In FIG. 7, components with the same symbols as in FIG. 2 are as follows:
Each shows the same thing as in FIG.

Further, 701 is a CPU, and 702 is a ratio setting means.

In this embodiment, it is assumed that the ratio γ that the subject occupies within the screen is set in advance by the photographer using the ratio setting means 702. Therefore, unlike the first embodiment, it is not necessary to detect the time lag Δt1 from setting γ to distance measurement, the focal length fT at the time of release, and the calculation of the distance Do to the subject at the time of release. That is, γ set by the ratio setting means 702 is detected, and further,
Using the distance g1 to the subject obtained by distance measurement and the moving speed V of the subject, calculate the distance 112 to the subject at the time of exposure using equation (9), and use this 12 to calculate equation (3). By doing this, the actually set focal length fT
2 can be found.

FIG. 8 shows the processing algorithm of the CPU 701.

First, check whether the release switch 206 is turned on (5T801), and when the release switch 206 is turned on, the value of the timer in the CPU 205 is set to "0" (ST802), and time measurement is started (ST80).
B).

Next, distance measurement is performed by the distance measurement unit 202 (ST804).
Next, the moving speed V of the subject is detected (ST80
5) Then, calculate the distance 12 to the subject.
806), γ set by the ratio setting means 702 is fetched (ST807), and focal length fT2 is calculated (ST808).

Next, the motor drive circuit 204 is controlled to set the focal length of the zoom lens 210 to fT2.

First, compare the focal length fT2 with the telephoto side limit fTT of the focal length that the zoom lens 201 can set.S7g09
), lr2 > fTT, the set value of the focal length is set to fTT (ST810), and a warning is issued to the photographer (ST811). On the other hand, if fT2≦fTT, the focal length fT2 is compared with the wide-angle limit fTW of the focal length that can be set by the zoom lens 201 (ST8
12) At this time, if fT2<fTW, the focal length settings are set to f and W (ST813), and a warning is issued to the photographer (ST814). Next, the motor drive circuit 204 is controlled to zoom the zoom lens 201 (ST815), and a focusing operation is performed in consideration of the movement of the focus position due to the zooming (ST816). The value indicated by the timer matches Δt2. After waiting until (jT817), exposure is performed (ST818).

In this way, even with the camera having the auto-zoom function of this embodiment, the proportion of the moving subject within the screen can be adjusted to the set value.

Particularly, when distance measurement requires a long time, a great effect can be obtained.

[Effects of the Invention] As explained in detail above, according to the camera having the auto zoom function of the present invention, even when the subject is moving, the proportion of the subject in the screen will not deviate from the set value. This makes it possible to take pictures without any need.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing the configuration of a camera with an auto-zoom function according to the present invention, and FIG. 2 is a block diagram schematically showing the configuration of a camera with an auto-zoom function according to the first embodiment of the present invention. 3 is a flowchart showing the processing algorithm of the CPU shown in FIG. 2; FIG. 4 is a schematic diagram showing the configuration of the ranging section shown in FIG. 2;
FIG. 5(a) is a graph showing an example of a time change in the distance to the subject, FIG. 5(b) is a time chart showing the operation timing of the distance measuring section and speed detecting section shown in FIG. Figure (C) is a conceptual diagram showing the result of integration performed by the speed detection section shown in FIG. 2; FIG. 6 is an electric circuit diagram showing an example of a specific configuration of the speed detection section shown in FIG. 2; FIG. 7 is a block diagram schematically showing the configuration of a camera having an auto-zoom function according to a second embodiment of the present invention, and FIG. 8 is a flowchart showing an algorithm for the processing of the CPU shown in FIG. Figures 9(a) to 9(d) are conceptual diagrams for explaining the principle of a conventional camera with an auto zoom function, and Figure 10(a) shows an example of a change in distance to a subject over time. 10(b) is a conceptual diagram showing an example of a composition set by a photographer in a conventional camera with an auto zoom function, and FIG. 10(c) is a conceptual diagram showing an example of a composition set by a photographer in a camera with a conventional auto zoom function.
FIG. 3 is a diagram showing an example of a photograph actually taken when the composition shown in FIG. 101...Photographing lens, 102...Distance measuring means, 10
3- Speed detection means, 104 Focal length variable means, 105 Focal length control means, 201 Zoom lens, 202 Ranging section, 203 Speed detection section 204 ...Motor drive circuit, 205...CPU. 206...Release switch, 701...CPU. 702...Ratio setting means.

Claims (1)

[Scope of Claims] Distance measuring means for measuring the distance to a subject; speed detecting means for detecting the speed of the subject; focal length variable means for changing the focal length of a photographic lens; and the subject distance and the subject. a focal length control means for predicting a subject distance at a predetermined time based on the speed of the photographing lens, and controlling the focal length variable means of the photographing lens so that the ratio of the subject to the screen becomes a predetermined value based on the predicted subject distance; A camera having an auto-zoom function, comprising: