JP2000147366A - Range-finding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a range-finding device that an effect exerted on a range- finding action such as a focus detecting action by harmful light is eliminated and the AF accuracy of a principal object can be enhanced by changing a prescribed range-finding arithmetic method so that the effect of the harmful light is eliminated when it is judged that the harmful light is included. SOLUTION: By a range-finding means 1, the focusing state of a photographing lens or a distance to the object is detected by the prescribed range-finding arithmetic method and a range-finding signal is outputted. By a harmful light judgement means 2, the existence of the harmful light exerting the adverse effect on the range-finding action is judged based on the output of the range-finding means 1. When it is judged by the judgement means 2 that the harmful light is included, the range-finding means 1 is instructed by a range-finding arithmetic method change means 3 so that the range-finding arithmetic method is changed in order to eliminate the effect of the harmful light. By a control means 4, a focusing control action is executed based on the output of the range-finding means 1. Thus, even when the object of the harmful light exists in the background of the principal object, the effect thereof is eliminated and the AF accuracy is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus which can be applied to a camera which automatically performs focus detection and distance measurement and adjusts the focus of a photographing lens based on the result.

[0002]

2. Description of the Related Art Conventionally, many cameras having a night view shooting mode have been realized, but even without such a night view shooting mode, a beautiful picture can be obtained by fixing the camera to a tripod and using long exposure. You can shoot.

A recent automatic focus (AF) camera can reliably detect the focus of a dark subject such as a night scene. FIG. 19A shows an image in the viewfinder to be photographed.

[0004] A person is standing in the foreground, and the photographer is about to photograph the person as a main subject against a night view. In this scene, the background has a street lamp on the right side of the person and the neon of the background building is on the left side of the person.

[0005] An AF target (distance measuring frame) captures three of these persons, a streetlight, and neon light, and the surroundings are assumed to be dark at night. Generally, when shooting a night scene, the above scene is a common scene.

That is, there is some light source in the distance measuring frame,
The light source is often the light of a window of a building in the background or a street lamp, and it is rare that the inside of the distance measurement frame is completely dark. The same can be said for a case where there is no main subject in front of the user.

That is, it can be said that the light source in night view photographing often becomes a point light source unlike the sun in the daytime.
FIG. 19B shows sensor data obtained by imaging the scene of FIG. 19A with the AF sensor.

[0008] The AF detection system is a known passive phase difference detection system, and the outputs of the left and right sensor arrays are shown. The horizontal axis shows the arrangement order of the previous pixel (assuming 64 elements), and the vertical axis shows the sensor output, which is a drawing drawn by connecting the outputs of adjacent pixels.

As can be seen from FIG. 19B, the image of a street lamp is a point light source for the AF sensor and is very bright, so that the image becomes a thin and steep image. Darker than neon, with less power.

That is, since the difference in brightness is large, the output of the image in the center of the dark portion is crushed. For example, it is known that the sensor output under backlight also becomes such. When focus calculation is performed based on such a sensor output, a photograph in which neither the background nor the person is in focus may be obtained.

The reason for this is that the passive phase difference detection method
In principle, this is due to the following two problems originally possessed. (1) A backlit subject is hard to focus on the center image because the center image is destroyed. (2) When calculation focus is performed based on a steep image (an image like a point light source where an image appears only in a few pixels), the calculation accuracy decreases.

In order to solve the above problems (1) and (2), the following prior arts are known. First, Japanese Patent Publication No. 6-7219 discloses that an AF sensor is arranged at a position slightly offset from an image forming plane of an AF optical system, and a sharp sensor output is hardly generated by producing an optical low-pass effect. The disclosed technology is disclosed.

JP-A-5-264887 discloses a technique in which when a backlight condition is detected, the integration time of the AF sensor is extended so that an image of a dark portion is also output.

That is, as shown in FIG. 19C, this is a technique in which the image of the surrounding streetlight is saturated, but the image of the central person is clearly output and focused on the person.
The integration time in the case of FIG. 19C is several times longer than that in the case of FIG.

Japanese Unexamined Patent Publication No. Hei 7-199039 discloses a technique of emitting AF auxiliary light when a night view mode for shooting a night view is set.
That is, this is a technique of irradiating a foreground person with auxiliary light and clearly outputting an image of the person, thereby focusing on the person.

Further, direct light in the form of a point light source such as a street lamp is
Due to the aberration of the AF optical system, an image having flare may be formed on the AF sensor. In such a situation, if the point light source-like direct light enters the end of the effective light receiving area of the AF sensor, the center of gravity of the image is shifted, resulting in erroneous distance measurement (see FIG. 18).

[0017]

However, the above prior art has the following problems. First, Tokuhei 6-
The technique disclosed in Japanese Patent No. 7219 has an effect on a thin linear object, but has no effect on a point light source such as a streetlight in FIG.

Conversely, it can be said that a point light source such as a streetlight has a very steep image. That is, a technique for reducing the influence of the point light source on the focus detection is required.

In Japanese Unexamined Patent Publication No. Hei 5-264887, since backlight under sunlight is to be detected, FIG.
There is a problem that the sensor output as shown in FIG. 9B cannot be determined to be backlight.

That is, this can be determined to be backlight only when the output on both sides is larger than that at the center. According to Japanese Patent Application Laid-Open No. Hei 7-199039, in the night view mode, the auxiliary light of AF is always emitted, so that not only energy loss occurs, but also unnecessary scenes (the night view mode is used under sunlight, or the There is a problem that the auxiliary light is emitted even in such a night view without harmful light for AF.

It is to be noted that the problem of erroneous distance measurement due to the displacement of the center of gravity of the image when the image having the flare on the AF sensor due to the direct light in the form of a point light source such as a street lamp is incident on the end of the effective light receiving area is solved. A method for doing so has not yet been proposed.

The present invention has been made in view of the above-mentioned problems of the prior art, and removes the influence of harmful light on a distance measuring operation such as focus detection, thereby improving the AF accuracy for a main subject. An object of the present invention is to provide a distance measuring device.

[0023]

According to the present invention, in order to solve the above-mentioned problems, (1) the focus state of the taking lens,
A distance measuring means for detecting a distance to a subject by a predetermined distance calculating method and outputting a distance measuring signal; and a harmful light for judging whether there is harmful light which adversely affects the distance measurement result by the distance measuring means. Light determining means, and control for changing a predetermined distance calculation method by the distance measuring means so as to remove the influence of the harmful light when the harmful light determining means determines that harmful light is included. And a distance measuring device.

According to the present invention, (2) the distance measuring means includes a photoelectric conversion means having a photoelectric conversion element array,
The harmful light determination means detects a position of harmful light on the photoelectric conversion element array, and the control means performs a distance measurement calculation by the distance measuring means based on the harmful light position detected by the harmful light determination means. An area to be set is set (1).
Is provided.

According to the present invention, (3) the distance measuring means includes a photoelectric conversion means having a photoelectric conversion element array for outputting a charge accumulation signal, and the control means controls the harmful light judgment means. When it is determined that the distance measuring means is included, the distance measuring means is controlled so that the area affected by the harmful light from the charge accumulation signal of the photoelectric conversion element array is not used for the distance measuring calculation. The distance measuring device according to (1) is provided.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the concept of a distance measuring device applicable as an automatic focusing device of a camera according to an embodiment of the present invention.

That is, the distance measuring apparatus applicable as the automatic focusing apparatus of the camera according to the first aspect of the present invention detects the focus state of the photographing lens or the distance to the subject by a predetermined distance calculating method. Distance measuring means 1 for outputting a distance measuring signal, and harmful light determining means 2 for judging the presence or absence of harmful light which adversely affects the distance measuring operation based on the output of the distance measuring means 1
If the harmful light determining means 2 determines that harmful light is included, the distance measuring means 1 is instructed to change the distance measuring method so as to remove the influence of the harmful light. It is characterized by comprising distance calculation method changing means 3 and control means 4 for performing focus adjustment control based on the output of the distance measuring means 1.

FIG. 2 is a block diagram showing the overall configuration of a camera to which the automatic focusing apparatus according to the present invention is applied. First, a mechanical configuration and an optical configuration will be described.

In FIG. 2, a light beam from a subject passes through a five-group photographing lens 41 and is incident on a main mirror 42. Here, the taking lens 41 is the first group lens 5
1, a second lens group 52, a third lens group 53, a fourth lens group 54, and a fifth lens group 55;
It is composed of

Then, focusing is performed in the first group lens 51 and the second group lens 52, and at the time of zooming, the third group lens 53 and the fourth group lens 54 are simultaneously moved.
The first group lens 51 and the second group lens 52 are driven by a cam structure to prevent a focus movement during zooming.

The main mirror 42 is a half mirror.
0% is reflected toward the finder optical system 43. On the other hand, the remaining 30% of the amount of light incident on the main mirror 42
Are transmitted through the main mirror 42 and reflected by the sub-mirror 44, and then guided to the AF optical system 45.

The finder optical system 43 includes a screen 61, a condenser lens 62, a prism 63, a mold roof mirror 64, and an eyepiece 65, and is observed by a photographer.

Then, the main mirror 42 and the sub mirror 4
Reference numeral 4 retreats to the position shown by the broken line in the figure when the film is exposed. The subject light beam that has passed through the photographing lens 41 is exposed to the film 72 while the shutter 71 is open.

Further, the AF optical system 45 includes a field stop 8
1, infrared cut filter 82, condenser lens 83,
It is composed of a mirror 84, a re-imaging stop 85 and a re-imaging lens 86, and guides a light beam for focus detection to the AF sensor 15.

Next, the electrical configuration will be described. In FIG. 2, a camera control unit 10 which is a camera control device is shown.
Has a central processing unit CPU11, an interface IC12, and the like, and controls a series of operations of the camera.

The camera control unit 10 includes an exposure control unit 1
3, a film drive unit 14, an AF sensor 15, an aperture drive unit 16, a zoom control unit 17, and an AF lens control unit 1.
8, a photometry unit 19, a flash control unit 20, a switch group 21, and an EEPROM 22 are connected.

The exposure controller 13 includes a main mirror 42
And the shutter 71 is driven to control the exposure of the film 72. Film drive unit 14
Controls the winding and rewinding of the film 72.

The AF sensor 15 has photodiode arrays 15L and 15R, which are photoelectric conversion element arrays, and outputs the output of each element to the camera control unit 10 to perform focus detection.

The aperture driving section 16 drives the aperture 87 in the taking lens 41 to an appropriate aperture value. The zoom controller 17 drives a zoom lens group of the photographing lens 41 by a zoom motor 23.

In this case, the position of the zoom lens group is controlled by an encoder 24 attached to the zoom motor 23. The AF lens control unit 18 drives the focus lens group of the photographing lens 41 by the AF motor 25.

In this case, the position of the focus lens group is
It is controlled by an encoder 26 attached to the AF motor 25. The photometric unit 19 is a sensor including a photodiode that generates an output according to the luminance of the subject, and is installed in the finder optical system 43, for example.

The strobe control unit 20 controls a strobe for emitting flash light to a subject, and in the present invention, uses a strobe light as an auxiliary light, and thus also serves as an auxiliary light control unit.

The switch group 21 is all switches (hereinafter, SW) on the camera pressed by the photographer, and includes a release button (not shown) and a photographing mode switch for setting a night scene mode.

When the night view mode switch is pressed, the camera enters a mode in which an exposure operation suitable for night view shooting is performed. The EEPROM 22 stores various correction data such as AF and photometry. The CPU 11 reads data from the EEPROM 22 when the power of the camera is turned on or at the time of initialization, and expands the data in the RAM in the CPU 11. At the same time, data is read from the EEPROM 22 as needed to make corrections and the like.

FIG. 3 is a diagram showing an internal block configuration of the AF sensor 15. As shown in FIG. In FIG. 3, the AF sensor 15
Are the photodiode arrays 15L and 15R, the pixel amplifier circuit EAC, the shift register SR, and the sensor control circuit S
It is composed of CC.

The photodiode arrays 15L and 15L
R generates an electric charge according to the amount of light incident on each photodiode, and independently outputs the electric charge to the pixel amplifier circuit EAC.

In the pixel amplifier circuit EAC, the charges generated from the photodiodes of the photodiode arrays 15L and 15R are independently amplified, and a voltage signal corresponding to the generated charges is generated.

The pixel amplifier circuit EAC generates a monitor output according to the maximum value of the electric charges generated by each photodiode, that is, the output of the pixel amplifier circuit corresponding to the photodiode having the largest incident light amount. Terminal M
Output to DATA.

The sensor control circuit SCC includes a CPU 11
, The internal operation of the AF sensor 15 is controlled in accordance with the signals (CEN, RES, END, CLK). Further, the shift register SR stores a clock signal C from the CPU 11.
The outputs of the pixel amplifier circuits EAC corresponding to the photodiodes of the photodiode arrays 15L and 15R are sequentially output to the sensor data output terminal SDATA according to LK.

Next, the operation of the CPU 11 and the AF sensor 15 will be described with reference to the timing chart of FIG. First, when the CPU 11 receives the reset signal RES, the sensor control circuit SCC initializes each block in the AF sensor 15 and starts the charge accumulation operation by the photodiode arrays 15L and 15R and the pixel amplifier circuit EAC. Let it.

During this accumulation operation, the pixel amplifier circuit EAC
Monitor output MD according to the charge accumulation level
Output to ATA. The CPU 11 outputs the monitor output MD
ATA is monitored at any time by the built-in AD converter,
When the level reaches an appropriate charge storage amount, an accumulation end signal END is output to the AF sensor 15 to terminate the integration operation.

Next, the CPU 11 sets the read clock CL
When K is output to the AF sensor 15, the shift register SR
Correspond to the photodiode arrays 15L and 15L
The output voltage of the pixel amplifier circuit EAC corresponding to the accumulated charge of the R photodiode is sequentially output to the sensor data output SDATA.

In the CPU 11, the sensor data output S
DATA is sequentially AD-converted by a built-in AD converter and stored in the internal RAM. As will be described later, in the present invention, strobe light is used as AF auxiliary light, and when focus cannot be detected due to low luminance of the subject, the strobe light is pulsed during the integration operation as shown in the figure. And a proper integration amount is obtained.

FIG. 5 is a block diagram showing a detailed configuration of the flash control unit 20 which also serves as auxiliary light. In FIG. 5, a DC / DC converter 90 that boosts the power supply voltage to a voltage at which a strobe can emit light is connected in parallel to a power supply E.

The output of the DC / DC converter 90 is connected to a main capacitor voltage measuring circuit 91 for measuring the voltage charged in the main capacitor MC. The output of the DC / DC converter 90 includes Xe
A (xenon) tube 95 is connected to a trigger circuit 92 for applying a trigger for light emission, and a diode D1.
Main capacitor MC that stores luminous energy through
Is also connected.

The power supply E has a Xe tube 95 that emits light by consuming the energy of the main capacitor MC connected to the cathode of the diode D1, and a light emission amount control circuit 93 that controls the light emission amount of the Xe tube 95. Are connected in series, and a power supply control circuit 94 for controlling the supply of the power E is connected to the light emission amount control circuit 93.

The control of the DC / DC converter 90, the main capacitor voltage measuring circuit 91, the trigger circuit 92, and the light emission amount control circuit 93 is performed by the CPU 11 through the interface IC 12.

FIG. 6 is a flowchart of a main routine showing the operation of the entire camera according to the first embodiment of the present invention. First, when a main switch (not shown) is turned on, C
PU11 is power-on reset and starts operation, and I
Initialization of the / O port, initialization of the RAM, and the like are performed (step S1).

Next, a first release (hereinafter, 1RS)
It is determined whether or not W) is turned on (step S2).
The release SW (not shown) of the camera of the present invention is a general 2
Stage SW, 1R at the first stroke of half-press
When the SW is turned on, the camera performs operations such as AF and lens driving, and a second release switch (hereinafter, 2RSW) is turned on in the second stroke of full press to reach exposure.

If it is determined in step S2 that 1RSW is off, the process proceeds to step S10. On the other hand, if the 1RSW is on, the photometric unit 19 operates to perform photometry of the subject luminance, thereby calculating the aperture value and the shutter speed value that provide an appropriate exposure (step S3).

Then, the subroutine "AF" is executed to detect the focus of the subject. Based on this focus detection, the focusing lens is driven to the in-focus position to focus on the subject (step S4), which will be described later.

Subsequently, as a result of this AF operation, it is determined whether or not focus has been achieved (step S5). However, as will be described later, even when AF is not possible due to low contrast or the like (determined by a detection impossible flag). It is determined that the camera is not in focus.

Here, if it is not focused, step S9
, And cannot shift to the exposure operation until focus is achieved. On the other hand, if it is in focus, it is determined whether or not the 2RSW is turned on (step S6).

If the 2RSW is off, the process returns to step S2. If the 2RSW is on, the exposure operation is controlled by controlling the aperture 87, the main mirror 42, and the shutter 71 based on the result calculated in step S3. Perform (Step S
7).

When the exposure operation is completed, the photographed film 72 is wound and fed to the position of the next frame (step S8), and a series of photographing operations is completed. Then, the display operations of the display devices LCD and LED (not shown) are controlled (step S9), and the process returns to step S2.

In step S10, 1RSW
In response to the operation of any one of the switches other than the 2RSW and the other switches, the state of the other SW is detected, and if not turned on, the process proceeds to step S9.

If any of the SWs is turned on, the process corresponding to the SW is executed (step S11), and then the process proceeds to step S9. FIG.
14 is a flowchart of a subroutine “AF” in FIG.

First, the integration operation of the AF sensor 15 is performed according to the timing chart described with reference to FIG. 4 (step S).
20). After this integration is completed, the sensor data of all pixels is
The data is read into the RAM of U11 (step S21), and the illuminance is corrected (step S22).

This illuminance correction is based on sensor sensitivity variation and A
This is a known technique for correcting a decrease in peripheral light amount of the F optical system.
In step S23, it is determined whether or not a point light source serving as harmful light is included. A specific method of this harmful light determination will be described later.

In step S24, as a result of the harmful light determination,
Referring to the set harmful light flag, if no harmful light is included, the process proceeds to step S26. Also,
If harmful light is included, the position of the harmful light on the AF sensor is stored in step S25.

In step S26, it is determined whether or not the position of the harmful light is within the central block. When the harmful light flag is cleared, that is, when there is no harmful light, or when there is no harmful light in the central block, the process proceeds to step S27 to perform the correlation calculation of the central block.

The central block is a block between the central portions of the left and right sensors shown in FIG. The correlation operation in the central block will also be described later.

On the other hand, if the harmful light is present in the central block in step S26, the flow shifts to step S29, and the central block is not correlated. In step S28, it is determined whether or not the result of the center block correlation operation is undetectable.
If the detection is not possible, the process proceeds to step S29. If the detection is possible, the process proceeds to step S35.

In step S29, it is determined whether or not the harmful light position is in the right block. If the harmful light flag is cleared or if there is no harmful light in the right block, the flow shifts to step S30, where the right block is deleted. Perform correlation calculation.

The right block indicates the right block of the left and right sensors shown in FIG. 19B. As a result of the correlation operation of the right block, if the detection is not possible, the process proceeds to step S32;
Go to 5.

In step 32, it is determined whether or not the position of the harmful light is in the left block. If the harmful light flag is cleared or if there is no harmful light in the left block, the process proceeds to step S33 and the left block is determined. If not, the process proceeds to step S33 to perform a correlation operation on the left block.

The left block is a left block of each of the left and right sensors shown in FIG. 19B. If the harmful light is in the left block, it returns as undetectable in all blocks.

Then, as a result of the left block correlation calculation, it is determined whether or not the focus cannot be detected (step S35). If the focus cannot be detected, all the blocks cannot be detected, and the process returns.

On the other hand, if it can be detected in any of steps S28, S32 and S34, the defocus amount of the photographing lens 41 which is the distance measurement result is calculated in step S35, and the aberration amount of the photographing lens is corrected in step S36. I do.

This aberration correction corrects a difference in the detected defocus amount due to a difference in the focal length of the photographing lens 41. Next, it is determined whether or not the photographing lens 41 is already in focus (step S37).

This determination is for determining whether the detected focus amount is within a predetermined allowable value. And if it is already in focus, there is no need to drive the lens,
Returning, if out of focus, the lens driving amount up to focusing is calculated based on the defocus amount as the distance measurement result (step S38), and the photographing lens 41 is driven to the focusing position (step S38). Step S39).

Steps S35 to S39 are well-known techniques, and are not directly related to the gist of the present invention, and thus description thereof is omitted. As described above, when the harmful light is detected, the correlation calculation of the block containing the harmful light is not performed. Therefore, the correlation calculation is performed only for the image of the object other than the point light source (right block) in FIG. An operation can be performed to focus on a person.

That is, in the central block correlation calculation in step S27, a person image can be detected. Here, referring to FIG. 8, step S27 in FIG.
Will be described.

The sensor data read in step S21 of FIG. 7 is the object image signal L of the left sensor.
(I), it is expressed as a subject image signal R (I) of the right sensor.

First, "5", "37", "5" and "5" are set as initial values for variables SL, SR, Fmin and J, respectively.
8 "(steps S71, S72).
L is a variable that stores the head number of a small block element row for which correlation is detected from the subject image signal L (I), and SR is a small block element for which correlation is detected from the subject image signal R (I). A variable that stores the start number of the column.
Fmin is a variable indicating the minimum correlation value.

J is a variable for counting the number of times small blocks have been shifted in the subject image signal R (I).
Then, the correlation output F (s) is calculated by the following equation.

[0087] In this case, the number of elements of the small block is 27, and the number of elements of this small block is determined by the size of the distance measurement frame displayed on the finder and the magnification of the detection optical system.

Subsequently, the minimum value of the correlation output F (s) is detected. That is, F (s) is compared with Fmin, and if F (s) is smaller than Fmin, Fmin is added to Fmin.
(S) and substitute SL and SR at that time with SL
M and SRM are stored (steps S74 and S7).
5).

Further, SR and J are decremented (step S76), and the correlation calculation is repeated until J = 0 (step S77). That is, the correlation is obtained while fixing the small block position in the image L and shifting the small block position in the image R by one element.

When J = 0, 4 is added to SL and 3 is added to SR, and the correlation calculation is repeated until SL = 29 (steps S78 and S79). That is, the correlation calculation is repeated while shifting the number of elements of the small block in the image L by four elements.

As described above, the correlation calculation can be performed efficiently, and the minimum value of the correlation output can be detected. The position of the small block indicating the minimum value of the correlation output indicates the positional relationship of the image signal having the highest correlation.

The two-image interval SRM-SLM, which is the interval between small blocks at this time, is adopted. Then, in order to determine the correlation of the detected small block image signal having the highest correlation, the correlation outputs FM and FP expressed by the following equations (2) and (3) are calculated (step S80).

[0093] That is, the correlation output is calculated when the subject image R is shifted by ± 1 element from the small block position indicating the minimum correlation output.

At this time, FM, Fmin, and FP are as shown in FIG.
(A) and (b). Note that FIG.
The horizontal axis of (a) and (b) is the position of the photoelectric conversion element (element number from the left end), and the vertical axis is the correlation output.

If the correlation is high, the correlation output F (s)
Becomes So = 0 at the point So, whereas
If the correlation is low, So does not become "0". When the number of photoelectric conversion elements is 64 on one side by performing the above correlation calculation, the correlation calculation is performed over almost the entire area excluding about 5 elements at both ends on the right and left sides.

Subsequently, in order to determine the correlation, the correlation indexes SK and FS represented by the following equations are obtained (step S8).
1). When FM ≧ FP SK = (FP + Fmin) / (FM−Fmin) (4) FS = FM−Fmin (5) When FM <FP SK = (FM + Fmin) / (FP−Fmin) (6) FS = FP−Fmin (7) FIGS. 9A and 9B show only the case where FM ≧ FP.

The correlation index SK becomes SK = 1 when the correlation is high, and the higher the value, the lower the correlation. Further, the correlation index FS corresponds to the contrast of the small block image signal having the highest correlation, so that a larger value indicates a higher contrast.

Therefore, by comparing the values of the correlation indices SK and FS with predetermined values, it is possible to determine whether or not the detected image shift amount is reliable (steps S82 and S83).

If it is determined that the reliability is low in either of steps S82 and S83, an undetectable flag is set (step S84), and the process returns.
If it is determined that the reliability is high in both steps S82 and S83, the undetectable flag is cleared (step S85), and the process returns.

This undetectable flag is determined in step S28 in FIG. If there is reliability as described above, the two-image interval SRM-SLM is adopted. Since the two-image interval SRM-SLM is data on a pixel basis, more detailed two-image interval data ZR is calculated by a known method such as three-point interpolation.

Then, using the two-image interval ZR0 at the time of focusing stored in the EEPROM 22, the image shift amount ΔZR in proportion to the defocus amount near the in-focus state is given by ΔZR = ZR−Z
Find R0.

The subroutine "Right block correlation operation",
The “left block correlation calculation” is the same as the “center block correlation calculation” except for the setting of variables, initial values, and the like, and the basic processing is the same.

FIG. 10 is a conceptual diagram of the harmful light determination in step S23. The sensor data in FIG. 10 is the same as that in FIG. FIG. 10 shows a case where the influence of the harmful light on the focus detection is large.

As described above, the image of a street lamp is a point light source for an AF sensor and is very bright, so it is a thin and steep image. However, the image of a person is darker than a background street lamp or neon. , Output is small.

That is, since the difference in brightness is large, the output of the image in the center of the dark portion is crushed. The width of A and B in the figure is large but the width of C is small, and the width of C is smaller than the pixel pitch. Although it depends, it is about three pixels.

The outputs a and b are small and c is very large. When such sensor data is detected, it is determined that harmful light is present. Next, FIG. 11 shows a flowchart of a subroutine "judgment light determination" of step S23 in FIG.

First, a value that maximizes output among all the pixels and the pixel are searched, and the value is set as Max (step S1).
00). This corresponds to C in FIG.

Then, it is determined whether or not this Max is larger than the first threshold value (step S101). If not, the harmful light flag is cleared (step S110) and the routine returns.

That is, if Max is not large to some extent, it is determined that the light cannot be harmful light. On the other hand, when this Max is larger than the first threshold value,
Find the output of the pixel two pixels ahead of the pixel giving the maximum output,
The output is set as Maxp (step S102).

Further, the output of a pixel two pixels before the pixel giving the maximum output is obtained, and the output is set as Maxm (step S103). Then, it is determined whether or not Max-Maxp is greater than a second threshold value (step S1).
04) If not larger, the process proceeds to step S107, but if larger, it is determined whether Max-Maxm is larger than a second threshold value (step S10).
5) If not large, the process proceeds to step S107.

That is, it is detected that the sensor data changes sharply in the range of ± 2 pixels, and if the sensor data does not change sharply, it is determined that harmful light is not possible. In step S107, the harmful light flag is cleared, and the process returns.

On the other hand, if Max-Maxp is larger than the second threshold value and Max-Maxm is larger than the second threshold value, the harmful light flag is set (step S106), and the routine returns. .

Next, a second embodiment of the present invention will be described. The structure is the same as that of the above-described first embodiment. FIG. 12 shows a flowchart of a subroutine "AF" according to the second embodiment.

First, in step S181, integral control of the AF sensor 15 is performed. In step S182, the CP
U11 reads the signal accumulated in the AF sensor 15 as sensor data and stores it in the RAM.

In step S183, illuminance correction is performed as in the first embodiment. In step S184, R
The focus detection calculation 1 is performed based on the sensor data stored in the AM.

In step S185, it is determined whether or not the result of the focus detection calculation 1 is not detectable. If the result is detected, the process proceeds to step S186. If not, the process returns.

In step S186, it is determined whether or not the image shift amount ΔZR calculated by the focus detection calculation 1 is within a predetermined range that is larger than the allowable focusing range. If not, the process proceeds to step S188.

This is because the detection accuracy decreases when the image shift amount, that is, the defocus amount is large, so that the harmful light effect removal processing described below is not effective.

Next, in step S187, the presence or absence of harmful light mixed with the main subject is determined from the sensor data of the detection blocks SLM and SRM having the highest correlation, and if there is harmful light, the influence is removed. Perform processing.

The method for removing the harmful light effect will be described later. In step S188, an operation of converting the image shift amount ΔZR finally obtained and obtained by the focus detection operation into a defocus amount is performed.

In step S189, the same aberration correction as in the first embodiment is performed. Then, in a step S190, it is determined whether or not the defocus amount is within the focusing allowable range, and if it is within the focusing range, the process returns.

On the other hand, if the camera is out of focus in step S190, the lens drive amount is calculated based on the focus amount obtained in step S191, and the process proceeds to step S192.
To control the driving of the photographing lens 41 and return.

FIG. 13 shows a method of shifting the detection block on the AF sensor data (subject image signals L (i), R (i)) by the subroutine "focus detection calculation 1" in step S184 of FIG. .

As described above, the detection operation is efficiently performed over the entire area of the subject image signal. Note that the processing by the “focus detection calculation 1” is the same as the “center block correlation calculation” of the first embodiment, and a description thereof will be omitted.

Next, the "harmful light effect removal processing" performed based on the flowchart shown in FIG. 14 will be described. In step S193, the subroutine "judgment light determination" of the first embodiment is applied to the sensor data L (i) in the detection block SLM having the highest correlation by the "focus detection calculation 1".

In step S194, referring to the harmful light flag, if there is harmful light, the process proceeds to step S195, but if there is no harmful light, the process proceeds to step S199 to adopt the result of focus detection calculation 1. To return.

In step S195, a new detection block BL is set based on the detected harmful light position. Here, the setting of the new detection block BL differs depending on the positional relationship between the main subject and the harmful light.

In the case of FIG. 16A, the left end of the harmful light is located at i = a. At this time, the sensor data L
In (i), the final position of the new detection block BL is BLE = a
And the number N of pixels of the detection block BL is set to a−SLM +
Let it be 1.

The head position BLS = SLM. In the case of FIG. 16B, the right end of the harmful light is i = b
It is located in. In the sensor data L (i), the head position BLS of the new detection block BL is set to 1 = b on the right end of the harmful light (BLS = b), and the final position is set to BLE = SLM + 26.

The number of pixels N is SLM + 27−b. In step S196, “focus detection calculation 2” is executed for the new detection block BL. The “focus detection calculation 2” will be described later.

In step S197, it is determined whether or not the detection result in the new detection block BL can be detected. If the detection result can be detected, the result of the focus detection calculation 2 is adopted in step S198.

On the other hand, if detection is impossible, step S19
At 9, the result of the focus detection calculation 1 is adopted. next,
The focus detection calculation 2 is performed according to the flowchart shown in FIG.
Will be described.

In “focus detection calculation 2”, the detection block B
An operation on L is performed. In step S121,
As shown in FIG. 17, sensor data L (i), R (i)
BLS and Xs + BLS + d (Xs is the shift amount at the time of focusing) are input as initial values to variables SL and SR indicating the top of the upper detection block, respectively.

Next, in step S122, the variable J
Is set to the initial value 2 * d. J is the sensor data R
This is a variable for counting the number of shifts of the block in (i).

Next, in step S123, the following calculation of the correlation operation formula (8) is performed. F (s) = Σ | L (SL + i) −R (SR + i) | (i = 0 to N) (8) s = SR−SL Subsequently, to detect the minimum value of the correlation output F (s) ,
In step S124, F (s) is compared with Fmin. If F (s) is smaller than Fmin, Fmin is set to Fmin.
(S) and substitute SL and SR at that time with SL1 and SR
It is stored as 1 (step S125).

Here, Fmin is set to a predetermined initial value in advance. On the other hand, if F (s) is equal to or greater than Fmin in step S124, the process proceeds directly to step S126.

In step S126, SR and J are each decremented, and the next block of sensor data R (i) is specified. In step S127, it is determined whether J = 0.

If J is not 0, the process returns to step S123 to repeat the above calculation. As described above, in steps S123 to S128, the sensor data L
While the block position of (i) is fixed to the BLS, the block position of the sensor data R (i) is changed one pixel at a time J
By performing the rotation, the operation of obtaining the correlation is repeated while changing the shift amount only in the vicinity of the in-focus state in the range of d around the in-focus shift amount xs.

FIG. 17 shows how the position of the detection block BR on the sensor data R (i) is shifted with respect to the detection block BL. When J = 0, step S
At step 128, FM and FP are calculated, and step S129 is performed.
Calculates the reliability indexes FS and SK.

This calculation method is based on the above equations (4) to (7).
Therefore, the description is omitted. Next, in steps S130 and S131, the reliability indexes FS and SK are compared with determination values FSth2 and SKth2,
Determine the reliability.

This judgment value is changed as follows according to the number of pixels of the detection block. Here, as the number of pixels in the detection block is smaller, the correlation output F (s) tends to be smaller. Therefore, when the determination values of the reliability indexes FS and SK are the number N of detected pixels, for example, FSth2 = N / 27 * FSth (9) SKth2 = 27 / N * Skth (10) This is set according to the number of pixels.

If there is no reliability (FS ≦ FSt)
If h2 or SK> SKth2), the process returns as undetectable, but if there is reliability (FS> FSth2 and SK ≦ SKth2), the process proceeds to step S132 to clear the undetectable flag and returns.

At step S133, a detection impossible flag is set, and the routine returns. In the second embodiment, the best correlation block SLM in the sensor data L (i)
Although the harmful light determination is performed only for, the harmful light determination may be performed only for the sensor data R (i), or both results may be considered.

Further, it may be determined whether or not to perform the harmful light determination in consideration of the conditions such as the focal length of the photographing lens and the photographing magnification. Specifically, the determination of the harmful light may be performed only when the focal length at which the harmful light is liable to be mixed is small or the imaging magnification is smaller than a predetermined value.

As described above, according to the present invention, even if there is a harmful light subject in the background of the main subject, the influence of the harmful light is eliminated by performing focus detection calculation by separating the harmful light.
F accuracy can be improved.

In the first and second embodiments, TT
Although the present invention is applied to the focus detection device of the L phase difference method, even if it is applied to the external light type passive distance measuring device, only the defocus amount data is replaced with the distance data, and the same effect can be obtained.

Further, the above processing may be executed only when the night scene mode is selected, and may not be executed when another shooting mode is selected. ADVANTAGE OF THE INVENTION According to the focus adjustment apparatus of this invention, even if there exists harmful light like a streetlight in night scene photography in the range-finding field or the background of the subject, it is possible to eliminate the influence and improve the AF accuracy remarkably. Effects can be obtained.

[0148]

Therefore, as described above, according to the present invention, the influence of harmful light on the distance measuring operation such as focus detection is removed, and the AF accuracy for the main subject can be improved. A distance device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a concept of a distance measuring device applicable as an automatic focusing device of a camera according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing the overall configuration of a camera to which the automatic focusing device of the present invention is applied.

FIG. 3 is a diagram showing an internal block configuration of an AF sensor 15;

FIG. 4 is a timing chart for explaining operations of a CPU 11 and an AF sensor 15;

FIG. 5 is a strobe control unit 2 also serving as an auxiliary light;
FIG. 2 is a block diagram showing a detailed configuration of the 0 ’.

FIG. 6 is a flowchart of a main routine showing an operation of the entire camera according to the first embodiment of the present invention.

FIG. 7 is a flowchart of a subroutine “AF” in step S4.

FIG. 8 is a flowchart for explaining a subroutine “central block correlation calculation” executed in step S27 of FIG. 7;

FIG. 9 shows the relationship among FM, Fmin, and FP. The horizontal axis in FIGS. 9A and 9B indicates the position of the photoelectric conversion element (element number from the left end). The vertical axis indicates the correlation output.

FIG. 10 is a conceptual diagram of a subroutine “harmful light determination” executed in step S23 of FIG. 7;

FIG. 11 is a flowchart of a subroutine “harmful light determination” executed in step S23 of FIG. 7;

FIG. 12 is a flowchart of a subroutine “AF” according to the second embodiment.

FIG. 13 is a diagram showing a method of shifting a detection block on AF sensor data (subject image signals L (i), R (i)) by a subroutine “focus detection calculation 1” in step S184 of FIG. 12; is there.

FIG. 14 is a flowchart for explaining “harmful light effect removal processing”;

FIG. 15 is a flowchart for explaining focus detection calculation 2;

FIG. 16 is a diagram for explaining a specific example in a case where a new detection block BL is set based on a detected harmful light position in accordance with a positional relationship between a main subject and harmful light.

FIG. 17 shows sensor data L (i) and R (i)
A variable SL indicating the head of the position shift of the upper detection block,
BLS, Xs + BLS + d as initial values for SR
FIG. 9 is a diagram illustrating a state where (xs is a shift amount at the time of focusing) is input.

FIG. 18 is a diagram for explaining that when direct light in the form of a point light source enters an end of an effective light receiving area of an AF sensor, an erroneous distance measurement is caused due to a shift in the center of gravity of an image. .

FIG. 19 is a diagram for explaining a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Distance measurement means, 2 ... Harmful light judgment means, 3 ... Distance measurement calculation method change means, 4 ... Control means, 41 ... Photographing lens, 42 ... Main mirror, 43 ... Finder optical system, 44 ... Submirror, 45 ... AF Optical system, 51: first group lens, 52: second group lens, 53: third group lens, 54: fourth group lens, 55: fifth group lens, 87: diaphragm, 61: screen, 62: condenser lens 63, prism, 64, molded roof mirror, 65, eyepiece, 71, shutter, 72, film, 81, field stop, 82, infrared cut filter, 83, condenser lens, 84, mirror, 85, re-imaging Aperture 86 Re-imaging lens 10 Camera control unit 11 Central processing unit (CPU) 12 Interface IC 13 Exposure control unit 14 Fill Drive unit, 15: AF sensor, 16: Aperture drive unit, 17: Zoom control unit, 18: AF lens control unit, 19: Photometry unit, 20: Flash control unit, 21: Switch group, 22: EEPROM, 15L, 15R ... photodiode array, 23 ... zoom motor, 24 ... encoder, 25 ... AF motor, 26 ... encoder, EAC ... pixel amplifier circuit, SR ... shift register, SCC ... sensor control circuit.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoichiro Okumura 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Industrial Co., Ltd. 2F065 AA06 CC00 DD09 DD12 EE05 FF01 FF04 FF05 GG08 JJ25 JJ26 LL04 MM22 NN16 QQ08 QQ12 QQ21 QQ23 QQ25 QQ34 QQ37 QQ38 QQ51 SS03 SS13 2F112 AA08 AA10 AC04 BA06 BA07 BA14 CA02 DA04 DA28 DA40 FA03 FA09 FA12 FA14 FA21 FA38 FA45 2H011 AA01 BA21 BB02 BB03 A02BA05 DA05 DA05

Claims (3)

[Claims] 1. A distance measuring means for detecting a focus state of a photographing lens or a distance to a subject by a predetermined distance calculating method and outputting a distance measuring signal, and adversely affects a distance measurement result by the distance measuring means. Harmful light determining means for determining whether there is an influence of harmful light; and the distance measuring means for removing the influence of the harmful light when the harmful light determining means determines that the harmful light is included. And a control means for changing a predetermined distance calculation method according to the following. 2. The distance measuring means includes a photoelectric conversion means having a photoelectric conversion element array, the harmful light determination means detects a position of harmful light on the photoelectric conversion element array, and the control means comprises: 2. The distance measuring apparatus according to claim 1, wherein an area in which the distance measurement is performed by the distance measuring means is set based on the position of the harmful light detected by the harmful light determination means. 3. The distance measuring means includes photoelectric conversion means having a photoelectric conversion element array for outputting a charge accumulation signal, and the control means determines that the harmful light is included in the harmful light determination means. 2. The distance measuring device according to claim 1, wherein the distance measuring means is controlled so that an area affected by the harmful light from the charge accumulation signal of the photoelectric conversion element array is not used in the distance measuring operation. Distance device.