JPH0238933B2 - JIDOSHOTENKENSHUTSUSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an automatic focus detection device in an optical device such as a camera.

(Prior art) Conventionally, automatic focus detection devices have a baseline long-distance meter type focus detection optical system and detect the focus position by moving a mirror and using a double image matching method, or a device that detects the focus position by moving a mirror and using a double image matching method. TTL (Through The
Some cameras have a focus detection optical system of the "Taking Lens" type and detect the focus position using a double image matching method by moving the taking lens or optical element group back and forth. However, these automatic focus detection devices only detect the in-focus position, but cannot measure the amount of deviation of the lens from the in-focus position, in other words, the amount of defocus; it is necessary to move the mirror, photographing lens, and photoelectric element group. It was hot. Furthermore, in Japanese Patent Application Laid-Open No. 54-113334, a desired distance range is selected from the entire distance range in which the imaging lens can image an object on the image plane, and the imaging lens or light receiving element is selected. While moving, a reproduction section including an imaging lens and a light receiving element detects the contrast of the object image, and from the output signal of this reproduction section, the focal position of the imaging lens is detected within the distance range selected by the distance range selection section. An automatic focus detection device is described. In this automatic focus detection device, an arbitrary distance range with respect to a three-dimensional object can be selected by the distance range selection section, and the in-focus position of the imaging lens can be detected within that distance range. However, since the focusing position of the imaging lens is detected by detecting the contrast of the object image while moving the imaging lens or the light receiving element, it is possible to focus multiple images on a three-dimensional object without moving the imaging lens or the light receiving element. The focal position cannot be detected, and the imaging lens or light receiving element must be moved to detect the focal position within the distance range selected by the distance range selection section.

(Purpose) The purpose of the present invention is to eliminate the need to move lenses, etc.
Another object of the present invention is to provide an automatic focus detection device that is capable of detecting a plurality of differential focus amounts for a three-dimensional object according to its far and near distribution, and arbitrarily selecting one of the differential focus amounts.

(Structure) The present invention will be described below by giving examples and referring to the drawings.

FIG. 1 shows an example of a TTL focus detection optical system using exit pupil division of a photographing lens in a camera.

Condenser lens 11, minute lens group 12
The exit pupil 14 of the photographing lens 13 is divided by a pupil division optical system consisting of a part 14A of the exit pupil 14,
The image-forming light beam of the photographic lens 13 passing through 14B is incident on the minute photoelectric elements A ₁ to An of the A group and the minute photoelectric elements B ₁ to Bn of the B group. These photoelectric elements are paired with A ₁ and B ₁ , A ₂ and B ₂ . . . An and Bn, respectively, and the two photoelectric elements in the pair receive light rays incident on the same location on the focus detection surface. Of these, the imaging effect rays that pass through portions 14A and 14B of the exit pupil 14 enter correspondingly.

FIG. 2 shows another example of a TTL focus detection optical system using exit pupil division of the photographic lens.

In this example, the image-forming light beam that has passed through a part 14A of the exit pupil 14 passes through the half mirror 15 and the prism 1.
6. The imaging action light ray enters the photoelectric elements A ₁ to An through the imaging lens 17 and passes through a part 14B of the exit pupil 14, is reflected by the half mirror 15, and passes through the prism 18 and the imaging lens 19. Photoelectric element B ₁ ~
Incident to Bn.

FIG. 3 shows an example of a baseline long distance meter type focus detection optical system.

The light rays from the subject are incident on the photoelectric elements A ₁ to An through the mirror 20, the lens 21, and the prism 22, and the light rays from the subject are incident on the photoelectric elements _B1 to Bn through the mirror 23, the lens 24, and the prism 22. do.

For the photoelectric elements A ₁ to Az and B ₁ to Bn, a photodiode array, CCD, BBD, or the like is used.

Focus is reached when the double images match when the phase shift j' of the patterns formed from the outputs of the photoelectric element groups A ₁ -An, B ₁ -Bn becomes 0. Assuming that the focal point is now at a certain position and the pattern is as shown in FIG. 4, the amount of defocus e can be determined by detecting the phase shift j' of the pattern. j′ is the fourth value in the case of a two-dimensional (plane) object.
As shown in Figure 4, only one value is taken, but in the case of a two-dimensional (stereoscopic) object, multiple values _j1 ' and _j2 ' are taken as shown in Figure 4b.

In the TTL focus detection optical system, the relationship between j' and e is e∝j'/2θ _F =j'×F (D=f/F≒2θ _F ×f). However, F is the distance measurement F value, D is the distance measurement exit pupil effective diameter, and f is the photographing lens 1 as shown in Figure 5.
3 focal length, 2θ _F is the exit pupil 14A from the focus position,
This is the angle when looking at 14B. The differential focus amount e is the distance from the focus plane P to the focus detection plane PD,
As shown in Figure 5, F is changed by switching the distance measurement F value mode.
When the value changes from F ₁ to F ₂ , it is necessary to correct the relationship between j' and e by multiplying j' by F ₂ /F ₁ , for example, to make the relationship between j' and e constant. In addition, in the baseline long distance meter type focusing optical system, if the reference length is L, then e∝j'/L.

When the focus is at an arbitrary position, the photoelectric element group A ₁ ~
To obtain j' from the outputs of An, B ₁ to Bn, the outputs a ₁ of the photoelectric elements A ₁ to An of group A and the photoelectric elements B ₁ to Bn of group B
~an, b ₁ ~bn may be stored in a set of memories as a number sequence, and the degree of correlation between them may be tested by shifting one number sequence relative to the other number sequence. To test the degree of correlation between these, use the formula Y = Σ
(ai−bi) ^q or Y lo = Σ{(ai−bi+1) ^p −(ai+1
−bi) ^p } can be used. However, P=1,
2, 3..., and when P is an odd number, Y = Σ|ai−
bi｜ ^q or Y lo = Σ｛｜ai−bi+1｜ ^p −｜ai+1−
Let bi｜ ^p }. Photoelectric element group A ₁ ~ shown in FIG.
The correlation degrees of the outputs of An, B ₁ to Bn are calculated using the above calculation formula, and the results Ya and Yb are shown in FIG. Figure 6a,
6b shows the calculation results for a two-dimensional object [FIG. 4a], and FIGS. 6c and d show the calculation results for a three-dimensional object [FIG. 4b]. 3
In the case of a dimensional object, multiple j′ occur due to the distance composition of the object, but according to the calculation result YA, all of them can be detected, and according to the calculation result YB, the intermediate j' can be detected depending on the ratio of the object perspective distribution. Can detect location.

FIG. 7 shows an electrical circuit in one embodiment of the invention.

In this embodiment, _the focus _detection optical system shown in FIG.
It is made up of. The CCD 25 is driven by the control circuit 26 and the photoelectric element groups _A1 to An,
Each incident light is photoelectrically converted and integrated by the photosensor group 27 corresponding to _B1 to Bn, and then sent to the shift register 2 in parallel.
8 and output in series. The output signals a ₁ -an, b ₁ -bn of the CCD 25 are converted into digital signals by the A/D converter 29 and stored in the memories 30 and 31. In this case, the memory 30 contains the signals of group A.
a ₁ to an are stored, and at the same time, signals b ₁ to bn of group B are stored in the memory 31. The output signal of memory 30 is transferred to memory 32 and then to memory 33. The output signal of the memory 31 is shifted by the shift circuit 34 from the output signal of the memory 30, transferred to the memory 35, and further transferred to the memory 36. Memories 30 to 33, 35, and 36 synchronously transfer signals, and memories 32, 33, 35, and 36
It has a word structure. Therefore, if the signal in the memory 33 is ai, the contents of the memory 32 will be ai+1, and the contents of the memories 35 and 36 will be bi+1-j, bi-
becomes j. Here, j is the shift amount of the shift circuit 34. The difference between the output signals of the memories 33 and 36 is taken by a differential circuit 37, and the output signal is sent to a power circuit 38.
By raising the value to the q power and integrating it in the integration circuit 39, the calculation Yi=Σ(ai-bi-j) ^q can be performed.
This calculation is repeated for each shift amount j, and the control circuit 26 sequentially changes the shift amount j. The peak detection circuit 40 is the integration path 3
The values Yj(min)-1, Yj(min), Yj(min)+1 near the peak value of the output signal of No. 9 as shown in FIG. )+1
Detect. On the other hand, a differential circuit 41 calculates the difference between the output signals of the memories 33 and 35, and the output is raised to the pth power by a power circuit 42. Further, the difference between the output signals of the memories 32 and 36 is taken by a differential circuit 43, and the output is raised to the power of a power circuit 44p and then sent to the power circuit 4 by a differential circuit 45.
The difference between the two outputs is taken. Then, the output of this differential circuit 45 is integrated by an integration circuit 46, and Ylo=Σ
The following calculation is performed: {(ai−bi+1−j) ^p −(ai+1bi−j) ^p }. This calculation is repeated for each shift amount j. The zero cross detection circuit 47 detects the values Yj ₁ ', Yj ₂ ' near zero of the output signal of the integration circuit 46 as shown in FIG. 6b, and the corresponding shift amounts j ₁ and j ₂ . The j′ arithmetic circuit 48 calculates the output of the peak value detection circuit 40 (j(min)−1, Yj
(min)−1), (j(min), Yj(min)), (j(min)
)
+1, Yj (min) +1 is approximated by these 2
The next curve Y=Cj ₂ +Dj+E is determined, and the peak position Yj' and the corresponding value j' of j' (=-D/2C) are calculated, and the output of the zero cross detection circuit 47 (j
, Yj ₁ ′) (j ro ₂ , Yj ₂ ′), by linear approximation of these, j ′ ro = j ′ ro ₁ = j ro ₁ − j ro ₂ /Yj ₁ ′−Yj ₂
Calculate ×Yj ₁ ′.

j ′ is a plurality of j ₁ ′, j ₂ ′... for a three-dimensional object.
…jn′As the subject becomes more distant, j ₁ ′＞j ₂ ′＞……
By setting j' to a small value such as jn', it is possible to select the smaller or larger value of j' and prioritize the far and near subjects to detect the in-focus position. , and by selecting the minimum value of the values of Yij' by the control circuit 26, j'i with the highest degree of correlation can be selected.
Since j′ b indicates the average position of the near and far subject distribution for a three-dimensional subject, for example, far,
By preparing near and average priority modes and selectively setting one of them in the distance measurement mode setting section 49, the control circuit 26 can select one of them in response to each mode setting signal from the distance measurement mode setting section 49. By selecting j′, it is possible to correspond to any subject. In this case, the control circuit 26 controls j' when the far point mode or the near point mode is set.
Select the smaller value or the larger value of , and when the average emphasis mode is set, select j',
Normally, j' corresponding to the minimum value of Y is selected.

When the peak detection circuit 40 performs peak detection, the direction in which the signals b ₁ to bn are shifted by the shift circuit 34 can be controlled by shifting the signals b ₁ to bn once to determine the slope of the output Y of the integrating circuit 39. Based on this, the circuit 26 can determine the shift direction so as to reduce the amount of shift. However, when shooting a 3D object, Y as shown in Figure 6c.
Since the peak value of A does not become one, it is necessary to shift the entire amount. When the zero-cross detection circuit 47 performs zero-cross detection, even if the signals b ₁ to bn are not shifted (even if j=0), the control circuit 26 can determine the shift direction so that the amount of shift is smaller depending on the sign of Y-ro. can.

When performing distance measurement at a different lens position from the first distance measurement, the necessary shift amount j will not be larger than the previous shift amount, so as long as the photographing lens is moved to the in-focus position in the first distance measurement, the maximum The amount of shift can be determined by the control circuit 26. By determining the shift direction and shift amount in this manner, calculation speed can be increased.

The range OR of the above calculation is as shown in Figure 8, where the signal b ₁ ~
bn is shifted within the range l-n≦j≦k-1, and becomes the signal ak-al relative to the signal ak-al. The maximum value of the shift amount j is determined according to the maximum extension value of the lens used, and is usually |l−
n|=|k-1|.

FIG. 9 shows the relationship with the amount of defocus e obtained from the control circuit 26.

FIG. 10 is a flowchart showing the zero-cross detection operation. Shifting of signals b ₁ to bn is performed using binary classification method (successive approximation method), and the maximum shift amount is
jmax is jmax∝maximum extension amount of the photographing lens, and the calculation range is as shown in Figure 8, and j
Since the ^relationship between First, the output of the integration circuit 46
If Yj is 0, it is at the in-focus position, so j'=0. If Yj is not 0, the parameter I is reset, and the direction and amount of shift are determined based on the positive or negative value of Yj, and the shift is performed. And if Yj=0, then j
= j′, so the shift ends. If Yj does not become 0, the shift amount is incremented and the above operation is performed again. When the shift amount reaches the maximum value,
Depending on whether Yj is positive or negative, the near-zero value Yj ₂ ′ or Yj ₁ ′ of the output signal of the integration circuit 46 and the shift amount j ₁ , j ro
₂ , find j' by the operation j' = j lo ₁ − j lo ₁ − j lo ₂ /Yj ₁ ′−Yj ₂ ′Yj ₂ ′. Here, Yj ₁ ′ and Yj ₂ ′ are the closest values in the vicinity of zero, and j ₁ and j ₂ are the shift amounts at that time.

The control circuit 26 was selected as described above.
j' and the F-number mode signal from the F-number mode setting section 50, and displays the amount e on the display device 51, and sets it in the subtraction counter 52.
A rotation direction signal and a speed signal are given to the motor drive circuit 53 to rotate the motor 54 and the photographing lens 1 is rotated.
Move 3. Pulse generator 5 is photographing lens 1
A number of pulses proportional to the amount of movement of 3 are generated, and the subtraction counter 52 is subtracted by these pulses.
When the subtraction canter 52 becomes 0, it sends a stop signal to the motor drive circuit 53 to stop the motor 54, thereby stopping the photographing lens at the in-focus position. The control circuit 26 corrects the differential focus signal based on the F value mode signal from the F value mode setting section 50 (or the period of the pulse generator 55 is controlled by the F value mode signal), and the relationship between j' and e is changed to F.
Controlled constant regardless of value mode switching.
The control circuit 26 causes the warning device 56 to display a warning during focusing. Also memory 36
The output signals are integrated by the integrating circuit 57 and divided by the number of signals by the dividing circuit 58, thereby performing the calculation Σbi/i and measuring the brightness of the subject.
The control circuit 26 controls the integration time of the CCD 25 using the output signal of the division circuit 58, and also provides a photometry signal to the automatic exposure circuit 59 to calculate exposure, and performs exposure control based on its output.

(Effects) As described above, according to the present invention, the subject image is divided and detected by the first set of photoelectric element groups and the second set of photoelectric element groups, and the force signal of the first set of photoelectric element groups is detected by the shift means. Since the output signals of the second set of photoelectric elements are shifted relative to each other, there is no need to move lenses or the like. Furthermore, the amount of defocus is detected by detecting the shift amount of the shift means that corresponds to the peak value of the integrated value obtained for each shift amount of the shift means. Since it has a calculation means that detects a plurality of defofocus amounts according to the distance distribution, it is possible to detect a plurality of defofocus amounts for a three-dimensional object without moving the lens or the like. Furthermore, a distance measurement mode setting section for arbitrarily setting one of distance measurement modes among a far point mode, an average weight mode, and a near point mode having different distance measurement ranges, and a distance measurement mode setting section for arbitrarily setting one of distance measurement modes having different distance measurement ranges from each other; A control circuit is provided to select the amount of defocus according to the ranging mode signal from the mode setting section.
One defocus amount can be selected from a plurality of defocus amounts for a three-dimensional object without moving the lens or the like.

[Brief explanation of drawings]

Figures 1 to 3 are front views showing examples of focus detection optical systems, Figures 4 to 6 are diagrams for explaining the present invention, and Figure 7 is an electric circuit in one embodiment of the present invention. FIG. 8 is a diagram showing the calculation range of the electric circuit, and FIGS. 9 and 10 are diagrams for explaining the present invention. 25...CCD, 26...control circuit,
29...A/D converter, 30-33, 35, 36
...Memory, 34...Shift circuit, 37...Differential circuit, 40...Peak detection circuit, 48...J' operation circuit.

Claims (1)

[Scope of Claims] 1. A first set of photoelectric element groups and a second set of photoelectric element groups that divide and detect a subject image; Shift means for relatively shifting the output signals of the photoelectric element groups, and the output signals of the first set of photoelectric element groups and the output signals of the second set of photoelectric element groups that are relatively shifted by the shift means. Differences between the output signals of the corresponding pairs of photoelectric elements are multiplied and integrated, and the shift amount of the shift means corresponding to the peak value of the integrated values obtained for each shift amount of the shift means is detected. By detecting the amount of defocus,
For a three-dimensional subject, there is a calculation means for detecting multiple amounts of defocus according to the distance distribution of the subject, and a distance measurement method in one of a far-focus mode, an average-focus mode, and a near-focus mode with different distance measurement ranges. It is characterized by comprising a distance measurement mode setting section for arbitrarily setting a mode, and a control circuit for selecting a differential focus amount from among the plurality of differential focus amounts according to a distance measurement mode signal from the distance measurement mode setting section. Automatic focus detection device.