JP2909978B2 - Imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing apparatus having a photoelectric conversion means for photographing and performing still photography.

[0002]

2. Description of the Related Art The above-mentioned camera is usually provided with an automatic focus adjusting device for automatically adjusting the focus of a photographing optical system to a subject. The automatic focus adjustment device includes an active method in which measurement light is projected onto a subject and focus detection and focus adjustment are performed based on the reflected light, and an image formation state of a subject image by a photographing optical system or an equivalent optical system. There is a passive method for performing focus detection and focus adjustment. In the active method, an infrared light emitting diode is generally used for projecting measurement light. Further, cameras equipped with an imaging photoelectric conversion element such as a CCD include a system having a dedicated light receiving element for focus detection and a system utilizing the output of the imaging photoelectric conversion element. The latter has the advantage that the production cost can be reduced and the size can be reduced because the dedicated light receiving element and the processing circuit for the output thereof are not required.

[0003]

In any of the active system and the passive system, when there is a certain amount of light, a sufficiently accurate focus adjustment can be performed. In some cases, an auxiliary light is needed for focusing. In other words, even in the passive system, an auxiliary light source for focus adjustment must be prepared in order to perform photographing in a dark place.

Of course, in photographing in a dark place, the photographing itself requires auxiliary light such as strobe light or DC current-driven illumination light, but the necessary light quantity differs between focus adjustment and photographing. In particular, without using a dedicated light receiving element for focus adjustment,
In a camera that performs focus detection and adjustment based on the output signal of the imaging photoelectric conversion element, even if the image is bright enough without using a strobe or by using a strobe, if the brightness is insufficient for focus adjustment, , An auxiliary light source, which also needs to be turned on at least during the focusing operation.

[0005] It is an object of the present invention to eliminate such inconveniences and to provide a photographing apparatus capable of performing a focus adjustment without using an auxiliary light source to the extent possible.

[0006]

Imaging apparatus according to the present invention SUMMARY OF THE INVENTION is an imaging apparatus comprising an automatic focusing device which performs focus adjustment by using an image signal obtained from the photoelectric conversion means for imaging, the subject brightness Is below a certain level
Set the imaging photoelectric conversion means to focus adjustment sensitivity
The flash slightly to adjust the focus.
After completion, switch to shooting sensitivity and fire the flash
It is characterized in that it is configured to perform photographing .

[0007]

According to the above-mentioned means, the chance of requiring an auxiliary light source only for focus adjustment is reduced, and the degree of freedom of photographing is increased accordingly.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention applied to an electronic still camera. Reference numeral 10 denotes a photographing lens unit having a zoom function, which includes an aperture and a shutter inside. Reference numeral 12 denotes a solid-state imaging device that converts an optical image into an electric signal, 14 denotes an imaging processing circuit that converts an output signal of the imaging device 12 into a video signal, and 16 denotes a signal for recording a video signal output from the imaging processing circuit 14. A recording processing circuit for converting the magnetic disk into a recording medium, a magnetic head, a magnetic disk as a recording medium, a spindle motor for rotating the magnetic disk, and a spindle motor for rotating the magnetic disk.
2 is a motor drive circuit for driving the magnetic head 18 to a designated radius position of the magnetic disk 20, that is, a designated track.

Reference numeral 28 denotes a lens driving circuit for driving a zooming lens and a focusing lens of the photographing lens unit 10, reference numeral 30 denotes a diaphragm driving circuit for driving the diaphragm of the photographing lens unit 10, and reference numeral 32 denotes a shutter of the photographing lens unit 10. Is a shutter drive circuit for driving the shutter.

Reference numeral 34 denotes a low-pass filter (LPF), 3
6 is a band-pass filter (BP) for extracting high frequency components.
F), 38 are BPFs having a band narrower than the BPF 36, 40 is a switch for selecting the outputs of the LPFs 34, 36 and 38, 42 is an A / D converter for digitizing the output of the switch 40, and 44 is an A / D converter for one screen. D converter 42
Is an integration circuit for integrating the output data of.

Numeral 46 denotes a microcomputer which performs a predetermined operation and controls the whole operation.
48 is a key for inputting a predetermined instruction to the arithmetic control circuit 46;
An operation device including switches, a display device 50 for displaying an operation state and the like, a strobe light 52, a strobe light 54
Is a flash drive circuit for emitting light.

For easy understanding, first, the recording operation of a photographed image after the focus adjustment is completed will be briefly described. The optical image obtained by the photographing lens unit 10 is converted into an electric signal by the image sensor 12, and the output signal of the image sensor 12 is converted into a video signal by the image processing circuit 14. The recording processing circuit 16 performs a recording process on the video output of the imaging processing circuit 14 and converts the video output into a signal for recording. The output of the recording processing circuit 16 is recorded on the magnetic disk 20 by the magnetic head 18.

The magnetic disk 20 is rotated at a predetermined speed by a spindle motor 22 driven by a motor drive circuit 24.
6 to the designated track of the magnetic disk 20.

Next, the operation of this embodiment relating to focus adjustment will be described. 2 shows a flowchart of the main routine, FIG. 3 shows a detailed flowchart of S8 in FIG. 2, and FIG. 5 shows a detailed flowchart of S4 in FIG. In FIG. 2, first, the sensitivity of the imaging system (aperture, shutter time, gain of the imaging processing circuit 14) is set to the maximum sensitivity when the strobe light 52 is not used, and the brightness data of the subject is taken into the arithmetic control circuit 46. (S1). Specifically, the aperture of the photographing lens unit 10 is fully opened, the shutter is operated at an appropriate shutter time for daytime photographing, and the imaging processing circuit 14 is operated.
The image pickup device 12 is exposed with the gain of the image pickup device considerably increased. The output of the image pickup device 12 is converted into a video signal by the image pickup processing circuit 14, and the LPF 34 and the BPFs 36, 38
Is applied to In the initial stage, the switch 40
34, the BPFs 36 and 38 are sequentially selected to select high-frequency components. The output of switch 40 is A
The signal is applied to the integration circuit 44 via the / D converter 42, and the integration circuit 44 performs integration within one screen and outputs brightness data to the arithmetic control circuit 46.

The arithmetic control circuit 46 compares the brightness data from the integrating circuit 44 with a predetermined level (S2). If the integrated value is equal to or less than the predetermined level, the sensitivity of the imaging system is set to the sensitivity for AF (focus adjustment) (S3), the strobe light 52 is weakly illuminated (pre-emission), and the photographic lens unit 10
Focus adjustment by focusing lens (S
4) The sensitivity of the imaging system is set to the sensitivity for flash photography (S
5), the strobe 52 is charged and enters a standby state (S6,
9). When the integral value exceeds a predetermined value, (S
2) The sensitivity of the imaging system is set to a general sensitivity for daytime shooting (S
7), the focus is adjusted by the focusing lens of the photographing lens unit 10, and a standby state is established (S8,
9).

In this embodiment, in a photographing environment where auxiliary lighting such as strobe light is required, the strobe light is weakly emitted, and the illumination facilitates focus detection and adjustment. An image captured by weak flash emission has poor image quality and is not suitable for recording for recording, but does not hinder focus adjustment.

The basic operation of S8 in FIG. 2 will be described with reference to FIG. Regardless of which of the LPF 34, the BPF 36, and the BPF 38 the switch 40 selects, the integrated output of the integrating circuit 44, as shown in FIG.
The movement of the focusing lens of 0 becomes maximum at the in-focus position and becomes smaller as the distance from the in-focus position increases. The detection accuracy of the in-focus position becomes higher as the band becomes narrower, but the accuracy of detecting the direction of the in-focus position when deviating from the in-focus position decreases. Therefore, at a stage far from the focus position, the LPF 34 having a wide band is selected.
The switch 40 is controlled so that the PF 36 and the BPF 38 are selected. In addition, LPF34, BPF36 and B
Although the integration level generally differs depending on which of the PFs 38 is selected, in the present embodiment, the operation control circuit 4
6, standardized before evaluation.

First, the integration output of the integration circuit 44 is fetched (S11), and the focusing lens of the photographing lens unit 10 is moved to the infinity side by one step by the lens drive circuit 28 (S12). Then, the integrated output of the integrating circuit 44 is fetched (S13), and is compared with the integrated value fetched immediately before (S14). As long as the integral value on the infinity side is large, the step movement of the focusing lens toward the infinity side is repeated (S14).

If the integral value on the infinity side is not large (S1
4) The focusing lens is moved to the nearest side by one step (S15), the integrated output of the integrating circuit 44 at that position is taken in (S16), and compared with the immediately preceding integrated value (S17). As long as the integral value on the close side is large, the step movement of the focusing lens to the close side is repeated (S
17).

If the integral value on the close side does not become large, it is determined that the position of the focusing lens one step before is the in-focus position, and the focusing lens is returned one step toward infinity (S18). The focus is displayed and the focus adjustment operation ends (S19).

Referring to FIG. 5, the basic operation of S4 of FIG. 2 will be described. It is basically the same as FIG. 3 except that the strobe light is weakly emitted as necessary.
4. The same applies to the selection of the BPF 36 and the BPF 38.

First, the strobe light 52 is weakly illuminated, the integrated output of the integrating circuit 44 for the captured image under the illumination is fetched (S111), and the focusing lens of the photographic lens unit 10 is moved by one step by the lens driving circuit 28. Move to infinity side (S112). Then, the strobe light 52 is made to emit light weakly, and the integrated output of the integrating circuit 44 for the captured image under the illumination is captured (S113), and is compared with the integrated value captured immediately before (S114). As long as the integral value on the infinity side is large, the step movement of the focusing lens toward the infinity side is repeated (S114).

If the integral value on the infinity side is not large (S1
14), the focusing lens is moved to the closest side by one step (S115), and the strobe light 52 is weakly emitted at that position, and the integrated output of the integrating circuit 44 for the captured image under the illumination is taken in (S116). A comparison is made with the immediately preceding integral value (S117). As long as the integral value on the close side is large, the step movement of the focusing lens to the close side is repeated (S117).

If the integral value on the close side does not become large, it is determined that the position of the focusing lens one step before is the in-focus position, and the focusing lens is returned one step toward infinity (S118). The focus is displayed and the focus adjustment operation ends (S119).

FIG. 6 is a block diagram showing the configuration of another embodiment of the present invention. Components having the same functions as those in FIG. 1 are denoted by the same reference numerals. In this embodiment, an A / D converter 60, a memory control circuit 62, a memory 64, and a D / A converter 66 are connected between the imaging processing circuit 14 and the recording processing circuit 16, and the D / A conversion is performed. The output of the device 66 is LPF34 and BPF3
6,38. The memory 64 has a storage capacity capable of storing photographed image data at all step positions of the focusing lens of the photographing lens unit 10 (may be image data appropriately thinned out on the screen within a range that does not hinder focus detection). Is provided. The arithmetic control circuit 68 is composed of a microcomputer similarly to the arithmetic control circuit 46, and controls the whole of FIG.

In the embodiment shown in FIG. 6, the output video signal of the imaging processing circuit 14 is written to the memory 64 via the A / D converter 60 and the memory control circuit 62 and read from the memory 64, as compared with FIG. The only difference is that the obtained image data is applied to the recording processing circuit 16 and the LPF 34 and the BPFs 36 and 38 via the memory control circuit 62 and the D / A converter 66, and the focus adjustment operation by the focusing lens is different. That is, the contents of S4 and S8 in FIG. 2 are different. FIG. 7 shows a flowchart of the focus adjustment operation in S8 of FIG. 2 in the embodiment of FIG. 6, and FIG. 8 shows a flowchart of the focus adjustment operation of S4 in FIG.

In FIG. 7, first, the focusing lens is positioned at infinity (S21), a loop variable n is initialized (S22), and photographed image data is taken into the n-th storage area in the memory 64 (S23). . Until the total number of steps of the focusing lens reaches N (S24), the photographing image data of each step is loaded into the memory 64 while the focusing lens is being moved one step at a time to the nearest side (S23, 25, 26).

When n = N, that is, when the photographed image data at all the step positions of the focusing lens is taken into the memory 64 (S24), the completion of the taking is displayed on the display device 50 (S27). The image data at each step position is sequentially read from the memory 64 by the memory control circuit 62,
LPF34, BPF36, 38, switch 40, A / D
The converter 42 and the integration circuit 44 search for an image having the highest frequency component (S28). The focusing lens is moved to the step position of the image having the highest high frequency component (S29), and the display device 50 performs the in-focus display (S30).

FIG. 8 differs from FIG. 7 in that the strobe light 52 emits weak light when image data is taken into the memory 64. That is, in FIG. 8, first, the focusing lens is positioned at infinity (S121), the loop variable n is initialized (S122), the strobe light 52 is weakly emitted, and the data of the captured image under the illumination is stored in the memory 64. (S123). Until the total number N of steps of the focusing lens is reached (S124), the photographing image data under the weak flash emission of each step is taken into the memory 64 while the focusing lens is being moved one step at a time to the nearest side (S123, 125, 126). ).

When n = N, that is, when the photographed image data at all the step positions of the focusing lens is taken into the memory 64 (S124), the completion of the taking is displayed on the display device 50 (S127). The image data at each step position is sequentially read from the memory 64 by the memory control circuit 62, and the LPF 34, the BPFs 36 and 38, the switch 40,
The / D converter 42 and the integrating circuit 44 search for an image having the highest frequency component (S128). The focusing lens is moved to the step position of the image having the highest high frequency component (S129), and the display device 50 performs the in-focus display (S130).

As described above, the method of stepwise moving the focusing lens from infinity to the closest side and collecting basic data necessary for focus adjustment can be adopted also in the embodiment of FIG. In FIG. 1, the integration output of the integration circuit 44 is stored in the arithmetic and control circuit 46, and when the integrated values of all the steps are stored, the focusing lens is moved to the step position of the largest integrated value.

FIG. 9 is a block diagram showing the configuration of still another embodiment of the present invention. The components having the same functions as those in FIG. 1 are denoted by the same reference numerals. In this embodiment, the A / D converter 70 and the storage for at least two screens are provided between the imaging processing circuit 14 and the recording processing circuit 16. A memory 72 having a capacity, a memory control circuit 74, and a D / A converter 76 are connected, and an LPF 3
4, BPFs 36 and 38, switch 40, A / D converter 4
2 and the integration circuit 44 is removed. Numeral 78 is an arithmetic control circuit for controlling the whole.

In the embodiment shown in FIG.
Is written to the memory 72 via the A / D converter 70 and the memory control circuit 74, and the image data read from the memory 72 is stored in the memory control circuit 74 and D
It is applied to the recording processing circuit 16 via the / A converter 76.

In the embodiment shown in FIG.
Focus detection and adjustment is performed by correlation of images from adjacent step positions of the lens. That is, the correlation between the images at adjacent step positions of the focusing lens becomes smaller as the distance from the in-focus position increases. For example, when the integrated value of the absolute value of the difference between the images is viewed on one screen, as shown in FIG. We take advantage of being lowest in location. It can be obtained by calculation from image data of two screens stored in the memory 74. Therefore, the LPF 3 provided in the embodiment of FIG.
4, BPFs 36 and 38, switch 40, A / D converter 4
2 and the integration circuit 44 become unnecessary.

FIGS. 10 and 12 show flowcharts of the focus adjusting operation in the embodiment of FIG. FIG. 10 is a diagram showing S8 in FIG.
FIG. 12 shows a detailed flowchart of S4 in FIG.

In FIG. 10, first, image data is fetched into the memory 74 (S41), and the focusing lens is moved to the infinity side by one step (S42). The image data is also taken into the memory 74 at the step position (S43), and the correlation with the image one step before (integration of the absolute value of the difference) is obtained (S44). If the correlation value is equal to or less than the specified level (S45), the in-focus state is displayed and the processing is terminated (S54). If the correlation value exceeds the specified level (S4).
5) When the correlation is obtained twice or more (S46),
The correlation between the present and the previous one is compared (S47). If the closest side is larger, the process returns to S42. If the closer to infinity, the focusing lens is moved to the closest side by two steps (S47).
48). The image is fetched into the memory 74, the focusing lens is moved one step closer to the nearest side (S50), the image is fetched into the memory 74 (S51), and the correlation between the current image and the previous one is obtained (S52). If the level is lower than the level, the in-focus state is displayed and the processing ends (S54). If the level is higher than the specified level, the focusing lens is moved to the closest side by one step until the level becomes lower than the specified level (S54).
50, 51, 52, 53).

In FIG. 12, first, the strobe light 52 is weakly emitted, the image data of the captured image under the illumination is taken into the memory 74 (S141), and the focusing lens is moved to the infinity side by one step (S142). ).
Also at that step position, the image data of the image captured under the weak light emission of the strobe light 52 is loaded into the memory 74 (S14).
3) The correlation with the image one step before (integration of the absolute value of the difference) is obtained (S144).

If the correlation value is below the specified level (S14)
5) The in-focus state is displayed and the processing ends (S15).
4) If the level exceeds the prescribed level (S145) and the correlation is obtained twice or more (S146), the correlation between the present and the previous one is compared (S147), and if the closest side is larger, the process returns to S142. If the infinity side is large, the focusing lens is moved to the closest side by two steps (S1).
48). The captured image data under the weak light emission of the strobe light 52 is fetched into the memory 74 (S149), and
The lens is moved to the close side by one step (S150), and the image data under the weak light emission of the strobe light 52 is stored in the memory 74.
(S151), the correlation between the image and the current image is calculated one step before (S152). If the image is below the specified level, the in-focus state is displayed and the processing ends (S154). The focusing lens is moved one step at a time to the nearest side until the distance becomes less than or equal to (S15).
0, 151, 152, 153).

In FIGS. 10 and 12, what is taken into the memory 74 is not necessarily the entire image data of one screen, but is the image data which has been appropriately thinned out within a range that does not hinder the correlation. Is also good. When thinning out,
The storage capacity of the memory 74 can be reduced.

FIGS. 13 and 14 show another flowchart of the focus adjustment in the embodiment of FIG. FIG. 13 shows FIG.
FIG. 14 shows a detailed flowchart of S8 in FIG. 2, and FIG. 14 shows a detailed flowchart of S4 in FIG.

In FIG. 13, first, focusing
The lens is positioned at infinity (S61), the loop variable n is initialized (S62), and the captured image data is taken into the n-th storage area in the memory 74 (S63). Until the total number of steps of the focusing lens reaches N (S64),
While moving the focusing lens one step at a time to the closest side, the captured image data of each step is loaded into the memory 74 (S63, 65, 66).

When n = N, that is, when the photographed image data at all the stepping positions of the focusing lens is taken into the memory 74 (S64), the completion of the taking is displayed on the display device 50 (S67). The image data of one step before and after is read from the memory 74 by the memory control circuit 72, and the correlation of the images is obtained (S68). The focusing lens is moved to the step position having the highest correlation (S69), and the display device 50 performs in-focus display (S70).

In FIG. 14, first, the focusing
The lens is positioned at infinity (S161), and the loop variable n
Is initialized (S162), and the image data captured under the weak light emission of the strobe light 52 is loaded into the n-th storage area in the memory 74 (S163). Until the total number of steps of the focusing lens reaches N (S164), focusing
At each step, the image data under the weak light emission of the strobe light 52 is taken into the memory 74 while the lens is moved one step at a time to the nearest side (S163, 165, 166).

When n = N, that is, when the photographed image data at all the step positions of the focusing lens is taken into the memory 74 (S164), the completion of the taking is displayed on the display device 50 (S167). The memory control circuit 72 reads out the image data of about one step from the memory 74,
An image correlation is obtained (S168). The focusing lens is moved to the step position having the highest correlation (S16
9) Focus display is performed by the display device 50 (S1).
70).

As described with reference to FIGS. 6, 7 and 8, in the case of FIGS. 13 and 14, it is not necessary to load the entire image data of one screen into the memory 74. I just need to take in.

Although an electronic still camera using a magnetic disk as a recording medium has been described as an example, the present invention can be applied to an electronic camera using a solid-state memory device as a recording medium, as well as a video camera and a TV camera.

[0048]

As can be easily understood from the above description, according to the present invention, accurate focus adjustment can be performed without an auxiliary light source other than a strobe at a brightness insufficient for focus adjustment. become.

[0049]

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a flowchart of a pre-imaging preparation routine.

FIG. 3 is a detailed flowchart of S8 of FIG. 2 in the embodiment of FIG. 1;

FIG. 4 is a relationship diagram between a degree of focus adjustment and an integrated value.

FIG. 5 is a detailed flowchart of S4 of FIG. 2 in the embodiment of FIG. 1;

FIG. 6 is a configuration block diagram of another embodiment.

FIG. 7 is a detailed flowchart of S8 of FIG. 2 in the embodiment of FIG. 6;

FIG. 8 is a detailed flowchart of S4 of FIG. 2 in the embodiment of FIG. 6;

FIG. 9 is a configuration block diagram of still another embodiment.

FIG. 10 is a detailed flowchart of S8 of FIG. 2 in the embodiment of FIG. 9;

FIG. 11 is a diagram illustrating a relationship between a degree of focus adjustment and a correlation (an integral value of an absolute value of a difference between screens).

FIG. 12 is a detailed flowchart of S4 of FIG. 2 in the embodiment of FIG. 9;

FIG. 13 is another detailed flowchart of S8 of FIG. 2 in the embodiment of FIG. 9;

FIG. 14 is another detailed flowchart of S4 of FIG. 2 in the embodiment of FIG. 9;

[Explanation of symbols]

10: photographic lens unit 12: solid-state image sensor 1
4: imaging processing circuit 16: recording processing circuit 18: magnetic head 20: magnetic disk 22: spindle motor 24: motor driving circuit 26: head driving circuit 2
8: Lens drive circuit 30: Aperture drive circuit 32: Shutter drive circuit 34: LPF 36, 38: BPF 4
0: switch 42: A / D converter 44: integrating circuit
46: arithmetic control circuit 48: operating device 50: display device 52: strobe 54: strobe drive circuit 60: A
/ D converter 62: Memory control circuit 64: Memory 6
6: D / A converter 68: Operation control circuit 70: A / D
Converter 72: Memory control circuit 74: Memory 76: D
/ A converter 78: Operation control circuit

Claims (1)

(57) [Claims] 1. A photographing apparatus comprising an automatic focus adjustment device for performing focus adjustment using an image signal obtained from an imaging photoelectric conversion means, wherein the brightness of a subject is lower than a predetermined level.
If there is, the imaging photoelectric conversion means is used for focus adjustment.
Set the sensitivity, make the strobe light weak, and adjust the focus.
After focus adjustment is complete, switch to
Is configured to shoot by emitting light.
Photographing apparatus characterized by that.