JP4164413B2 - Auto focus camera - Google Patents

Description

[0001]
【Technical field】
The present invention relates to an autofocus camera, and more particularly to an autofocus camera having a plurality of distance measuring points (autofocus positions).
[0002]
[Prior art and its problems]
In a conventional autofocus (autofocus) type camera, since there are few distance measuring points (about 1 to 3 points), a cosine error is likely to occur. Here, the cosine error means that when focusing is performed with the focus point at the center of the screen as the reference and the camera is shaken by an angle θ to recompose the image, the cosine error (cos θ) of the shake angle is initially focused. It is a phenomenon that it becomes a pin behind the position. This phenomenon is remarkable in a wide-angle lens having a short focal length. This is because the angle of swing tends to increase because the angle of view is large. This phenomenon is also likely to occur when the depth of field is shallow, for example, by opening the lens aperture. On the other hand, when a telephoto lens having a long focal length is used or when the depth of field is deep, cosine errors are relatively rare.
[0003]
On the other hand, in recent years, the number of autofocus distance measuring points has been increased in order to perform more precise distance measurement in accordance with the needs of photographers. In a camera with multiple ranging points, it is less likely that a cosine error will occur because there is little need to shake the camera after focusing.
[0004]
In an autofocus camera having multiple ranging points, a desired ranging point is selected by operating a ranging point selection button provided on the back of the camera while viewing the ranging point display in the viewfinder.
[0005]
However, it is not preferable to move the distance measuring points one by one by using the distance measuring point selection button to select only one of many distance measuring points, because this complicates the photographer. .
[0006]
OBJECT OF THE INVENTION
Accordingly, an object of the present invention is to provide an autofocus camera in which an operation for selecting a desired distance measuring point from a number of distance measuring points is facilitated.
Other objects of the present invention and features of the present invention will become more apparent by reading the following detailed description with reference to the accompanying drawings.
[0007]
SUMMARY OF THE INVENTION
According to the present invention, in a camera with a variable focal length, the number of distance measuring points is smaller as the focal length becomes longer and the angle of view becomes smaller. Conversely, as the focal length becomes shorter and the angle of view becomes larger, a larger number of distance measuring points are required. Based on the recognition that it would be convenient to increase or decrease the number of distance measuring points or / and change the arrangement according to the focal length based on the recognition that it is necessary.
[0008]
The present invention provides an autofocus camera in which a photographer can select any one of a plurality of distance measuring points, and a finder capable of displaying the positions of the plurality of distance measuring points by light emitted from a light source. A focal length detecting means for detecting a focal length of the photographing lens from a storage medium provided in the photographing lens, a light source driving unit for selectively driving all or a part of the light sources corresponding to the plurality of distance measuring points, according to the focal length of the detected photographing lens focal length detection means, and drives the light source driving section, have a control means for changing the number and / or arrangement of the distance measuring point to be displayed on the viewfinder, measured The number of distance points is larger as the focal length is shorter and smaller as the distance is longer, and the distance between the distance measurement points is larger when the focal distance is shorter .
[0009]
The photographic lens is preferably detachably attached to the camera body.
[0010]
Information on the focal length of the photographic lens is stored in the storage medium provided in the photographic lens, and the focal length detection unit reads information on the focal length of the photographic lens from the storage medium and detects the focal length of the photographic lens. It is preferable to do this.
[0011]
The autofocus camera of the present invention further includes a distance measuring point selection unit for the photographer to select one distance measuring point from a plurality of distance measuring points displayed on the finder, and the photographer selects the distance measuring point. It is preferable to have display changing means (control means) for making the display of the selected distance measurement point different from the display of other distance measurement points when the one distance measurement point is selected by operating the point selection unit.
[0012]
The light source is preferably a two-color LED, and more preferably a plurality of light sources corresponding one-to-one with a plurality of distance measuring points.
[0013]
As the focal length of the photographic lens becomes shorter, it is preferable that manual selection is possible up to a distance measuring point farther from the center of the photographic region.
[0014]
The plurality of distance measuring points are preferably arranged symmetrically with respect to the center of the imaging region.
[0015]
It is preferable that the distance between the two distance measuring points farthest from the center of the photographing region increases as the focal length of the photographing lens becomes wider.
[0016]
It is preferable that a plurality of distance measuring points have substantially the same distance between two adjacent distance measuring points.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
The camera body 1 of the present embodiment shown in FIG. 1 is an autofocus type digital camera (digital still camera), and an interchangeable lens barrel L including a lens (photographing lens) 6 can be attached to and detached from the mount 5. It is attached. The lens barrel to be mounted can be either a single focus lens or a zoom lens whose focal length can be arbitrarily changed, but in this embodiment, a zoom lens barrel equipped with a zoom lens is mounted. It will be described below.
[0018]
As shown in FIG. 2, most of the subject light that has passed through the lens 6 and entered the camera body 1 is reflected by the first mirror 7, reflected by the focus prism (projection surface) 9, and reflected by the penta prism 11. The eyepiece lens group 13 is reached. The focus plate 9, the pentaprism 11 and the eyepiece lens group 13 constitute a finder optical system 14. A part of the light reflected by the pentaprism 11 is incident on a photometric element 17 (for example, a photodiode or photometric IC) through a photometric lens 15. In FIG. 2, the path of light in the camera body 1 is indicated by a one-dot chain line.
[0019]
In the photometry element 17, when a photographer presses a photometry switch (not shown), a signal corresponding to the amount of incident light is output to the exposure control block 19. In the exposure control block 19, an exposure condition is determined based on the input signal, and the determined exposure condition is sent to the CPU 21. The CPU 21 outputs drive signals and control signals to the aperture drive mechanism 23, the mirror & shutter drive mechanism 25, and the strobe control block 27 according to the exposure conditions. In the aperture drive mechanism 23 and the mirror & shutter drive mechanism 25, the photographic lens 6 and the shutter 29 are driven so that the photographic lens 6 is driven with an aperture according to the exposure condition and the shutter 29 is driven at a shutter speed according to the exposure condition. Send drive signal to. The strobe control block 27 outputs a drive signal to emit the strobe 31 when a predetermined control signal is input.
[0020]
The photographer can confirm the photographing range encompassed by the photographing lens 6 by looking through the finder optical system 14, and uses this to adjust the desired composition and the like. When the mounted lens barrel L is a zoom lens, the focal length of the lens 6 can be adjusted. The focal length is adjusted by the photographer turning the zoom ring LR provided in the zoom lens barrel L. When the lens barrel L is a zoom lens, information on each settable focal length is stored in a lens ROM 33 (storage medium) provided in the zoom lens barrel L, and provided in the lens barrel L. A code plate (not shown) and a brush (not shown) that slides on the code plate in conjunction with the zoom ring LR are provided, and the current focal length in the lens ROM 33 is set in accordance with the conduction state of the brush. The address where the corresponding information is stored is determined, and the information regarding the focal length stored at the address can be read out to the camera body side. When the lens barrel L includes a single focus lens, the code plate and the brush are not included, and single focal length information is stored in the lens ROM 33.
[0021]
In a state in which the lens barrel L is mounted on the camera body 1, the lens ROM 33 is electrically connected to the CPU 21 in the camera body 1 via a signal line (not shown) and a contact group provided on the mount. Thus, mutual information communication is possible.
[0022]
When the photographer turns the zoom ring LR, the current focal length information stored in the lens ROM 33 is read by the CPU 21 serving as a reading unit. When the lens barrel L is a single focus lens, the focal length information stored in the lens ROM 33 is read by the CPU 21. The CPU 21 outputs an LED drive signal to the superimpose block 35 that constitutes the light source drive unit together with the CPU 21 based on the correspondence table of the focal length and the number of distance measuring points and / or the arrangement stored in the table 34.
[0023]
On the other hand, the light transmitted through the half mirror at the center of the first mirror 7 is reflected by the second mirror 37 and enters an AF (autofocus) unit 39. The CPU 21 sends a focus adjustment signal to the AF drive mechanism 41 in accordance with the light incident on the AF unit 39. The AF drive mechanism 41 adjusts the extension amount of the photographing lens 6 based on the focus adjustment signal. Also, the AF unit 39 adjusts the focal point for the distance measuring point (AF position) selected by the photographer. The selection of the distance measuring point will be described later.
[0024]
When the photographer presses the photometry switch / release switch 43, the first mirror 7 and the second mirror 37 rotate around their rotation centers based on the drive signal sent from the CPU 21 to the mirror & shutter drive mechanism 25. Then, the shutter 29 is retracted from the photographing optical path (dotted line in FIG. 2), and the shutter 29 is opened. Thus, the subject light transmitted through the lens 6 travels straight and enters the CCD (charge coupled device) 47 through the optical low-pass filter 45. On the other hand, the CCD 47 starts operating based on a drive signal input from the CPU 21 to the CCD driver 51 via the clock generator 49. Information on the light incident on the CCD 47 is amplified by an amplifier (AMP) 53 and then sent to the exposure control block 19 and the A / D conversion block 55. The information digitized by the A / D conversion block 55 is processed by the signal processing block 57 and the compression / non-compression block 59 and then stored in the image memory 61. Simultaneously with the elapse of a predetermined exposure time, the shutter 29 is closed based on the drive signal from the mirror and shutter drive mechanism 25, the operation of the CCD 47 is stopped, and the photographing is finished.
[0025]
Each mechanism and block in the camera are driven by electric power supplied from the battery 63 via the DC / DC converter 65. The photographer can set a desired shooting mode by operating the mode setting button 67. Information such as the set shooting mode and exposure conditions is displayed on the external display 69.
[0026]
In the camera of the present embodiment, the photographer can select one of a number of distance measuring points and perform automatic focus adjustment on the distance measuring point. FIG. 4 is a diagram showing all distance measuring points that can be displayed on the viewfinder. As shown in FIG. 4, there are 13 ranging points in total, 7 points in the vertical direction (A, B, C, D, E, F, G in order from the top), 7 points in the horizontal direction (H from the left) , I, J, D, K, L, M) are arranged in a cross shape. The distance measuring point is lit and displayed in a rectangular shape by the light emitted from the LED of the superimpose block 35. Here, the distance measuring point D is arranged at a position corresponding to the center of the imaging region. E, F, and G are arranged symmetrically with respect to D, respectively with C, B, and A. H, I, and J are arranged symmetrically with respect to D, respectively with M, L, and K. Has been.
[0027]
The distance measuring points (A, B, C, D, E, F, G) arranged in the vertical direction are arranged at equal intervals with a distance D _1v between adjacent distance measuring points. Similarly, the distance measuring points (H, I, J, D, K, L, M) arranged in the horizontal direction are equally spaced at a distance D _1H between adjacent distance measuring points. . D _1v and D _1H may be the same.
[0028]
As shown in FIG. 2, the superimpose block 35 is provided between the mount 5 and the AF unit 39. The superimpose block 35 includes 13 two-color light emitting LEDs 71, a pattern mask 73 and a lens 75 provided on the optical axis of each LED. The LED 71 has a cross shape corresponding to seven distance measuring points (A to G in FIG. 4) in the vertical direction in the finder optical system 14 and seven distance measuring points (H to M) in the left and right direction. It is arranged. The central LED in the horizontal direction and the central LED in the vertical direction (corresponding to point D in FIG. 4) are common. The light emitted from the LEDs 71 is shaped into a predetermined shape by the pattern mask 73 and enters the focus plate 9 through the lens 75. Each LED 71 is independently controlled by a drive signal sent from the CPU 21.
[0029]
The selection of distance measuring points will be described below. In the present embodiment, the number of distance measuring points that can be selected is changed according to the focal length of the imaging lens 6 to be used. This is to provide a shooting environment free from cosine error without forcing the photographer to perform complicated operations by selecting a desired distance measuring point from an appropriate number of distance measuring points.
[0030]
FIG. 5 shows an example of a finder display in which range-finding points that can be used at each focal length are shown. 5A shows a case where the focal length is 85 mm or more, FIG. 5B shows a case where the focal length is 50 mm or more and less than 85 mm, FIG. 5C shows a case where the focal length is 30 mm or more and less than 50 mm, and FIG. Show.
[0031]
The number of distance measuring points increases as the focal length decreases and decreases as the focal length increases. This is because the shorter the focal length, the wider the angle of view, and there is a strong demand to select one distance measuring point from more distance measuring points. Conversely, the longer the focal length, the smaller the angle of view and the less This is because selection from a distance measuring point is sufficient. Further, since the cosine error is more likely to occur as the focal length is shorter, if a large number of distance measuring points are arranged, an operation of shaking the camera after focusing once is unnecessary, and the cosine error is less likely to occur. On the other hand, since the cosine error is less likely to occur as the focal length becomes longer, it is not necessary to force the photographer to perform a complicated distance measuring point selection operation. In FIGS. 5B and 5C, the number of distance measuring points is the same, but the distance between the distance measuring points is larger when the focal length is shorter. This is to prevent the camera from shaking greatly by increasing the distance between the distance measuring points.
[0032]
Specifically, as shown in FIG. 5, as the focal length of the photographic lens is longer (telephoto), the focus point located at the center of the photographic area is determined as a manually selectable focus point. As the focal length of the lens becomes shorter, it is possible to select a distance measuring point far from the center of the photographing region as a manually adjustable distance measuring point. Therefore, as the focal length of the photographic lens decreases, the distance between two distance measuring points that are the farthest from the center of the image capturing area among the manually selectable distance measuring points increases.
[0033]
As described above, among the distance measuring points arranged in the same direction, the distance (S) between the two distance measuring points farthest from the center of the imaging region is made closer as the focal distance becomes longer (the distance becomes shorter as the focal distance becomes shorter). Thus, it is possible to efficiently arrange the ranging points so as to cover the subject image appropriately. This distance is a distance S _1H between J and K farthest from D corresponding to the center of the imaging region in the horizontal direction of FIG. 5B, and a distance S _1V between C and E in the vertical direction of FIG. It is. Similarly, this distance is the distance S _2H between I and L and the distance S _2V between B and F in the horizontal direction and vertical direction in FIG. 5C, and in the horizontal direction and vertical direction in FIG. is the distance H and M S _3H, distance between a and G S _3V. At this time, S _1H <S _2H <S _3H and S _1V <S _2H <S _3V are satisfied.
[0034]
Further, distance measuring points are selected such that the distances between adjacent distance measuring points are substantially equal. For example, in the state of FIG. 5B, the adjacent distance measuring points are selected so as to be substantially D ₁ . FIG. 5 (c), the 5 likewise the case of (d), none of the adjacent distance measuring point is set such that D ₂ (provided that D _2> D _1).
[0035]
By setting the distance (D) between adjacent distance measuring points to be equal, and increasing the distance D as the focal length is shorter, the number of distance measuring points that can be manually selected quickly and accurately by the user can be reduced to a necessary and sufficient number. it can.
[0036]
The focus detection point display in the viewfinder is automatically changed as follows. FIG. 6 is a flowchart of processing for detecting the focal length of the photographing lens and changing the distance measuring point display in the finder based on the detected focal length. When the camera is turned on by the photographer (STEP 1), the focal length information of the photographing lens is read from the lens ROM by the CPU and the focal length f is detected (STEP 2).
[0037]
First, the CPU determines whether or not the detected focal length is 85 mm or more (STEP 3). When it is determined that the focal length is 85 mm or more (YES in STEP 3), based on the information stored in the table 34, a drive signal for lighting the LED at the D position from the CPU to the superimpose block is generated. Sent (STEP4). Based on the drive signal from the CPU, the superimpose block lights only the LED at position D in green (STEP 5).
[0038]
Next, when it is determined in STEP 2 that the detected focal length is not 85 mm or longer (NO), it is determined whether or not the focal length is 50 mm or longer and less than 85 mm (STEP 6). When it is determined that the focal length is 50 mm or more and less than 85 mm (YES in STEP 6), the positions of C, D, E, J, and K from the CPU to the superimpose block based on the information stored in the table 34 A drive signal for turning on the LED is sent (STEP 7). The superimpose block lights only the LEDs at positions C, D, E, J, and K based on a drive signal from the CPU in green (STEP 8).
[0039]
Further, in STEP 6, when it is determined that the detected focal length is not 50 mm or more and less than 85 mm (NO), it is determined whether or not the focal length is 30 mm or more and less than 50 mm (STEP 9). When it is determined that the focal length is 30 mm or more and less than 50 mm (YES in STEP 9), the positions of B, D, F, I and L from the CPU to the superimpose block based on the information stored in the table 34 A drive signal for turning on the LED is sent (STEP 10). The superimpose block lights only the LEDs at positions B, D, F, I and L in green based on the drive signal from the CPU (STEP 11).
[0040]
If it is determined in STEP 9 that the detected focal length is not 30 mm or more and less than 50 mm (NO), it is determined whether or not the focal length is less than 30 mm (STEP 12). When it is determined that the focal length is less than 30 mm (YES in STEP 12), A, C, E, G, H, J, K are transferred from the CPU to the superimpose block based on the information stored in the table 34. And a drive signal for lighting the LED at the position of M is sent (STEP 13). Based on the drive signal from the CPU, the superimpose block lights only the LEDs at positions A, C, E, G, H, J, K and M in green (STEP 14).
[0041]
Furthermore, when it is determined in STEP 12 that the focal length is not less than 30 mm (NO), the focal length is detected again (returns to STEP 2).
[0042]
The photographer can select an arbitrary point from the distance measuring points displayed as described above. Selection of a distance measuring point is performed by operating a circular distance measuring point setting button 3 (ranging point selection means) provided on the back or top surface of the camera. The distance measuring point setting button 3 is displayed with arrows indicating the respective directions at the upper, lower, left and right end portions, and the distance measuring point in the finder can be moved by pressing the arrow. The distance measuring point can be determined by sequentially moving the distance measuring point and pressing the center portion of the distance measuring point setting button when the desired distance measuring point is reached. When the center portion of the ranging point setting button is pressed, the CPU 21 (ranging point selection means, display change means) causes the superimpose block 35 to light the LED 71 at the position corresponding to the ranging point in red. Send the drive signal. Upon receiving this drive signal, the superimpose block (display changing means) 35 lights the LED 71 at a position corresponding to the distance measuring point in red. When the photometry switch 43 is pressed, the CPU 21 sends a drive signal to the AF drive mechanism 41 to perform focus adjustment at the distance measuring point.
[0043]
The following modifications are possible for this embodiment.
In the present embodiment, the colors of the LED light are two colors, green and red, but other color combinations are possible. It is also possible to turn on only the selected distance measuring points and turn off the remaining distance measuring points. Further, the luminance of the LED may be changed between the selected distance measuring point and the remaining distance measuring points. Of course, the light source may be other than LEDs.
[0044]
In the present embodiment, the same number of light sources (LEDs) as that of all the distance measuring points are arranged in a one-to-one correspondence with each distance measuring point, but the number of light sources may be smaller than the number of distance measuring points. Well, it may be one. In this case, a shutter or the like corresponding to each distance measuring point may be provided.
[0045]
Although the present embodiment is applied to a digital camera, the present invention is not limited to a camera that records an image on a CCD, but can be applied to a single-lens reflex camera in general, including a camera that records an image on a silver salt film.
[0046]
In the present embodiment, the lens barrel L mounted on the camera body has been described as a zoom lens. However, the zoom lens may be an electric lens or a manual lens, and may be a plurality of single focus lenses having different focal lengths.
[0047]
Further, the present invention can be applied to a lens-integrated camera having a zoom lens and a photographing lens capable of switching a focal length in the camera body instead of the interchangeable lens camera.
[0048]
Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the above embodiment, and can be improved or changed within the scope of the purpose of the improvement or the idea of the present invention.
[0049]
【The invention's effect】
As described above, according to the present invention, since the number of distance measuring points is changed according to the focal length, the operation for selecting a desired distance measuring point from a number of distance measuring points is facilitated. A focus camera can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view of an autofocus camera according to an embodiment of the present invention as viewed from the left rear.
FIG. 2 is a side view of the inside of a zoom autofocus digital camera body according to an embodiment of the present invention.
FIG. 3 is a block diagram of a camera according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating all distance measuring points that can be displayed on a viewfinder.
5A is a focal length of 85 mm or more, FIG. 5B is a focal length of 50 mm or more and less than 85 mm, FIG. 5C is a focal length of 30 mm or more and less than 50 mm, and FIG. It is a finder display showing available distance measuring points in the case.
FIG. 6 is a flowchart of processing for detecting a focal length of a photographing lens and changing a distance measuring point display in the finder based on the detected focal length.
[Explanation of symbols]
A to M AF point 3 AF point setting button (Focus point selection part)
6 photographic lens 14 finder optical system 21 CPU (control means, light source drive unit, display change means)
33 Lens ROM (focal length detection means)
35 Superimpose block (light source drive, display change means)
71 LED

Claims (10)

An auto-focus camera that allows the photographer to select one of several AF points,
A finder capable of displaying the positions of the plurality of distance measuring points by light emitted from a light source;
A focal length detecting means for detecting a focal length of the photographing lens;
A light source driving unit that selectively drives all or part of the light sources corresponding to the plurality of distance measuring points;
Control means for driving the light source driving unit in accordance with the focal length of the photographing lens detected by the focal length detection means to change the number or / and the arrangement of the distance measuring points displayed on the finder;
I have a,
The number of the distance measuring points increases as the focal length becomes shorter and decreases as the focal length becomes longer, and the distance between the distance measuring points is larger when the focal length is shorter . The autofocus camera according to claim 1, wherein the photographing lens is detachably attached to the camera body. Information on the focal length of the photographic lens is stored in a storage medium provided in the photographic lens, and the focal length detection unit reads out information on the focal length of the photographic lens from the storage medium. The autofocus camera according to claim 1 or 2, wherein a focal length is detected. Further, a distance measuring point selection unit for the photographer to select one distance measuring point from the plurality of distance measuring points displayed on the viewfinder, and the photographer operates the distance measuring point selection unit. 4. The auto switch according to claim 1, further comprising: a display changing unit that, when the one distance measuring point is selected, makes the display of the selected distance measuring point different from the display of the other distance measuring points. 5. Focus camera. The autofocus camera according to any one of claims 1 to 4, wherein the light source is a two-color LED. 6. The autofocus camera according to claim 1, wherein the light source is a plurality of light sources corresponding to the plurality of distance measuring points on a one-to-one basis. The autofocus camera according to any one of claims 1 to 6, wherein as the focal length of the photographing lens becomes shorter, a manually selected distance measuring point farther from the center of the photographing region can be selected. The autofocus camera according to any one of claims 1 to 7, wherein the plurality of distance measuring points are arranged symmetrically with respect to a central portion of the imaging region. The autofocus camera according to any one of claims 1 to 8, wherein a distance between two distance measuring points farthest from the center of the imaging region increases as the focal length of the imaging lens becomes wider. The autofocus camera according to any one of claims 1 to 9, wherein the plurality of distance measuring points have substantially the same distance between two adjacent distance measuring points.

Images