JP4112312B2 - Digital camera with zoom function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera with a zoom function using both a conversion lens and an electronic zoom.
[0002]
[Prior art]
In recent years, digital cameras have become more sophisticated, and high-power zoom is required. On the other hand, low cost and downsizing are also demanded, and it is impossible to use an expensive optical zoom lens with high magnification. Therefore, for example, in a camera with a zoom function described in Japanese Patent Laid-Open No. 6-181531, or a video camera described in Japanese Patent Laid-Open No. 8-18842, a conversion lens for switching a focal length (hereinafter simply referred to as a conversion lens). A high magnification zoom function is realized by combining a lens) and electronic zoom.
[0003]
As is well known, the electronic zoom is a method of performing an artificial zoom by electronically enlarging an image obtained by a CCD. Unlike an optical zoom lens, the image quality deteriorates when enlarged, but the optical zoom lens. In the same manner as described above, the photographing magnification can be continuously changed. On the other hand, as is well known, the conversion lens is a lens that is inserted into and removed from the optical axis of the master lens to switch the focal length. Unlike the optical zoom lens that moves the moving lens on the optical axis, the conversion lens has a simple structure and is high in height. While switching to the magnification becomes possible, the magnification cannot be changed continuously. In the invention described in the above publication, a smooth zoom function is realized by complementing the discontinuity of the focal length due to the conversion lens with the electronic zoom. In addition, a relatively low-cost low-power zoom lens is used as a master lens, and a high-power zoom function is realized by combining these lenses.
[0004]
[Problems to be solved by the invention]
However, when the conversion lens is inserted into and removed from the optical axis, a momentary interruption occurs, so that it is not possible to take a picture at the switching point. In addition, if the zoom amount is repeatedly enlarged and reduced in the vicinity of this switching point, momentary interruptions frequently occur and framing is difficult.
[0005]
The present invention is for solving the above-described problems, and has a zoom function that is easy to perform framing in the vicinity of a point where the focal length is switched by the insertion / removal of the conversion lens without the position where the photographing cannot be performed by the conversion lens. The purpose is to provide a digital camera.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the digital camera with a zoom function according to the present invention can be inserted / removed between a master lens and an insertion position inserted on the optical axis of the master lens and a position retracted from the insertion position. A multifocal lens composed of a plurality of conversion lenses provided on the camera and a plurality of the conversion lenses are individually inserted / removed to switch the focal length of the multifocal lens and switch the optical photographing magnification at a plurality of switching points. Optical magnification switching means, imaging means for photoelectrically converting a subject image formed by the multifocal lens to obtain a photographed image, and electronic zoom for electronically enlarging a part of the photographed image to perform electronic zoom processing And switching of the optical photographing magnification and executing an electronic zoom process before and after the plurality of switching points, The total zoom magnification that combines the imaging magnification of the multifocal lens and the electronic zoom magnification is continuously changed from the wide-angle end to the telephoto end, and a plurality of switching points of the optical imaging magnification are set when the total zoom magnification is enlarged. Zoom control means for shifting at the time of reduction, storage means for storing data relating to lens brightness, aberration characteristics and peripheral dimming characteristics as lens characteristics at each focal length of the multifocal lens, and obtained at each focal length Image correction means for correcting the captured image based on the insertion / removal state of each of the plurality of conversion lenses and the data so that the obtained image quality is substantially uniform.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an electrical configuration of a digital camera 2 embodying the present invention. The digital camera 2 has a zoom function using both the multifocal lens 3 and an electronic zoom. The multifocal lens 3 includes a master lens 4, a first conversion lens 5, and a second conversion lens 6, and is held by a lens barrel 7. These first and second conversion lenses 5 and 6 have an insertion position (solid line in the figure) inserted on the optical axis X of the master lens 4 and a retreat position (two-dot chain line in the figure) retreating from the insertion position. Are provided so as to be freely inserted and removed. Each of these conversion lenses 5 and 6 is a teleconversion lens that increases the photographing magnification by insertion. The multifocal lens 3 can switch the optical magnification to, for example, × 1, × 3, or × 6 times by changing the focal length discontinuously by the combination of these three lenses. Then, before and after the focal length switching point by inserting / removing the conversion lenses 5 and 6, the electronic zoom processing is performed to continuously change the total zoom magnification including the optical photographing magnification and the electronic zoom magnification.
[0009]
The controller 8 is connected to each part of the camera via the data bus 28 and the like, and controls the entire digital camera 2 based on the input signal input from the key input unit 10. The key input unit 10 is provided with an enlargement zoom button 11, a reduction zoom button 12, a shutter button 13 used for a shutter release operation, and the like. The ROM 35 stores programs, various setting information, and the like.
[0010]
A zoom counter 14 and an LUT (Look Up Table Memory) 15 are connected to the controller 8. The zoom counter 14 counts up the counter value according to the operation amount when the enlargement zoom button 11 is operated, and similarly counts down when the reduction zoom button 12 is operated. The controller 8 specifies the zoom amount desired by the user based on the counter value. The LUT 15 stores the correspondence between the zoom amount, the switching point of the optical magnification of the multifocal lens, and the electronic zoom magnification. The controller 8 determines whether or not it is necessary to switch the optical magnification of the multifocal lens from the LUT 15 according to the specified zoom amount, and determines the electronic zoom magnification.
[0011]
The lens barrel 7 incorporates a focusing mechanism 16 for adjusting the focus and a conversion lens inserting / removing mechanism 17 for inserting and removing the first and second conversion lenses 5 and 6. The focusing mechanism 16 and the conversion lens switching mechanism 17 are each composed of a mechanical mechanism and a motor, and are driven and controlled by a driver 18 connected to the controller 8. By this conversion lens insertion / removal mechanism 17, the first and second conversion lenses 5, 6 are respectively moved between the insertion position (two-dot chain line in the figure) and the retracted position (solid line in the figure).
[0012]
Behind the lens barrel 7 is a CCD 21 that photoelectrically converts subject light that has passed through the taking lens and images it. As is well known, the CCD 21 outputs an analog signal for each pixel corresponding to the accumulated charge amount of each cell. This analog signal is input to a correlated double sampling circuit (CDS) 22 to remove noise, amplified by an amplifier (AMP) 23, and input to an A / D converter 24. The A / D converter 24 converts an analog signal into digital data. The digitized image data is input to the image signal processing unit 25 and then temporarily written in the RAM 29.
[0013]
The image signal processing unit 25 includes various circuits such as an image quality correction circuit, an AE circuit, and an AF circuit. Each circuit accesses the image data written in the RAM 29 and performs various image processing. The image quality correction circuit performs various correction processes such as gamma correction and sharpness correction. The AE circuit measures the luminance value based on the image data and determines the exposure value. The controller 8 adjusts a diaphragm or the like (not shown) according to the exposure value. The AF circuit checks the contrast of the image data and detects the focal position. Then, the focusing mechanism 16 is driven based on the detected focal position.
[0014]
The electronic zoom unit 27 performs electronic zoom processing on the image output from the image signal processing unit 25 according to the electronic zoom magnification determined by the controller 8. Then, the image data subjected to the image processing and the electronic zoom processing is compressed by the compression / decompression unit 32 in, for example, a compression format of JPEG (Joint Photographic Experts Group). The JPEG compressed image is recorded on the memory card 34 by the media controller 33. In the reproduction mode, after the compression / decompression unit 32 performs an expansion process on the captured image read from the memory card 34, this data is written in the video memory 30 and reproduced and displayed on the LCD 31.
[0015]
The CCD 21 captures a through image to be displayed on the LCD 31 as a subject confirmation image. The captured through image is converted into digital data, subjected to simple image processing by the image signal processing unit 25, electronic zoom processing by the electronic zoom unit 27, and writing into the video memory 30. . The through image is converted into an analog composite signal by an LCD driver (not shown) and output to the LCD 31. This live view is updated several tens of times per second. The user can check the subject in real time using the through image.
[0016]
Since the digital camera 2 uses the first and second conversion lenses 5 and 6, instantaneous interruption occurs at the point where the conversion lenses 5 and 6 are inserted and removed. Since shooting is not possible at the position where the instantaneous interruption occurs, the digital camera 2 shifts the switching points of the conversion lenses 5 and 6 between the zoom zoom and the zoom zoom.
[0017]
FIG. 2 is a graph showing the relationship between the zoom amount specified by the controller 8 according to the zoom operation amount of the user and each of the optical photographing magnification, the electronic zoom magnification, and the total zoom magnification. These relationships are stored in the LUT 15, and the controller 8 refers to the LUT 15 according to the zoom amount, and performs switching of the optical photographing magnification and electronic zoom processing. FIG. 2C is a graph showing the relationship between the zoom amount and the total zoom magnification. The optical photographing magnification and the electronic zoom magnification are determined so as to match the total zoom magnification. FIG. 2B is a graph showing the relationship between the zoom amount and the electronic zoom magnification. The electronic zoom magnification is determined such that the total zoom magnification changes continuously by complementing the optical photographing magnification that is switched discontinuously.
[0018]
FIG. 2A is a graph showing the relationship between the zoom amount and the optical photographing magnification. A position A1 is an insertion point of the first conversion lens during zooming, and a position B1 is a retraction point of the first conversion lens during zooming reduction. The position A2 is an insertion point of the second conversion lens at the time of zooming in, and the position B2 is a retraction point of the second conversion lens at the time of zooming out. In this way, the switching points (insertion point and retraction point) of each conversion lens are shifted between when zooming in and when zooming out.
[0019]
When the power is turned on, the digital camera 2 resets the zoom counter 14 to adjust the zoom amount to the wide end that is the initial position. At the wide end, as shown in FIG. 2A, both the first and second conversion lenses 5 and 6 are in the retracted position, and the optical photographing magnification is the lowest. Further, as shown in FIG. 2B, the electronic zoom magnification is also equal. For this reason, as shown in FIG. 2C, the total zoom magnification obtained by combining the optical photographing magnification and the electronic zoom magnification is also equal.
[0020]
When the enlargement zoom button 11 is operated, the zoom amount is up-counted according to the operation amount, and enlargement zoom is performed. At this time, the through image of the LCD 31 is also enlarged. When enlargement zoom is performed from the wide end, first, the electronic zoom magnification is gradually enlarged. This enlargement electronic zoom processing is performed until the total zoom magnification at the position A1 is reached. When the zoom amount reaches position A1, the first conversion lens 5 is inserted, and the optical photographing magnification is increased. The electronic zoom magnification is reduced simultaneously with the insertion by an amount corresponding to the increase in the optical photographing magnification. When the zoom amount is further enlarged from this position A1, the electronic zoom magnification is again enlarged. The enlargement electronic zoom process is performed until the total zoom magnification at the position A2 is reached. Since the second conversion lens 6 is inserted at this position A2, the optical photographing magnification is further enlarged, and the electronic zoom magnification is reduced at the same time as the insertion by the enlarged amount. When the zoom amount is further enlarged from this position A2, the electronic zoom magnification is again enlarged and reaches the telephoto end.
[0021]
On the other hand, when the reduction zoom button 12 is operated from the tele end, the zoom amount is down-counted according to the operation amount, and reduction zoom is performed. When the reduction zoom is performed from the tele end, first, the electronic zoom magnification is gradually reduced. This reduction electronic zoom processing is performed until the total zoom magnification at the position B2 is reached. When the zoom amount reaches position B2, the second conversion lens 6 is retracted, and the optical photographing magnification is reduced. At the same time as the retreat, the electronic zoom magnification is enlarged by the reduction. When the zoom amount is further reduced from B2, reduction electronic zoom processing is performed again until the total zoom magnification at position B1 is reached. When the zoom amount reaches the position B1, the first conversion lens 5 is retracted, and the optical photographing magnification is reduced. At the same time as the retreat, the electronic zoom magnification is enlarged by the reduction. When the zoom amount is further reduced, a reduction zoom process is performed to reach the wide end.
[0022]
By performing such optical photographing magnification switching and electronic zoom processing, the total zoom magnification can be continuously changed. In addition, a through image corresponding to the total zoom magnification is displayed on the LCD 31. Since this through image is enlarged or reduced according to the zoom amount, the user can perform framing through this through image. At the switching point of each of the first and second conversion lenses 5, the through image is momentarily interrupted by the insertion / removal of the lens.
[0023]
Further, by shifting the switching points of the conversion lenses 5 and 6 between enlargement and reduction, no instantaneous interruption occurs at the position where the instantaneous interruption occurs at one of the enlargement or reduction. , The position that can not be taken can be eliminated. When performing framing, enlargement zoom and reduction zoom are often repeated in the vicinity of a desired zoom amount. For example, when framing is performed in the vicinity of the position A1, enlargement zoom and reduction zoom are repeated in this vicinity. Even in such a case, an instantaneous interruption occurs at the position A1 at the time of enlargement, but no instantaneous interruption occurs at the time of reduction. Therefore, the number of occurrences of the instantaneous interruption is reduced and framing is facilitated. Of course, for example, if the enlargement zoom and the reduction zoom are repeated beyond the interval between the position B1 and the position A1, an interruption occurs at both the enlargement and reduction. Therefore, the intervals between the positions B1 and A1, and the positions B2 and A2 are appropriately determined so that instantaneous interruption does not occur frequently in consideration of the zoom amount (operation amount) performed during framing.
[0024]
Next, the operation of this embodiment will be described. When the digital camera 2 is turned on and the shooting mode is selected, a through image is displayed on the LCD 31. The user performs framing while watching this through image. When the enlargement zoom button 11 and the reduction zoom button 12 are pressed, the count value of the zoom counter 14 is counted up or down. The controller 8 specifies the zoom amount from the count value, and switches the first and second conversion lenses 5 and 6 and performs electronic zoom processing according to the zoom amount while referring to the LUT 15.
[0025]
The switching points of the conversion lenses 5 and 6 are shifted at the time of enlargement and reduction, and even if the zoom amount is repeatedly enlarged and reduced in the vicinity of the switching point, the number of occurrences of instantaneous interruption is small. Easy to do. For example, when framing is performed in the vicinity of the position A1, the first conversion lens 5 is inserted at the position A1 during zooming, but the first conversion lens 5 is not retracted even when passing through the position A1 during reduction. Therefore, at the position A1, an instantaneous interruption occurs only at the time of enlargement, and no instantaneous interruption occurs at the time of reduction. When framing is performed in the vicinity of the position B1, the first conversion lens 5 is retracted at the position B1 during the reduction zoom, but not inserted during the enlargement, contrary to the position A1. Therefore, at the position B1, an instantaneous interruption occurs only at the time of reduction, and no instantaneous interruption occurs at the time of enlargement.
[0026]
When shooting at position A1, the zoom is adjusted to position A1 by reduction zoom, while when shooting at position B1, the zoom is set to position B1. As described above, since the switching points of the conversion lenses 5 and 6 are shifted between the enlargement time and the reduction time, photographing can be performed at each switching point (positions A1, B1, A2, and B2).
[0027]
When the shutter button 13 is pressed after the framing is completed, an image is recorded at a total zoom magnification corresponding to the zoom amount.
[0028]
When the conversion lens is used as in the above embodiment, the lens characteristics of the multifocal lens 3 change due to the insertion / removal of the conversion lens, and therefore when the conversion lens is inserted and when the conversion lens is retracted. Then the image quality will change. Therefore, characteristic data of the multifocal lens 3 when the conversion lens is inserted and when the conversion lens is retracted may be stored, and image correction may be performed based on the characteristic data.
[0029]
In that case, characteristic data, that is, data such as lens brightness, various aberration characteristics, and peripheral light attenuation characteristics are stored in advance in the ROM 35, for example. The image signal processing unit 25 reads characteristic data from the ROM 35 according to the insertion / removal of each conversion lens, and electronically corrects the image accordingly. In this way, uniform image quality can be ensured even when the conversion lens is inserted and removed.
[0030]
In particular, in the digital camera 2, the switching point of the conversion lens is shifted between the enlargement zoom and the reduction zoom, so even if the same total zoom magnification is used, whether the magnification is adjusted by the enlargement zoom or the reduction zoom. Depending on the lens characteristics. For example, when adjusting to the total zoom magnification corresponding to the middle between the position B1 and the position A1, since the image is enlarged by electronic zoom processing at the time of enlargement, the first conversion lens is not inserted, but when adjusting by reduction zoom, A first conversion lens is inserted. For this reason, the lens characteristics are different at the time of enlargement and at the time of reduction. For this reason, as described above, such a problem can be solved by executing the image correction according to the lens characteristics.
[0031]
In the above embodiment, the multifocal lens is composed of three lenses, one master lens and two conversion lenses. However, the number of these lenses may be changed as appropriate.
[0032]
In the above embodiment, the master lens is described as an example of a single lens, but an optical zoom lens may be used as the master lens. According to this, zooming is performed with an optical zoom lens up to a certain photographing magnification, and a conversion lens and an electronic zoom are used to obtain a photographing magnification exceeding that. Of course, although the example of the teleconversion lens has been described, a wide conversion lens that switches the focal length to the wider angle side may be used.
[0033]
Furthermore, in the above embodiment, an example of a digital camera has been described. However, the present invention can be used for various cameras such as a digital video camera as long as it is a type having a multifocal lens and electronic zoom means.
[0034]
【The invention's effect】
As described above, according to the digital camera with a zoom function of the present invention, it is possible to insert / remove between the master lens and the insertion position inserted on the optical axis of the master lens and the position retracted from the insertion position. An image formed by a multifocal lens, a multifocal lens comprising a conversion lens provided in the optical system, an optical magnification switching means for switching the focal length of the multifocal lens by inserting and removing the conversion lens, and switching an optical photographing magnification. An imaging means for photoelectrically converting a subject image to obtain a photographed image, an electronic zoom means for electronically enlarging a part of the photographed image to perform electronic zoom processing, and switching of the optical photographing magnification and controlling the switching point By performing electronic zoom processing before and after, the total zoom magnification that combines the shooting magnification of the multifocal lens and the electronic zoom magnification is at the wide-angle end. Zoom control means for continuously changing from the telephoto end to the telephoto end, and this zoom control means shifts the switching point of the optical photographing magnification between when the total zoom magnification is enlarged and when it is reduced, thereby eliminating the position where photographing is impossible. Can do. Further, even when the enlargement zoom and the reduction zoom are repeated in the vicinity of the switching point, the number of occurrences of instantaneous interruption is reduced, so that framing is easy.
[0035]
A storage unit that stores data on lens characteristics at each focal length of the multifocal lens; and an image correction unit that corrects the captured image based on the data so that the image quality obtained at each focal length is substantially uniform. Therefore, even when the lens characteristics are changed by changing the focal length, a uniform image can be obtained at each focal length.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of a digital camera embodying the present invention.
FIG. 2 is a graph showing a relationship between a zoom amount and each of an optical photographing magnification, an electronic zoom magnification, and a total zoom magnification of the digital camera embodying the present invention.
[Explanation of symbols]
2 Digital Camera 3 Multifocal Lens 4 Master Lens 5 First Conversion Lens 6 Second Conversion Lens 8 Controller 14 Zoom Zoom Counter 15 LUT
17 Lens switching mechanism 25 Image signal processing unit 27 Electronic zoom unit 35 ROM

Claims (1)

A multifocal lens comprising a master lens and a plurality of conversion lenses provided so as to be removably inserted between an insertion position inserted on the optical axis of the master lens and a position retracted from the insertion position;
Optical magnification switching means for switching the optical photographing magnification at a plurality of switching points by individually inserting and removing the plurality of conversion lenses and switching the focal length of the multifocal lens;
Imaging means for photoelectrically converting a subject image formed by the multifocal lens to obtain a captured image;
Electronic zoom means for electronically enlarging a part of the photographed image to perform electronic zoom processing;
The optical zoom magnification is controlled and electronic zoom processing is executed before and after the plurality of switching points, so that the total zoom magnification combining the imaging magnification and the electronic zoom magnification of the multifocal lens is changed from the wide-angle end to the telephoto end. Zoom control means that shifts a plurality of switching points of the optical photographing magnification at the time of enlargement and reduction of the total zoom magnification,
Storage means for storing data relating to lens brightness, aberration characteristics, and peripheral dimming characteristics as lens characteristics at each focal length of the multifocal lens;
Image correction means for correcting the captured image based on the insertion / removal state of each of the plurality of conversion lenses and the data so that the image quality obtained at each focal length is substantially uniform. Digital camera with zoom function.

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