JP3564733B2 - Digital still video camera - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a digital still video camera.
[0002]
[Prior art]
In recent years, a so-called digital still video camera, which captures a still image using an imaging means such as a CCD and records the obtained image data on a memory card using a semiconductor memory, is becoming popular. In a still video camera, photographed image data is generally compressed and stored in a memory card in order to effectively use the memory card for recording and storing photographed data.
[0003]
FIG. 5 is a block diagram showing an example of the configuration of such a conventional digital still video camera. In FIG. 5, reference numeral 501 denotes a photographing lens group for forming a subject image on an image pickup unit 505 described later; Reference numeral 503 denotes a mirror optical system for taking in the subject light into a photometry unit and a focus detection unit for exposure and focusing, 504 a shutter, and 505 an image pickup for converting the subject light taken in through a photographic lens group into an electric signal. And an image pickup means such as a CCD.
[0004]
Reference numeral 506 denotes an A / D conversion unit that converts the image signal photoelectrically converted by the imaging unit 505 into a digital signal. Reference numeral 507 denotes white balance correction, amplification, and γ for the image signal digitized by the A / D conversion unit 506. A signal processing unit for performing certain signal processing such as correction and contour enhancement; 508, a buffer memory for temporarily storing the image signal processed by the signal processing unit 507; 509, a compression circuit for compressing image data; Is a memory card for recording image data compressed by a.
[0005]
Reference numeral 515 is a focus detection unit, 516 is a photometry unit, and 520 is a control unit for controlling a shooting operation. Based on output signals from the focus detection unit 515 and the photometry unit 516, the control unit 520 performs focusing and proper exposure. The driving of the photographing lens group 501, the aperture 502 and the shutter 504 is controlled based on the calculation result, whereby the automatic focusing and the automatic exposure are performed.
[0006]
The degree of compression of the image data in the compression circuit 509, that is, the compression ratio is previously selected by a manual switch or the like (not shown), and the photographer selects a desired compression ratio with the switch and performs photographing. .
[0007]
[Problems to be solved by the invention]
By the way, in recent years, as can be seen not only in so-called compact cameras but also in auto-focusing and auto-exposure of single-lens reflex cameras, camera shooting has been carried out so that higher quality images can be obtained with simpler operations. There is a remarkable tendency to simplify and simplify operations.
[0008]
In such a situation, in the conventional digital still video camera as described above, as described above, there is an annoyance that the user has to operate a switch to select a data compression ratio before shooting. Was.
[0009]
On the other hand, in order to eliminate such inconvenience, the image data digitized by the A / D converter 506 and stored in the buffer memory 508 is analyzed to automatically determine the compression ratio, or In some cases, the image data is partially extracted from the image data 508, the image data is compressed, the result is fed back, and the compression is repeated to determine the optimum compression ratio. In any case, the optimum compression ratio is calculated. It takes a long time to perform this operation, so that it is not possible to take a picture quickly. In addition, it is necessary to operate a compression circuit to determine the compression ratio, which consumes power.
[0010]
The present invention has been made to solve the problem of the conventional digital still video camera, and provides a digital still video camera capable of automatically determining the compression ratio of image data in a short time and with low power. With the goal.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present application is directed to an image pickup unit that converts a subject light into an electric signal, a photographing optical system that forms a subject image on the image pickup unit, and the photographing optical system. Focus detection means for focusing the image, analog-to-digital conversion means for converting an electric signal photoelectrically converted by the imaging means into a digital signal, and compressing image data digitized by the analog-to-digital conversion means In a digital still video camera including a compression unit and a recording unit that records image data compressed by the compression unit, the compression unit includes a high-frequency component included in an output signal of a photoelectric conversion element in the focus detection unit. this is intended the amount of higher to increase a compression ratio of the data compressor often, to compress the image data at a compression rate in accordance with the output signal Those of the digital still video camera according to claim.
[0015]
According to a second aspect of the present invention, there is provided an imaging unit for converting subject light into an electric signal, a photographic optical system for forming a subject image on the imaging unit, and a focus for focusing the photographic optical system. Detecting means, analog-to-digital conversion means for converting an electric signal photoelectrically converted by the imaging means into a digital signal, compression means for compressing image data digitized by the analog-to-digital conversion means, and compression means And a recording means for recording image data compressed by a digital still video camera, wherein image quality is reduced by compressing image data until the image quality of a subject image captured by the image capturing means is substantially maintained. Priority mode and image data such that the data length of the image data is substantially constant irrespective of the image quality of the subject image picked up by the image pickup means. It has proposed that further comprising a mode selecting means for switching between the data length priority mode to compress.
[0016]
When the mode selecting means selects the image quality priority mode, the compressing means lowers the compression ratio as the amount of the high frequency component included in the output signal of the photoelectric conversion element in the focus detecting means increases. When the mode selection means selects the data length priority mode, the compression means controls the compression ratio as the amount of high frequency components contained in the output signal of the photoelectric conversion element in the focus detection means increases. The digital still video camera is characterized in that the image data is compressed at a compression ratio according to an output signal so that the image data is controlled to be high.
[0017]
[Action]
In the present invention configured as described above, a subject image is formed on the imaging unit by the imaging optical system, and the imaging unit converts the subject light into an electric signal. This electric signal is converted into a digital signal by the analog-digital conversion means, and the digitized image data is further compressed by the compression means.
[0018]
Here, based on an output signal from the focus detection unit, the compression unit compresses the image data at a compression rate corresponding to the output signal. Then, the compressed image data is recorded in the recording means.
[0021]
In the invention described in claim 1, the compression unit controls the compression ratio of the data compression unit to be higher as the amount of the high frequency component included in the output signal of the photoelectric conversion element in the focus detection unit is larger. That is, since image data having any image quality is compressed to a fixed data length and stored in the recording medium, the number of frames of the image that can be stored in the recording medium is always constant, and the usability is good.
[0022]
Further, in the invention according to the second aspect , an image quality priority mode in which image data is compressed and stored in the recording medium until image quality of a subject image captured by the imaging unit is substantially maintained, There is further provided mode selection means for switching between a data length priority mode for compressing image data so that the data length of the image data is substantially constant regardless of the image quality of the captured subject image.
[0023]
This mode selection means can be freely switched according to the photographer's needs. If the photographer wants to convert high-quality image data into a high-quality reproduced image, the mode selection means should be set to image quality priority. Switch to mode. When the mode selection unit selects the image quality priority mode, the compression unit controls the compression ratio to be lower as the amount of the high frequency component included in the output signal of the photoelectric conversion element in the focus detection unit is larger. A reproduced image whose quality is not impaired can be obtained.
[0024]
When the photographer wants to keep the number of frames of the image data stored in the recording medium constant, the mode selecting means may be switched to the data length priority mode. When the mode selection means selects the data length priority mode, the compression means controls the compression ratio higher as the amount of the high frequency component included in the output signal of the photoelectric conversion element in the focus detection is larger. Therefore, the image data length of one screen is constant regardless of the image quality of the subject image picked up by the image pickup means. Therefore, the number of frames of the image data stored in the recording medium is constant.
[0025]
As described above, in the digital still video camera according to the present invention, the compression ratio of the image data is determined based on the output signal of the focus detection means. A switch operation for selecting a compression ratio is not required. Furthermore, since the compression ratio is not determined by analyzing the image data itself, and the compression unit is not operated to determine the appropriate compression ratio, the captured image data can be obtained in a short time and with low power. Appropriate compression can be performed.
[0026]
【Example】
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a digital still video camera according to one embodiment of the present invention. FIGS. 2 and 3 are block diagrams showing a part of the configuration of the digital still video camera in more detail. 4 is a flowchart showing the operation of the digital still video camera of the embodiment.
[0027]
As shown in FIG. 1, a digital still video camera according to the present embodiment is similar to the conventional digital still video camera shown in FIG. A mirror optical system 103 for taking light into the photometry unit 116 and the focus detection unit 115, a shutter 104, an imaging unit 105 including imaging means such as a CCD, an A / D conversion unit 106 for converting an image signal into a digital signal, A signal processing unit 107 for performing certain signal processing such as white balance correction, amplification, γ correction, and edge enhancement on the image signal digitized by the D conversion unit, and temporarily outputs the image signal processed by the signal processing unit 107. A buffer memory 108 for temporarily storing image data; and a compression processing unit 109 for compressing image data.
[0028]
The control unit 120 further includes a focus detection unit 115, a photometry unit 116, and a control unit 120 that controls a shooting operation. The control unit 120 performs focusing and proper exposure based on output signals from the focus detection unit 115 and the photometry unit 116. And the drive of the photographing lens group 101, the aperture 102 and the shutter 104 is controlled based on the calculation result, whereby the automatic focusing and the automatic exposure are performed. Then, the captured image data is recorded on the memory card 110 after being compressed by the compression processing unit 109.
[0029]
On the other hand, the digital still video camera according to the present embodiment is different from the conventional digital still video camera in that the compression processing unit 109 that performs data compression when recording captured image data on the memory card 110 includes the focus detection unit. Data compression is performed at a compression rate corresponding to the output signal of the output signal 115.
[0030]
The case where the image quality priority mode is selected will be described below. The compression processing unit 109 performs a well-known quantization operation and code assignment operation on the digital image data, and performs a compression operation on the image data. The compression processing unit 109 includes a plurality of quantization tables for the quantization operation, specifically, three quantization tables (ie, a low compression rate (L), a medium compression rate (M), and a high compression rate (H )), And the final data compression ratio is determined by selecting one of the quantization tables.
[0031]
The selection of the image quality priority mode or the data length priority mode in the compression ratio mode is performed by an external operation switch. When both the compression mode selection switch 123 and the compression coefficient selection switch 124 of FIG. 1 are turned on (H), the image quality priority mode is set, the compression mode selection switch 123 is turned on (H), and the compression coefficient selection switch 124 is turned on. When switched to OFF (L), the mode is the data length priority mode, and the mode can be selected.
[0032]
Here, the image quality priority mode means that the image quality of the subject image captured by the imaging unit 105 is compressed and stored in the memory card 110 while maintaining the image quality of the subject image as much as possible. Mode. Accordingly, high-quality image data is compressed at a low compression ratio and stored in the memory card 110, so that the image data length of the position screen is not constant.
[0033]
On the other hand, the data length priority mode is a mode in which the image data length of one screen is made as constant as possible and stored in the memory card 110 irrespective of the image quality of the subject image captured by the imaging unit 105. Therefore, the number of frames of an image recorded on one memory card is almost always the same, which is convenient.
[0034]
That is, as shown in FIG. 1, the digital still video camera includes a high-pass filter 140 that passes only a signal having a frequency component equal to or higher than a certain value among output signals of the photoelectric conversion element from a known focus detection unit 115. , An integrator 141 for integrating the signal passing through the high-pass filter 140, and a compression coefficient selection unit 142 for selecting a compression ratio based on an output signal from the integrator 141. The compression processing unit 109 compresses the image data based on the output signal from 142. Hereinafter, these will be described.
[0035]
First, FIG. 2 shows the configuration of the known focus detection unit 115 provided in the present embodiment. As shown in FIG. 2, the subject light from the mirror optical system 103 shown in FIG. An image is formed on the surface 201, and an arbitrary part of the subject image (generally, the center part of the subject area) is input to the photoelectric conversion element 204 by the CCD line sensor by the condenser lens 202 and the optical system 203. Then, an output signal from the photoelectric conversion element 204 by the CCD line sensor is input to the control unit 120 for focusing calculation and is input to the high-pass filter 140.
[0036]
The high-pass filter 140 allows only a signal having a frequency component equal to or higher than a certain value to pass, and the signal that has passed through the high-pass filter 140 is input to the integrator 141. The integrator 141 integrates the output signal of the high-pass filter 140 for each screen for a predetermined time based on a command from the control unit 120, and outputs the result to the compression coefficient selection unit 142 as a voltage value.
[0037]
FIG. 3 shows the configuration of the compression coefficient selection unit 142. In FIG. 3, reference numeral 342 denotes the compression coefficient selection unit 142, 341 denotes the integrator 141, and 309 denotes the compression processing unit 109. As shown, the compression coefficient selection unit 342 includes two comparators 342a and 342b, and reference voltage generators 343a and 343b connected to the two comparators 342a and 342b, respectively. Reference voltage generator 343a, 343b, respectively from the reference voltage _{V CC} in the camera A [V], for generating a reference voltage of B [V] (A> B ).
[0038]
The comparator 342a, the output voltage V _Y of the integrator 341 is input are added, the reference voltage A from the reference voltage generator 343a [V] is input is subtracted. Similarly, the comparator 342b, the output voltage V _Y of the integrator 341 is inputted by adding a reference voltage B from the reference voltage generator 343b [V] is input is subtracted. The outputs of the comparators 342a and 342b are input to the input ports P ₁ and P ₀ of the compression processing unit 309, respectively. The compression processing unit 309 uses the compression coefficients corresponding to the states of the input ports P ₁ and P ₀ to output image data. Compression.
[0039]
That is, the integrator 141 (341) of the output voltage _{V Y} and the reference voltage A _[V], but if one is on the relationship between _V Y> A (high-frequency component is great), the input port state _P 1 / P ₀ is, H / H, and the compression processing unit 109 (309) in this case is to compress the compression factor L (low compression ratio).
[0040]
In the case of A ≧ V _Y ≧ B, the state P ₁ / P ₀ of the input port becomes L / H, and the compression processing unit 109 (309) performs compression by the compression coefficient M (medium compression ratio). Do.
[0041]
Further, when there is a relationship of B> V _Y (the number of high-frequency components is small), the state P ₁ / P ₀ of the input port becomes L / L, and the compression processing unit 109 (309) sets the compression coefficient H (high). (Compression ratio).
[0042]
On the other hand, if the data length priority mode, the output voltage _{V Y} of the integrator 141 (341), the reference voltage A _[V], but the relationship between _V Y> A (high-frequency component is great) when In this case, the state P ₁ / P ₀ of the input port becomes H / H, and in this case, the compression processing unit 109 (309) performs compression using the compression coefficient H (high compression ratio).
[0043]
In the case of A ≧ V _Y ≧ B, the state P ₁ / P ₀ of the input port becomes L / H, and the compression processing unit 109 (309) performs compression by the compression coefficient M (medium compression ratio). Do.
[0044]
Further, when there is a relationship of B> V _Y (the number of high-frequency components is small), the state P ₁ / P ₀ of the input port becomes L / L, and the compression processing unit 109 (309) sets the compression coefficient L (low). (Compression ratio).
[0045]
Thus, in this third embodiment of a camera, when the data length priority mode, as the output voltage V _Y of the integrator 141 (341) is high, i.e., higher compression ratio greater the high frequency component Since the image data is selected to be high, for example, image data compression is automatically performed at a high compression ratio even for a fine image having many high frequency components.
[0046]
Furthermore, since the case is selected the image quality priority mode, as the output voltage V _Y of the integrator 141 is high, i.e., the the more high-frequency components often higher compression ratio is selected to be lower, for example, a high frequency component The image data is automatically compressed at a low compression ratio for a fine image having many images.
[0047]
This camera has a “compression auto mode” in which the compression ratio is automatically determined by the above-described compression coefficient selection unit 142 and the like, and compression is performed. There are two types of modes, a “compression manual mode” for selecting a compression ratio. Switching of this mode is instructed by the compression mode selection switch 123.
[0048]
That is, when the compression mode selection switch 123 is closed, the compression manual mode is set, and three types of compression coefficients (low compression coefficient L, medium compression coefficient M, high compression coefficient) are set by turning on / off the compression coefficient selection switches 124 and 125. The compression coefficient H) is selected, and the image data is compressed by the compression coefficient. On the other hand, if the compression mode selection switch 123 is opened, the compression auto mode is set, and the compression coefficient is automatically selected by the compression coefficient selection unit 142 and the image data is compressed by the selected compression coefficient. .
[0049]
Next, the operation of the camera of this embodiment will be described with reference to FIGS. 1, 3, and 4. FIG. In the camera of the present embodiment, a so-called half-pressing operation of the release button starts a shooting preparation operation. That is, when the half-press switch 121 is closed in step 401 of FIG. 4, photometry and focus detection operations are performed in steps 402 to 403. If the compression mode selection switch 123 is closed in step 404, step At 405, the compression coefficient set by the user is read.
[0050]
On the other hand, if the compression mode selection switch 123 is open, an appropriate compression coefficient according to the image is automatically selected in step 406 as described above.
[0051]
If the full-press switch 122 is closed in step 407, a series of photographing operations are performed in step 410, and the image data is compressed in step 411 by the read or selected compression coefficient. Is recorded on the memory card 110, and the shooting ends.
[0052]
On the other hand, if the full-push switch 122 remains open in step 407, the process proceeds to step 408, and if the half-press switch 121 is closed, steps 402 to 407 are repeated again. If the half-push switch 121 has been opened in step 408, the photographing preparation operation is terminated in step 409 after a predetermined time has elapsed.
[0053]
As described above, in the digital still video camera of the present embodiment, the compression processing unit 109 automatically selects the compression coefficient of image data based on the high frequency component of the output signal from the photoelectric conversion element of the focus detection unit 115. Because of the nature of the digital image data, or by extracting a part of the image data and operating the compression circuit, the data compression coefficient is selected based on the data length at that time. Coefficient selection work can be performed at high speed.
[0054]
As a result, the time from the start of the photographing operation to the storage of the image data in the memory card can be reduced as compared with the related art, and high-speed continuous shooting can be performed. Further, since it is not necessary to operate an A / D converter, a buffer memory, and a compression circuit for selecting a compression coefficient, power is not wasted.
[0055]
In the above-described embodiment, a series of photographing operations has been described with respect to so-called single mode (single-shot) photographing. However, in continuous mode (continuous photographing) photographing, photometry and focus detection are performed even during the photographing period. Since the operation is performed, the compression coefficient may be changed during the photographing period, or the compression coefficient may be fixed during continuous shooting. In addition, the compression coefficient described in the present embodiment may be considered as a selection of a well-known quantization table in the compression processing unit.
[0056]
【The invention's effect】
As described above, according to the present invention, a digital still video camera that can automatically determine the compression ratio of image data in a short time and with low power can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of a digital still video camera according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a distance measuring unit provided in the digital still video camera according to one embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a compression coefficient selection unit included in the digital still video camera according to one embodiment of the present invention.
FIG. 4 is a flowchart showing an operation of the digital still video camera according to one embodiment of the present invention.
FIG. 5 is a block diagram showing a schematic configuration of a conventional digital still video camera.
[Explanation of symbols]
101, 501 photographing lens group 102, 502 aperture 103, 503 mirror optical system 104, 504 shutter 105, 505 imaging unit 106, 506 A / D conversion unit 107, 507 signal processing unit 108, 508 buffer memory 109, 309, 509 compression Processing unit 110, 510 Memory card 115, 515 Focus detection unit 116, 516 Photometry unit 120, 520 Control unit 121 Half-press switch (release)
122 Full-press switch (release)
123 Compression mode selection switch 124, 125 Compression coefficient selection switch 140 High pass filter 141, 341 Integrator 142, 342 Compression coefficient selection unit 201 Primary focal plane 202 Condenser lens 203 Optical system 204 CCD line sensor unit 342a, 342b Comparator 343a, 343b Reference Voltage generator

Claims (2)

Imaging means for converting subject light into an electric signal; a photographing optical system for forming a subject image on the imaging means; focus detection means for focusing the photographing optical system; Analog-to-digital conversion means for converting the electrical signal into a digital signal, compression means for compressing the image data digitized by the analog-to-digital conversion means, and recording means for recording the image data compressed by the compression means In a digital still video camera with
The compression unit controls the compression ratio of the compression unit to be higher as the amount of the high-frequency component included in the output signal of the photoelectric conversion element in the focus detection unit is larger, so that the compression ratio according to the output signal is higher. A digital still video camera characterized by compressing image data. Imaging means for converting subject light into an electric signal; a photographing optical system for forming a subject image on the imaging means; focus detection means for focusing the photographing optical system; Analog-to-digital conversion means for converting the electrical signal into a digital signal, compression means for compressing the image data digitized by the analog-to-digital conversion means, and recording means for recording the image data compressed by the compression means In a digital still video camera with
An image quality priority mode in which the image data is compressed and stored in the recording medium until the image quality of the subject image captured by the imaging unit is substantially maintained; Mode selection means for switching between a data length priority mode for compressing image data so that the data length is substantially constant,
Said compression means, when you have selected the mode selecting means Gae quality priority mode, the control to lower the higher the compression ratio the amount of high-frequency components are often included in the output signal of the photoelectric conversion elements in the focus detecting means when you select the mode selecting means is de chromatography data length priority mode, so as to increase control as the compression ratio the amount of high-frequency components are often included in the output signal of the photoelectric conversion elements in the focus detecting means , it features and to Lud digital still video camera to compress the image data at a compression rate corresponding to the output signal.

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