Abstract:
A camera having an image capture unit and first and second image compression units adapted to compress a digital image outputted from the image capture unit in a first compression method and a second compression method which is different from the first compression method. First and second image decompressions units are adapted to decompress a digital image compressed in the first and second compression methods. The camera is adapted to provide a digital image outputted from the image capture unit to the first or the second image compression unit. The camera is further adapted to store a digital image compressed in the first or the second image compression unit in a removable memory unit, to provide a digital image read from the removable memory unit to the first image decompression unit if the digital image read from the removable memory unit is compressed in the first compression method, and to provide a digital image read from the removable memory unit to the second image decompression unit if the digital image read from the removable memory unit is compressed in the second compression method.

Description:
This application is a continuation of U.S. application Ser. No. 08/333,868, filed Nov. 3, 1994, now U.S. Pat. No. 5,764,286, which is a continuation of U.S. application Ser. No. 08/170,459, filed Dec. 20, 1993, now abandoned, which is a continuation of U.S. application Ser. No. 07/911,253, filed Jul. 7, 1992, now abandoned, which is a continuation of U.S. application Ser. No. 07/497,195, filed Mar. 22, 1990, now abandoned. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to still video cameras using a solid-state memory device as the image recording medium. 
   2. Description of the Related Art 
   Electronic still video cameras using a magnetic floppy disc as the image recording medium are known. In view of recent advances in the high storage and low cost unit production technique of semiconductor memories, a new type of still video camera which makes use of a semiconductor memory device as the image recording medium is regarded as promising. 
   The image sensor of the still video camera, for example, the CCD type image sensor, even in the present state of art, has some five hundred thousand picture elements. In the near future, it is likely to realize an increase of the number of picture elements to one million or more. To store data of the great number of picture elements in the memory without deterioration, as one picture element takes 8 bits, for one frame of five hundred thousand picture elements, four megabits have to be used. To provide as high a capacity of image storage of 25 frames as that of the magnetic floppy disc, the number must be 25 times increased to one hundred megabits. However far the high storage capacity technique of semiconductor memories may advance, there can be demerits in cost, size and consumption of electric power. 
   In addition, the prior known camera of the above-described new type is made to include a compressing means. This compressing means is of the fixed form. So, it has been impossible either to selectively use a plurality of compressing methods, or to alter the compressing method. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an improved camera apparatus and method. 
   This object is realized in a camera comprising: an image capture unit adapted to generate a digital image; a first image compression unit adapted to compress a digital image outputted from the image capture unit in a first compression method; a second image compression unit adapted to compress a digital image outputted from the image capture unit in a second compression method which is different from the first compression method; a first image decompression unit adapted to decompress a digital image compressed in the first compression method; and a second image decompression unit adapted to decompress a digital image compressed in the second compression method, wherein the camera adapted to provide a digital image outputted from the image capture unit to the first or the second image compression unit; wherein the camera adapted to store a digital image compressed in the first or the second image compression unit in a removable memory unit, wherein the camera adapted to provide a digital image read from the removable memory unit to the first image decompression unit if the digital image read from the removable memory unit is compressed in the first compression method, and wherein the camera adapted to provide a digital image read from the removable memory unit to the second image decompression unit if the digital image read from the removable memory unit is compressed in the second compression method. 
   The above object is further realized in a processing method for a camera, wherein the camera including an image capture unit adapted to generate a digital image, a first image compression unit adapted to compress a digital image outputted from the image capture unit in a first compression method, a second image compression unit adapted to compress a digital image outputted from the image capture unit in a second compression method which is different from the first compression method, a first image decompression unit adapted to decompress a digital image compressed in the first compression method, and a second image decompression unit adapted to decompress a digital image compressed in the second compression method, the method comprising the steps of: providing a digital image outputted from the image capture wilt to the first or the second image compression unit storing a digital image compressed in the first or the second image compression unit in a removable memory unit; providing a digital image read from the removable memory unit to the first image decompression unit if the digital image read from the removable memory unit is compressed in the first compression method; and providing a digital image read from the removable memory unit to the second image decompression unit if the digital image read from the removable memory unit is compressed in the second compression method. 
   Other objects and features of the invention will become apparent from the following written specification and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of the construction of an embodiment of the invention. 
       FIG. 2  is a block diagram illustrating the construction of the compression circuit. 
       FIG. 3  is a block diagram illustrating the construction of the expansion circuit. 
       FIG. 4  is a block diagram of another embodiment of the invention. 
       FIG. 5  is a flowchart for the operation of the embodiment of FIG.  4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is next described in connection with embodiments thereof by reference to the drawings. 
     FIG. 1  in schematic diagram shows an embodiment of the invention in which two compression processes can be selected to operate. A camera body  10  has a solid-state memory device  12  detachably attached thereto in which photographed images are recorded (stored). Light from an object to be photographed enters, through a photographic lens  14 , an image sensor  16  where it is photoelectrically converted. The output of the image sensor  16  is converted to digital form by an A/D converter  18 . A compression selecting circuit  20  determines selection of one of compression processes performed by compression circuits  22  and  24  to be applied to the data output from the A/D converter  18 . Depending on the selection result, the compression selecting circuit  20  changes a switch  26  over between two positions, so that the output data of the A/D converter  18  is supplied to the selected one of the compression circuits  22  and  24 . The compressed data by the compression circuit  22  or  24  is transferred to the solid-state memory device  12  where it is stored in a predetermined format. 
   If the camera body  10  has only a recording function, the solid-state memory device  12  is then detached from the camera body  10  and attached to a reproduction apparatus (not shown) where the recorded images are reproduced. In  FIG. 1 , however, the reproducing function too is illustrated. When the images are reproduced from the solid-state memory device  12 , data stored in the solid-state memory device  12  is read out and supplied to one of two expansion circuits  28  and  30  selected by a switch  26 . The expansion circuit  28  or  30  performs the expansion process corresponding to the compression process used in the recording. In more detail, the expansion circuit  28  expands the data compressed by the compression circuit  22 , while the expansion circuit  30  expands the data compressed by the compression circuit  24 . 
   The image data restored by the expansion circuit  28  or  30  is converted to analog form by a D/A converter  32 , and then to a video signal by a video circuit  34 . 
   It is to be noted that  FIG. 1  is depicted with regard to the flow of image signals. Therefore, various kinds of switches for operation commands, a display device and further a control circuit for controlling the entirety, an electric power source circuit, etc., are omitted. 
   Next, the compression process in the compression circuit  22  or  24  is explained in detail. The natural image has a very strong correlation between any adjacent two of the picture elements. So, taking the differences between the adjacent picture elements gives, in most cases, small values. In other words, compared with the use of the absolute values (of, for example, 8 bits) in storing (recording) the image, the use of their differences in the storage can largely compress the data amount. This compressing method is called the “DPCM”. Besides this, there are another compressing methods as improved over the DPCM, one of which is to adaptively vary the non-linearity of the non-linear quantization circuit according to the image, namely, the ADPCM. Yet another method is by transforming the image into a frequency domain, with a larger weight on the coefficient of the low-frequency component and a smaller weight on the coefficient of the high-frequency component, (namely, for example, the discrete cosine transformation). 
     FIG. 2  in block diagram shows the construction of a compression circuit employing the DPCM, and  FIG. 3  in block diagram shows the construction of an expansion circuit for expanding the compressed data. Incidentally, their details are described on pp. 146-159 of “Digital Signal Processing of Image” by Keihiko Suibatsu published by Nikkan Kogyo Shinbun Co. Ltd. The circuit of  FIG. 2  comprises a subtractor  40 , a non-linear quantization circuit  42 , a representative value setting circuit  44 , an adder  46 , a delay circuit  48  and a coefficient multiplier  50 . The subtractor  40  subtracts the output of the coefficient multiplier  50  from the input of 8-bit image data. The non-linear quantization circuit  42  non-linearly quantizes the output of the subtractor  40 . Thereby the image data of the input is compressed from the 8 bits to, for example, 3 bits. The 3-bit output of the non-linear quantization circuit  42  is the compressed data which is aimed at. 
   The representative value setting circuit  44  reverts the 3-bit output of the non-linear quantization circuit  42  to a representative value of 8 bits. The adder  46  adds the output of the coefficient multiplier  50  to the output of the representative value setting circuit  44 , i.e., the data (8 bits) of the representative value. The output of the adder  46  is delayed by one picture element by the delay circuit  48 , concretely speaking, a data latch circuit, before it is supplied to the coefficient multiplier  50 . The coefficient multiplier  50  multiplies the input by a constant coefficient, for example, 0.95, and supplies the multiplication result to the subtractor  40  and the adder  46  at the time of the inputting of the next data. 
   By repeating such a procedure, the 8-bit data is compressed to the 3-bit data. 
   The non-linear quantization circuit  42 , the representative value setting circuit  44  and the coefficient multiplier  50  can be realized in the form of table transformation of ROM. So, high speed processing is possible. 
   Next, the expansion circuit of  FIG. 3  comprises a representative value setting circuit  52 , an adder  54 , a delay circuit  56  for delaying the input by one picture element and a coefficient multiplier  58 . The representative value setting circuit  52  is similar to the representative value setting circuit  44  of  FIG. 2 , transforming the input data (3 bits) to a representative value of 8 bits. The adder  54  adds the output of the coefficient multiplier  58  to the output of the representative value setting circuit  52 . The output of the adder  54  becomes the restored data which is aimed at. The delay circuit  56  is a data latch circuit similar to the delay circuit  48 , delaying the output of the adder  54  by one picture element before it is supplied to the coefficient multiplier  58 . The coefficient multiplier  58  multiplies the input by a constant coefficient, for example, 0.95. Its output is supplied to the adder  54 . By such a loop process, the compressed data (3 bits) of the input is expanded to the original data of 8 bits. 
   The discrete cosine transformation method as it details are described in pp. 179-195 of “Digital Signal Processing Image” by Keihiko Suibatsu published by Nikkan Kogyo Shinbun Co. Ltd., is briefly explained as follows. At first, by the discrete cosine transformation, the image data is orthogonally transformed and the frequency components are taken out. These frequency components are multiplied by such a coefficient that the low-frequency component is left, while the high-frequency component is removed. By this, the image information can be compressed. When the frequency components of the image are sided to the lower one, good compression with less deterioration can be carried out. 
   Next, the selection criterion by the compression selecting circuit  20  is explained. For simplicity, the compression circuits  22  and  24  themselves, or similar circuits, perform compression processing by each of the plurality of compressing methods, and whichever gives a less amount of data may be selected. If it is desired to speed up the selecting operation, a portion of the image, for example, the central one, only is subjected to the plurality of compression treatments. Based on the comparison of the data amounts, selection of one of the compression treatments may be made. Also, one of the compression circuits, say  22 , employs a compression method which gives always a constant amount of compressed data, while the other compression circuit  24  employs another compression method which varies the amount of compressed data as a function of the image. So, from only the amount of data output from the compression circuit  24 , which compression circuit  22  or  24  is to be selected may be determined. 
   The compression circuits  22  and  24  may employ different compressing methods from each other. But the compressing methods may be the same, or quantitatively different in the compression characteristic. In the case of DPCM, for example, the quantizing characteristic of the non-linear quantization circuit  42  is changed. 
   Though, in the above-described embodiment, the two compressing processes are selectively used, the invention is not confined to this and so includes a mode of non-compression and another mode of compression. Also, the image data is not only for black and white but also likewise for colors. Further, the selection of the compressing methods may otherwise be made not automatically but manually. 
   As is easily understandable from the foregoing description, according to the invention, the amount of data of an image to be recorded can be compressed by the method suitable to the respective individual image, thereby giving an advantage of more efficiently utilizing the image recording medium. 
   The invention is next described in connection with another embodiment thereof. 
     FIG. 4  in block diagram shows another embodiment of the still video camera according to the invention, and  FIG. 5  is a flowchart for the operation of this embodiment. 
   In  FIG. 4 , the camera comprises a lens  61 , a CCD  62  (solid-state image sensor) for converting an image formed thereon by the lens  61  to an electrical signal, a signal processing portion  63  for processing the signal output from the CCD  62 , an A/D converter  64  for converting the signal output from the signal processing portion  63  to digital form, a data compressing portion  65  for compressing the digitized image signal, a connector  66 , a memory cartridge  67  (memory element) detachably attached to the camera body, and a block  68  for controlling the entirety including a timing control circuit and a system control portion (hereinafter called the “system controller”). 
   In the interior of the data compressing portion  65 , a program ROM for determining the compressing method is incorporated. As this ROM, use is made of a rewritable EEPROM (Electrically Erasable Programmable Read-Only Memory). The memory cartridge  67  is available in types for photography and for a compression program. When the latter type is in use, the content of the EEPROM in the data compressing portion  65  is rewritten by the system controller  68  into the content of the compression program cartridge. 
     FIG. 5  shows a flowchart for the operation of this embodiment. 
   After initialization (step S 101 ) has been done, when a memory cartridge is inserted (step S 102 ), whether it is for photography or for compression programs is discriminated (step S 103 ). If for compression programs, a compression code number representing the compression program is written (step S 104 ) and the compression program is transferred to the EEPROM (step S 105 ). When this has ended, the “end” display is presented (step S 106 ). If it is for photography, an initiation of a shutter operation (step S 110 ) is followed by writing the compression code number (step S 111 ) and the photographed image data (step S 112 ). 
   In such a manner, the program for use in the compression of the video signal can be written and rewritten in the form of electrical signals by the cartridges from the outside of the camera. 
   It should be noted that the camera may be provided with an input terminal for program, from which a program for compression is supplied in the form of an electrical signal by an adequate device, thus rewriting the program of the EEPROM of the data compressing portion  65 . 
   As has been described above, according to the present embodiment, the program for compression of the data in the camera is alterable by the electrical signal supplied from the outside of the camera. Therefore, a wide variety of compressing methods become selectively usable. Hence, the camera is made convertible to the newest data compression type. Further, when the object to be photographed is a flower, the camera can be made to operate with the selection of one of the compressing methods which is most suited to the flower.