JP4557900B2 - Imaging device - Google Patents

Description

The present invention relates to an imaging apparatus such as a video camera or a still camera with a signal recording apparatus for recording a video signal obtained by shooting.

  As a video signal recording / reproducing technique, a video signal recording / reproducing system described in Japanese Patent Laid-Open No. 3-175784 converts a video signal of a selected screen into a digital signal form and then performs a data compression process to reduce the amount of data. It has been proposed to reduce the weight and store it in a removable memory pack.

  However, this video signal recording / reproducing system extracts and records a part of the main video signal for easy confirmation of the recorded content of the main video signal recorded on the magnetic tape. It is not intended for use.

  Video recording devices such as video cameras and still cameras equipped with PC card-type signal recording devices that record continuous video signals obtained by shooting have improved reliability, reduced power consumption, and reduced size and weight. Improvement from the viewpoint is desired. For example, when a PC card type magnetic hard disk drive (HDD = Hard Disk Drive) is used as the signal recording device, the HDD is in a recording operation state throughout the photographing period, so that the power consumption increases and the capacity increases. Since a power source (battery) is required and the amount of heat generated increases, the amount of heat generation increases and the temperature rises, so the temperature countermeasure becomes complicated. These also hinder downsizing and weight reduction of the video recording / reproducing apparatus.

  Also, an HDD using a magnetic hard disk as a recording medium has a magnetic head placed on the surface of the magnetic hard disk in a recording and reproducing operation state. Recording and playback of signals in a state where they face each other with a gap of several microns (head loading), so they are very vulnerable to vibration and shock (the head and disk are easily damaged by contact) It is in. For example, even if an HDD with impact resistance of 100G is used, this is enough to withstand the impact that acts when the HDD drops from a height of 1 to 2 centimeters onto a desk. When such a video recording apparatus using an HDD is a portable digital video camera, it is highly likely that an impact force exceeding this value will be generated, so that the HDD is not easily damaged. Must be implemented. However, mounting the HDD with a mechanical buffering member becomes an obstacle to the reduction in size and weight of the digital video camera.

A signal recording device using a flash memory as a recording medium can be used instead of the HDD. However, since this flash memory also consumes about several hundred mW when in the writing operation state, the writing operation state is maintained over the entire shooting period. If this is maintained, power consumption increases and a large-capacity power supply is required.
JP-A-3-175784

  For small portable digital video cameras that digitalize and compress continuous video signals obtained by shooting and record them in a signal recording device, and digital cameras that attempt to record and play back moving images, this camera is set to the operating state. The magnitude of power consumption is an extremely important factor. In particular, a signal recording apparatus using an HDD consumes a large amount of power by the HDD. And the temperature rise of the whole recording apparatus by the heat | fever generate | occur | produced with power consumption also becomes a problem.

  In addition, since the HDD has a low reliability with respect to vibration and shock due to its structure, a video recording apparatus using the HDD as a signal recording device has a problem with reliability against vibration and shock given from the outside. Become.

  One object of the present invention is to propose a small video recording apparatus capable of reducing power consumption and temperature rise.

  Another object of the present invention is to propose a small video recording apparatus that is highly reliable with respect to impact and vibration.

  Still another object of the present invention is to propose a small-sized video recording apparatus that has low power consumption and temperature rise, and is highly reliable against shock and vibration.

In the present invention, the above object can be achieved by the following configuration, for example, but is not limited to this configuration.
The purpose is, for example, an imaging unit that images a subject and outputs a video signal, a camera signal processing unit that processes a video signal output from the imaging unit, and a video signal output from the camera signal processing unit , A recording means for recording a video signal stored in the buffer memory on a recording medium using a recording head, and a recording operation state for recording the video signal stored in the buffer memory on the recording medium And an operation control means for performing intermittent recording in a pause state in which the recording operation is paused while accumulating the video signal in the buffer memory, and the operation control means is configured to perform a recording operation during the intermittent recording. The pause period can be achieved by controlling the recording head to be retracted from the surface of the recording medium .

  The present invention can reduce power consumption and temperature rise by shortening the period during which the signal recording apparatus is in a recording operation state with high power consumption.

Further, by shortening the duration of easily recording operation state damage to vibration or impact, it is improved reliability against vibrations and impacts.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a circuit block diagram of a portable digital video camera according to the present invention capable of recording and reproducing a television signal of NTSC (National Television System Committee) system or PAL (Phase Alternation Line) system. This digital video camera converts a continuous analog video signal obtained by photoelectric conversion in the image pickup unit into a digital video signal, and further compresses it according to the MPEG (Moving Picture Expert Group) 1 format. Data is recorded in digital memory and reproduced.

  The lens unit 1 has a configuration capable of zooming and iris control, and the focus is a fixed focus method. A CCD (Charge Coupled Device) solid-state imaging device 2 converts an optical subject image captured by the lens unit 1 into an electrical analog video signal. The preprocessing circuit 3 suppresses low-frequency noise peculiar to the CCD solid-state image pickup device 2 included in the video signal read from the CCD solid-state image pickup device 2 by a CDS (Correlated Double Sampling) circuit. In order to stabilize the signal level of the output signal of 2, the automatic gain control is performed by the AGC circuit, and further, the preprocessing is performed to compensate for the dynamic range shortage of the subsequent analog-to-digital converter (ADC = Analog Digital Converter) 4. A function of limiting the amplitude near the input upper limit value of the ADC 4 with respect to the level of the video signal input to the circuit 3 is also provided.

  A camera signal processing circuit (DSP = Digital Signal Processor) 5 inputs a video signal output from the preprocessing circuit 3 and converted into a digital form by the ADC 4. Although not shown, the camera DSP 5 has a function of converting a digital video signal input from the ADC 4 into a luminance signal Y and color difference signals U and V by a matrix circuit, a function of adding a synchronization signal, an iris and a shutter speed. A function for adjusting the relationship, a function for adjusting white balance, a function for digitally zooming in, and the like. The camera DSP 5 outputs a horizontal / vertical drive signal pulse to the CCD solid-state image pickup device 2 and reads a video signal from the CCD solid-state image pickup device 2 while taking a timing with the synchronization signal.

  The camera control microcomputer 6 controls the motor 8 for driving the iris and zoom via the motor driver 7, supplies parameters necessary for the operation of the camera DSP 5 to the camera DSP 5, and controls the entire camera system. to manage.

  In the recording mode, the encoder / decoder 9 inputs a digital video signal (luminance signal Y and color difference signals U and V) generated by the camera DSP 5 via a digital bus line, and outputs a digital video signal. The data amount is reduced to about 1/50 by compressing (encoding) to the MPEG1 format which is a standard compression format. In this embodiment, the encoder / decoder 9 generates compressed data in a digital form of 1.72 Mbit / s. In the playback mode, a digital video signal is generated by decompressing (decoding) the compressed data read from the HDD 15 into the buffer memory 13 according to the MPEG1 format, and sent to the camera DSP 5 via the digital bus line.

  The work memory 10 is a memory used when the encoder / decoder 9 compresses / decompresses data according to the MPEG1 format.

  The recording / reproducing control microcomputer 11 supports the data compression / decompression process by the encoder / decoder 9 and controls the data transmission process and the operation display lamp 12.

  In this embodiment, the buffer memory 13 is configured using a synchronous DRAM having a storage capacity of 8 Mbits.

  In this embodiment, in the recording mode, the recording / playback control microcomputer 11 divides a continuous video signal of a moving image with a period of 2.33 seconds, and compresses the video signal in one division according to the MPEG1 format by about 4 Mbits. The encoder / decoder 9 is controlled so that the data is sequentially reduced so as to be reduced and stored in the buffer memory 13, and one section (corresponding to 2.33 seconds) of 4 Mbits of compressed data stored in the buffer memory 13. Is transferred to the memory card type HDD 15 of the PC card standard defined by PCMCIA (abbreviation of Personal Computer Memory Card International Association) via the interface circuit 14 and is recorded in a time of about 0.72 seconds, and is played back. Then, in order to reproduce a video signal of one section having a period of 2.33 seconds, the compressed data of the one section (4 Mbits) is used. Is read from the HDD 15 through the interface circuit 14 in a time of about 0.72 seconds, transferred to the buffer memory 13 and stored, and the compressed data stored in the buffer memory 13 is transferred to the encoder / decoder 9 for MPEG1 format. The video signal having a time of 2.33 seconds is generated by being expanded in accordance with the above, and is sent to the camera DSP 5 through the digital bus line. The data transfer timing is generated by the recording / reproduction control microcomputer 11.

  The card connector 16 is a PCMCIA standard card connection interface having a 68-pin connection terminal.

  The HDD 15 is standardized to a length of 54.4 mm, a width of 85.6 mm, and a thickness of 10.5 mm. A magnetic hard disk, a magnetic hard disk rotation drive motor, a servo circuit, a magnetic recording / reproducing head are included in the housing. , A digital signal recording processing circuit and a 256 kbit input / output interface buffer memory are incorporated.

  The camera DSP 5 is a digital video input from the ADC 4 or the encoder / decoder 9 by a built-in NTSC or PAL encoder and digital / analog converter (DAC = Digital analog converter) during recording and playback. The signals are organized into NTSC or PAL analog TV signals and output to a video signal monitor LCD (Liquid Crystal Display) monitor panel 17 and an output terminal 18.

  FIG. 2 is a time chart showing the timing of data compression, data transfer, and data writing by the encoder / decoder 9, the recording / reproduction control microcomputer 11, the buffer memory 13 and the HDD 15 in the recording mode.

  (A) is a processing timing at which the encoder / decoder 9 compresses the digital video signal output from the camera DSP 5 according to the MPEG1 format to generate compressed video data and outputs it to the recording / playback control microcomputer 11. Is shown. In this embodiment, data compression processing is executed at a rate of 30 frames per second (two GOPs (Group Of Picture) as a group of video frames) to generate a data string of 1.72 Mbit / sec. The data processing amount of one division is 70 frames (4M bits in terms of compressed data amount) in 2.33 seconds. Actually, the video signal is compressed using 2 frames as 1 packet.

  (B) shows the processing timing for transferring the compressed data to the buffer memory 13 and storing it. Since the HDD write cycle T0 in this embodiment is 2.33 seconds, one section is about 2.33 seconds, and 4 Mbits of compressed data for 70 frames are transferred and stored in the buffer memory 13 in units of packets during this period. Is done.

  (C) shows the access (recording operation) timing of the HDD 15. Here, 4 Mbits of compressed data stored in the buffer memory 13 for about 2.33 seconds are recorded in the HDD 15 in a short time. In this embodiment, the recording operation time T1 for operating the HDD 15 to record one section of compressed data is about 0.72 seconds. For this recording, the recording / playback control microcomputer 11 transfers the compressed data stored in the buffer memory 13 to the buffer memory in the HDD 15 in units of packets and records it on the magnetic hard disk. Here, the HDD 15 performs a recording operation as follows upon receiving a write command from the recording / reproducing control microcomputer 11. The magnetic recording head is loaded onto the magnetic hard disk (required time t11 = about 0.2 seconds). After referring to the disk management area, the magnetic head is sought to a desired recording track (required time t12 = 0.01 seconds). Data is recorded in units of packets on the magnetic disk (required time t13 = 0.31 seconds). The magnetic recording head is unloaded from the magnetic disk (required time t14 = about 0.2 seconds). Then, it pauses until the same recording is started for the next segment (pause period T2 = about 1.61 seconds).

  FIG. 3 is a flowchart of processing executed by the encoder / decoder 9 and the recording / reproduction control microcomputer 11 for such data compression and compressed data recording. When a digital video signal is output from the camera DSP 5, the encoder / decoder 9 is controlled by the recording / playback control microcomputer 11 to acquire the video signal in processing step 301, and in accordance with the MPEG1 format in processing step 302. Compress the signal. In this compression processing, two frames of the video signal are executed as one packet, and when the end of data compression for one packet is confirmed in processing step 303, the processing proceeds to processing step 304 and the compressed data is written and stored in the work memory 10. .

  On the other hand, the recording / reproducing control microcomputer 11 reads the compressed data from the work memory 10 in the processing step 305, and writes the compressed data in the buffer memory 13 in the processing step 306. Then, the process proceeds to processing step 306 to check whether or not compressed data of one section (4 Mbits) has been accumulated in the buffer memory 13. When one section of the compressed data is stored in the buffer memory 13, the recording / reproducing control microcomputer 11 moves to processing step 308 to load the magnetic head of the HDD 15 onto the magnetic hard disk in order to make the HDD 15 in a data recordable state. , Seek to the recording track. Thereafter, the process proceeds to processing step 309, where the compressed data stored in the buffer memory 13 is transferred to the interface circuit 14 in packet units, and a write command is given to the HDD 15 in processing step 310 to record the compressed data in the HDD 15. . This writing is continued until the end of writing of one section (4M bits) is confirmed in processing step 311. When the writing is completed, in order to put the HDD 15 into a sleep state, the processing proceeds to processing step 312 and the magnetic head of the HDD 15 is moved. The HDD 15 is suspended from the magnetic hard disk until data is recorded for the next section.

  The HDD 15 generally consumes a very large amount of current when it is in an operation state necessary for recording data, and the PCMCIA standard type III type HDD 15 used in this embodiment has a current consumption of 250 mA. The power consumption of the HDD is roughly divided into the following four states. The standby state where the motor that rotates the magnetic hard disk is stopped, the startup state where the motor starts rotating, the idle state where the motor is rotating but the magnetic head is retracted from the disk and the recording operation is paused, the magnetic head is This is a read / write state in which a data read or write operation is performed facing the magnetic disk. The power consumption in each of these states is in the order of startup state> read / write state> idle state> standby state.

  Therefore, if the time T2 for stopping the recording operation by setting the HDD 15 in the idle state during video recording is created, the HDD 15 is in a low power consumption state for maintaining the rotation of the magnetic disk during this period, and the recording operation time T1. As the pause time T2 is longer than (= t11 + t12 + t13 + t14), the effect of reducing the power consumption of the system is greater in video recording that records data for a long time of several minutes.

  FIG. 4 shows the relationship between the storage capacity of the buffer memory 13 and the current consumption for data recording by the HDD 15 in the portable digital video camera according to the present invention. The horizontal axis represents the storage capacity of the buffer memory 13, and the vertical axis represents the total current consumption of the HDD 15. Curve 30 is for HDD 15 with a storage capacity of 340 Mbytes, curve 31 is for HDD 15 with a storage capacity of 260 Mbytes, and curve 32 is for HDD 15 with a storage capacity of 170 Mbytes. In this embodiment, the HDD 15 having a storage capacity of 260 Mbytes is used in order to realize moving image recording for 20 minutes or more. Referring to this characteristic curve, when compressed data is stored using a buffer memory using a 4M bit product, which is a general DRAM capacity, current consumption can be reduced by about 100 mA. Considering the power consumption, the power supply of the HDD 15 is generally 5 V, so that it is possible to reduce the power by 500 mW. Since the total power consumption of a small portable digital video camera is about 6.0 W, the reduction is 8.3%. As a result, the life of the battery, which is very important as a portable device, can be improved by about 8.3%.

  Further, as described above, the HDD 15 is very vulnerable to vibration and impact during the recording operation. However, if the recording operation pause period T2 is provided as in this embodiment, the magnetic head is in a state of being retracted from the magnetic disk during this period. Does not hit the magnetic disk and damage the magnetic disk or destroy the data. In this embodiment, the recording operation period T1 in which the magnetic head faces the magnetic disk is 1/3 of one section (writing period) T0, and the risk factor due to vibration and impact is reduced to 1/3. Reliability will be increased by a factor of three.

  FIG. 5 is a longitudinal side view of a very miniaturized portable digital video camera according to the present invention. The same components as those of the circuit block shown in FIG. The photographing unit 20 including the lens unit 1 and the CCD solid-state imaging sensor 2 is rotatably coupled to the recording / reproducing unit 22 by a rotational coupling mechanism 21. The recording / reproducing unit 22 includes a circuit board 24 on which the circuit elements 23 from the preprocessing circuit 3 to the interface circuit 14 and the PCMCIA card connector 16 are mounted, the display lamp 12, the LCD monitor panel 17, and a rechargeable battery 25. Built in. car. A PCMCIA type III standard 260 Mbyte HDD card 15 is attached to the connector 16.

  The portable digital video camera in this embodiment is collected in a very small form having a height dimension of 144 mm, a width dimension of 78 mm, and a depth dimension of 43 mm. As the device is miniaturized in this way, components are mounted at a high density inside the device, so that the temperature rise inside the device due to power consumption increases. In such a portable digital video camera, if the HDD 15 is maintained in the recording operation state over the entire period of recording the moving image, the surface of the HDD 15 rises to about 80 ° C. The housing of the HDD 15 is made of metal in order to increase its structural reliability. However, when the user touches the metal housing whose surface temperature has increased to 80 ° C. for attachment and detachment, it burns. There is danger. In this embodiment, since the HDD 15 can be attached to and detached from the portable digital camera to improve the usability when transferred to a personal computer or the like, it is necessary to suppress the temperature rise of the HDD 15 during recording as much as possible. .

  However, as described above, the HDD 15 is stored within a short time (0.72 seconds) after compressing the video signal to be recorded generated in a predetermined period (1 division = 2.33 seconds) and storing it in the buffer memory 13. Since the average current consumption of the HDD 15 can be reduced to about 100 mA by recording the recording time and stopping the surplus time, the surface temperature of the housing can be suppressed to 70 ° C. or lower. It becomes. Such a surface temperature is a temperature at which there is relatively little danger even when touched, and the user can safely remove the HDD 15 from the portable digital camera.

  Further, since the power consumption is reduced, the consumption of the rechargeable battery 25 is also reduced, so that a small size is sufficient, which is advantageous for reduction in size and weight.

  The embodiment using the HDD for recording the video signal (compressed data) has been described above, but the present invention can also be applied to recording on a memory card using a flash memory. The flash memory consumes about several hundreds mW of power for the writing operation due to its characteristics. However, if the present invention is used, the power consumption can be reduced in the same manner as recording to the HDD.

The present invention can also be applied to a video recording apparatus using a recording means in which a recording / reproducing medium for recording / reproducing compressed data cannot be attached / detached.
As is clear from the above description, the embodiment according to the present invention includes, for example, the following configuration.
For example, in the video recording apparatus for converting a continuous analog video signal obtained by photographing into a digital video signal and recording compressed data compressed on the time axis in the signal recording apparatus, the signal recording apparatus A recording control means for recording compressed data in a data compression means for compressing a video signal for each predetermined period and storing it in a buffer memory; and the compressed data for each predetermined section stored in the buffer memory as the signal The signal recording device is set in a recording operation state only for a period necessary for recording in the recording device, and the compressed data stored in the buffer memory is recorded in the signal recording device, and the recording operation is performed in other periods. By providing an operation control means for putting the signal recording apparatus in the resting state, the period for setting the recording operation state in which the power consumption of the signal recording apparatus is large can be shortened and the power consumption and To reduce the degree rise
Further, as apparent from the above description, according to the embodiment of the present invention, for example, the following effects are also included.
For example, when the signal recording device is a hard disk device, the reliability of vibration and impact is improved by shortening the period of the recording operation state that is easily damaged by vibration and impact.
For example, by making the recording operation period shorter than the recording operation pause period, the effects of reducing power consumption, reducing temperature rise, and improving reliability are increased.
Furthermore, for example, the power supply is reduced by reducing power consumption, and the temperature countermeasure is facilitated by reducing the temperature rise, thereby facilitating downsizing and improving the reliability of the signal recording apparatus. The effect of facilitating impact countermeasures can also be obtained.

1 is a circuit block diagram of a portable digital video camera according to the present invention. 4 is a time chart showing timings of data compression, data transfer, and data writing in the recording mode of the portable digital video camera according to the present invention. 3 is a flowchart of data compression, data transfer, and data write processing in the recording mode of the portable digital video camera according to the present invention. It is a characteristic view which shows the power consumption reduction effect of HDD in the portable digital video camera which becomes this invention. It is a vertical side view of a very small portable digital video camera according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lens part, 2 ... CCD solid-state image sensor, 5 ... Camera DSP, 6 ... Camera control microcomputer, 9 ... Encoder / decoder, 10 ... Work memory, 11 ... Recording / reproduction control microcomputer, 13 ... Buffer memory, 15 ... HDD .

Claims (4)

Imaging means for imaging a subject and outputting a video signal that is a continuous moving image ;
Camera signal processing means for processing a video signal output from the imaging means;
Compression processing means for compressing the video signal output from the camera signal processing means;
A buffer memory for storing the compressed video signal output from the compression processing means;
Recording means for recording the video signal stored in the buffer memory on a recording medium using a recording head;
An operation control means for performing intermittent recording by a recording operation state in which the video signal stored in the buffer memory is recorded on a recording medium and a pause state in which the recording operation is paused while storing the video signal in the buffer memory; ,
With
The operation control means captures the subject and outputs a video signal that is a continuous moving image, the camera signal processing means performs the camera signal processing, and the compression processing means performs the compression processing. The buffer memory accumulates the video signal output from the compression processing means, and the recording head is retracted from the surface of the recording medium during the pause state of the recording operation during the intermittent recording. To be controlled,
An imaging apparatus characterized by the above. In claim 1 ,
The recording medium is a hard disk;
An imaging apparatus characterized by the above. In claim 1 or 2 ,
The recording medium is a card-type hard disk detachably provided in the imaging apparatus;
An imaging apparatus characterized by the above. In any of claims 1 to 3 ,
The compression processing means performs compression processing according to the MPEG method;
An imaging apparatus characterized by the above.

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