JP2009200982A - High-speed imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a long-time photographing standby by suppressing an imaging device from being heated during the photographing standby while preventing noise from being accumulated in the device during the standby. <P>SOLUTION: When a photographing starting instruction is given from an operating unit 16, a timing control unit 17 controls an imaging device 13 so as to implement an idling operation for operating a CCD 132 for accumulation at low speed. In such a state, since a calorific value of the device is small, temperature elevation is smooth. Since accumulated charges of a photoelectric conversion unit 131 are sequentially fed by the CCD 132 for accumulation, meanwhile, noise is not accumulated by a dark current, either. When a photographing starting trigger is output from a trigger signal generating unit 18 in response to a detecting signal from an external sensor 2, high-speed photographing operation is started by the imaging device 13 and when pixel signals are accumulated as many as the predetermined number of frames that are accumulated in the CCD 132 for accumulation, photographing is finished. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a high-speed imaging apparatus for capturing high-speed phenomena that are difficult to capture with a normal imaging apparatus such as bursting, explosion, combustion, collision, discharge, or high-speed movement of an object.

  For example, a dedicated high-speed imaging device has been developed in order to continuously capture high-speed phenomena such as explosion, destruction, combustion, collision, and discharge (for example, Non-Patent Document 1). With this high-speed photographing device, photographing at a very high speed of 1 million frames / second is possible. Conventional general CCD-type and CMOS-type image sensors cannot cope with such high-speed shooting. For this reason, an imaging element having a special structure as described in, for example, Patent Document 1 is used for the high-speed imaging device.

  This imaging device is called a pixel peripheral recording type imaging device (IS-CCD = image storage-CCD), and is vertically transferred by the number of recording frames (for example, about 100 frames) for each photodiode as a photoelectric conversion unit. During the shooting, the signal charge photoelectrically converted by the photodiode is sequentially transferred to the storage CCD, and after the shooting, the signal charge for the number of recording frames stored in the storage CCD is stored. The pixel signal is acquired by sequentially reading through the horizontal transfer CCD. The signal charge that exceeds the number of recording frames during shooting is discarded, and the signal charge for the latest number of recording frames is always held in the storage CCD. If the operation is canceled, the latest predetermined number of frames from the time point that has been recorded by the number of recording frames from that point in time can be obtained.

  Although the above-described imaging device can perform extremely high-speed shooting, on the other hand, it consumes a large drive current and generates a considerable amount of heat during the shooting operation. For this reason, for example, if high-speed shooting operation is continuously performed at 1 Mfps, which is the maximum shooting speed, the element may be destroyed due to heat generation. In order to avoid this, conventionally, the element temperature is monitored and the driving of the element is stopped when an abnormal temperature is reached, or the continuous time (high-speed shooting allowable time) for performing the high-speed shooting operation is limited. Yes.

  Due to the characteristics of the subject in such a high-speed imaging device, for example, a phenomenon such as an explosion has occurred and it is desired to photograph changes occurring within a short period of time from when a trigger signal corresponding to the occurrence is obtained. There are many cases. In that case, it is necessary to wait for the target phenomenon to occur, and in some cases, the standby state may be prolonged. In such a case, if the camera is on standby in the state of high-speed shooting as described above, the shooting standby state may be automatically canceled because the high-speed shooting allowable time has passed during that time. It was.

  In terms of control, it is possible to drive the imaging device so that the imaging device starts a high-speed imaging operation after the trigger signal is obtained without driving the imaging device during imaging standby. However, in general, in the above-described image sensor, noise accumulation due to dark current becomes a problem. Therefore, when the operation of the image sensor is started from the photographing start time, a sufficient SN ratio is ensured. There is a problem that is difficult.

JP 2001-345441 A Kondo et al., “Development of High-Speed Video Camera HyperVision HPV-1”, Shimadzu review, Shimadzu review editorial department, published on September 30, 2005, Vol. 62, No. 1, p. 79-86

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-speed imaging device capable of extending the standby time before starting high-speed imaging while ensuring the SN ratio of the image at the time of shooting. Is to provide.

In order to solve the above-mentioned problems, the present invention includes an imaging unit that photoelectrically converts a captured optical image of a subject and outputs it as an electrical signal, and processes the electrical signal output from the imaging unit as a captured image. A high-speed imaging device,
a) start trigger generating means for generating a trigger signal for giving an instruction to start photographing;
b) Stand by in an idling state that repeats the operation at a lower speed than the shooting operation described later until the trigger signal is given, and drives the imaging means so as to shift to the shooting operation at a high speed when the trigger signal is given. Photographing control means;
It is characterized by having.

  As one aspect of the high-speed imaging device according to the present invention, the imaging unit includes a signal storage unit that stores therein an electrical signal for a predetermined number of frames without outputting the signal to the outside. Preferably, the imaging means is controlled to end the imaging when the electrical signal corresponding to the optical image having the predetermined number of frames is accumulated in the signal accumulation unit after the imaging is started in response to the input of the trigger signal. .

  The start trigger generation means may generate a trigger signal in response to a detection signal from another sensor that detects a change in the subject, for example, a vibration sensor, a position sensor, an optical sensor, a sound sensor, or the like. Further, based on the result of processing an image signal acquired by another photographing apparatus, for example, a trigger signal may be generated when a specific change occurs on the image. Of course, the trigger signal may be generated in accordance with a manual operation by the operator.

  Further, the transition from the stop state to the idling state may be performed according to a manual operation by an operator, for example.

  As an example of a shooting work procedure using the high-speed shooting apparatus according to the present invention, a photographer first places the apparatus in a shooting standby state by a manual operation. Thereby, the imaging control means operates the imaging means in an idling state. When the image pickup means is an image pickup device that performs signal transfer using a CCD, in the idling state, the photoelectric conversion operation and the signal transfer of the electric signal obtained thereby are repeatedly performed at a low speed. At this time, naturally, a drive current is supplied to the image sensor, but since it is a low-speed operation, the amount of heat generation is considerably smaller than that during a high-speed shooting operation, and the idling state can be continued for a long time.

  Then, when the trigger signal is generated by the start trigger generation means, the imaging control means switches the operation of the imaging means from the idling state to a preset high-speed imaging operation, and substantially starts optical image imaging. Since the photoelectric conversion operation and the electric signal transfer operation are repeatedly performed in the idling state until immediately before the start of photographing, noise due to dark current or the like is not accumulated, and an image signal having a good SN ratio from immediately after the photographing is started. Can be obtained.

  According to the high-speed imaging device of the present invention, since heat generation of the imaging unit is suppressed during standby before the start of shooting, damage to the element due to excessive heat generation can be avoided even when the shooting standby time is long. Thereby, it is possible to wait for a long time. Further, since the basic operation of the image pickup means is performed even during standby for shooting, accumulation of noise due to dark current or the like does not matter, and an image signal with a high S / N ratio can be obtained immediately after the start of high-speed shooting. Can do.

  A high-speed imaging apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a configuration diagram of a main part of a high-speed imaging apparatus according to the present embodiment, FIG. 2 is a schematic timing diagram for explaining the operation of the high-speed imaging apparatus of the present embodiment, and FIG. 3 uses the high-speed imaging apparatus of the present embodiment. FIG. 4 is a diagram illustrating an example of a flowchart of a photographing procedure, and FIG. 4 is a diagram schematically illustrating a temperature change of the image sensor in the high-speed photographing device of the present embodiment.

  As shown in FIG. 1, the high-speed imaging device 1 includes an imaging lens 10 that collects incident light coming from a subject to be imaged, and an imaging device that converts an optical image into an electrical signal (in the imaging means of the present invention). 13), an image processing unit 14 that processes the captured electrical signal (pixel signal), a storage unit 15 that stores the processed data, and a shutter drive unit 12 that blocks light incident on the image sensor 13. A mechanical shutter 11 that is driven, an operation unit 16 that is operated by a photographer, and a timing control unit that supplies various control signals and clock signals to control each unit in order to perform shooting (shooting according to the present invention). And a trigger signal generation unit (corresponding to start trigger generation means in the present invention) 18 for generating a shooting start trigger. A detection signal from an external sensor 2 different from the high-speed imaging device 1 is input to the trigger signal generation unit 18. Further, the image data stored in the storage unit 15 is output to the outside and reproduced by the monitor 3.

  The external sensor 2 is not particularly limited as long as it detects the beginning of a change in a subject that is a subject of photographing. For example, a vibration sensor, a position sensor, a sound sensor, an optical sensor, or the like is used. The trigger signal generation unit 18 generates a shooting start trigger in accordance with either a detection signal from the external sensor 2 or a predetermined operation in the operation unit 16, and gives the shooting start trigger to the timing control unit 17. The timing control unit 17 includes not only a CPU and a ROM storing a control program, but also a circuit that generates various clock signals necessary for operating the image sensor 13 and the like.

  The imaging device 13 is the above-described pixel peripheral recording type imaging device (IS-CCD), and a photoelectric conversion unit 131 such as a photodiode arranged in a two-dimensional array and an electrical signal generated by the photoelectric conversion are transmitted for a predetermined number of frames. It includes a storage CCD 132 that stores (for example, 100 frames as an example), and a transfer CCD 133 that reads out the electrical signals held in the storage CCD in order. Actually, since the storage CCD 132 also has a function of a vertical transfer CCD, a part of the storage CCD 132 and the transfer CCD 133 are common. However, the image pickup device 13 is not limited to this, and may be any image pickup device capable of high-speed shooting of about 1 kfps or more.

  The image processing unit 14 includes an amplifier and an A / D converter, amplifies the analog pixel signal read from the image sensor 13, converts it to digital data of a predetermined number of bits, and performs appropriate noise removal and the like as necessary. Perform data processing. The image data processed by the image processing unit 14 is stored in the storage unit 15 having a storage area for a predetermined number of frames, and further output to the monitor 3 in order.

  Next, a characteristic operation of the high-speed imaging device 1 of the present embodiment will be described. The photographer first sets shooting conditions such as a shooting speed (frame rate) from the operation unit 16. The fastest frame rate that can be set is 1 Mfps (1 million frames / second) or more, which is much faster than a normal photographing apparatus. When the photographing condition setting is completed, the photographer gives a photographing standby instruction through the operation unit 16 so that photographing can be started anytime (YES in step S1). Upon receiving this instruction, the timing control unit 17 controls the shutter drive unit 12 to open the shutter 11 and controls the image sensor 13 to execute an idling operation (step S2).

  When the shutter 11 is opened, light that has passed through the imaging lens 10 enters the imaging element 13. Originally, it is desired to shield incident light during idling operation, but the opening and closing operation of the shutter 11 requires a longer time than the high-speed imaging operation (d in FIG. 2; for example, about 3 ms). Therefore, if the shutter 11 is opened after the shooting start trigger is input, the exposure start is delayed and the desired shooting cannot be performed. Therefore, here, the shutter 11 is opened at the time of start of photographing standby.

  In the image sensor 13, in the idling operation state, the storage CCD 132 operates so as to sequentially forward the electrical signal (dummy pixel signal) generated by the photoelectric conversion unit 131, as in the case of photographing. However, the pixel signal output from the image sensor 13 by the operation of the transfer CCD 133 is not executed, and the electrical signals that cannot be held in the storage CCD 132 for 100 frames are discarded in the oldest order.

  As described above, in the idling operation state, although the pixel signal is not necessary, the transfer operation is performed by the storage CCD 132 in the photoelectric conversion unit (photodiode) 131 or on the element in the vicinity of the photodiode. This is to prevent noise caused by dark current or the like from accumulating in the accumulation CCD or the like. The transfer operation speed in the storage CCD 132 at this time is set to a sufficiently low speed compared to the transfer operation speed at the time of actual photographing. For example, even when the transfer rate at the time of actual shooting is 100 Mfps, the transfer rate at the idling operation is set to 30 fps. This is because when the accumulating CCD 132 operates at a high speed such as 100 Mfps, the amount of heat generation is large, the temperature inside the element increases rapidly, and the duration of the idling operation cannot be extended. That is, by performing the idling operation at a low operating speed, accumulation of noise can be prevented, and the idling operation can be continued for a long time while suppressing the amount of heat generation.

This point will be supplementarily described with reference to FIG. Now, when the start of shooting standby is instructed at time 0 and the idling operation is started, the temperature of the image sensor 13 (element temperature) rises relatively slowly as indicated by A in FIG. On the other hand, when a high-speed shooting operation is performed as will be described later, the element temperature rapidly rises as indicated by B in FIG. _Assuming that the _limit temperature at which the image sensor 13 does not fail is T _limit , when idling is performed immediately after the start of shooting standby at the same operating speed as during high-speed shooting operation, the element temperature exceeds the limit temperature T _{limit in a} short time. End up. On the other hand, by performing idling at a low speed operation, the imaging standby time becomes longer.

Of course, since the heat generation in the image sensor 13 cannot be ignored at all even in the low speed operation, the continuation time of the idling operation is determined in advance and the continuation time has elapsed (YES in step S3). The timing controller 17 controls the image sensor 13 to temporarily stop the idling operation (step S8). In FIG. 4, if it is possible to estimate the temperature rise ΔT during the period from the start of shooting to the end of shooting, the element temperature may exceed the limit temperature T _limit when shooting is performed if the duration of idling operation exceeds t3. is there. Therefore, the continuable time can be set as t3. Of course, since it is actually necessary to consider differences in various conditions such as the ambient temperature, it is preferable to determine the continuation time in consideration of the most severe conditions.

  Before the predetermined time t3 of step S3 elapses, there is a beginning of a phenomenon to be photographed on the subject, and when this is detected by the external sensor 2 and a detection signal is input to the trigger signal generator 18, the trigger signal generator 18 generates a shooting start trigger and sends it to the timing control unit 17. When the timing control unit 17 recognizes that there is a shooting start trigger (YES in step S4), it drives the image sensor 13 to perform high-speed shooting operation (step S5). When the high-speed shooting operation is started (time t1 in FIG. 4), the image sensor 13 sequentially forwards an electrical signal corresponding to the amount of light incident on the photoelectric conversion unit 131 to the storage CCD 132, and is obtained first immediately after the start of shooting. When the electrical signal is stored in the last stage (100th stage) CCD of the accumulating CCD 132, that is, when pixel signals for 100 frames are obtained (YES in step S6), the photographing is finished (FIG. 4). Time t2). Simultaneously with the end of shooting, the shutter drive unit 12 controls the shutter 11 to close (step S7).

  After the photographing is completed, the timing control unit 17 drives the transfer CCD 133 in the image sensor 13, sequentially reads out the pixel signals for 100 frames held in the storage CCD 132, and transfers them to the image processing unit 14 (step S8). ). Since this signal reading can only be performed at low speed, it takes a certain amount of time to read out the image signals for 100 frames. On the other hand, the closing operation of the shutter 11 is not performed so fast, and the shutter 11 is closed during signal readout, but this prevents the incident light to the image sensor 13 from being blocked and prevents an increase in noise in the element 13. Can do.

  In the image processing unit 14, pixel signals sequentially read from the image sensor 13 are converted into digital data, further appropriately processed and stored in the storage unit 15. When the photographer performs a predetermined operation from the operation unit 16, image data is read from the storage unit 15 and sent to the monitor 3, and high-speed 100 frames of images can be reproduced in slow motion.

  In the above embodiment, the idling operation is stopped only after the lapse of time from the start of the idling operation. However, when the temperature of the image sensor is detected by the temperature sensor and the temperature exceeds a predetermined value, the idling operation is performed. It is also possible to use a control that temporarily stops the operation.

  The above-described embodiment is an example of the present invention, and it is obvious that the present invention is encompassed by the claims of the present application even if appropriate modifications, changes and additions are made within the scope of the present invention.

The block diagram of the principal part of the high-speed imaging device by one Example of this invention. FIG. 3 is a schematic timing diagram for explaining the operation of the high-speed imaging device according to the present embodiment. The figure which shows an example of the flowchart of the imaging | photography procedure using the high-speed imaging device of a present Example. The figure which shows typically the temperature change of the image pick-up element in the high-speed imaging device of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... High-speed imaging device 10 ... Imaging lens 11 ... Shutter 12 ... Shutter drive part 13 ... Imaging element 131 ... Photoelectric conversion part 132 ... CCD for accumulation | storage
133 ... CCD for transfer
DESCRIPTION OF SYMBOLS 14 ... Image processing part 15 ... Memory | storage part 16 ... Operation part 17 ... Timing control part 18 ... Trigger signal generation part 2 ... External sensor 3 ... Monitor

Claims (2)

A high-speed imaging device that includes an imaging unit that photoelectrically converts a captured optical image of a subject and outputs the signal as an electrical signal, and that processes the electrical signal output from the imaging unit as a captured image,
a) start trigger generating means for generating a trigger signal for giving an instruction to start photographing;
b) Stand by in an idling state that repeats the operation at a lower speed than the shooting operation described later until the trigger signal is given, and drives the imaging means so as to shift to the shooting operation at a high speed when the trigger signal is given. Photographing control means;
A high-speed photographing apparatus comprising:   The high-speed imaging apparatus according to claim 1, wherein the imaging unit includes a signal accumulation unit that accumulates an electrical signal for a predetermined number of frames without outputting the signal to the outside, and the imaging control unit includes: The imaging means is controlled to end the imaging when the electrical signal corresponding to the optical image of the predetermined number of frames is accumulated in the signal accumulation unit after the imaging is started in response to the input of the trigger signal. A high-speed imaging device.

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