JP4921120B2 - Solid-state imaging device - Google Patents

Description

  The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device suitable for capturing a two-dimensional image whose state changes at high speed, such as an explosion phenomenon or a combustion phenomenon.

  As a device that captures two-dimensional images of high-speed phenomena such as explosion, destruction, and combustion, a high-speed imaging device (high-speed video) equipped with a high-speed imaging device with a recording time of 1 microsecond (1 million images per second). Camera) is used for scientific measurement and the like. An imaging apparatus that captures such a high-speed phenomenon is proposed in Patent Document 1.

  In this imaging apparatus, for example, 80,000 pixels of oblique linear CCD type pixel peripheral recording imaging elements (hereinafter, abbreviated as ISIS) are arranged in a matrix form along a two-dimensional array line. In each pixel, one signal extraction gate that is extracted for each electronic shutter is connected to one photodiode that generates an electric signal corresponding to the light intensity of incident light to be detected. After this signal extraction gate, a CCD device having a CCD cell for transferring, as image information, an electric signal output from the photodiode by the signal extraction gate for each electronic shutter is attached.

  When an optical image of a subject is captured via an optical lens and projected onto a pixel, an electrical signal output from a photodiode for each electronic shutter for obtaining image information of one screen is converted into a charge in each pixel. Then, the signal is taken out from the signal take-out gate and sent to the CCD device one after another. When the charges are transferred horizontally, the charges in the CCD cells are simultaneously transferred vertically to the CCD cells one stage below. Then, when it is transferred again horizontally, the transfer operation in which the charges of the CCD cells are all transferred to the CCD cells one stage below at a time is repeated. While the electronic shutter is continuously repeated, the charge from each photodiode is accumulated in all the CCD cells. As a result, the image signal for one screen is stored at a high speed in the CCD device attached to the photodiode. In the oblique linear CCD type pixel peripheral recording image sensor (ISIS), a CCD device is attached obliquely to form a recording unit (memory unit).

  By operating as described above, charges are transferred in parallel for each electronic shutter, and charges for image information are accumulated in the CCD device at high speed. In the case of high-speed imaging, it is difficult to read out while accumulating charges. Therefore, after the electronic shutter is stopped, the charges accumulated in the CCD device are read out from the readout electrode. The read charges are digitized at a subsequent stage of the high-speed image sensor, and then an electric signal obtained by the same electronic shutter is edited into one screen to create and display a two-dimensional image.

JP-A-2005-45608

  The photographing speed of the conventional high-speed image sensor described above is proportional to the speed of the electronic shutter (electronic exposure) and the parallel transfer speed of charges in the CCD device. However, if the parallel transfer rate of charges in the CCD device is increased, the CCD device generates heat and noise increases.

  Accordingly, an object of the present invention is to provide a solid-state imaging device in which noise generation due to heat generation is reduced when charges in a CCD device taken at high speed are transferred to a storage unit at high speed.

In order to solve the above-described problems, a solid-state imaging device according to the present invention includes an optical system that captures an optical image of a subject, an imaging element unit that generates a two-dimensional image information by photoelectrically converting the optical image, and a recording unit. In a solid-state imaging device comprising: a CCD solid-state imaging device, a temperature detection unit that detects the temperature of the imaging device unit, an electronic cooling unit that cools the imaging device unit, and a control unit.
When the detected temperature from the temperature detection unit is a temperature within a predetermined operating range, the control unit starts cooling the electronic cooling unit in response to a trigger standby signal for preparing for high-speed shooting. Control to cool the image sensor unit, and if the cooling supply current to the electronic cooling unit exceeds a predetermined value or the detected temperature exceeds a predetermined value, control to set the image sensor to a low speed mode It is characterized by doing.

  According to the present invention, instead of constantly cooling the image pickup device electronically, the image pickup device portion starts to be electronically cooled by a trigger standby signal, and only at the time of high-speed transfer of charges obtained by high-speed shooting to the recording portion. Since the image sensor unit is electronically cooled, deterioration of the electronic cooling due to the heat radiation of the electronic cooling becomes after the signal charge transfer of the high-speed imaging, so that the effective efficiency of the electronic cooling is improved and noise due to the heat generation is reduced. Mixing in video signals can be reduced.

  Hereinafter, an embodiment of a solid-state imaging device of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an image of a subject at a high speed of 1 million frames per second (that is, 1 μsec. For one screen). It is a block diagram which shows the structure of the solid-state imaging device of this embodiment which can image.

  As shown in FIG. 1, a solid-state imaging device capable of high-speed shooting includes an optical system 1 such as an optical lens or a prism that captures an optical image of a subject, and two-dimensional image information by photoelectrically converting the captured optical image. Image sensor 2 for generating image, correlated double sampling (CDS: Correlated Double Sampling) for extracting baseband signal from output signal of image sensor 2, variable gain (AGC: Automatic Gain Control), and analog / digital conversion A front end processor (FEP) 7 that performs (ADC), an image processing unit 8 that performs digital conversion of a correlated double sampled signal, performs image processing, recording, output processing, and the like, and an image sensor unit 2 at a specified speed, a temperature detection unit 4 for measuring the heat generation temperature when the image sensor unit 2 is driven at a high speed, and the image sensor unit 2 are connected to a Peltier device. An electronic cooling unit 5 that cools by cooling or the like and a control unit 6 are configured.

  The control unit 6 performs speed control for changing the imaging device unit 2 to the low speed mode based on the relationship between the stable operation illustrated in FIG. 4 and the relationship between the set imaging speed S and the temperature rise T illustrated in FIG. And a function of controlling the cooling current I supplied to the electronic cooling unit 5 based on the temperature detected by the temperature detecting unit 4 to perform speed control for changing the imaging device unit 2 to the low speed mode. The control unit 6 also has a function of outputting predetermined drive information to the drive unit 3 when a trigger signal for performing predetermined high-speed imaging is input.

  In high-speed imaging, since the number of memories is limited, trigger timing is extremely important for capturing a predetermined high-speed video. In general, since it is difficult to accurately capture the trigger timing, if the image sensor unit 2 is operated at a high speed after the trigger is present, the target photographing cannot be performed in time for a predetermined moment.

  Therefore, it is necessary to set the image sensor section 2 to the high speed operation state before the trigger signal is input. However, since the heat generation is high in the high speed operation state, the stable operation time t is limited as shown in FIG.

FIG. 4 is a schematic diagram showing the operation speed and a stable operation region from when the temperature of the image sensor unit 2 rises to the maximum temperature Tmax. In the schematic diagram of FIG. 4, the horizontal axis S represents the imaging speed (frame number / sec), and the vertical axis represents the operation time t. Operation area for stable operation of the image pickup device unit 2, and the speed ^{S p,} maximum allowable operating time tmax and the product is constant expressions, i.e., in ^{S p} × tmax = K, expressed. Moreover, maximum allowable operating time tmax is represented by tmax = K / ^{S p.} Here, K is a constant value and p is a constant.

  FIG. 2 shows the structure of the image sensor unit 2, which is mainly composed of a light receiving element unit 13 of m × n pixels and m × n × 1 memory unit 14 for storing video signals from the light receiving element unit 13. ing.

  FIG. 3 is a schematic diagram of the image sensor section for explaining the operation of the memory section 14 for storing data from one light receiving element in the light receiving element section 13 of the image sensor section 2 shown in FIG. In FIG. 1, when a trigger standby signal is input to the control unit 6, the imaging speed designated by the speed designation signal is given from the control unit 6 to the drive unit 3, and the drive unit 3 starts driving the imaging element unit 2. Then, the high-speed shooting operation ready state (trigger / standby state) is entered.

  In the trigger standby state, data from one pixel of the light receiving element is input as a high-speed image to the memory unit 14 in FIG. 3, and the memory unit 14 also records the high-speed image in conjunction. The portion exceeding the memory number l is discharged to the outside.

  Next, when a trigger signal is input at time t0, the data before the trigger from time t0-i to t0 input before time t0 and the trigger from time t0 to t0 to t0 + j are input to the memory unit 14. Later data is distributed and recorded.

  The data before the trigger and the number of images of the data after the trigger are determined by a preset skipback signal. The skip back signal is input to the control unit 6 in FIG. 1 and is given to the image sensor unit 2 through the drive unit 3. The skip back value can be set according to the purpose.

  Next, in this high-speed imaging state, the higher the speed, the greater the power consumption of the imaging device unit 2 and the temperature rises. The temperature of the image sensor 2 is always detected by the temperature detector 4. The detected value is input to the control unit 6, and the control unit 6 controls the electronic cooling unit 5 to increase the supply of the cooling current of the electronic cooling unit 5 in order to suppress the temperature rise of the imaging element unit 2.

  Here, if the electronic cooling unit 5 constantly cools, the efficiency of electronic cooling is reduced due to the heat radiation from the electronic cooling unit, and the influence of noise on the video signal due to heat generation increases. Controls the electronic cooling of the image sensor unit 2 so that the electronic cooling is performed only during the period in which the charge is transferred to the memory unit 14 in the solid-state image sensor at high speed. Since the signal charges for high-speed imaging are shifted after being transferred to the memory unit 14, the efficiency of performing electronic cooling can be improved, and mixing of noise due to heat generation into the video signal can be reduced.

  However, when the temperature rise of the image sensor unit 2 exceeds the suppression of the temperature rise due to electronic cooling and reaches or approaches the allowable maximum temperature Tmax of the image sensor unit 2 as shown in FIG. 5, or as shown in FIG. When the cooling current I reaches or approaches the maximum cooling current Imax, the control unit 6 sends a signal for canceling the high-speed shooting state to the driving unit 3 and immediately switches the imaging element unit 2 to the low-speed mode. Take control.

  The preferred embodiments have been described above, but it goes without saying that various modifications can be made without departing from the spirit of the present invention. For example, in the embodiment, it has been described that the electronic cooling is performed only during the high-speed transfer period to the recording unit in the solid-state imaging device for high-speed shooting, but the electronic cooling is performed only during the high-speed transfer period, and the predetermined temperature is set. During the above, control may be performed so as to stop high-speed transfer to the recording unit in the solid-state imaging device for high-speed shooting.

1 is a block diagram illustrating a configuration of a solid-state imaging device of the present invention. The block diagram which shows the structure of the image pick-up element part of the solid-state imaging device of this invention. The schematic diagram of the memory operation | movement per pixel of the image pick-up element part of the solid-state imaging device of this invention. The schematic diagram which shows the relationship between the operating speed and operating time of the solid-state imaging device of this invention. The schematic diagram which shows the relationship between the operating speed of the solid-state imaging device of this invention, and temperature rise. The schematic diagram which shows the relationship between the operating speed of the solid-state imaging device of this invention, and a cooling current.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical system, 2 ... Image pick-up element, 3 ... Drive part, 4 ... Temperature detection part, 5 ... Electronic cooling part, 6 ... Control part, 7 ... FEP (front end processor), 8 ... Image processing part (Image processing + (Recording + output), 13... Light receiving element portion, 14... Recording portion (memory portion)

Claims (1)

An optical system for capturing an optical image of a subject;
A CCD solid-state imaging device having an imaging device section and a recording section for generating two-dimensional image information by photoelectrically converting the optical image;
A temperature detection unit for detecting the temperature of the image sensor unit;
In a solid-state imaging device comprising an electronic cooling unit and a control unit for cooling the imaging element unit,
When the detected temperature from the temperature detection unit is a temperature within a predetermined operating range, the control unit starts cooling the electronic cooling unit in response to a trigger standby signal for preparing for high-speed shooting. Control to cool the image sensor unit, and if the cooling supply current to the electronic cooling unit exceeds a predetermined value or the detected temperature exceeds a predetermined value, control to set the image sensor to a low speed mode A solid-state imaging device.

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