CN101674416B - Method for reducing noise and increasing gain of low-illuminance cameras - Google Patents
Method for reducing noise and increasing gain of low-illuminance cameras Download PDFInfo
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- CN101674416B CN101674416B CN2008101421943A CN200810142194A CN101674416B CN 101674416 B CN101674416 B CN 101674416B CN 2008101421943 A CN2008101421943 A CN 2008101421943A CN 200810142194 A CN200810142194 A CN 200810142194A CN 101674416 B CN101674416 B CN 101674416B
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Abstract
The invention discloses a method for reducing noise and increasing gain of low-illuminance cameras, which applies to low-illuminance or super-sensitivity cameras. The method is based on a camera adopting a charge-coupled image sensor. The method comprises: connecting the image signal output end of the charge-coupled image sensor with a relevant secondary sampling-holding circuit and dividing image signals after entering the relevant secondary sampling-holding circuit into two paths of signals through two capacitors, wherein one path of signals is a top circuit, and the other path of signals is a bottom circuit; connecting XSHP sampling pulses and XSHD sampling pulses to the top circuit and the bottom circuit respectively; and connecting the output parts of the top circuit and the bottom circuit with a differential amplifier. The method has the advantage of ensuring that the low-illuminance cameras can be greatly improved in sensitivity to external light, can show optimal effects in various illumination environments, and can still clearly identify images and display real-time continuous pictures even in very dark environments.
Description
Technical field
The present invention relates to the method that a kind of video camera reduces noise and increasing gain, a kind of method of reducing noise and increasing gain of low-illuminance cameras when particularly object place ambient light illumination is low.
Background technology
Low-illuminance cameras has existed for many years on market, from day and night color/monochrome suitching type, the slow-speed shutter image accumulation formula of earliest, or adopts ultra-low illumination CCD, until present popular infrared ray light-projecting type video camera is of a great variety.Yet not having a kind of method is its not enough place.Introduce on the market existing several kinds low below and release souls from purgatory video camera:
1. day and night type:
This type of video camera still has certain market demand at present on market.It is characteristics of utilizing black-and-white image higher to the infrared ray sensitivity, in certain light source condition, utilizes circuit-switched mode to transfer image to black and white by colour, so that the collocation infrared ray.
In the technological evolution process of colour/black and white line transfer; This type of video camera has adopted single CCD colored designs, by day or light source be colour TV camera when sufficient, come or light source utilizes digit circuit that colour signal is eliminated when not enough when night; Become black-and-white image; And for the infrared ray of arranging in pairs or groups, also cancelled the obligato infrared ray stripper of colour TV camera, real " low-illuminance cameras " should refer to the assembly and the accessible function of technology that video camera itself is adopted; And daytime is colored, evening black and white video camera because of being subject to the CCD sensitivity; Assembly itself also can't change, just utilize circuit to switch and the mode of collocation infrared light with functional promotion, can not be at last truly low-illuminance cameras.
2. slow-speed shutter formula:
This type of video camera is called accumulation type video camera or picture accumulation type video camera again; It is the technology of utilizing the computer memory body; Accumulate because of insufficient light shows fuzzy picture several continuously; Become the picture of an image definition, the illumination that the slow fast gate technique of utilization reduces video camera is to 0.008LUX/F1.2 (128), and picture can accumulate maximum frame number be 128 frames.This type of low-illuminance cameras is applicable to forbids museum red, that ultraviolet ray destroys; The biological activity at night is observed; Military coastline supervision at night etc.; The supervision in the more static place of attribute, but to taking the photograph image content requirement smoothness and real-time and dynamic monitoring environment, this type of low-illuminance cameras just can not meet the demands.
3. low-illuminance cameras:
This type of video camera is also claimed 24 hours video cameras; Employing charge-coupled device (CCD) technology, its colored illumination generally can reach 0.05LUX, and black and white then generally can reach 0.003-0.001LUX; But under some special photoenvironments; When particularly environment was very dark, the light sensitive degree of video camera was low, on picture, was difficult to recognize into some concrete objects.
4. infrared ray light-projecting type video camera:
This type of video camera adds video camera on the basis of original low-illuminance cameras and joins the infrared ray light projector; Be the low-illuminance cameras that adopts infrared ray light-projecting type charge coupled device (Exview HAD CCD) technology; The sensitivity of light can improve greatly to external world; At near infrared region, its sensitivity can be brought up to 4 times of common camera.Under the monitoring environment of 0 illumination, under the promptly unglazed fully situation, also can on picture, obtain object picture more clearly.But during practice; Camera chain system signal can include the reset noise that action causes comprising because of Reset because of the output of initial charge coupled apparatus; And because of descending with the strong and weak image quality that luminance signal produced that changes of light signal; Make the whole system signal-to-noise ratio occur worsening, but be difficult to eliminate.
Summary of the invention
The technical problem that the present invention will solve is; The camera chain system signal that exists to ultra-low illumination video camera in the prior art can cause comprising the reset noise because of the output of initial charge coupled apparatus includes because of Reset moves; And because of descending with the strong and weak image quality that luminance signal produced that changes of light signal; And make the whole system signal-to-noise ratio defective that worsens occur, and reach the reset noise that makes whole camera system to eliminate fully, make the low-light (level) characteristic obtain better to improve; Effectively the minimal illumination of elevator system obtains the image brilliance of high s/n ratio and exports signal.
The present invention has overcome shortcoming of the prior art, and a kind of method of reducing noise and increasing gain of low-illuminance cameras is provided, and said method is based on the video camera that adopts charge-coupled image sensor, and said method comprises:
A. the image signal output end at charge-coupled image sensor connects relevant secondary sample holding circuit;
B. after picture signal gets into relevant secondary sample holding circuit, be divided into two-way by two electric capacity, the one tunnel is the top circuit, and one the tunnel is the below circuit;
C. XSHP sampling pulse and XSHD sampling pulse are inserted top circuit and below circuit respectively;
D. then up output place of circuit and below circuit be connected differential amplifier.Among the said step C, the XSHP sampling pulse is preceding, the XSHD sampling pulse after.
Among the said step C, the XSHP sampling pulse triggers the first electronic circuit SH1, and the XSHD sampling pulse triggers the second electronic circuit SH2, the 3rd electronic circuit SH3.
The said first electronic circuit SH1 and the second electronic circuit SH2 tandem connection insert in the circuit of top.
Said the 3rd electronic circuit SH3 inserts in the circuit of below, and its output connects differential amplifier.
The operating frequency of said XSHD sampling pulse, XSHP sampling pulse and charge-coupled image sensor is identical.
Compared with prior art, utilize the method for the invention can make low-illuminance cameras to external world the sensitivity of light improve greatly, to all showing best effect under the various photoenvironments; Even under very dark environment; Also can debate the knowledge image clearly, show the picture of real-time continuous, particularly behind the infrared illumination equipment of cooperation special use; Under unglazed fully environment, also can obtain the black and white image of high definition, realize the monitoring of zero illumination.
Description of drawings
Fig. 1 is the circuit diagram of the method for a kind of reducing noise and increasing gain of low-illuminance cameras of the present invention;
Fig. 2 is the picture signal output sketch map of the method for a kind of reducing noise and increasing gain of low-illuminance cameras of the present invention;
Fig. 3 is the correlated double sampling and holding circuit electrical schematic diagram of the method for a kind of reducing noise and increasing gain of low-illuminance cameras of the present invention;
Fig. 4 is the signal to noise ratio and the sensitivity comparison diagram of the method for a kind of reducing noise and increasing gain of low-illuminance cameras of the present invention.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail.
To shown in Figure 3, the invention provides a kind of method of reducing noise and increasing gain of low-illuminance cameras like Fig. 1, said method is based on the video camera that adopts charge-coupled image sensor 6, and said method comprises:
A. the image signal output end at charge-coupled image sensor 6 connects relevant secondary sample holding circuit;
B. after picture signal gets into relevant secondary sample holding circuit, be divided into two-way by two electric capacity, the one tunnel is the top circuit, and one the tunnel is the below circuit;
C. XSHP sampling pulse 1 and XSHD sampling pulse 2 are inserted top circuit and below circuit respectively;
D. then up output place of circuit and below circuit be connected differential amplifier 7.
The image signal output end of initial charge coupling imageing sensor 6 includes reset noise that is caused because of the Reset action and the luminance signal that changes with the light signal power; The reset noise is the main cause of whole signal-to-noise ratio degradation; Must eliminate; The method of the invention utilizes XSHP sampling pulse 1 to take out the reset noise, takes out the luminance signal size with XSHD sampling pulse 2, again via behind the low noise automatic gain amplifier 10; Can the reset noise be eliminated fully, obtain the image brilliance output signal of high s/n ratio.
Among the said step C, XSHP sampling pulse 1 is preceding, XSHD sampling pulse 2 after.
Among the said step C, XSHP sampling pulse 1 triggers the first electronic circuit SH13, and XSHD sampling pulse 2 triggers the second electronic circuit SH24, the 3rd electronic circuit SH35.
The said first electronic circuit SH13 and the second electronic circuit SH24 tandem connection insert in the circuit of top.
Said the 3rd electronic circuit SH35 inserts in the circuit of below, and its output connects differential amplifier 7.
Said XSHD sampling pulse 2, XSHP sampling pulse 1 are identical with the operating frequency of charge-coupled image sensor 6.
As shown in Figures 2 and 3, the correlated double sampling is divided into two loops after being coupled with C2 via capacitor C 1 with holding circuit output, and last side hydraulic circuit (top circuit) is by the reverse operational amplifier and the first electronic circuit SH13, and the first electronic circuit SH24 forms.Following side hydraulic circuit (below circuit) is made up of the reverse operational amplifier and the first electronic circuit SH35; When 1 action of XSHP sampling pulse; The output of U4 can obtain RESET noise level 8; Next when 2 actions of XSHD sampling pulse; U6 can obtain effective luminance signal image position standard 9, and U5 still can obtain original RESET noise level, via effective signal of video signal output that can obtain authentic representative brightness behind the differential operational amplifier 7.
As shown in Figure 3; The said first electronic circuit SH13 comprises first amplifier; The output of this first amplifier connects second electronic circuit; This first amplifier input terminal is through the reverse operational amplifier of bridge rectifier (74HC4066 cake core) the connection top circuit of first electronic circuit, and wherein three nodes of the 74HC4066 cake core of first electronic circuit connect XSHP sampling pulse, power supply input and ground connection respectively; Said first amplifier input terminal is through capacity earth, and two supply pins of said first amplifier are except that connecting power supply, also respectively through ground connection behind the electric capacity; The said second electronic circuit SH24 comprises second amplifier; The output of this second amplifier connects differential amplifier 7; This second amplifier input terminal connects the output of first amplifier through the 74HC4066 cake core of second electronic circuit, and a node of the second electronic circuit 74HC4066 cake core connects the 3rd electronic circuit, and said first amplifier input terminal is passed through capacity earth; Two supply pins of said first amplifier are except that connecting power supply, also respectively through ground connection behind the electric capacity; Said the 3rd electronic circuit SH35 comprises the 3rd amplifier; The output of the 3rd amplifier connects differential amplifier 7; The 3rd amplifier input terminal is through the reverse operational amplifier of the 74HC4066 cake core connection below circuit of the 3rd electronic circuit, and wherein a node of the 74HC4066 cake core of the 3rd electronic circuit connects a node of 74HC4066 cake core in second electronic circuit, simultaneously; This node also connects the XSHD sampling pulse; Said the 3rd amplifier input terminal is through capacity earth, and two supply pins of said the 3rd amplifier are except that connecting power supply, also respectively through ground connection behind the electric capacity;
Its maximum magnification ratio of pre-amplifier of the prior art is generally+31db; The specific noise that image signal output end comprised of the relevant secondary sample circuit for eliminating initial charge coupling of the method for the invention utilization imageing sensor 6 can promote amplifier gain+6db again.
As shown in Figure 4, the present invention and the prior art difference in signal to noise ratio and sensitivity lifting can be seen very clearly that by Fig. 4 the amplifier gain that designs by the method for the invention has promoted+6db.Its signal to noise ratio can remain unchanged.
The method of the invention make low-illuminance cameras to external world the sensitivity of light can improve greatly; To all showing best effect under the various photoenvironments,, also can debate the knowledge image clearly even under very dark environment; The picture that shows real-time continuous; After particularly cooperating special-purpose infrared illumination equipment, under unglazed fully environment, also can obtain the black and white image of high definition, realize the monitoring of zero illumination.At the near infrared region of near-infrared 760mm-1100mm,, just can realize black and white image clearly if cooperate the infrared illumination of suitable wavelength.Above content is to combine concrete preferred implementation to the further explain that the present invention did, and can not assert that practical implementation of the present invention is confined to these explanations.For the those of ordinary skill of technical field under the present invention, under the prerequisite that does not break away from the present invention's design, can also make some simple deduction or replace, all should be regarded as belonging to protection scope of the present invention.
Claims (6)
1. the method for a reducing noise and increasing gain of low-illuminance cameras, said method is characterized in that based on the video camera that adopts charge-coupled image sensor said method comprises:
A. the image signal output end at charge-coupled image sensor connects relevant secondary sample holding circuit;
B. after picture signal gets into relevant secondary sample holding circuit, be divided into two-way by two electric capacity, the one tunnel is the top circuit, and one the tunnel is the below circuit; Said top circuit is by the reverse operational amplifier and the first electronic circuit SH1, and the second electronic circuit SH2 forms; Said below circuit is made up of reverse operational amplifier and the 3rd electronic circuit SH3; The said first electronic circuit SH1 comprises first amplifier; The output of this first amplifier connects second electronic circuit; This first amplifier input terminal is through the reverse operational amplifier of the 74HC4066 cake core connection top circuit of first electronic circuit, and three nodes of this first electronic circuit 74HC4066 cake core connect XSHP sampling pulse, power supply input and ground connection respectively; Said first amplifier input terminal is through capacity earth, and two supply pins of said first amplifier are except that connecting power supply, also respectively through ground connection behind the electric capacity; The said second electronic circuit SH2 comprises second amplifier; This second amplifier input terminal connects the output of first amplifier through the 74HC4066 cake core of second electronic circuit; A node of the 74HC4066 cake core of this second electronic circuit connects the 3rd electronic circuit; Said second amplifier input terminal is through capacity earth, and two supply pins of said second amplifier are except that connecting power supply, also respectively through ground connection behind the electric capacity; Said the 3rd electronic circuit SH3 comprises the 3rd amplifier; The 3rd amplifier input terminal connects the reverse operational amplifier of below circuit through the 74HC4066 cake core of the 3rd electronic circuit; Wherein a node of the 74HC4066 cake core of the 3rd electronic circuit connects a node of 74HC4066 cake core in second electronic circuit; Simultaneously, this node of the 74HC4066 cake core of the 3rd electronic circuit also connects the XSHD sampling pulse, and said the 3rd amplifier input terminal is passed through capacity earth; Two supply pins of said the 3rd amplifier are except that connecting power supply, also respectively through ground connection behind the electric capacity;
C. XSHP sampling pulse and XSHD sampling pulse are inserted top circuit and below circuit respectively;
D. then the output of second amplifier and the 3rd amplifier is connected differential amplifier respectively.
2. the method for a kind of reducing noise and increasing gain of low-illuminance cameras according to claim 1 is characterized in that:
Among the said step C, the XSHP sampling pulse is preceding in chronological order, the XSHD sampling pulse after.
3. the method for a kind of reducing noise and increasing gain of low-illuminance cameras according to claim 1 is characterized in that:
Among the said step C, the XSHP sampling pulse triggers the first electronic circuit SH1, and the XSHD sampling pulse triggers the second electronic circuit SH2, the 3rd electronic circuit SH3.
4. the method for a kind of reducing noise and increasing gain of low-illuminance cameras according to claim 3 is characterized in that:
The said first electronic circuit SH1 and the second electronic circuit SH2 tandem connection insert in the circuit of top.
5. the method for a kind of reducing noise and increasing gain of low-illuminance cameras according to claim 3 is characterized in that:
Said the 3rd electronic circuit SH3 inserts in the circuit of below, and its output connects differential amplifier.
6. the method for a kind of reducing noise and increasing gain of low-illuminance cameras according to claim 1 is characterized in that:
The operating frequency of said XSHD sampling pulse, XSHP sampling pulse and charge-coupled image sensor is identical.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008101421943A CN101674416B (en) | 2008-09-11 | 2008-09-11 | Method for reducing noise and increasing gain of low-illuminance cameras |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2008101421943A CN101674416B (en) | 2008-09-11 | 2008-09-11 | Method for reducing noise and increasing gain of low-illuminance cameras |
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| CN101674416A CN101674416A (en) | 2010-03-17 |
| CN101674416B true CN101674416B (en) | 2012-01-04 |
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| CN104092924A (en) * | 2014-04-30 | 2014-10-08 | 武汉博睿达信息技术有限公司 | VMS video sharpening processing network system framework under low illumination and pre-detection method |
| TWI672954B (en) * | 2017-06-12 | 2019-09-21 | 晶相光電股份有限公司 | Readout circuit and sensing device |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1166103A (en) * | 1996-04-17 | 1997-11-26 | 三星电子株式会社 | Method and circuit for reducing noise |
| US5850257A (en) * | 1994-05-20 | 1998-12-15 | Canon Kabushiki Kaisha | Noise reduction device employing a sample and hold circuit, and an image pickup device using the noise reduction device |
| CN1437392A (en) * | 2002-02-07 | 2003-08-20 | 富士通株式会社 | Correlation secondary sampling circuit and CMOS image sensor containing the same circuit |
| CN101160956A (en) * | 2005-04-14 | 2008-04-09 | 美光科技公司 | Multi-point correlated sampling for image sensors |
-
2008
- 2008-09-11 CN CN2008101421943A patent/CN101674416B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5850257A (en) * | 1994-05-20 | 1998-12-15 | Canon Kabushiki Kaisha | Noise reduction device employing a sample and hold circuit, and an image pickup device using the noise reduction device |
| CN1166103A (en) * | 1996-04-17 | 1997-11-26 | 三星电子株式会社 | Method and circuit for reducing noise |
| CN1437392A (en) * | 2002-02-07 | 2003-08-20 | 富士通株式会社 | Correlation secondary sampling circuit and CMOS image sensor containing the same circuit |
| CN101160956A (en) * | 2005-04-14 | 2008-04-09 | 美光科技公司 | Multi-point correlated sampling for image sensors |
Non-Patent Citations (1)
| Title |
|---|
| JP特开2004-357046A 2004.12.16 |
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