With the more strict demand for microscopy imaging in scientific field,CCD imaging equipments get wide attention from scientists and research scholars.However,there are too many brands of camera in this field for you to choose.As a result,some people get confused.When choosing CCD camera,the pixel quantity of the CCD camera is always the the custmers' biggest concerning point.Actually,besides the resolution ratio,there are other performance indexes more worth of attention,such as chip size,pixel dimension,etc.
One:What is CCD
A.CCD is short for Charge Coupled Device.It is a photosensitive element based on MOS(Metal-Oxide-Semiconductor) technology.The element is covered with several sensors,and every sensor is called a pixel.CCD is a of prime importance in a camera,it can transfer light signal into electronic signal,just as what human eyes do.As a result,the performance of the CCD directly decide the performance of the camera.At present,CCD has owned the advantages of wide spectral range,low detection limit,wide dynamic range,low dark current&reading noise,integral signal,multi-channel simultaneously detection and real-time monitoring ability.
B.Conponents of CCD
1st layer”Micro camera”
2ndlayer”Color separation filter”
3rdlayer”Sensitive”
CCD is the light sensitive circuit device just like the negative plates,you can image it as several sensitive particles,covering the backside of the optical lens.When the light and image pass through the lens and shoot to the surface of CCD,it will generate current and transfer the induced contents to digital data to be stored.
Two:Main characters determining the CCD imaging quality
Physical resolution ratio
Chip dimension
Pixel dimension
SNR
Gray value
Physical resolution ratio:CCD's resolution ratio,the pixel is the basic unit of digital image,every pixel is a small point,and the different colour point(pixel)make up a beautiful photo,CCD is always classified and ranked by pixel.As for the same chip dimension,the more pixel means the higher resolution ratio.
Chip dimension:The digital camera has main demension of 2/3'' ,1/1.8'',1/2.7'' etc.The bigger the CCD dimension means the larger the sensitive area and better imaging performance.For example,the performance of 2/3'' 3.0 MP camera is better than the 1/1.8'' 4.0 MP camera(The sensitive area of the latter one is only 70% of the former one ).If we wish to increase the CCD pixel
quantity and maintain current image quality at the same time,we must increase or maintain the single pixel area and increase the total area of the CCD。The more professional camera owns the larger CCD dimension.At present,the larger dimension CCD is hard to process&manufacture and has a extremly high cost.
Pixel point:the basic unit of CCD photosensitive layer.The diameter owns micron level of magnitudes.The more pixel points in unit area will make up more delicate image and higher resolutio ratio.The increasing pixel in the same dimension of CCD is a good thing,however ,if it exceed a certain quantity,it will cause decreasing of sensitive area of single pixel ,insufficient exposure and mutual interference of light signal between each pixel point.This,of cause,will be a backfire for the difinition of image.
SNR:SNR is the ratio between normal light signal and abnormal signal(noise) of CCD.The higher SNR indicates the less abnormal signal and more real and clear image quality.
Gray value:The unit of gray value is Bit which is a term in computer image used for describing the colour quantity included in the generated image.”Depth is 8 bit”means the image only contains 28 that is 256 kind colour.The higher grey value indicates the more grayscale can be distinguished by camera and richer colour.
Three:Preparation for buying a camera
1st step:Clear the purpose and goal of buying a CCD camera
It's important to determine the purpose and goal of buying a CCD camera,only if you know what you need,can you find the machine you really need.Don't be blind to pursuit high pixel and high resolution ratio,just take this as an example,the Black&White CCD camera used for fluorescence shooting will be a satisfactory in 1.0 MP or a little more pixel,since the small quantity of pixel have a excellent performance in sensitization and is just match the feature of low fluorescence.
2nd step:Psychological price
Determing a bearable psychological price according to the quantity of the research fund,30-50 thousand for example,will save us much time and make you more focus when making selection.
3rd step:It's not necessary to buy from microscope manufactures
People like to buy CCD camera when buying a microscope,it's not bad to maintain the systemmatic of the equipment,however,it is sometimes not a good way to save money.Generally speaking,the microscope manufactures will not produce the CCD camera by themselves,they will OEM in other CCD camera manufactures.Why not just find a CCD camera suitable for the microscope with better cost performance and save the money at the same time!JPLY is a professional microscopy CCD camera manufacture and there are agents of JPLY all around the country,you can just take a look at it and I bet it worth it.
4th step:Trial is the best policy
We can only get a perceptual knowledge from the material,only actual using of the machine,can we get the most important rational knowledge.You can make the manufacture representative demonstrate it for you,sometimes the 10.0 MP CCD may not get more clear photos than 5.0MP,trail is the best policy to protect you away from traps.
