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FAQs (CCD) | CCD / CMOS / NMOS image sensors

What are the main differences between MOS image sensor and CCD image sensor usage?

MOS image sensors can generally handle a higher electrical charge compared to CCD image sensors, and are used under high light level conditions. CCDs feature low noise and are more suited for detecting low level light. MOS image sensors are also capable of operating on a 5 V supply which makes them easy to handle.

What components are needed for using CCD image sensors with a PC?

Prepare the following components.

1. Prepare the following components.Multichannel detector head or driver circuit (These products for some CCDs might not be available from us. See the image sensor datasheets or selection guide for detailed information.)

2. Multichannel detector head controller C7557-01 (when using a multichannel detector head): Allows easy data acquisition via USB connection to a PC

3. External power supply, A/D converter (Whether these are required depends on the multichannel detector head and driver circuit. See the datasheets.)

4. Frame grabber board (when using a multichannel detector head with a Camera Link interface)

To what extent do CCD spectral response characteristics listed in the datasheets vary among individual products?

Photosensitivity listed in the datasheets are typical values for product specifications and are not guaranteed values. Front-illuminated CCDs for example have somewhat large variations in spectral response characteristics from product to product because they have a structure where CCD gate electrodes are formed on a surface that receives incident light. Near the visible region, back-thinned CCDs have fewer variations in sensitivity compared to the front-illuminated type. In the ultraviolet region however, they exhibit large variations.
If spectral response characteristics for individual products are needed, then consult our sales office nearest you. Please note that spectral response characteristics depend on temperature. See our technical guide for information on the temperature dependence of spectral response characteristics.

In what sequence should power to a CCD be turned on?

We recommend first turning on the DC power to the CCD and then applying the power to the clock system. Turning on power in the reverse sequence or at the same time is not likely to harm the CCD.

How does overlapping of CCD two-phase clock pulses (P1, P2) affect operation?

It is recommended that the clock pulses overlap each other at 50%±10% of their amplitudes. Operation deviating from this condition may affect the saturation charge and charge transfer efficiency, so take this into account if high detection accuracy is required.

Can I use any voltage if it is within the voltage range of the operating conditions listed in the CCD datasheet?

CCD characteristics vary with operating conditions. Operating conditions specified in the datasheet show the adjustment range. They must be adjusted within the specified range. We recommend using the CCD under typical operating conditions. Electrical and optical characteristics listed in the datasheet are the values when used under typical operating conditions.

Are CCDs sensitive to X-rays?

When X-rays are directly incident on a CCD, the front-illuminated type is sensitive to X-rays from 0.5 keV to 10 keV, and the back-thinned type is sensitive from 0.1 keV to 10 keV. Front-illuminated CCDs coupled to an FOS (FOP coated with scintillator) or phosphor sheet are sensitive to X-rays of several ten keV or higher. See our technical information for details. If detecting X-rays at other energy levels, consult our sales office nearest you.

CCD datasheets do not list the sensitivity in terms of voltage output (unit: V). How can it be calculated?

Datasheets contain a graph showing spectral response characteristics [vertical axis: quantum efficiency (QE)] and CCD node sensitivity (Sv). The voltage output at particular wavelengths can be calculated from the quantum efficiency and CCD node sensitivity. This calculation formula is as follows:

V = Number of incident photons × QE × Sv

Is a shutter required when capturing images with a CCD?

When capturing two-dimensional images with an FFT-CCD, its operating principle requires a shutter or similar mechanism to block light so that no light strikes the CCD during charge transfer. (This is to prevent light striking the CCD during charge
transfer from being read out as a signal because the photosensitive area of an FFT-CCD also serves as a charge transfer register.) The signal produced by light incident on the CCD during charge transfer appears like vertical stripes in the acquired image. (This phenomenon is called smear.) If the charge integration time is extremely long compared to the readout time, then there is relatively little shading effect, so the desired image can be acquired even without a shutter.
When operating an FFT-CCD in binning mode, the light incident on the CCD during charge transfer is added to the signal by binning and is read out as one-dimensional data, so there is no problem if used without a shutter.

Flaws not described on the inspection sheet can be seen in the detected image. Why is that?

The inspection sheet conditions are shown on the datasheet. Compare the device using conditions close to those inspection conditions.
Abnormal phenomena that did not occur at the time of shipping inspection might occur due to damage (electrostatic discharge damage or deterioration caused by surge) during handling by the customer or due to unavoidable problems (caused by effects from cosmic rays, etc.) during shipping, so please consult our sales office.

Will problems occur from using a CCD in vacuum?

There is no problem at all when using a front-illuminated CCD with no window under a vacuum of several pascals. However, at vacuum levels higher than approximately 10-2 pascals, the system may sometimes become contaminated from resin and so on, so please consult us. Back-thinned CCDs have also been used in vacuum, so please consult us if using them in vacuum.

Can a CCD be coupled to an FOP?

Nearly all front-illuminated CCDs can be coupled to an FOP.
However, back-thinned CCDs cannot be coupled to an FOP. Please consult our sales office for more details.

To what level should temperature and humidity be maintained during handling of a CCD?

To find the temperature range, see the operating temperatures and storage temperatures listed in the datasheet. The temperature and humidity must meet the conditions that will not cause moisture condensation on the sensor. Using at a humidity from 45% to 55% is recommended. Use in this recommended humidity range is also necessary as an ESD countermeasure.

What measures are required to avoid ESD (electrostatic discharge damage) during handling of a CCD?

Static electricity can destroy a CCD, so care is required during handling. We recommend using a workbench fitted with ESD
countermeasures, wrist straps, conductive mats, etc. Use of an ionizer is also recommended to remove static electricity that may be generated during handling. See the "Precautions" of CCD image sensors for detailed information.

Where should a CCD be stored?

See the "Precautions" of CCD image sensors for the instructions on how to store a CCD. After unpacking, we recommend storing in a low humidity desiccator.

Can incident light damage the CCD?

Visible light cannot damage the CCD. However, ultraviolet light, X-rays and other high-energy radiation can cause damage.
See our technical information for details.

CCDs still generate an output even if the charge integration time is zero. Why is that?

CCDs generate dark current even during readout operation. So even if the charge integration time is zero, there is still an output including dark current.

What is the reason for the large tolerance on CCD packages?

The packages mainly use ceramic materials, so manufacturing the package within a small tolerance is difficult. In view of quality control, the package tolerance is set to a large figure. Special processing techniques may make the package tolerance smaller, so consult us if needed.

Multichannel detector heads (camera heads) are not available for some CCD types. Any suggestions on how to use those CCDs?

Multichannel detector heads are not available for some CCD types, but simple evaluation circuit boards may be available for them. Contact our sales office for more information.

Can CCDs with custom specifications such as low dark current or minimum blemishes be chosen for purchase?

Custom specifications may be available at extra cost for some CCDs. Please contact our sales office if needed.

Can you provide CCD image sensors with no flaws or blemishes on the photosensitive surface?

Types with no flaw or blemish may be available at extra cost for some CCDs. Please contact our sales office if needed.

Can I purchase flawed CCDs at a low price?

Some CCD types with flaws or blemishes may be available. Please contact our sales office if necessary.

I need data other than those shown in the inspection sheet. Can you supply such data with the product when shipping?

If that data can be prepared, then we will provide it for a fee.

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