Charge-Coupled Devices (CCDs)

(or: How My Digital Camera Works)

Elizabeth Castelli
Manhattan East Middle School

Summer Research Program for Science Teachers
August 2009

Introduction: Cell phones, digital cameras, telescopes -- think of a digital device that can take a picture and it probably has a CCD in it. CCDs are used to capture and digitalize images. In this activity we will learn just how a CCD converts photons of light into digital memory.


- Understand how CCDs are constructed, collect light, and create a digital signal.

- Illustrate how a CCD collects photons given a variety of conditions.

- Describe sources of CCD noise and their causes.

            1. read noise

            2. dark current

3. cosmic rays


A lot of beans

  - 25 small paper cups

  -1 baseball

  - Paper and pencil

  - Charged-Coupled Devices Handout

  - Mini-Quiz



1. Using the handout titled, “Charge-Coupled Devices – CCDs”, read the “How it Works Section” with students aloud and identify the parts of the CCD as they relate to the demo:

            - one cup = one pixel

            - each bean = one electron

            - baseball = cosmic ray

            - paper = lens cap


2. Have each group gather their supplies and set up their rows of cups. Make sure students set up a 5 by 5 grid of cups and have enough beans to fill at least 6 cups. Each group also needs a baseball and a piece of paper.


3. Have students work though each of the scenarios, first using the beans and cups to see what is going on, and then answering the questions as a group aloud.


4. Go over the correct scenario and answers with the class before moving on to the next scenario.


5. Complete quiz as a wrap up, or the next day as a “do now” to asses student learning and/or retention.



 NYS Physical Setting Core Curriculum


S6. Interconnectedness: Common Themes: Models
            Key Idea 2: Models are simplified representations of objects, structures, or systems used in analysis, explanation, interpretation, or design.


S7. Interdisciplinary Problem Solving: Strategies

            Key Idea 2: Solving interdisciplinary problems involves a variety of skills and strategies, including effective work habits; gathering and processing information; generating and analyzing ideas; realizing ideas; making connections among the common themes of mathematics, science, and technology; and presenting results

S4. Students will understand and apply scientific concepts, principals, and theories pertaining to the phyical setting.

  Key Idea 1: Performance Indicator 1.2: Describe current theories about the origin of the universe and solar system.

                             Major Understandings: 1.2a The universe is vast and estimated to be over ten billion years old. The current theory is that the universe was created from an explosion called the Big Bang. Evidence of this theory includes:

         1. cosmic background radiation

                   2. a red-shift (the Doppler effect) in the light from very distant galaxies