It is very important to measure the width of cracks in concrete for monitoring the status of buildings and avoiding fatal damages of concrete structure. In order to remedy some defects such as the difficulty of accurate focusing and the image’s blur because of field curvature or less depth of field in the handy system for measuring the crack width in concrete structure which designed before based on the traditional optical imaging technology

a new system based on wave-front coding which can extend the depth of focus is designed. First

the normalized parameter of a cubic phase plate and the relationship between it and its corresponding real design parameters are discussed. Then a handy measuring system design based on wavefront coding with CODE V is completed. Finally

the cubic phase plate is made and a preliminary experiment is done. Experimental results indicate that the depth of field of the wavefront coding system based on a single lens can be extended to 15mm when resolving power is 50mm and F number is 6

which is 4.5 times of that in theory at the same F number. The system can satisfy the requirements of depth of field and imaging for measuring the width of cracks in concrete.