Three-dimensional catadioptric vision sensor using
omnidirectional dot matrix projection
Fuqiang Zhou (周富强)
1,
*, Xin Chen (陈 昕)
1
, Haishu Tan (谭海曙)
2
,
and Xinghua Chai (柴兴华)
1
1
Key Laboratory of Precision Opto-mechatronics Technology, Ministry of Education,
Beihang University, Beijing 100191, China
2
Department of Electronic Information Engineering, Foshan University, Foshan 528000, China
*Corresponding author: zfq@buaa.edu.cn
Received July 1, 2016; accepted September 23, 2016; posted online November 10, 2016
In order to solve the problem of low measurement accuracy caused by uneven imaging resolutions, we develop a
three-dimensional catadioptric vision sensor using 20 to 100 lasers arranged in a circular array called omnidi-
rectional dot maxtric projection (ODMP). Based on the imaging characteristic of the sensor, the ODMP can
image the area with a high image resolution. The proposed sensor with ODMP can minimize the loss of the detail
information by adjusting the projection density. In evaluating the performance of the sensor, real experiments
show the designed sensor has high efficiency and high precision for the measurement of the inner surfaces of
pipelines.
OCIS codes: 140.3290, 140.3560, 150.0155, 280.3420.
doi: 10.3788/COL201614.111403.
In computer vision systems, omnidirectional three-
dimensional (3D) measurements are an attractive area that
can observe omnidirectional scenes simultaneously
[1,2]
. The
imaging model of catadioptric vision systems have been
studied in-depth in recent years. Geyer and Daniilidis
[3]
derived the geometric model of the catadioptric camera
system, which has been used by many research works in
the area of visual serving. Scaramuzza et al.
[4,5]
gave a
detail analysis of the catadioptric camera’s imaging
model with a conic reflector. Similarly, vision sensors
based on the catadioptric vision system also have
achieved remarkable results. Paniagua et al.
[6]
designed
a wearable catadioptric vision sensor with a low-cost
conic pattern laser in hand. Shin
[7]
proposed an omnidi-
rectional ranging system using a line structured light
image to obtain all directional distance information effec-
tively. Harmat
[8]
presented an omnidirectional structure
light sensor that could be applied to small, unmanned
aerial vehicles, which can operate in a number of differ-
ent environments. Zhang
[9]
used light rings with different
angular frequencies and intensities to build a catadioptric
vision system for robotic navigation. Catadioptric camera
systems based on structured light 3D vision measurements
have the widest applications
[10–13]
in practical inspections
due to their fast measuring speed, non-contact, low cost,
and robust nature in real measurements
[14–16]
. However,
although the working method and principle of the existing
catadioptric structured light vision sensors are similar, the
lasers used in the sensors are different, such as circular
structured light and line structured light
[17]
, whi ch may
cause the loss of detail information in a local, highly reflec-
tive pipeline. The measurement accuracy is influenced by
the uneven imaging resolution caused by the structure
characteristics of the reflector and the projection density
of the lasers.
To solve these problems, we present a 3D catadio ptric
vision sensor that can be applied to the measurement of
a long pipeline. The omnidirectional dot maxtric projection
(ODMP), which consists of 20 to 100 dot lasers and is posi-
tioned in 2 to 5 layers between the mirror and camera by
10° to 50°, can image a high imaging resolution area. The
density of the ODMP can be adjusted using the measure-
ment accuracy. In the following section, we describe how we
can realize the measurement model by using the ODMP.
To measure the detail information of the inner surface,
we first established the structure of the sensor. Figure
1
shows the optical path designation of the ODMP sensor.
The camera placed below the conic reflector and the cam-
era optical axis coincide with the symmetry axis of the
conic reflector in the vertical direction. As is shown in
Fig.
1, there are some identifiers that need introducing:
the entrance pupil of the lens is located at ξ unite above
the origin. h is the distance between the optical center
of the camera and the vertex of the conic reflector. The
working height of the ODMP is m. The working distance
of the novel sensor is set as the mi nimum distance from the
light spots in the omnidirectional image to the camera
optical axis, which is defined as l.
Fig. 1. Structure design of ODMP sensor.
COL 14(11), 111403(2016) CHINESE OPTICS LETTERS November 10, 2016
1671-7694/2016/111403(5) 111403-1 © 2016 Chinese Optics Letters