Abstract

The basic constraints on the working range of CCD-based bar code readers are analyzed. A comprehensive model that allows the calculation of the optimal working range and its corresponding optical system parameters is derived. Experimental results are found to be in good agreement with theoretical calculations. Finally, comparisons between bar code laser scanners and CCD readers are presented.

© 1993 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. W. S. Boyle, G. E. Smith, “Charge coupled semiconductor devices,” Bell Syst. Tech. J. 49, 587–593 (1970).
  2. S. B. Campana, “Techniques for evaluating charge-coupled imagers,” Opt. Eng. 16, 267–274 (1977).
  3. J. W. Coltman, “The specification of imaging properties by response to a sine wave input,” J. Opt. Soc. Am. 44, 468–471 (1954).
    [CrossRef]
  4. J. C. Feltz, “Development of the modulation transfer function and contrast transfer function for discrete systems, particularly charge-coupled devices,” Opt. Eng. 29, 893–904 (1990).
    [CrossRef]
  5. Electro-Optics Handbook (Radio Corporation of America, Lancaster, Pa., 1974), pp. 114–117 and 216.
  6. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 123–125.
  7. Data sheet of a Panasonic Model ZE-8300 CCD bar code reader.
  8. Data sheet of MSB Electronics Model LEMCO 71 CCD bar code reader.
  9. E. Barkan, J. Swartz, “System design considerations in bar-code laser scanning,” Opt. Eng. 23, 413–420 (1984).
  10. A. Yariv, Optical Electronics (Wiley, New York, 1975), pp. 67–69.
  11. Data sheet of Sharp Electronics Model GL5LR8 LED.

1990 (1)

J. C. Feltz, “Development of the modulation transfer function and contrast transfer function for discrete systems, particularly charge-coupled devices,” Opt. Eng. 29, 893–904 (1990).
[CrossRef]

1984 (1)

E. Barkan, J. Swartz, “System design considerations in bar-code laser scanning,” Opt. Eng. 23, 413–420 (1984).

1977 (1)

S. B. Campana, “Techniques for evaluating charge-coupled imagers,” Opt. Eng. 16, 267–274 (1977).

1970 (1)

W. S. Boyle, G. E. Smith, “Charge coupled semiconductor devices,” Bell Syst. Tech. J. 49, 587–593 (1970).

1954 (1)

Barkan, E.

E. Barkan, J. Swartz, “System design considerations in bar-code laser scanning,” Opt. Eng. 23, 413–420 (1984).

Boyle, W. S.

W. S. Boyle, G. E. Smith, “Charge coupled semiconductor devices,” Bell Syst. Tech. J. 49, 587–593 (1970).

Campana, S. B.

S. B. Campana, “Techniques for evaluating charge-coupled imagers,” Opt. Eng. 16, 267–274 (1977).

Coltman, J. W.

Feltz, J. C.

J. C. Feltz, “Development of the modulation transfer function and contrast transfer function for discrete systems, particularly charge-coupled devices,” Opt. Eng. 29, 893–904 (1990).
[CrossRef]

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 123–125.

Smith, G. E.

W. S. Boyle, G. E. Smith, “Charge coupled semiconductor devices,” Bell Syst. Tech. J. 49, 587–593 (1970).

Swartz, J.

E. Barkan, J. Swartz, “System design considerations in bar-code laser scanning,” Opt. Eng. 23, 413–420 (1984).

Yariv, A.

A. Yariv, Optical Electronics (Wiley, New York, 1975), pp. 67–69.

Bell Syst. Tech. J. (1)

W. S. Boyle, G. E. Smith, “Charge coupled semiconductor devices,” Bell Syst. Tech. J. 49, 587–593 (1970).

J. Opt. Soc. Am. (1)

Opt. Eng. (3)

J. C. Feltz, “Development of the modulation transfer function and contrast transfer function for discrete systems, particularly charge-coupled devices,” Opt. Eng. 29, 893–904 (1990).
[CrossRef]

S. B. Campana, “Techniques for evaluating charge-coupled imagers,” Opt. Eng. 16, 267–274 (1977).

E. Barkan, J. Swartz, “System design considerations in bar-code laser scanning,” Opt. Eng. 23, 413–420 (1984).

Other (6)

A. Yariv, Optical Electronics (Wiley, New York, 1975), pp. 67–69.

Data sheet of Sharp Electronics Model GL5LR8 LED.

Electro-Optics Handbook (Radio Corporation of America, Lancaster, Pa., 1974), pp. 114–117 and 216.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 123–125.

Data sheet of a Panasonic Model ZE-8300 CCD bar code reader.

Data sheet of MSB Electronics Model LEMCO 71 CCD bar code reader.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (9)

Fig. 1
Fig. 1

Block diagram of a CCD-based bar code reader.

Fig. 2
Fig. 2

Image contrast C versus ratio r. The ratio r is defined as w/(2mM), where m is the size of the bar code narrowest element, w is the width of the rectangular PSF (i.e., the geometrical PSF), and M is the optical lateral magnification for a given bar code position. The dashed curve incorporates the effects that are due to CCD pixel size.

Fig. 3
Fig. 3

Diagram of three imaging configurations: far-extreme (solid line) out-of-focus, in-focus (heavy solid line), and near-extreme (dashed lined) out-of-focus positions.

Fig. 4
Fig. 4

Linearization of the signal Vout versus exposure (ItTint) for a CCD sensor.

Fig. 5
Fig. 5

Schematic configuration of a CCD bar code reader system.

Fig. 6
Fig. 6

WR versus illumination factor α for various bar code densities when the limited number of pixels/module is set to (a) N = 2.5 and (b) N = 4.

Fig. 7
Fig. 7

WR versus bar code density m for various values of illumination factor a when the limited number of pixels/module is set to (a) N = 2.5 and (b) N = 4.

Fig. 8
Fig. 8

Comparison of WR between bar code laser scanners and CCD noncontact readers in which laser scanners are optimized for a bar code density of 10 and 7.5 mil, respectively, and the CCD reader is optimized for a bar code density of 10 mil.

Fig. 9
Fig. 9

Illumination intensity of a Sharp LED GL5LR8 linear array (n = 15) along the separation d away from the array (solid curve) and an empirical approximation I = 132/d5/3 (dashed curve). The geometrical distribution of LED's is shown in the inset.

Tables (3)

Tables Icon

Table 1 CTF (m′) of CCD Pixels a

Tables Icon

Table 2 Optimal WRthr and Their Corresponding System Parameters for Various Bar code Densities a

Tables Icon

Table 3 WR Versus Bar code Densities for a Modified CCD-Based Bar code Reader Optimized for a Bar code Density of 10 mil a

Equations (37)

Equations on this page are rendered with MathJax. Learn more.

I out = I in ( x , y ) | h ( x , y ) | 2 ,
C ( m ) = { 1 0 r ½ ( 1 ) j r j r ( j 1 2 ) r ( j + 1 2 ) . with j = 1 , 2 , 3 ,
X 1 = ( D 2 m r ) a D ,
X 2 = ( D + 2 m r ) a D .
WR = X 2 X 1 = 4 mra D .
I t = k / d p ( fc ) , d d min ,
I s = I t h eff [ D 2 ( 1 f 1 a ) ] 2 = I t h eff ( D 2 b ) 2 ,
V out = I s T int γ ( V ) ,
V s = I s T int γ C ( m ) .
SNR = 20 log [ I s T int γ C ( m ) V n ] ( dB ) .
( I s ) min = V n T int γ C ( m ) 10 σ / 20 .
N = m M min L β ,
a = WR 2 + X 0 .
( I s ) min = k h eff ( X L + WR ) p [ D 2 ( 1 f 1 a ) ] 2 .
D = 4 m r max X 0 + WR 2 WR ,
V n T int γ C ( m ) 10 σ / 20 = k h eff ( X L + WR ) p × [ D 2 ( 1 f 1 X 0 + WR 2 ) ] 2 .
N = m L β ( X 0 + WR 2 ) f ( X 0 + WR ) ( X 0 + WR 2 f ) ,
α ( X L + WR ) p / 2 ( WR X 0 + WR X 0 + WR 2 ) = m 2 N ,
α = ( V n 10 σ / 20 T int k h eff γ C min ) 1 / 2 L β 2 r max .
D eff = 4 2 π m [ ln ( 1 C min ) ] 1 / 2 ,
WR = 2 Z 0 = 2 π W 0 2 λ = 8 m 2 [ ln ( 1 C min ) ] π λ .
2 W 0 W 1 = m 0 m 1 .
Z 1 2 = Z 0 2 [ ( W 1 W 0 ) 2 1 ] ,
WR 1 = { Z 1 + Z 2 = WR 0 2 { 1 + [ 2 ( m 1 m 0 ) 2 1 ] 1 / 2 } when m 1 > m 0 2 Z 1 = WR 0 [ 2 ( m 1 m 0 ) 2 1 ] 1 / 2 when m 0 2 < m 1 < m 0 , 0 when m 1 < m 0 2
F θ = J θ 1 d Ω ( lm ) ,
d Ω = d s cos θ ( d / cos θ ) 2 = d s cos 3 θ d 2 ( sr ) ,
I ( S 1 ) = F θ d s = J θ 1 cos 3 θ d 2 = cos 3 [ tan 1 ( S 2 S 1 d ) ] d 2 ( fc ) .
I ( S 1 , d ) = i = 1 n { J θ i cos 3 [ tan 1 ( S 2 i S 0 d ) ] d 2 } ( fc ) .
J θ = { 0.2 [ cos ( 3.6 θ ) ] 1.2 ( cd ) 0 < θ < 25 ° 0 otherwise .
I ( d ) = k d p ( fc ) , d > d min ,
P N = m b L β N .
C ( m ) = 1 r 1 ,
1 r = 2 m a D ( P σ a ) ,
I s = k h eff ( P σ X 0 + X L ) p [ D 2 ( 1 f 1 a ) ] 2 ,
1 ( P σ X 0 + X L ) p ( D 2 b ) 2 ( 2 m a D ( P σ a ) 1 ) = η ,
η V n 10 σ / 20 T int γ k h eff .
WR ( m ) = min ( P N , X 2 , P σ ) max ( X 1 , X 0 ) ,

Metrics