Abstract

A random method is presented to measure the modulation transfer function (MTF) of the rigid endoscope, evaluating its imaging quality. The experimental setup includes a four-dimensional (4D) mobile platform, a non-full-screen liquid-crystal display (LCD), three different kinds of patterns, a nasoendoscope of 0° direction of view under measurement, a complementary metal oxide semiconductor (CMOS) device, and a computer. The method is divided into three steps to complete the MTF measurement. First the geometric distortion is evaluated to determine the suitable sampling matrix (SSM) by the grid pattern. Then the illuminance inhomogeneity distribution is evaluated to obtain the illuminance compensation curve by the uniform grayscale pattern. Finally the MTFs are acquired by analyzing the spatial frequency contents of the compensated SSMs by the random patterns. By analysis and comparison, the method can improve the stability and accuracy for the MTF measurement in a simplified way.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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References

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  1. R. Prescott, “Model for the assessment of image quality in endoscopes,” in 25th Annual Technical Symposium (International Society for Optics and Photonics), 53–57, (1981).
  2. Medical endoscopes-rigid endoscope, Part 1: Optical properties and test methods, Chinese National Standard, YY 0068.1, (2008).
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    [Crossref]
  4. JBT 9328-1999 Resolving power test target.
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    [Crossref]
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    [Crossref]
  7. F. A. Navas-Moya, “Measurement of the Optical Transfer Function Using A White-Dot Pattern Presented on A Liquid-crystal Display,” J. Eur. Opt. Soc. Rapid Publ. 8(1), 13029–13037 (2013).
    [Crossref]
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  10. Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
    [Crossref]

2014 (1)

2013 (2)

F. A. Navas-Moya, “Measurement of the Optical Transfer Function Using A White-Dot Pattern Presented on A Liquid-crystal Display,” J. Eur. Opt. Soc. Rapid Publ. 8(1), 13029–13037 (2013).
[Crossref]

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

2010 (1)

A. Fernandez-Oliveras, A. M. Pozo, and M. Rubino, “Comparison of Spectacle-lens Optical Quality by Modulation Transfer Function Measurements Based on Random-dot Patterns,” Opt. Eng. 49(8), 083603 (2010).
[Crossref]

2004 (1)

1999 (1)

1954 (1)

Backman, S. M.

Cheng, D.

Cheng, W.

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

Coltman, J. W.

Desai, V. N.

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

Fernandez-Oliveras, A.

A. Fernandez-Oliveras, A. M. Pozo, and M. Rubino, “Comparison of Spectacle-lens Optical Quality by Modulation Transfer Function Measurements Based on Random-dot Patterns,” Opt. Eng. 49(8), 083603 (2010).
[Crossref]

Kolehmainen, T. T.

Levy, E.

Lipson, S. G.

Liu, X.

Makynen, A. J.

Navas-Moya, F. A.

F. A. Navas-Moya, “Measurement of the Optical Transfer Function Using A White-Dot Pattern Presented on A Liquid-crystal Display,” J. Eur. Opt. Soc. Rapid Publ. 8(1), 13029–13037 (2013).
[Crossref]

Ngo, Y. Z.

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

Ojala, K. M.

Opher-Lipson, M.

Peles, D.

Pfefer, J.

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

Pozo, A. M.

A. Fernandez-Oliveras, A. M. Pozo, and M. Rubino, “Comparison of Spectacle-lens Optical Quality by Modulation Transfer Function Measurements Based on Random-dot Patterns,” Opt. Eng. 49(8), 083603 (2010).
[Crossref]

Prescott, R.

R. Prescott, “Model for the assessment of image quality in endoscopes,” in 25th Annual Technical Symposium (International Society for Optics and Photonics), 53–57, (1981).

Rubino, M.

A. Fernandez-Oliveras, A. M. Pozo, and M. Rubino, “Comparison of Spectacle-lens Optical Quality by Modulation Transfer Function Measurements Based on Random-dot Patterns,” Opt. Eng. 49(8), 083603 (2010).
[Crossref]

Wang, Q.

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

Wang, Y.

Yu, L.

Appl. Opt. (1)

Biomed. Opt. Express (1)

J. Eur. Opt. Soc. Rapid Publ. (1)

F. A. Navas-Moya, “Measurement of the Optical Transfer Function Using A White-Dot Pattern Presented on A Liquid-crystal Display,” J. Eur. Opt. Soc. Rapid Publ. 8(1), 13029–13037 (2013).
[Crossref]

J. Opt. Soc. Am. (1)

Opt. Eng. (1)

A. Fernandez-Oliveras, A. M. Pozo, and M. Rubino, “Comparison of Spectacle-lens Optical Quality by Modulation Transfer Function Measurements Based on Random-dot Patterns,” Opt. Eng. 49(8), 083603 (2010).
[Crossref]

Opt. Express (1)

Proc. SPIE (1)

Q. Wang, V. N. Desai, Y. Z. Ngo, W. Cheng, and J. Pfefer, “Towards Standardized Assessment of Endoscope Optical Performance:Geometric Distortion,” Proc. SPIE 9042, 904205 (2013).
[Crossref]

Other (3)

R. Prescott, “Model for the assessment of image quality in endoscopes,” in 25th Annual Technical Symposium (International Society for Optics and Photonics), 53–57, (1981).

Medical endoscopes-rigid endoscope, Part 1: Optical properties and test methods, Chinese National Standard, YY 0068.1, (2008).

JBT 9328-1999 Resolving power test target.

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Figures (8)

Fig. 1.
Fig. 1. Simplified resolution test board.
Fig. 2.
Fig. 2. The experimental setup.
Fig. 3.
Fig. 3. The grid pattern and its image: (a) grid pattern and (b) distorted grid image.
Fig. 4.
Fig. 4. Distortion of nasoendoscope: (a) F(r) curve, (b) Δ(r) curve and (c) M(r) curve.
Fig. 5.
Fig. 5. Illuminance distribution of output image: (a) NDR, SSM of the image and (b) 3D illuminance distribution for NDR.
Fig. 6.
Fig. 6. The random pattern and its image: (a) random pattern and (b) random image.
Fig. 7.
Fig. 7. MTF measurement results (d = 20 mm): (a) horizontal MTF comparison with different SSM sizes, (b) horizontal MTF comparison before and after illuminance compensation and (c) comparison with simplified resolution test board.
Fig. 8.
Fig. 8. MTF measurement results (d = 25 mm).

Equations (9)

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r ( λ , d ) = D 1.22 λ d ( c y c l e s / m m )
C T F ( υ ) = [ I max I min I max + I min ] o u t p u t [ I max I min I max + I min ] i n p u t
M T F ( υ ) = π 4 [ C T F ( υ ) + C T F ( 3 υ ) 3 C T F ( 5 υ ) 5 + C T F ( 7 υ ) 7 + C T F ( 11 υ ) 11 C T F ( 13 υ ) 13 C T F ( 15 υ ) 15 C T F ( 17 υ ) 17 + C T F ( 19 υ ) 19 ]
M T F ( υ ) π 4 C T F ( υ )
P S D ( υ x ) o u t p u t = 1 M i = 1 M | F F T { S S M ( 1 : N , i ) } | 2
M T F ( υ x ) = P S D ( υ x ) o u t p u t P S D ( υ x ) i n = 1 M i = 1 M | F F T { S S M ( 1 : N , i ) } | 2 o u t p u t 1 M i = 1 M | F F T { S S M ( 1 : N , i ) } | 2 i n
P S D ( υ x ) i n = c o n s t
M T F ( υ x ) = P S D ( υ x ) o u t p u t = 1 M i = 1 M | F F T { S S M ( 1 : N , i ) } | 2 o u t p u t
M T F ( υ y ) = P S D ( υ y ) o u t p u t = 1 N j = 1 N | F F T { S S M ( j , 1 : M ) } | 2 o u t p u t

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