Abstract

A chromatic confocal microscope (CCM) is a high-dynamic-range noncontact distance measurement sensor; it is based on a hyperchromatic lens. The vast majority of commercial CCMs use refractive-based chromatic dispersion to chromatically code the optical axis. This approach significantly limits the range of applications and performance of the CCM. In order to be a suitable alternative to a laser triangulation gauge and laser encoder, the performance of the CCM must be improved. In this paper, it is shown how hybrid aspheric diffractive (HAD) lenses can bring the CCM to its full potential by increasing the dynamic range by a factor of 2 and the resolution by a factor of 5 while passively athermizing and increasing the light throughput efficiency of the optical head [M. Rayer, U.S. patent 1122052.2 (2011)]. The only commercially suitable manufacturing process is single-point diamond turning. However, the optical power carried by the diffractive side of a hybrid aspheric diffractive lens is limited by the manufacturing process. A theoretical study of manufacturing losses has revealed that the HAD configuration with the highest diffraction efficiency is for a staircase diffractive surface (SDS). SDS lenses have the potential to reduce light losses associated with manufacturing limits by a factor of 5 without increasing surface roughness, allowing scalar diffraction-limited optical design with a diffractive element.

© 2014 Optical Society of America

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References

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2011

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

2008

B. H. Kleemann, M. Seesselberg, and J. Ruoff, “Design concepts for broadband high-efficiency DOEs,” J. Eur. Opt. Soc. 3, 08015 (2008).
[CrossRef]

1998

H. J. Jordan, M. Wegner, and H. Tiziani, “Highly accurate non-contact characterization of engineering surfaces using confocal microscopy,” Meas. Sci. Technol. 9, 1142–1151 (1998).
[CrossRef]

1997

1994

1993

1984

G. Molesini, G. Pedrini, P. Poggi, and F. Quercioli, “Focus-wavelength encoded optical profilometer,” Opt. Commun. 49, 229–233 (1984).
[CrossRef]

1871

W. Sellmeier, “Zur Erklrung der abnormen Farbenfolge im Spektrum einiger Substanzen,” Ann. Phys. 143, S272–S282 (1871).
[CrossRef]

Chipman, R. A.

Dobson, S. L.

Evans, C. J.

R. L. Rhorer and C. J. Evans, Handbook of Optics, 3rd ed. (McGraw-Hill, 1995), Chap. 41.

Fainman, Y.

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1968), p. 67.

Grann, E. B.

Hecht, E.

E. Hecht, Optics (Addison-Wesley, 2002), p. 158.

Hoenicka, R.

R. Hoenicka, S. Schmideder, and N. Reindl, “Temperature sensor,” U.S. patentUS20130128925 A1 (May23, 2013).

Jordan, H. J.

H. J. Jordan, M. Wegner, and H. Tiziani, “Highly accurate non-contact characterization of engineering surfaces using confocal microscopy,” Meas. Sci. Technol. 9, 1142–1151 (1998).
[CrossRef]

Kleemann, B. H.

B. H. Kleemann, M. Seesselberg, and J. Ruoff, “Design concepts for broadband high-efficiency DOEs,” J. Eur. Opt. Soc. 3, 08015 (2008).
[CrossRef]

Liu, H.

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

Lu, Z.

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

McCann, J. T.

M. J. Riedl and J. T. McCann, “Analysis and performance limits of diamond-turned diffractive lenses for the 3–5 and 8–12 micrometer regions,” in Infrared Optical Design and Fabrication, R. Hartmann, M. Marietta, and W. J. Smith, eds., Vol. CR38 of SPIE Critical Review Series (SPIE, 1991), pp. 153–163.

Michael Morris, G.

Moharam, M. G.

Molesini, G.

G. Molesini, G. Pedrini, P. Poggi, and F. Quercioli, “Focus-wavelength encoded optical profilometer,” Opt. Commun. 49, 229–233 (1984).
[CrossRef]

Pedrini, G.

G. Molesini, G. Pedrini, P. Poggi, and F. Quercioli, “Focus-wavelength encoded optical profilometer,” Opt. Commun. 49, 229–233 (1984).
[CrossRef]

Poggi, P.

G. Molesini, G. Pedrini, P. Poggi, and F. Quercioli, “Focus-wavelength encoded optical profilometer,” Opt. Commun. 49, 229–233 (1984).
[CrossRef]

Pommet, D. A.

Quercioli, F.

G. Molesini, G. Pedrini, P. Poggi, and F. Quercioli, “Focus-wavelength encoded optical profilometer,” Opt. Commun. 49, 229–233 (1984).
[CrossRef]

Rayer, M.

M. Rayer, “Metrological apparatus,” U.S. patent1122052.2 (December29, 2011).

Reindl, N.

R. Hoenicka, S. Schmideder, and N. Reindl, “Temperature sensor,” U.S. patentUS20130128925 A1 (May23, 2013).

Rhorer, R. L.

R. L. Rhorer and C. J. Evans, Handbook of Optics, 3rd ed. (McGraw-Hill, 1995), Chap. 41.

Riedl, M. J.

M. J. Riedl and J. T. McCann, “Analysis and performance limits of diamond-turned diffractive lenses for the 3–5 and 8–12 micrometer regions,” in Infrared Optical Design and Fabrication, R. Hartmann, M. Marietta, and W. J. Smith, eds., Vol. CR38 of SPIE Critical Review Series (SPIE, 1991), pp. 153–163.

Ruoff, J.

B. H. Kleemann, M. Seesselberg, and J. Ruoff, “Design concepts for broadband high-efficiency DOEs,” J. Eur. Opt. Soc. 3, 08015 (2008).
[CrossRef]

Sales, T. R. M.

Sasian, J. M.

Schmideder, S.

R. Hoenicka, S. Schmideder, and N. Reindl, “Temperature sensor,” U.S. patentUS20130128925 A1 (May23, 2013).

Seesselberg, M.

B. H. Kleemann, M. Seesselberg, and J. Ruoff, “Design concepts for broadband high-efficiency DOEs,” J. Eur. Opt. Soc. 3, 08015 (2008).
[CrossRef]

Sellmeier, W.

W. Sellmeier, “Zur Erklrung der abnormen Farbenfolge im Spektrum einiger Substanzen,” Ann. Phys. 143, S272–S282 (1871).
[CrossRef]

Sun, P.

Sun, Q.

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

Swanson, G. J.

G. J. Swanson, “Binary optics technology: the theory and design of multi-level phase diffractive optical elements,” (Massachusetts Institute of Technology, 1989).

Tiziani, H.

H. J. Jordan, M. Wegner, and H. Tiziani, “Highly accurate non-contact characterization of engineering surfaces using confocal microscopy,” Meas. Sci. Technol. 9, 1142–1151 (1998).
[CrossRef]

Wang, T.

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

Wegner, M.

H. J. Jordan, M. Wegner, and H. Tiziani, “Highly accurate non-contact characterization of engineering surfaces using confocal microscopy,” Meas. Sci. Technol. 9, 1142–1151 (1998).
[CrossRef]

Zhang, H.

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

Ann. Phys.

W. Sellmeier, “Zur Erklrung der abnormen Farbenfolge im Spektrum einiger Substanzen,” Ann. Phys. 143, S272–S282 (1871).
[CrossRef]

Appl. Opt.

J. Eur. Opt. Soc.

B. H. Kleemann, M. Seesselberg, and J. Ruoff, “Design concepts for broadband high-efficiency DOEs,” J. Eur. Opt. Soc. 3, 08015 (2008).
[CrossRef]

J. Opt.

T. Wang, H. Liu, H. Zhang, H. Zhang, Q. Sun, and Z. Lu, “Effect of incidence angles and manufacturing errors on the imaging performance of hybrid systems,” J. Opt. 13, 035711 (2011).
[CrossRef]

J. Opt. Soc. Am. A

Meas. Sci. Technol.

H. J. Jordan, M. Wegner, and H. Tiziani, “Highly accurate non-contact characterization of engineering surfaces using confocal microscopy,” Meas. Sci. Technol. 9, 1142–1151 (1998).
[CrossRef]

Opt. Commun.

G. Molesini, G. Pedrini, P. Poggi, and F. Quercioli, “Focus-wavelength encoded optical profilometer,” Opt. Commun. 49, 229–233 (1984).
[CrossRef]

Other

M. J. Riedl and J. T. McCann, “Analysis and performance limits of diamond-turned diffractive lenses for the 3–5 and 8–12 micrometer regions,” in Infrared Optical Design and Fabrication, R. Hartmann, M. Marietta, and W. J. Smith, eds., Vol. CR38 of SPIE Critical Review Series (SPIE, 1991), pp. 153–163.

R. L. Rhorer and C. J. Evans, Handbook of Optics, 3rd ed. (McGraw-Hill, 1995), Chap. 41.

G. J. Swanson, “Binary optics technology: the theory and design of multi-level phase diffractive optical elements,” (Massachusetts Institute of Technology, 1989).

R. Hoenicka, S. Schmideder, and N. Reindl, “Temperature sensor,” U.S. patentUS20130128925 A1 (May23, 2013).

M. Rayer, “Metrological apparatus,” U.S. patent1122052.2 (December29, 2011).

http://www.micro-epsilon.co.uk/download/products/cat--confocalDT--en.pdf .

E. Hecht, Optics (Addison-Wesley, 2002), p. 158.

http://www.zeonex.com/applications_optical.asp .

https://www.norlandprod.com/adhesives/NOA%2089.html .

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1968), p. 67.

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Figures (13)

Fig. 1.
Fig. 1.

Schematic description of the CCM. The light emitted by the white light source is axially spread due to the chromatic aberration of the optical head. Only the light focused onto the surface is coupled back to the spectrometer. The peak position gives a unique signature of the surface height.

Fig. 2.
Fig. 2.

Map of possible optical design using a refractive and HAD hyperchromatic lens of 8 mm diameter. The HAD approach allows designs that are not achievable using the refractive technology.

Fig. 3.
Fig. 3.

Dash line: diffraction efficiency of three consecutive modes of harmonic p = 6 . Plain line: chromatic confocal response. For one surface, three peaks are observed simultaneously; therefore, the measurement uncertainty is improved.

Fig. 4.
Fig. 4.

Dash line: diffraction efficiency of two consecutive modes of harmonic p = 1.5 . Plain line: chromatic confocal response. By spreading the energy between two modes, the range of measurement is extended by a factor 2.

Fig. 5.
Fig. 5.

Diffraction efficiency of the doublet E48R [13] plastic with the NOA89 glue [14]. Even with broadband illumination, the diffraction efficiency exceeds 98% over 400 nm of spectral bandwidth.

Fig. 6.
Fig. 6.

Diffraction efficiency of the E48R [13] plastic with air and with the NOA89 [14] glue. The couple E48R [13] and NOA98 [14] exhibits significantly higher diffraction efficiency than the couple 480R [13] and air.

Fig. 7.
Fig. 7.

Tool at the diffractive zone discontinuity. Shadow zone Λ represents the part of the diffractive profile that cannot be machined.

Fig. 8.
Fig. 8.

Profile of an SDS lens, which is simply consecutive steps of the height of the original diffractive profile. An SDS lens is powerless at the design wavelength.

Fig. 9.
Fig. 9.

Efficiency of HAD lens, SDS lens of optical power of 0.005 mm 1 , and a stack of seven broadband HAD lenses equivalent to optical power of 0.005 mm 1 . It appears that the SDS lenses offer the highest efficiency due to low scattering losses, low machine impulse response losses, and no shadow zone losses.

Fig. 10.
Fig. 10.

Diffractive profile of HAD lens measured using CCI white light interferometer. The shadow zone is 5 μm for a lens with a 21 μm ring size.

Fig. 11.
Fig. 11.

Diffractive profile of an SDS lens measured using a CCI white light interferometer. The shadow zone is 0.8 μm for a lens of 5 μm ring size.

Fig. 12.
Fig. 12.

Quadratic HAD lenses with a ring width of around 10 μm. Due to the fine structure of HAD lenses, diffractive ring intervals below 10 μm suffer from high form error.

Fig. 13.
Fig. 13.

CCM optical head generic architecture. Entrance pinhole is placed on the left-hand surface to measure on the right. In the case of HAD- and SDS-based CMM optical heads, the diffractive surface is placed at surface S3.

Tables (2)

Tables Icon

Table 1. Broadbanda and Thin HAD Comparison for Quadratic Diffractive Lens of Optical Power 0.005 mm 1

Tables Icon

Table 2. Experimental Relative Chromatic Confocal Peak Intensity of Three Comparable CCM Optical Heads Using Refractive, HAD, and SDS Hyperchromatic Lensesa

Equations (19)

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z ( r ) = z ref ( r ) + mod ( z dif ( r ) , δ z ) ,
1 F ref ( λ ) = ( n ( λ ) 1 ) ( 1 R 1 1 R 2 + ( n ( λ ) 1 ) d n ( λ ) R 1 R 2 ) ,
n ( λ ) = 1 + i = 1 k λ 2 B i λ 2 C i ,
F Diff = F 0 p λ D m λ ,
δ z = λ D n 1 ,
δ ϕ = δ z 2 π n λ D ,
η = sinc 2 ( p λ 0 λ n 1 ( λ ) n 2 ( λ ) n 1 ( λ 0 ) n 2 ( λ 0 ) m ) ,
p λ 0 λ n 1 ( λ ) n 2 ( λ ) n 1 ( λ 0 ) n 2 ( λ 0 ) = m .
Δ r = m p f λ 0 2 R .
η ring = 1 2 π r Λ 2 π r Δ r = 1 Λ Δ r ,
η ring = 1 n = 1 N 2 π r n r t sin ψ π R 2 ,
η lens = 1 2 α r t n 1 n 2 ( α R 2 λ D + 1 ) ,
η lens = 1 2 r t n 1 n 2 ( NA 2 λ D + α ) .
η lens = 1 2 R 2 a max ( δ x v r ) 2 n = 1 N r n .
η lens = 1 2 R 2 a max ( δ x v r ) 2 λ D α n = 1 N n ,
N = R 2 α λ d .
η ( r ) = sinc 2 ( λ PV ( r ) ( n 1 n 2 ) λ ) .
η = 2 R 2 0 R η ( r ) r d r .
z ( r ) = z ref ( r ) + mod ( z ref ( r ) , δ z ) .

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