By "contact," I assume that you mean a system similar to that described by Gamon and Surfus (New Phytol. 143: 105-117 (1999)), which means "near contact." There are many indices. Many of these have been developed for use at the canopy level, so that they include the effect of the degree of light interception by the set of leaves. They are not useful for leaf-level studies (e.g., the normalized difference vegetation index). Among the indices that have been developed are:

PRI = Photochemcial Reflectance Index and is a measure of xanthophyll activity (photosynthetic radiation-use efficiency increases with increasing PRI values); a reduction in PRI (as we formulated it) indicates an increased level of zeaxanthin and a reduced PSII light use efficiency: (R531 – R570) / (R531 + R570) (Gamon, (Peñuelas and Filella, 1998). See a reanalysis by Sims and Gamon (Remote Sens. Environ. 81:337-354 (2002)).

The red edge of absorbance, as a first derivative at 703 nm (assuming that you're using a hyperspectral sensor with many narrow wavebands). This measures chlorophyll content. Developed by Filella and Penuelas (Int. J. Remote Sens. 15:1459-1470 (1994)).

SIPI = "structure insensitive pigment index" or structural independent index and is basically a measure of carotenoids/chlorophyll a: (R800 – R445) / (R800 – R680). See Penuelas et al. 1995. Photosynthetica 31:221-230.

(Review of pigment indices: Blackburn. 1998. Remote Sens. Environ. 66: 273-285)

NDPI (or NPCI) = is a normalized total pigment to chlorophyll a index and has been found to be well correlated with chlorophyll content, carotenoids/chlorophyll a, lutein and neoxanthin/chlorophyll a; e.g., a rough estimate of the ratio of total pigments to chlorophylla, decreasing in healthy plants and increasing in stressed or senescing plants. (R680 – R430) / (R680 + R430)

WBI = Water Band Index and is related to the amount of plant water: (R900 / R970) (Gamon). See Claudio et al. 2006. Remote Sens. Environ.103:304-311.

I'm sure there may be more that have some specialized use.

Red/far red ratio; reflectance, transmittance, absorbsorptance = 1 - reflectance-transmittance, these can be done with all spectrum that are measurable......this is just thie beginning, particularly if you have a radiometer or other good equipment.

The red:far red ratio is only useful at the canopy level. It's a measure of the degree of light interception at a given level in the canopy, and it comprises a signal for plant development, esp. stem elongation

What I mean with "contact measurement' is like in pictures below

Or..

Any one know other paper the evaluate leaf water content , with this technique?

You are using what is called a leaf clip. I assume you are using a hyperspectral sensor like the Ocean Optics USB2000 or USB4000. Possibly the ASD Field Spec. What are you trying to measure? There are already published algorithms for estimating leaf chlorophyll concentration from leaf reflectance measurements:

http://calmit.unl.edu/people/agitelson2/pdf/2008/AJEV_59_3_299-305.pdf

http://calmit.unl.edu/people/agitelson2/pdf/06_JPP-2003.pdf

http://calmit.unl.edu/people/agitelson2/pdf/2009/2009-JPP.pdf

There are also methods for estimating carotenoids:

http://calmit.unl.edu/people/agitelson2/pdf/63_2ndAgr&Forestry-Florida-2K.pdf

For estimating water content:

http://calmit.unl.edu/people/agitelson2/pdf/2009/2009-GRL-water%20content.pdf

Many canopy level vegetation indices are also valid for leaf level measurements, but as Vincent mention already, some are less effective because there is less scattering in the NIR for leaf level measurements. I suggest finding papers regarding the metrics you wish to measure and see which VIs work best. Regardless you should always include NDVI, Simple Ratio, and EVI (or EVI2) since these are frequently published. I strongly suggest using Chlorophyll Index Red Edge (CIred edge) or another red edge band for many chlorophyll related metrics (e.g. green leaf area index).

A good place to start would be my adviser's webpage. He is an expert in this type of remote sensing and he has amassed a large set of publications of which many are freely available. Those that are not, I probably have access to and can send you if you message me. The citations in these papers will lead you to other groups' works as well.

http://calmit.unl.edu/people/agitelson2/