## 5 Conclusions  
A Raman system with a 1064 nm excitation laser was coupled to a fiber probe, a digital microscope, and a motorized stage. The near-infrared excitation wavelength (\(\uplambda\)) enabled light penetration down to several hundred micrometers. The detection by a lens with NA 0.3 in combination with a 600 \(\upmu\)m fiber core gave poor confocality but offered extracting volumetric information from deeper tissue layers, which partly compensates for the lower scattering intensity of factor 0.3 due to the \(\uplambda^{-4}\) Rayleigh law. As a consequence of the focus diameter near 200 \(\upmu\)m, a high-precision motorized stage was not required, and an inexpensive model was selected instead with a large scan range of 200 \(\times\) 300 mm. Overall, such a compact and versatile Raman instrument shows great potential for applied sciences, in particular for samples with a high fluorescent background.  
The performance of the 1064 nm Raman instrument was demonstrated for non-tumor and tumor specimens of resected human bladders. Radical cystectomy is performed in patients with high-grade, muscle-invasive tumor diseases. Due to previous treatments such as endoscopic resection of non-muscle-invasive tumors and photodynamic therapy, necrosis is often present beside lipid-rich, control, and tumor tissue. Preprocessing of 1064 nm Raman images by baseline correction, smoothing, and normalization followed by processing with KMC and HCA revealed four clusters that were assigned to necrosis, lipid-rich, control, and tumor tissue. The findings agreed well with Raman images at 785 nm of these specimens. Deviations between 1064 nm and 785 nm Raman data sets might be due to different sample orientations. Proper correlation with the histopathological gold standard of parallel hematoxylin and eosin-stained tissue sections is also impaired by different orientations. Resected tissue can be stained by inks to label the orientation, e.g., to assess the tumor margin. However, these inks give intense Raman signals and/or high backgrounds that interfere with the spectral fingerprint of tissue. The 1064 nm option would be interesting for Raman imaging of intraoperative specimens with ink labels because inks do not contribute to 1064 nm excited Raman spectra. Another interesting urological application of a portable dispersive 1064 nm fiber probe Raman imaging spectrometer is the assessment of kidney stones whose Raman spectra are often affected by intense fluorescence at visible excitation wavelengths. It was shown that the identification of the stone type failed in two cases with the 785 nm Raman instrument and was successful in all cases with the 1064 nm instrument.  
Conceptualization, J.D.M.-B., T.A.S. and C.K.; methodology, J.D.M.-B. and T.A.S.; software, J.D.M.-B. and T.A.S.; investigation, J.D.M.-B.; resources, C.K., J.P. and A.M.; writing--original draft preparation, J.D.M.-B. and C.K.; writing--review and editing, all; supervision, C.K. and J.P.; funding acquisition, C.K. and A.M. All authors have read and agreed to the published version of the manuscript.  
This work has partially been funded by the German Federal Ministry of Education and Research (BMBF) under the project UroMDD (03 ZZ0444).  
The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Ethics Committee) of the University of Freiburg (protocol code 592/17 (191723) approved on 30 January 2020) for studies involving humans.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
Data Availability Statement: The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors thank [PERSON] (Faculty of Medicine, University Freiburg, Germany) for support in providing bladder specimens.  
The authors declare no conflicts of interest.