You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither SPIE nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the SPIE website.
5 March 2014Implantable CMOS imaging device with absorption filters for green fluorescence imaging
Green fluorescent materials such as Green Fluorescence Protein (GFP) and fluorescein are often used for observing
neural activities. Thus, it is important to observe the fluorescence in a freely moving state in order to understand neural
activities corresponding to behaviors. In this work, we developed an implantable CMOS imaging device for in-vivo
green fluorescence imaging with efficient excitation light rejection using a combination of absorption filters. An
interference filter is usually used for a fluorescence microscope in order to achieve high fluorescence imaging sensitivity.
However, in the case of the implantable device, interference filters are not suitable because their transmission spectra
depend on incident angle. To solve this problem we used two kinds of absorption filters that do not have angle
dependence. An absorption filter consisting of yellow dye (VARYFAST YELLOW 3150) was coated on the pixel array
of an image sensor. The rejection ratio of ideal excitation light (490 nm) against green fluorescence (510 nm) was
99.66%. However, the blue LED as an excitation light source has a broad emission spectrum and its intensity at 510 nm
is 2.2 x 10-2 times the emission peak intensity. By coating LEDs with the emission absorption filters, the intensity of the
unwanted component of the excitation light was reduced to 1.4 x 10-4. Using the combination of absorption filters, we achieved excitation light transmittance of 10-5 onto the image sensor. It is expected that high-sensitivity green
fluorescence imaging of neural activities in a freely moving mouse will be possible by using this technology.