The effective classification methods of the small target objects in the no-fly zone are of great significance to ensure safety in the no-fly zone. But, due to the differences of the color and texture for the small target objects in the sky, this may be unobvious, such as the birds, unmanned aerial vehicles (UAVs), and kites. In this paper, we introduced the higher layer visualizing feature extraction method based on the hybrid deep network model to obtain the higher layer feature through combining the Sparse Autoencoder (SAE) model, the Convolutional Neural Network (CNN) model, and the regression classifier model to classify the different types of the target object images. In addition, because the sample numbers of the small sample target objects in the sky may be not sufficient, we cannot obtain much more local features directly to realize the classification of the target objects based on the higher layer visualizing feature extraction; we introduced the transfer learning in the SAE model to gain the cross-domain higher layer local visualizing features and sent the cross-domain higher layer local visualizing features and the images of the target-domain small sample object images into the CNN model, to acquire the global visualizing features of the target objects. Experimental results have shown that the higher layer visualizing feature extraction and the transfer learning deep networks are effective for the classification of small sample target objects in the sky.

Conventional 2-D discrete cosine transform (DCT) and 2-D discrete wavelet transform (DWT) have not been taken image orientation information into account. At the same time, to remove the speckle noise in ultrasound image is also a hard nut to crack. Based on above two issues, aiming at the sectorial ultrasound image, the paper proposes directional DCT-DWT hybrid transform. The proposed rays' or arts' DCT and DWT can be adopted for an image after the coordinate transform for the pixels of the image. Since the radiate wave directions are considered, the algorithm based proposed 2-D hybrid transform can inhibit the speckle noise of the ultrasound images. The experiment result verifies the proposed algorithm to be valid.

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