Modification of the inception v3 model for image classification with keras to work with grayscale images. You can also provide custom number of output classes (10 in this case).
inception = InceptionV3(weights='imagenet', include_top = True)
input_tensor = Input(shape=(img_height,img_width,1))
x = Conv2D(3,(3,3),padding='same')(input_tensor) # x has a dimension of (img_height,img_width,3)
out1 = inception(x)
out = Dense(10, activation = 'softmax')(out1)
model = Model(inputs = input_tensor, outputs = out)