颜真卿——多宝塔碑.doc

Colour Vision
Sensitivity & Acuity
Colour Vision
Trichromatic theory of colour vision
There is only one type of rod and this responds strongly to bluish-green light
Cones are divided into three categories, each of which has a different sensitivity to light
There are red light receptors, green light receptors and blue light receptors.
These cone sensitivities support the trichromatic theory as all colours of the visible spectrum can be seen by mixing the 3 primary colours (red, blue and green)
White objects reflect all colours to eye, black absorbs all colours so no light to the eye.
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Wavelengths of light absorbed by different cones
Colour Blindness
If you have normal vision you will see a figure seven in reddish brown dots.
People with red-green colour blindness will not see the 7, why?
These people lack red sensitive cones, but the green stimulated cones are stimulated by the red light, so all dots appear green
Sensitivity and Acuity
Rods and cones synapse with bipolar cells
Bipolar cells synapse with ganglion cells
Ganglion cells synapse with neurone fibres
At the fovea each cone synapses individually with a ganglion cell
This gives good Acuity (resolution). Bright light needed
Many Rods synapse with one bipolar neurone – RETINAL CONVERGENCE
Dim light results in small amount of neurotransmitter release
Individually, this would be insufficient to e the threshold of the bipolar cell, but the total amount of transmitter from several rods is
This gives less acuity but better sensitivity