A visual acuity device measures the visual acuity of a patient's eye by directing a pulsating beam of light on the eye and detecting the resulting reflection. A primary pattern having a pattern formed by transparent and non-transparent portions is positioned in the optical path of the pulsating beam of light. A fixed pair of analyzer or secondary pattern is positioned in the optical path of the beam of light reflected from the patient'eye. One of these analyzer or secondary patterns has a pattern which substantially corresponds to the pattern of the primary fixation pattern and the other has a pattern which is the negative mirror image of the pattern of the first analyzer or secondary pattern. The beam of light reflected from the patient's eye is divided by a beam splitter so that each of the analyzer patterns receives the reflected image of the primary pattern from the patient's eye. A photoelectric device is associated with each of the analyzer patterns for detecting the reflected beam of light passing through each of these analyzer patterns to generate an electrical output signal. The photoelectric devices are connected to a difference amplifier for eliminating any glare and generating a signal which is determinative of the visual acuity of the patient's eye. Far visual acuity can be measured by using infrared light adding a collimating and compensating lens. Thus, the visual acuity device objectively measures both far and near visual acuity.
A sensor for mixing ratio of liquid fuel comprising: a cylindrical enclosure having both inlet and outlet opening to act as a passage through which a mixing liquid fuel flows; a transparent column concentrically disposed into the enclosure to make outer surface contact with the liquid fuel; light emitting diode and photo diode each provided so as to sandwich the column in the lengthwise direction, so that the light emitted from the former enters the column through its one end and reflects at the boundary of the column and the liquid fuel, and go out of the other end thereof to fall on the latter; a temperature compensation photo diode disposed in the enclosure with the light of the light emitting diode partly as a light source to rectify the characteristics influenced under the ambient temperature variation; a voltage control circuit provided to control the voltage across the light emitting diode so as to maintain uniform output from the temperature compensation photo diode.
A blood flow measuring apparatus includes a system control unit that sends outputs for controlling the start and end of the measurement to optimum gain calculation units, which calculate the optimum gains of photomultipliers for receiving the light reflected from the eye fundus and the system control unit controls whether the optimum gains are outputted or not. Also, the optimum gain calculation unit respectively supply the system control units with outputs for monitoring whether the setting of the optimum gain has been completed or not, whereby the system control unit discriminates whether the photomultipliers have been set at the optimum gains.
A blood flow measuring apparatus includes a system control unit that sends outputs for controlling the start and end of the measurement to optimum gain calculation units, which calculate the optimum gains of photomultipliers for receiving the light reflected from the eye fundus and the system control unit controls whether the optimum gains are outputted or not. Also, the optimum gain calculation units respectively supply the system control unit with outputs for monitoring whether the setting of the optimum gain has been completed or not, whereby the system control unit discriminates whether the photomultipliers have been set at the optimum gains.
Methods, devices, and systems for predicting an optical acuity measure of an optical system of an eye. An optical acuity measure can be predicted by determining a point spread function based on a wavefront measurement of an eye, convolving a resolution target with the point spread function to produce an image, and predicting the optical acuity measure of the optical system of the eye based on the image.
