A digital electro-optical measuring micrometer, in which the measurement is precisely determined and initiates electrical pulses fed to a digital readout, said micrometer including:
- (a) a U-shaped housing transportable to a point of measurement and within which all mechanically movable elements used to derive the precise measurement are carried, said housing further including a fixedly supported anvil;
- (b) a movable anvil including a movable bracket slidably carried by and on a precision guide means supported by the housing and providing for movement toward and away from the fixedly supported anvil, said guide means disposed within the housing so that the movable anvil is precisely movable along a prescribed path and distance which is at least a standard unit of measurement;
- (c) a constant force spring attached at one end to the housing and at the other end to the movable bracket so as to urge the movable anvil from the maximum open condition and toward the fixedly supported anvil and with said constant force applied at all intermediate positions therealong;
- (d) a tape of relative thinness, this tape carried for movement within the housing by rollers carried by the fixed housing and with at least one end of the tape being secured to the movable member and moved with and by the movable anvil as it is moved, this movable tape being in a driving contact with a precision gage roller carried on a rotatable shaft and with this roller and shaft being rotated as the tape is moved thereover;
- means for maintaining the tape at a determined tension and for providing a corresponding rotational movement of the roller;
- (e) a rotary disc-like interrupter member carried by and on the shaft on which is mounted the precision gage roller, said interrupter member precisely rotated with the movement of the tape and in response to the movement of the movable anvil against and with the bias of the constant force spring, said interrupter member having a sequence of equally spaced radially disposed lines thereon and in which the tape is also carried in a guide path and maintained in a prescribed alignment by means of first and second idler rollers with one idler roller arranged on each side of the tape path to and from the precision gage roller to provide a wrap around this roller of at least one-quarter of the circumference of said precision gage roller;
- (f) an encoder including a directed light source and at least a pair of photosensors carried by and as a part of said encoder, each photosensor adapted to receive a narrow beam of light from said source with said beam and photosensors arranged so that the lines of the radial interrupter member interrupts the beam of light as the interrupter member is moved, said interruptions as read by the photosensor being converted to electrical pulse signals;
- (g) a dash pot having a piston connected to the movable anvil and movable in said dash pot, said piston movable by and with the movement of the movable anvil and having throttling means for establishing the maximum rotational speed of the interrupter member and the associated movable anvil in either of the two directions of movement to prevent bounce and to establish a sufficiently slow rate of the movement of the anvil whereat and whereby each and every interruption of the beam of light is distinctly read by the photosensors to insure that each and every line on the rotating interrupter member as it interrupts the beam of light converts said interruptions to an electrical pulse signal, said pair of photosensors being optically aligned so as to produce substantially simultaneously phase-shifted waves and pulses each time a line interruption occurs and to feed this information to a discriminator circuit which ascertains from this information the direction of travel at that instant of time, and (h) a digital counter and read-out adapted to receive said electrical signals and convert said pulse signals to information which is fed to converting apparatus with said information corresponding to the precise linear position of the movable member.