Test circuit for photographic cameras

Claim 2

In a camera adapted to expose film to scene illumination through an exposure aperture, exposure sensing apparatus for sensing scene illumination and for deTermining the condition of an energy source for said exposure sensing apparatus, said exposure sensing apparatus comprising: a. photosensitive means responsive to scene illumination for providing a signal indicative thereof; b. indicating means responsive to the signal for providing an indication that scene illumination is less than a predetermined value; and c. test means for measuring the condition of the energy source and for disabling said indicating means when the energy level of the source falls below a predetermined value.

Claim 3

In a camera adapted to expose film to scene illumination through an exposure aperture, exposure sensing apparatus for sensing scene illumination and for determining the condition of an energy source for said exposure sensing apparatus, said exposure sensing apparatus comprising: a. first test means responsive to scene illumination for providing a first signal indicating that scene illumination is below a predetermined level; b. second test means adapted to be coupled to the source for providing a second signal indicating that the energy level of the source is below a predetermined value; c. energizable means for providing a visual indication; and d. switch means operative in a first mode in response to the first signal for energizing said indicating means and in a second mode in response to the first and second signals for preventing the energization of said indicating means.

Claim 4

In a camera adapted to expose film to scene illumination through an exposure aperture, exposure sensing apparatus for sensing scene illumination and for determining the condition of an energy source for said exposure sensing apparatus, said exposure sensing apparatus comprising: a. first test means responsive to scene illumination for providing a first signal indicating that scene illumination is below a predetermined level; b. second test means adapted to be coupled to the source for providing a second signal indicating that the energy level of the source is below a predetermined value; c. energizable means for providing a visual indication; and d. switch means operative in a first mode in response to the first signal for energizing said indicating means and in a second mode in response to the first and second signals for preventing the energization of said indicating means.

Claim 5

In a camera adapted to expose film to scene illumination through an exposure aperture, exposure sensing apparatus for sensing scene illumination and for determining the condition of an energy source for said exposure sensing apparatus, said exposure sensing apparatus comprising: a. energizable means for providing a visual indication; b. switch means having an input terminal and having a threshold level above which said switch means is disposed in an operative mode for energizing said indicating means and below which said switch is disposed in an operative mode; c. first test means responsive to scene illumination for applying a first signal indicating that scene illumination is below a predetermined level to said input terminal; d. second test means adapted to be coupled to the energy source for providing a reference signal indicative of the potential level of the energy source; the reference signal being less than the threshold level of said switch means when the potential level of the energy source is less than an operative value; and e. means for maintaining the potential of said input terminal at a level not greater than that of the reference signal.

Claim 6

In a camera adapted to expose film to scene illumination through an exposure aperture, exposure sensing apparatus for sensing scene illumination and for determining the condition of an energy source for said exposure sensing apparatus, said exposure sensing apparatus comprising: a. energizable means for providing a visual indication; b. switch means having an input terminal and having a threshold level above which said switch means is disposed in an operative mode for energizing said indicating means and below which said switch is disposed in an operative mode; c. first test means responsive to scene illumination for applying a first signal indicating that scene illumination is below a predetermined level to said input terminal; d. second test means adapted to be coupled to the energy source for providing a reference signal indicative of the potential level of the energy source; the reference signal being less than the threshold level of said switch means when the potential level of the energy source is less than an operative value; and e. means for maintaining the potential of said input terminal at a level not greater than that of the reference signal.

Claim 7

In a camera having a light-integrating, timing circuit for determining the exposure interval in accordance with the intensity of scene illumination, apparatus for sensing scene illumination and for determining the condition of a potential source for the timing circuit, said apparatus comprising: a. photosensitive means responsive to scene illumination and having an impedance dependent upon the intensity of incident scene illumination; b. first switch means responsive to the impedance of said photosensitive means for providing a first signal indicative that the intensity of scene illumination is below a first value; c. energizable means for providing a visual indication; d. second switch means having an input terminal for receiving the first signal and having a threshold level above which said second switch means is disposed in an operative mode for energizing said indicating means and below which said second switch means is disposed in an inoperative mode; e. test means adapted to be coupled to the potential source for providing a reference signal indicative of the potential level of the potential source; the reference signal being less than the threshold level of said second switch means when the potential source is below an operative level sufficient to normally energize the timing circuit; and f. means for maintaining the potEntial of said input terminal at a level not greater than that of said reference signal so that when the potential of the potential source is not above its operative level, said indicating means may not be energized.

Claim 8

In a camera having a light-integrating, timing circuit for determining the exposure interval in accordance with the intensity of scene illumination, apparatus for sensing scene illumination and for determining the condition of a potential source for the timing circuit, said apparatus comprising: a. photosensitive means responsive to scene illumination and having an impedance dependent upon the intensity of incident scene illumination; b. first switch means responsive to the impedance of said photosensitive means for providing a first signal indicative that the intensity of scene illumination is below a first value; c. energizable means for providing a visual indication; d. second switch means having an input terminal for receiving the first signal and having a threshold level above which said second switch means is disposed in an operative mode for energizing said indicating means and below which said second switch means is disposed in an inoperative mode; e. test means adapted to be coupled to the potential source for providing a reference signal indicative of the potential level of the potential source; the reference signal being less than the threshold level of said second switch means when the potential source is below an operative level sufficient to normally energize the timing circuit; and f. means for maintaining the potEntial of said input terminal at a level not greater than that of said reference signal so that when the potential of the potential source is not above its operative level, said indicating means may not be energized.

Claim 9

Apparatus as claimed in claim 4, wherein there is included blocking means disposable from a first position to facilitate scene illumination being directed onto said photosensitive means, to a second position blocking the scene illumination from said photosensitive means.

Claim 10

Apparatus as claimed in claim 4, wherein said maintaining means comprises a unidirectional conducting device connected to said input terminal and to receive the reference signal.