Photo lock system

• US 3,896,345 A
• Filed: 09/03/1974
• Issued: 07/22/1975
• Est. Priority Date: 09/03/1974
• Status: Expired due to Term

• Current Assignee: Henry R. Zink
• Original Assignee: Henry R. Zink
• Inventors: Zink, Henry R.
• Primary Examiner(s): Hix, L. T.
• Application Number:
  US05/502,851
• Time in Patent Office: 322 Days
• Field of Search: 317/134 250/555,556,557
• US Class Current: 361/172
• CPC Class Codes: E05B 49/006 actuating opto-electronic devices

Abstract

An access control system for actuating a latch or other device when the appropriate key member is inserted. A receptacle with photocells at first and second stations with a transparency at the first station. A film strip key member with a complementary transparency and an average transmission or gray scale on the remainder of the film matching that of the complementary transparency. Detector circuitry having the photocells connected in the input for actuating a latch or initiating an alarm as a function of the particular key member inserted.

Claims

1. In an access control system, the combination of:

a receptacle having a first station and a second station and including means defining a slot for receiving a key member for movement past said first station to said second station;

a first radiation sensor mounted at said first station;

a second radiation sensor mounted at said second station;

means for directing radiation across said slot to each of said sensors;

a first transparency mounted at said first station; and

a key member having a second transparency which is the complement of said first transparency, with said second transparency positioned on said key member to move past said second station to said first station as said key member is inserted into said slot, and with at least the portions of said key member which are at said second station during insertion having an average radiation transmission characteristic substantially the same as that of said second transparency.

2. A system as defined in claim 1 wherein said transparencies are a photographic positive and a photographic negative.

3. A system as defined in claim 2 wherein said key member is a strip of photographic film with said second transparency a part thereof.

4. A system as defined in claim 1 wherein said receptacle includes spaced plates providing said slot therebetween, each of said plates having an opening at said first station and at said second station for receiving said sensors and a radiation source.

5. A system as defined in claim 1 including:

a first detector having an input and an output; and

first circuit means connecting said first sensor to said first detector input, with said first detector providing an access signal at the output thereof when a complementary second transparency is opposite said first transparency blocking substantially all radiation to said first sensor.

6. A system as defined in claim 5 including:

a second detector having an input and an output;

second circuit means connecting said second sensor to said second detector input, with said second detector providing a blocking signal at the output thereof when a key member having an average radiation transmission characteristic substantially different from that of said first transparency is positioned at said second station; and

third circuit means connecting said blocking signal to said first detector for blocking any access signal output.

7. A system as defined in claim 6 with said second circuit means also connecting said second sensor to said first detector, with said second detector providing said blocking signal when said key member average transmission is less than that of said first transparency, and with the signal from said second sensor providing a blocking signal when said key member average transmission is greater than that of said first transparency.

8. A system as defined in claim 6 wherein each of said first and second circuit means includes a variable resistor in series with the sensor for connection across a voltage source, with the junction of the sensor and variable resistors connected to the detector input.

9. A system as defined in claim 5 including an access control device and means connecting said first detector output to said device in controlling relation for actuation of said device by an access signal.