Average Co-Inventor Count = 3.16
ph-index = 3
The patent ph-index is calculated by counting the number of publications for which an author has been cited by other authors at least that same number of times.
Company Filing History:
1. Hitachi, Ltd. (3 from 42,517 patents)
3 patents:
1. 4810872 - Optical property measuring device
2. 4810089 - Photoelastic effect measuring device
3. 4304490 - Spectrophotometer